Donny Boy

I read on one of the posts referencing a magazine article that Mazda is considering/producing a 335 hp turbo version of the RX-8 slated for production soon after the release of the RX-8 we've all been waiting for.

I only hope Mazda does not go the way of forced induction, and opts for a 3 rotor engine or a 2 rotor engine with more displacement instead.

Forced induction engines tend to have a shorter life than normally aspirated ones. It's generally less stressful on an engine to have more displacement and more power, than to have less displacement, more power and more stress on the engine. Sure, another rotor would increase the weight of the car, but not by much, maybe 125 lbs only. Remember, the Renesis weighs 303 lbs today. Another rotor without accessories would not add much weight.

Furthermore, with the added torque, the 3 rotor would be able to rev less at 60 mph, thus offsetting the added displacement of the third rotor.

What do you think are Mazda's options, or do you like the turbo idea?
Any other engine/transmission ratio suggestions?

SPDFRK

Why not be optimistic and say a turbo three rotor and I will call it SNKEATR (Snake Eater).

Donny Boy

I got it, I got it. Or even a 4 rotor motor. Huh huh, are we there yet, are we there yet?

fritts

I am on the other hand of your arguement I hope they do go FI. I believe if Mazda gets the engine cooling in place you will see a much higher degree of reliability from the rotary. From what I have read, the 3rd gen ran way to hot which created coolant seal issues. Another thing, would be to stay away from the sequential turbo system. This system not only created to much heat, but also was way to complicated for what it was, how many vacuum lines did it have????... I believe mazda would have taken these issues into account, which is why we are seeing a NA version of the RX. A turbo would give a much larger increase in power, plus allow for upgradeability.

With a 3 rotor I think you will notice that the redline would be decreased significantly, along with it a significant amount of horsepower. Another problem with a three rotor would be the fuel efficiency and emission problems. I don't know how much higher they would be but I think they would be 150% higher at least.

Hercules

If it's a 3 rotor Renesis engine, then they would simply extend the rotor chamber and add another rotor. Fuel efficiency would decrease because of increased displacement, but not because of unburned hydrocarbons like in the previous rotaries.

Personally I like having an NA engine over a turbo. I don't intend to mod my car in any way, because it's going to be leased (get the RX-7 or the MPS RX-8 afterwards hehe).

I don't know why the redline would be decreased... but maybe you can fill me in on that one.

irresistibo

3 rotors, 300+ hp, crazy modding options. Sounds good to me, i prefer that to a turbo. More potential with a 3rd rotor. I could add a turbo later. Has anyone heard about room in the engine bay? I read somewhere on this post that the engine compartment is very tight, and there was little room for mods. That would suck.

fritts

With the 3rd rotor you will have that much more rotating mass in the engine. The engine will not rev as high nor will it be able to rev as fast as a 2 rotor. The only 3 rotors I have seen have been FI making me believe that 3 rotors is not that great of an option NA. We will not see a 20b 3 rotor in the renesis. How will they side port the engine with a 3rd rotor. Also mazda has said that this engine would be better suited for turbocharging due to the larger side ports than the 13b's were.

boowana

Rumors recently stated that Mazda may return to Le Mans next year. If this is true, we will might get a "look into the future" of what technologies are used and their applicability to production cars.
Remember, Mazda IS back into racing and as the only Japanese manufacturer to EVER win at Le mans, this would be an appropriate come back. :p

RedRotaryRocket

Speaking of LeMans and tying that into fritts' post, the LeMans winning 787B car was running an N/A 4-rotor....apparently multiple rotors and N/A works well enough.....

As for a 3-rotor renesis, you ask how they will make the side exhaust ports work with the 3rd rotor....I don't know, but I'd guess they'll do it the same way they make the side intake ports work on the current 3 rotor....

RX7 Guy

Fritts,

Perhaps I’m overlooking something but I can’t see where an additional rotor would adversely effect either. Not rev as high…Why not, there is still a side housing between each rotor so the sheering load imposed on the eccentric shaft isn’t increased. Not rev as fast…Why not, rotational mass has been increased 50% & the motivating force has been increased 50% so the net change is zero. What does increase is the torque load imposed on the eccentric shaft due to the additional length & power but that’s not the limiting load so it doesn’t come into play.

How about a three rotor with the rotor in the middle having twice the mass as the ones on the sides which are phased together for balance. Or, how about a massive displacement single rotor so that it could be air cooled. Or, how about a concentric two rotor. Or, how about a super high RPM rotor that draws air in through the center to produce a centrifugal compression effect.


:D Think about that for a moment...500cc's, 30,000 RPM's, 400 Hp. :D

m477

Um, I think that you got that the other way around... there would be WAY more modding options with a turbo than a 3-rotor NA.

Correct me if I'm wrong, but as far as I know, every single rotary-powered car running 12s or better is turbocharged.

