Racing Beat used to sell high compression rotors, but nobody bought them. You can ask if they have any available in their wearhouse, but that's about all I could think of. Like I said before, though, the RX-8 rotors wouldn't make enough of a difference between the s5 rotors and themselves to make the switch enough to warrant a change. I mean 9.7:1 and 10:1 is not enough of a difference that I would go looking for. It's not even enough to warrant upgrading fuel grades. Personally, I think that anyone that says that it's worth it to use RX-8 rotors in our cars either has way too much money to blow or is consentrating on the wrong aspect of the car. A good port job could blow away any difference that .3:1 compression would make. Now, with that said, I assume you are looking for higher compression rotors because your sanctioning body dosen't allow porting on the ports. If that's the case, just do what you can get away with, like port out the intake manifolds. That should make enough of a difference that it wouldn't be a noticable difference audibly, but you would probably make more hp across the board, enough to pass your competitors, at least.

 

Yes there is a SAE article on the position of the 'tub' in the rotor, Ive read it but sorry I cant find it.

Im not sure on this but if you tried to weld on extra bits to raise compression would that create hot spots leading to detonation? I dont think this is a good idea. 10:1 rx8 rotors will be enough methinks.

Rx-8 rotors can be used but you will have to modify them to retro fit apex seals. They arent made to pass the peripheral exhaust port.

 

Theyre cheaper.

 

Theyre lighter.

http://f2.autospeed.com/cms/A_0802/a...popularArticle

 

get ceramic coating in there, and have it a certain thickness. that increses compression.
the dimples would need to be ceramic coated as well as other parts o the rotor. its easy. tell them you want it twice as thic and your compression gets bumped through the roof.

 

http://www.thecarricos.com/ACRE/
SAE Papers.

Check check it out.

 

yep i was just about to say..... based on the geometry of the mazda 13b 10:1 comp is probobly as good as its gona get for reliable combustion with gasoline. a completley flat rotor with no "tub" would make for a pathetic combustion chamber.


the r26b only used 10:1 rotors and id image mazda would have pushed the comp. on that motor as far as possible.

 

Im telling you, you dont want to go much over 10:1,.. and MDR rotor faces make the most power, and is waht the r26b is, which is what fc rotors and rx8 rotors are anyhow. The biggest advantage of rx8 rotors is ther elighter weight, which would allow for 10k rpm with much less worry then with s5 rotors.

 

The best way to raise compression ratio is by raising volumetric efficiency above 100% using external means........

Aka forced induction, even if just a little bit.......

 

Like ram air? Were talking for a n/a race car here..

 

Ram air does work, I have it on my car. It only adds a slight amount of torque to third gear though, probably enough for a mph in the quarter at most.

Pressure wave tuning, the tournament effect (and variable dynamic effect in the S5 manifold), and inertial supercharging are all strategies used in NA intake manifolds to attain relatively high volumetric efficiency.

When it comes to density efficiency, the effects of intake manifold insulation can't be underestimated.

 

Welding will not be equal ever. Even if you get them to be the same compression across each face, there are other effects you must consider. One being the clearance you have from the face to the housing, you could seriously destroy them both. Another the weld is going to have different reactions to the heat of combustion. And lastly the most important, weight. What I mean by this is they have to be balanced to a T. If they aren't balanced to near stock you're either going to have a motor that shakes like a bitch, or you're going to completely snap your ecentric shaft in half.

- Steiner

 

I was recently discussing this issue with a fellow forum member, does anyone have any further info? He suggested that if CRs went above 10.5:1 two flame fronts would be produced. It seems to me that a LDR (leading deep recess) rotor might allow for a little higher CR, but it seems like that's the wall for the rotary engine. Perhaps the duel flame front issue explains why the Renesis requires 91 octane whereas other 10:1 CR engines with similar HP and breathing displacement can run on 87?

BTW: Is it just me or does 10:1 CR seem awfully low for a Lemans caliber engine? I believe the 3.0L V8s in the IRL run a 18:1 CR.

 

Wouldn't it make sense to make an incredibly close tolerance rotor that leaves mostly nothing but the "tub" of the rotor with air/fuel in it? Then when it moves past the point of highest compression, it opens up other areas for the flame to expand into.

 

BTW, if you really, really want to experiment with welding beats into the rotor dish, you could do it. First, you need to find a welder that is experienced and good at welding cast. Then, you need to lay your beads as evenly as possible. Now, you will need to get a CC measurement of the dish. Fill it with water, and measure the volume of water it will hold. Grind each newly welded dish so that each holds the same amount of water. Note that by "grind", I don't mean with an angle grinder. You're going to want to use a CNC table or other precision cutting tool so that you are removing the same amount of material from each face. If you overweld each rotor face, then you can remove material to a set depth, thus keeping balance tolerable. The rotors are not balanced from the factory as well as everyone thinks, so a little imbalance is not going to kill you.

But as Snrub mentioned, you will end up seperating the flame front into two halves. Not good. You'll wind up with an upper flame front that directly opposes the motion generated by the lower flame front...End result is a lot of power lost as the rotor tries to fight the pressure on the other front.

 

Whatever way the flame front travels, it is achieving the same goal of increasing pressure from combustion- turning the rotor. Isnt there flame fronts travelling outwards from the spark in all possible directions- up/down normally?
Can someone point out where im going wrong?

Quote:
You'll wind up with an upper flame front that directly opposes the motion generated by the lower flame front...End result is a lot of power lost as the rotor tries to fight the pressure on the other front.

Is this really true, it doesnt make sence to me, mabye I just need more explaining?

Is there any tech info on the 'dual flame front' out there?

 

You cant, because of the shape, A rotor that fits almost perfectly at TDC would hit the trocoid elsewhere.

 

tech info usually comes from aaron and icemark, and few others, if they don't know then you'll probably have trouble finding out

 

I think it has more to do with the fact that the ignition of the trailing pocket will be much retarded then that off the first and thus it will miss the point of peak torque transmission, as well as possibly incomplete combustion due to exhaust polution fromt he first event,..etc...bad idea basically

 

Unfortunately true. This is a good thread topic, I'd like to think that we could get some further answers here without Barwick having to go to the engine building/porting section on NoPistons to talk to BDC, Ito, et al. Anyone?