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Michael Mount,
Research is showing that some customize the earlies to 48mm+/-. Would this be too big ?
I keep thinking its important for the flow to be good during pre-boost & since the inlet of the 2v head is 42mm, the ITB should be very close to that at the runner, but the throttle plate and shaft take up space, so maybe a 46mm or 48mm is better. Seems logical.
Also, if someone were intentionally driving in rpm range 3500-5000 would smaller be better?
You can have most moder turbo, wastegate, boost control etc but nothing beats the throttle response of the ITB's and coupled with turbo it is the best combination. The fact that it is used seldomly is caused by cost.
Also in hotrod world you see it not so often because it takes some experience and knowhow to set up, you get ****ty drivability with just speed density and you cannot tune boosted engine with Alpha-N only. You need ECU that has Alpha-N/hybrid load strategy (which is essential in getting a n/a ITB engine running well too and not having constant mixture issues with different load and humidity).
I built ITB'+turbo+EFI engine for my 924 Turbo "Gulf", using GSX-R750 throttles. Up to 2002 or so they were separated and in order to get proper cylinder spacing I just needed to extend the linkage between throttles and machine proper spacers.
Mike refers to sizing in this thread: https://rennlist.com/forums/944-turb...tb-intake.html
Whereas the Hayward Performance is like 54mm!
I'm inclined to think LR is right about the sizing; a 2.5 litre with stock intake valves will be better off with smaller 42mm + so as to cause less disturbance... but please educate me if I'm on the wrong path.
Whilst sipping this morning's coffee, I thought I'd search to see the NINJA motorcycle's ITB set up.... and familiarize myself with it. Holy! 2 throttle plates per cylinder. Apparently this helps control air flow to increase torque at lower rpm. Look at this pic & see it shows what I think is a idle air solenoid (could be wrong) and the double butterflies! This might be going overboard though! In the NINJA world, there are discussions about more power being had by removing one butterfly. I like they Haya solution better.
As close as possible to the intake valve would make the most sense. If you are using the stock intake flange, I'd just leave the injectors in the factory location.
Good. I was planning on leaving them in oem position but figured I'd ask.
Some Hayabusa have 2 inj per hole, angled differently and one on either side of the butterfly (above/below) and may not be used at the same time (it's unclear, but one might be a WOT inj, which may explain the 4 pin TPS), but either way it's straying from a more "conventional" ITB adaptation. Thank you all. I am confident this will be something to try once I finalize my engine as it is now, so that I can experience the "before" and "after".
Having the injector upstream improves charge cooling especially good on turbocharged engines. With E85 it's even a greater advantage. Of course there is a VE disadvantage that occurs from fuel displacing available oxygen but that can be more than compensated for with the cooling effect of E85. The time delay in fuel delivery can be compensated for with an aftermarket ECU. Is it all worth it? Probably not for a street engine.
05-30-2021, 01:17 PM
. Seems logical.
