While there seems to be a lot of talk lately of fixing the P1093 issue some of the ideas being floated around are pretty far out there. If you attempt these repairs all I can say is buyer beware! People are talking about blocking the SAFETY PRESSURE VALVE and Shimming the Safety Pressure Valve. I am sorry but neither of these are a fix let alone safe. The purpose of the valve is much the same as a safety valve on you hot water heater at home. It is designed to open ONLY when there is a problem and not until then. There have been reports of GM having some bad valves and by all means those valves should be replaced, but block or shimming a valve set to open at 28,000 psi is just down right stupid! Think about what it takes to cut steel in half as that is just what your playing with. Look at the size they have made these parts to hold this level of pressure and think about it.
Yes, there is a problem when increasing the performance above stock that needs to be solved but blocking or shimming the safety valve is not a fix..... it is down right dangerous.

Steve who would try something like that?

Any info/updates on when the LLY extreme is available and will your programming help on the PITA p1093 codes.

Steve, have you seen 28k on a TechII yet? Do you think it would be safe to put a 28k relief on the rail?

Probably putting a lift pump on a system that was engineered for suction only could cause a serious engine fire. Don't think too many people are worried about that either.

In 3 months the LLY will be "orphaned" as the software guys move to the 06 computer.

Will the software guys remove the spike before then? That would be great. But in real life, we probably won't see it.

Steve, have you seen 28k on a TechII yet? Do you think it would be safe to put a 28k relief on the rail?

Probably putting a lift pump on a system that was engineered for suction only could cause a serious engine fire. Don't think too many people are worried about that either.

28,000 is where the stock relief valve is set, that's 5,000 over the stock max setting of 23,000 in the fuel rail. If your hoping to see everything that is going on with a Tech II you are mistaken as the data update rate is to slow. It will only update one PID every 250 ms ..................way too slow.

You are completely wrong in your 2nd statement. The system design was not for suction only, I think you need to go get a few books on the common rail design from Bosch. The only components that are marginal are the EDU and the fuel filter assemble and they will both be fine up to 12 psi! Those tests have already been done and confirmed the limits on the filter assemble with the manufacture!

Sorry, but, every system component will hold 10-12 psi all day long.
Screwing around at 28,000 you can cut steel in half and have a much higher chance of a fire as the high pressure atomizes the fuel much better.

Tim

We are working on resolving the issue as we feel it's in software control with the greater fuel delivery that's the cause of the problem. I do not know that we can solve it for sure but were giving it one Hell of a try. Making power is easy and that's been done for a long time. We have already been down the track quite a few times and know what it does. I am just not ready to release a product with a known problem like some others do.

28,000 is where the stock relief valve is set, that's 5,000 over the stock max setting of 23,000 in the fuel rail. If your hoping to see everything that is going on with a Tech II you are mistaken as the data update rate is to slow. It will only update one PID every 250 ms ..................way too slow.

You are completely wrong in your 2nd statement. The system design was not for suction only, I think you need to go get a few books on the common rail design from Bosch. The only components that are marginal are the EDU and the fuel filter assemble and they will both be fine up to 12 psi! Those tests have already been done and confirmed the limits on the filter assemble with the manufacture!

Sorry, but, every system component will hold 10-12 psi all day long.
Screwing around at 28,000 you can cut steel in half and have a much higher chance of a fire as the high pressure atomizes the fuel much better.

Did Bosch design the fuel storage, delivery, and return systems? Did GM design the delivery for pressure?

For that matter did they design the engine for 550HP?

Yes, there might be a better fix for the spike.

Interesting that some have resolved it who have run "spikey" tunes, and actually post that the tune doesn't 1093. Heck, some people even sell a fuel pressure box!

It appears a solution has been available to a select few. Well after a bit more testing, there will be one available to all.

It will amount to this: You want more than 350rwhp on your LLY? You will need:

Tuner
Exhaust
Trans
Gauges
Pressure shim

A pressure box will lie to the computer and increase rail pressure right up to the point that the pressure relief valve blows off.

Why go so far with a pressure box? Ramp up the fuel pressure to the full 23055psi via the tech 2 and see if the relief valve does it's job or not.

PS- nevermind....relief valve won't pop because it hasn't reached 28000psi

Did Bosch design the fuel storage, delivery, and return systems? Did GM design the delivery for pressure?

What does fuel storage have to do with anything? Bosch did design the fuel delivery system and return system and yes, the supply side was designed for pressure from a lift pump! Racor designed the Fuel Filter assemble. Racor says it's good for < 15 psi! All GM did was route the stainless steel lines from the engine to the tank. Do you really think the fuel lines that run from the tank to the engine and back will not hold 10 -12 psi? Like I said before screwing around with a sealed 28,000 psi regulator is not something that should be done. If you feel it's OK just because someone else is doing it be my guest, I'm just pointing out its not safe nor is it the right thing to do! I would never do it to my truck let alone anyone else's. There is also some people putting a dime under the regulator and blocking the whole thing off might as well just do that too. I just think it's much better to fix the cause of the problem but that only my opinion.
Also we have been long past 350 RwHp, much closer to 450 RwHp without blocking or modifying the regulator, so yes it can be done properly. It just takes time to do it right and get the necessary field testing done.

Why go so far with a pressure box? Ramp up the fuel pressure to the full 23055psi via the tech 2 and see if the relief valve does it's job or not.

The update rate of the data coming to the Tech II is too slow to see what is going on. There are pressure waves traveling inside the fuel rail and the Tech II will never show them. These pressure waves are from injectors opening and closing and the charging of the system from the high pressure pump. If you disrupt the system such that you increase the pressure waves to the point of opening the safety pressure blow off you have done it wrong, plain and simple! So to just try to raise the pressure regulator to cover up what you've screwed up is BS.

The update rate of the data coming to the Tech II is too slow to see what is going on. There are pressure waves traveling inside the fuel rail and the Tech II will never show them. These pressure waves are from injectors opening and closing and the charging of the system from the high pressure pump. If you disrupt the system such that you increase the pressure waves to the point of opening the safety pressure blow off you have done it wrong, plain and simple! So to just try to raise the pressure regulator to cover up what you've screwed up is BS.

Is it at all possible to make the fuel delivery without these 'waves'? If so, how would you monitor the 'waves' in the fuel rails?

I just think it's much better to fix the cause of the problem but that only my opinion.
Also we have been long past 350 RwHp, much closer to 450 RwHp without blocking or modifying the regulator, so yes it can be done properly. It just takes time to do it right and get the necessary field testing done.

That's exactly why I'm waiting to see how the new TTS product for the LLY works out before I make any decisions on buying another programmer.

