Dave, no disrespect either but the dyno graph you show is using stock headers. The question asked was whether adding cats to an already torque shifted curve would make it more noticeable not whether adding cats would drop torque. It's the headers in his scenario that are causing the torque shift. I'll bet his car is a blast to drive from 5000rpm to redline but that just may not be practical in day to day driving.

 

You won't be disappointed...

 

Go to AWEs website...there is a dyno there for headers as well...shows no drop at all in the low end torque range.

Dave

 

I went there, didn't see a dyno of GMG Headers + AWE Cats. Not all headers are the same and most tuners match their systems to work well with each other. You have to look at the entire exhaust system as a whole and not as individual parts. I went to GMG's site too but couldn't tell which setup he got...

 

Duh, my bad. AWEs site shows their headers not GMGs. Could be a difference, probably not much if any though.

Dave

 

I agree, I don't believe it would make so much of a difference... GMG is a reputable shop, so their products should be good

 

It's not a question of whether GMG is good or not. GMG is a race shop that makes racing products. What's good for racing may not be practical for day to day driving. Tuners like AWE, develop complete systems that maximize performance without compromising practicality of day to day driving. IMO, it is not a good idea to mix and match exhaust component manufacturers. Perhaps the OP can shed some light on why he chose GMG over AWE for the headers. I would also suggest that readers of this thread do some googling on exhaust header design to understand how primary tube diameter and length can impact torque bands...

 

I originally was going to get the IPD Plenum and GIAC flash. However, after reading the forums extensively and seeing the lack of agreement on the effectiveness of the plenum, I decided to go with something traditional instead. GMG had the headers and chip in stock, so I had them installed while I waited for the cats.

In retrospect I made a hasty decision and probably should have ordered a matching set of headers and cats, as that could be the issue. I also should have only installed one mod at a time (my novice reasoning was that I would feel a larger change in the car if I did multiple at once).

I did unplug the battery for 15 minutes as recommended, but it doesn't seem to have a made any difference.

GMG does have a dyno, perhaps I should take a few runs on it to see what the torque/horsepower curves look like? The downside to this is I really don't wish to throw a few hundred dollars away on a dyno that I don't have any benchmark to compare to.

 

I would contact GMG and discuss with them what you've noticed. They are good guys and can tell you exactly what their headers are doing without the need to dyno. I'm sure your car is making large hp gains and is much faster overall. Work with them and GIAC, they'll help you out and make it right.