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Guest Message by DevFuse

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Exhaust out the hood, joint it or separate?

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3 replies to this topic

#1 Phizinza


    Yip yip

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Posted 29 October 2013 - 02:11 AM

We're looking at changing the exhaust setup on our EA81 race wagon. We want to get it out of being bashed and because the radiator is in the back now we were thinking of brining the exhaust forward and up to the hood or maybe out the side where the jack used to mount.


Question is with only around 2ft of pipe on each head would it need to be joined as in like the y-pipe joins it or would running it separate not harm performance?


At the moment we just run the y-pipe, nothing else and it runs great. But after last race the left hand header got flattened to around 15mm thick in one section.




#2 el_freddo


    Eat, Live, Breath Subaru

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Posted 29 October 2013 - 04:47 AM

G'day Phiz,


Why not make an exhaust similar to a turbo setup but turn it around to pop out the bonnet where you've said - this way you can still join it and have the bash plate protect it where it passes in front of the sump.

I think you don't have to join them for performance, rather for comfort so you don't get a crackle or thrumming sound (ever hear the Holden 253 V8 with separate twin exhausts crackle?) - but that shouldn't be an issue for racing.  



#3 Phizinza


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Posted 29 October 2013 - 06:07 AM

From what I understand the headers joined together are tuned to run better at certain RPMs. This is achieved by the exhaust pulses fron one side of the engine effectivly pulling the exhaust out the other side as it escapes the exhaust pipe. This is why equal length headers are usual better for performance. Its no problem to join them, but easier if it wasn't needed our wouldn't help hp.

#4 Uberoo


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Posted 29 October 2013 - 01:31 PM

run the exhaust out the side,up through the hood would obstruct visibility too much.


As for joining the pipes I have always heard that you pick up a bit more low end torque with them joined, separate it tends to be a bit more peaky.

Edited by Uberoo, 29 October 2013 - 01:36 PM.

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