05, ever used a ball-valve faucet? Better yet, how about a trigger handle on a hose pipe? What happens when you turn the hose on, the line becomes tight with "x" amount of pressure. Ok, squeeze the trigger once very quick and see what happens to the hose, it moves. In laymans terms, this reaction would be "A" wave. The Bosh system uses 1000's of times the pressure and 1000's times faster (Pulse) injections. I think what Steve is getting at would be, the refactory waves that don't cancel but amplify themselves to the point of system destruction. .........

Although I could be wrong.

05, ever used a ball-valve faucet? Better yet, how about a trigger handle on a hose pipe? What happens when you turn the hose on, the line becomes tight with "x" amount of pressure. Ok, squeeze the trigger once very quick and see what happens to the hose, it moves. In laymans terms, this reaction would be "A" wave. The Bosh system uses 1000's of times the pressure and 1000's times faster (Pulse) injections. I think what Steve is getting at would be, the refactory waves that don't cancel but amplify themselves to the point of system destruction. .........

Although I could be wrong.

Ah, that makes total sense! Thanks for your analogy!:ro)

Now I see where this could potentially cause a problem, but wouldn't the rail be leaky at first indicating a problem waiting to escalade? Or would it just make it's way out at all cost?

The problem with the 1093's are 2 fold depending on when. I have over 50 hrs of ploting and graphing the rail pressure and actually have a fuel rail mocked up with an industrial mechanical pressure gauge to try to catch the problem.
Now lets talk about the stock trucks first.I have driven hundereds of miles with a clear jug in the cab to catch when the relief pops and when and what pressures. I have NEVER seen a relief valve pop on accel. It is usually after a decel and then it doesn't reset till under 8k psi rail pressure.Another find is that it usually happens when fuel temp is above 120*.In a hot soak condition(idleing for long periods of time with ac on)And then drive, I could duplicate much more frequently.If you accel hard and then decel ,relief pops, rail pressure drops but does not set a code till you reaccelerate and at that point the commanded rail pressure is 20k+ and the actual is 8-10k. This difference sets the code. If you would not reaccel and would just come to a stop the relief would pop but no codes would be set because the actual and desired are not far enough apart.Once under 8kpsi the relief closes and no one even knows.

Now to my findings.The relief has a small pintle and is held on it's seat by spring pressure. The assembled height of this spring is between .750 and .770. there seems to be slight diferences in the valves I've disassembled.Here's the interesting part. Every spring I have tested@ .770 has a different pressure.Generally 38-41 #. If I put them in a toaster oven @200* for 10 minutes simulating engine heat,Some drop as much as 4-5# spring pressure.That's over 10% with just temp.This spring is not in fuel to keep cool.It is in the rail and will heat transfer off of the engine.Shimming these springs back to cold seat pressure seems to fix the relief problem.With an infared temp gauge I have seen 200*+ at the rear rail relief fitting.Blocking off the relief was only used to prove the diagnosis and should not be used on the street.

Now the 1093's on accel with or without boxes.This is a fuel delivery problem.If the relief does not pop,(now remember I know it didn't pop because I have a jug between my legs catching any fuel that would come out if it did) and you set a 1093 then you have a fuel DELIVERY issue.A1093 only sets if the actual and the desired rail pressure are way apart.(I believe it's 8k psi difference I'll check) The repair for this still seems to be up for debate. A lift pump definately helps.Good filters.

Here's what I found.The injection pump feeds the drivers rail in the front.Out of the center of that rail it feeds into the front of the passenger rail.Now all 8 injectors and their returns are fed by a .025 orfice/dampner.The LB7 had a fuel block that fed both rails evenly and didn't have this (sharing) type setup.The rail inlets on the LB7 were also 1/8 inch.With a big box on these trucks rail pressure drops 3-5k under the desired @WOT even with a lift pump.Without a lift pump there's your 1093.If you enlarge the orfice/dampner at the inlet of both fuel rails(even by a small amount) the rail pressure is usually within 2k.I have an 05 truck with 11k miles since the relief mod and the orfice enlarged and have not seen a 1093.These are a use at your own risk but are proven with MUCH testing on several trucks.Please read carefully. Tim

Thanks Tim! Very informative!

I think the point is: This appears to work better than any other solution right now. It is the only available option today.

If a tuning-based solution exists, it's top secret. I've spend the last several months talking with tuners all over the country telling them we need a solution. Certainly tuning it out would be nice, but if I understand it right, nobody has been able to yet.

The shim-mod is a bandaid. But if the patient is bleeding to death, a bandaid today is better than a suture next year.

Oh, and Steve, I'm kidding about the lift pump. I'm saying we do things that decrease the safety of our vehicles, like spraying nitrous into them, going 115mph, launching in 4WD, over-boosting, etc, etc. There is nothing holy about the relief valve, raping it might be a crime, but it feels so good!

midwest: It sounds like you're gaining some really good info! I've only thrown 1093s in the situations you describe.

And for that matter--Why are some trucks so much more prone to 1093s than others? To date, I've only thrown a 1093 three times in almost a year of ownership. As I've mentioned before, each one of these has occurred when I was really low on fuel. If it's a software issue, I'd think all our trucks would tend to be more similar.

Is it at all possible to make the fuel delivery without these 'waves'? If so, how would you monitor the 'waves' in the fuel rails?

You would need an acoustical tranducer of some type.... something to hear the shockwave from the pulses.

My personal feeling is that this fuel feeding design is the problem. Why is the rh rail being fed out of the middle of the lh rail?The fuel pulse wave Steve talked about has to be totally different in the lh and rh rails. The relief and the pressure sensor do not have the same common ground as in the LB7.This fuel wave issue was in the LB7 but did not affect the relief because it was it was in the distribution manifold along with the pressure sensor.I don't think you're going to get around it by design.
It could possibly be bosch's way to try to control these shock waves to prolong injector life.Who knows.I may try to Retrofit one back to Lb7.The lines from the rails to the injectors will be the problem.

midwest: It sounds like you're gaining some really good info! I've only thrown 1093s in the situations you describe.

And for that matter--Why are some trucks so much more prone to 1093s than others? To date, I've only thrown a 1093 three times in almost a year of ownership. As I've mentioned before, each one of these has occurred when I was really low on fuel. If it's a software issue, I'd think all our trucks would tend to be more similar.

It is a software issue, because when you check for fluid release with a stock tune you get nothing on a healthy truck, but when you put in a big stack, it POURS fuel out the pressure relief. You would not believe how fast it comes out an itty bitty little hole! These programs DO NOT command more than 23000psi, it's the way they handle changing fuel demand. The programs in existence cause a spike in the rail pressure for brief instant when you lift, which dumps the rail pressure hard. The engine sees the dropped pressure, and spikes it up again.

We were told it was insufficient fuel supply at first, but what was funny is didn't happen much when dragracing. This was puzzling. Didn't act like starvation.

For me, the only question is now, how much shim? Not whether to shim it. My thought is to use just enough shim to stop it. But how much is that??? We will try to finish tests this weekend.

