Spoonie

Not to start a war, but I don't think so. The RX-8 appears to have the same power characteristics as a Honda S2000. For anyone who has not driven an S2000, the car feels about as fast as an accord up until about 5,500 RPM, then all hell breaks loose. I'm sorry but I need power in the middle and low rev ranges. I'm not looking for Dodge-Viper torque, but if the only way to get decent power out of the RX-8 is to redline the motor, then the Standard RX-8 is not for me. I'll wait for the turbo. The Standard RX-8's power plant does not seem to be flexible. I don’t care if the rotary engine is super smooth. Redlining a car all the time increases Engine wear.

I'm a bit disappointed by what I’ve read so far in regards to the RX-8. I doubt that the car will be able to outperform a BMW 330i or the G35. Not to mention that the 330i gets better fuel mileage. Any idea when the Turbo will be out? Looks like I’ll be keeping my 330I, The RX-8 does not seem to offer anything more that isn’t out there already. In fact the RX-8 seems to offer less. I guess I was expecting too much.

pelucidor

There are many who can give eloquent answers to your questions. Then there's me.

1. The RX-8's torque curve is different from the S2000 - 90% torque from 3000rpm onwards if I remember right. Also Honda offers an optional 100k mile engine warranty, so perhaps redlining a car to 9000rpm is not too detrimental. I am sure the same would apply to the RX-8.
2. I have test-driven an S2000 several times - I think it feels like an Integra (not a slow car, low weight) rather than an Accord below 6000rpm due to it's weight. And of course the other 3000 rpm provides plenty of excitement. I think the Rx-8 will feel slightly more 'powerful' than the S2000 from a much lower rev range.

3. I've also driven a BMW 330i many times. Good but (IMO) overpriced car. I doubt the fuel economy will be much better in an aggressively driven 330i - perhaps 2 or 3 mpg. You already have a good vehicle, so I can understand why you might feel the RX-8 is not a huge improvement over the 330i in many (if any) areas.

4. I almost bought an automatic G35 Sedan. I might still get the G35 when the 6MT comes out. The power/weight ratio of the G35 to the RX-8 suggests that the RX-8 should be quicker in all areas (but probably not by much), and it should definitely be more nimble. The G35 always feels big (both good and bad).

5. I think the RX-8 offers a lot that isn't out there already. Let's start with the rotary engine. Then the design concept of a 4-door coupe with swing doors. The the light weight, the low price etc and I think it is unique. But not for everyone.

Hercules

According to these reviews, the RX-8 will beat the 330 on the dash to 60 and the quarter. Mind you, these are preproduction reviews and numbers could change, or improve if C&D gets their hands on the car.

90% of torque is available from 3250 RPMs.

Obviously, you don't know rotaries. Redlining rotaries is not bad for the engine, not like it is for a piston engine. It doesn't increase wear nearly as much, and if you read the RX-7 forums, and any rotary enthusiast will tell you they love the sound of the warning buzzer because it's a frequent sound that's heard while driving.

As per beating the 330 or G35.. time will tell. I have faith in this car because of Mazda's past reputation, and the near 4 years they've put into this car's development. The engineers that worked on this car worked a lot on THEIR OWN TIME, which says a lot for the enthusiasm they have. The RX-8 might not even beat the 330 or G35 as per power, but I think handling is where it will excel. As time draws near, hopefully after launch in January... we'll know for sure.

And if it's not all it's cracked up to be, I'll probably be buying a 330 or a used E36 M3

Macabre

why is that? I would think that, just like in a piston engine, as RPMs increase the forces excerted on the crankshaft or eccentric shaft in this case would increase. I've also read that the wear on the stationary gears increases a great deal as RPMs increase. I also know that the rotary lemans car had a lower rev limit for the endurance race than for qualifying, presumably for reliability. Am I missing something?

Toadman

*evil grin* Someone do the honors.... Be nice, Herc... :D

Hercules

I'm being nice! :D

MyT13B

The stationary gears have been proven strong enough to 10,000 rpm. That is if they are properly hardened which I suppose is a standard feature. In the past, hardened stationary gears were sold to racing applications.

Much of the racing technology of past years has found its way into the production versions.

A standard rule of thumb has been if your rotary sees over 10K rpm then you might be wise to do an inspection teardown.

By making the rotor 14% lighter, that limit may conservatively be 11K rpm as the disaster limit. I would NOT recommend anyone try it since it would be about $5000 US to replace a blown engine! And hopefully there is a rev limiter to prevent that much rpm.

