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Discussion Starter · #1 ·
Hey guys, I'm new to the diesel tuning thing although I've been around the gasser tuning area for a while (strictly as an amateur). Started in to Hot Rodding when things still had carburetors.

Lots of general theory about the way a gas engine is supposed to run - stoich or slightly lean at cruise, best power AFR, best timing, etc.

Anyway, when things really started to heat up in the computer based tuning arena, there were lots of post popping up about how to best tune an injected gas engine with the new tools and the tables the factory had provided.

Well, haven't really seen the same thing yet in the diesel arena, was thinking maybe it's time to get something like that going.

I was looking over the +60hp tune from the repository and comparing it to the stock tune for LLY's (haven't been able to download my LBZ stock tune yet).

Looks like there are three boost level tables - A,B, and C ? Is that right ? And each one is progressively higher than the previous one by about 1.7 psi ? Seems like a pretty small difference between the tables ?

Also, seems like there is a seperate table for each level with egr on and egr off ?

Ok, why three tables, why so close to each other, and why the egr on and off versions of each ?

And what is mm3 per stroke ?

These at least seem somewhat intuitive, but then we come to vane position. WTF ? This is totally new. You can control boost and vane position seperately ? What is the optimum ? What are we shooting for ?

Then there is injection pulse, and timing. Ok, so injection pulse timing controls the fuel going in, but how do you know when you have enough, or too much ? And what is the optimum timing for different conditions (at least theoretically ?)

And then of course, there is fuel pressure.

Very interested in learning, just not sure where to start.

Any advice ?
 

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hahaha :lol: i think weve all kinda been through this, ive asked these same questions a couple times! i dont know how much i can help and guys help me out if im wrong here, but mm3 is injector opening time or pulses per min, mpa is fuel pressure, i better leave this one to the pros though!
 

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Discussion Starter · #3 ·
yeah, I've read bout all the post here and at EFILive's forum.

McRat's 20-20 tune did explain some things, but I'm a theoretical kind of guy. Like to know why I'm doing whatever it is I should be doing. (BSME training did that to me :p).

Don't know much about the theory of optimizing diesel engines.
 

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ya i still have some problems wondering what im doing to my poor truck!
 

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Extinct;1528725; said:
Looks like there are three boost level tables - A,B, and C ? Is that right ? And each one is progressively higher than the previous one by about 1.7 psi ? Seems like a pretty small difference between the tables ?

Also, seems like there is a seperate table for each level with egr on and egr off ?

Ok, why three tables, why so close to each other, and why the egr on and off versions of each ?

Any advice ?
The A,B and C tables use Barometric Pressure to determine which one the engine will be using...C is approx. 5000ft. elevation and lower, don't know where A takes over...There are several of these A,B,C tables...
 

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Extinct;1528725; said:
Hey guys, I'm new to the diesel tuning thing although I've been around the gasser tuning area for a while (strictly as an amateur). Started in to Hot Rodding when things still had carburetors.

Lots of general theory about the way a gas engine is supposed to run - stoich or slightly lean at cruise, best power AFR, best timing, etc.

Anyway, when things really started to heat up in the computer based tuning arena, there were lots of post popping up about how to best tune an injected gas engine with the new tools and the tables the factory had provided.

Well, haven't really seen the same thing yet in the diesel arena, was thinking maybe it's time to get something like that going.

I was looking over the +60hp tune from the repository and comparing it to the stock tune for LLY's (haven't been able to download my LBZ stock tune yet).

Looks like there are three boost level tables - A,B, and C ? Is that right ? And each one is progressively higher than the previous one by about 1.7 psi ? Seems like a pretty small difference between the tables ?

Also, seems like there is a seperate table for each level with egr on and egr off ?

Ok, why three tables, why so close to each other, and why the egr on and off versions of each ?

And what is mm3 per stroke ?

These at least seem somewhat intuitive, but then we come to vane position. WTF ? This is totally new. You can control boost and vane position seperately ? What is the optimum ? What are we shooting for ?

