That is a very good point about flow reversion when the throttle plate is closed. I hadn't thought of that.

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JP
GT4DC Treasurer

Grey St185 RC
Silver BMW E46 M3
Multicolour yawn Honda VFR400
Silver Honda Civic Type-R

More very useful information there DJ. ITB Vs single TB on the plenum explanation makes perfect sense to me


I can't help but think Mr Bell has missed a bit of the explanation. I still can't get my head around what I'm thinking but I've got a feeling that a little overlap will help lower exhaust manifold pressure by allowing some flow through the inlet and hence reducing the load on the hotside wheel.

The other thing is theory is great and all that but results rule. The cosworth scene sat in the 400hp doldrums for ages and ages until the trial and terror of experienced builders gave the magic recipe for unlimited horsies

In fact we made cams with duration more than 300, keeping the OEM lift.
It has very nice overlap
Also - at 1mm lift the duration is about 260.
So the lobes are very flattened & "angry" in this sense.

With that 470 hp is the result on the OEM turbo (1.8 bar boost).
The result was achieved with use of OEM pistons, etc.
Only cams & ECU was altered.

After 20th run 2 of 4 pistons were blowned with thermal load because of overlap. This result was expected, the OEM pistons were used just for scientific curiosity.

So - if you have nice nozzle area in your turbo (OEM turbo can't be judged as a real backpressure generator, it's twinscroll housing is rather free-flow stuff), big NA-type duration & NA-type overlap can be easily used. With nice gain at all!

Yeah, the exhaust was non OEM, it was 3'' DP & the rest pipes were also 3'', the IC also was changed to FMIC - that's all in tuning for that car including mentioned before ECU & cams

The car is ST205 with 3gen engine.

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"To raven, to do a crap, to sward a pinkie - just that are the needs of a real man"

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