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Big Bore Exhaust Q's
Posted: Thu Oct 08, 2009 1:41 am
by forbesg
I've seen it posted a number of times & also seen many Brit. vendors talk about big bore exhausts for the minor. What size (OD) is considered big bore for a minor?
I'm guessing 2" (~50mm).
I'm considering building my own (due to cost), can get 1.6mm mild steel pipe for a very reasonable price.
Does anyone have any pictures of one at the rear, to give me an idea of what it would look like.
Posted: Thu Oct 08, 2009 8:13 am
by PSL184
We use 1.5" over here as a "big" bore

Posted: Thu Oct 08, 2009 9:45 am
by bmcecosse
I made one - just followed the route of the standard pipe - but in larger bore pipe! I happened to have a suitable Cooper S straight through silencer - it's fitted in the normal place under the passenger footwell.
Posted: Thu Oct 08, 2009 9:58 am
by Stig
I think mine's about 1.5" (40mm), but to be honest it's not the pipe that's the main restriction, it's the standard silencer.
When I fitted mine the new pipe was damaged in transit but I found that the old narrow bore pipe fitted inside (rather than outside) the output pipe of the new silencer. I ran it like that for a week or two (LCB - new silencer - old pipe) until I got a replacement for the pipe. I didn't notice much difference in performance when I changed the pipe to the bigger one - nothing like as much as the change to HIF38 carb, LCB and better silencer anyway.
That's the Grumpy's large bore system, it's not significantly louder either.
Posted: Thu Oct 08, 2009 11:57 am
by jonathon
1.5" is fine , 2" is too large . PM sent
Posted: Fri Oct 09, 2009 6:47 am
by forbesg
Awesome
Thanks Lads.
-Grant