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How to get 120mm^3 of fuel out of a DS4

43K views 128 replies 25 participants last post by  alex1234 
#1 ·
Any one have any ideas on how to get a DS4 pump to 120mm output on fuel? I just bought the engine that sctrailrider built and need a ds4 that can fuel it.
 
#3 ·
Not sure if any have gotten above 104-105mm^3 out of a DS4. Hopefully, if it is done, this will be something shared with the masses...LOL. Tom might also have some ideas. Do not recall any, after having a tune done (by whomever), also flow tested the pump and posted up the resulting flow chart or the values@ rpms.....
 
#4 ·
I talked to Bill Heath today about his merlin ds4 pump, he claims with his special merlin ecm tune with that pump, that it will far out perform the db2. He says with that and the cam he sells, and that the way the engine is currently built that he could get me at 400 to 420 hp. I dont know, sounds awfull optimistic to me, as we all know that 400 horse mark with the 6.5 is hard to reach.
 
#5 ·
A few have claimed to have obtained 400hp at the crank. For us however, there has only been two 6.2/6.5L trucks to break 300hp at the wheels (John and Ian). Would need to be in excess of 25% powertrain losses (not unreasonable), to be 400 plus horsepower at the crank. People can claim all they would like to, but until actual hard data is shown, it is just hypothetical......
 
#8 · (Edited)
do a mechanical swap to a DB4 built by R&D performance...

buy one like this, he is building them for gm diesels as well.....
 

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#9 ·
I'm not going to start anything here, it's a free country for the time being...

but I never cared to just accept what is said without SOMETHING that sort of looks like facts or proof of someones claim... to this day I haven't seen anything close to that from the seller mentioned... I will admit I don't purchase from that company as I have found a seller that can back up his claims and I have always received what was promised and I didn't half to purchase a load of other things just to improve what I had...

and if needed I can post the numbers for the db2 I have for the new motor that john also built... it also puts out quite a bit of fuel by the number sheet...
 
#11 ·
I agree with what all of you are saying, claims and dyno reports are two different things. I would like to keep the ds4 though, so some research and calling around to a few people are in order.
 
#12 ·
contact member greatwhite, he bought tunercat and played with it alot, word is he(or someone he knows) broke the code that gm wrote to stop the pump from going higher.....
 
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#15 ·
With the programming, you can easily tell it to squirt about 120mm^3 per injection, by some math analysis, but I don't know what the OBD2 programming capabilities are, and I have never verified its pushing as much as the numbers would suggest.

The displacement of the DS4 makes it capable, especially if you increase the cam travel, and its probably easier to fill 4 plungers than 2.
 
#16 · (Edited)
On the DS4 test stand you can set (request)the fuel to any desired amount up to 99 mm/3.

Typically the IP will only put put out about 82mm/3 max.

I have slightly altered the internals of the IP and with a little tweaking got 102mm/3.

However I never applied it to a vehicle as I am quite sure the vehicle performance would have been sub par for a daily driver. Being electronic I am not sure how the vehicle would have responded without extensive reprograming to the specific vehicle.

So from what I gather even the most extreme programing can only get you so much fuel. After that the IP needs some real attention to get higher levels of performance.

Try finding that on the internet.
 
#17 ·
So does that mean when you set the test stand to 80mm^3 that is puts out 80mm^3, but when you set it to 99mm^3 it still only puts out 82mm^3? Or is it a sliding scale, that when you set it to 80mm^3 it only outputs 70mm^3?

Just wondering if there is a difference between a PCM and PMD pulse width setting and the test stand.
 
#19 ·
80 to 82 is pretty much the max. The pump tends to fall off after 75 is requested.

As a a side note the 5068 pump does put out slightly more, and that is due to the cam ring having just a small amount more lift. Think about .004" more. If memory serves me I think it could put out 86-88 max.

