robertdot

Because it gives it more power. If you don't want any more power than what a NA engine can provide, you don't need forced induction. You just have to decide how much power you want vs. how much longevity you are willing to give up. Not that I think there is any scientific formula you could apply across the board, but simply more boost = less longevity. If you get a car and keep it 5 years then sell it / throw it away, boost it as much as you want without blowing up the engine, and have fun. If you want to keep it 20 or 30 years, you want to boost it not very much / not at all, and / or beef up the internals enough to handle the additional stress.

DOMINION

I hope you **** leard something from this.

zoom44

i learned that a few people hadn't seen kari's pic before

also mazda has said on more than one occasion that the renesis is built to take boost, so you will see a factory boostd renesis "at some point". the talk right now is electric assissted turdo for 2006

DOMINION

Yea like me.

mikeb

mazda doesn't even know what type of oil the rx8 needs

cortc

If the RX8 gets factory FI it will more than likely be a supercharger, the Renesis is a better candidate for it and it is easier to engineer (Packaging it in the 8 is a lot easier and less heat issues)... There is also talk about a RX7 replacement with a 1.5 liter Renesis (wider rotors) or 3 rotors (That’s right a regular production 3 rotor engine!); only time will tell... I have good sources, but until then even reliable rumors are just that...

One thing for sure, it will be a lot of fun…

robertdot

HAHAHAHAHAHA.

I'll buy into a SC or Turbo RX-8 from Mazda. That seems pretty likely considering all the love for the RX-7's turbo system and the desire to push the RX-8 to the next level.

I'm not sure I buy the 3 rotor RX7. I know there are 3+ rotor cars floating around the world, but it seems, at least, quite a ways off. As I'm sure many have heard, something would have to happen with the side port on the Renesis for the center rotor. They could move back to the older way for the center rotor, but it seems some inefficiencies would develop w/ the center vs the outer rotors.

I'd bet on a 1.5 liter Renesis. They've still got so much they can do with it before they need to ditch it for a "20B" Renesis. I wouldn't even doubt a turbo or SC 1.5 liter...

fxdsconv2000

A thiner middle rotor that would not exceed the volume for the intake and exhaust is possible.

rotarygod

Once again I need to write a small book as a reply! Here goes...

First off, to address the initial observation, what is your proof? Do you know the designers personally? Are you one of the designers? If the answer is no to any of these, you don't know for sure and are therefore speculating based on what you believe to make sense. Let's go over some historical facts about Mazda's trends and the rotary engine. I'll start with the 1st generation RX-7 and work forward from there.

1978: the 1st generation RX-7 emerges as a 1979 model. It is powered by a 95 hp 12A engine. In 1981 emissions changes which resulted in using a catalytic converter rather than a thermal reactor helped bring horsepower up to 110. I'll bet they didn't see that one coming 2 years earlier. In 1984 the GSL-SE was offered to certain markets. They increased the engine size to a 13B and horsepower jumped up to 135. In Japan they retained the 12A but added a turbo which resulted in nearly the same power as the nonturbo 13B versions.

1986: The 1st year of the 2nd generation RX-7. It was available only with a 146 hp naturally aspirated 6 port 13B. 1987: The Turbo II hit the market with 170 hp. In 1989 each model was revamped. The nonturbo went up to 160 hp and the Turbo II went up to 200 hp. The Japanese market received a special limited edition version of the Turbo II known as the Enfini IV. It had 215 hp.

1993: The 3rd generation RX-7 emerges. Mazda designed this car as a no holds barred sports car. They had performance goals in mind that could not be accomplished without some redesigning of the 13B. Their goal of 250 hp (but attained 255) could only be achieved through turbocharging. You and I know this isn't only true but to hit their margin of safety and emissions regulations, at the time it was true. Mazda took many shortcuts on this car. They installed 2 very small turbos to help response time. The biggest issue was that they spin so fast and get so hot, they aren't reliable. Another issue Mazda had was the internal coolant seals. They changed the material they were made from and reliability here went down. To compound cooling issues, the radiator was pathetically small and the engine bay was so cramped that air could not flow well through it. All of these factors combined with a sticker price approaching almost $40K by 1995 caused it's demise in this country. Mazda continued to develop and improve this car until the 21st century when it finally had 285 horsepower.

Enter the RX-8. A car that is designed to be a COMPROMISE car for the person who wants the feel and performance of a sportscar with the drivability and functionality of a sedan. Mazda had horsepower goals that up until the Renesis could not be met without the aid of forced induction. Mazda knows the engine has far less average horsepower without turbos, but they didn't have neck snapping power in mind when they designed this car. They wanted a smooth linear deliver of power and that is what this car has. They had performance goals in mind and they hit them with the current setup. So this begs me to ask these questions.

If Mazda hit their projected performance numbers without forced induction, why would they need a turbo? A turbo adds complication, it is something else to go wrong, and it is more expensive to manufacture. Now before you think I am agreeing with the original poster, I have another question.

