hashsi

How much HP can i get from just installing an intake and catback exhaust on a GTU that is not turbo?? And with a header maybe?

t_mak@mail.plymouth.edu

7hp or so

hashsi

Thatz it??? I could have sworn that i read somewhere that the gains would be like 28+hp from the exhaust only???

Mykl

28 hp from a cat-back? Where did you read that?

Mazdatrix advertises a 28 hp gain from their full, dual uncollected system. However, this isn't just the cat-back, it includes a header and a presilencer to go with it.

Chances are you're actually losing power with a cone intake due to all the heat from the exhaust that gets to it.

I'd say that even 7 hp is a bit more than you would get.

The Ace

Whoah take it easy. Even on my TII a catback + downpipe will not give any more than 15-20HP. Huge gains can be obtained on a turbo with a full exhaust, but that's not legal... So only choice is to keep the main cat, and replace everything else. On a NA though you need the backpressure, so the gains are not as dramatic as in a turbo...

Mykl

He doesn't need backpressure, his car is an '89, the secondary ports are actuated by the air pump. He can run whatever kind of exhaust he wants.

SpeedRacer

With headers/catback, and cone intake you'd probably pick up close to 20hp, although you might burn up your cats with headers. Get rid of your cats and you could probably pick up 25hp(total with headers/catback/intake)

hashsi

if i take off the cats won't the car be too loud??? and will i be able to pass emissions?? I drive about 100 miles a day, so i don't want to be constantly annoyed by the noise.

Green

86 Base here... I don't have any cats... and I don't have one of my mufflers right now (crappy stock one rusted off haha)

My ports open (I'm pretty sure... or DAMN my car would FLY with em open =) I will double check on those hehe... car feels the same as it did before I rebuilt it..faster maybe.. but I'm sure the ports are opening cuz I have a little hesitation

and without my muffler, it has a nice TONE to it, but then it has another NASTY noise with it... you know, that HICKISH no muffler noise haha but I'm used to it now dangit=( can't afford new exhaust yet...

SpeedRacer

If you remove your cats and keep your stock catback, then you will ok as far as noise is concerned. My car is very quite when putting around town, I can go unoticed easily, but when I get on it, it sounds beautiful, and still not TOO loud. If you remove your cats AND install a catback, then yeah, it will be loud. And without a catylitic converter, you will not pass emissions.

Sebring7

Well like my sig says, that is the exhaust system I used to have before I had to switch over to the TII exhaust system from the Y-Pipe on up to the mufflers. My system was LOUD as hell. It was louder than any other APEXi N1 system out there. Even a guy with a 89 GTU that I met couldn't believe how loud mine was compared to his. Anyway, I got a REAL big gain from my system. I'd say anywhere from 20-25hp. On my old car (86 GXL) my mods were:

Racing Beat Single outlet header, 2.5" straight pipe to 2.5" Y-Pipe to 2.5" Sebring exhauts.
APEXi SuperFlow Intake
Working 6 ports!

With these mods alone I felt a substantial gain! I would say it put me at about 170fwhp.

So with what you just said I'd say you'd have a nice 15-20hp gain since you would have a cat on there.