I see this thread.
Then I see Banzai's dyno gallery has an S5 RX7 ITS car which no porting is allowed, not even port matching. Banzai Racing (Keefer 13B RX-7 Engine Installation) |
Originally Posted by Gilgamesh
(Post 12169067)
I see this thread.
Then I see Banzai's dyno gallery has an S5 RX7 ITS car which no porting is allowed, not even port matching. Banzai Racing (Keefer 13B RX-7 Engine Installation) |
Originally Posted by fidelity101
(Post 12168848)
0-10hp tops, but the peak could be shifted up to 7800-8000rpm I'd imagine because the runners are shorter. However with making the VDI system functional I could gain equal more power likely in the mid range too.
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Originally Posted by peejay
(Post 12169242)
The S5 manifold has way too much surface area and therefore flow restriction to be a good performance manifold, IMO. Although I shouldn't say this until after I sell off my stock of S5 manifolds, I have 3 of them and will never use 'em. Think $200 a set is a fair price? I need to buy tires ;)
The real limitation of the 6 port engines is actually the ports though and not the manifolds. The manifolds, even the S5, can flow enough to support 200 rwhp and the S4 far more than that. The biggest issue lies in the port timing of the 6 port motors. The reason that a 4 port motor typically makes more power and has a smoother power band has to do with the fact that the intake ports, primary and secondary, close at the same time. On the 6 port motors, with the auxiliary ports shut, the secondaries close first and then the primaries. The point of the divided intake manifolds is to take advantage of tuning the return wave pulses to help charge the other rotor just before it closes. The problem is that this closing pulse in the engine does affect the other port in the same rotor as well through the rotor housing. When the auxiliary ports are open, now the primaries close first and the outer ports essentially keep moving. It's a mess. Another neat thing is that the exhaust port size on an n/a is what affects your power peak. It actually flows plenty and if it is going to be opened up, should really only be opened up to what Racing Beat considers a street port exhaust profile. Even a large bridge port can be supported by this. Going larger on the exhaust side only shifts the power band up in the rpm range. If you make a really large exhaust port but don't do much to the intake or manifolds, you'll just have a car that makes lower power everywhere in the rpm range, something that is pretty common. If you make really large intake ports but then use longer, free flowing runners to tune them and keep the exhaust ports mild, you'll make some very nice power everywhere. At this point, dividing the intake manifold into individual rotors that don't cross talk is the best option. For street cars using the stock manifolds, mild porting (no bridging) is best and definitely do very little to the exhaust ports. |
One interesting thing is that I'm seeing the power lay over like mine never did.
I always removed the sleeves and removed the actuator shafts. The actuator shafts represent a large cross sectional area restriction and ALL air to the end housings has to go past them since the main secondaries are under the aux ports. |
well I picked up a caged FC shell I'm going to basically mirror this build but I'm adding a GT45 turbo. ;) and I'm naming what I did with the AUX ports the "Drawbridge Port"......a new build thread will be coming soon..... that is all
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