ECU Help???

[art leong]

I got to the track Friday night. And devoloped a problem. I'm totally new to the tuneable electronics. So I didn't have a clue about what to do about it.
The car wouldn't make any power in the lower rpm ranges. Similar to a carburated car with out an accelerater pump. Seems to be lean very, very, lean in the lower rpms. Once the rpms get to around 4500 it runs great. But It won't even spin a tire in the water in first gear. It breaks up bad. Seems like a lean condition to me.
This a something that happened overnight, it didn't do this before. My biggest problem then was traction.
The data logger is telling me the air/fuel ratio when its running bad is at 15.94 to 1 or above (this is the highest the sensor reads) Bad when it cleans up goes down to around 13 to 1.
When it cleans up it revs good to 7500 when I shifted it drops down to 5200 and revs fine.
The only changes I made to the car were adding weight to the front end. Bigger battery etc and changing my air intake setup. Neither of which I think could cause the problem.
Tomorrow I'm going to take my data to the guy that setup the ECU in the car. And see if they can figure what happened. But I don't have complete confidence in them.
I'll need a crash course in tuning these ECU's. Maybe someone can help a little at the southern racers race at Silver Dollar Raceway
Any ideas???????

[Bernie Cunningham]

How's your fuel flow, filter, pressure?

[art leong]

Fuel pressure is 43.5 psi using a Aeromotive 1000 pump fiters are all new just 2 runs on the car.
No problem with acceleration because I can't get the tires loose in the water.
The air/fuel ratio starts way lean then gets "normal" when the car cleans up at about 4500 rpm in gear.

[Sean Haning]

Hey Art, there are a bunch of very knowledgable tuners of 2.2, 2.5, and 2.4 as well as 2.2 hybrid cars on http://www.turbo-mopar.com/forums/cmps_index.php Go over there and ask and I'm sure one of the calibration or standalone "experts" could help you out.

[Ed Wright]

Art, your air/fuel ratio will look extrememly lean at lower RPM, due to fresh air being pulled back in the collector during overlap. You need to put a muffler, or at least 18" of collector extention to know what the actual air/fuel ratio is at idle, on the converter, and launch. Once you get that dialed in you can remove it to race it. Be sure, if you are going to run it in closed loop to set the min RPM for closed loop fuel corrections higher than the RPM you will stall it on the converter. Otherwise the ECU will be pouring the fuel to it down there to try and correct what it assumes is an extremely lean air/fuel sistuation with the exhaust extention gone. If you can put a bend in the extention, that would be even better for the initial low RPM air/fuel tuning. I no longer run my FAST in closed anyway.

Good luck, Ed

[art leong]

Hi Ed. You might be on to something with my problem. Is it posible the open loop parameters are messed up. And when it gets up there in closed loop it straightens out and runs fine?

[Ed Wright]

Originally Posted by art leong

Hi Ed. You might be on to something with my problem. Is it posible the open loop parameters are messed up. And when it gets up there in closed loop it straightens out and runs fine?

Could be Art. Set the min temp or min RPM for closed loop exttremely high, and get the fueling corrected in open loop with the muffler or long header extention installed. If you get it running well warm, but it has problems cold, only change the temp correction tables to address that, or you will be changing your warm/no temp correction tuning. Remember to not let it run in closed loop at low RPM with open headers.

[NovaMan]

Just out of curiosity, is this a speed-density system or mass airflow?

[Ed Wright]

Originally Posted by NovaMan

Just out of curiosity, is this a speed-density system or mass airflow?

Speed Density.

[art leong]

Originally Posted by Ed Wright

Could be Art. Set the min temp or min RPM for closed loop exttremely high, and get the fueling corrected in open loop with the muffler or long header extention installed. If you get it running well warm, but it has problems cold, only change the temp correction tables to address that, or you will be changing your warm/no temp correction tuning. Remember to not let it run in closed loop at low RPM with open headers.

I'm using open loop all the way through.