jamesjedi

Hi,

Thanks, as always, for the input. Is the following statement accurate?

After searching posts on exhausts, it looks like there is no noticible gain from changing the pipe to a larger diameter, or replacing the muffler with a higher flowing one. It seams that the only worthwhile gain lies with the cat.

I do not wish to drive on the street without the cat. As a note of interest, I talked to Steve Wong a few years ago, and he said that replacing the cat on a Carrera 3.2 with a Dansk Sport cat (very expensive), that is constructed with a metal substrate core (as apposed to a ceramic core), did not change the power output when compared to a premuffler.

jamesjedi

I forgot to mention that my cylinder head has been ported and polished, and I have an FRWilks chip.

krystar

that's pretty much what most ppl agree on.

bigger doesn't equate to better when it comes to NA exhaust. running a 3" exhaust pipe will only cool and slow down the exhaust gases, reducing scavenging effect and exhaust gas velocity.

jamesjedi

It is nice to see that it is a mod that does not cost very much. I will probably replace the cat.

Thanks

Potomac-Greg

I've got two cat-back systems, one with a full muffler and one with a resonator. Both bolt on after the cat. With the more open system, I do see more top end power/speed on track. It's minor, but noticeable. So the cat might be a restriction, but so is the muffler.

My view is that I'll keep the cat on even though my car has "historic" plates and is not subject to inspection. I'm not a tree hugger, but I do want to be responsible to Mother Earth.

jamesjedi

For whatever it is worth....I agree about keeping the cat. It does not seem very responsible to omit the cat for a gain that may not be noticeable for street use. Also, I doubt that I would ever have a better "track day" because of a deleted cat.

James

M758

I believe so. I don't have a street legal NA right now, but when I did I never considered pulling the cat or changing the muffler. On the steet the NA is not powerhouse and doing the exhaust does not change that fact in anyway. The gains are ony slightly noticeable on a track so on the street I would not notice. Heck you can probably see a bigger change in acceleration on the street empy fuel tank vs full as compared to exhaust changes.

RedRose

It's true :P I notice changes when I use different gas stations due to 2 octane higher gas... Or am I crazy?

M758

you are crazy.

The 84 944 will run on 87 gas. No need for any more octane for a stock motor.

roman944

you are like me then

my car would NOT run on 91! it would stutter and do all kinds of weird things

mixed some 87 to make it close to 50/50 mix (3-4 gallons of 91 and added about 4-5 gallons of 87) and the car started running perfect again

from that point on I stuck with 89 and happy

ritzblitz

Id bet you can benefit from a slightly larger diameter if you also have a bigger cam.

944CS

everything about the 944 is geared towards low end torque. If you change the exhaust and leave the cam stock, you won't see any gains. If you change the cam and leave the exhaust stock, you'll see a little but not as much as if you changed both.

Also this is the reason why putting in a test pipe doesn't do anything for power. The exhaust still has to go through this