Then there is injection pulse, and timing. Ok, so injection pulse timing controls the fuel going in, but how do you know when you have enough, or too much ? And what is the optimum timing for different conditions (at least theoretically ?)

And then of course, there is fuel pressure.

Very interested in learning, just not sure where to start.

Any advice ?
Diesels with common rail direct injection are unique. They are very easy to get 100hp of extra power by just adding some fuel (mm3) and timing (at what point around TDC the injector opens). I haven't seen a LBZ tuning file yet bit I assume the different Boost tables are the same as the 2nd gen LLY tables. There are different tables based on Baro readings. As far as the EGR boost tables it's probably just an emissions thing.

mm3/stroke is how much fuel is dumped into the cylinder at each injection pulse.

I haven't had much luck with the vane position for the turbo. You can just adjust the amount of boost with the Desired Boost Levels. That's the best place to start IMHO.

As far as timing goes you do not want to increase it too much or you will get cylinder wash and that isn't good. I set my max injection timing to 40deg and my injection tables don't go past 34deg. Other people may do this differently. There is a PID that gives you the number of crank rotation degrees while the injector is open. I try to split the injection pulse so 50% is pre TDC and 50% is post TDC.

With a 60hp tune you shouldn't need lift pumps and I'd leave the fuel pressure set to stock levels.

These are just my suggestions. I'm sure others will chime in. Good luck!
 

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i figure table A is around 12,000 ft. i run in tabel B all the time, 7200-9000+ft.
mm3 is basicly how long the injector is open or how far the right pedel is pushed down.

What exactly is cylinder wash? my guess is the fuel is delivered to earily can burn fast enough and puddels?
 

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2500hd05;1528839; said:
i figure table A is around 12,000 ft. i run in tabel B all the time, 7200-9000+ft.
mm3 is basicly how long the injector is open or how far the right pedel is pushed down.

What exactly is cylinder wash? my guess is the fuel is delivered to earily can burn fast enough and puddels?
It's a bad thing since I think fuel can get below the rings (probably worst case senario) and then ignite when the rest of the fuel does. All I know is it makes a nasty noise that doesn't sound like it's good for the motor.
 

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Discussion Starter · #9 ·
Here is what I understand thus far.

Fuel:

Injection pulse and injection pressure impact the amount of fuel that goes in to the engine. Because diesel engines do not have throttles, the amount of fuel directly impacts the horsepower produced at any given rpm. Therefore the engine power is controlled by the amount of fuel that is injected. However, there are a few things I do not understand about fueling.

Like - how much fuel is too much ? Someone mentioned cylinder wash, which is normally when you have so much fuel that it can't all be burnt and some liquid fuel gets by the piston rings into the crankcase. However, I would think that long before you get to that point power would actually decrease from too rich a mixture. Is that true ? Is there a way to measure that point with instrumentation (rather than trial and error dyno or strip runs ) like a wideband ?

Timing:

If I understand correctly, this is kinda like ignition timing on a gas engine, except that you are timing the injection of the fuel instead of the spark. The idea is to inject it at the optimum point before top dead center where the most benefit is obtained from the resulting ignition and cylinder pressure. To soon, and the pressure builds too fast and power is reduced (you also sometimes get knock in a gas engine), too late and power is reduced also. In a gas engine, if you run too little advance – you also can really heat up the engine. I’m guessing that would be what would cause EGT’s to go up really high in a diesel as well ?

The real part I don’t understand on a diesel is the pilot injection thing – what does that do, what is it about ?

VVT/Boost:

Ok, from what I understand about this, the variable vane thing is there to help build boost quickly at low engine speeds and not limit boost production at higher engine speeds. So under WOT you would want the vanes closed (?) at lower speeds and gradually opening as engine speeds increased – right ?

From what I have read, some mpg gains can be had by opening the VVT’s at low load to reduce backpressure and reversion EGR.

Is the VVT the only way to control boost, or is there an electronic wastegate as well ?

