Since Ive added dual Catco cats to replace factory pieces that broke up ive noticed my trap speeds havent been where they were even in better weather. Before I ran my 13.52 my best ET was 13.63 at 99 MPH. My MPH has consistantly been 94.7 but my 60fts are a little better (in the 1.77s before was 1.8s). Is the better 60fts killing my MPH or could it be the cats since its the only new part on the car?? I like the times Im turning but the MPH looks less than impressive when before I was flirting with 100 MPH and even went over as high as 100.8. Is there a possibility the car is leaning out like someone suggested to me? Also if this is a possibility, would adding headers add to this and would adding and adj fuel reg help matters any?? Any opinion or suggestions would be appreciated....

 

FWIW, my best times and best speeds have never come on the same run. And, the best speed runs never had the best 60 ft times. You are probably experiencing something to that effect.

Did anything else change with the cat change, like traction? If you were marginal on traction with your best speed runs, your times suffered. If you are now launching better, it won't take as much time to get through the distance and therefore you won't have as much time to build up speed.

Perhaps someone else can provide more insight.

 

The cats are the only part thats different and my 60fts were LOW 1.8s and now 1.77 range. I have in the past trapped at this MPH but Ive also trapped as high as 99.xx but up until the last of the year when the track closed 94.7 was almost a given and not once did I see a 95 MPH trap speed or did it go below 94.5. In the end Im looking for better times but the MPH shows to me there isnt much left in this combo, thats a pretty efficient ET for that MPH. Now I have SLP headers, Ill have my AC removed and a few other odds and ends by March when the track opens. Im gonna try to add a adj fuel reg when I port the plenum and see if I gain anything from that, I was just wondering if anyone else has run into this problem with after market cats, cause 1 other guy I know has as well with Catco or was this a traction thing or just a matter of the car running at its limits??

 

It does tend to indicate that you're doing your best work at the beginning. Altitude not withstanding, I'm in your MPH range but 1.5 sec slower (with the '57). I know I'm slow off the line (2.3's) because of gears, and to some extent the heavier car, but obviously I'm making pretty good power overall.

I'd guess you need to tweak some more to get all your combo has available. I wouldn't say the cats have hurt you, but rather unbalanced your system. The AFPR should help, and headers typically help IF the rest of the system (like fuel pressure) is adjusted accordingly.

One advantage of high MPH to ET in bracket racing is people tend to mis-judge you at the top end and back off - Bye, bye!