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why not 3-rotor?

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Old 03-06-2003, 02:18 PM
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why not 3-rotor?

Let me just say that the RX-8 seems almost perfect with one exception. It needs a tad more horsepower and definately more torque. Now before I get flammed I'll let you know that I used to drive a Honda Prelude so I know how much fun it is to drive high RPM's and row the gears....but there were plenty of times I wished that I had the torque of a 6 cylinder so I didn't need to be at 6000 RPMs to have any acceleration. Sometimes driving at high RPMs can seem obnoxious, especially with performance exhaust.

Problem: torque and horsepower

Solution: 1 more rotor

I figure that with a 3 rotor RENISIS you could have close to 200 ft-lbs of torque...if not more and at least 300 horsepower. The cost of this would be added weight to the engine and drive train and crappy fuel economy...but hey I can live with that if it means 1/4 mile times in the low 13s. I would also assume that the engine would be less stressed than a turbo or supercharged 2-rotor and thus last longer and be a little more reliable.

I know this is only a dream world but I think the world would have been turned upside down with a car like the 3 rotor RX-8. I can't think of what the magazines would write as negatives.

Anyways I'd love to hear what everyone elso thinks.
Old 03-06-2003, 02:25 PM
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I had heard something about 3 rotors, I thought it was primarily for a future power version of the RX-8, or possibly for the RX-7. For me, I think a better solution to the current 2-rotor question of torque in the lower RPMs is a supercharger - it gives a larger kick in the lower range where you need it, without needing to blow exhaust in the higher range. It's more controllable too, depending on who builds it.

BTW, I have a Prelude too - kick *** car, it's going to be hard to justify spending 30k+ for another car when this one is still so much fun. Do you really think it'll be 30k worth of better than the Prelude?
Old 03-06-2003, 02:37 PM
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I'd have to agree with the wombat that a supercharger is the perfect solution to the RENESIS 'lack' of low range torque. And the cost and complexity of installing a supercharger on the RENESIS will be a LOT less than that of building a 3-rotor engine.

Also, keep in mind that we haven't seen the RX-8's engine compartment so who's to say the 3-rotor extra width will fit?
Old 03-06-2003, 02:47 PM
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remember that this is the first year for this car and noone has one yet! there is always improvments in following years- have to leave yourself a little room for improvemnt after all, or things would never progress and that would get a little stale after awhile don't you think? :D
Old 03-06-2003, 02:47 PM
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I thought because of the Renesis' side ports it would be hard to add a third rotor as the middle rotor wouldn't work. Someone correct me or explain what I really mean...
Old 03-06-2003, 06:08 PM
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Originally posted by pelucidor
I thought because of the Renesis' side ports it would be hard to add a third rotor as the middle rotor wouldn't work. Someone correct me or explain what I really mean...
yeah, good point. OR
can they easily add some more mms to the rotor width???

this is where i started back when i first joined the forum. talk about a crash course! it's great.
Old 03-06-2003, 06:33 PM
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Originally posted by pelucidor
I thought because of the Renesis' side ports it would be hard to add a third rotor as the middle rotor wouldn't work. Someone correct me or explain what I really mean...
Don't the current 3 rotor setups use side port intakes and peripheral port exhaust? If so, then it should be no problem to have all the ports in the side housing, ala Renesis.
Old 03-07-2003, 08:11 AM
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Originally posted by DisneyDestroyer
BTW, I have a Prelude too - kick *** car, it's going to be hard to justify spending 30k+ for another car when this one is still so much fun. Do you really think it'll be 30k worth of better than the Prelude? [/B]
Ohhh this car will be way better than the Prelude. Just think of all the advantages the RX-8 has over the Prelude. Rear drive, 6 speed, better access to the rear seats, better handling, more linear power, ...etc. Ohhh this car will be well worth the 30k.

I also think of it this way. We just bought my wife the new Mazda 6. Now the 6 is as fun to drive as the Prelude. I might even go as far as to say the 6 is the most fun car that I've ever driven (other cars I've driven for awhile: 1998 Prelude, 325 BMW, 328 BMW so not a long list). Now the Rx-8 is going to be better. The only bad thing....I can't buy it until ~2006 (I want to first pay off the truck ). The one positive is that I'll be able to watch the evolution of the car. Know if they're going to add forced induction or have the RENESIS spin to 20k RPMs, hehe.
Old 03-07-2003, 09:50 AM
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A tri-rotor wankel will require 6 more inches of room, a longer rotor (90 vs. 80 mm) will require only 1 more inch.

Which one do you think will fit?

Also an extra rotor will add an extra 50 lbs, whereas the long rotors will add 5 lbs to the engine weight. Think of the weight distribution. 52/48 is okay 53/47 no good 55/45 is **** poor for a rear wheel drive car. Anything more front heavy is laughable.
Old 03-07-2003, 02:10 PM
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i could handle 50 extra pounds for the power benifits received by throwing a 3 rotor in there. As far as the weight distribution, mount the battery in the back, ala miata, bmw, etc. still have the 50/50 distribution, and helluva lot more power. I haven't ever had a chance to drive a 3 rotor, but everthing i've read says it does everything the 2 rotor does better. much more torque, still incredibly smooth, and apparently the exhaust pulse pattern is very similair to the marenello v-12, which is one of the sweetest sounding engines in the world.
Old 03-07-2003, 11:51 PM
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A tri rotor would sound like a 9 cylinder engine if you used a single exhaust system.

The wankel as is should sound like a single exhaust 6 cylinder engine ala 350Z
Old 03-08-2003, 12:16 AM
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yes, the power stroke overlap is the same as a 6-cylinder engine.
justinm2, you're thinkin' of a 4 rotor which has the same overlap, and i personally don't think it sounds anything like a small displacement Ferrari V12...

anyhoo, back on topic, amgtortoise, Buger, me, and a few other fellahs have discussed this to death in the Tech section...

basically, the first largest deterrant to a three rotor is cost: many more expensive bits (like new centre housings, a two peice e-shaft) and some R+D to get the thing running right...
the wider rotor idea needs only have a longer e-shaft (like the 10-15mm extension, only on the journals), wider rotor housings (those same 10-15mm, stretched in the middle, no funny re-engineering), and of course those 10-15mm wider rotors. that's it.
because of the increased mass of the rotors, and the decreased strength of the e-shaft (longer), the rev limit may not be as high (and i'm talking the LIMIT... the RENESIS can do a few more rpm than the 9k redline: it just starts to choke after 8500, and Mazda needs it to last a long time), but it'll make all that torque (and obviously way more power) people are bitching for...
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