Here is the real question on this subject – part throttle boost/fueling. What is the optimum between boost and fuel at part throttle for best economy, smoothness, and power – more boost and less fuel, or more fuel and less boost ?

Can anyone help fill in some of the blanks here ?

OK, with respect to the three boost tables, why does it make a hill of beans difference what the altitude is ? With a boosted engine, you can control the intake manifold pressure to be whatever you want it to be at all rpm/throttle openings - right ?
 

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Extinct;1530268; said:
Here is what I understand thus far.

Fuel:

Injection pulse and injection pressure impact the amount of fuel that goes in to the engine. Because diesel engines do not have throttles, the amount of fuel directly impacts the horsepower produced at any given rpm. Therefore the engine power is controlled by the amount of fuel that is injected. However, there are a few things I do not understand about fueling.

Like - how much fuel is too much ? Someone mentioned cylinder wash, which is normally when you have so much fuel that it can't all be burnt and some liquid fuel gets by the piston rings into the crankcase. However, I would think that long before you get to that point power would actually decrease from too rich a mixture. Is that true ? Is there a way to measure that point with instrumentation (rather than trial and error dyno or strip runs ) like a wideband ?

Timing:

If I understand correctly, this is kinda like ignition timing on a gas engine, except that you are timing the injection of the fuel instead of the spark. The idea is to inject it at the optimum point before top dead center where the most benefit is obtained from the resulting ignition and cylinder pressure. To soon, and the pressure builds too fast and power is reduced (you also sometimes get knock in a gas engine), too late and power is reduced also. In a gas engine, if you run too little advance – you also can really heat up the engine. I’m guessing that would be what would cause EGT’s to go up really high in a diesel as well ?

The real part I don’t understand on a diesel is the pilot injection thing – what does that do, what is it about ?

VVT/Boost:

Ok, from what I understand about this, the variable vane thing is there to help build boost quickly at low engine speeds and not limit boost production at higher engine speeds. So under WOT you would want the vanes closed (?) at lower speeds and gradually opening as engine speeds increased – right ?

From what I have read, some mpg gains can be had by opening the VVT’s at low load to reduce backpressure and reversion EGR.

Is the VVT the only way to control boost, or is there an electronic wastegate as well ?

Here is the real question on this subject – part throttle boost/fueling. What is the optimum between boost and fuel at part throttle for best economy, smoothness, and power – more boost and less fuel, or more fuel and less boost ?

Can anyone help fill in some of the blanks here ?
It's hard to get too much fuel in our trucks without upgrading the injectors and adding a second CP3 fuel pump. The main thing is to not inject it too early. Too much fuel too early causes cylinder wash from what I understand.

Here is a little thread on timing.

Pilot injection is a small injection pulse before the main injection pulse to help ignite the main injection action and cause less diesel rattle. It also helps with emissions.

The VVT was originally added to help with emissions. There is no wastegate with the VVT. Yes closing the vanes creates more boost. You are on the right track about back pressure and fuel mileage. Here is a link that explains why certain things help with mileage.


Extinct;1530285; said:
OK, with respect to the three boost tables, why does it make a hill of beans difference what the altitude is ? With a boosted engine, you can control the intake manifold pressure to be whatever you want it to be at all rpm/throttle openings - right ?
The air pressure (barometer reading) based boost tables are probably used for emissions. I personally haven't been above 5000ft with mine so I can't say whether these make any difference or not.

Here is another link for fun. Also check this link out.

Good questions BTW. I'm hoping to learn something from this also.
 

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Discussion Starter · #11 ·
OK, I have been thinking a lot more about this - in particular the theoretical best method of tuning this LBZ diesel. I did a little research on the subject as well, but I would like to share my thoughts with the community and see if anyone else can corroborate my thoughts and/or expand on or make corrections to them.

OK, here we go.

I've looked at the LBZ tables that EFILive has cracked for us and I think I understand the logic of the GM engineers.

1. First, it appears that we/you (the driver) determines the desired torque needed via pedal position, as there is a table that torque vs pedal position vs rpm (3d table). Therefore, it appears that the pcm looks at the rpm, the tps, and reads the desired torque.

