The title just about says it all. I spent hours recently reading about how all these various engines worked, because I still didn't understand why the rotary was so bad on gas. Then I found some site that explained it very well. Its all about compression, a rotary has less compression, and its not adjustable, where as you can swap parts in a piston engine and add much much more. Thats why its less efficient, less compression. Perfect job for a turbo. Would a turbo therefore, not only add more power, but also increase gas mileage (ignoring the fact that if your 8 had a turbo, you'd whale on it much more)?

The RX7 had a turbo. How come the RX8 doesn't? And are there reasons why it never will? I'm no mechanic for sure, but it seems like adding a turbo is a relatively minor addition to the car, from a technical point of view. Maybe I'm just missing something. Or maybe Mazda is torturing us on purpose to help give the RX8 more mystique and help give Mazda a better image.

 

Well some argue that the turbo would improve mpg, but in reality you're more likely to stomp on it more often and get poor mpg in turn.

 

Compared to other cars, the RX8 rotary doesn't have a compression problem.

Yes you can change this compression ratio. For the RX7 there were low compression rotors made which lowered the compression to make the turbo more effective, there might be some coming out for the RX8. I have no news of anyone progressing on this however.

That site you read sounds pretty off.

http://auto.howstuffworks.com/rotary-engine.htm

The problem with the fuel consumption, is inherant to the design of the rotary engine. The single long chamber used for combustion does not lend itself easily to efficient full igniton of all the gas in the chamber. In general, the bigger the combustion chamber, the more gas is required to cause an explosion of sufficient power to do work.

If you tried to compress the engine a lot more, then you would experience detonation, where the gas mixture is superheated by getting compressed and self ignites in the wrong part of the power stroke, causing the engine to seize.

Its a pretty fine line of trying to stave off detonation and yet cram as much air in as possible(turbos/superchargers) to produce powerful strokes.

Turbos increase any engine's efficiency, because you are getting much more than just the 1.3L or whatever base amount of air, all crammed into the engine.

It would be the same basic principle as this:

You use a black powder rifle. The instructions say to cram a speficied amount of powder in to fire the slug. You could add more in, and it would make the bullet go faster and farther. But you also put a greater than recommended amount of stress on the barrel.

It makes the rifle shoot farther, but it has nothing to do with the design of the rifle, it just has to do with how much freaking powder you crammed in there.

The RX8 doesn't have a turbo because mazda tried to increase the efficiency of just the rotary engine and not use a turbo as a crutch to beef up efficiency ratings.

Besides, any turbo on any car is going to put more stress on a engine than natural aspiration. The RX7 was a very finicky car that had a rigorous maintenance schedule. By going the natural aspiration route with the RX8 you generally make maintenace costs lower and reiability skyrocket.

Sure making pipes and bolting stuff on is not hard, anyone with the right tools could do it. The hard part of adding a turbo on anything is that you have to change the whole igniton software to make sure it doesn't blow itself up. Which is the stumbling block that everyone is trying to overcome at this moment.

 

after the disaster with the 3rd gen i dont think we will ever see a turbo on a rotary again from the factory.

 

I think its going be made.. maybe in 2-3 years..

 

one word: supercharger :p

 

I think it would make more sense for Mazda to produce a three-rotor engine than it would to produce a turbo, even if that meant reducing the displacement of each chamber. Sure it would be more expensive to design and produce, but in the long run, it would be much more reliable.
There are several three-rotors out there, aren't there?


BTW, do you guys ever sleep????? :p

 

my thoughts exactly.

 

AMEN! I think Mazda should forget Turbo's or SC's and simply go to a 3-rotor engine. I would like it to stay 1.3L but maybe to make it more fuel effecient go with a 1L that makes 320HP and I predict that RX8 sales will increase big time.

It performs pretty dang good with only 238HP (or 225 like so many claim) so increaseing it by about 80+HP would do wonders for performance.

I think Mazda knows the 8 needs more power...I just hope (while I realize it probably wont happen) they go with a 3-rotor engine.

 

I was told by a mazda rep that there would be no factory turbo made. He stated that it all amounted to the BTUs (heat) made by the enging. Adding a turbo would increase the BTUs and shorten the life of the engine. It's all about warranty, the life expectancy of the engine would be short lived, and this would hurt their image.
I also asked about the 20B (three rotor), and was told they are not durable due to a coupling in the crank shaft that is prone to break. He stated that it's like putting a regular two rotor enging and adding the third rotor. the weak link is between the second and third rotor.

 

My initial thought is no, and that’s because of the RX-7’s issues, but if Mazda can work out a reliable version I think they may give it a shot. However, that being said I would venture to guess it would be a very conservatively tuned version, and due to the likelihood that the boosted version would be expensive, you might be better off going aftermarket.

