Hey I was wondering if one of you had the time and knowledge to answer this question:

When you port rotors you are increasing the displacement, but are you also reducing the compression?

Also, lighter rotors are higher compression correct?

Thank you in advance.

 

U don't port rotors, "porting" is changing the intake and exhaust port size. Ur not increasing displacement, just changing port timing, like cams do in piston engines. Lighter rotors r not nessessarilly higher in compression.

 

The most helpful thing you could do to learn a lot is call Racing Beat and get there FREE tech tip and catolog. You will be able to answer most your questions with that book.

 

So making the pockets on the rotor faces larger does NOT increase the combustion area? And if a rotor is lighter wouldn't it spin easier and faster thereby raising the compression? Thanks for more detailed answers.
I will call Racing Beat for their catalog but in the meanwhile maybe someone can enlighten me.

 

Nobody "ports" rotors. There are a few companies that remove material from the sides for the purpose of lightening or balancing them. In some cases they can get a full pound off the weight of a rotor. That is not a bunch of return for the amount of money they charge.

As you are referring to opening up the bowls on the face of the rotor, I have never seen it done. It would lighten the rotor but it would also reduce the compression ratio. It would NOT increase the displacement of the engine.

BTW: A motor spinning faster and eaiser has NOTHING to do with the compression ratio. Compression is based on how well the combustion camber seals and the difference between the total volume of intake compared to the volume of the chamber at top dead center. (Other parameters are considered like temperature, intake velocity, etc).

 

Well the rotors are hollow. This is to allow oil to splash/sprayed around inside them for cooling purposes. I am not certain how thick the face is but I would bet you would want to make them much thinner since they see the force of the combustion!

 

There were companies that would mill out the rotor faces to lower compression. Some would be as low a 7.5:1. The purpose was not to lighten them but to lower compression for high boost applications. When rotors are lightened and balanced, material is taken off of the sides of the rotor as well as the counterweights to match. This does make them easier to spin faster but it doesn't mean that you neccesarily can rev it up higher. For higher rpm use, ignoring a host of other precaustions that should be taken, you need the rotors side clearanced. It is similar to the lightening process but material is removed from a slightly different location on the side around the side and corner seals and in a very small quantity. This adds clearance so that the rotors can move slightly more side to side since the eccentric shaft flexes slightly at high rpms. If you added a center bearing this would be of no concern. Another trick is to use 2 side seals stacked on each other to help how the rotor centered better. This slightly increases wear but not so much that it is worse in terms of abuse than high rpm use.

 

Thanks for the insightful answers.