currently rebuilding a FD 13b turbo engine, would like to increase the RPM limit , have been told that at high RPM the rotors can crash into the side plates, whats the best way to make more clearance to avoid this?

 

Use a lathe and very sharp tooling to remove .012" from each side from the tip to the outer oil scraper groove. Pad the jaws so no dents develop in the rotor. Only the tips will touch but doing the whole side is easy and quick. I have never bothered to rebalance anything after this but technically it should be done.



The rotors balance each other. The counterweights take out the rocking couple. If you then lighten the rotors on a mill, the rotating assembly must be balanced.



Break all machined edges with a small stone, and clean the rotor several times. Then take it to the car wash and use the high pressure wand. The little bits love to stay inside the rotor until you start the engine.



Lynn E. Hanover

 

Hey Lynn I never ask for these because I can usually visualize what you are talking about. But in this case could you post a picture of a rotor and shade or outline what you mean? I would really prreciate it.



Thanks in advance.

 

Sweet info, Lynn.. Thanks



I have been thinking about this for a while, but figured the rotors would need rebalancing.



*Grabs rotors, runs to the lathe*

 

Ah thanks mate, thats exactly what i wanted to know, have spent countless hours trying to google this info but couldnt find anything any other tips on modifying for higher RPMs? will be using rx8 bearings and stationary gears, PTS seals, cross drilled eccentric shaft, fully balanced rotating assembly, stud kitted instead of dowelling, was thinking is there any way i could line bore the engine?? like you do on the main bearings on a piston engine?

 

Sounds like you've got it figured out for the most part. You should also pay a lot of attention to the oil passage, they are horrible from the factory..

 

will be using a new oil pump, was going to look at externally feeding the rotors like they do on the 20b engines with an oil manifold, might not be needed though

 

If I hadn't lost my damn shop camera, I would post a picture of what we do. We don't use a manifold, but have the oil lines external...

 

oh that would be great if you could take some pics eventually

 

The picture would be a rectangle or side view of any rotor. Your job is to make the rotor thinner than it is now by a total of .024" or .012" from each side. ( what you see in an end view, or the triangular shape)

is where the material is removed.



The crank shaft is quite flexible and allows an "S" shape to develop at high revs. This allows the rotor to tip at a slight angle between the irons and the part of the rotor around the corner seal hole will drag on the irons. So that portion that is likely to touch or drag is reduced by .012". You can remove material from the tip to inboard just an inch or so, or go right to the side of the scraper ring hole. Easy to get it the same if you go all the way rather than stop at 1 inch or one and one quarter inch.



I also remove about .005" from each thrust face that keeps the rotor centered between the irons. Notice that some overheat failures include irons completely hosed by the thrust faces touching without enough oil film?



(Big black circle around the center hole in the iron).



When you pick up a rotor with one hand, you thumb and fingers are on the surface that must be reduced.



If you still need a picture (as I often do) I will assemble one.



Note also that mods like this are not required for operation at or below the stock red line. (but what fun is that)?





Lynn E. Hanover