Time for me to jump in lol...

For street no more than 8k RPM Clearancing the side of the rotors is not necessary.. unless the costumer wish to have it done.. for future hp needs..... Simple... :)...

Jump!

perhaps I'm missing it in the deleted posts on the other thread, but I thought that Charlie said he intends to use his motor/car for high RPM (9K) and track use....meaning that the clearancing was necessary?


As a point of personal education, what is the possible downside to clearancing rotors for a street car? Possible side seal wear?

I think possibility of increased blow-by, which ultimately will lead to shorter engine life?


-Ted

I'm curious, how would blow-by lead to shorter engine life? I understand how it could reduce power, but it would seem to me that greater clearance on sealing surfaces reduces seal wear and would increase engine life in exchange for maybe less fuel economy.

Didn't Mazda increase side seal clearance drastically on the Renesis? They must have done that for a reason, right? I personally would trust Mazda engineers to have better data than the entire engine builder aftermarket put together.

That is correct. I also plan on driving the car on the street every chance I get. I got the clearancing done for extra insurance when I will be running the car in the higher rev's. To me its worth it.

Blow by would not increase the side seals still do there job. Have Phil call all of his engine builders to find out

Joff,
If mazdas engineers were puerto rican, we would have some of the badest production cars ever :D.

Just got off the phone with Paul @ Mazmart (home of Rick Engman). Paul asked Rick about this for me and Rick says he does not clearance the rotors... Not even on his race engines.

LOL!

So, What happened?? I thought you said you are done with this??

Hmm.. I guess you were lying to me:)

Anyhow, Another thing you guys can do is listen to Glen like flies on shit :)

Just saw this thread show on top.

I have been building these things since 72 and have never seen this as a failure point, street or race. The IT motors spent their lives near 8 and the GT motors at 10K.

Resulting damage from bad bearings and or bad build or gear walking, yes, many.

Here are my 2CS.

I do not see the necessity or any cost benefit. Mazda does not include it as one of their build hints, and it is not in my copy of the Mazda RX7 Competition Preparation and Service Manual. I do not have the latest versions though so I will stand corrected if that modification is recommended. (remember I am the factory freak) I do not know of any of the top builders that do.

But I will not dismiss it completely either. Who knows what the future and innovative experimentation may result in. I will leave this one to those with deep pockets. I’m having enough to do with flat bottoming the open road car and working on this buggy.

When a rotary is built properly to spec with new parts or parts that meet spec it will perform and be reliable. It is then to the client to take care of it. A good build isn’t anything if the oil isn’t changed or it is run out of water. (but the light wasn’t on that long, just until it stopped.) They may come in the shop that way, but they leave knowing the proper care and feeding of their investment.

Side seal clearance was not increased drastically. There is no difference between SS and CS. The clearance of SS in the rotor is different because of the design of the new SS.
Rotor to side housing clearances are less .12-.21mm for FD, .05-.19mm for Renesis.

If you are inducing any blow by it will shorten the life of the motor. First by contaminating the oil and building up combustion gases in the oil containment system. Beside loss of power.

Amen!

Thank you for your input Rx4ur7!

That's interesting.. I was looking for that information about FD vs Renesis clearance.. Thanks for posting that.

Same thing was also told by another very experienced builder.

Over the weekend I met up with the guys from SpeedSource and asked them if they clearanced the rotors on their 20Bs.. They said, "yeah we do. But VERY little". I ask how little and they said they barely clearance it..

Also they told me their peak HP is at around 8500RPM.

Just thought I post what I found out :)

Interesting thread... I'm no engine builder but I've heard at least a couple of piston guys mention using increased piston-to-cylinder-wall clearances to avoid contact due to the piston expanding when it sees a lot of heat (high boost). Due to the shape of the piston inside the cylinder I don't think those guys would be need to be very concerned with flex or eccentric shaft wobbling... I would venture it's just expansion from heat.

I suspect there are some similarities and some differences between how the piston engines and a rotary engine will react to the additional heat (not a lot of forged aluminum rotors out there), but something along those lines may account for why some builders are suggesting that increased clearances and others don't. I suspect it may be more important in engines that are seeing a lot of heat. This may explain why one builder observed a higher percentage of FD failures than FCs... it's pretty much a given that the FD runs hotter.