discodom90 · Apr 30, 2013

Hi guys,

As per the title really. Been offered a stainless system for ridiculously cheap from a mate and its come off a v8. I think the bore size is different? Will it be worth getting to make it fit or will it do more harm than good having a bigger bore from down pipe back?

Thanks in advance!

jamesmartin · Apr 30, 2013

bore size wont hurt ,the bigger the better,but you be better get a system that fits

discodom90 · Apr 30, 2013

jamesmartin said:
bore size wont hurt ,the bigger the better,but you be better get a system that fits

Why would it not fit? Are they a different shape under the car?

jamesmartin · Apr 30, 2013

discodom90 said:
Why would it not fit? Are they a different shape under the car?

yes ,silencers differ too

discodom90 · Apr 30, 2013

Ahhh okay thanks, I'll probably give it a miss then.

thebiglad · May 1, 2013

See the pictures:

Jongould · May 1, 2013

jamesmartin said:
bore size wont hurt ,the bigger the better,but you be better get a system that fits

Not true I'm afraid, bore size is very important, exhausts are tuned to each engine and unless someone has worked out whats what then changing from this system will usually result in a decrease of power (changing silencers is generally OK, its all about bore size and exhaust gas velocity). Basically you want the exhaust to pull the gas out at the same frequency as the engine is working, getting the velocity just right so that it is in sync is what gives maximum power, a big bore means plenty of flow but it will be too slow, a small bore will be faster but the flow rate will be right down...

Good article on the science, I have an understanding of the principle but couldn't quote the math without looking...

http://www.miata.net/garage/KnowYourCar/S4_Back.html

dyte · May 1, 2013

Jongould said:
Not true I'm afraid, bore size is very important, exhausts are tuned to each engine and unless someone has worked out whats what then changing from this system will usually result in a decrease of power (changing silencers is generally OK, its all about bore size and exhaust gas velocity). Basically you want the exhaust to pull the gas out at the same frequency as the engine is working, getting the velocity just right so that it is in sync is what gives maximum power, a big bore means plenty of flow but it will be too slow, a small bore will be faster but the flow rate will be right down...

Good article on the science, I have an understanding of the principle but couldn't quote the math without looking...

Technos Know your car Series #4

its a tdi it really wont affect it

Jongould · May 1, 2013

dyte said:
its a tdi it really wont affect it

It will although not to a point you will notice too much difference, its not so essential on turbo cars as the pulse-pull affect is pretty much lost after the turbo anyway....

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