Man Patman your a TOOL! You have one of the most knowledgeable rotary builders giving you advise. Not telling you what to do but advising you on what to do and your not even hearing anything. Why don't you search and find out who GT1-20B is? You'll find the name Carlos Lopez like CLR Motorsport's Carlos Lopez. That guys been building and racing rotarys at the professional level for years. I think what you have lost sight of is the HP number you stated you wanted to achieve 650whp. And then the question you asked "which rotors?" It seems that you have had your mind set on the higher compression rotors so why did you even ask the queston on which rotors to run. 650whp is no small feat even with a 20B and yes you can do it with high C/R rotors but with pump fuel what will be the threshold of boost you can raise and are you going to add water injection or run higher octane fuel on the streets. Point is you are not going to have to worry about those things if you go with the lower compression rotors. You'll be safe running higher boost with pump gas. Maybe you should ask GT1-20B how his 8.5C/R lightened to 93 spec weights would work on your application. Here a little taste of the craftsmanship of this man. Good luck to you and your endeavor. But please next time don't ask for opinions when your dead set on what you already want to do. Hey you are the "Resident Know-it-All"

 

i did not ever ask anything about compression ratios. all i ever asked is if anyone knew the strengths of various rotors' castings. JUST IN CASE YOU MISSED THAT, MY QUESTION WAS ABOUT THE STRENGTHS OF THE CASTINGS.

I am sick and tired of this forum. It is full of people who have lots of advice, generally not very useful advice, that they feel necessary to dole out as often as possible. I try very hard to ask very concise and specific questions on here, and i still get all this **** about stuff that I dont need help on.

And, if GT1-20B is Carlos Lopez, then I'm sure he could answer that question in a second, and I would appreciate it. But no matter who you are, if you give me advice that conflicts with what I know to be true, both from experience and from mathematical/theoretical analysis without any facts to back it up, then I am not going to just go along.

GT1-20B it is obvious that you know a lot about this sort of thing, but that doesnt necessarily mean that your experience is applicable to my goals and my specific project.

In reality, I have had poor luck finding a core 20B, which I was afraid would happen, so I am going to be just working with the stock block until I get the time and money for the build that I want. But I eventually will have a high compression 20B, and I am completely confident that it will meet all my goals.

In truth, if i can ever get some data on the 9.7 rotors, I am afraid that I will find them too weak for my comfort. In that case, if I havent pissed Carlos off to badly by questioning his apparent omniscience, I was considering sending him some 9.4s to port phase and trim down to the later model weight.

Anyway, this thread is obviously going nowhere, so I'm off to do something more useful with my time.

thanks for all the advice. and incidentally, just because I dont agree doesnt mean I am not listening.
Pat

 

Hey Pat,
The S5 and up castings are thinner don't know exactly how much thinner they are. The S4 to me are the ticket and if you want higher compression the 9.4's should work great for you. I also contimplated using the 9.4's on my recent motor but my car is setup for the dragstrip only so higher compression and lots of boost is not an issue for me, running C16 fuel. But my personnel preference on a street driven car is lower compression and higher boost. Nothing wrong with S5 rotors as long as you get a great tune on it. Detonation is a mother and I have collapsed the rotor face on an engine 13brew. I got a couple junk rotors sitting around if a get a chance maybe I'll drill some holes through them and take some measurements. Good luck.

 

yeah, the s4 9.4 rotors worked great in my last motor, but I'm shying away from having to have them lightened and rebalanced. If you could measure some s5s, that would be awesome. Ive got lots of s4s i could cut up.

Anyway, like I said, my plan for right now is to run the 20B stock with a relatively small turbo, maybe 450 hp. then later this summer I will tear it down and do a full engine build, so thats when I have to decide on rotors and things.

thanks for the answer.
Pat