Simple Exhaust Question - 944 NA

jamesjedi · 11-05-2009, 12:10 PM

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 · 11-05-2009, 12:34 PM

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

krystar · 11-05-2009, 12:36 PM

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 · 11-05-2009, 12:41 PM

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 · 11-05-2009, 12:41 PM

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 · 11-05-2009, 12:56 PM

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 · 11-05-2009, 01:16 PM

Quote:

Originally Posted by 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 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 · 11-05-2009, 01:34 PM

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

M758 · 11-05-2009, 02:19 PM

you are crazy.

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

roman944 · 11-07-2009, 02:07 AM

Quote:

Originally Posted by RedRose

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

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 · 11-07-2009, 01:46 PM

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

944CS · 11-07-2009, 03:11 PM

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

11-05-2009, 12:10 PM	#1
jamesjedi User Join Date: Jul 2007 Posts: 61	Simple Exhaust Question - 944 NA 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.

11-05-2009, 01:34 PM	#8
RedRose Addict Rennlist Member Join Date: Sep 2008 Location: Iowa, USA Posts: 468	It's true :P I notice changes when I use different gas stations due to 2 octane higher gas... Or am I crazy? __________________ Joel Mason 1984 944 -- Needs new paint and bodywork!

11-05-2009, 02:19 PM	#9
M758 Addict Rennlist Member Join Date: Aug 2002 Location: Phoenix, Az Posts: 12,432	you are crazy. The 84 944 will run on 87 gas. No need for any more octane for a stock motor. __________________ Joe P. 88 944 Turbo S - 100% Stock ++++++++ 84 - 944 Spec #94 Red/White Arizona Region 944Spec Director - Az 944 Spec Champion 02/03, 2006 - 2nd Az Region 944 Spec 2003,2004,2008 4th - 2009 NASA Nationals - Fastest 944 spec lap at Miller Nationals - 2.19.282 (Sat Warm-up)

11-07-2009, 01:46 PM	#11
ritzblitz Addict Rennlist Member Join Date: Aug 2007 Location: State College, PA / Quakertown, PA Posts: 1,922	Id bet you can benefit from a slightly larger diameter if you also have a bigger cam. __________________ '83 944... runs

11-05-2009, 12:34 PM	#2
jamesjedi User Join Date: Jul 2007 Posts: 61	I forgot to mention that my cylinder head has been ported and polished, and I have an FRWilks chip.

11-05-2009, 12:36 PM	#3
krystar Addict Rennlist Member Join Date: Oct 2007 Location: Schaumburg, IL Posts: 1,700	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.

11-05-2009, 12:41 PM	#4
jamesjedi User Join Date: Jul 2007 Posts: 61	It is nice to see that it is a mod that does not cost very much. I will probably replace the cat. Thanks

11-05-2009, 12:41 PM	#5
Potomac-Greg User Join Date: Jan 2008 Location: Suburban DC Posts: 1,356	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.

11-05-2009, 12:56 PM	#6
jamesjedi User Join Date: Jul 2007 Posts: 61	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