Keep in mind these pumps were set with the optic sensor in the optimum max side of spec. A stock set pump could very well put out even less than what I have listed. So results can very a wee bit.
 
#18 ·
FWIW I have Bill's tune in my truck, and it seems to be lacking fuel on the top end, acceleration is sluggish past 60mph. I emailed him asking if its possible to add more fuel to the top end, and he said the tune I have is set for 80mm fuel, which he claims is the same amount as his LSR truck. I was always under the impression that the pump is physically limited to 80mm, but if its just a matter of coding and software..... :)
 
#21 ·
sorry hugh, but i need to laugh @ bill heath....:hehe::hehe:.... there is no way,(if he did indeed tell you his tune in the LSR is the same as yours) that his outlandish claims of 500hp with that truck can be fueled by only 80mm of fuel.... sounds more to me that its just another claim/pitch to sell pieces.... and the pitches are starting to over-lap and sound ridiculous........:hehe::hehe::hehe:
 
#23 ·
I was after that mythical 120mm3 once too. Was lead to believe it could be done. Paid for my "race" tune and matched it with the turbo that was being pushed with the tune and whala......I had a truck that was putting out no more fuel than any of my other tuned ds4 trucks ever did. After some talking with the people that had me believe the 120mm3 was possible, I found out that was merely a theoretical number based off of calculations of what the pump could flow, but was then told the programming couldn't be commanded to put out that much fuel. Face plant for me for not being more specific with my questions on my 120mm3 quest.

Talked to the tuner and he said he estimated that I was putting out in the 105mm3 range. Long story short, I swapped a worn out marine db2 pump onto the truck and it had more low end and mid range power than the ds4 and dropped off slightly at the top end. When it was rebuild I found out, if I remember right, that it was only putting out somewhere in the 80s cc of fuel at 3500 rpm. Comparing how it ran vs the "race" ds4, I would say the ds4 might have been putting out slightly more fuel at 3500 rpm, but only slightly, and nowhere near the theorized 100+mm3.

Stick wth mechanical if you want the fuel to match the engine. Until Heath can give you flow numbers of his pump, I would highly doubt it puts out that much fuel. At one point, he claimed his power package with that pump and his modified GM8 turbo would get you 425hp. So your far better turbo and engine should surpass that with his pump...... If it actually supplied the fuel needed to reach that hp....

And hello to all. First post here, but have been member 3500_6.5 on another page. I think most here will know me from there, but for those who aren't on that page, hello!! Looking forward to meeting and discussing with all of you!
 
#24 ·
Welcome aboard.. Take a minute to click on "User CP" in the upper right hand corner
then click on "Edit Signature" and enter in your vehicle information and any known mods to your truck. That will help to be able to help you, answering any questions you may have...
 
#27 ·
Just got on my laptop. On here, it shows my sig on the second post, but not the first. Hopefully all will be able to see it now!
 
#31 ·
As has been stated over a decade ago, the DS4 in theory can put out 120MM3 of fuel due to plunger and lift travel. The problem is theory and reality rarely agree. Realistic numbers are more or less for a healthy pump i nthe low 90's for actual output through a test orifice, and could actually be lower depending on how much fuel the injector returns. The highest output pump built IIRC was canadian riggers WAY back in the day which was a 5068/5521 hybrid pump, and it put out at the inejctor an actual 94-96MM3 of fuel. So you can call for it to fuel X amount all day long, don't mean you will get it. I know somebody else recently tried forcing one to over fuel on a test stand, and the most he could get out of a freshly rebuilt bone stock 5521 was 96Mm3 of fuel through a test orifice. Never heard back on his results through an actaul injector or a marine nozzle.
 
#33 ·
I'm a little late to the party but i'm wondering the same thing Tom hinted at earlier. The test stand can adjust the quantity of fuel requested but can it adjust other factors that can be adjusted in the PCM tune or are they static?

