Turbo Manifold

[T66]

Hi Guys. How important is it that all 4 (4 cylinder) channels or ducts are the same length on a Turbo Manifold. The reason I ask is that I saw a HKS Rotary (13b) Turbo Manifold and the one channel was a lot shorter than the other.

[CBFryman]

equal length means equal pressue on all cylenders...

[CBFryman]

exaust back pressure and delta drop that is

[Schister66]

a 13b is a rotary......they don't follow the same rules as everything else......

[nissanfanatic]

Equal length will not make much of a difference at all in power or response. It is only in theory that equal length will increase response. Tubing diameter would be more of a thing to worry about in regards to the characteristics mentioned.

[2.2 Straight six]

really ? so the thing about equal length really helping the engine is a myth ? i always understood that the diameter/flow capacity would be more influential, but with the equal length thing, i thought it would make a great deal of difference to engine, an was always told i was wrong.

[Black Lotus]

Originally Posted by nissanfanatic

Equal length will not make much of a difference at all in power or response. It is only in theory that equal length will increase response. Tubing diameter would be more of a thing to worry about in regards to the characteristics mentioned.

Theory works most of the time. How well a theory works depends on how you've misapplied the other theories in close proximity(I just made that up!).
Equal length? On-boost it may not make much of a difference, but off-boost it does.
But then again this thread is about rotarys......

[T66]

Originally Posted by Black Lotus

Theory works most of the time. How well a theory works depends on how you've misapplied the other theories in close proximity(I just made that up!).
Equal length? On-boost it may not make much of a difference, but off-boost it does.
But then again this thread is about rotarys......

The intention of this thread is to establish whether equal length pluming on an exhaust manifold is the Alfa and omega. This thread is not about rotary’s. I simply used it as an example. Thank you for the info, why would it not be an issue on boost?

[2turboimports]

You asked a question about equal length headers siting the ROTARY engine you saw them on or whatever. That's why everyone is talking about rotary this and that.

I would think it would make a bit of difference on boost since there would be that little bit more flow in the exhaust allowing the air to escape in larger amounts.
Unequal length tubing would have that bit more restriction somewhere which would increase the pressure in the exhaust. Pressure isn't something you really want in the exhaust, it's more flow that you are usually after. There are exceptions though.
But then it also goes back to how long the tubing is, how many bends, etc etc.

[Jet-Lee]

on N/A it matters, harmonics and all that jazz.

on Boost, it doesn't matter.

[T66]

Originally Posted by T66

Hi Guys. How important is it that all 4 (4 cylinder) channels or ducts are the same length on a Turbo Manifold. The reason I ask is that I saw a HKS Rotary (13b) Turbo Manifold and the one channel was a lot shorter than the other.

My first language might not be English but if you read my first sentence you will see my question and the rest of the gentlemen seemed to understand my question. I used the rotary application as an example.

[nissanfanatic]

http://sdsefi.com/techheader.htm

[T66]

nissanfanatic, your input is much appreciated.

[KiwiBacon]

Equal length keeps the exhaust pulses arriving at regularly spaced intervals.
It's important on a NA engine, it's important on a boosted engine too. But on a boosted engine it's easier to mask shortcuts in design and fabrication by just turning up the boost.

Then you get applications like Subaru. Because of packaging issues you can either have shorter, unequal length pipes or longer, contorted equal length pipes. In a siutuation like this there doesn't appear to be an advantage either way. The longer ones have more volume and more heat loss which offsets the advantage of equal lengths.

BTW some 4 cyl turbo manifolds arrange pipe lengths to combine pulses, rather than equal spacing them.

[Schister66]

if you want to start a new thread about this....do it, but don't bring back one that's almost a year old