First attempt at tuning advice needed

[Buckeye79]

This is my first attempt at any type of tuning, working on the VE table and am wondering if someone would want to take a look and give me some advice. When I first started, I had STFT readings of 45-50 now, most appear on the negative side. Been going on 20-30 minute runs including highway and trying to stay under 3000 RPM, I have been copying the table from VCM and pasting into the VE using paste special>Multiply by % -half. I'm wondering if that is the right way to do it or if I should be looking at only specific cells that are still way out of range instead.

Car is a 79 Cutlass 5.3 l33 799 heads 02 Zo6 cam and 2001 truck intake with the stock 25317628 injectors and rail from same intake. The PCM is also from the same 2001 truck.

I appreciate any help. Thanks

[5FDP]

Something is wrong elsewhere if you started with trims at 45-50%, that is not a tuning issue.

There should never be values in your VE table over 100 like you have, you are working around an issue. Like a massive vacuum leak or incorrect fuel pressure. Those are two most popular issues on swap vehicles as well as exhaust leaks before the o2 sensors.

If you don't have 58psi of constant fuel pressure, you will have issues like this..

[Buckeye79]

So sounds like I need to try to find a vacuum leak. Fuel pressure is right at 58. One thing I do notice though is after it sits for a few minutes, I have to turn the key off and then back on a few times to get fuel back to the rail, seems to be bleeding off somewhere.

[horsepowerguru427]

So sounds like I need to try to find a vacuum leak. Fuel pressure is right at 58. One thing I do notice though is after it sits for a few minutes, I have to turn the key off and then back on a few times to get fuel back to the rail, seems to be bleeding off somewhere.

You either have an external leak, an injector(s) that is staying open or its bleeding pressure back into the tank through the pump. I usually dead head the pump into a pressure tester and watch what it does. After pressure is built up and the key is turned off it should hold residual pressure. If it bleeds off fast or to a low number with the pump dead headed then you need a new pump. If it does not, do an injector balance test to eliminate or pinpoint which injectors are bleeding down.

[Buckeye79]

You either have an external leak, an injector(s) that is staying open or its bleeding pressure back into the tank through the pump. I usually dead head the pump into a pressure tester and watch what it does. After pressure is built up and the key is turned off it should hold residual pressure. If it bleeds off fast or to a low number with the pump dead headed then you need a new pump. If it does not, do an injector balance test to eliminate or pinpoint which injectors are bleeding down.

Good idea, I should be able to pull the feed line off at the rail to check this. Thanks

[Buckeye79]

Anyone know where I can find the injector data for the 25317628 injectors? I have been trying to find that info with no luck. I just wanted to verify the current tune to make sure that matches. I had several intakes and I'm 90% sure I used the correct one but knowing my luck I wouldn't be surprised if it wasn't. If they were the wrong ones, could that lead to the high VE numbers?

[bk2life]

Anyone know where I can find the injector data

yes, you use the search bar at the top.

https://forum.hptuners.com/showthrea...ata-Repository

[Buckeye79]

yes, you use the search bar at the top.

https://forum.hptuners.com/showthrea...ata-Repository

Funny guy ... I know how to use the search function. That post and the spreadsheet only list the gen 4 injectors. It mentioned mine in one post but unless I was 100% sure exactly what they were from, how would I know which file to get from the repository? To my knowledge, the tune itself doesn't mention the injector part numbers only the flow data. Am I missing something?

[blindsquirrel]

If the PCM cane from the same truck as the intake and fuel rail and regulator and injectors, why would you need to be messing with injector data at all?

The reference to use for OE GM Gen 3 injector data in a Gen 3 PCM is whatever stock Gen 3 file came with those injectors.

[Buckeye79]

If the PCM cane from the same truck as the intake and fuel rail and regulator and injectors, why would you need to be messing with injector data at all?

The reference to use for OE GM Gen 3 injector data in a Gen 3 PCM is whatever stock Gen 3 file came with those injectors.

Right I understand that much. What I am not 100% sure of is if the injectors were the ones from the stock file I have. I had multiple PCM's as well as intakes at the time we started the swap. Would I be better off just swapping to a known injector and use the data from them since there is apparently no real way to make sure the tune matches? Thanks

[blindsquirrel]

That injector number is what came stock in a 2001 LM7, is it not? It's an old number that GM no longer lists but The Intarwebs still remembers it, says it's the same 25lb'er that all those trucks came with, and all the injector data in your file is unchanged from stock 2001 LM7, so what are we even talking about here?

[horsepowerguru427]

That injector number is what came stock in a 2001 LM7, is it not? It's an old number that GM no longer lists but The Intarwebs still remembers it, says it's the same 25lb'er that all those trucks came with, and all the injector data in your file is unchanged from stock 2001 LM7, so what are we even talking about here?

I guess if he changed his fuel system to a 4 bar (58psi) instead of 3 bar that came stock in 2001 then his injector data would need to be changed? Thats the only reason i can think that the data would be wrong for those injectors, which he did mention he had "58psi of fuel pressure" in Post #3.

[blindsquirrel]

screenshot.17-05-2024 18.57.42.png

[Buckeye79]

Finally had a chance to get back to this the car does not seem to have a vacuum leak, tried starting fluid as well as propane around the intake with no noticeable rpm or stft change. Vacuum measured at the booster port is around 16-18. With fuel gauge attached directly to the feed line at the intake, pressure is just over 85, turn the key off, it doesn't drop much. Fuel gauge hooked to port with key on, just over 58, when key is off, it drops fairly quickly. I'm guessing there is an issue with the injectors? Oil also has a slight fuel smell. Should I replace the injectors? If so should I be looking for somewhat of an upgrade?

[ns158sl]

85 psi after heatsoaked? im not following why the pressure is 85 vs 58psi? You said feed line vs at the rail. It is going to be the same pressure at the pump vs the rail, well maybe a half psi unless there is a restriction somewhere else.

[SiriusC1024]

Get a new reg.

[blindsquirrel]

With fuel gauge attached directly to the feed line at the intake, pressure is just over 85

If you mean you disconnected the feed line from the rail (and therefore the regulator), and put the gauge in the end of the feed line, and ran the pump deadheaded against the gauge, that does not tell you anything useful. That's not the pressure the injectors will see.

Fuel-in-oil will make it impossible to tune, the vapors coming thru the PCV will act like an EVAP purge stuck open.

[Buckeye79]

If you mean you disconnected the feed line from the rail (and therefore the regulator), and put the gauge in the end of the feed line, and ran the pump deadheaded against the gauge, that does not tell you anything useful. That's not the pressure the injectors will see.

Fuel-in-oil will make it impossible to tune, the vapors coming thru the PCV will act like an EVAP purge stuck open.

I'm going to swap the injectors and rail with a known good setup from a running lm7 I just pulled, see if that takes care of the fuel in oil issue. Obviously a fresh oil change is also in order.

85 psi after heatsoaked? im not following why the pressure is 85 vs 58psi? You said feed line vs at the rail. It is going to be the same pressure at the pump vs the rail, well maybe a half psi unless there is a restriction somewhere else.

Checked pressure right at feed line, removed from rail. It was suggested earlier to dead head the pump. So no regulator involved when getting 85.