What does fuel storage have to do with anything? Bosch did design the fuel delivery system and return system and yes, the supply side was designed for pressure from a lift pump! Racor designed the Fuel Filter assemble. Racor says it's good for < 15 psi! All GM did was route the stainless steel lines from the engine to the tank. Do you really think the fuel lines that run from the tank to the engine and back will not hold 10 -12 psi? Like I said before screwing around with a sealed 28,000 psi regulator is not something that should be done. If you feel it's OK just because someone else is doing it be my guest, I'm just pointing out its not safe nor is it the right thing to do! I would never do it to my truck let alone anyone else's. There is also some people putting a dime under the regulator and blocking the whole thing off might as well just do that too. I just think it's much better to fix the cause of the problem but that only my opinion.
Also we have been long past 350 RwHp, much closer to 450 RwHp without blocking or modifying the regulator, so yes it can be done properly. It just takes time to do it right and get the necessary field testing done.

We have been close to 450rwhp without 1093's??
We have been past 350rwhp without 1093's?

Since you started a thread about 1093's, tell us how you got there.

Midwest, McRat! Congradulations on the efforts to find and cure the 1093's. The future will tell if your efforts are successful. I haven't hit a 1093 yet (I run my truck on the speed limiter once a week for about 200km Monday morning to get to work) but he truck is still stock. Off the topic (but maybe the same cause, reason) a few of these LLY's have an awful surging at light throttle (1100 to 1400) that I experience daily (cruising around the job site, looking for a parking spot for this bus) and I just hate it (that is why it is still stock, I won't keep it if it is not a good daily driver). GM spend a pile of dough on the thing early (some injectors, fuel pump pressure regulator assy., weeks of testing at the dealership then gave up and said no fix at this time). My questions to you (particularly Midwest, with the bottle between your legs, impressive) did you ever experience this surging, is there a noticeable pressure spiking at low pressures (well below the pressure relief setting), is the fuel distribution layout a possible cause (line pressure spiking on on side and not being read on the other)? Any ideas you have ( I think you are the most experienced guy in the world on these LLY systems or some one would have programed a cure by now ie. GM, the tune guys) would be greatly appreciated. I am more than willing to shim up a pressure relief valve (should be adjustable any way if the balance is critical). I may even try to tig up a distribution manifold if the sensors can't do their job properly. Or insulate, if the heat sink into the manifold is an issue (although winter or summer it is there). Any insight?

Here's what I found.The injection pump feeds the drivers rail in the front.Out of the center of that rail it feeds into the front of the passenger rail.Now all 8 injectors and their returns are fed by a .025 orfice/dampner.The LB7 had a fuel block that fed both rails evenly and didn't have this (sharing) type setup.The rail inlets on the LB7 were also 1/8 inch.With a big box on these trucks rail pressure drops 3-5k under the desired @WOT even with a lift pump.Without a lift pump there's your 1093.If you enlarge the orfice/dampner at the inlet of both fuel rails(even by a small amount) the rail pressure is usually within 2k.I have an 05 truck with 11k miles since the relief mod and the orfice enlarged and have not seen a 1093.These are a use at your own risk but are proven with MUCH testing on several trucks.Please read carefully. Tim

Tim

You need to go back and recheck the LB7 as the statement above in red is incorrect. The LB7 does have a fuel block but the sharing and fuel limiters are one in the same between the LB7 and the LLY. The hose routing is different but not enough to cause an issue. The big difference is the location of the Fuel pressure sensor and the pressure waves it see's. The 2006 model year is going to be worse than the current problem as the new relief valve is designed to not re close until pressure is below 3000 psi which means you will need to pull over and shut the truck off. This is Bosch's way of keeping people from fooling around with there system. The software controls how the pump responds to the changes in the system and if it responds to slow it could open the pressure valve by keeping the pressure to high for too long. It is a software issue caused by the aftermarket programs and the valve is doing just what Bosch intended it to do. By raising the opening point your putting the system under much higher demands. If any of you have been around long enough you will remember back when the LB7 first came out. Pressure boxes raised the pressure to the point that the valves were blowing open and the solution than as now was to shim the relief valve. What happen was we saw a large increase in failed fuel sensors and leaking fuel systems. There were also a few reports of fires caused by the high pressure leaks. So as I said before buyer beware.

McRat

How do we make the power without P1093...................... its called testing over and over till the problem has been resolved. The same way we developed the Xtreme for the LB7's! Shimming the regulator is a band-aide for a poor program, I would suggest you go back to your programmer and tell them to fix the software properly. I guess that's the difference between programmers, some just want it out fast to sell for a profit and some of us want it right before we sell it.

...McRat

How do we make the power without P1093...................... its called testing over and over till the problem has been resolved. The same way we developed the Xtreme for the LB7's! Shimming the regulator is a band-aide for a poor program, I would suggest you go back to your programmer and tell them to fix the software properly. I guess that's the difference between programmers, some just want it out fast to sell for a profit and some of us want it right before we sell it.

Which "programmer" should I discuss it with?

I have run:

TTS
Edge
Predator
Bully Dog
Quad
Van Aaken
PPE
Banks

I've discussed it with all on the list except Bully Dog.

It appears the problem is with throttle decay. Slowing it down a few hundred millisecs would be a good place to start.

But since none of the above listed programmers has a fix, and I don't have the tools to edit the ECM myself, I hope you don't mind if I stock up on bandaids. They are on sale this week for four cents each! :D

McRat

You have run our Tow tune which does not set any P1093's and by your own statements our Race tune that you were given to try for awhile set less P1093's than any others you have tested so why would ours have less 1093's than others? It's called testing and adjusting. You should go discuss it with whichever programmer you are currently useing that sets the codes. You go buy your bandaids, but it would be smarter to not cut yourself first!

McRat

You have run our Tow tune which does not set any P1093's and by your own statements our Race tune that you were given to try for awhile set less P1093's than any others you have tested so why would ours have less 1093's than others? It's called testing and adjusting. You should go discuss it with whichever programmer you are currently useing that sets the codes. You go buy your bandaids, but it would be smarter to not cut yourself first!

I'm on nitrous oxide so I don't feel it anyways! :D

What I said is exactly correct.The lh and rh fuel rails are fed by a common distribution block where the relief and pressure sensor are before the rails on the lb7.The lly fills the lh rail (where the relief valve is) and then out of the center of that Rail it feeds the rh rail( where the pressure sensor is).Yes they technically are sharing fuel but not directly out of the other rail.The lb7 has the sensor and the relief in the same block(common ground quote)
Steve are you then adjusting or modifing the pressure regulator tables if fuel control is what you think is wrong. Your not just doing it with timing and pulse width. I don't think anyone else is doing anything but timing and pulse.
I seems to me that I don't recall any 1093's before the rail pressure software update where rail pressure was dropped at certain throttles for excessive smoke(the first update)Yes they had driveability issues but not 1093's. Anyone with a 04 not setting 1093's till software update please resond.