For example, I have an old tune here that doesn't raise the fueling paramaters but by changing the pulse at part throttle, you can make the pump deliver more fuel than it thinks and the truck is much more agressive because it's using the same shift points while fueling the equivalent of 75% throttle with only 50% commanded by the driver (example data)

The only way to figure this out is to know what inputs are being given to the pump from the test stand (and if they match the limits of the PCM outputs) I suppose
 
#34 ·
The test stand isn't held to the constraints that the ECM is held to. There are people out there who can request full FSOL travel, but it still will not give you the theoretical 120MM3 of fuel. You can go out and build your own fuel controller as the technology is available to do so, but you are still only going to get X amount of fuel from the pump which is what several others have stated they can get from it on a test stand. The test stand doesn't care about ECm programming, it can tell you what the pump can do, thats that.
 
#35 · (Edited)
The question is more along the lines has anyone verified the test stand is telling the truth when you request a higher volume that it increases the pulse width appropriately. Like with an oscilloscope and measured an increase in pulse width to show the controller is actually programmed to go past GM's desired maximum. I'm not saying it does or the pump can, just a question as to the level of verification.

I can attest to more coming out of the pump, unmeasured, when increasing the pulse width in the PCM, than just using GM's mapping and maxing the fuel request at 80mm^3. The more is noticeable by more smoke at full throttle and being able to drive more boost.
 
#36 ·
Are you asking if anybody has verified if the ECM is actually telling the pump to go to full fueling beyond what the ECM is capped at from the factory? If so I'm not aware of anybody who has rigged up a GM ECM to a test stand to verify the actual output. As you have pointed out we know the DS4 can put out more than what GM has capped the software at in the ECM, but how the ECM can command is unknown as far as I know. On a test stand they use a different controller to control the pump than an ECM, and as far as I know it doesn't have the constraints of the GM software to hold it back. Would be interesting to compare an altered GM ECM on a test stand to see what it is doing, and if timing or such changes when you go beyond the origanal GM limitations in the software.

Heres a pic of the STANADYNE tester that they use on a test stand to check the DS4 pump.
 

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#38 ·
I was actually thinking perhaps that Stanadyne and GM in cahoots may have decided to limit the output pulse width of the test stand, to limit the pump output to 80mm^3, even though it tells you that you are requesting up to 99mm^3. Perhaps they thought it could be damaging to go beyond, so they limited the duration (not travel) of the fuel solenoid closure.
 
#39 ·
Not likely. Stanadyne had high hopes of selling lots of these pumps to other makers which would of course used this same machine for other applications. When the pump is modified the IP will put out more and very close to what is demanded.

Unfortunately Stanadyne had a very high failure rate on GM products and the other makers saw the IP as junk. Nobody took them up on the DS pump so the DS pump ceased to remain in production.

I remember in 95-96 sending back to the factory 50-75 pumps at a time on a pallet. Stanadyne at one time supplied new pumps in exchange for bad warranty pumps. They didn't even want the repair shops to fix them under warranty. Warranties made a lot of fuel shops very wealthy which is quite remarkable since warranties paid so little.

I know cus I was there.
 
#40 ·
This is now going where I was thinking as far as rigging up an ECM to the test stand. I should have an OBD-I PCM I can donate to the cause but don't have a set of pigtails or a harness to modify.
 
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#45 ·
see above post, test bench is on its way....:coolnana:
 
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#41 · (Edited)
Rigging a PCM just to the DS4 may be difficult, in so much as making it happy by providing a CPS signal for timing and RPM. Although maybe we could change parameters in the PCM code so backup fuel mode, running on the OS alone, does not hurt its output capability. Not sure if I have enough code defined to adjust backup fuel mode.
 
#44 ·
I have a complete 94 and 95 harness and other stuff i'd get rid of for the cause.
test bench is past winnipeg now guys....:thumb:
 
#42 ·
I have a complete 94 and 95 harness and other stuff i'd get rid of for the cause.
 
