skillmaker

People tell me a three-rotor Renesis can't be done. They believe it is because of the peripheral porting.

And yes, I know I sound like a broken record, and some may think I'm an idiot. Sorry (just a little, not much). Every time people discuss turbos and superchargers, they presume that is the only fix.

Lemme see - right now, your Renesis has:
End plate A
Rotor Housing A
Center plate A-B
Rotor Housing B
Front Plate B

So, what would be so hard about:
End plate A
Rotor Housing A
Center plate A -B
Rotor Housing B
Center plate B -C
Rotor Housing C
Front Plate C

The end plates (front and back) provide peripheral ports to the closest rotor, and the center plates provide peripheral ports for intake/exhaust for two rotors, right? You'd need a different eccentric shaft, and some different intake/exhausts, and re-arrange some things in the engine bay, as well as a different ECM unit. (Maybe the battery in the trunk, and some relocated fuse boxes and etc).

And, using modern math, we see that
2 rotors = 238 hp = 119HP per rotor
3 rotors x 119 hp per rotor = 357 hp. (or approx 300+ rwhp)

A 300rwhp RX8 would really be a flagship sports car, with acceleration and handling to match the top end cars costing twice as much. This, my friends, would truly be a Mazdaspeed 8!

Look, I can't guarantee this is the last time I'll whine about this. We add turbos and superchargers because they are easier and obtainable and aftermarket. Manufacturers have started using turbos because it is a reasonably inexpensive way to add HP to a 4 cylinder engine. However, how many people, honestly given a choice, would rather drive a turbo than have more cylinders available? I for one would rather drive a V6 than a 4, a V8 rather than a V6, and given the opportunity, a three-rotor rather than a 2.

There. I've said it again. My apologies in advance to everyone who is so enamoured of turbos and superchargers. I would rather have more engine.

zoned

Mmmmmmm.....3 rotor..........

phartknauker

Would be a nice option at the dealership for sure!! v-6 mustang or v-8 GT... 2-rotor base model or Mazdaspeed 3-rotor !!! Woohoo!!!

Tigerfootball

i thought the 3 rotor was basically impossible to make emissions legal in the states. it would be very nice though.

StewyRX8

I would love it, but doubt it will happen based on sales...

Rootski

iTrader: (1)

The bitching about gas mileage would be endless. Even more so than now.

Mazda-Rati

Doesn't Speedsource have a 3-rotor renesis?

gh0st

if your using periphial ports, the ports would be on the rotor housings. thats basically a 20b. 119hp per rotor is achieved by side ports which is the part that makes a tri rotor dificult.

the multi side port renesis is:

intake:

End plate A-A (2 intake ports)
Rotor Housing A
Center plate A-B
Rotor Housing B
Front Plate B-B (2 intake ports)

exhaust:

End plate A
Rotor Housing A
Center plate A-B
Rotor Housing B
Front Plate B


Periphral exhaust ports would be:

End plate
Rotor Housing A
Center plate
Rotor Housing B
Front Plate

the second picture is the 6 port motor.
http://rotaryengineillustrated.com/r...sis09popup.jpg

it would be easier to make aquad rotor based off the renesis design

gh0st

they are running a 20b.

otakurx

There is nothing impossible about the 3-rotor, that is all rumor. Mazda just saw no reason before because of how the 2-rotor will respond to a turbo. A 3-rotor could be done easily with side ports and everything just like our motors. I think mazda execs wanted to use a more proven motor, the 13B with the RX-8 and they probably weren't looking to create the next super car. I mean the fact that we run a 1.3L with ~238hp is pretty impressive, remember the more power the more likely things will break and the more parts will cost. Maybe they will consider it for a new sports car line (as in 2-seater) but I think they will go turbo first.

Krankor

You raise the question as if it were a technical matter. It is primarily a political and marketing matter.

dynamho

... and would 9 miles per gallon be a reasonable figure?

zoom44

to the OP- we have SIDE ports not peripheral ports

Macius8

iTrader: (3)

[QUOTE=dynamho]... and would 9 miles per gallon be a reasonable figure?[/QUOTE

Gas mileage would be probably the same. Look at the guys in puerto rico running 20b's + turbo. They get over 15mpg's no problem or so i read in one of their threads. Unless you mesh on the gas all the time then its a whole different story.

phartknauker

yes... in fact I would brag about how bad it was....

RX8Maine

IIRC, the side ports and associated air channels on the front and rear housings are different than those in the center housing. If you were to buy a couple Renesis units and simply stack in another rotor, the center rotor would only be fed by center housings, one on each side, and its flow dynamics would be completely different that the two end rotors. That would reduce the engines efficiency and the internal stresses on the eccentric shaft would probably break it under load.

The only way around this without resorting to peripheral ports would be to design the end-housings and center-housings to have excactly the same flow design. This would require less flow through the end housings (not going to get 119HP/rotor anymore) OR more flow through the center housings, requiring them to be thicker (and therefore heavier), making the engine less compact.

I don't think it would be possible to shoehorn in a true multi-side-port 3-rotor engine that would fit in the chassis without significant alterations, maintain the cars weight balance, AND get the kind of output you are hypothesizing without forced induction.

skillmaker

I would like to thank all of you who have contributed to this thread so far.