2. The pcm takes the desired torque, and determines the required fuel, boost, and timing. Now, the question is what is the relationship between these.

Based on the limited amount of research I have done, it would appear that diesel engines are similar to gasoline in that there is an air/fuel ratio at which maximum torque and efficiency are produced - too much fuel, torque and efficiency go down, too little, torque and efficiency go down.

However, based on the limited amount of research I did, I could not determine if diesel engines were also similar to gasoline engines in whether these torque and efficiency optimums occur at the same ratio.

It is well known that gasoline engines produce these maximums at a ratio of around 12.7:1 and maximum fuel efficiency in the 14.7-16:1 range.

We need to determine what is the optimum ratios for diesel engines for our preferred conditions.

I am sure the general probably optimized these for a different set of conditions, namely including reliability and emissions, which probably changes things from where we want to be.

Timing has not been addressed, I will address that later.

3. Assuming this is correct, we can see that for any given rpm, the engine can deliver a certain optimum torque and/or efficiency, based on the air supplied and the matching optimum fuel ratio.

We don't have a throttle to control airflow on a diesel, however we do have a turbo which is capable adding airflow above the normally aspirated airflow.

So, for some minimal torque requirements at a selected rpm, we probably don't need any boost to deliver the airflow necessary to deliver the torque requested when matched with the correct ratio of airflow. This is why on some of Citi's tunes he gets better mileage by turning down the boost and opening up the vanes, because he is lessening the restriction in the exhaust and making the engine more efficient when operating in the NA range.

In fact, as some low torque requirements, when even optimum torque fueling with no boost provides too much torque, the fuel will need to be reduced to less than optimum torque just to reduce the torque supplied - hence the benefit of a six speed and tall gearing - lower torque via lower rpm and fueling is more BMEP (break mean efficient power) efficient.

Then, for larger torque requirements, more air is added via boost, and more fuel to match.

So, for best efficiency, we match fuel to air, providing boost when more torque is needed, and reducing boost (and exhaust restrictions) when not, and maybe even fuel.

4. Now, based on this theory, the boost tables would be based on torque, but they actually are based on fuel. The PCM apparently looks at the fuel requirement (based on torque desired), and supplies the boost to match. This is essentially the same as I have suggested, as they are matching air and fuel.

5. There is a vane position table, and I expected this to be based on torque desired, however this is based on fuel as well. I find this a little bizarre, as the vane position basically determines the boost created. So given this, I don't understand exactly why there is a boost table and a vane position table, not just one. However, I have a theory on this as well.

I believe the pcm must have a proportional-integral-derivative controller that controls boost. For this controller, the vane position would be the initial value used in the pid calculations, and the boost tables would be used for trim adjustments.

Can anyone shed any light on this ?

6. Fuel pressure - it seems GM adjust fuel pressure based on the amount of fuel required and rpm. Anyone have any idea why they would do this instead of running at maximum pressure all the time and just adjust the pulse width ?

7. Pulse width - obviously this table is used to determine the length of time necessary to achieve a given fuel volume needed per cycle.

8. Injection timing - now I think this works very similar to ignition timing for a gas engine, with there being an optimum for a given rpm and load (fuel, and boost). I really think the The optimum values can obviously be arrived at pretty easily for each point on the map with a little datalogging.

However, the pilot and post injection I am not sure about, does anyone have any theory about how to determine the optimum settings for these ?

I have read all the other post and understand the theory regarding using the pilot injection to initiate the flame front in a more controlled manner, as opposed to the more explosive combustion which results in the traditional diesel rattle. However I don't have a good idea about how to quickly further optimize the pilot timing, and not sure what the post injection is for and how to optimize it.

Again, looking for a little help here, if anyone would be willing to share their knowledge (hint, hint - pro-tuners out there).

I've got live and some experience tuning my LS1 (as well as a BS in Mech. Engineering, so I understand combustion theory pretty well), now I'm ready to start on my LBZ, I just want a little better information on how to go about it rather than just turning everything up to get more power. My goal is more power when I step on it and better efficiency when I don't.

