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Old 09-05-2018, 09:37 PM   #1
loud_sam
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Default Best exhaust diameter size

Evening all,

I have a haywood & Scott exhaust manifold 4-2-1 then reduce down to 2 inch exhaust system with 2 silencers but I think its sapping some power from my the engine.

I was wondering what other people are using what diameter exhaust are on there mini's so I could maybe pinch some ideas.

Thanks Sam

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Old 10-05-2018, 05:47 AM   #2
fynnbar
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You ought to have 2-1/4" minimum, right through, with a B18. This will give you over 20% more flow.
I'm running 2-1/4" with my B16
What size is the '1' part on the 4-2-1 ?

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Old 10-05-2018, 12:09 PM   #3
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2.5" all the way from the manifold on my B18C.
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Old 10-05-2018, 04:23 PM   #4
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Thanks lads,

The 1 part of the manifold I 2.5 inch if I remember correctly but I do remember when I had the exhaust made it was reduced down to 2 inch. I have wanted to change the exhaust so this is my excuse a nice new 2.5 inch will do

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Old 10-05-2018, 11:29 PM   #5
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It would be nice if you could find out if your "feeling"
Is fact, ?
I'm leaning towards 2 1/4 coz the lads say so !
How much more do you want with that lump? Greedy BuggeR, only joking ,
I'm making a 2 inch s,s and what's bothering me is approx 1/4 inch of my pipe is below floor level under the handbrake
Guides at frame, I don't feel good about that,
I'm going to skwash it but I'm interested how you deal with that ,
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Old 11-05-2018, 08:11 AM   #6
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2.5" for me.
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Old 11-05-2018, 01:14 PM   #7
Beanman
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Stock Integra Type R (JDM & USDM) = 2.25"

Since I dont plan on messing with my engine I also went with 2.25
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Old 12-05-2018, 04:39 PM   #8
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I did 2.5 SS front to back in mine
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Old 12-05-2018, 07:50 PM   #9
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Quote:
Originally Posted by ardonfast View Post

How much more do you want with that lump? Greedy BuggeR, only joking ,
As much as i can

I have been measuring today and the manifold is 2.5 inch so I'm going with a 2.5 inch exhaust and it should tuck up nicely and not hang down to much so hopefully it won't scrape.

How many silencers are people running on there exhaust? I was thinking about running 1

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Old 06-07-2018, 02:39 AM   #10
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The sizing of the exhaust can become quite an expansive subject, you would need to know loads of values for different data. A Quick google about exhaust system sizing throws up some generalisations and they point towards a 2.1/4" system coping up to 185 Hp Max and 2.1/2" System up to 232 Hp max. Given that your pipe coming out the collector has a 2.1/2" diameter, it is best to match that to avoid a choke in the system, which would definitely sap power. The b18 should be powered correctly to work with the 2.1/2".
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