ITB size wrt intake port size..

[celica-fiend]

So.. having read the stickied TB size post and followed through Lances calcs, including the 20% efficient bit.. Ive been a bit surprised and hope someone can straighten this out for me.

Motor is a Toyota 20R/22R hybrid, give or take it'll be 2366cc or 144 ci according to googles conversion.

Working through the calcs for ITB size with the 20% bit, I end up with a whopping 57mm per runner TB..

Which.. sounds a little .. stunning to start with.. even with my near complete lack of knowledge of gas dynamics.. heres my thoughts though:

I previously had a set of 40mm Weber DCOE's on the car, with (off the top of my head) either 36 or 38mm chokes. The intake ports on a 20R head are 35mm.

Going by those measurements, I had thought that my Triumph TT600 TB's would fit the bill, being a 44mm bellmouth -> 38 mm thottle plate .. given the much lower redline of my motor (7200, very worst case scenario) I thought this would work.

I also had hopes that running a smaller diameter body would give me a stronger MAP signal at idle and tip-in and allow for better off-idle transitions..

So having worked out the calcs and come up with the 57mm TB's.. I was..err.. stunned

Comments?

Thanks,

Brett

[whittlebeast]

Shooting from the hip from a calculation standpoint but from MS experance, I would stay in the 42mm X 4 area. That should be plenty for your application. You will find that about 15% throttle application in the low revs will be enough to produce full power at those revs. The fight will be drivability. In the CRX/B16A in first gear and driving in the rain, any significant movement of your foot would instantly light the front tires. The extreamly light flywheel and huge clutch did not make this any easier. Any binding/stiching in the throttle cable only makes this worse. MAPDOT AE control and RPM based AE is a must.

see www.ncs-stl.com/crx

AW

[Thomas Rouw]

Think 42 is a little small, for that cylinder volume, you would surely have heaps off torque lowdown, but if it's HP on top you're after I would absolutly not go any smaller than 45mm.

42 is very nice, for very small chambers at very high RPM hence motorcycle, my advice would be 45mm

grtz Thomas