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Do equal length runners matter for a turbo header?
https://slantsix.org/forum/viewtopic.php?f=30&t=65434
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Author:  SpaceFrank [ Sun Oct 18, 2020 11:20 am ]
Post subject:  Do equal length runners matter for a turbo header?

I'm design a new header for the Race Dart that will go directly from the head to a T3 flange. My preference is to keep it as compact as possible and not worry about keeping the individual runners equal length. I assume the whole idea of phasing your exhaust pulses becomes pretty unnecessary because the back pressure is dominated by the effect of the turbo, but I don't really know. We're using a pretty damn big turbo (WH1C), and spool-up time is a concern. Would there be a significant benefit to matching the runner lengths?

Author:  ProCycle [ Sun Oct 18, 2020 11:28 am ]
Post subject:  Re: Do equal length runners matter for a turbo header?

It's my opinion that header lengths don't really matter. As you said, the drive pressure negates any scavenging effect from the header pipes. As I recall, if your turbo has a twin scroll turbine housing it's beneficial to feed 1,2 & 3 into one side and 4, 5 & 6 into the other.

Author:  Dart270 [ Sun Oct 18, 2020 1:28 pm ]
Post subject:  Re: Do equal length runners matter for a turbo header?

Yep, I would not worry. Clustering cyls like Procycle says could help if you have a two-hole hot side input flange on the turbo.

Lou

Author:  MadScientistMatt [ Mon Oct 19, 2020 11:31 am ]
Post subject:  Re: Do equal length runners matter for a turbo header?

The exhaust in a turbo car is at much higher pressure than in a normal header, and so the velocity is a lot lower. I haven't seen many dyno results firsthand, but I've heard turbo engine builders claim that the primary concern they have with header design is short tube length over equal length or even tuning the tubes to an optimum length.

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