When does a GTP stop pulling?

[louvered97gtp]

Yes I can swap a 3.4 pulley. But my setup should let me use as small as a 2.8 pulley from what i understand. My 99 is intercooled with a GenV.
You think the boost might be an issue? I've ran 13psi at the track previously with no issues a month or so ago, this problem suddenly surged and didn't have this problem back then. Only thing that appears to make this problem go away is when I run a 10:1 WOT AFR. I did this last night but will try it again tonight to see if this was a fluke or not.

[streetcar]

The fuel pressure is definitely low, which is why the MAF curve is a bit funky -- however I don't think the lean spike is the result of a fueling problem as the rail pressure is consistent, low, but consistent even with more demand placed on it.

Moving to a larger pulley, lowers the amount of air entering the cylinders, lowering the cylinder pressure (and power output). It's an easy way to see if it is a spark/coil related problem.

Also, try the attached MAF table. It's a bit more polynomial like, and the variance between the two are very small, and would put the car in the rich side worst case. Use the the folder icon (load table) in the MAF Airflow vs Output Freq window on the top left to import the table.

[louvered97gtp]

Thanks for your efforts and help on this. Much appreciated. I'll load this in an hour and post up results as I'll have to return the wideband to it's owner tomorrow. Shipping the wideband back to my friend in Pensylvania.

[louvered97gtp]

The fuel pressure is definitely low, which is why the MAF curve is a bit funky -- however I don't think the lean spike is the result of a fueling problem as the rail pressure is consistent, low, but consistent even with more demand placed on it.

Moving to a larger pulley, lowers the amount of air entering the cylinders, lowering the cylinder pressure (and power output). It's an easy way to see if it is a spark/coil related problem.

Also, try the attached MAF table. It's a bit more polynomial like, and the variance between the two are very small, and would put the car in the rich side worst case. Use the the folder icon (load table) in the MAF Airflow vs Output Freq window on the top left to import the table.

Well, tried the LQ table provided and the car didn't like it. It sputtered as if a missfire all through the WOT run, sounded similar to what I imagine water being sucked through an intake would sound.
Attached is the scan of this run.

Also attached is the run with a 3.4 pulley. the problem seems to be gone on first run, but starts appearing again in later runs. On the second run, the car suddenly lost power and bogged right before it shifted, this is seen by the sudden lean spike. The last run shows this lean spike again at the end as my usual problem.

[streetcar]

Hrm, something is definitely not right if you're experiencing misfires.

[JerryH]

Could you have a bad batch of gas? Happened to me once... was a bitch until I refilled and drove out that tank. I stopped going to that gas station and things improved.

[louvered97gtp]

No bad gas, I've been having this problem for two weeks and have filled up at my regular gas stations, 2 of them. Problem persists. I've been told to try lowering fuel pressure, that even though it seems backwards it's worked on various cars where slightly lowering pressure helped a similar situation while increasing pressure made it worse. I've found quite a few cars that did this successfully so I figure it's worth a shot. Also, I might just need to replace the fuel pump and see if it's failing and can't keep up. Problem is, I dont know how to lower fuel pressure, I'm assuming I'd need an adjustable regulator. Still trying to find out.

[JerryH]

The stock GTP fuel regulators are of fixed values and you cannot adjust them. A person with the right abilities could use the FPR from a 1999 Cadillac STS with the N* engine and use that. It also is fixed but they have a torx screw on top that is held in place with loctite. The touch of a torch, a little twist, and there is your $25 adjustable FPR.

You *still* would need a method to monitor the pressure. Install a gauge on the schrader valve of the fuel railing for an additional $25. Voiia... all done!

[streetcar]

No bad gas, I've been having this problem for two weeks and have filled up at my regular gas stations, 2 of them. Problem persists. I've been told to try lowering fuel pressure, that even though it seems backwards it's worked on various cars where slightly lowering pressure helped a similar situation while increasing pressure made it worse. I've found quite a few cars that did this successfully so I figure it's worth a shot. Also, I might just need to replace the fuel pump and see if it's failing and can't keep up. Problem is, I dont know how to lower fuel pressure, I'm assuming I'd need an an adjustable regulator. Still trying to find out.

Fuel pressure is low enough...lowering it even more will just lower overall fuel delivery leaning the car out. If you want to throw parts at it, start with a Racetronix Pump and GP Sorenson regulator. Fuel pressure hasn't changed, but something else obviously has.

Have you tried the 3.4 pulley?

