Okay I have a 88 IROC with the lo3 engine. I have done a few mods consisting of Team-G single plain Intake, 160 thermostat, and K&N X-treme Air filter set-up.

My problem is whenever I lean into the gas really hard it bogs, backfires, almost stalls until the revs get built up. If your in first an spining 3000rpm and mash it there is no problem, it still accelarates like crap but not as bad. It runs fine if you go out after it has been sitting for 5-6 hours start it up and immidiatly drive it. You can hear all the gas that is being injected but soon as it warms up it runs like crap again. I am thinking maybe lack of fuel since I have increased the airflow, because it never did this with the stock intake. Thanks

 

yea you really need to tune for that .

 

Needs more pump shot.

I had to more than double a few of my pump shot values, when I put the team-g on my car.

 

I am not into the chip burning. Don't have the time since I am in school during the day an working at night just to keep the car going is bad enough. Do you think data loging and maybe getting a chip from tbichips.com would solve my problem.

By the way what is pump shot.

 

Pump shot (accel enrich) is additional fuel thats overlayed on top of whats normally injected by the injectors. In the tables, you can store anywhere from several milliseconds all the way up to one second of injector on time. Bascially it just richens up the mixture to compensate for fuel settling out, need for additional fuel during changing engine loads, etc. In the factory code, they double the ammount of 'pump shot' at high loads so they can skimp on it at lower loads. This is probably to help with emmisions at low throttle or drivability. When you mod the motor, though, this can really leave the car with a lack of fuel after the throttle first opens.

Id still check the fuel pump first to make sure the pressure isnt cratering under load. A dead pump will really cause problems.

 

i think your increased plenum volume/plenum surface area has something to do with it. venturi velocity lacking? i assume this happened day one after the mod. i had same occur day one with single plance BUT i may have overcompensated in tune with too much AE/PS. discovered that with WB02.

 

Yes it happened from the first time I bolted the new intake on. It ran perfectly fine with the tbi intake, it even spun the tires from a crawl when you layed into it considering it only has 170 hp. I cant even keep up to by buddies 1990 VW GTI with a VR6 Engine swap. Also I have headman shortie headers and a 2.5 inch flowmaster exhaust these mods however increased the power with the stock intake.

 

That engine/car is not anything to sneeze at. The power to weight ratio compared to what you have on an f-body is very different.

 

Ya I know it was dynoed at 230 RWHP. He's got complete header, exhaust, computer work, etc. It used to only pull 1 maybe 1.5 cars on me now its like 3 or 4. That will change this summer when I build my 383 and spray it.

 

Also sounds like it could be a timing problem. Did you recheck the timing after doing the intake swap? That is exactly what mine did after my intake swap and it was due to the timing being way off. Good luck!

 

While the subject is up I had the same problem until I increased the pump shot. It corrected the problem except when it gets colder outside. It mainly does it the worst when crusing in 4th or 5th gears or the car is really cold.

Any suggestions? Is there a cold compensation table in the chip that reads the Inlet air temp that could richen the mix up when colder?

Tnanks DM

 

Ya I thought it would be the timing but I checked and it was 4 advanced. I know the stock timing is 0 but I advanced it a little to get better throttle responce. And if you dont mind DM how much did you increase the pumpshot.

 

It was a while back so give me some time to look it up but from what I can remember it was considerable.

 

Looking at it I must have kept adding until it smoothed out on accel. No real number suggestions.....Dewey and others could give you more input here. I still have way more questions than answers. But the point here is you need to be able to tune it to see what it wants

 

For hard numbers.

Pump shot vs. Delta TPS (Before intake/cam)

3906
2197
854
610
549

Pump shot vs Delta MAP (before)

2929
1464
976
366
183

Pump shot vs Delta TPS (after)

4894
2902
1803
1315
849

Pump shot vs Delta MAP (after)

4450
3324
1975
819
240

Since PS is measure in usecs open, when I did this, I also raised my fuel pressure. So the ammount of fuel actualy going in, is even more than the usecs added shows, since the amount of fuel per usec has also gone up.

HTH,
John

 

Dewey: yours is a 350 cid? what is fuel pressure before and after? my last mods resulted in me determining my PS was excessive. at that time i added the Innovative WB so that opened my eyes. i maintained FP at 12 lbs. possibly the Holley Manifold did a better job of managing fuel and needed less AE. prior was the Xram set up and single plane. i was off chart on WB for AE (8/1 or richer). PE however was lean at 13.2/13.5/1 when commanded at 12.7/1. i since corrected that to 12.5 commanded but see little response on WB. will up FP to 15 lbs and revisit my AE and VE tables this spring. looks like that cam likes fuel. thats a good thing !

 

Ronny,

I'm still on a 305.

I might be a bit exesive on the fuel in AE, With my using nitrous, and not hooking a WB up yet, I tuned it so it wouldn't backfire when I nailed the giggly-go.

I'm dyno'ing it a couple of times this spring, once in about 2 weeks, again early April. Several of us that I tune with, went in on an LM-1, I just need to weld a bung in, and do some LM-1 Tuning also. But, lately I've been busy and lazy, hopefully this spring I will make some better progress.

And I'm running 17psi on the stock injectors with my combo. I needed the bump, to keep it fueling at my 6250 RMP shift point, without going static.