10:1 doesn't sound like an incredibly great idea when mixing with large amounts of boost tho...

 

those are for n/a set-ups

 

there's people already boosting 19psi+ on Renesis rotors, the only problems were more power and faster spool... it's all in the tuning

 

As far as i understand they take the S4 TII 8.5 CR rotors and modify those.

 

wow, that's impressive. But with the trimmed s4 tii you could do 30+psi.

 

with proper fuel and tuning the same can be said about the 10:1 rotors... of course at those levels it would be wise to start modifying more than that, pinning the block to keep it from twisting itself open for example. Let's not turn this thread into a "low comp vs high comp for turbos" debate, I'm sure it's been covered before.

 

Do you have to rebalance the whole assembly when only doing a scalloped modification? Or is it a scalloped lightened rotor package deal?

 

Carlos will have to chime in himself here but if I remember correctly, the port phasing modification can be done to any rotor. He chooses the Turbo II low comps for a couple of reasons but related to the n/a rotors, they're better, thicker castings on the rotor face. I do remember him saying he could do it to the higher comp n/a rotors as well.

 

on a side note, how much weight is shaved off the rotors? scalloped, and lightened?

 

I'm sure that in all these years of using the modified rotors, CLR (and others) must have dynoed the results... I'd like to see some examples if you have them available for posting.

Brian

 

The rotors are lightened to 93+ spec to facilitate the use of the stock counterweights. I have to answer the low comp vs. high comp question a bit here...and this is coming directly from Carlos, not from me. While one can run high boost on high comp rotors, the safety window is so small, I personally wouldn't want to test it out on a $7K motor. One would be able to run more boost on 93 pump (which is what I'm referring to here) and have a greater margin of safety. In the end, you'll make more hp running low compression rotors with a higher boost level than you will with high comp rotors and lower boost levels. And you'll be safer at the same time. High comp rotors require a pretty fast processor and a computer with good resolution. It's a no brainer. I'm sure a Haltech E11 or Motec would be just fine :-) Not so sure about say a Power FC with it's 20x20 cell and 8 bit processing.

The phase porting (scallops) do not lower the compression ratio below that of the normal TII rotor. Carlos said it would "seem" like they would in simple fluid dynamic terms but it's not the case (and I'm sure above my head!).

The other reason the S4 TII rotors are used is because of their casting quality. The 93+ rotors are the WORST out of all the rotors Mazda has produced. Specifically, they vary by upwards of 50 grams each (not very consistent in weight) and the rotor face thickness also varies greatly in addition to being too thin. The Renesis rotors are of higher quality and their phase porting is much, much smaller. I don't know how thick the face is on the Renesis rotor, but I think Carlos had one there and they do use the Renesis rotors in n/a race engines like PP 20B's and what not.

In the end, it's your money. If you go with high comp rotors in a race-only vehicle, hey whatever floats your boat. Carlos will be more than happy to machine a set for you. You'll see no loss in bottom end or response if the car is tuned properly (I actually run NEGATIVE split under vacuum).

As for dyno stuff, it's coming. If you read the last few posts in the CLR post, you'll see I'm waiting for the local dyno to be rebuilt. Coils burned out and have since been rewound and are ready to go in. I have unlimited use of this dyno for free, hence the reason why I've waited. That and the grenaded oil pan. I'm hoping to have dyno results in the next few weeks, shooting for 450ish on pump with a GT40. Another motor, running the low comp rotors (but no phase porting/scallops) made 490ish on 93 octane using a larger compressor. The dyno run is in the dyno/time slip section. Car is used for track days and the engine has been going strong for three years. Made over 180 runs on the dyno at WOT, which was apparently a record for any type of engine at this particular dyno.

Plenty of people have dyno'd the rotors. 99% of the clients are pro-level racers from around the world, most of which don't advertise that CLR is building their engines. That includes road race AND top level drag racers who shall remain nameless! CLR won the SCCA GT1 championship in 2003 with a 20B n/a. As much as we'd like to think the good ol US of A is the center of the universe, there's much more rotary racing going on in various other parts of the globe where they haven't been outlawed or penalized to the point of being uncompetitive.

 

would it be to costly to have cast titanium rotors then machined for use, I know F1 transmissions use a cast titanium casing, so it can be cast , the weight would be between 5 and 6 lbs, is weight that important, of course counter weights could be lightined also to help the total mass. j ust a thought RON

 

Why do people always say titanium like it's the solution to everything? Ghraargh.

Machining would be quite expensive for the same reason that it's not suitable for a rotor... galling. Plus, casting it is far from trivial... and really, it's still pretty dense. There's far better materials if you do some research.

 

Titaniun seems to be the material of choice for the opiniated

Why not use Un Obtanium...... Its even better !

 

What, like Al-Be alloys?

Actually, did some research and there's some Al-SiC metal matrix composites that would be pretty suitable... though I've this funny feeling that low volume production runs of investment cast rotors would still be kinda out of my price range.

Still, something to try someday.

 

The 'Obtanium' reserves have been depleted fore some time now!

 

Oooh, me likey. 29° earlier port timing is a bunch! Getting the intake flow going right after "TDC" instead of pulling in exhaust is great. I'll bet this would make power on just about anything including engines with stock exhaust. There is a local road race class that outlawed bridge porting to keep the RX7s in check. This is exactly what these guys need.

 

BOY you guys give up easy, I was only trying to advance the rotor thing, how much money Mazda must have spent on the ones they use now? anything good costs money, I was looking at the weight thing. never said it would be easy, you have to try it before you condem it ! HE-HE must have struck a cord on that one! RON

 

No, you completely missed the point. If you're going to the trouble of custom casting rotors, titanium's not a very good thing to make them out of. Even ignoring the problems with titanium that make it unsuitable for use in sliding applications, the problems with casting and machining them that would drive price way up... it's still pretty dense! Yes, it'd be lighter than cast iron, but so what?

The Al-SiC MMCs that I was talking about are pretty easily castable, have structural properties pretty similar to cast iron (including thermal expansion) are very long wearing in sliding contact, but are 2/3rds as dense as Titanium alloys. So you have something that's better *in this application* in every single way... and is also cheaper.

Or hell, why not go all out? Ferrari was using aluminum / carbon fiber MMCs for their F1 uprights... why not Al-Be / carbon fiber rotors? Ooh, or Al-Be-Li / carbon fibre MMC... that would do it. (yes, I'm going to extreme examples of unobtanium)

Titanium has its uses, but it's not the wondergod solution to every single problem like people seem to think it is.

 

If you wanted a semi-realistic material to use, in the last couple of years they've come up with some magnesium alloys that do away with disadvantages of past Mg alloys. The new BMW 3-series block is Mg, so I imagine they're using such an alloy.

Banzaitoyota said that he built an engine with Renesis rotors, tore it down and built it again with S5 rotors and found a 8hp difference.

 

Well, What do You expect ?

The F-1 guys took it ALL, ..... and then ran OUT !

 

wanted to add
we just started a new motor in my friends shop car
which he sourced a used set of CLR rotors

and OMG! those that thing sound bad ***
sounds like a bridge port with NO BRIDGE!

 

Nah nah... they're just stockpiling it until the rules change. There's a big hole in the ground somewhere in Italy filled with the stuff, y'know.

 

Went racing this weekend, & found out :

The "Irakies" were involved with the sequester of the remainder available earthly stock of " Un Obtaniun" elements.

Wasn't just the F 1 guys,

This stuff, apparently is required for (WMD)'s : Weaponds of MASS Destruction.

WOW !

The Italians have a big problem.

 

Hmm, so what would one need to place rx8 rotors into a 13b(t) engine? lol