RedRotaryRocket

m477,

I think the point irresistibo was trying to make was a comparison between a 2-rotor turbo and a 3-rotor n/a. If you start out with an n/a 3-rotor, you could always add a turbo as one of your modding options. In that case, you start out with the same amount of power, but your ultimate potential is greater.

m477

I suppose the potential is greater, but most aftermarket turbo kits for NA engines are very expensive and pretty rare compared to upgrades for stock turbo cars. For example, I'd rather pay $2k to be able to turn up the boost for those occasions when I really need it than pay $10k for some huge aftermarket turbo setup.

wakeech

i'd like to outline a few things, and throw my weight behind the 20B 3-rotor idea...

firstly, fritts, some of your concerns are valid, but you're overly pessimistic...
and RX-7 Guy, your reasoning is well meaning, but unfortuneatly not correct for the most part...

uh, well first thing...
it's not a big deal to design the ports for the third rotor... the middle rotor is simply flanked by two of the "middle" side housings in a two rotor... okay, that's probably not exactly true, they'd be a bit different (the front and back "middle" side housings), but not that different...

as for the lower redline thing, ya, it'd probably be lower, but not from the increase in rotatioal mass!!! think about this... when they dyno-test just the engine, they test it AT THE FLYWHEEL... what is the mass of your average road-car flywheel?? remember too, that you're only adding 8cm of eccentric shaft, and the rotor itself wieghs like what, >6 lbs in the RENESIS?? that's not going to be the limiting factor...
although shearing forces don't increase, tortional forces do, meaing you need a tougher eccentric shaft (it's longer too, don't forget that...)
Grimdawg, gimme some help here, oh enginnero...

looking at the increase in size, gimme one good reason why the length would increase more than 8cm... just one hypothetical one, 'cause i can't think of any, but there's probably something... if not, this thing won't take up nearly as much space as a turboed 2 rotor...
not to mention it'd be lighter... even with a slightly larger radiator, more coolant ( think about how many mL's more that would be... not many), more oil, heavier mounts, and other things i can't think of, would have a VERRY hard time tipping the scale in at 100 lbs, i'm sure... the weight increase would be so very very small... and ya, the power you could glean from such a motor would be in the 320-340 range, no problem... i'm sure if you pushed the envelope, you could hit like 360-370, but wouldn't impress with it's fuel consumption, or pass emissions...
i don't see why emissions on the 3 rotor would some how be worse than a 2 rotor... if it can pass, it can pass.

as for the "more upgradeable" thing, trust me, 3 rotor is the only way to go... ya, you'd be going FI, but who cares?? 150% of the displacement baby!! :D

RX7 Guy

Wakeech,

Are you confusing me with someone else. You indicate that “for the most part, I’m incorrect” but then go on to write a post that’s very nearly a verbatim restatement of mine:

I wrote:

You wrote:

I wrote:

You wrote:

Also, I’m a little confused by your estimates of the power & torque a three rotor will produce. Displacement is increased 50% over a two rotor so initially the 162 Lbs. of torque will increase to 243 & the 250 hp will increase to 375. But than the economy of scale effect will allow the accessories to operate a little more efficiently so an extra couple of percent should be added. The net output will be very nearly, 248 Lbs. of torque & 383 hp.

As always, I may have missed something. Perhaps you’re thinking that the center rotor won’t cool as efficiently so losses from a higher density altitude in the intake charge will occur or something like that.

Ultimately, I think we’re on the same sheet of paper but there’s a couple of smudges that need to be cleaned up.

Your pal,
Brett

max_stirling

First of all, all this dreaming about a 3 rotor is fun, but the truth is that Mazda has strongly denied any development of a 3 rotor RENESIS, where as a FI 2 rotor is definately in the works.

Personally, I like the idea of a NA 3 rotor, but I place that dream right next to my dream of winning the lottery. Now, regarding LeMans, I would love to see Mazda take the overall win again, but the current rumor is that Mazda will be racing in the GT or GTS class and not the LMP (prototype) class. With that, a Turbo 2 rotor would be completitive with the rest of the field if Mazda can squeeze out 500-600HP and be able to run it at WOT for 24hrs straight. Mazda will be racing with the likes of Porsche GT3s, Corvette C5Rs, and Viper GTRs.

If Mazda were to run in the LMP class again and shoot for an overall win, I think there's an option that no one has thought about. Instead of developing and manufacturing one off 4 rotor engines, I think they could much develop FI/NA 2 rotors that will run in parallel with some kind of gearbox that could mate the two engines together.

Eccentually this is what the W series engines from VW are, except for sharing a gearbox, they share a crank shaft.

