I just bought some Ausie Speed Dutra duals from Gill Welding (nice people). Is there a formula for calculating the length of the pipes before they go into the collector?

That length is proportional to where in the RPM band you want the peak scavenging for torque. I put my Y at about 42” which was about 3500 RPM. you will never know exactly without a dyno and testing but my modeling said between 40 and 60 should put it in the nice highway RPM for peak torque when passing and such.

Jim

With Dutras, I'm not sure it will matter much, but putting it further back is likely better and that 42" number sounds about right. When I use headers, I put the Y junction 4 - 8" behind the trans X member.

Lou

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Greg

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