1989 350/five speed with heads, cam 24lb/hr injectors, 52lbs fuel pressure.

The car is running 16:1-18:1 at WOT, and about the same at idle.

I've tried changing the injetor size, messing with the MAF scalar tables and even the PE table, but nothing seems to be moving the A/R in the right direction.

Using a Prominator and Tunerpro.

What should i do next?

 

Sounds like a mechanical problem. How old is the fuel pump, fuel filter?.

Air leak post MAF?.

Do the logs show the MAF reading about right?.

 

What PE table have you modified? There are 2 in the 6E mask. One is PE vs RPM and the other is PE vs Temp. If you are sure that your fuel pump is i good working order, start modifing the PE vs Temp table in 8 to 133 degree region. The temp table makes more dramatic changes to the AFR that the RPM. Go ahead and scale the table by about 130% and make another WOT run with the wideband hooked up. See if there is any change.... Also make sure to get the car up to operating temperature first.

Also...what mods do you have done to the car and does your data logging software display injector duty cycle and pulsewidth?

 

I think the fuel system is probably OK. I've got a gauge on the car and i'm not losing any pressure during the pulls. I don't believe there is a leak past the MAF either. It's sealed up pretty good.

I just have the free version of Tunerpro, so i haven't datalogged anything. I was uising a Snap On scanner to watch the BLM during the pulls. It was anywhere from 118 to 135.

I was modifying the PE vs. RPM table and the car was up to operating temp and in closed loop when i made the pulls.

How do you scale it by 130 percent? It might help if i had the program in front of me right now but unfortunately my laptop is at work and i'm at home.

The car has a full exhaust on it with dual converters. The O2 sensor is only a couple ofmonths old and i was using a wide-band on the dyno to tune it.

 

During WOT runs the BLM should lock at 128 since the ecm is running in open loop. To scale the numbers just use the calculator and multiply the number in the PE vs TEMP table by 1.30 and you will add 30% more fuel there since you are running extremely lean at WOT....

 

PE in $6E .ecu's out there is calculated incorrectly.

https://www.thirdgen.org/techbb2/sho...hreadid=259424

and the important part of it:
Edit the ECU items for both PE's (right click on them, edit ecu item)

For PE vs RPM
Multiplier = .390625
Offset = -50

For PE vs Ctemp
Multiplier = .390625
Offset = 0


This way, if you add the numbers they will total the total added percent. So, if you want 12.5:1, you simply take 14.7/12.5*100-100=17.6%, and the two PE's must add to 17.6%.

If you want 13:1, take 14.7/13*100-100=13.07% total PE.

Cool eh?

BTW, this IS how the ECU calculates it, but in hex. The commanded A/F will follow these equations.

A couple questions:
1) Where is the WB installed?
2) What have you done to gaurantee no misfires?
3) Does the engine sound OK when doing these 16-18:1 WOT pulls?
4) What brand of WB is it?
5) Is there any check engine light?
6) Could you try a stock calibration with just changing the injector constants, as a reality check?
7) Could you have a bad MAF?

 

The wide-band was installed in the tail pipe. Its a dynojet for the dynojet i was tuning on.

I switched MAFs and nothing changed. The engine sounds good and i don't believe i've heard any misfires. Sounds pretty crisp. I thought about trying the stock 350 program, but haven't found one that i believed to be a stock 1989 350 program. I also would need to know what to change in the program since i have a manual transmission.

No CE light either.

 

Bingo, install it in the o2 bung on the car.

 

It's just the poker type of rod that they stick in the tail pipe. I'm not sure that would be feasible considering where the O2 is. I don't see how the Gm cars can differ that much from all of the Mustangs i've seen on dynos that get tuned through the tail pipe. But oddly enough, someone else just emailed me to do the same thing.

 

In the program i'm using, the PE Vs. RPM table has .781225 as the factor, and an offset of -100. The PE Vs. Temp table has it exactly as you listed it with .390625 and 0 offset.

Steve

 

Where did everyone go?