Tim

Like I said you need to go back and retrace the fuel areas on the LB7 as you have missed something. We have no trouble with P1093 on any '04 or '05 LLY with our Tow tune and we use the latest base software from GM so that's not a problem. We have run testing on our Race and Xtreme tunes in the field and have very few P1093 codes at greater than 120 Hp. Those are hard fast test points and Mc Rat was one of the testers with his truck on the Race tune and had much more trouble with other tunes setting codes then he did with ours. At the time of the testing we had more power than anything else he had run. So same truck same hardware just different programs results in greatly different amounts of P1093. In my book that proves it's a software issue. Understanding why is a whole different story.

As far as your heat soak being the problem I think you need to go put a temperature probe into the regulator because the spring is never going to reach the numbers you think it is in normal operation. Just look at what heat soak has to do. It needs to raise the entire rail up to the temperature level your testing and the fuel in the rail and the mass of the rail along with the air dissipating heat around the rail just will not allow that to happen. Sure some areas will be slightly higher than others but not more than a few degrees. Since the regulator is also a sealed unit you must be cutting it apart to install a shim, once you have done that the strength of the part has been reduced as well. Another thing you might want to look at is the description of a P1093 code......................

"DTC P1093 Fuel Rail Pressure Low During Power Enrichment"
Conditions for Setting the DTC
The difference between the commanded fuel pressure and the actual fuel pressure is more than 20 MPa. OR The FRP regulator fuel flow is more than 19 200 mm³ at 800 RPM, or more than 44 400 mm³ at 2,000 RPM.
This should get you going the right direction.

...Since the regulator is also a sealed unit you must be cutting it apart to install a shim, once you have done that the strength of the part has been reduced as well....

Nope. :D

Why not get Fingers to make a board that reads commanded pressure then reports back actual pressure is what was commanded. Poof problem gone.

Call it the "Finger Faker"

.

Nope. :D

You have got to be kidd'in me! There is no stop for the Safety Regulator in the fuel rail. It is torqued to specification and the end of the regulator cuts a groove into the rail to form a seal. So if your just placing a shim in the rail which is the only thing you can do and tighten the regulator to the point where it collapses the case there is no way to know what pressure you will end up with. You could do the same thing by just over tightening the regulator and saying your prayers! :badidea:

Why not get Fingers to make a board that reads commanded pressure then reports back actual pressure is what was commanded. Poof problem gone.

Call it the "Finger Faker"

.

The problem is from the Safety valve opening due to excessive pressure. Once the valve opens your done. Lying to the ECM will not fix it.

Why would it open? I am talking about faking out the ECM on the pressure difference that triggers the 1093

The P1093 is from the lack of pressure. The Safety Valve open due to too much pressure and drains the system down and then the ECM sets the code

The P1093 is from the lack of pressure. The Safety Valve open due to too much pressure and drains the system down and then the ECM sets the code

I thought the 1093 was the issue here. I am saying leave the pressure alone, leave the relief alone, unhook the pressure sensor, build a board that intercepts commanded pressure and reports back on the pressure sensor wiring that the pressure is what was called for.

No difference in the two, no 1093

.

I thought the 1093 was the issue here. I am saying leave the pressure alone, leave the relief alone, unhook the pressure sensor, build a board that intercepts commanded pressure and reports back on the pressure sensor wiring that the pressure is what was called for.

No difference in the two, no 1093

.

The 1093 code is not causing the problem. The code is being set AFTER the safety valve opens since the rail pressure is drained way below desired. Fooling the ECM would do nothing since the rail pressure is already gone at that point, and the valve won't close until actual goes under 8,000. Fooling the ECM in regards to the 1093 won't do anything since the fuel pressure isn't there. Even if you tell the computer it's there, it really isn't.

:exactly: What he said !

TxChristopher

I hope between what I said and what Chad said you now understand it, if not ask away.

I gotcha, I didn't know the problem included the relief valve cutting loose as well. hmmmmmmmmmmmmmm.

Could a different relief valve be engineered with a slightly higher pop pressure that will also close sooner than the original......if it does happen to open?

You have got to be kidd'in me! There is no stop for the Safety Regulator in the fuel rail. It is torqued to specification and the end of the regulator cuts a groove into the rail to form a seal. So if your just placing a shim in the rail which is the only thing you can do and tighten the regulator to the point where it collapses the case there is no way to know what pressure you will end up with. You could do the same thing by just over tightening the regulator and saying your prayers! :badidea:

I can raise the rail pressure relief in any increment I want with simple hand tools without destroying the valve, rail, or seat. It's even re-adjustable, removeable, and requires less than $1 worth of parts to do. Can be returned to stock easily.:ro)

But you are not interested in it, so I'm not sure why you keep trying to guess how it's done. You'll kick yourself when you find out. :D

When we find out if our math jives with the result, someone will post a tutorial.

Dampening the pressure spikes with an acumulator or some sort would probably help. Trouble is getting one in the range you need. Killing the spikes from the coarse grain of the control loop would help keep the relief from popping.

But what do I know....

Mc Rat

You are correct in that I will not do it nor recommend it to anyone. I am only pointing out what the dangers are and why. Since I have the regulators here and the fuel rails I have only pointed out how they go together in stock form. It doesn't take much to figure out what can and cannot be done from there. Screw regulator into hole and tighten doesn't leave much room.

Killing the spikes from the coarse grain of the control loop would help keep the relief from popping.

But what do I know....

Ah come on, now you've gone and done it. Just a little tweak here and there in the PID loops.

I thought about increasing the rail volume or reducing the orifice size on the relief, but if the shim mod works, and there is no downside, then it is far simpler.

Mc Rat

You are correct in that I will not do it nor recommend it to anyone. I am only pointing out what the dangers are and why. Since I have the regulators here and the fuel rails I have only pointed out how they go together in stock form. It doesn't take much to figure out what can and cannot be done from there. Screw regulator into hole and tighten doesn't leave much room.


Like I said, you'll kick yourself when the pics are posted. :D

McRat

I doubt it, Either fix it right or do not bother. :D

The relief can be disassebled in 20 second with no heating or cutting.It is very simple with a custom little tool.I'm sure the dis assembly process did not change the characteristics of the valve.I have dis and reassembled the valves several times and you can not tell.Most of the 1093's I address every day are on stock trucks.These all have the reliefs pop on decel and when you reaccel thats when the 1093 sets.I have not seen a 1093 set on hard accel (if the filter is good) on a stock truck. With a box yes.

Steve,I know diagnostic criteria of a 1093 and am still not shure what you mean in your post.
There is still a big difference in the springs assembled height pressures I have tested.If the releif is not the issue then why the internal PI from Gm and the backorder of fuel rails. If I set the spring assembled height pressure to the high end of what I have seen in all I have disassembled the 1093 is gone.This might explain why one truck has it and another one doesn't.