#48 ·
This is going to be fun :popcorn:
 
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#49 · (Edited)
i wonder if a DS4 had .330" or .350" plungers( if this is even possible) would it help it get more fuel? the computer would be saying one thing, but the IP doing something different?
 
#50 · (Edited)
If you put in bigger plungers then it should output more, the computer's fuel mapping would just be incorrect, and could be corrected with some testing on the stand, just so the value someone programs in means what it says. Otherwise if not changing the mapping, a programmer could just adjust the definition scale factor for fueling to get it close. So right now there is a fuel table to request a certain fuel rate, but that just feeds into another couple tables of requested fuel rate = this much pulse width, but defined in like degrees of rotation. Then there is a requested fuel rate vs RPM table for some adjustment based on RPM and the changing transfer pressure or other pumping dynamics with relation to speed.

So basically, with larger plungers, when commanding 80mm^3 it puts out the same duration of squirt, but would displace more fuel.
 
#51 ·
I am currently playing with the tune and the westers garage definition file for obd1 and i talked a lot with Lyndon there. We have the same conclusion : the code is actually preventing the pump to get it to fuel more.

The DS4 is capable of more than what we think but is constrained by the code but also because it works with rotation of the engine to pump/inject. We could probably patch the code to get it to inject more fuel but it would probably affect the angle where it begins to inject hence playing on the "timing" and duration of pulse width which is not always something that is suitable versus a certain RPM.

That said, the best mod would definitly be a mechanical one that could allow to up scale the quantity of fuel injected for the same duration of pulse width. Don't know if the plungers are the good thing we have to have in mind but at first sight it looks logical to me if i understand well how the pump works.

Anyone know if this is what the Heath merlin SHO pump has as mod?:think:

94C1500 you refer to some requested fuel map that feeds into another pulse width angle map and these, I have a understanding of them. But the other map you talk about some other adjustment base on rpm x requested fuel, do you know what it is? Can you explain a bit I am kind of confused about what it does?

Thank you
 
#52 ·
I've been playing with some of the same stuff. Do you have a chip emulator on your truck or even able to do RT tuning with that definition? I know 94C1500 and I have our own files created from an independent disassembly and there are some critical parameters you may be missing. You'll run into hitting different max/min values that you won't realize until you are emulating on a truck.

Do you have a disassembly and the ability to recompile code from changes? This goes past the basics of tweaking what GM put there for us.
 
#57 ·
I played with a DS4 to see what I could make the thing put out. It topped out at 102cc's.

The max setting is totally unusable without a drastic resetting of the ECM. And then it would still run like crap due to the mods made.

The max a stock pump will put out is only about 82 cc's. So no matter what you do to the programming that's the max you can get. I keep saying this here but people keep on insisting they can make it do better. It just ain't going to happen without mechanical mods to the pump. 75cc's is about all you can get before drivability goes to crap. That's about as far as the pump can handle.

DS4 pump was designed before low sulfur fuel came out. DS4 pumps like clean real diesel fuel. DS4 was never capable of high output. Just the way they made it.
 
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#58 ·
What did you do to the pump to get 102cc's? The interpretation I have from your statement above, it must have been mechanical, tell the guys in the thread.....We My brother Jeff and I) are not sure yet of what the actual output (yep, in our old dinosaur test stand) is of the DS4. We have a few more DS4's coming our way, and will test with stock ECM and any other programs/chips you guys like. From talking with Fred, he seems to figure that the old test stands do not lie, due to what is in the calibrated tube is what was pumped.....LOL. A conservative calibration for a DB4 is 118cc's, so there should be at least that physically available from a DS4's H&R, more if bored out (this should always include any fill and spill passages). We have tried various means of getting more fueling (thus far only mechanically), and with fueling changes, proper air/fuel ratios need to be maintained, and if fueling is increased to above 90cc's, these motors will need to have mechanical modifications made, to have any reliability whatsoever.....J&J.
 
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