Single or multiple TB's?
Turbo Mini Forums

Bearing in mind im still learning about the whole injection side of things, could anyone explain (in simple terms lol) the advantages and disadvantages of the two setups?

And are the pro's and cons of each setup the same for blown engines?

Cheers

Matt

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1/4mile in 13.2sec @ 111 terminal on 15psi

The main advantage of having a throttle per cylinder is that you can run the exact tuned length (both in terms of butterfly position and overall intake length) required to give best results.
The other advantage is that you can optimise the airflow right through the system by matching changes in section and avoiding tight turns etc.

Both of these points are far less significant to a boosted engine so you will see very little benefit in the real world using multiple throttles.

I am assuming that your thinking about what to do for the K head conversion your doing. If it's any help I intend to make a plenum and run a single throttle body. If at all possible I will do my best to equalise the intake runners length to help give as even a total intake length as possible, certainly helps when running off boost and although opinion is devided on the significance under boost I can't see it hurting!!!!

Every day is a school day ...........

How fast and how expensive ...... the same question...

I was thinking of running the standard TB's or maybe some Hayabusa ones and a plenum before them, any problems doing it this way round as the more popular install seems to be TB then plenum?

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1/4mile in 13.2sec @ 111 terminal on 15psi

For my charged K engine it will run a single throttle body as well (just to be posh - well there is more to it than that but I'm not letting on! - it'll be drive by wire as well!)- nice simple to manufacture plenum and no loss of performance - you can also package the plenum closer to the head to gain space/plenum volume without the tb's being in the way.

RB racing use the std throttle bodies on their bike conversions so it obviously works that way as well

JK

If Carling made Mini engines
it would probably be like this one!

Matty, if you stay with ITBs just use the bimmer ones .... more than up to the job IMHO.

John's point about having more space in front of the engine (for IC???) is valid too.

Every day is a school day ...........

How fast and how expensive ...... the same question...

Yeah space is going to be tight (to say the least..lol), I suppose thats one advantage of the 8V the intake pipes are that little bit shorter!

How do you go about sizing up a single TB, is it just a case of trying to get the venturie size the same area as the 4 seperate TB's.

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1/4mile in 13.2sec @ 111 terminal on 15psi

It's a little less critical than individual throttles. Basically you can fairly easily work out from revs, boost and capacity how much approximately you'll be drawing into the engine .... make sure the TB is a little larger than that (no restriction at full throttle) and make sure you can make a linkage for it that will give a nice progressive control with the availabel pedal travel and your there. Not the most technical description but should prove good enough to get you a nicely running motor.

Might also be worth looking at the various twin butterfly bodies with different opening rates ... not as important with EFi as mechanical but still can give some benefits in light throttle / load running.

Every day is a school day ...........

How fast and how expensive ...... the same question...

Well at the moment I have no idea what boost I will be able to run, and won't untill the engine is running?

I was thinking along the lines of a k head has 4 at 34mm so working it out area for area a single would have to be around 68mm. Looking at the mpi's they seem to be 52mm so I can't see that being far off? What you recon?

Have you got a formulea for working it out?

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1/4mile in 13.2sec @ 111 terminal on 15psi

Lol..scrap that calc seems well OTT when looking at other engines

Ive found this site, that seems to have what looks to be handy info.

http://cherrypicker.tripod.com/index.html

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1/4mile in 13.2sec @ 111 terminal on 15psi

Ive decided to stick with the K TB's, I recon I could just about squeeze a plenum in aswell. :)

Ive got the coice of 34mm or 38mm, any perferences which would be better?

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1/4mile in 13.2sec @ 111 terminal on 15psi