Looking back at the history of the RX-7, why is there any doubt that a more powerful version will not appear? A more powerful version of every generation RX-7 has always appeared. Look at the first years of each model. Now look at the only year RX-8 we have available. See a correlation? I do. They each only have 1 power level available for that year. Coincedence? I think not. In 1979 did anyone except Mazda know for sure that there would be a turbo version or at least a larger engine version available later? I doubt it. In fact I'll bet that year, Mazda didn't even know it. Every RX-7 that ever came without a turbo, had an upgraded version availble at some point in it's lifespan. It's really quite simple. Manufacturers test the waters with a lower, cheaper model. They judge potential sales by this. If the car does well in it's current trim, they'll offer an upgraded model. If sales are low, why spend more money on a higher level of car that won't sell? Just because you add power to a car doesn't mean that sales will just miraculously go up. They will in this car, but they weren't even sure if it would sell at all yet alone so good.

You can almost bank on the fact that a more powerful version is on it's way. This leaves us with the debate over how will they increase power? Some say larger displacement. I say no to this only because of current gas prices and the cars current gas mileage. This will definitely hurt economy on a full time basis. Others say turbocharging. This may happen. The biggest current issue is with emissions regulations. A turbo absorbs some heat from the exhaust system. This means that the cat will be slower to get up to temperature. The WRX actually has a cat before the turbo. That solves the issue of cat temperature but creates the potential for drivability issues. Having driven a WRX however, I can tell you it isn't bad at all. The rotary exhaust is extremely hot. Placing a cat this close to the engine will almost certainly result in short cat life. I think with the advent of electric assist spooling turbos which Mazda has shown, they can solve some issues about cat location and turbo spool times. Only time will tell but I think a turbo still has a chance of appearing on this car. The last group think supercharging will appear. I favor this group although I can't discount the viability of a turbo. A supercharger won't create all of the emissions issues that a turbo will. A supercharger also isn't an exhaust restriction. When a turbo isn't under boost, it still hurts power but restricting flow. Consequently when today's supercharger isn't under boost, it has a bypass valve that opens to maintain efficency and mileage. The blower itself actually only takes about 1/3 of a horsepower to turn when not under boost. Air still flows through the rotors of the supercharger. If you disconnected the belt, it would still spin from airflow. That isn't much parasitic loss. These features still allow you to retain economy, emissions, and get added power. It offers the least compromise of every system.

Of course someone is going to say that the Renesis has too high of a comprssion ratio so it won't work good. Once again lets look at history. When the turbo 12A came out in the 1st gen RX-7, Mazda installed lower compression rotors. When the Turbo II 2nd generation RX-7 came out, they installed lower compression rotors. The 3rd generation RX-7 retained the lower compression from the 89-91 Turbo II's. Why wouldn't they do the same here? They always have! My logic is to keep the current compression ratio but run less boost. Anyone who has sat through hours of my other posts knows the difference between static and effective compression ratio and how the static compression ratio (10.0:1) isn't what determines power.

In summary what you just spent the last half hour of your life reading is simply this, they probably will offer a higher power version of the RX-8 one day and if it has forced induction, they will probably install lower compression ratio rotors. They always have. Why break from tradition? Simple, isn't it?

rx8 dx

Rotarygod you are right. Mazda is not going to FI the current version of the Renesis,at least for now.

Two plan strategy for Mazda and the incorporation of FI to the renesis:

Plan A: They are aware of all the FI aftermarket in development and plan to "watch and wait" to see how the current version of the engine takes it. That way they are not investing in any testing or spending money in repairs and want us to be the guinea pigs.

Plan B: If plan A doesn't work, then they will modify the original version of the renesis with one that will be able to handle the failure points that the first engine revealed when it was FIed.

bureau13

rx8 dx, I think you're putting words in rotarygod's mouth. Who says Mazda isn't investing anything in testing FI on the Renesis? Also, I would hardly call using lower compression rotors on a near-future FI Renesis a major redesign, nor does such a choice indicate that they tried and failed to do it the other way. As rotarygod said, Mazda has always gone with lower compression rotors when they added a turbo, but there are other ways to do it (i.e. run less boost).

jds

Rotarian_SC

I agree with you jds, if Mazda wanted to watch and wait then they would want to see FI projects being done and would help those companies crack the ECU.

BaronVonBigmeat

Instead of bigger/wider rotors, or adding FI...how feasible would it be to go with option C, higher RPM's? What is the limiting factor for the Renesis, or rotaries in general? Something about "10,000 RPMs" just sounds nice.

EstonRX

No reason the Renesis can't be taken up to 12,000 rpms for that matter. The RX-8 would need some drive-train modification to have much life at those RPM's, but the engine would be fine. Emissions, however, well, good luck! Say by the the cat and have fun offroad/track only!

If I were a betting man, I would put money down that Mazda's first factory FI RX-8 will be using the 10:1 ratio that it uses now. Sure, historically they've always dropped the ratio (in my opinion just to make life easier tuning) but with this fancy-shmancy new engine that has won all kinds of awards I think they'll keep it as is and run the boost in the 5-7psi range.

