Equal length turbo header

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sidemarkers
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Re: Equal length turbo header

Post by sidemarkers » Tue Dec 26, 2017 2:58 pm

I've seen equal length merged headers on naturally aspirated street dubs. To think that it might be just as beneficial on a turbo making 20 lbs of boost is odd?

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Wally
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Re: Equal length turbo header

Post by Wally » Wed Dec 27, 2017 3:58 pm

sidemarkers wrote:
Tue Dec 26, 2017 2:58 pm
I've seen equal length merged headers on naturally aspirated street dubs. To think that it might be just as beneficial on a turbo making 20 lbs of boost is odd?
Nope: tests (on several watercooled japanese models) by a rather well-known turbo header builder revealed that equal length made more hp all over the rev range as opposed to a log style unequal length header.
There is also sound theory behind it, based on most of the N/A exhaust events like you mention iirc.

I strongly believe in equal length, even more then exhaust length on a turbo for quicker spool.
Still, its difficult wrt space constraints as we all know, but if you have a choice...i'd go for EL.
T4T: Type 4 Turbo engine, under construction

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petew
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Re: Equal length turbo header

Post by petew » Wed Dec 27, 2017 7:33 pm

Wally wrote:
Wed Dec 27, 2017 3:58 pm

Nope: tests (on several watercooled japanese models) by a rather well-known turbo header builder revealed that equal length made more hp all over the rev range as opposed to a log style unequal length header.
There is also sound theory behind it, based on most of the N/A exhaust events like you mention iirc.

I strongly believe in equal length, even more then exhaust length on a turbo for quicker spool.
Still, its difficult wrt space constraints as we all know, but if you have a choice...i'd go for EL.
See I believe that, but i'd ask these questions...
1. How much more power across the range?
2. How much extra cost?
3. How much extra space?

Which is why log/unequal length systems are more popular.

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sidemarkers
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Re: Equal length turbo header

Post by sidemarkers » Sat May 26, 2018 4:47 am

seabeebuggy wrote:
Tue Dec 26, 2017 12:14 am
To me, I don't understand how you can have scavenging when you have back pressure. Add a turbo to spin at the end it really changes things. sounds like tuning.
About 95% of true daily driving is non-boost. I'd say that basically all driving besides maybe hard acceleration would benefit from the scavenging of a properly designed equal length, smooth radius, merge collector header.

Tuning is a broad term which also is relevant to turbo headers. If an engine has a turbo header that has a runner that is 3 feet long and another runner which is 8 inches long it will create a noticeable imbalance. The short runner will spike in pressure under boost much faster than the longer runner and cause more reversion forcing spent exhaust back into the chamber diluting the incoming air/fuel mixture.
Last edited by sidemarkers on Sat May 26, 2018 11:29 pm, edited 2 times in total.

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petew
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Re: Equal length turbo header

Post by petew » Sat May 26, 2018 5:55 am

I guess it's a more marked problem on horizontally opposed motors, specifically VW type 1. Subarus and type 4s issues won't be so acute due to the adjacent, downward pointing exhaust ports.

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sidemarkers
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Re: Equal length turbo header

Post by sidemarkers » Sat May 26, 2018 10:22 pm

The design I am working on should address all these issues

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