Anyone else want to chime in here and we can work and learn together - keep improving on this thread ? Or maybe correct my theories where they are wrong ?

Jeez, nearly 100 views since I made the last post and no one has anything to say ???

Tell me I'm wrong, warn others not to believe me, ask me a question, add to what I've said !

Say something, the silence is deafening !

Here we have the premiere tuning tool in the world for the premier diesel engines in the world, and I can't seem to get a discussion going on the best way to use it other than adding boost and fuel ?

Surely there are other technically competent people out there who have no interest in becoming professional tuners and protecting their tuning secrets that would be willing to share their knowledge ?
 

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I am no expert, but i know how frustrating it is waiting for someone to reply to your post so here is what i think.:) and remember I have an old school truck.

Extinct;1570570; said:
OK, I have been thinking a lot more about this - in particular the theoretical best method of tuning this LBZ diesel. I did a little research on the subject as well, but I would like to share my thoughts with the community and see if anyone else can corroborate my thoughts and/or expand on or make corrections to them.

OK, here we go.

I've looked at the LBZ tables that EFILive has cracked for us and I think I understand the logic of the GM engineers.

1. First, it appears that we/you (the driver) determines the desired torque needed via pedal position, as there is a table that torque vs pedal position vs rpm (3d table). Therefore, it appears that the pcm looks at the rpm, the tps, and reads the desired torque.

Still trying to understand this one, and as i understand it the lbz is even different.

2. The pcm takes the desired torque, and determines the required fuel, boost, and timing. Now, the question is what is the relationship between these.

exactly...???

Based on the limited amount of research I have done, it would appear that diesel engines are similar to gasoline in that there is an air/fuel ratio at which maximum torque and efficiency are produced - too much fuel, torque and efficiency go down, too little, torque and efficiency go down.

However, based on the limited amount of research I did, I could not determine if diesel engines were also similar to gasoline engines in whether these torque and efficiency optimums occur at the same ratio.

It is well known that gasoline engines produce these maximums at a ratio of around 12.7:1 and maximum fuel efficiency in the 14.7-16:1 range.

We need to determine what is the optimum ratios for diesel engines for our preferred conditions.

I am sure the general probably optimized these for a different set of conditions, namely including reliability and emissions, which probably changes things from where we want to be.

Timing has not been addressed, I will address that later.

3. Assuming this is correct, we can see that for any given rpm, the engine can deliver a certain optimum torque and/or efficiency, based on the air supplied and the matching optimum fuel ratio.

We don't have a throttle to control airflow on a diesel, however we do have a turbo which is capable adding airflow above the normally aspirated airflow.

So, for some minimal torque requirements at a selected rpm, we probably don't need any boost to deliver the airflow necessary to deliver the torque requested when matched with the correct ratio of airflow. This is why on some of Citi's tunes he gets better mileage by turning down the boost and opening up the vanes, because he is lessening the restriction in the exhaust and making the engine more efficient when operating in the NA range.

In fact, as some low torque requirements, when even optimum torque fueling with no boost provides too much torque, the fuel will need to be reduced to less than optimum torque just to reduce the torque supplied - hence the benefit of a six speed and tall gearing - lower torque via lower rpm and fueling is more BMEP (break mean efficient power) efficient.

Then, for larger torque requirements, more air is added via boost, and more fuel to match.

So, for best efficiency, we match fuel to air, providing boost when more torque is needed, and reducing boost (and exhaust restrictions) when not, and maybe even fuel.

I don't have a VVT so ???

4. Now, based on this theory, the boost tables would be based on torque, but they actually are based on fuel. The PCM apparently looks at the fuel requirement (based on torque desired), and supplies the boost to match. This is essentially the same as I have suggested, as they are matching air and fuel.

5. There is a vane position table, and I expected this to be based on torque desired, however this is based on fuel as well. I find this a little bizarre, as the vane position basically determines the boost created. So given this, I don't understand exactly why there is a boost table and a vane position table, not just one. However, I have a theory on this as well.

