New to the forum, signed up to get some insight from other j-bodys who have already "been-there". I work for a performance shop and do the EFI tuning, albeit mostly V8 stuff and largely Mustangs. A customer has brought us a 1997 Cavalier Z24 with the LD9 2.4. Customer claims there is a Walbro 255 in tank, we installed Accel 62lb/hr "skinnies" (hi-impedance). We spent a considerable amount of time putting together a custom turbo setup for his built engine, with the "snail" in question being a Garrett (GT32). We have thus far used HPTuners software to tune it, but I am running into something here and have tried as much as I can think of but it keeps going lean as boost comes on. It begins to make boost about 2600 (here I can get 10AFR if I want) and makes 12+psi by 4K (aproaching 13AFR here). I set up the injector constant first...and it seemed to idle and cruise well on the rollers off boost. I have tried the following . Setting up the PE commanded to 11AFR, with no PE multiplier for RPM. That was BAD...mid 3K rpm it was stone lean. Added to the miltiplier so that it was as much as .6, not really any different. Put the customer's supplied Vortech FMU on, and put multipliers back. Only miniscule change...even asked for 9AFR in PE commanded...best so far was 12.8 AFR by 4700. Not acceptable. Performed a fuel pressure check, to find that if we crimp the return line right off, we get 75-78 psi. Hmmm. During a boost pull, we see just over 70. My trouble is I can't get HPTuners to log this car, no sensors are showing up, so I can't see injector duty cycle, but my line of thought is with 70psi fuel pressure and 62lb injectors, we aught to have a pile of fuel. What might we be up aginst I wonder? Thoughts?

Just thought I restate that the injectors are high impedence....I had not previously mixed and matched injectors, from hi or lo impedence (I know you can't put low in for Hi) and I wondered if it were possible the injector driver can't hold the injector open for lack of current since this has the lo impedence ECU. Anyone run into problems running hi impedence units on 98 and earlier cars?

It really sound like a fuel problem is with the amount of fuel getting to the injectors and regulator first, not with your software I would double check a few things first.

Inspect the fuel filter and see if it rated to flow the required amount of fuel and the given pressure you need, alot of people just install a new oem filter thinking that a clean filter will do. But
if the filter wont move tthe amount fast enough then at low pulls and idle you will keep the fuel level good but then that pump kicks in as the fuel is spent and the filter just can't keep up.

Check the voltage rates of the fuel pump while at idle and under load maybe you are getting a drop off from all the electrical and ignition systems.

I would also check to see if you are having a issue with the airflow sensors, some pre-98's are not equipped with units that can read the boost your giving it, so once you reach a certain point it can't read the
extra air and only gives what it thinks it needs at that max point. I bet your turbo is spooling up at about 2KRPMS and thats why you are running lean around 3KRPMS, so even if you were to add the fuel points it still tell your Tuner the engine is only getting X amount of air.

Let me know what happens next!



http//www.umods.org/drift.html
umods@live.com/ddiaz@umods.org

Could be a couple of things. It could be that the feed lines or wiring to pump may not be keeping up. Sounds basic/silly, but I ran into this on a few separate occasions. Also, the PE Command is not like others (LSx/LSJ/LNF) PCMs. With the J body PCM, all it does is provide a target area, it won' t automatically try to target it. How much VE tuning have you done on it? This could be the issue itself. You also said you are having issues with logging the car. You will need to make your own config file as the LSx config file will not work. I have a somewhat generic one I use on the J body platform I could send you when I get home. As for the injectors, usually is not a problem, but there is always a first. Is there a reason you did not just stick with low impedence?

Let me know if you need me to send you the config file..