Geo, I have felt the surge you describe.I have not spent time on it so I'm not sure.In my experience on stock truck you will not set a 1093 driving hard like you describe if you have a good filter.It seems to happen when you accel hard is if to pass a car, and then let off to settle back in traffic,and then step back on the throttle.I'll try to pay a little more attention on the surge.

If the releif is not the issue then why the internal PI from Gm and the backorder of fuel rails. If I set the spring assembled height pressure to the high end of what I have seen in all I have disassembled the 1093 is gone.This might explain why one truck has it and another one doesn't.

While there seems to be a lot of talk lately of fixing the P1093 issue some of the ideas being floated around are pretty far out there. If you attempt these repairs all I can say is buyer beware! People are talking about blocking the SAFETY PRESSURE VALVE and Shimming the Safety Pressure Valve. I am sorry but neither of these are a fix let alone safe. The purpose of the valve is much the same as a safety valve on you hot water heater at home. It is designed to open ONLY when there is a problem and not until then. There have been reports of GM having some bad valves and by all means those valves should be replaced, but block or shimming a valve set to open at 28,000 psi is just down right stupid! Think about what it takes to cut steel in half as that is just what your playing with. Look at the size they have made these parts to hold this level of pressure and think about it.
Yes, there is a problem when increasing the performance above stock that needs to be solved but blocking or shimming the safety valve is not a fix..... it is down right dangerous.


If the valve is bad then it needs to be replaced, look at my previous post. Disassembly of the regulator is fine for testing but is not a fix. If the springs are bad then replace the valve. To raise the pressure to some unknown amount is just asking for trouble. Remember this was done on the LB7 in the early days only to find out it caused pressure senders to start leaking and some reports of leaking lines. GM goes on back order on parts for all kinds of reasons but I just bought fuel rails for two engine dyno motors and they were here in 4 days so the backorder cannot be all that bad.

Please explain why on one truck with no parts changes there are no P1093 codes stock, then program "A" is installed and still no P1093. Then program "B" is installed and its P1093 all day long, then install program "C" and it gets a P1093 once in awhile. Do you really think the Safety Pressure Valve knows the program changed?

Could a different relief valve be engineered with a slightly higher pop pressure that will also close sooner than the original......if it does happen to open?


That is the whole argument....what McRat is doing is doing exactly what you want engineered. Diesel Tech. is saying he can minimize the violent spike in fuel rail psi. from WOT to closed throttle that causes the valve to open by fine tuning the programming. This could keep everyone from moding the relief valve.

Argument=

1. Relief valve mod fixes problem, but could be unsafe and cause fuel rail leak or fire.

2. Programming can fix problem, but there are no high performance programs that don't have this problem and WE WANT HIGH PERFORMANCE PROGRAMS!!

End result....We buy high performance programs that cause the problem and fix it with the mod. OR, we wait for TTS to fix the problem because the other manufactures didn't (and don't intend to) fix it in their programs.

If the valve is bad then it needs to be replaced, look at my previous post. Disassembly of the regulator is fine for testing but is not a fix. If the springs are bad then replace the valve. To raise the pressure to some unknown amount is just asking for trouble. Remember this was done on the LB7 in the early days only to find out it caused pressure senders to start leaking and some reports of leaking lines. GM goes on back order on parts for all kinds of reasons but I just bought fuel rails for two engine dyno motors and they were here in 4 days so the backorder cannot be all that bad.

Please explain why on one truck with no parts changes there are no P1093 codes stock, then program "A" is installed and still no P1093. Then program "B" is installed and its P1093 all day long, then install program "C" and it gets a P1093 once in awhile. Do you really think the Safety Pressure Valve knows the program changed?


An LLY will go a month without a 1093, then throw 10 in a week, then go another month without. There is certainly something we haven't seen that is doing that.

With a big tune, you will bleed out the relief without setting 1093's as well.

I can raise the pressure to any value over 23000. Unknown? Just as unknown as any other other calculated value. The spring is linear rate. We know the factory preload distance. Want 10% gain? Do the math and increase the preload.

Testing today is going very well. Better than expected. Need to start working on the tutorial.

I've been running a modified relief valve on my 2002 for a LONG time now. Before it I have fuel in oil when using the old pressure box. After I never had it repeat regardless of what I ran.

The pressure box has been pretty popular with the Dodge guys as a nice simple means to gain HP.

I've been running a modified relief valve on my 2002 for a LONG time now. Before it I have fuel in oil when using the old pressure box. After I never had it repeat regardless of what I ran.

The pressure box has been pretty popular with the Dodge guys as a nice simple means to gain HP.

I'm lost. :(

So the stock relief valve would blow off and this somehow caused you to have fuel in the oil? :help2:

I just got back from a trip and had a situation where the check engine lite came on and I lost power ,would not go above 2000 rpm, I pulled over ,it corrected itself , started out and did it again, I disconnected the edge and went from Lake Shasta CA to San Diego and back to Oregon , no problem, I reconnected the edge , went another 1500 miles ( this is all pulling at 22 thou + , It happened again , twice , I again disconnected the edge and then it happen several more times , each time under HARD pull and when I backed way out of it on the next hills it was OK , I stopped and got a code read at Autozone (P 1093) called my dealer and he said it was Low fuel pressure and likley a regulator or pump, then I get home and saw this thread , any input would be appreciated , I have 62 thou now (04 LLY ) and this is the first time for this , After I had the code read the check engine lite went out in Redding CA and got to LA and home to Las Vegas no more problems , but I did go real easy on every hill .PSS , I have an appointment to do a Radiator/hood /fender mods for the overheating , I will post this in that thread as well.

I'm lost. :(

So the stock relief valve would blow off and this somehow caused you to have fuel in the oil? :help2:

Yep, I believe that in my case it had to do with where the fuel goes when it dumps, torque on return lines, and a piece in the OE fuel pickup assembly that Diesel Tech hadn't been able to locate as of last March or so. I had 24% fuel dilution IIRC and ran the same box later without incident.

I just got back from a trip and had a situation where the check engine lite came on and I lost power ,would not go above 2000 rpm, I pulled over ,it corrected itself , started out and did it again, I disconnected the edge and went from Lake Shasta CA to San Diego and back to Oregon , no problem, I reconnected the edge , went another 1500 miles ( this is all pulling at 22 thou + , It happened again , twice , I again disconnected the edge and then it happen several more times , each time under HARD pull and when I backed way out of it on the next hills it was OK , I stopped and got a code read at Autozone (P 1093) called my dealer and he said it was Low fuel pressure and likley a regulator or pump, then I get home and saw this thread , any input would be appreciated , I have 62 thou now (04 LLY ) and this is the first time for this , After I had the code read the check engine lite went out in Redding CA and got to LA and home to Las Vegas no more problems , but I did go real easy on every hill .PSS , I have an appointment to do a Radiator/hood /fender mods for the overheating , I will post this in that thread as well.

