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Hey all... researching for my new engine build, Ive noticed alot of serious motors and aftermarket manifolds are using Single throttle plenums and just wondering why exactly?
While we are on the subject what is the exact benefits of ITB's on a turbo engine... is the aim to reduce lag and/or throttle response?
Do the stock ITB's become a restriction at higher power levels and its just cheaper to go single throttle?
Or there other cons of ITB's or maybe Pro's of a single throttle effecting their decision?
The general reason behind the multi throttle setup I believe is to aid throttle response. I'm not personally convinced and I've tuned/driven GTRs with factory itb's as well as individual throttle bodies and couldn't really pick the itb's as a winner myself.
At some point the multi throttle bodies will become a restriction, and this may be one reason to swap to a single throttle body/plenum if you're chasing big power. The other reason however is that the single throttle/plenum simplifies tuning and is probably easier for most tuners to get their heads around.
I'm not convinced that ITBs improve throttle response either.
If you think about the volumes of air involved...
Using a different example just because the maths is easier.
A 2L NA 4 stroke 4 cyl engine at 100% VE consumes 1000 litres of air per minute per 1000rpm.
So 6000rpm = 6000 litres per minute which is 100 litres per second...
If you've got a 3 litre plenum volume and snap the throttle shut, it only takes 0.03 seconds to consume all of the air left in the plenum.
Even quicker if you've got a larger displacement engine and/or smaller plenum.
Nissan obviously thought it was a good reason for some reason though!
Both GTIR and GTR which were "race base" sort of cars had ITBs.
It's interesting that the R35 GTR doesnt though...