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The mkiv Supra Owners Club

individual throttle bodies


paul mac

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Well i've had another red wine induced e-bay moment ;) (see 24 pot brembo for my last) seriously, i have been wanting to do something trick with the intake for quite a while and my original plan was a dual stage inlet involving a set of 50mm "short" runners and 35mm "long" runners with a set of control flaps but although i think this would still work the complexity has put me off, so plan B :- found a set of throttle bodies off a 2002 BMW E46 M3, did some research and found a 2JZGTE IS300 on SF in the states with GSXR750 bodies but figured the M3's should be a lot nearer in shape and layout than the uber compact bike ones and with the M3 being a 3.2 litre straight 6 they really dont look a million miles out :).

From the pics you can see two shiney tubes on the top, the smaller dia is the fuel rail (interestingly 18mm id) the larger is a very healthy sized vacuum connection linking all the bodies so hopefully i can still retain MAP (as per the IS300), the stock plenum inlets measure around 44mm each and the M3 bodies are 50mm so allowing for the restriction of the butterfly plate they should just be slightly bigger than stock, the other good thing about these over the Gixer's is all the bodies are seperate the only thing holding them all together is the main throttle linkage bar. So potential problems :-

MAP or the dreaded MAF

Will the buterfly spindle seals handle boost (1.6+)

Synchronisation

Throttle linkage and cruise (sorry but i love cruise control)

TPS

Vacuum link (brakes)

Plenum

any comments on the above or can anyone see anything glaring i have missed, would be greatfully recieved

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If I may blunder in here full of ignorance and interest...

 

Are there any advantages to doing this, or is it more a case of 'cos I can'? I imagine it would sound fantastic though.

yes your right there is definately an element of "cos i can", i do get bored easily watching telly and really enjoy a challenge/project, as for advantages I think its to easy to just dismiss ITB's as a normally aspirated thing, i once read somewhere anything that works on an n/a will also work on a turbo engine , granted the biggest percentage gains would come on a n/a.

The obvious improvement is throttle response but i cant remember the last time i got in my car and thought "i need more throttle response" :p, power delivery can also be tuned by the inlet valve area to ITB butterfly area ratio, ITB's also give a better balanced flow into each cylinder. I think the real advantage would come on a manual gearbox small single setup blatting round a track but alas a 2 wheeled accident many moons ago means i'm restricted to a "slush box" ;) so i'll make the most of what i have :eyebrows: and see what i get, if it works out i'll post all my drawings so it should be pretty easy for anyone else to replicate

 

 

 

wow missed that one bud did it make it off the drawing board

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Nice idea, but i would be inclined to have a look at adapting a set of RB 26 throttle bodies/plenum, as it looks like the BMW ones will need to be closer together, which will cause big problems with the linkage, but good luck whichever way you go:)

 

that was one of the first things i checked and theres nothing that scares me, besides we dont want any of them Skyline boys finding out we're putting Datsun bits on our cars ;) oh the shame, first thing i need to do is get the pressure washer on them, for some bizarre reason their covered in sand !

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If I may blunder in here full of ignorance and interest...

 

Are there any advantages to doing this, or is it more a case of 'cos I can'? I imagine it would sound fantastic though.

 

As already mentioned the main benefit if improved throttle response when running large overlaps because there is less intake volume to fill up with exhaust residuals.

 

You also get a slight benefit in the reduction of puming losses, as the induction air isn't being sucked through the main throttle.

 

Probably less relevant on a forced induction engine, but not totally irrelevant.

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had a bit of a play today

1st pic shows the TPS side body note the slight downward angle of the body as well

2nd pic shows a supra inlet gasket on the body, not to bad a match, i think the easiest way to mount them is going to be to make a spacer plate that matchs the head and all the bolt holes for the bodies

3rd pic shows a stock Bosch M3 injector and a Rochester -Siemens injector, the Bosch injector has a much longer nose to protrude into the body further, the Rochester is a perfect fit in the body but unfortunately sits 8mm further back than the Bosch, will have a look for some alternative injectors, interestingly the stock M3 Bosch injector is only 247 cc :search: and it makes 320hp :blink:, i suppose this reflects a more efficient modern design than our ye olde Supra engines ;)

 

apologies for not using photoshoped pics but it drives me mad when you find a really good thread and all the photoshop pics are not available any more

throttle bodies.jpg

throttle bodies 022.jpg

throttle bodies 023.jpg

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Yes i think an adaptor/spacer plate would be the best way, then you could keep the std throttle linkage, which will make setup a lot easier.

Not sure about the shaft seals though, being from an N/A they will be designed to prevent leakage from outside rather than inside, but if the tolerances are good you may get away with it.

Plenum design will be the telling point i suspect, and will determine the overall efficiency.

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interestingly the stock M3 Bosch injector is only 247 cc :search: and it makes 320hp :blink:, i suppose this reflects a more efficient modern design than our ye olde Supra engines ;)

 

It's an NA, so running high 12's to low 13:1 afrs for max power - the injector requirements are smaller :)

 

-Ian

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  • 3 weeks later...

well i've managed to stay off the red wine for a day or two :eyebrows: so a quick update, decided against an adaptor plate direct to head as some of the TB's holes and cylinder head studs overlaped, i could have re-drilled the head but bottled it due to having nightmares about breaking into water ways etc :eek:, so i have got a stand off plate made that will be welded via tubes to a cut down lower plenum, found some lovely oval tube at http://www.rossmachineracing.com/intakepartspage.html

and was going to use their "velocity stacks" but i have really been looking for a true velocity stack rather than just a simple radius. I've now found some plenum intakes that should do the job

Last pic shows the worst mismatch from the 90mm M3 cylinder spacings so the tube will need to be angled for number 2 and 5 cylinder.

More astute observers may have noticed there are only 5 TB's here, the last is at work having some ally bungs made for the redundant injector holes, interestingly this is the first time i have used waterjet cutting and its spot on, surface finish is not as good as milled but from loading the program in the machine to finished took about 10 minutes :cool:, they dont even bolt the plate down, the guy charged me a tenner for the complete cut plate, i could'nt even buy the material for that, bargain

throttle bodies 006.jpg

throttle bodies 007.jpg

throttle bodies 008.jpg

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  • 3 weeks later...

bit of an update, been far to busy with work, training and sitting exams :(, bought some more bits though, got some sweet oval section tube from http://www.rossmachineracing.com/ who are jolly helpfull guys, also got some fuel rail brackets from them which are very nicely cnc machined and a considerable improvement on my old ones, picked up some bell mouths and these will be going inside the plenum (cant help thinking how cool these would look on an n/a :eyebrows:) i think from a packaging point of view the Ross machine bellmouths would be far easier to mount but that exchange rate at the moment is a killer :(, right need to get in the garage and start hacking "aluminum" :)

intake gasket 026.jpg

intake gasket 024.jpg

intake gasket 027.jpg

intake gasket 030.jpg

intake gasket 031.jpg

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