P&P Tuning
420.5whp / 359.8wtq

I actually was pretty adamant to the other techs at the shop that I felt the issue was with fuel supply, but one point they kept reminding me of that I can't dispute was that we kept a steady 70+psi fuel pressure while the AFR drifted lean. This kinda rules out pump, wiring to it, the filter and all doesn't it? If it were a supply problem, the pressure should tail off. As for the MAP sensor not seeing above 100Kpa...well the MAP sensor isn't really in the picture in an Alpha-N strategy at WOT anyway AND you should still be able to smash the last line in the table and get the fuel. Trouble is this: The VE table can only have a max value of 110, which I put in from say 43% TPS and above from 2600RPM and up in ALL tables. I can't get more there, the PE I understand is what you target, and you tune the VE to get it....this is not new to me. BUT if you overcompensate with the PE, the PE multiplier and have an FMU to raise pressure on the mechanical side completely seperate from the ECU and STILL can get enough....I begin to think were missing something entirely. After reading last night, I am apt to try an experiment to see if the high impedance squirters are the culprit. Aparently, the low impedance "peak and hold" driver needs to see a given spike of current (4-6amps) to switch into hold mode (1 amp). With the increased electrical resistance of the new injectors (13.9ohms compared to 2.4ohms) I wonder if maybe the driver never hits the required current to go into hold mode so the pulsewidth doesn't widen, and if it does reach hold mode, maybe it isn't enough current to hold it for long. A saturated high impedance injector only requires 1 amp, but if this ECU provides 1 amp in hold mode through a 2.4ohm injector, maybe it can't even hold open the new injectors with more resistance. I wonder if its worth trying the stock injectors with the FMU and trying to see if it gets us any more control on fuel....if it does, get lo impedance 550 or 650ccs. I keep going back to this, people are on here with stock injectors and FMU and no tuning and holding 10psi, no? Surely I should get further even if just testing than we did. (175whp@4kRPM, 220wtq@3K with not enough fuel and 10-12 degrees timing for safety during the testing) I WILL TAKE CONFIGS AND ANY HISTOGRAMS YOU HAVE QWK LN2!! Thanks for reading, we gotta beat this.

BTW, this same car last year had a blower (Vortech I think?) on it at 7psi with stock injectors and this same FMU, same pump, stock ECU and ran well for a year according to customer.

Chris,

Email me a copy of the file and a good number to reach you. My email is pnptuning@gmail.com .. I would not mind taking a look and seeing if I can spot something you may be overlooking... I will also reply to it with the proper config file.







P&P Tuning
420.5whp / 359.8wtq

AN UPDATE...
I went at it again today with the stock lo impedance injectors back in it with the FMU still in place to see what if any changes we would get. The idle quality sure is better and the tip out/coast down when you declutch is far better...it would almost stall on declutch with the hi impedance 60's. Once under power it almost mirrored the AFR line on the graph until 3K RPM, and it got leaner...I aborted at 3500. This turbo (GT32) spools ALOT quicker than I would have expected. We had 14psi by 3400 RPM! We definitely wanted less...and it will make more. I found out it might have a 20psi actuator on it...so we are in the process of getting a 6psi can, and we can always put a boost controller on it to get it back up a bit. Lets get through 1 run on boost shall we? After all this I wondered something. Is there a hard limit of some kind in the JBody ECU of this era (1997)? Like some kind of airflow limit (I have seen this in many MAF ECU's) or a max pulse width??? I STILL CAN'T GET HPTuners to log on this car!!!!!!!! I only see battery voltage...that's it. It flashes fine.....my dyno has OBDII input, and it sees RPM and no more. Then I plugged in our Snapon scanner, and it sees pretty much everything.....i did a couple blips to see what pulsewidth I got and the most I saw was 9.9ms at about 3K RPM (maybe 10psi?) We are about to set the thing up on the 6psi...if it can get through the range decently, it may have to stay like that until a standalone or piggyback gets installed. Too bad it wasn't a 2000+ model year, LOL.

Did you use the config I sent you? I know it works......



P&P Tuning
420.5whp / 359.8wtq

Chris Nugteren wrote:AN UPDATE...
I went at it again today with the stock lo impedance injectors back in it with the FMU still in place to see what if any changes we would get. The idle quality sure is better and the tip out/coast down when you declutch is far better...it would almost stall on declutch with the hi impedance 60's. Once under power it almost mirrored the AFR line on the graph until 3K RPM, and it got leaner...I aborted at 3500. This turbo (GT32) spools ALOT quicker than I would have expected. We had 14psi by 3400 RPM! We definitely wanted less...and it will make more. I found out it might have a 20psi actuator on it...so we are in the process of getting a 6psi can, and we can always put a boost controller on it to get it back up a bit. Lets get through 1 run on boost shall we? After all this I wondered something. Is there a hard limit of some kind in the JBody ECU of this era (1997)? Like some kind of airflow limit (I have seen this in many MAF ECU's) or a max pulse width??? I STILL CAN'T GET HPTuners to log on this car!!!!!!!! I only see battery voltage...that's it. It flashes fine.....my dyno has OBDII input, and it sees RPM and no more. Then I plugged in our Snapon scanner, and it sees pretty much everything.....i did a couple blips to see what pulsewidth I got and the most I saw was 9.9ms at about 3K RPM (maybe 10psi?) We are about to set the thing up on the 6psi...if it can get through the range decently, it may have to stay like that until a standalone or piggyback gets installed. Too bad it wasn't a 2000+ model year, LOL.