As far as all the talk concerning the RX-8 drive train or the Renesis in particular not being able to handle FI, I have to agree with a few of the posters above and say it's purely a tuning issue. I don't see any single weaker link in the picture compared to older engines, and many parts are stronger than before. The higher compression ratio means less boost unless you want to build a bomb, but the key is solid a/f and timing under all situations. The piggy back guys will get there no doubt.

kimba2

wouldn't more RPM = more emission, hotter engine, decrease power plant life.

Japan8

Actually I just got done watching a video that came with one of my mags on the development of the RX-8. I has a section where Kenichi Yamamoto dubbed ""Mr. Rotary" takes a prototype out on the track at Miyoshi. He is the Department Manager for the rotary engine development at Mazda. He pretty much says that the Renesis provides what he considers to be the rotary feel... smooth linear power.

As for rotarygod's analysis. It's very good... but it doesn't address one issue. This is an RX-8 not an RX-7. Does Mazda plan to offer both a high powered RX-8 and a simliarly powers RX-7? Isn't there a sales problem with that picture?

DOMINION

Cant. Rotaries dont have the tourq like a piston Engine.

DOMINION

rotarygod, It would take me a 2 days to write that.

rotarygod

Actually the initial point of it was that no one but Mazda engineers know for sure. Since the car is a compromise and not a true pure bred sports car, adding power wouldn't necessarily put it in that realm. It would just be higher powered. I believe there is still room for a true 2 seater sports car. Will there ever be a higher powered version of the RX-8? Almost certainly. This doesn't mean that it will have forced induction. When I say higher power, I'm not necessarily saying 75 or 100 more horsepower. It may be only 15 horsepower from better tuning but it's still more power. This is what I find plausible.

David_M

Something else to take into consideration is that Mazda has publicly stated they intend to produce a Mazdaspeed version of all their cars. While this isn't a guarentee of a turbo RX or even a more powerful NA car, more power certainly seems to be part of the Mazdaspeed formula.

Just as an aside on turbocharging the Renesis. With a 10.0-1 static compression ratio low boost is the only option, but who declared low boost a problem. If all you want to do is add a few pounds of boost, say 4-6 pounds for the sake of arguement, then you will only need a small turbo. which means that you can acheive a very fast spool time to max boost. Using a small turbo is probably the best way to go if your going to put one on a RX-8. A small turbo can be made to spool so quickly that it will be practically invisible in terms of the driving experience. The downside is that the familiar feel of boost kicking in won't be there because you'll be at full boost so shortly after idle.

I should add that when I say small I mean small. A turbo that would be too small to make big numbers on the dyno. Dyno numbers are good for tuning or bragging but if you just want enough power to make a RX-8 run with the big dogs 65-75 hp should do it. To put those numbers in perspective, assuming the factory claims are true, you would end up with 303-313 hp total and run mid to high 13's in the 1/4 mile.

RenesisX-8

iTrader: (1)

I bet the 8 will never see a turbo because it will consume too much gas. I mean 10 city-15 hwy...how would that look on the sticker of a four door?

I think they are going to do minor tweaks to the N/A renesis over the next few years....intake tuning+exhaust tuning+compression tweak+ecu tuning+upped redline or displacement. Anyone of those seem feasable. They may gain 10-30 h.p. after some more tweaks to the current set up.

I think the turbo will be used for the future RX-7 possibly, or not at all. They may even use hybrid electric for torque and up the rev's for horsepower. That would bring the fuel efficiency back. Of couse, they would need lighter weight battery technology i'm sure. Or, they may do more displacement or three rotors,.....BUT that won't be fuel efficient either. I think new technology will take the rotary even further and the Renesis is just a fresh starting point.

rotarygod

Those numbers are pure fiction. That would ONLY be true if you floored it everywhere you go. Just because a car has a turbo doesn't mean it is spooled up and providing boost. Most of the time it is just free spinning inline with the moving air. No extra air, no extra fuel needed. With regular driving you'll probably see no less than a mile per gallon drop in gas mileage. People only see worse mileage because the car is so fun it is hard to keep your foot off the gas.

T-von

Yep.... My Fd with over 80k original milles gets the advertised 17 city & 25 hwy. Like RG said, it all depends on how you drive.

SSR Engineering

Well a turbo charged rotary isn't exactly the most emission friendly car in the world, getting it to pass CARB inspection would a project all in its own. Mazda didn't turbocharge the vehicle for plenty of reasons and reliability was probably on the list but not before budget and emissions. Having a basis for a naturally aspirated car, that would mean in order to turbocharge the RX-8 they would have to go all the way back to the drawing board, design a whole new engine and go from there.

rx8 dx

So Mazda need to go back to the drawing board and build the "Renesis II" engine with the FI package that includes a new ECU/Tuning, because a lot of cars for 05 and 06 (Nissan,Acura, even Honda)will have so much HP that RX8 owners(Including me) will not be happy with the old stated 238hp.