| Author | Topic |
|---|
Location:
Sydney
Registered:
May 2002
|
|
Exhaust Question
|
Fri, 04 April 2003 23:59
|
 |
Hey all
Im getting mixed stories here
Ive been told that if theres not enough backpressure in ones exhaust system....that it can damage the exhaust valves...
another says this isnt true
whats the deal ???
Ta
Mani
|
|
|
I supported Toymods
Location:
melbourne
Registered:
June 2002
|
|
Re: Exhaust Question
|
Sat, 05 April 2003 00:20
|
|
the thing that has been stressed with this subject before (the only thong i kindof believe anyway) is its not really "back pressure" you are after, but having exhaust pipe that is too big a diameter will mean the exhaust gas will cool down before it leaves the pipe, which leads to power loss as the engine has to "force" the exhaust out, rather than it "rushing out by itself" (remember, exhaust valves are always smaller than intake, fot this purpose, in a 20 valve 4age there are two exhaust valves, 3 intake etc)
Now, to try and answer the actual question,
as for damaging the valves, id say the way you would damage exhaust valves is by overheating them, i would gues that the exhaust config doesn't have too much too much to do with it, but if anything i would say that having too much "back pressure" would be bad, as the echaust gas would hanga around for too long, and heat up the valves for longer. if anything, a low back pressure system would be better.
but as a (dodgy) rule
1.6 litre engine 2 inch
2.o litre engine 2.125 inch (thats 2 and a 1/4)
3.0 litre 2.5 inch (strting to guess now)
what is much more important to the exhaust valve damage is a/f ratio and spark timing, maybeye exhaust cam timing too, but i think this wouldn't matter too much.
|
|
|
I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
|
|
Re: Exhaust Question
|
Sat, 05 April 2003 00:42
|
|
|
and add 0.5" if it's forced induction... I'd hate to see a 2jz-gte running around with a 2.5" exhaust
|
|
|
Location:
Melbourne
Registered:
May 2002
|
|
Re: Exhaust Question
|
Sat, 05 April 2003 11:12
|
|
The bigger the exhaust the more power.
Thre more free flowing the more power.
The louder the more you'll grow to hate the EPA.
|
|
|
Location:
Sydney
Registered:
May 2002
|
|
Re: Exhaust Question
|
Sat, 05 April 2003 13:52
|
|
fooz
u may get more power up top
but u lose torque down-low
so once again its a balance of torque and KW
depending on what u want
Ta
Mani
|
|
|
I supported Toymods
Location:
melbourne
Registered:
June 2002
|
|
Re: Exhaust Question
|
Sun, 06 April 2003 02:39
|
|
yeah, my dodgy size list was for NA cars. with a turbo, usually use the biggest pipe you can afford or fit under your car.
there may be a downside to having massive big pipes on a turbo, but i don't know what it is.
|
|
|
Banned member
Location:
Brisbane
Registered:
May 2002
|
|
Re: Exhaust Question
|
Sun, 06 April 2003 02:45
|
|
| manipulate wrote on Sat, 05 April 2003 23:52 |
fooz
u may get more power up top
but u lose torque down-low
so once again its a balance of torque and KW
|
sounds like you answered your own question !
on a mild 22re i used to run i had a straight through 2.5 system into a dynomax super turbo muffler, as i didnt really care about low down torque there was already shitloads, and that sort of muffler has a nice not is reasonably quiet until you start thrashing the car about
|
|
|
Location:
Melbourne
Registered:
May 2002
|
|
|
Location:
Sydney
Registered:
May 2002
|
|
Re: Exhaust Question
|
Sun, 06 April 2003 04:21
|
|
| celicamad85 wrote on Sun, 06 April 2003 12:45 |
| manipulate wrote on Sat, 05 April 2003 23:52 |
fooz
u may get more power up top
but u lose torque down-low
so once again its a balance of torque and KW
|
sounds like you answered your own question !
|
No....my question was.....is there damage done to the exhaust valves, is theres not enough back pressure in an exhaust system
fooz....resonators and cats create restriction, bigger exhausts reduce backpressure.....similar but different
Ta
Mani
|
|
|