 

Like mentioned above, you still have cats on the car.
So you must either put Wideband Before cats, or take cats off.

If you are seeing 16:1 then the cats are doing their job.

 

I've spoken with two companies who've tested before and after cat samples and there is no discernable difference between the two so i can't see the converters as being the problem. My lack of knowing what to manipulate in the program is probably where the issue is at this point.

 

I don't agree with that,
If a cat is doing its job, it will burn raw fuel in the exhaust stream which will burn the 02 in exhaust stream as well.

Why do you think many new vehicles have before and after cat o2s? If it did not make a difference, they would not bother.

What are your BLMs at idle? If they are with in 128 +/- 5 the car should still be around 14.7 before cat - But you are seeing 16 at idle. After cat!

Also if you have any nice exhaust leaks they will pull fresh air in, even at wot and skew results.

But I would also think that you should see a difference when you richened the mixture. Did you try doing it manually by raising Fuel pressure?

 

The BLMs were anywhere from 118-135. There aren't any exhaust leaks to my knowledge and i have tried raising fuel pressure from 48 to 50 and then 52, but still nothing.

 

The F/P can be fine, but the volume can be low. It's only as the pump goes into it's death throws that pressure drops. If the pump is more then 2 years old, get a new larger one. 2 years you say?, yep, I've seen too many guys chasing numerous lil bugs in drivibility that wound up being pump related.

 

Well, from what I think I know:
A cat with no air pump will not skew the results more than a few tenths of an air fuel ratio.

Our cars have air pumps, but they are supposed to be disabled from pumping air into the exhuast at WOT. Maybe that valve on your car is broken. I don't know how much air it would take to do that, but it's a little rediculous to think that it could make that much difference if it's injected to the cat. The cat would take that air and CO, and melt its way to here in China, unless that second brick of the cat is already blown out.

I'll have to disagree with Grumpy here, unless the pump is sucking air from a bad pickup, or fluctuating so fast that the gauge isn't catching the bad flow. If the pressure is steady at 52 psi - at WOT - at peak HP, then it DOES have the flow required (unless a problem like stated above is occurring).

Maybe you're reaching the max airflow vs RPM threshold. That'll clamp the airflow reading. It was probably some limp home thing combined with a way to limit AE or some other thing like that, and keep people from hotrodding their engines too much (i.e. who really knows). How much heads and cam do you have?

 

I'm going to have to agree with grumpy here, You couldnt' blow through my old fuel filter , but at WOT it kept a study 45 psi at the shrader valve. I was dumping a ridiculous amount of fuel in, like my PE adder tables were all up to 20% when stock is -8%. When your still running 14.5 ET's after a head and cam swap you know somethings up. It was a really hard problem to diagnose, but I learned my lesson, don't ever skimp on the fuel system.

Mine was off the scale when I had some small exhaust leaks, even WOT runs wouldn't knock it down below 2.5V (stoich with a zeitronics) both o2 bungs are in the y-pipe, another mistake I won't repeat. The exhaust leaks were completely un-audible, but after tightening the collectors some it helped it a lot.

 

Check the archives, at DIY-EFI, and Turbobuick.com and get back to me..

Ask, Tpi_guy@hotmail.com or look for his posting about it at DIY.
It's been about 6 years now.

If you want to assure volume, then you need to check the pressure on the RETURN line. If you have less then a couple PSI, your out of pump.

Not to mention that as you increase the PSI demand on the pump, the volume drops.

 

There's just no way to have too much ignition, or too good of fuel system, up until the point that you overwhelm the pressure regulator. ie on my lil 3.8L, I run 2 staged, 340 fuel pumps. The second one coming on at ~3 PSI of boost.

There seems to be a certain unknown IMO, about how the fuel rail pressure surges, and it's refill rate as injectors open and close, I don't think it's as obvious as it looks. With larger injectors, a controlled PW/DC, you have to, have an really good refill rate to keep up with the injectors, or so it apprears to me. IMO, there maybe more going on that's lead to the non-return line systems that the oems are going to.