There are two types of P1093's:

a) Fuel delivery issues
b) Tuner spikes

This mod fixes the second kind, not the first kind.

Loosing or reducing the spikes will require changing from a pure feedback loop based on delta-P to a predictive control loop based on predictied demand and trimmed by delta-P.

The nature of this common rail system is that it is very digital in charactor. The injectors can go from full flow to nothing to full flow in a matter of m-sec. Waiting for the pressure rise before reacting, as appears to be the case, will generate spikes and with the flows involved and the small volume of the system, the spike can be too much.

Oh, FWIW, the problem with the relief valve is that it is not resetting. Fix that, and you will have the protection from overpressure AND no 1093's.

But what do I know....

Yep, I believe that in my case it had to do with where the fuel goes when it dumps, torque on return lines, and a piece in the OE fuel pickup assembly that Diesel Tech hadn't been able to locate as of last March or so. I had 24% fuel dilution IIRC and ran the same box later without incident.

Where does the fuel go when it's dumped?

Oh, FWIW, the problem with the relief valve is that it is not resetting. Fix that, and you will have the protection from overpressure AND no 1093's.

But what do I know....

The relief valve is a classic needle and seat system. It does reseat itself after knocking down the rail pressure. The reason it will bleed a lot of fuel is that it goes into a cycle. It blows the valve, pressure drops below 23k, it tries to get the pressure back, spikes again and repeats. Just a little fluid will knock the pressure way down as liquids don't compress much.

A smaller orifice would help, but then if the system really did go haywire, it might not be able to bleed off the entire CP3 output.

Oh, FWIW, the problem with the relief valve is that it is not resetting. Fix that, and you will have the protection from overpressure AND no 1093's.

But what do I know....

Seems to me that is the proper solution as well. This has never been an issue for me so I haven't looked at it to the extent most of you have, but after getting a handle somewhat on the problem a valve that holds its seat is the proper fix.

.

Back to the tank via fuel return lines. On the LB7's part of that system is internal to the head. If the relief lifts, the flow would probably be the full flow of the pump. If there is a restriction, you could easily see up to the full pressure of the pump.

I believe this relief by design is why it doesn't reset till lower pressure.The tiny pintle/needle is actually in a tight fitiing bore and then against a seat.Once it pops any flow through the orfice with this tight fitting bore seems to hold it off the seat.The lb7 had more of a needle and seat design with a longer more linear spring.Once it poped the design allows the pressure to bleed off quickly and then reset.
The 06 duramax has a new design again that doesn't reset till 3k so you must shut the truck off to get the rail pressure under 3k.

I was actually going to try to relax today and go out in the boat but it's raining so I'll get some pictures taken and post the differnce in the 2 designs.Tim

I believe this relief by design is why it doesn't reset till lower pressure.The tiny pintle/needle is actually in a tight fitiing bore and then against a seat.Once it pops any flow through the orfice with this tight fitting bore seems to hold it off the seat.The lb7 had more of a needle and seat design with a longer more linear spring.Once it poped the design allows the pressure to bleed off quickly and then reset.
The 06 duramax has a new design again that doesn't reset till 3k so you must shut the truck off to get the rail pressure under 3k.

I was actually going to try to relax today and go out in the boat but it's raining so I'll get some pictures taken and post the differnce in the 2 designs.Tim

would it be possible to use the LB7 bleed off on the LLY?

Beat me to that question :)

Sorry I didn't get the pictures posted. It quit raining and I actually got to go out in the boat. I will get them tomorrow. Please be patient.

No there is not an easy way to retrofit the lb7 relief. Tim

While there seems to be a lot of talk lately of fixing the P1093 issue some of the ideas being floated around are pretty far out there. If you attempt these repairs all I can say is buyer beware!...

The research I've done on my part is non-profit. I credit Tim at Midwest for the idea, I just went off his research and backed it up with a little help from my friends who wish to remain nameless.

I'm not in the business of selling performance parts. I do reverse engineering, testing, and inspection of High-Performance components for a living. We are putting these mod's on both of my trucks for racing purposes.

If you want fewer 1093's today, get ahold of Tim or me and we can help. In my case, I'll tell you who in SoCal can do it for you, or tell you how to do it yourself.

Hopefully a software based solution comes up shortly.

The relief valve is a classic needle and seat system. It does reseat itself after knocking down the rail pressure. The reason it will bleed a lot of fuel is that it goes into a cycle. It blows the valve, pressure drops below 23k, it tries to get the pressure back, spikes again and repeats. Just a little fluid will knock the pressure way down as liquids don't compress much.


A higher K spring would also help if that is the case. Still set to the same pop-off, but would not open as drastically.

Yeah, a spring with a higher rate per mm but less preload distance would be nice.

Back to the tank via fuel return lines. On the LB7's part of that system is internal to the head. If the relief lifts, the flow would probably be the full flow of the pump. If there is a restriction, you could easily see up to the full pressure of the pump.

This will never happen. The return line connections are a simple low pressure rubber hose with a spring clamp retainer. If the pressure was to rise much above 30 psi it would push the rubber hose off. Also on the injector returns a LLY are just pushed in place where the LB7 use solid lines with Banjo bolts. The volume of fluid needed to reduce the pressure is very small so the pressure drop across the safety relief valve is huge. 28,000 is the relief pressure but return pressure is less than 3 psi. The feed hole to the safety relief valve is ~ .033 and the fuel rail has a ~.028 feed hole. This is true for both the LB7 and LLY. So the system is flow limited by the rail inlet size. Opening the rail limiter will just make the problem worse as it allows more in and now takes the flow limiter designed into the system, out of the system.

There are two problems here and two proper ways to fix them.

1. Stock truck sets codes and Safety Relief Valve is found to leak....... replace valve.

2. Install aftermarket products and truck sets codes....... get aftermarket product fixed.

After market products may need additional engine/truck mods to accomidate the product. :) No one expects to cross the higher performance lines without additional supporting mods.

I need to back off the discussion here. I don't get the codes (yet) and I do not have the tools to add the dozen or so lines of code to inject predictive control into the feedback loop for a software solution. The discussion still interests me since I get paid well to solve these sorts of problems.

Sorry everyone I didn't get the pictures posted.The day got away from me. I burried a good friend today and then after the funeral I tripped into a big pile of beers and they went right down my throat. I'll try to post now if I can figure it out.

It won't download I'll try in the morning at the shop it's been a long day. Tim

Ok I'm an idiot how can I get the pictures posted if the file size is too large. I guess I can retake them. Any help Thanks in advance. Tim

Ok I'm an idiot how can I get the pictures posted if the file size is too large. I guess I can retake them. Any help Thanks in advance. Tim

e-mail them to me at dream749@aol.com and I will host them :cool:

The first picture is the distribution manifold and relief assy for the lb7.Notice the pressure sensor and relief in the same manifold.The 3 fiiitings are inlet,and outlet to RH and LH rails.The relief pintle is much larger and bleeds off much quicker and resets.