I believe the pcm must have a proportional-integral-derivative controller that controls boost. For this controller, the vane position would be the initial value used in the pid calculations, and the boost tables would be used for trim adjustments.

Can anyone shed any light on this ?

6. Fuel pressure - it seems GM adjust fuel pressure based on the amount of fuel required and rpm. Anyone have any idea why they would do this instead of running at maximum pressure all the time and just adjust the pulse width ?

another good question???

7. Pulse width - obviously this table is used to determine the length of time necessary to achieve a given fuel volume needed per cycle.

8. Injection timing - now I think this works very similar to ignition timing for a gas engine, with there being an optimum for a given rpm and load (fuel, and boost). I really think the The optimum values can obviously be arrived at pretty easily for each point on the map with a little datalogging.

However, the pilot and post injection I am not sure about, does anyone have any theory about how to determine the optimum settings for these ?

citi1991 has posted and shared alot of information on both of these areas which have been put in a sticky.:D

I have read all the other post and understand the theory regarding using the pilot injection to initiate the flame front in a more controlled manner, as opposed to the more explosive combustion which results in the traditional diesel rattle. However I don't have a good idea about how to quickly further optimize the pilot timing, and not sure what the post injection is for and how to optimize it.

Again, looking for a little help here, if anyone would be willing to share their knowledge (hint, hint - pro-tuners out there).

Wow, ah, not sure what to say here without p*ssing somebody off, but it seems we are on our own unless you want to join the battle of you is bigger.....better..

I've got live and some experience tuning my LS1 (as well as a BS in Mech. Engineering, so I understand combustion theory pretty well), now I'm ready to start on my LBZ, I just want a little better information on how to go about it rather than just turning everything up to get more power. My goal is more power when I step on it and better efficiency when I don't.

Anyone else want to chime in here and we can work and learn together - keep improving on this thread ? Or maybe correct my theories where they are wrong ?
I have gotten a lot of help offered to me here, and appreciate it very much, but when i comes to understand why they made the changes they are recommending i have not been given much to go on. I do not know if WE are all just copy/pasting stuff that works, or WE actually know how/why and don't want to share????

CRICKET,,,,CRICKET,,,
 

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I'm just trying to learn something too so a good half-dozen or so of those views are from me checking up on the updates or next post. :D

Your questions are awesome and I really hope someone can and WILL answer them publicly. You seem to have a great understand of things and just need a little push or hint to 'get it'. Some of the things you've already picked up on I would have never noticed just from looking at tunes, logs and reading here. Its quite complicated IMO. Very fun to learn though.

Thanks for trying to get this going. Hopefully it will develop into a very useful thread for many to use.


C-ya
 

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Extinct;1530285; said:
OK, with respect to the three boost tables, why does it make a hill of beans difference what the altitude is ? With a boosted engine, you can control the intake manifold pressure to be whatever you want it to be at all rpm/throttle openings - right ?
Little info off topic I guess but at work our mine goes down to 7810 feet and still going down. We run cat scoops and originally when they came they wouldn't run worth a damn. Around 7200 feet the at pressure is 18.4 instead of the regular 14.4. The engines needed a new atmospheric pressure sensor that would run higher pressures. Just because the first sensor was wacky that sent the engine into a derate.
 

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Discussion Starter · #15 ·
06bowtie_guy;1573473; said:
Little info off topic I guess but at work our mine goes down to 7810 feet and still going down. We run cat scoops and originally when they came they wouldn't run worth a damn. Around 7200 feet the at pressure is 18.4 instead of the regular 14.4. The engines needed a new atmospheric pressure sensor that would run higher pressures. Just because the first sensor was wacky that sent the engine into a derate.
Holy crap, -7810 ft ? Where the hell do you work ? What kind of mine is that ? Bet my NA LS1 would make some serious power at that elevation !
 

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One thing you need to keep in mind is that the timing on a diesel engine does not quite compare to a gasser....as we are talking about the injected fuel vs. the spark to ignite the A/F mixture.
 

