Diablosport Forums

2009 R/T Challenger Auto
Long Tube American Racing Headers
MBRP Exhaust, minus cats
Predator Diablo
AFE CAI

I run 92-93 octane and modified the 91 CAI tune to give more fuel across the board. Smells rich at idle. Is the extra fuel necessary, or is the canned tune ok with the full exhaust? I don't have my data log handy, but I can get it. I also don't like the performance of it. At one time it would break the tires loose at 45 mph or so, now it won't spin 'em at 30 mph. Somethings robbing power (maybe TCM?.) Even after resetting TCM it's not much better. Dyno mode ON.

Its your lack of cats. You have no backpressure, which lowers the exhaust velocity, which hurts your torque production and scavenging.

I agree, to be honest, I don't think you've done enough to your vehicle to go catless. High flows yes, but full catless no. Your exhaust gas velocity tanked when you did that.

What should I do to the engine then? Cams? It has ran good at times like this, just not consistently.

You have two options.

You can throw a set of high flow cats on, and you will probably see an increase in low end torque due to increase exhaust gas velocities.

Or you can cam it. If you just want something mild you can go for something like a FRI Sidewinder, great driveability, great low end torque, very easy to tune and you can do it without losing MDS (I don't have one, just based off of my research). You have a great base to put a camshaft into, your engine is breathing fine, a cam and a custom tune will really wake it up.

Heads, cam. Be alot easier just to put on cats. I run 11's with cats, so its not like they're a restriction.

Ok, thanks all for the info. Back to my original question: what do ya'll think about the 91 CAI tune without adding the extra fuel? I've since read that it won't affect part throttle, so if it's rich at idle, the predator can't fix that. I smell like exhaust fumes after driving around for a bit. I've ran trucks without cats before and don't remember the smell after driving. Hell, maybe I have an exhaust leak that I can't hear - just thought of that possibility as I type...

You can't change your fuel part throttle, the computer knows at air to fuel ratio its trying to hit and does it on its own. The only time you can change your fuel is at WOT (this is why Part Throttle Fuel Controllers were invented). You could go back to stock and log your knock retard, and if you are getting knock retard at WOT, then you can try adding more fuel.