t-von

iTrader: (8)

Ok guys, I understand that Mazda has previously experimented with the larger 21A rotary engine.

http://cp_www.tripod.com/rotary/pg21.htm

Other than re-tooling, whats keeping Mazda from building these larger displacement engines now? I figure since Mazda previously has already experimented with the Renesis design why not go ahead and build these larger displacement versions using todays technology to produce a rotary engine capable of consistantly making over 300hp NA and much higher torque figures? These larger engines could prove to be more reliable than the 13b at these hp levels mainly due to the increased displacment and less overall stress.

Bottom line, I feel we need larger displacement versions of the rotary.

peejay

They might make more torque but I dunno about the HP, since the larger trochoid dimensions means faster apex seal rubbing at a given engine speed, meaning accelerated wear. They'd be more RPM-limited than current engines.

mwatson184

The intake ports can only flow so much. You may be widening the rotor housings and having more displacement, but this doesn't effect the intermediate housings and the intake port size they can support.

Marques

t-von

iTrader: (8)

Are you refering to the 15A engine which is based on the other rotary engines? The larger 21a engine could be engineered to have the larger intermediate plate.

t-von

iTrader: (8)

Peejay, yes the rpm's would be lower but thats not necessarily a bad thing for what could be considered a "Big Block Rotary". You wouldn't have to beat this engine to death to get the most out of it like you already have to do with the Renesis. Also apex seal technology has improved a great deal from 30yrs ago. Anyways, I wouldn't expect an engine like this to replace the 13b. It would be nice to have something else available for other applications.

Jeff20B

iTrader: (13)

Mazda should make a modern 15A so it can share side plates etc. I mean, c'mon. What's holding them back at this point?

peejay

Bear in mind that current rotaries experience exponentially worse apex seal wear starting at 8000rpm. This is for *any* apex seal, technology can't overcome basic forces.

Whether this seal wear is due to higher rubbing speeds or higher centrifugal forces, I need more info to say. If it's from higher rubbing speeds then the larger engine will be worse and the RPM threshold would be lower. If it was centrifugal forces, it would be a bit better (larger radius).

Jeff20B

iTrader: (13)

So with wider rotors, we could have a factory redline of only 8k instead of the Renesis' 10k or whatever it is. Since a three rotor Renesis is still out of the question, let's tell Mazda to build a modern 15A.

peejay

Yeah it makes sense, doesn't it?

You'd want the redline lower anyway. I'd hate to see how much a shaft another 20mm longer, with heavier rotors, would whip around in the middle!

rxseven

What's keeping mazda from making higher disp engines? Simple, fuel consumption and emissions.

Jeff20B

iTrader: (13)

Why are those things so important?

rxseven

They are to mazda if they want to sell their cars on the west coast of this country.

peejay

Or any other part for that matter!

Although if the 10A to 12A and 12A to 13B pattern is inferred, a 15A would probably be more thermally efficient than a 13B. (Notice how torque goes up out of proportion to displacement) This makes sense because increasing the rotor width makes the surface/volume ratio more betterful.

rxseven

Not the part where I am from
Oklahoma scrapped emission testing a few years ago so we can run what we want. Come to think of it we never had any *proper* testing to begin with, just an old rag in front of the tailpipe.

peejay

Oklahome scrapped emissions testing for cars that are already in circulation.

However for cars to be allowed to be sold new in the US they have to pass rather strict federal emissions tests. And the fuel economy for a company is averaged and the company has to pay a fine per car sold if they don't meet the minimums, and there's also a gas guzzler tax placed on individual models that fall below certain levels (it's also a sliding scale as well).

Even the I/M240 testing (short drive cycle on a dyno) are a complete joke compared to what a has to be done on a Federal emissions test. We're talking huge bucks and a big time factor as well. The complete vehicle emissions are tested, not just exhaust emissions but also evaporative emissions, and not all evaporative emissions come from the engine. (Ever wonder why the "new car smell" has changed in the past few years? New car smell is a form of emissions! Those plastics evaporating into the air contain HC's and those *are* counted)

rotarypower101

iTrader: (1)

Because of precedence. It has been proven that a NA will outlast a forced induction rotary twice over. Combine that with big HP numbers and better fuel consumption and you have a winning combination.

If the rotary is to remain to the end of the dino days, it will be because of materials science if you ask me. I personally would like to see a variant on a 15A platform, increasing the volume and decreasing surface area is exactly what needs to happen.

NCSU3rotor

If i was mazda i would try and bring back the cosmos 20B's in a new gen rx-7s with the new renesis tech. but im not mazda. by the way with skyline coming to america, the rex should come back as well, what do yall think?

tweaked

iTrader: (4)

i hear from SCC they are at the drawing board for a turboed S7

peejay

a turboed S7? You mean a Saleen S7?

I hope you don't mean Series 7... the final RX-7s were Series 8. Any fourth-gen would start off as being a Series 9.

now

iTrader: (1)

i thought there was a 16a in the works.
matt

peejay

If Mazda goes by their historical 10mm additions in rotor width:

60mm = 10A (984cc)
70mm = 12A (1146cc)
80mm = 13B (1308cc)
--
90mm = 15A (1470cc)
100mm = 16A (1632cc)
110mm = 18A (1794cc)
120mm = 20C (1956cc)

Note there was a 13A, it had 70mm wide rotors and a larger trochoid dimension. Also I listed the monster twice-as-big-as-a-10A engine as "20C" because it'd be the next 2.0l rotary displacement engine after the 20B.

Wargasm

Mazda has got to wake up and realize that they're competing with 4-500 hp Corvettes, Vipers, and Mustangs over here in the RX-7 class. In the RX-8 class, they're up against 250-350 hp cars roughly....

If they want to sell anything performance-oriented over here, we either need to see a <2000 lb car (fat chance) with a Renesis, or something with a 3... or dare I say it.... 4 rotor engine. The turbocharged 3 rotor is way more likely, so I think that's the way they should go.

I've said a million times that they could have a lineup of 2 rotor, 3 rotor, 3 rotor turbo.... That way they can sell more units of the slower model and then price the top of the line 3 rotor turbo around 40-50k.

Oh well they won't listen to me, and they won't get any of my money.

Brian

peejay

Sub-2000lb would kick complete ***. IN maddox's words, they'd have to import colons from other countries it would kick so much ***.

The only problem with 3-rotor or 3-rotor turbo would be that it would get **** fuel economy. Mazda vowed in the 70's that they would never again sell a car in the US that qualified as a gas guzzler. That is why we never got the turbo convertible, the fuel economy would have gone below gas guzzler level.

t-von

iTrader: (8)

Slightly off topic, but if Mazda built a 2000lb car like the Lotus Elise with a Renesis would be freaking insane. Hell that car with 190hp Celica motor already runs 12's in the 1/4. A Renesis could make it a 11 sec car.

Anyways Mazda needs to get off their asses, find that lost passion they once had, and start experimenting again with other possibilities.

CARLiTO_

too bad they are getting fucked by FORD in the ***