I bought a GT2860RS and it came stock with a 20 psi internate wastegate actuator too. It would barely crack open at 15 psi in my static testing. I had to order a 6 psi gate and have a Hallmann MBC so I can run 13 psi+ as planned. Found the internal gate at FR sport - a little pricey but it was all I could find that would directly fit given my search criteria.

Edited 1 time(s). Last edited Thursday, February 18, 2010 7:22 PM

It should not be hard to get the scanner to read. A default HPT config should work. Most Jbody ECU's do not even read boost, so no limit. It is possible this car uses map for fueling, but most do not. Even if it does use map for fueling, no limit on how much air the car will take, just a limit on the fields to adjust. Sounds like you need a proper set of low impedence injectors for this car, that are bigger than stock.



FU Tuning

QWK LN2, yup...I used the config. It looked good, nice work on it, but no go. Not sure what to attribute it to. I tried the default as well and no change. I was thinking an issue with the DLC connector or harness but then the Snapon scanner worked. I am not a noob with HPT by any means, I have tuned dozens of FBodys,Vettes and trucks etc (and even one 3.4L turbo GA) and it always worked. No idea whats up with it. I only asked about a hard limit in the ECU cuz I know for example a Denali I tuned had a hard limit of 512g/s airflow limit regardless of MAF used (ECU will not register any more)...we may not see it in the software and not many have probably pushed this early ECU to a point where it would be found...it was just thinking out loud, thats all. I hate to say this, and not looking to get flamed, but this 97 ECU is really the limit to the whole project...its not very flexible but I guess you all knew that already. And the actuator I looked at was at ATP Turbo...lists for $60. I agree, the best answer is the lo impedance 60's. We may end up there. Thanks for the input. Stay tuned.

Chris Nugteren wrote: Stay tuned.

Don't worry, I'm always tuned! . Too bad I am not closer, I would love to come by and help you get this b!tch done.





P&P Tuning
420.5whp / 359.8wtq

still on this one, waiting on a lower rated wastegate actuator...no major breakthrough. Anyone know for certain if this VCM can accept the GM SC reflash even though it is a 97? I heard it will lose guages etc, BUT will the flash take, could it be tuned with the associated MAP sensor, or does it only work on later VCMs?? Just wondering. Another question for you. Since VE offset can't really give us a huge amount to play with here...would faking the injector constant and rescaling the VE tables get me anywhere? Example: the constant for stock is .202 or something...what if you used .250 or higher. It would idle and run rich at cruise, but you can take it OUT with VE tuning. Wouldn't that net more at WOT? The constants are just for example...but the principal is what I am questioning. Any ideas?

I do not know if anyone has tried the GM reflash on a 97. I know on a 99 you lose gauges, but it works.

What is your VE offset at currently?

GM did what your talking about with faking the injectors constant on the Reflash. I donlt like it.

I would get low impedence injectors and control the boost and you should get the results you need with the FMU and HPT.



FU Tuning

I never actually flashed a calibration to the ECU that had the offset altered. The reason for this is I sat and messed with it some just in the software and I quickly realized you wouldn't get that much using it. I think there are spots in the orig VE table that are like values of 10 or 14 or something....they are in spots you might never see so that wouldn't hurt you much. At cruise and idle...since I don't have the laptop here for the weekend...anyone recall the lowest VE values? Ones that are going to be hit frequently. This would be the highest offset you could use. Say the number was 35, then the lowest number ANYWHERE in the table could be 35 and you could then get a max VE of 135% but there would be some low throttle stuff that might get over fuelled. Now I guess you could rely on trims to take this out if it necessary...not proper, but under the circumstances. Perhaps with a bit of this and a bit of the "fake" inj constant we can get it done. How many psi of boost you can get by with this is the question.

