First time tuning - 88 Fiero with supercharged 3800

[toadson]

Hello,

I purchased HP Tuners Pro about a month ago, along with an AEM 30-0334 wideband sensor. This sensor wasn't wired from the factory for a 5v reference like HP Tuners would use on a non-CAN vehicle, so I ordered pin connectors from digikey, #455-2518-1-ND as suggested on this forum. I've welded a bung in the exhaust before a catalytic converter and have it working with HP Tuners.

I've not done any tuning myself and have only done some scanning on my car. The car is an 88 Pontiac Fiero. The engine and transmission were from a 98 Buick Riviera and I swapped the Riviera PCM in the Fiero some time ago. I had someone tune the car before I installed a cam, and it appears they flashed it with a 99 Grand Prix GTP file. I don't know what exactly was done with the tune besides some minor adjustments such as a 180* thermostat, tire size, probably a VATS removal if I had to guess.

The engine is a supercharged 3800 series II v6, attached to the stock Riviera transmission, a 4T65e. I have a ZZP VS cam installed with L76 valve springs, stock rocker arms, a 3.4 pulley, full 3" mandrel bent exhaust with stock manifolds, 180* thermostat. I always run 93 octane gas.

I've attached a log. Theres a lot of cruising but also some wide open throttle runs. I'd like to see if anyone has advice for tuning a 3800, and if I should be scanning for any other PIDs. Thanks!


10-26-17 fiero.hpl

[5FDP]

Post the tune.

Add commanded AFR and injector pulse width for both banks to your logs.

It seems you may be losing fuel pressure too, in some of your WOT pulls the AFR on the wideband goes way lean and some knock starts to show. Also the o2 sensor mv drops from 900's down to 700's showing that it's running out of fuel.

[toadson]

Here is the tune. Didn't think to attach it. Also it's a 99 GTP file, not 98 like I originally posted. Corrected my original post.

I have a fuel pressure gauge. I could check to see if the pressure is dropping at WOT. I have a Walbro 255lph pump in there but it's probably 7-8 years old.

fiero-base.hpt

[5FDP]

Yeah for sure double check fuel pressure at WOT.

Also something to consider changing right away is how the power enrichment settings are currently setup. They were changed from factory but they did not change one part of it that you should do.

The BASE AFR vs ECT is setup to run 11.8 AFR in PE, then there is an adder table called ADD vs RPM. That tables adds to the commanded AFR based on time and engine RPM. The negative numbers in the table take away from the current commanded AFR.

If you look at it and using this as an example, say you were in the throttle for 4-6 seconds at 4000-6000rpm. It would be adding anywhere from -1.112 to -1.435ish. So that's 10.68 to 10.2ish commanded AFR. That's way rich and richer than you ever need to be. That too can tax the fuel system even more as it tries it's hardest to reach the commanded AFR.

If I recall correctly the factory base afr vs ect table is set to 12.400 for PE at operating temp, so the commanded AFR even with the add vs rpm active will still stay in the low 11's to high 10's after a long WOT pull.

You can either zero out the add vs rpm table or tweak the table to add less fuel based on your commanded AFR. I personally just zero the table out and set the commanded AFR to 11.3 or 11.5 to keep things safe.

[toadson]

Awesome, thanks for the advice. I've read about power enrichment and heard it really wakes up the LS engines. I wasn't sure if PE existed on the 3800 PCM's or not, but I will take a look at that table. I'm planning to do a lot of scanning and research before I change anything because I would rather not blow the engine up! One other things I've read about the 3800's is increasing the WOT timing. Sounds like its something you do in 1* increments to be safe, but a few posts I've seen people talk about adding several degrees of timing over stock.

[5FDP]

I'd still adjust the PE settings like I explained before you drive it a lot more and beat on it while you learn. You for sure do not want to be over doing the fueling while you are getting the hang of it. There is only two things you need to change there to command a constant 11.3-11.5 AFR throughout WOT, then you can adjust all the fueling from there using your wideband.

[toadson]

So I added commanded AFR to the scans. I also added injector pulse width for bank 1. I dont see an option to add bank 2?

Attached a couple of scans. I see what you are saying about the commanded AFR being in the 10s at WOT. I think I like your idea of "You can either zero out the add vs rpm table or tweak the table to add less fuel based on your commanded AFR. I personally just zero the table out and set the commanded AFR to 11.3 or 11.5 to keep things safe." I will look at modifying my tune to adjust that. I found my fuel pressure gauge so I'm planning to check that out hopefully sometime this weekend.



fiero 11-22-17.hplfiero 11-22-17 w2.hpl

[toadson]

Looks like I do have some fuel delivery issues like you mentioned. Psi jumps around from 38-50 psi. At WOT it spikes to 50 and starts dropping to 40, so they're definitely something wrong. Last time I changed the filter it looked full of rust so I'll probably end up dropping the tank since it's made of steel.

[toadson]

I dropped the fuel tank and there was a lot of fine rust floating around in there. Not sure how the car even ran with all the junk I found. I cleaned it out using muriatic acid and replaced the fuel pump sock and filter. I havent check the PSI yet but the AFR is much better. Still looks like it could be leaning out a bit in the 5000+ rpm range though. I will do some more scans and post them later and check out the PSI once the weather is a bit nicer here.

[ITSAV6]

I would replace the tank or use one of the tank inner coating kits. I had this same issue years ago on a Datsun 280Z. Cleaned it several times because you couldn't buy a tank at that time. Couldn't ever get all the flakes out due to design so I swapped the feed/return(external pump)and put a cleanable filter pre pump. It would stop up after 2-3 days of driving. After 6 months I cleaned it once a month and never had any more trash in it.