Hi all,
When using beveled rotors to what degree does beveling the rotors improve performance when done in conjunction with good porting on the primaries and secondaries (i.e. a streetport)? Do you get any gain with beveled rotors if you have already ported the engine or is this really only necessary if you can't port the engine for some reason, such as racing class, etc? Is this a situation where beveling the rotors alone gets you the performance of a good porting job so you end up doing either beveling or porting versus both? Also if you both port the engine and bevel the rotors what effect does this have on the engine in terms of driveability on the street?
I know these are alot of questions, but I'm thinking about what to do to the next engine I have built and now that I have a real job money is not much of a question right now.
Thanks in advance,
Peacedog

 

it all comes down to what you want to accomplish and what you're willing to sacrifice. machining bevels into a rotor can open a port earlier, close it later or both. keep it reasonable and idle and drivability are not going to be affected.

rotor bevels cannot replace porting, they can just enhance it.

 

what he said^^
beveling rotors accomplishes the same thing as porting. porting is slightly more effective because you change not only the timing, but also the port area, so you get a little more flow in addition to more duration. beveling rotors only increases the duration. In any case, the same rules apply for power increase vs drivability. More porting/beveling= more power, less drivability, especially after a certain point.

pat

 

On the subject of beveling and porting, I am curious about some things. In bridgeported engine, there is a good bit of over lap, I'm not concered with how much. Now on a street port, there is less overlap, correct? Now does beveling the rotors change the overlap any or just the port timing?

Would a heavy streetport and beveled rotors produce as much power as a bridgeport with no beveling, or make more streetable power? Would beveling be the way to go to reduce overlap then and/or improve idle and streetability? I don't have a good image of the rotor and different ports to visualize this stuff.

 

If you read what was said above, thats already been answered. Beveling increases overlap just as much as porting, so the streetability changes just as much. The only difference might be that you could get the power without having to worry about the bridge breaking.

 

Hi all,
I'm not sure if this is a thread hijack,but it might provide some clarity to the issue of beveled rotors. In either this forum or the racing forum a writeup was given about beveled rotors and compression ratios last week. Someone from CLR gave a very clear writeup of what this can do for your engines. Bottom line, E Prod 12A engines can produce about 230HP at the flywheel using beveled rotors, large streetporting and lightened internals. The comment was made that this would be a fairly "peaky" engine and would need a very low restriction exhaust to make this kind of power, i.e. even if you built the engine properly you probably couldn't get this kind of power on the street due to need to limit the exhaust noise by using a more restrictive exhaust system. The writeup was really good and gave several concrete examples of what beveled rotors can do for you. I'll see if I can find the thread.
Regards,
Peacedog

 

Actually, I was thinking of two separate posts. One dealing with CR and beveled rotors and the other was about E prod engines. They are here:

https://www.rx7club.com/rotary-car-performance-77/beveled-rotors-cr-621256/

https://www.rx7club.com/race-car-tech-103/what-goes-into-e-prod-engine-622839/


As someone who doesn't really know much about these kinds of engines and their associated modifications this answered alot of questions for me.

Regards,

Peacedog