Custom ITB EFI build

[Bjornb]

Heres some pics of my current project. I'm modifying some throttle bodies off of a couple of Polaris 650cc snowmobiles to fit on my 911, I decided to give it a try after seeing other members using motorcycle tb's on their Porsche's. The tb's are 46mm which may be a little on the big side for my mostly stock sc but they only cost me $65 shipped so I'm gonna give them a try. I've already machined up a set of manifolds for them so now I just need to get my engine back together so I can bolt them up and start figuring out the throttle linkage and everything.

Heres the pics









I have more shots If anyone cares to see more.

[wowzer911]

I'm in, post some more.
These throttle bodies line up with 911 intakes?

[James Brown]

sounds like fun! I found a website that uses parts off old fords to make a wasted spark distributer-less ignition system for about $100.00 that would be great to build an EFI engine for way under a grand!!

[CBRacerX]

Looks interesting!

[stevemfr]

Yes, please more pics and info. Are the bores on your manifolds tapered? (nice work, btw) What ems are you planning on using?

[JohnJL]

Originally Posted by James Brown

sounds like fun! I found a website that uses parts off old fords to make a wasted spark distributer-less ignition system for about $100.00 that would be great to build an EFI engine for way under a grand!!

I've got all those parts. Its called "EDIS-6." Needs either a dizzy or crank angle sensor with a 36-1 tooth wheel. Even better is pair it with Megasquirt or other ignition control with a map.

[don gilbert]

yes, more pics and keep posting.. my brother and i have been contemplating for months how to put hyabusa tb's on the 3.0

[jcc911]

Very interesting, please more pics!
Keep us updated.

[Avery]

Nice....I did a simililar conversion but I did not make the manilfolds. I used the 964 intakes and the rubbber boots. Everything lines up perfectly. I did have to buy a set of adapters to mate the two bolt intake studs of the older motoros to the three bolt intake studs of the the 964 intake....I got those from Jerry Woods. I like your approach of making the intakes much better.

So far, I've only run the motor on my dyno, and its very sweet. You will like its tunability...

I will be interested in how you develop your throttle linkage. Mines crap for now...but ok for dyno testing.

[Avery]

Here's a pic of my set up with the 964 intakes. I still have to make some plugs so I can eliminate the old 964 fuel rails.

[911st]

Wow!

[safe]

Nice work!
I think those will work perfect.

[kenikh]

Glad to see someone is making progress on this, and close to home, too. You should hook up with Al Kosmal in Mount Vernon. He and I chatted long ago about solving this very problem with these (among other) recreational vehicle ITBs.

[Bjornb]

Wow! I wasn't expecting so many responces so quick. I will upload some more pics when I get home but to anwser some questions the tb spacing is 116mm which I think is 1 or 2mm narrower than the 911's spacing, yes the manifolds are tapered from 46mm at the top down to 38mm at the bottom, I am planning on running with a Haltech e6x unless theres something better for the money and as far as throttle linkage is concerned I won't know for sure until I get my topend back together but I was thinking of replacing the steel bracket that connects the three together with and aluminum part that I could link the throttle off of but its hard to tell without it bolted to the engine. Thanks for all the positive replies and if theres any more questions feel free to throw em at me.

[Bjornb]

Hey Avery what does the outside of those 964 manifolds measure? I need some sort of rubber coupler to mount my tb's with and if the 964 boot fits good I will just buy them.

[Bjornb]

Hers some more pictures! some of the parts look bent but it's just the camera lens

[safe]

Originally Posted by Bjornb

The tb's are 46mm which may be a little on the big side for my mostly stock sc but they only cost me $65 shipped so I'm gonna give them a try.

A few thoughts:

My TBs are big too, 48mm on a stock 3.2. When come to think about it they are 48mm at the bottom but they are tapered, so the throttle plates are probably closer to 50mm...
The main disadvantage I have seen this far is the non linear throttle response and that I have to run the engine incredibly rich when cold, or rather, when it's not at operating temperature.
Otherwise torque is pretty even from 2000 rpm up to 6000.

I used a small piece of rubber hose to connect my TBs to the "intake adapter".

*You will need to fabricate a throttle linkage that has a progressive opening to get the best out of it.
*Build the intake stacks as long as you can.
*Get the engine mapped by a proffesional on an dyno, saves you a lot of time an worry.

[Bjornb]

Just got back from Texas yesterday and had some parts waiting for me. Here's some pics of the tb's mounted to the manifolds with 964 intake boots and a couple shots of the 6AN fuel rail material I ordered. The 964 boots are a tight fit but they slide right on if you twist them while you push.

[SCHNELE]

nicely done

[rvanderpyl]

Here's a picture of what I did with mine, unfortunately due to completely dis-assembling my car to rebuild it, the motor has just been sitting ever since.






I used Kawasaki KZ750 TB and Weber manifolds. I was also able to use the normal Weber throttle bar by making some adjustable linkages.