Does anyone know if F4i or 600rr throttle bodies will fit on a f3 engine? I really just want to know if the spacing is the same.

 

hmmm, they mount similiarly, need to find someone to measure there throttle bodies. Thinking of changing over to FI?

 

Well not so much changing as going to it directly. I've never seen my engine run, and have recently rebuilt it for a project of mine.

 

I actually asked a motorcycle mechanic freind of mine and he told me It would be cheaper and easier to buy a f4i engine and put that in the F3 frame. He said the motor would be very very difficult to get it to run properly with FI because of all the computer crap that comes along with the fi and the engines lack out computer control. I dont think im making as much sense as he did. But if you do find a way to prove him wrong i'd love to know. I <3 my F3 but I will be moving up to something in the near future mostly for the FI.

 

My reasons for doing this are many. Cost being one. I have an engine already, and everything to make it fuel injected besides the throttle bodies. While I can make tehm myself, I'd much rather be able to use the F4i ones. And its not going to be put in an F3 frame, but one of my own design. I'm not going to be uning any stock Honda electrics either. I've got an Electromotive ECU and coils, and will be writing the fuel maps myself.

 

If the throttle bodies are larger than the F3 carbs,you may have lots oftrouble getting it to run right.

 

Not with the right volumetric efficiency tables. Remember, airflow is dictated by what the cylinder can pull in, not by how big the tb is. As long as your injectors fire the correct amount of fuel at the correct time, it doesn't matter how big these things are.

The only time size matters is in carbs because the size dictates air speed through the venturi, which determines how much gas flows out. There isn't a venturi in FI, because you dont need one.Thats the beauty of injection, its adaptability and precision.

 

Here's a thought. Sell the F3 engine and use the money to buy an F4i engine!

I know a guy that builds small F1 style racecars (on some sort of a team, sponsors, the whole 9 yards) and they use F4i engines all the time. They have a hard enough time dealing with F4i engines and I cannot imagine what they'd have to say about trying to convert an F3 to FI.

If its just some silly garage project like a gokart then it doesnt need FI, just deal with the carbs If you NEED FI, then sell the engine and buy an F4i engine

 

I love how on this forum you ask a simple question, and instead of getting real answers you get all kinds of "bolt on this", "buy that" answers. I asked if the F4i throttle bodies have the same center to center distance as the F3 intakes. This is all. I have no desire to buy an F4i, as I'm only planning on using the throttle bodies if they'll fit. I alreadyhave my computer, and it doesn't matter what I use it on, its fully programmable, I'll have just as much trouble with the F4i as I will with an F3 with throttle bodies.So I guess I'll have to find someone local willing to let me measure their F4i. I just thought that with the wealth of knowledge on a site like this, someone would know the real answer to my question. Or I'll just make the throttle bodies myself.

I know you're all trying to save me a lot of time and frustration, and I appreciate that. But any suggestions as to the realanswer to my problem would be appreciated as well.

 

IIRC,the F4 & F4i motors are more narrow than the F3.You'd have to make another bracket/rack for them.

Now....

This is true,but your engine has to pump the air out faster ,this is where additional rpms come in.F3 bottom end wasn't designed for the higher rpms of the FI bikes.IMO,13.5k won't quite do it.All parts are complimentary.Therein is your weak link.

In order for the fuel injection to "adapt", you must have the sensors as well,intake and exhaust.You'l need an F4i exhaust header.The F4/F4i motor is more narrow than the F3,so you'll have to fidget with the header to make it work.

There's a guy out this way that does this with a drag bike,so it can be done.Didn't ask him how,though,of course he won't tell. [:@]