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Wow, no questions here are there? :D

Ok run down for LBZ from my playing and understanding of how it works...So take this for what you want. Also all my references will be with the tables converterd to imperial.

I guess we will start with Pedal position to desired torque B1115 table. Down the right side is throttle position in % across the top is rpm. In the center is the desired torque output. So the LBZ is rated at 650ft lb of torque at 1600 rpm, when looking at the the table you will see 664.

So lets take the 664 where does it come from and how does it add fuel based on this number?

Go to table B1102 Torque Based Fuel. Looking down the right side is the torque number from the B1115 throttle table. Across the top is rpm, the numbers in the center represent mm3 of fuel. So 664ftlbs at 1600 rpm requires 87.6 mm3 of fuel. Now with this table we can see how the mm3 is referenced.

Now before we get to one of the first tables that most people adjust for added power B0720 table we need to look at the B1001 Fuel pressure base table. Down the right side is mm3 and across the top is rpm, the center represents fuel pressure in MPa. Now things to look at from this table, what rpm and what fuel pressure corrispond to help in adjusting the B0720 table.

Ok, finally we can look at the B0720 table Main Injection Pulse. Down the right side is mm3 across the top is fuel pressure, in the center we have how long the injector is open to allow fuel in. From the previous tables, its now possible to understand what area is being adjusted to add/remove fuel.

Basically we have 3 tables that the amount of fuel entering the cylinder can be adjusted. Some work better, some fine tune better all stuff that is up to the one programming. Obviously the pump is only giong to make so much fuel pressure, but has some room to play. The mm3 is the amount of fuel being injected so can adjust that and the pulse is how long it has to get all that fuel in the cylinder.

Injection timing table, for us seems to be the B table B0909. Down the right side is mm3 and across the top is rpm, the center is crank degrees before and after top dead center of the piston and when the fuel will start to be injected.

Desired Boost tables, down the right is mm3 and across the top is rpm. The center is the boost level that we want. Now lets say the number is 37, well this really isnt 37psi per a gauge, this is with the addition of atmospheric pressure of 14.7psi. So if you want to know what the "gauge boost" would be, subtract 14.7 from the number.

VVT-Variable vane turbo. Really this is pretty simple, close the vanes, more exhaust pressure build up spins the turbo faster, less vane position less exhaust pressure to spin the turbo. Basically this acts like waste gate and allows for more control than a waste gate can. So at low rpm, when there is less exhaust, we can keep the vanes closed up, more rpm means more exhaust flow, so we need to open up the vanes and bleed some of the pressure off the turbo so we dont over speed or spin the turbo to fast and it comes apart. How many rpm the turbo spins equals how much or how little boost we make.

Why does the altitude matter? Because the air is thinner, need to spin the turbo faster to get the same psi (comression of actual air) to equal what it does at lower altitudes and come out with close to the same power output and emissions.


Now obviously there are other factors that come into play with all these tables such as coolant temp, air intake temp and such, but its the base of it all.
 

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I have not spent much time with the LBZ tables yet, but the scan tool and tune tool will link the tables correctly.

You can just go out and log the heck out of it and see what the tune is doing based on driving habits, cruising, WOT, starting from a stop, etc.

Once you have that data then you can look at it and understand what is really going on.

I'll be looking at the LBZ stuff soon as my brother has an LBZ, seems like GM was looking to make it more complicated.......:eek:

;)
 

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WOW guys, keep it going. I'm learning. Great idea Extinct. Things have surely changed from the LB7/LLY to the LBZ.

Cobra, my 07 stock tune tables B1115 and B1102 don't follow your example(not that that matters for learning purposes), maybe I'm not looking at the right spot. My B1115 @50% tps and 1600rpm = 658, and when going to B1102 and 650 my mm3 is 65.5

Thanks guys,
Rob
 

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Its possible that its different, I was just going off a stock program that was in the tune library, but hopefully people will get the general idea of what i ment :)
 
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