EFI/ITB Questions
 

Have a stock Carrera 3.2 and (despite a million other jobs to complete) an urge to try a DIY ITB/EFI conversion using motorcycle throttle bodies. Why? Because retro-cool. Because orgasmic sound. Because eye candy. Because had a Yamaha R1 engine in my last car and want (some of) that throttle response in my flat-6. Not looking for any extra power. Would probably use Megasquirt for engine management and keep the stock coil + dizzy for ignition.

Anyway, I was curious how much of the stock 3.2 fuel system could be retained, to keep costs down and the ability to switch back and forth if things go tits up?

For example, if I could mimic the factory injector ports and fuel rail mounts with my ITB manifold, could I keep the Carrera fuel rails + fuel lines + fuel regulator + fuel damper + injectors? I would just plug the motorcycle injector ports.

How about the CHT sensor - can that be kept and used with Megasquirt?

What about the teeth+sensor on the Carrera flywheel: can that be used for timing instead of a wheel/sensor on the crank pulley?

I am currently planning to go with the popular 1000cc GSXR TBs from 2001-2002. They have 42mm throttle plates and the bore at the inlet side (42mm) is close to the 3.2 intake port diameter (41mm).

Yes to all except flywheel may not work. I know for sure MS II and I cannot decode the flywheel, but maybe MSIII? Doubt it because it needs a missing tooth.

I'm going down this path with my 3.2.

You can buy an injector drill bit (has the correct dimensions of a standard injector) and drill the GSXR ITB's.

I'm using Busa's....

Thanks. Why did you go with the Busa TBs - I presume they have a slightly larger throttle plate than the 1-litre bikes?

How are you hooking up the TBs to the heads?

There was a discussion a while back about ITBs/EFI and there was a link over to a thread in either the turbocharging/supercharging forum or the rebuilding forum. I'll see if I can dig it up. Steve Wong and a bunch of others contributed to it and it was an excellent read. He published the EFI maps from the stock 3.2 DME. You could use those as a baseline to get in the ballpark and then tweak from there.

And just in case you haven't seen it, check out the Clewett Engineering website. Richard Clewett has a complete package that I looked at when considering upgrading my 3.0L motor. At the very least that could give you some additional ideas.

Do your homework before going ITBs, they work great on hi-reving engines that why motor bikes like them. But for a street car you may not be happy, plus the 3.2L is at best good for 6800RPMs and you will give up low end torque and most likely a lot of it. Putting ITBs on these motors goes well beyond just bolting them up and adding EFI. You need to consider all the components as a whole, cams are very important with ITBs as is getting a higher rev limit and that costs a lot of money to do correctly. I advice you really ask a lot of questions about how ITBs effect torque curves, dig up dyno sheets from the stock 3.2L then find some from ITB engines and compare the torque curves you'll learn a lot from doing this.

If you are keeping the stock 3.2L cams they won't work well with the ITBs and if you don't plan to increase revs significantly, up to at least 7500RPMs the ITBs won't do what they are designed to do.

I went with those because of the 42mm outlet. Didn't realize the butterfly is 48. For comparisons sake, I believe the BMW E46 M3 engine uses 52mm inlet ITB's, the same as the 'Busa's.

Yes, I'd rather do GSXR1000's instead in case these are too big.

I'm having CNC blocks made going from head to ~2 1/4" circle using silicone couplers coupling to them and to manifold logs atop.

Sal, Chris Carroll from Turbo Kraft took an existing 930 using a 3.2 intake, and converted to ITB's picking up a huge amount of mid-range torque and of course about 50whp with no other changes. I know apples to oranges comparing boosted to NA, but throwing that out there.

Al Kosmal has done some work in this area. Talk to him before recreating the wheel.

Regarding the use of the existing 3.2 flywheel sensors, I found the following in another thread. Looks like it's doable with some additional Megasquirt circuitry:

Nice find! Id like to use the original since it's more granular and should be pretty EMI safe being engineered by the factory. That's a great price!

Thanks for sharing.

http://forums.pelicanparts.com/porsche-911-technical-forum/741911-d-zug-tours-rsr-dyno.html

https://www.youtube.com/user/koz77911

regards
al

If you put a rain hat intake over the ITBs (like the older early cars) then the intake has 1 large air inlet horn and can easily be fitted with a MAF sensor. Some modern day race cars run system exactly like this, ITBs with MAF air metering. If this is done I may be able to help and you could retain the entire stock DME. The only issue is the idle air control valve would be deleted but I don't think that's a big deal. I already have a MAF solution that works flawlessly for the 3.2L.

Or you can even possibly do this setup and retain the factory AFM but it would look ugly.

Poke around the net and search for ITBs with MAF. An intake like this can easily have a MAF adapted on the Air Horn:
http://forums.pelicanparts.com/uploads21/Air+Filter1345087933.jpg

MAF is hands down the very best way to meter air and fuel.

Thanks for your input Sal. I was planning to use 2 separate foam filters over each bank of 3 ITBs, though (rather than an airbox). Why? I just don't like the look of the huge airbox. So I would be limited to MAP or TPS for load (the GSXR ITBs already have vacuum take-offs and a TPS). Also, even I was able to get a load signal readable to the DME, how would I tune the DME (compared to, say Megasquirt)?

For aesthetics, maybe you could make vacuum sealed rain hats that merge at the rear cylinders with a single MAF?

don't think that fits the criteria:

nice..... Trog

Trog, that looks like it's for 3.6 heads and not 3.2, right? How did you make those adapters that sit on the intake ports and fasten onto the 3 studs (2 for 3.2 heads)?

Actually, it's designed for the 996. However if you want to run ITB's with a MAF sensor, this is the configuration that's required.

Trog,

This would also work well for MAF setup:
Welcome to Rothsport Racing - Engine Products
Could even be used with stock harness and DME, I think my MAF system would do well with these ITBs and the common plenum they have.