Tubular intake manifold design - Suzuki GSX-R Motorcycle Forums Gixxer.com
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post #1 of 5 (permalink) Old 08-29-2008, 11:57 PM Thread Starter
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Tubular intake manifold design

I have a question for someone a little more learned in the ways of how any given engine makes its power. For any intake manifold or airbox or possibly on both in the same application you have a common area for air to collect and then be distributed into the different cylinders based on that cylinders vacuum drawing the air in. I have never seen a manifold that has a fixed method of distributing air based on the route that air has to take in accordance with the manifolds design. To give an image like the one I have it's essentially a header used as an intake manifold. Of course I'm not saying that this is as easy as taking a header and using it on the inlet side but merely just to provide a image. Could a design like this be used in a boosted application? The theoretical benefit I see would be a continual uninterrupted path for air to flow. In no way am I suggesting this for a motorcycle application, just asking in general for any internal combustion engine. Thoughts? If you need me to elaborate more I could.
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post #2 of 5 (permalink) Old 08-30-2008, 02:10 AM
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Re: Tubular intake manifold design

If you're asking if anyone has ever turbo'd an inline four bike using a boosted single carb on a manifold...the answer is yes. Mr turbo and hann racecraft did em that way back in the old school bike turbo kit days and it's still done that way in some applications. Some with a plenum like box, and some with a tubular manifold like you're describing, however, the tubes come from a single box plenum chamber in all cases. Nowadays the plenum chanber sits atop the throttle bodies pressurizing the intakes in similar fashion.

There are some motorcycles (non turbo'd) which have a tubular manifold serving up more cylinders than it has carbs too, similar to the plenum x tubular described above. The Benelli six cylinder with four carbs comes to mind. This design can be a nightmare to tune though as the plenum gets excess fuel fogged into it from the 'reversion' from the other cylinders not on the intake stroke.

Anyway, I'm just babbeling here...what exactly is the question ?
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post #3 of 5 (permalink) Old 08-30-2008, 02:15 AM
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Re: Tubular intake manifold design

Boosted applicatons yes. Far as NA goes, different length that you use for runners will change your torque output and where it is on the curve.
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post #4 of 5 (permalink) Old 08-30-2008, 03:35 PM Thread Starter
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Re: Tubular intake manifold design

Boosted applications is where I see it making most sense. If nothing else then simply for air filter usage. Anyways Jon, I really didn't have a specific question and I was just asking about the general subject of this application's usage in an internal combustion engine. I was wanting to know the physical effects of eliminating a plenum or air chamber from the equation, again, namely a boost environment, and using only a tubular design to direct air to the cylinders.

If anyone else is confused here's the path:
pipe fitted over the compressor side of the turbo or centrifugal supercharger goes to

intercooler(optional) which goes to

single throttle body(some applications)

inlet pipe of manifold which is basically a header in reverse dividing in whatever fashion to however many cylinders which goes to

the throttle bodies on an individual throttle body application

Now that I think about it I think there are VW manifolds similar to this that mount the carbs on top. Any other thoughts?
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post #5 of 5 (permalink) Old 09-02-2008, 01:01 PM
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Re: Tubular intake manifold design

Unless you have 4 turbo's, you are still starting with 1 source so the air will have to choose somehow. Too many factors are at play, and 2 different designs may not do much at all, or they may make a huge difference. I am going to lean and say that it won't make too much of a difference unless you are flowing some serious CFM through the engine.
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