Chris Nugteren wrote:I never actually flashed a calibration to the ECU that had the offset altered. The reason for this is I sat and messed with it some just in the software and I quickly realized you wouldn't get that much using it. I think there are spots in the orig VE table that are like values of 10 or 14 or something....they are in spots you might never see so that wouldn't hurt you much. At cruise and idle...since I don't have the laptop here for the weekend...anyone recall the lowest VE values? Ones that are going to be hit frequently. This would be the highest offset you could use. Say the number was 35, then the lowest number ANYWHERE in the table could be 35 and you could then get a max VE of 135% but there would be some low throttle stuff that might get over fuelled. Now I guess you could rely on trims to take this out if it necessary...not proper, but under the circumstances. Perhaps with a bit of this and a bit of the "fake" inj constant we can get it done. How many psi of boost you can get by with this is the question.

YOu can raise the VEE offset. I have mine at 100% and no issues. You can play with the injector constant and be able to keep it lower (what GM did), but it will make your injectors look maxed out.

In normaly driving the ECU controls the AFR's and will keep it in the 14:7:1 range. With running a FMU you should not need the raise the offset much and still be fine.



FU Tuning

UPDATE:
New actuator installed, boost rises to 7psi by 3800-4K and the wastegate has trouble holding a steady line( I guess because this turbo wants to flow so much) and it creeps, up to 8.7psi by 5500. Oddly enough it spools slower now too. With stock injectors, and a VE offset of 30% and some injector constant tuning, I got this car up to 5500RPM and 200whp/203wtq. Then the dreaded lean condition returned. Too bad cuz the graph was still climbing steep! There is a bit of room for spark tuning to get more power, but not much point if we can't get the whole RPM range covered. AFR flirted around 12.0 which is enough I think for this low boost tune. This car has the engine, turbo and pretty much the supporting mods to make good power, but I feel so hampered by the ECU. One could easily throw in some low impedance injectors and get more from this, but I honestly feel it would be better served having a standalone. Is there much in the way of install and wiring info for these cars for Megasquirt? I think the cost of this build thus far dictates the solution would need to be budget friendly if it were done in the short term, but have the flexibility to do it right. (or drive it as is and wait to spend big bux later) I have tuned a handful of different types of standalones, but not megasquirt...any info on this from those who have it?

I have tuned a 2.4 to make 266 whp on 15 psi (motor was bone stockthe stock ECU can handle the setup on this car. internally).



FU Tuning

Chris Nugteren wrote:UPDATE:
New actuator installed, boost rises to 7psi by 3800-4K and the wastegate has trouble holding a steady line( I guess because this turbo wants to flow so much) and it creeps, up to 8.7psi by 5500. Oddly enough it spools slower now too. With stock injectors, and a VE offset of 30% and some injector constant tuning, I got this car up to 5500RPM and 200whp/203wtq. Then the dreaded lean condition returned. Too bad cuz the graph was still climbing steep! There is a bit of room for spark tuning to get more power, but not much point if we can't get the whole RPM range covered. AFR flirted around 12.0 which is enough I think for this low boost tune. This car has the engine, turbo and pretty much the supporting mods to make good power, but I feel so hampered by the ECU. One could easily throw in some low impedance injectors and get more from this, but I honestly feel it would be better served having a standalone. Is there much in the way of install and wiring info for these cars for Megasquirt? I think the cost of this build thus far dictates the solution would need to be budget friendly if it were done in the short term, but have the flexibility to do it right. (or drive it as is and wait to spend big bux later) I have tuned a handful of different types of standalones, but not megasquirt...any info on this from those who have it?

Get some injectors that are worth a damn and tune it right...





P&P Tuning
420.5whp / 359.8wtq

injectors, agreed.....its the tune it right thing I question. I am definitely used to having more ECU to work with, but we'll see where it goes from here. You should know, I am just the tuner...I have an employer who makes the final decisions AND a customer who has to put out the cash. I can only SUGGEST the right way to do things, not always do they oblige.

Chris Nugteren wrote:injectors, agreed.....its the tune it right thing I question. I am definitely used to having more ECU to work with, but we'll see where it goes from here. You should know, I am just the tuner...I have an employer who makes the final decisions AND a customer who has to put out the cash. I can only SUGGEST the right way to do things, not always do they oblige.

I fully understand that....





P&P Tuning
420.5whp / 359.8wtq

good luck and keep us updated.