He did it though did he? Thats all I really need to know, that it has been done. I'll prolly end up having to fab an intermediate piece to make them fit, but if it's been done I can do it.

I dont really understand what you're getting at with the air, I wont be using an F4i fuel map, so as long as I put less fuel in to match the lessened airflow its fine. I have all my sensors etc here, I dont need to use an F4i header, all you need to do is drill out the F3 header ad weld in a bung for your O2 sensor. The vacuum lines are already in the head, I have my aftermarket crank position sensor installed, so I'm good to go in the sensor dept. I just hope theres a TPS or a place for one on the F4i TB's, but it shouldn't be too hard to make one fit.

Thanks for the input, it helps to talk these things out.

 

well, the F3 has a TPS and its just a carb, so the F4i motor should definately have one, as far as I know ANY fuel injected fuel has a TPS so the computer knows how much the butterflies are open and therefore knows how much fuel to spray. Depending on your computer, it may be able to adapt to the stock F4i TPS, making it easier than trying to fit a different one on there. If you havent already, get some in the F4i forums to measure the resistance range of the stock TPS and check to see if your computer is compatible with it.

 

kjohnson.... I'm confused here.

13.5k rpms isn't enough to make the throttle bodies work? What does redline have anything to do with larger diameter TBs? Also, why would he need an f4i header?

 

The engine has to burn off and expend/expel the fuel fast enough before it takes on more fuel.This is where mapping can be a pain.Notice how FI bikes rev faster,and higher?The bottom ends of the the FI bikes compliment this,the carbed ones don't.This may cause hydrolock or plug fouling with high regularity. Any internal combustionengine is basically an air pump.

 

Yeah scrufdog, i hope so.
kjohnson, I'm not quite sure what you're getting at. Sure you're right that an F4 prolly has better volumetric efficiency than an F3, but the redline or how fast it gets there is irrelevant. You're not sitting around at 13.5k+ all dayon your F4i, pumping fuel though it. For the F3, I will be using a custom fuel map developed by me for the application, so forwhatever air it can pump, I'll add the correct amount of gas at the correct time. The only restriction on the TB is to make it big enough, you cant have one thats too big, as long as it fits physically to the engine. My F3 engine wont pull in more air than it can, and my computer will tell my injectors to add the right amount of fuel, I dont see the problem.

 

Yea, the engine pulls in the air it needs. Just because you have larger TBs doesn't mean it's going to spin faster. The motor, at any RPM, will pull in the air it needs, regardless of TB size. The throttle bodies do not force air into the motor, only channel it into the engine.

Your logic is beyond me, if I'm wrong please correct me. I mean, by how I interpret what you are saying, is that people who increase the TB diameter on their cars (for more power) they would need a new engine with a higher redline. And that thing about needing the f4i header is bizarre also....

 

Why didn't you say you did your homework and had that covered,sooner?

Who did the map? I may try this myself (later on,of course )



Now to answer Fatboy:

The F4i header(aftermarket and OEM) has the hole for the exhaust sensor.The F2/3 header does not.Helps the cdi adjust gas flow into the motor,unless you override that by tuning it with a Dynojet tuning link.

Well,on a car there is more room for TB enlargement and other mods due to larger displacement.Bikes have less displacement (obviously ) ,so the need for gas combustion efficiency is magnified.Less room for error,if that helps make sense.The '02 RC51 is a geat example.Larger TBs,same displacement,complimented by better head flow and more efficient bottom end.

Ever put "too much carb" on an old muslecar motor? Same-same,as the Italians say.Hope this helped.

 

Ah, the too much carb analogy... didn't exactly consider that. The displacement issue also seems to make sense, I'll have to go read up on it. I come here to learn, I'm pretty naive at times

As for the f4i header, I thought you were saying it was need because of it's flow rate, not about a bung for a sensor.

 

I'm pretty sure I did say that, I just wanted to know how big the TB's were.

The maps not done yet, though it is on the way. The TB's have quite an impact on it as you'd imagine, as well as the rest of the intake and exhaust, so i have to wait till everything's together and then dyno test and set up my tables. The ignition map is done, though.

I did it myself, its not too hard with some of the aftermarket rigs that actually generate the maps themselves instead of putting in entries one by one like I imagine the power commander is, although i dont know. They make the maps, then you fine tune the entries.