Another factor that is going to play into this is the sales of the RX-8, which have been slow as of late. The slow sales might force their hand, but at the same time might cause them to scrap the 8 all together. Ultimately this decision will come down to economics, and that’s something that is very difficult to predict.

 

20B's for all my friends

 

^and 14mpg for everyone too :D

 

I think its mainly a cost issue. because cost would skyrocket with addition of factory turbo, a plethora of other things needs to be altered to accomodate a turbo and push the price of the car into $40k range. At that price range only a small percentage of RX-8 sold will be turboed models. So its probably not worth it to develope it just for a niche market amongst what is already a niche market. expensive price is what killed the Supra, 300Z, 3000GT and RX-7 in the 90s. The idea of a turbo/super charged RX-8 may sound nice in the mind of an auto enthusiast, but it dosnt make business sense for a company looking to make profit. A sub 30k price is what makes 350z and rx8 successful.

 

I prefer 38D's myself.

1.3L :D

 

It can be done...they just are unwilling to do it right now I guess. Mazda telling us no to Turbo/SC's make sense based on what we all have talked about but something should be done.

So far the aftermarket for the 8 has shown you can get about 20-30HP out of this NA engine (without turbo/sc) but I wonder if Mazda can't do better?

I hope they figure something out because the 8 is too good of a car to let it die. If it does...this might be the last rotary car ever made. If the Turbo option proved problematic and they are making excuses regarding a 3-rotor....where are you going to get the extra power from?

The Turbonator? LOL

Frankly, there seems (and I'm a rotary newbie so this might be just fluff) that probably 50HP is the limit in gaining power in the Renesis naturally. This might even be a stretch but I’m hopeful more tricks will come up helping us gain NA HP.

I just love this car so much I hope Mazda does not give up on it.

 

:D is right

How about this engine for the next RX8?

Honestly though, the Renesis will never have forced induction from the factory. Even the secret supercharged RX8 that Racing Beat built with MNAO was only a glimmer of hope of the Mazdaspeed RX8 for the US that we all want.

I think the best path for this car, is to eliminate the all the crap on it that restricts air flow, tune the engine for all the power it can generate under the curve, upgrade all the suspension components, and sell to us. The JDM Mazdaspeed II RX8 is a real sweet car over there, too bad that it was a limited production vehicle.

 

What is that sweet sweet engine?

Nemesis...what are those things that restricts air flow? Header, Cat, Muffler...is that what you mean? How could they get rid of that stuff?

In the engine picture above if those pipes could be directed right into the front fender (with some type of small CAT per pipe) that would look sooooo cool. Probably ear hurting...but sweet either way.

 

Yes, all the mods we are putting on the car for air flow: Intake, Headers, Midpipe, and Catbacks. Then tune the engine for a broad power curve from the factory. The only drawback to this, would be the aftermarket guys would be pissed!

So, just gives us a quality CAT that can take the heat of a properly tuned Renesis and I will be happy.

 

That's the custom 26B that Scoot Tunning builds in Japan.

 

http://www.b-kmotorsports.com/

B K Motorsports is developing a 3 rotor in conjunction with Mazda. I remember when the Renesis first came out, some people were saying no way could anyone make a 3 rotor because of the side ports.

Couldn't find any pics or drawing of the engine. just this quote from a press release:

"The engine is based on the RENESIS rotary engine as supplied in Mazda’s flagship sportscar, the RX-8. It is designated 20B, a three-rotor design incorporating electronic fuel injection with a full data-gathering system. And, like its street-going two-rotor sibling in the RX-8, the engine revs to over 9,000rpm – this being one of the hallmarks of the rotary engine. While still undergoing final tuning, Mazda and SpeedSource are targeting output in excess of 400 hp, making it competitive with other engines in the class."

I doubt this will ever find it's way into a production car. But once the engine has been fully developed, I wonder if it would be available for racers and enthusiasts with deep pockets?

 

^^^ 4 rotors?!?! wat in the ?!

please say im wrong? would that even fit in a (im assuming) rx7?

neways... turbo from factory? 1 to 12 shot supercharger from factory 1 to 4 shot

 

Yep, Scoot makes 4 rotors and they have put them into FDs. I think the next best known 4 rotor builder is Downing of Atlanta. Petit Racing makes 3 rotors and will put them into your FD as well...

Only problem I would see with a 3 rotor or larger is the length of the block. I think Mazda stuck with 2 rotors because it would allow them to centralize weight better and plus I doubt they wanted to develop on the 20B (in money terms).

FS

 

it is not a side port engine it is a regular 20b. they are just using Renesis for marketing.

 

Mr. Downing is going to be at 7stock!!