i have an 86 rx7 and i was wondering hoe much my hp would increase if i put a 2"catback system on it? the mufflers are bombs and the cat is high flow. this is very puzzling for me to figure out. alot of people tell me it will increase by as much as 30%. i really dont know. maybe you guys know

 

A catback will give you about 5-7 hp at best. The restriction is the cats themselves.

 

well then how much would it improve my 1/4 mile time

 

I agree with Felix to a degree, but on my car the improvements from a catback were far more dramatic than when I went from cats to gutted cats to header/presilencer, the stock y pipe at the fork is only 1 5/8" in diameter and poses the biggest exhaust restriction, I installed the dynomax catback, and the difference was huge between the it and the stock catback, I guess it depends on what kinda of shape the cats are in, if they are plugged or starting to break down, the catback won't do much, but if they are relatively free flowing the improvement will be greater, I also noticed an increase in fuel mileage with the catback install..Max

 

Yeah if you had header/presilencer or midpipe or highflow cat or whatever first, the catback will give you a better kick in the ***. On stock **** though, it won't help a whole lot.

 

Well, when I only had an intake my best time with the g-tech was 16.4 on this one road near my house (Flat). I had actualy ran a 16.6 at the track but it was only my second time going so I improved my launch after that. but anyways.

BTW my car did have the main cat when I got it.

I then installed a RB header to the custom midpipe and a RP 50mm cat back from RX7.com all at once.

I went back to that road during the same climate as my last run (80 degrees in FL), and got a 15.34

I then ran it again one night when it was 50 degrees and managed a 15.14.

SO, if the full exhaust gives you over a second I'm guessign the cat back alone might give .5 or so.

 

the full RB exhaust also raises your boost pressure a lot... because there's less backpressure in the exhaust, the wastegate doesn't work as well and boost creeps up a lot! that's where lots of the HP increase comes from when you remove the converters... it also means you'd better be realy with an FCD and some fuelling mods...

 

peejay, i believe he is refering to a n/a. he stated the car was an 86 and they had no turbos in 86

 

Sorry... wasn't paying attention to where he was from.

 

LOL

UMMM is that a real pic in your avatar?? If it is, how much did a reabuild cost ya?? or did you have look with that over rev

lol