Regarding the aftermarket, a FI 2 rotor would be a wiser choice. Turning up the boost on a factory FI engine is much easier than adding FI. With factory FI, the engine computer is designed to detect boost and adjust the fuel maps for it. With factory NA engines, the engine computer would essentually have to be overridden and no one expects a tuner to have the engine testing and development power of a manufacturer. The result is decreased relibility.

In addition, the internals of a NA engine needs to be upgraded to handle boost where FI engines are already strengthen for boost.

Just a thought

m477

Excellent post, but how do you know that there will be a FI RENESIS?

SPDFRK

Where is that coming from? That is what I hoped they were developing I prefer the GT classes because they are closer to real world cars and the utilizaton of technology is closer to production availability.

max_stirling

Actually, this comes from AutoWeek. The race tuner is ProDrive from the WRC fame. Also unknown is the type of engine to be used, though, I would assume, the RENESIS is the engine of choice since Mazda doesn't have a competitive V8 or flat 6 (Porsches).

rototlewski

The only engine mazda has ever used in le mans is their rotarys they have never entered a piston powered car in that race and i hope that they don't plan to.

well I don't see why there would be a problem putting side ports on a 3 rotor I think it would be easier because of the front intermidate housing is about the same size as a rotor housing. Thats because it has to hold the stationary gear for the middle rotor. Turbo would be exelent for this engine just for the sheer force of three rotors exhaust pulses happening close together.

The R26B 4 rotor had a 9000 rpm don't tell me that they can't make a multi rotor that has to have a lower redline. The 20B's red line was at 7500 for a reason, it was because there was no need to rev higher because the turbos started to lose efficancy at about 7000 and the power would drop off dramaticly.

You can get below 12's with a three rotor a guy running in the all-motor named jesus palddeia (or something like that) runs a N/A 20B PP with three porsche down-draft carbs makes like 400-450Hp he runs 10's consistantly and ran a high 9 once. its in a first gen. he has been so successful that the they are changing the rules to not allow 3 rotors in the all motor class, those bastards!!

I have been on a 3&4 rotor kick for the past year and have looked up alot about them.

also mazda used to use a engine called the 13G in racing for like 8-10 years. It was a P-port that made N/A 360-400Hp
Thats the same engine Racing beat uses in their bonneville car that went 242mph on the salt flats. That has 3 turbos on it and 930hp!

as you can tell i know alot about 3 rotors as i am putting a 20B in my corvair.

2300lbs+400Hp=Fasssst

Im gonna quit typing now since my fingers are getting tired.:o

rototlewski

I got some pics of the 13G











this is a 20B block with the intake manifold on it


20B


This is a 20B N/A that makes 450hp


These are 20B factiods
Potential power outputs:
*The standard power output of a 20B turbo is 280HP.
*With turbos removed (naturally aspirated), these engines produce 250hp stock, 320hp if ported.
*Apparently with the mere addition of a boost controller the power jumps to around 400HP.
*Rod Millen's Pike's Peak race car made about 500HP with a nearly stock engine.
*Japanese modifiers get about 700HP without too much trouble (I suspect this would be at a level where some engine porting and severe turbos would be required).
*Racing beat's Bonneville racer makes 900+ hp with a triple turbo peripheral port 13G
*The above figures were all mid-late 1990s. In 2002 some drag racers are claiming 1200hp.

wakeech

rotolewski!! cool stuff...

RX-7 Guy, i heartily apologize, i musta been on something then... i don't do drugs, but yes, i'm imagining things, sorry guy!! :o

hey max_sterling, i don't know all about prodrive's future plans, but i do know that they're running a Ferrari right now... are they just gonna switch in the future then, and run the Mazda cars?? OH!! would that then be like the Subaru factory-backed type of deal?? i'm pretty sure that Ferrari is giving prodrive very little in the way of help...

and you're sure (and by that i mean as sure as you can be) about the turbo 2 rotor?? oh well, at least it'll sound cooler...

max_stirling

I was just relaying what has been said on AutoWeek. In regards to your statement about ProDrive, they don't race cars, they build them. Usually, a manufacturer or racing team will contract ProDrive to perform some research and development for a racing effort and build chasis and/or other race parts for that racing effort. ProDrive is not a racing team. They are a hired gun and will work for anyone that has enough zeros on their corporate checks.

ilovepotatos

The last thing I want is a turbo model. Aren't you happy with a 2800 pound rocket that has 250 hp? The turbo would just take us a step backwards to the 3rd Gen RX-7. We'd have people crying over their appex seals all over again. Remember, one thing rotaries hate is heat. What do turbo's do? More compression. Stay away from it! I'll get off my rant box now.
*Gets Off*

Hercules

I agree so don't worry :D

I have always been a fan of naturally aspirated. If the engine can't make 300+ horses naturally, I don't want to try other means to get it to do that. I'd rather they increase the displacement than add a turbo.

This is why I love BMW because their tiny I6s produce some insane power.