JoshC
JoshC New Reader
1/9/09 9:27 a.m.

Are there any throttle bodies in the ~30-40mm inner diameter range that are readily available, cheap and compact? I'm thinking there have to be some small throttle bodies that came on low displacement engines sitting in junk yards somewhere, but I need model/year information. I'm toying with the idea of a cheap ITB set up, but haven't had any luck finding what I'm looking for. I've seen a few that met the diameter requirement, but were physically too large to be useful. I also am toying with the possibility of using two dual throttle bodies, if I can find the right size.

z31maniac
z31maniac HalfDork
1/9/09 9:40 a.m.

Motorcycle throttle bodies are your best bet.

JoshC
JoshC New Reader
1/9/09 9:56 a.m.

That is a good suggestion in that it appears they are already plumbed for individual vacuum lines and idle control. My only concern is that spacing would now be dictated by the throttle body assembly (it appears that it is a single housing). Ideally, the TBs should be placed as close to the intake valve as possible, so spacing could be an issue (i.e. if they are spaced too far/close the manifold would have to be sufficiently long enough not to disrupt flow whereby increasing distance from TB to valve). I might buy one just too measure unless someone has some dimensions handy. There are some Honda/Yamaha (both from 600CC bikes) on eBay for $60-100.

16vCorey
16vCorey SuperDork
1/9/09 10:01 a.m.

I got mine from ebay for $53 shipped. Get some off of an early GSXR and they come apart, so you can space them how ever you want.

MadScientistMatt
MadScientistMatt HalfDork
1/9/09 10:16 a.m.

There's a mammoth list of motorcycle throttle body specs on the MSEFI forum here:

http://www.msefi.com/viewtopic.php?f=29&t=6627

JeremyB
JeremyB New Reader
1/9/09 10:42 a.m.

Just wondering if you're planning this for a race engine that is seeing high rpm's all the time or will this be on a street car? I think that ITBs with short intake runners are bad for engine torque and driveability at lower rpm's (like driving on the street). These work on high performance street bikes because they rev up much more than car engines.

Look at any modern auto engine and note how long the intake runners are. They smooth out port velocity as much as possible to flow air through the head. ITB typically tumble the air around if they are not fully open.

Now, I will say they look pretty darn cool on any sports car.

16vCorey
16vCorey SuperDork
1/9/09 10:59 a.m.
JeremyB wrote: Just wondering if you're planning this for a race engine that is seeing high rpm's all the time or will this be on a street car? I think that ITBs with short intake runners are bad for engine torque and driveability at lower rpm's (like driving on the street). These work on high performance street bikes because they rev up much more than car engines. Look at any modern auto engine and note how long the intake runners are. They smooth out port velocity as much as possible to flow air through the head. ITB typically tumble the air around if they are not fully open. Now, I will say they look pretty darn cool on any sports car.

Or you can have the best of both worlds.

JoshC
JoshC New Reader
1/9/09 12:22 p.m.

Some late model BMW engines use ITB, which are located almost inside the cylinder head. I think the additional runner length is upstream of the throttle.

We're tossing around ideas for a possible challenge car hence the cheapness requirement.

JeremyB
JeremyB New Reader
1/9/09 12:43 p.m.
16vCorey wrote: Or you can have the best of both worlds. "image"

Well done and very nice looking setup.

stuart in mn
stuart in mn Dork
1/9/09 1:15 p.m.

If you're really handy with a milling machine, there's a guy over on the HAMB board building his own ITB setup. He calls it Hillbillyborn injection.

http://www.jalopyjournal.com/forum/search.php?searchid=5144217

fiat22turbo
fiat22turbo SuperDork
1/9/09 2:04 p.m.

I was going to use a series of early Turbo-dodge throttle bodies. You know the old "suck through" pieces found on all of the Chrysler turbo vehicles from 84-87.

They are nearly perfect for this application: 40mm bore, with a built-in adapter for a rubber connection that can be separated and have a plate installed to tie all of the pieces together. Exposed linkage that would be easy to link together. Pretty standard TPS, dead simple AIS motor which is either open or closed and can be blocked off. They are cheap because no one wants them and they were relatively plentiful since Chrysler pumped out millions of turbo cars during the eighties.

However, then I found a couple of deals on ebay and would up with two sets of DCOE EFI throttle bodies. Thanks to eBay newbs about 5 years ago I was able to score some good deals because they mislisted the items. Of course that was back when eBay actually had good deals and small-time players.

FoundSoul
FoundSoul New Reader
8/22/12 10:10 a.m.

Sorry to raise the dead here... but I was just doing a little research on this topic helping my nephew prepare to make this conversion on his first car (S13 240sx) and ran into this thread, and saw the dead link to MSEFI above.

The replacement link for that is http://msextra.com/forums/viewtopic.php?f=94&t=6627&hilit=motorcycle+throttle+bodies

And it is a good list....

fidelity101
fidelity101 New Reader
8/22/12 11:49 a.m.

Snowmobile ones are good too

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