exhaust bore size

1. PaulW91 Infrequent Poster Joined: Jul 2008 lanarkshire Posts: 206 2002 bodied saxo vts 1.8t Audi A4 S-Line CBR600R

   #1 18th October 2010, 07:04

   just wondering if anyone could help me I'm going to be getting a new stainless steel exhaust made for my car once I get it back on the road and it'll be running gsxr throttle bodies and phase three cams with four into one manifold and have been told to get a two inch system made to get the best out of it but the plans are to go boosted in the near future so would I beable to get a two and a half inch system made just now or would that have a negative effect on performance just now?
   thanks for any help
2. PaulW91 Infrequent Poster Joined: Jul 2008 lanarkshire Posts: 206 2002 bodied saxo vts 1.8t Audi A4 S-Line CBR600R

   #2 19th October 2010, 04:59

   nobody tell me anything?
3. KamRacing Saxperience Addict Joined: Nov 2006 A farm shed in Aylesbury Posts: 14916 Corolla AE86 Peugeot 205 B18C (in bits)

   #3 19th October 2010, 10:52

   if you go 2 1/2" you will certainly loose gas velocity in your n/a setup
4. Jungle Established Member Joined: Sep 2008 Sheffield Posts: 1206 106 Rallye Turbo

   #4 19th October 2010, 11:06

   Besides, whats the piont in spending money doing a ITB set up if you plan on boost?
5. burgerfeet Infrequent Poster Joined: Oct 2010 Bridgend Posts: 231 VTS 2002 - well the Mrs does

   #5 19th October 2010, 12:02

   The bore size of an exhaust in a normally aspirated engine is critical. Too small or too big will affect you performance ie loss. Forced air induction, eg turbo doesn't really matter.
6. axsaxoman Saxperience Forum Bum Joined: Jan 2003 Scotland Posts: 3380

   #6 19th October 2010, 12:14

   Quote:

   Originally Posted by burgerfeet The bore size of an exhaust in a normally aspirated engine is critical. Too small or too big will affect you performance ie loss. Forced air induction, eg turbo doesn't really matter.

   Hi,
   I agree with most of what you are saying ,but with s/c it is same as an n/a car --ex size + primary lengths+ postion of first box do matter-
   -turbo no --as big as you like -but too small could be a problem

   1 user thanked this post: PaulW91
7. burgerfeet Infrequent Poster Joined: Oct 2010 Bridgend Posts: 231 VTS 2002 - well the Mrs does

   #7 19th October 2010, 14:26

   Quote:

   Originally Posted by axsaxoman Hi, I agree with most of what you are saying ,but with s/c it is same as an n/a car --ex size + primary lengths+ postion of first box do matter- -turbo no --as big as you like -but too small could be a problem

   I agree with that also. Didn't mention super charging as I didn't thing it would be a consideration. Then again blower was mentioned. Was just thinking is was a loosely coined phrase for turbo. If I recall, too big an exhaust with a super charger robs it of peak boost.
8. burgerfeet Infrequent Poster Joined: Oct 2010 Bridgend Posts: 231 VTS 2002 - well the Mrs does

   #8 19th October 2010, 14:27

   Quote:

   Originally Posted by burgerfeet I agree with that also. Didn't mention super charging as I didn't thing it would be a consideration. Then again blower was mentioned. Was just thinking is was a loosely coined phrase for turbo. If I recall, too big an exhaust with a super charger robs it of peak boost.

   Nope, blower wasn't mentioned....boost was though so turboing I guess.
9. PhillipM Infrequent Poster Joined: Feb 2010 Rotherham Posts: 82

   #9 19th October 2010, 16:26

   You can breathe pretty well through a 2" exhaust up to about 180 or so - it depends how much power you think you'd be running when your FI?
   I imagine your thinking about a supercharger rather than a turbo give you'd have to alter the manifold and exhaust anyway for the latter.
10. PaulW91 Infrequent Poster Joined: Jul 2008 lanarkshire Posts: 206 2002 bodied saxo vts 1.8t Audi A4 S-Line CBR600R

    #10 19th October 2010, 20:07

    thanks for the info everybody