Intake manifold construction

drewski86 · 07-09-2009, 10:47 PM

http://www.rx7club.com/showthread.ph...ghlight=intake

This will get you started. If you do the math it will get you close enough, but you will want to plan on making adjustments if you want to pull all you can out of it; every motor is going to want something different. Don't expect to get it right the first time, but close may be sufficient for your needs.

The throttle body needs to be big enough that it's not a restriction, but not too much bigger.
By multi venturi to you mean multiple injectors?
The plenum should be shaped that each rotor gets equal amounts of air. Size depends on that application but I would guess around 1-1.5 liters.
Runners should be round since the stock lower manifold will change the shape for the ports. If you want a small taper before it hits the lower manifold will increase velocity, but you don't want to go too extreme. Length is going to depend on the application, and remember, the primaries and secondaries are going to want different lengths but you want them tuned to the same RPM.

Hopefully that will get you started. Keep in mind, all this is going to do is point you in the right direction. Testing is where you're going to get answers. Fortunately since you're turbo you can add boost to overcome a poor manifold but that will only get you so far depending on how poor the manifold is.

07-09-2009, 10:47 PM	#2
drewski86 Slow Join Date: Jun 2008 Posts: 38 Rep Power: 0	http://www.rx7club.com/showthread.ph...ghlight=intake This will get you started. If you do the math it will get you close enough, but you will want to plan on making adjustments if you want to pull all you can out of it; every motor is going to want something different. Don't expect to get it right the first time, but close may be sufficient for your needs. The throttle body needs to be big enough that it's not a restriction, but not too much bigger. By multi venturi to you mean multiple injectors? The plenum should be shaped that each rotor gets equal amounts of air. Size depends on that application but I would guess around 1-1.5 liters. Runners should be round since the stock lower manifold will change the shape for the ports. If you want a small taper before it hits the lower manifold will increase velocity, but you don't want to go too extreme. Length is going to depend on the application, and remember, the primaries and secondaries are going to want different lengths but you want them tuned to the same RPM. Hopefully that will get you started. Keep in mind, all this is going to do is point you in the right direction. Testing is where you're going to get answers. Fortunately since you're turbo you can add boost to overcome a poor manifold but that will only get you so far depending on how poor the manifold is.