The next picture is the lly relief disassembled and compared to the lb7.Yes that little pin is the pintle. The pintle fits tightly into the bore of the seat.The washer with holes sits on the pintle and then the spring.Any flow through the pintle seems to hold it off the seat till pressure drops under 8k.

This weekend I am taking several to a cp3 test stand to test.I originally had some tested that were replaced under waranty. Some of these leaked as low as 23k psi.When I recieved them back they were disassembled and spring pressures were tested. That was the information in my original post.I recieved information that last week a new one was tested and poped@ 26.8k at 145* fuel temp on the cp3 test stand.I am taking 2 new valves,1 removed from a new fuel rail from GM SPO and one from bosch along with some modified. I'm excited to see the results.This crap just interests me. Tim

It would appear that the LB7 has a more 'progressive rate' spring in it. Where the LLY unit is almost Absolute as far as compression over unit time.

Please keep us posted on the test results.

It would appear that the LB7 has a more 'progressive rate' spring in it. Where the LLY unit is almost Absolute as far as compression over unit time.

Please keep us posted on the test results.

:exactly:

Additionally IMHO, if we are talking about making sure the relief valve is up to spec and doing it's job properly then I'm all for buying a "certified" and tested piece.

However if we are talking about raising the fuel pressure by some unknown quantity in a DIY mode by shimming the spring some arbitrary amount and then hoping for the best, I'm out. To me this becomes a huge safety issue.

I for one, am not willing to sacrafice my wife and two daughter's safety with unknown and possibly excessive fuel pressure, nor my own.

Kudos to Tim for seeking out a CP3 test stand and doing the research. Does this stand have the ability to rate the flow/pressure capacity of a cp3? How about injectors?

It would appear that the LB7 has a more 'progressive rate' spring in it. Where the LLY unit is almost Absolute as far as compression over unit time.

Please keep us posted on the test results.

:exactly:

Additionally IMHO, if we are talking about making sure the relief valve is up to spec and doing it's job properly then I'm all for buying a "certified" and tested piece.

However if we are talking about raising the fuel pressure by some unknown quantity in a DIY mode by shimming the spring some arbitrary amount and then hoping for the best, I'm out. To me this becomes a huge safety issue. :(

I for one, am not willing to sacrifice my wife and two daughter's safety with unknown and possibly excessive fuel pressure, nor my own. Lets' go fast, but let's do it intelligently. :(

Tim, does this stand have the ability to rate the flow/pressure capacity of a cp3? How about injectors?

:exactly:

Additionally IMHO, if we are talking about making sure the relief valve is up to spec and doing it's job properly then I'm all for buying a "certified" and tested piece.

However if we are talking about raising the fuel pressure by some unknown quantity in a DIY mode by shimming the spring some arbitrary amount and then hoping for the best, I'm out. To me this becomes a huge safety issue.

I for one, am not willing to sacrafice my wife and two daughter's safety with unknown and possibly excessive fuel pressure, nor my own.

Kudos to Tim for seeking out a CP3 test stand and doing the research. Does this stand have the ability to rate the flow/pressure capacity of a cp3? How about injectors?

What? You want to live FOREVER??? :rolleyes:

Seriously, here's a point to ponder...

Does the LB7 puke? How high will it spike (if at all)? Is LB7 bursting related to the PRV puking? Time to look at the LB7 as well. Might be some ponies in hiding.

We are raising the pressure 15% by preloading the straight wrapped spring 15% more. Observed pressure increase is 179mpa up fron 176mpa per Tech II.

This mod is not for the faint of heart. :eek:

But then again, neither is going >100mph in 4WD with a vehicle that handles about as good as a school bus. :D

What is the benefit of raising the rail pressure, how do you know if the pressure relief is to low?? Will this cause bursting??

We aren't raising the rail pressure.

Your relief valve is too low if you get fluid in the bottle (see other thread in this forum by me).

Current thought on bursting is that pressure drops so low that the injectors can't operate. Is it? Dunno.

What? You want to live FOREVER??? :rolleyes:

Seriously, here's a point to ponder...

Does the LB7 puke? How high will it spike (if at all)? Is LB7 bursting related to the PRV puking? Time to look at the LB7 as well. Might be some ponies in hiding.

We are raising the pressure 15% by preloading the straight wrapped spring 15% more. Observed pressure increase is 179mpa up fron 176mpa per Tech II.

This mod is not for the faint of heart. :eek:

But then again, neither is going >100mph in 4WD with a vehicle that handles about as good as a school bus. :D

As long as your quantifying the changes, and have confidence in the ability of the LLY fuel and return system to handle the pressure increases and spikes. Remember the return system from the injector on an LLY is plastic and rubber with spring clamps. The LB7 is hard lined. And yet IIRC many did this similar mod to the LB7s years ago and had trouble with the fuel system leaking. By changing the relief valve you have the potential to raise rail pressure do you not?

I just would rather not see you not drive the hamsters around in a truck that could leak fuel and burst into flames. :(

Probably safer in a bombed diesel than a stock gasser. Those things ignite if you fart too close to the motor! :eek:

...

I just would rather not see you not drive the hamsters around in a truck that could leak fuel and burst into flames. :(

Back when I was desert racing, a guy used to take his dog with him. He had a piece of carpet fastened to his fuel tank, and the dog held on with it's claws. Bob? Think he was with the Desert Vipers.

Anyhow, this gal comes up to Bob and goes, "HOW DARE YOU!!! WHAT IF YOUR POOR DOG FALLS OFF!!??"

Bob grins at her, then gets serious, "Miss? What if I fall off?"

...By changing the relief valve you have the potential to raise rail pressure do you not? ...

That is the curious thing. We are not seeing significantly more pressure (179 vs 176). Nor are we seeing anywhere near 28k psi. Maybe a vibration or pressure wave pops it.

A better solution would be a higher rate spring with less preload.

What? You want to live FOREVER??? :rolleyes:
We are raising the pressure 15% by preloading the straight wrapped spring 15% more. Observed pressure increase is 179mpa up fron 176mpa per Tech II.

This mod is not for the faint of heart. :eek:


McRat

If you are seeing 176- 179 mpa called out for with the Tech II then the programmer your useing is raiseing the rail pressure. Stock rail pressure is 160 mpa only on all LLY and LB7 engines. This would explain why your opening the Safety Valve as your close to 20 mpa (2900 psi) over the stock pressure to start with! It appears as though the Safety Vavle is working correctly and you've just pushed the pressure too high.

No, observed actual pressure gained 3mpa. That's it.

No programmer I've tested yet raises the pressure that I'm aware of.

Mc Rat

I have only quoted what you said, 176 - 179mpa correct ? If you used a Tech II to get these numbers then the pressure is raised. :confuzeld

176 before, actual
179 after, actual

Commanded = 159 peak.

