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Individual Throttle Body Selection

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Well I made an impulse buy on Ebay and bought throttle bodies from a BMW motorcycle. The Bike is a 2002 K1200lt that makes 119 HP. My thinking was that my Spitfire would never make 119 HP so they would be big enough. The bore at the butterfly is 1.3” (33 mm)and they open up to 1.55 at both manifold and airbox ends which confuses me. Why would you want a venturi at the butterfly? They don’t have injector bungs so that gives me the flexibility to mount them far from the head while keeping the injector close. My Webers have 4 28mm chokes and it doesn’t seem to be gasping for air at 6K. it came with a TPS and a stepper motor to control Idle speed. 

To me the hardest mechanical part is going to be mounting them to the head. I already have a crank sensor for my Megajolt ignition. I welded a bung in the collector for a Bosch 4.2 LSU O2 sensor and I have an AEM gauge to read it.

You have to spend about $600.00 On a Megasquirt2 to get sequential not batch injection. I don’t see the point of spraying fuel at a closed valve. https://rusefi.com/ Is much cheaper and may suit my needs 

The pics show the throttle bodies sitting with a spare head. The sticks show the angles that the runners would have to be at. It doesn’t seem to bad to me.  I think they should go into the head as straight as possible but the ports are really close together.

So… what do you think of these throttle bodies?  Should the butterflys be closer to the head? Should I look for something bigger?

Any advice is appreciated. I don't want to start this long journey in the wrong direction.




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Thanks for the rusEFI link btw. Never come across that before. Another interesting alternative. Also don’t forget Speeduino, which is rather similar in concept. MS is still the daddy of DIY EFI in my book though. 

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Hey I did see that a while back. You were sending me subliminal messages when I decided to hit the "buy it now" button. The ECU will be one of the last things that I buy so if I can pull this off at a reasonable price I may spring for MS2. 

Full steam ahead Cap'n

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