Or what makes the runners on a short turbo manifold considered short? I have read through may forums debating runner length, but no metrics of definition.

thoughts?

 

How Long is a Chinaman

 

The compromise between 1) distance from exhaust port to turbo flange and 2) available space to produce a manifold that allow a turbo to to plumbed for exhaust, intake, and wastegate piping helps define short or long runner for a given type of car setup. While very custom / exotic solutions often exists, the readily available product comparisons usually drive the "internet" definition of short or long runner. For most models of RX-7 street cars a manifolds like the TurblownEFR Turbo Manifold or theirT4 Twinscroll FC32 Turbo Manifold would generally be considered short while the Gleaseman FD3S Long Runner Turbo Manifold is consider long, even by its name.

 

The runners on my setup are 15”. So this is a curiosity.

 

the only thing sadder than this thread is me not having anything better to post about

 

why is this thread sad? I prefer some form of metrics. Unfortunately at times theses details are left out.

 

Are you talking about pulse-tuning?
It doesn't seem to be really calculated for in turbo rotaries, beyond maybe guesswork.
You either try as best as possible to mount the turbine housing directly to the exhaust ports to conserve energy (short) or, pretty much anything else for packaging reasons (long)

Im just staying posted in case you and any other big brains weigh in with data and equations and stuff.

 

I have a better question; what are you trying to accomplish? The reason I ask is because generally the only way to tell between short and long is the eye test and marketing. Obviously Turblowns "shorty" manifold (the one I have) is short, and I'd imagine any long tube manifold will be long...I really don't believe there's any other way of explaining it.

 

in 2007, how long the manifold was, was a big arguing point, but in 2021 you want the manifold that fits, and flows well while controlling boost, which is that part that matters

in theory a shorter manifold has less heat losses, and a long one may have some tuning, other than that its just packaging.

short would probably be like this HKS T51 manifold, can't be more than 8"


long is the original BMW manifold, which is basically just a header with the turbo as the collector. they claimed like 50hp or something, but don't forget they had a side pod to fill too...lets say more than 15"?

 

What do the girls say - short and fat, is where it's at!

 

I was waiting for somebody to go there...

I've had the scene from Braveheart "some men are longer than others.." "ah, your mother's been telling stories about me again, eh?" in mind each time I read the title 😂

 

length alone is kind of a meaningless metric, it doesn't truly define how it will measure up in totality.

as stated; metrics/details are being left out, perhaps more of them than seem to be realized.
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Short... but stubby like a tuna can I say!!


A-Spec 'stubby'

 

aware of one conceptually at less than 3” C-L between the flange faces, it will have to be cast or 3D printed though.

.

 

i had a cartech one for the 13B 6 port that was about that thickness, its like they made the one, and we just trade it amongst ourselves...
or two, there was the obligatory guy who said he made 450hp using that manifold

it puts the turbo low enough so you can keep all the 6 port and emissions jazz

 

Here is the manifold that triggered my question. its runners are 15" long. picture were taken during a test fit. It has since been finished and returned. Over all I'm really pleased.

 

familiar with it; the G30/Renesis thread on here is more or less a variation of it, but it’s essentially a log manifold and obviously one centerline flow path is way longer than the other. The one I referred to is asymmetrical equal length and fully divided T4. The flow path centerline of each port is less than 3” through the manifold. It’s for an REW in an RX8 chassis though and likely won’t work on an RX7 because of the chassis differences. Turbo limited too; a Garrett G35-900 might fit, but is really pushing it.

meh: now that I think about it, may have miscalculated. Let me double-check.

yeah my bad; correct port C-L length is 3.34” with a 2.6” flange-flange manifold width. As I was looking at your pic it dawned on me the 13B exhaust port - T4 divided port spacing didn’t match up with less than 2.5”. Correctly stated, less than 3.5” …
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