any threads on EFI conversion using single throttle body
 

Having my Carbs on a 2.5l with 10:1 compression for about 6 years now, I think I'm ready to go for EFI and electronic ignition. in the long haul I know it's going to be worth the effort and price. Better drivability and hopefully a few more MPG.

I don't want to do ITB, would like to keep it cleaner. I'm thinking about finding a suitable single throttle body, like off a 3.2 or another car,, then making a air box that connects to the CIS ruiners I have. Install injector bungs into the CIS runners. Should make a clean looking install. I'd also like to use a MAF.

I can't seem to find any threads on people going the single throttle body route.
anyone know of some?

Also love opinions on controllers for both fuel and spark. I don't want to go with mega squirt, it looks very iffy for longevity.

Also love to hear about any MPG improvements people have seen switching to EFI from Carbs. I get 18 mpg now and it sucks.

I can't offer advice yet but I'm heading in the same direction. My 914/6 GT clone has a 3.0 with Weber carb's. Runs good but could be much better with EFI. I have already purchased a Carrera 3.2 intake manifold setup and a Autronics ECU. I'm hoping to have this be my winter project. I'm nervous about the tuning but the install should be fairly straight forward. I will run it as fuel only for a while and then possibly go full ignition. Will be watching to see what others have to say.

Yes, it has been done.

http://forums.pelicanparts.com/911-engine-rebuilding-forum/494048-3-2ss-ms-efi-dyno-results.html

What are your port sizes? Matching the ports will be the biggest challenge with a 3.2 intake. At 40mm it is likely too large compared to your heads. You can make a step down adapter.

You might want to consider finding a 964 intake. You could have simple head adapters made for the lower injector connections to convert from 3bolt to 2-bolt. Then you can use the ECU to trigger the variable plenum volume flapper. Every little bit helps.

If you want to use the smaller CIS runners just buy the injector adapters from Tony Bitz and use his fuel rails. Even if you do not buy the entire kit the parts alone will save you many headaches of fabrication.

I have had a MS system for nearly 4 years now. No issues with longevity. Any troubles have been my curiosity of trying new firmware and tune variants. Very stable and the cost point can't be beat.

My ports are 36, I was going to use some 2.7l CIS runners I have and the rubber connections and connect to a air box I'll fab out of aluminum. Those runners are aluminum and shoule be easy to machine for new injectors. I may just rework the CIS box instead of building one from scratch. Jamie, what ecu did you use?

I would just cut the top off the plastic airbox and run it. Too much work to fab one out of aluminum. Besides, plastic is lighter. :)

I have had a Megasquirt (MSII) installed for several years. I have also installed 4 other systems and had my hands in tuning an additional 4. If you understand EFI Megasquirt is a very capable system and has, so far, been very reliable for each party involved. The key to any EFI is an understanding of the tuning process and having a quality installation. This means no short cuts on wiring and taking the time to thoroughly plan the install. It is the same with all EFI systems. Properly installed and tuned , Megasquirt or any aftermarket EFI will give superior results.

btw, is your 2.5 a 90x66 or 70.4x86? I am building a 2.5SS right now that will likely be EFI.

thanks Jamie, My 2.5 was built from a CIS 2.4l motor, with JE pistons and I forget about the cylinders. adopt remember the numbers off hand. It's nice, but have to run stupid rich. I literally have to drag the cluch when I stop the motor. I should have done 9:5. But EFI should get me there I hope.

is there a formula to help figure out the right size throttle? I guess I don't really need to stick with a Porsche part with so many to pick from. as long as it's a good part, has TPS and reasonable breather to work with. Correct?

Go to the turbo forum and forget the turbo. Most of us EFI turbo guys are running the Carrera intake.

If you really have wild cames and high compression pistons, I would think that ITB EFI would be the way to go. Single manifold/TB intake will not be happy with wild carbs and lots of reversion.

well steve, it's not wild wild a cam really, just like an E cam.... should do fine I think ITB is too much for me to hammer out.

the throttle body off the 2.7l boxster seems like it would be a fit match for the engine, about the same HP with some room to spare, but not to much. and easy to come by. My question would be if I have to match the TPS type to megasquirt, if there are specifics to consider there.

The Carrera 3.2 TPS will not work with MS as it is not a true TPS but a series of switches. I would imagine that the Boxter is a true TPS and as long as it sends a 0-5V signal it should work. Clewett sells a TPS that is compatible with the 3.2 and that is what I am using.