We are currently looking for an engine for our FSAE car. I would be interested in getting a 600RR if I knew I could swap out to a lower - midrange cam into the RR. Specifically from a F4i.. Is this possible? Anyone ever tried it? Or has anyone ever tried the reverse? If so does the year model have any affect? We aren't big moto guys and even our motorcycle guys are not too sure about it. We've had to install valve shims from scratch so I know how difficult it is to do that. Swapping cams would merit a tedious re-shimming. Thanks in advance!

 

I would say no since the RR engine is a completely different beast than the F4i engine.

 

Curious as to why? To change the lift/duration of the valves?

You'd have to be incredibly carefull that the RR / F4i cams had exactly the same number of teeth, and radius of sprocket. Then - you'd have to hope the cam profiles were compatible... I'm not sure I see what your plan?

My guess is that you won't beat the stock cam unless you REALLY know what you're doing... a guy who builds motorcycle race motors would be the place to go.

 

I don't think just swapping cams is going to get you where you want to be. the f4i does have a slightly flatter torque curve, but I doubt its just the cams that make it that way. I would bet the bore and stroke are different as well. Not only would you have issues with that, but timing and fueling adjustments would have to be made in order to run the different cams. i don't even know if an experienced guy would tackle that nightmare.

I don't think the F4i has better midrange power. it does have a little better lower end torque, but for the midrange, I would bet they are very close. The 600RR is designed to run midrange on up, where the F4i is more off line into the midrange, but falls off on the top, which makes it better for real world driving on the street. for a race application, the 600RR would be a better choice. I can't think of anyplace at a track where lower end torque would be a benifit. If it was substantial, then yes, but the little difference there is between them, I wouldn't worry about it. The 600RR will sing past the f4i's lower end in no time.

Also, don't forget about gear ratio changes. if your worried about getting power down sooner, you can always change that aspect.

and as PG said, the only thing the F4i and 600RR have in common is they are 600's. The engines themselves are not even close to the same.

 

Keep in mind fellas he has this in a gokart application

 

We had to re-shim because one of the guys who took our motor apart, forgot that the shims are very very specific.

We are pretty good at making fuel adjustments, but we need more practice in advancing and retarding spark timing.

We have a guy whose specific job is working on our differential and gearing.

We need the low to midrange power and torque because the competition we race in is very tight. When we did a practice competition you could put it in 2nd and leave it there the whole time since the course is so tight.

If you want to see the kind of races we do check out
http://www.youtube.com/watch?v=WjuanO5lRKI
http://www.youtube.com/watch?v=HioV7dORv4Y


interesting things also happen at these events

 

with regards to leaving it in second --- might you want to change the gear ratio of the final drive to get this motor up into the power band? Yes if you change the gear ratio a lot you'll have to shift more, BUT you will be able to pull the power out of the motor more easily. A few shifts and a lot lower gearing will give you explosive power -- which would be far easier and simpler than changing the cams

Plus unlike cams - you can change the gearing track side.

just curious?

 

As long as your up in the rpms and don't fall out of the power, it should be fine to leave it in one gear once your under way. I honestly think the power you will loose at the high rpms by trying to get more low end torque will hurt your overall performance.

Do you guys have any restrictions for tire sizes or exhaust? the exhaust could potentiall be an area that is hurting you if your not running the stock exhaust. You may beable to fit some sort of flapper that creates backpressure on the low rpms then opens fully to give top end power. If your basically running a free flow exhaust right now, that too will hurt your low end.

If you can, find a stock exhaust and put it on for a test run comparision. A little bit of backpressure can really bring the torque numbers down lower in the rpms.

 

We have an intake restriction of 20mm. About the size of a nickel. It limits the cars around 90-95hp. After 10krpm or so the restricter cannot physically flow any more air no matter how much the pressure difference is. Thats why we are interested in grabbing up so much low end power. I'm guessing changing the rear sprocket would be an easy way to accomplish this rather than a final gear? The main reason I asked is because if we found a cheap 600rr engine for sale then we could buy it and swap cams. Just to leave more buying options open so we aren't just looking for an f4i.

 

this is exactly what i was thinking. these motors are build to flow real good up top. i'm not sure exactly how much performance you can squeeze out of the motor if you cant make decent power past ten. what are your limitations on the motor? if you're not allowed aftermarket cams have you considered cutting and re welding the sprockets back onto the shaft?