Discuss all things tuning in this section. News, products, problems and results.
Ive got a 3.4L VVTI 2JZ with a Hypertune race intake manifold. Obviously this manifold style (Large plenum short runner) is suited for high rpm flow.
I have a 90mm electronic throttle and I think there is some advantages to be had by limiting max throttle in the lower RPMs. My thought is that I can keep air speed higher with throttle limiting which will allow me to advance the intake cam at lower RPMs and see a torque benefit.
As far as tuning goes what would be my best approach? I was thinking low RPM pulls (1500-4000) and limiting max throttle on each pull to see if the torque curve changes at all. Once thats optimized go back and start feeding cam advance in to see how that effects the torque.
Any input is appreciated
Can't see how decreasing tp opening increases air speed, doesn't make sense to me but one can only try.
Working under the “thumb on the garden hose” theory.
With individual throttle bodies/carbies there is often a benefit in using partial openings for several reasons, such as turbulence around the 'blades causing turbulence for better mixing and reduced fuel drop-out, and improved pressure wave reflections and timing, maybe other reasons?
I have read claims of there also being benefits with single 'body plenums, possible because the lower plenum pressure affects pulse velocities within for better pressure wave timing - can't see it affecting port turbulence but been wrong before, will be again.
This is the sort of testing where a steady state dyno' is great, but your method may also provide some useful (or not) feedback.
I've yet to see an improvement in torque from reduced throttle opening at low rpm on a single throttle/plenum but this is definitely a consideration with ITBs. It's pretty easy on the dyno to test the theory though. Just monitor torque under steady state as you go from light throttle to WOT. If you see the torque climb initially then plateau and drop as you move to WOT then just cap the throttle opening at the point where you saw max torque. You can profile the throttle vs RPM in the dbw throttle translation table.
I doubt there will be an increase in a standard butterfly throttlebody due to turbulence of the shaft/fasteners of the shaft/plate unless they're very low profile and knife edged. Even then I'd be doubtful. I could see it working in an iris style setup, an potentially a slide throttle? I'm not sure, though I will be tuning a periph 4 rotor with slide throttle later this year once its assembled and can revisit.