So as some of you know I picked up Jim's (amx1397) old exhaust a few months back. Added an H-pipe for less pop and better flow. So I took it to the track and didn't see really any gains with this "bolt-on". Well after getting an AFR reading done to it I can see why....the damn thing is all over the place between 4k and 6k RPMs. It's actually robbing us power without a proper tune


WHP: 313hp

Bear in mind that I was pulling a solid 12.0 (5k-6.25k) after I got my initial ECU tune w/ a Code3 pulley when we had our Tuning GTG in Miami in January. So with the extra exhaust flow the ECU is really undercompensating. So it looks like that even if you want to mess around with the exhaust, be prepared to get your ECU re-tuned.

I sent my ECU to Jerry to get the tune fixed up over the weekend and I expect it back on Wednesday. I'm hitting the track Thursday if it stays dry and I'm going to try and get the car re-dyno'd on Friday.

I don't know of anyone who's done a custom exhaust and posted before and after times, but without the retune, the best I did was a 12.5x with those AFRs being all over the place

 

That is good to know. I got my exhaust done a while ago, I now have the C3 pulley and an intake on the way, so I will definitely need a tune.

 

Yep, waiting to get my car re-tuned too since I now have the Magnaflow. I figured that was the problem with your car since you went from stock to a really opened up exhaust. It may not affect my car as much since I was already tuned for no cats and no resonator. But still, I'll hit the dyno after getting her re-tuned to see if I'll need even another.

 

Interesting...although to be totally accurate, the ECU does not perform any form of closed-loop compensation at WOT.

 

I had set my controller to about 12 to be safe and got rather close to it on a pull.

Officialy had 6 dyno schedules bumped, dropped due to "events" Trying another (third shop).

Ill try to get my chart with the a/f up if it is in my files.

Woody
Yess it sideways, I dont know how to rotate the file????????????WW

 

When you tested the 12.0 set up did you have a stock set up? Is the new set-up better breathing (less cats, larger diameter, etc.)?

Unless you are pulling AFR from right past the headers you are basically just seeing a compensation of more air being entered into the mix POST-Engine. That has zero effect on performance or engine behavior.

If you took an AFR reading from the tail pipe and one from the stock 02 location, the tail pipe would be about 0.5 pts different as there are additional obstructions.

For the most part nothing short of long tube headers will have any substantial effect on AFR.

 

The a/f was checked by screwing in a sensor in the factory location.
The readings were the dual inlet, 178 pulley, muffler delete, and porting of intake/heads plus little stuff like my super cooler, pulley fix and stat.

I get mixed comments on the desired a/f mixture , had a guy that says he was closer to 14:1 Wow, not me.

Woody

 

From my understanding most cars injectors open to 80% at WOT, is that also true with the crossfire?

 

So Mike, did you get the ecu back yet? Very curious to see what difference it made.

 

Well if the weather conditions weren't so muggy I'd let you in on the track times. Let's just say a DA of nearly 2000

The car does feel a lot better but since it's summer in FL, drag racing in these small S/C'd cars aren't doing any wow'ing or just maybe the exhaust is detrimental to our cars. I've though about throwing the stock one back on (even though it'll mess up my Tune again since it's tuned for an exhaust but I'm sure it wouldn't hurt)

I wasn't able to go on the dyno today because it was my dad's b-day, so I'll try to go sometime next week to get a reading.

 

Any update?

 

It's been way to hot and muggy down here the last 2 months.