bgbfflochp

I'm having problems with my A/F ever since I got my car tuned for my new SC pulley. When cruising at say 50mph, the car will bog down, and by the time I look at my wideband, it's reading 23-30! (it's usually rising up to those numbers and then goes back down to 14) When I get on it, a lot of times(but not everytime) it'll go to 10 or even 9s. I guess my question is this: If I've got my car tuned to rich, could it be sending too much fuel and the ECU is trying to correct itself...hence the 23-30s? My friends say when I get on it, a lot of times I'll have a big cloud of black smoke shoot out...and half the time the car bogs down (especially 7000-9000)...so really I'm not getting too much power.

If my car is in fact at 23-30 A/F...wouldn't I be on the side of the road somewhere by now? And does anyone know what that might feel like? Would it feel like the car's bogging down? When I say bog, it stops gaining speed, and feels/sounds like I've got something in my exhaust that I'm trying to shoot out...and then it picks up speed as it gets back to a normal A/F ratio.

I'd hate to spend a bunch of money on another tuning session at the dyno if it's something else. It never did this with the stock SC pulley, and I didn't rev too high on the way to the dyno after the new pulley install, so I don't know if it has something to do with the pulley or not. I almost have to think it's the tuning and not the new pulley...so here I am asking the experts.

Any ideas?
Thanks,
Dave

fperra

When you let off the throttle in gear, the injectors cut off and the a/f shoots way up. This is normal. Just sounds like you are running way rich.

AusS2000

What is controlling your fuel?

I have had a similar problem. I have a Comptech with 8lb pulley and have sometimes had the choke whilst at low throttle position and suddenly opening the throttle. My A/F also shows lean at this point, but I expect it is actually rich and misfiring so the 02 sensor is seeing lots of unburnt air.

bgbfflochp

I've got a V-AFC controlling my fuel. My fpr is pretty much wide open with the vafc taking out a little here and there. My main "spikes" are when I'm cruising...and it always seems to be around 45-55 mph when it happens.

Do I need to get my car re-tuned? Or is this just normal (sucks if it is)? Do I need to look into bigger fuel injectors or anything? I'm not really sure what the stock injectors are made to handle.

Thanks,
Dave

BenR

How accurate is your wideband lambda?

AusS2000

It's not a good set up. Heaps of fuel pressure, stock injectors, and VAFC pulling fuel via the MAP signal.

I assume what the VAFC is doing is lowering the MAP signal so much that the ECU thinks you are idling. When you suddenly open the throttle it's flooding and misfiring (which the wideband sees as lean because of the unburnt air).

I would advise you to look at bigger injectors and an E-manage at least, or an AEM if you can justify it. Then you can drive the injectors properly without worrying about MAP based trickery and it's inherent side effects.

If you go with an E-manage I'll be happy to supply you with base maps but you will still have to get some tuning time.

bgbfflochp

fair enough, I have an AEM EMS on the way now. Anyone know if this is difficult to tune with? The guy that does all the tuning at the dyno mainly has experience with mustangs...but tunes random imports that come through. Will he be able to understand what's going on with this thing?

Also, you say fuel injectors. What cc would you recommend? I think I'm only going to run 8 or 9lbs of boost. And do you have any recommendations on where to order them from?

Thanks again,
Dave

AusS2000

RC Eng sell Lucas injectors in 440 and 550cc with the bit's and pieces to plug straight in. All you need to do is splice their connectors to your harness. I believe they now have even bigger injectors in the right impedance for our systems.

If you are running with a rising rate FPR you can get away with the 440's (that's what I'm using) but as you are going to the AEM I would suggest at least the 550's or larger as you will be able to drive them properly without going overboard with fuel pressure.

Gernby

Have you checked to make sure the belt hasn't come loose? If it is slightly loose, it seems that it could slip / catch / slip / catch, etc causing rich / lean / rich / lean etc.