i'm building a busa turbo to go in seven type car and at the stage of making the pipe from the intercooler to the plenum. i've got a spare cosworth throttle body lying around and wondered if this would be better than the stock busa throttle bodies for this application.

like most turbo throttle body's the cosworth one is designed so that pedal movement / butterfly movement is not linear in so far as the initial 75% of pedal travel only gives 25% of butterfly movement and the final 25% of pedal movement gives a lot of butterfly movement which apparently gives a more linear 'feel' to the driver and smoother engine response for road use.

i could clamp the stock busa butterflies open and use the cosworth one.

any thoughts?

crikey! 170 views & no-one has an opinion?

Most folk who turbo charge (fuel injected) bike engines use the individual throttle bodies. It is supposed to give improved throttle response than the approach with single throttle body.

I think a single throttle body would probably be easier to tune than with the suzuki ITB. With the ITB the air flow is a complex function of MAP and throttle position that makes it tricky to tune. I certainly have had some troubles mapping, although I have solved these for the main fueling tables (dual table in megasquirt), the acceleration enrichment is still tricky because of this. Mine isn't a Busa, just a baby version.

I suppose it depends on what you are aiming for. Ultimate performance (then the ITB method, like in Skylines and Pulsar GTiR, and most Turbo-Busas), or more civilised road-manners (like pretty much everything else).

How are you going to control the fueling?

Matt

hi matt,

thanks for your input.

fueling will be using single injectors mounted in stock busa throttle bodies controlled be ms2 sequential. so if i went the single throttle body route the busa butterflies would just be permanently fully open.

you have hit the nail on the head as to why i put up the post as many folk seem to run into tuning problems with separate butterflies on a turbo. i think i'd rather have easier tuning than ultimate throttle response if thats what the options are

From reading the above and my own limited knowledge I'd look at removing the buse butterflies completely using the stock inlet as a base for a new manifold and use the cosworth throttle body.

why remove the butterflies completely, is that to improve airflow?

is it your experience that the cosworth throttle body would be more suitable?

As you say to improve flow. If try aren't being used might as well be removed. Leas obstructions and less things to fail.

I have no experience of the cosworth throttle body but my limited knowledge of
Mapping Etc and matts post combined all add up to the above comment.

yes i'd agree that removeing the busa butterflies would be better and that removing the butterfly spindles would be better again. its a 'no way back' solution however once its done!

I had a R1 turbo that (originally) ran with a cosworth single throttle body, When i spoke to the builder/tuner i was told that it suffered 'massive' surge problems, enough to overcome the waste gate and hold it shut while trying to rip itself off the dyno. Apparently hit 30 psi for a moment. Cure was itb's with a re-designed exhaust manifold. Ended up using gsxr1000 tb's with hayabusa injectors running on a KMS ecu
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