Do the LB7's spike or puke?

Now were getting somewhere, What ever box your running is most defiantly the problem not the safety valve. What ever they have done has cause the rail pressure to be greatly above where it should be by your own observations 179 mpa = 25,962 psi, commanded is 159mpa = 23061psi. Your programmer is causing a 12.5% error. At these pressures that a big error!

Do the LB7's puke or spike?

Now were getting somewhere, What ever box your running is most defiantly the problem not the safety valve. What ever they have done has cause the rail pressure to be greatly above where it should be by your own observations 179 mpa = 25,962 psi, commanded is 159mpa = 23061psi. Your programmer is causing a 12.5% error. At these pressures that a big error!

None of the tuners COMMANDS more than 159. Actuals will spike to 179 though.

Let's see, is that a "Yes It Does" ignore, or a "I don't know" ignore?

Just a thought while reading this for the conspiracy theorists here- Does anyone think that GM modified the setup to prevent or limit aftermarket power upgrades? The downside is they have created some new warranty problems with these codes, but they may have prevented/limited a lot of bad warranty on very costly items due to upgrades.

OCDUNE

The LB7 does have some spikes but they can be controlled with proper programming. The LLY has the same controls to control the CP3 pump that need to be tuned to avoid large spikes. It appears as though your seeing much larger spikes of pressure than the system does stock. This is a programming issue not the Bad Safety Valve issue. It needs to be solved by your programmer. They have created a 12.5% error into the system by whatever they are doing.

Pardon my immense stupidity, (I did not sleep a wink last night) But would it be possible to add the LB7's more 'progressive' spring into the LLY's Valve and accomplish the desired effect without raising the absolute safe threshold of pressure?

Just throwing out an idea.

I think the whole idea of the behind the "big dump" design is to get it to throw a code if the valve pops off. While this is nice for diagnostics, it is bad for performance applications.

No "programmer" that I am aware of is boosting rail pressure. The spike has to do with how the CP3 solenoid is being handled.

If the LB7 relief poped on decel like the LLY does you would likely not know because it pops and resets very quickly.Remember the code sets when the difference between commanded and actual rail pressure are 20mpa apart during POWER ENRICHMENT.The LLY does not seem to reset till under 8K psi rail pressure (from my tests),So it is likely that when you reaccel the valve may not have reset and THEN the 1093. Not just BECAUSE it poped.
I'm sure there are fuel spikes in the LB7 system also but it is more forgiving because the relief resets very quickly.The relief pintle is larger on the LB7 but the pin and bleed orfice is about the same size.The LB7 relief does not flow much more than the LLY(remember the orfice is the limiter) it is just capable by design to reset quicker because of how fuel flows around the pintle pin and then through larger holes in the pintle body to the return. The LLY pintle is held off it's seat much easier with any flow because the fuel has to flow around the pintle in tight fitting bore before it can vent to return.Is this a built in barometer by Gm for aftermarket tunes? Make your own decesion.
These LARGER fuel spikes in aftermarket tunes will likely have to be addressed as Steve is doing but the inconsistancy in SOME reliefs is a problem.This relief isuue still rears it's ugly head on stock trucks every day accross the USA but it's an epademic(sp) with some aftermarket tunes.Tim:rant:

Tim

I agree that the bad stock valves need to be address by GM. What we really need to do is somehow get the real specifications on the safety relief valve and test to those numbers. I am sure this is one of the ways Bosch and GM set out to stop the power being raised. That being said the same responsibility goes to the aftermarket manufacture for there products. This is just why we have not released the big tunes, making power was easy fixing everything else that comes with it is not.

My appointment this weekend with the cp3 test stand will be interesting. I have A few close contacts with engineering budies that may come with. This is a bosch testing facility so maybe some answers.Bosch themselves seem prety tight lipped.Maybe a consensus can be drawn. Tim

Do you know if this stand will bring the pressure up slow so the real cracking pressure can be measured?

I love it when things can be fixed simply. Manufacturing tolerances have improved since the old days (I remember having to keep 10 oil pressure sending units in stock for VW's to make sure that I had a good one), but they are still built by the lowest bidder. Midwest, thanks .

Tim

Any test results from this weekend?

I seems to me that I don't recall any 1093's before the rail pressure software update where rail pressure was dropped at certain throttles for excessive smoke(the first update)Yes they had driveability issues but not 1093's. Anyone with a 04 not setting 1093's till software update please resond.

I have an 6/04 and never have had a reflash. I've never thrown a 1093. I've run the predator on 100hp for well over 5k miles and have been running the ppe hot extreme set on kill for awhile. I run this truck hard, doing everything discussed here. Software issue?

Thanks for all the testing gentlemen.

Rob

Well I'm very disappointed after this weekend.The upper management of the testing facility got wind of what were going to test and put the stops to the tests.They said it was "a conflict of interest" Because they test for bosch and Gm and other diesel manufacurers.Because I was testing and possibly finding a"problem" with companies they work for, they did not want to be involved.So back to the drawing board.
I have another place that I can get to test them but I can't get there to witness with my hectic schedule.They will test and just report back. I will keep everone posted. Tim

Unsurprising they don't want someone to find and possibly fix the problem that they can't.

I have an 6/04 and never have had a reflash. I've never thrown a 1093. I've run the predator on 100hp for well over 5k miles and have been running the ppe hot extreme set on kill for awhile. I run this truck hard, doing everything discussed here. Software issue?

Thanks for all the testing gentlemen.

Rob

Mine is a very early 04, January build I believe (got it in March). Running Edge for over 15K miles on mostly level 4 and now level 5 with the trans done for over 5K miles and never a 1093. I keep reading this post looking for a fix for a problem that I may never have. Keeping my fingers crossed.

Good Luck to all.

Oh,

PS. I've had the latest re-flash as of this spring.

Oh,

PS. I've had the latest re-flash as of this spring.

This is just what I believe we will find in the long run. That trucks with bad Safety Relief Valves will show with any level software. I have reviewed the changes GM made in the calibration and do not believe they will make a difference one way or the other. In my personal truck I have run all three levels of software and found no differences with the P1093 problem. It boils down to the upgrade your running and how bad your stock valve is. I have customers testing product that set 1093's with other tunes but do not with our test product, so I believe were getting to the end of the road on the Race level(120 HP) tune and making good headway on the Xtreme tune. Those truck with a bad valve will set the code regardless and need to have the valve replaced.

... Those truck with a bad valve will set the code regardless and need to have the valve replaced.

Or perhaps shimmed to the proper preload. :D

McRat

Is the how to out yet or did I miss it?

DOH!!! I'll post it now. Didn't get very good pictures, but I'll post anyways.

sweeeeet ... thx

SO where are the pics?

SO where are the pics?

McRat created a new thread here

http://www.dieselplace.com/forum/showthread.php?t=37711

Enjoy

OCDUNE