tips on building a high rpm motor

[NoDOHC]

Check the clutch speed rating, if you intend to rev past the rating (or even to it) you should have a scatter shield.

Mine is rated for 9500 RPM. This is a pretty typical rating for a performance rotary clutch. You can get a better rating for NA drivetrain. 9500 is about it for turbo drivetrain.

Also, check your alternator (you may have to underdrive it), I ruined my s4 alternator by turning the rev limiter off, forgetting that I had, and trying to see how fast I could go in first gear. The fan belt broke at about 52 mph - about 10,000 RPM (because the alternator had seized).

For future reference:
I have run my engine for 3-4 hours on the dyno on several occasions with no issues at 9500 RPM. I had to do a teardown about 6 months ago due to thermal expansion in the spark plug area killing two apex seals. When I tore the engine down, the bearings looked like they were brand-new, the rotors had not touched the housings, the engine was in excellent shape with the exception of the blown seals (which really didn't do much damage, as I was able to re-use the rotor).

I have an 88 TII engine, stock planetaries, stock rotors, stock counterweights (using auto-trans counterweight in the back) stock oil pump, stock oil pressure regulator, and thermal pellet in operation.

The rotors have been clearanced, polished and lightened to 4.2 kg and the rotating assembly has been balanced with these rotors. I am running 15W-50 Mobile 1 synthetic oil.

To clarify - I only revved to 9500 RPM in second gear on the dyno, as the engine would overheat before I could get there in 3rd or 4th, thus the engine wasn't running at high speeds for extended periods of time.

Last time on the dyno, I made peak power at 6800 rpm (mild street port). This makes the 9500 RPM rev limiter seem a little like overkill... You might want to make sure that your porting supports making power at that high of speed before you spend a lot of time and effort worrying about it.

If you are turning that fast, You should definitely make the modifications that everyone suggested above (especially hardened planetaries and balancing). I merely posted what I have gotten away with so that you have some peace of mind.

Spark notes version:
Check clutch rating
Balance engine (absolute must)
Verify porting supports higher speeds
Even semi-stock rotaries will handle high speeds for short bursts

[j9fd3s]

Originally Posted by NoDOHC

Even semi-stock rotaries will handle high speeds for short bursts

yep. also the stuff that they outline in the competition prep book (www.foxed.ca) from 1979, has eventually become standard on the street engines.

the FD engine has the hardened gears, multi window bearings, high oil pressure, oil pan for corners, etc stock.

the Rx8 has the side clearanced rotors. which is applied retroactively, so if you buy new FC/FD rotors, they come side cut too

-mike

[FC Zach]

And also, make sure your drivetrain is bulletproof. And no matter how solid of a drivetrain you think you may have, you'll have to accept the fact that it won't last long. Ask me how I know, I just blew my fourth trans tonight, the latest being a JDM S5 T2. Even though it outlasted all the others combined I knew that one day it too will go and its life ended tonight. RIP tranny