I understand my terminology may have been off. I referred to it as a peripheral port motor, when the correct term might be a side-port multi-port motor?

Regardless, the reason for this thread existing is due to a saying I heard a long time ago: If you don't ask, then the answer is already 'no'.

I truly believe (without any significant research or irrefutable proof) that the engineering differences to go from a 2 rotor to a 3 rotor could be overcome fairly rapidly by a group of highly skilled automotive engineers such as are available at Mazda.

I also feel that the weight differences being discussed as affecting the balance of the car could also be overcome. I will grant that the engine would be longer (by the length of one rotor housing, one central housing, and the difference in size between the current central housing and a redesigned better flowing housing), and also somewhat heavier. I would also hazard a guess that if you add together the weight of a different manifold, turbo, waste gate, blowoff valve, intercooler, and additional parts and pieces, then the weight difference between a turbo RX8 and a three rotor RX8 would amount to under 100lbs.

As far as the strength of the tranny, driveline, etc... These are already being hyper-stressed by our FI brethren on a consistent basis, and for the most part seem to be up to the challenge.

Finally, as far as the MPG? Well, part of the reason our RXs get bad gas mileage is the stress we all like to put that little 2 rotor under. We squeeze the throttle hard a lot of the time because a) it's fun and b) it's what's needed to make the car go fast. With a 3 rotor, with more power, particularly down low, there would likely be less frequent full throttle runs needed, and possibly a little more even gas mileage figures. (Note - I am one of those few individuals who, with the exception of autocrossing, normally get near the EPA estimates for my RX. Driven like a truck, shifted below 3500rpm, gently. When I press hard, I expect and receive bad gas mileage. Ask your favorite Corvette driver what their REAL WORLD gas mileage is when they are having fun).


Carry on. Maybe someone from Mazda will see this thread, and listen and act on the need many of us have for more power.

m477

Or, in other words you could ask: why do the Corvette and S2000 get about the same fuel economy when the Vette has twice as many cylinders and nearly 3 times the displacement?

Another point here is that the 3-rotor wouldn't be able to rev as high due to the increased stress on a longer eccentric shaft. The JC Cosmo redlined at 7000rpm, so realistically I wouldn't expect anything more than 7500.

nycgps

iTrader: (1)

I think Emission is the biggest problem. Its always been a problem for Rotary Engine.

Plus they have to redesign the whole engine bay in order to make it balance.(and to fit the extra rotor housing and related stuff)

j_tso

For now I think Mazda needs another Phoenix Project like they did before the 1st RX-7, where they put their heads together to improve emissions and mileage by 40% in two years.

tmak26b

The gas mileage on the RX-8 is worse than the RX-7 isn't it?

3 rotors are nice, but Mazda would have a NIGHTMARE finding good mechanics to support it. Also it will come in a different car, you cant fit it in the RX-8 while maintaining the balance. Didn't Yamamoto said 3 rotors=more weight? They can squeeze the same power with a turbo, but they just have to figure out how to get the heat away. The heat is already bad enough on these cars stock, imagine with a turbo!

I dont know how they can fit a turbo into the RX-8 to give it a flat torque curve to 9K

skillmaker

Briefly -

Search these forums, and you will find that some people are already doing the engineering necessary to slide a three-rotor 20b into a streetable front subframe.

We were treated to three-rotor powered endurance racers at 24 hrs Daytona, that were actually tube-framed custom chassis, BUT it looked to me like they were able to solve both the placement and balance issues.

Mazsport is working currently on shoehorning a 20b into an RX8. Scott and his team should be justifiably proud when they accomplish this feat.

I do understand that a Renesis three-rotor would be different than a 20b three rotor. However, the power, durability, and concepts are all something that are well within the grasp of a large company like Mazda. We hear a lot of 'It would be hard', and 'That's nearly impossible', and 'You'd need to do this and that...'. Well, in concept it's very improbable that our rotary engines work at all. If no one at Mazda makes a decision to increase the HP and performance of our RX's, you can pretty much kiss the rotary goodbye. How many of you would want a 4 cylinder turbo RX8 (or would they call it an MX8)?

I am getting tired of people referring to our cars as Mazda's flagship product, when in fact all it gets is extremely minor cosmetic updates, while other cars in it's class get more and more HP. We are now out muscled by a compact hatchback (Mazdaspeed3), and a 4 door 4wd sedan (Mazdaspeed6).

Mazda - Please, give us a three rotor!

musclecarconvrt

I would love to have a 3 rotor.
It wouldn't be any more work for Mazda than any other Rotary. They just won't do it. It abolutely bows my mind that Mazda refuses to give their flagship sports car even equal power to it's 4 door sedans like the MS3 and MS6.

Sigma

You know, 20b swaps into RX-8s have been done quite a few times already. I think Acosta's is even shown on MazdaUSA.com

Vrimmick

Well if 3 rotors are so complicated wouldn't it be easier to go with bigger displacement? That would give us more torque and more power. Why do they stick with 1.3l - I am sure they could easily go 1.6 or 1.8 with a decent power increase - up to around 300hp (by mazda standards of course ;-)))