I'd like you try an additional test to isolate the problem from being fuel related. If you can, pull the supercharger belt, set your Power Enrichment -- Base AFR vs ECT to 12.8:1 and zero out the Add vs RPM table. Repeat the tests in a familiar matter you've done before (wind it out to 6000RPM).

I'd like to see the results.

[Eddie-98GTP]

Hey guys. I was just reading his thread and noticed something no one has mentioned (at least not that I saw). There are 3 torque management tables that will kill injectors that are still set to stock levels. I would try to zero these out (the injector fields) and see if it helps. It would be very easy to for the PCM to reference these tables with your mods.

Hope this helps.

[streetcar]

Hey guys. I was just reading his thread and noticed something no one has mentioned (at least not that I saw). There are 3 torque management tables that will kill injectors that are still set to stock levels. I would try to zero these out (the injector fields) and see if it helps. It would be very easy to for the PCM to reference these tables with your mods.

Hope this helps.

Eddie - Those tests when active would change spark, and commanded AFR.

(I run the factory torque management settings and have never had an issue @ 330whp with any injector cut sans burn outs)

[Eddie-98GTP]

Eddie - Those tests when active would change spark, and commanded AFR.

I just thought it would be something easy to try...

[streetcar]

No doubt.

EDITED for the wrong PID. PID should be Volts/.0313+-9.7 for the Aeroforce FP kit.

[louvered97gtp]

Thanks Eddie, I zero'd the # injectors to disable and will give that a try.

Streetcar, what's with the +0 in the string? Is that necessary?
And volts multiplied by 26 or divided by? I thought the asterisk meant multiply.
I've attached two screenshots to clarify and ask which one is correct.
Thanks,

Steve

[louvered97gtp]

Fuel pressure is low enough...lowering it even more will just lower overall fuel delivery leaning the car out. If you want to throw parts at it, start with a Racetronix Pump and GP Sorenson regulator. Fuel pressure hasn't changed, but something else obviously has.

Have you tried the 3.4 pulley?

I'd like you try an additional test to isolate the problem from being fuel related. If you can, pull the supercharger belt, set your Power Enrichment -- Base AFR vs ECT to 12.8:1 and zero out the Add vs RPM table. Repeat the tests in a familiar matter you've done before (wind it out to 6000RPM).

I'd like to see the results.

Yes, post #24 has the scan with the 3.4 pulley.
The add vs RPM was used only during the 3.4 pulley test per your recommendations. I've since already zero'd this table out again.
I'll give this test a shot later tonight when it's cooler and less traffic.
I'm unemployed at moment so if I this can be diagnosed and fixed without having to spend on a new pump right now it would be great. I'm not in a great position to be spending more money than absolutely necesarry so Thank you for the help.

[streetcar]

I rechecked the Aerofore instructions and the PID I stated in post #33 was incorrect.

They give 31.9 as the slope, and -9.7 as the Y intercept, so equation would be y=mx+b or 31.9*Volts+-9.7. Since HPT would like a divisible approach, the inverse of 31.9 (1/31.9) = .0313. The equation should look like Volts / .0313 + -9.7



Check your plugs/wires/coils. Try enabling the P0300 Misfire Detection DTC and create a separate config to scan for misfires and total misfires. The data won't be usable at idle, but under WOT they may shed some light.

[louvered97gtp]

That's an interesting screenshot you got there. I have nothing like that, and your post makes me wonder if I need to program these slope and intercept values into a custom PID to read the fuel pressure guage correctly. That screenshot is for the fuel pressure reading or the volts reading? Sorry for the ignorance, the custom PID's is still a bit confusing.

[streetcar]

That menu is the submenu of the Configure User Defined when inserting a PID into an EIO output. The VCM scanner will not allow access to the Configure User Defined menu if a scan is open.

Load your config, bring up the table display, right click on EIO Input #2 (Where you have the "Fuel Pressure - Autometer" PID, select "Insert". That should open the "Insert AUXs" window. Click the plus sign next to User Defined, double click Configure User Defined. If the option isn't there, you probably have a scan loaded. Click on one of the Undefined slots, name it, set units, and enter the transfer function from post #36. Leave the sensor field blank.

To reference the PID - it will be under AUX Input List - User Defined.

[streetcar]

If you're wondering the difference between the two PID equations check this out:



The green line is the Autometer PID, Black line Aeroforce PID. Y axis is fuel pressure, X axis is volts.

[shoafster]

there is a setting that bleeds off boost after 116 mph. look in the supercharger torque management settings and there should be a setting that does that. just change it to 255 mph, and increase the supercharger timer to 30,000, that way it doesnt limit boost when the timer hits 12800.