You should get a solid rush of power from 2500 rpm on up that takes the RX8 with authority even in high gear. 1st gear may even have a tendency to chirp or even squeal the tires when you plant your foot to the floor. No need to feather or dump the clutch either.

Rich

Given two facts, I can't see how you come to your conclusion.

1. In a given gear, acceleration is directly proportional to the amount of torque the engine produces. In other words, if an engine makes X units of torque at its torque peak, it will give you 90% of that push in the back where it makes 90% of the torque. Therefore, to determine if the car will "feel fast" in a given rev range, you need to look at what percentage of the maximum torque is available at that point. If 80% is available at a given point, it will be 80% as "fast" at that point.
2. The RX-8 is supposed to have 90% of its torque available around 3250. Coupled with the first fact, it's clear that the car will accelerate at basically the same rate (within 10%) anywhere from 3250 to redline. In other words, it will not feel peaky like an S2000.


Now, of course if you downshift it will feel (and be) much faster because you will increase the torque at the wheels due to the gearing advantage a lower gear gives you.

Of course, if you don't like redlining a car, the RX-8 probably isn't for you. To me that's most of the fun. As long as you keep a car well maintained, driving in the upper rev range shouldn't harm the engine. My Miata lives at 4k and up. That's where the fun is. :D

Hercules

The road and track article from Sam Mitani says:

So there's your chirpin for yah

R.Cade

If 90% of the power is available at 3500 then you should be able to drive it like grandma just fine.. but I can't can't imagine owning a sports car, with 9k+ redline, and NOT reving it!

Hearing the warning buzzer in a 3rd gen rx-7 is as good as prozac

Hercules

Amen :D

Macabre

I understand that the renesis has a high failure RPM threshold, but I still don't understand the comment that "Redlining rotaries is not bad for the engine, not like it is for a piston engine. It doesn't increase wear nearly as much" since everything I have read indicates that, just like a reciprocating piston engine, wear increases as RPM goes up. I'm not disagreeing with it per say, just asking that if it's valid, someone explain why the available information is in conflict. Frankly it smells a teensy bit like rotary propoganda. :D

Anyways, based on the torque graph that has floated around, the engine will be far less peaky than an S2000. If it's geared right, it should pull fairly well in the low to mid range.

Hercules

Read the other post I made about the "autoexpress" stuff.. the third article I posted mentions the midrange performance

Buger

To quote myself:

"The s2000 has a range of approx 2750 rpm (5750 - 8500) of 90% peak torque or greater. The vtec's first peak in the torque curve does not hit the 90% mark and the torque actually drops before slowly rising again at 4500 rpm again. This is why the s2000 has had a reputation of being "peaky".

Actually, the most amazing thing about what we have seen come out about the renesis is that it will have "90 percent of peak torque available at 3250 rpm". Assuming that the torque curve doesn't [drastically] go up and down like the vtec s2000 one, this would mean that there will be 5500 rpms of 90% or greater torque in the Rx-8's powerband!!!! "

Brian

Odessa

I'm kinda new on this...but, doesn't it have something to do with the fact that pistons have to accelerate, come to a complete stop and reverse direction and accelerate in the opposite direction. Where as a rotor moves in a continuos single direction. Seems very elegant to me, in contrast to a pistons vigorous movements. I don't know though I'm just recently interested in the rotary. But starting friction is much greater than continuous friction.

Buger

Found an old jpg that I previously posted. See attachment

Brian

Hercules

If the rotary was given more engineering time, more press and praise, and more money for development...

you would never see piston engines again At least Mazda is carrying on the work that needs to be done by everybody to make faster, lighter cars

DYT

Here is how I understand it. I'm not a rotary expert, so anybody feel free to correct me....

On the rotary engine, the main stress is from the twisting of the eccentric shaft. Obviously at higher the rpm, the more stress it is subject to.

On the piston engine, in addition to this same type of stress on the crankshaft, the up and down motion of the pistons create vibration and stresses on the pistons, rods, crankshaft, etc, getting worse as the rpm goes up.

Sputnik

That's exactly why high revs are harder on a piston engine than a rotary engine. And it's not only the pistons/connecting rods, but the valves, valve springs, and in some engines, the pushrods and valve lifters. And in addition to the normal friction wear, the crankshaft has to deal with the stresses of controlling the pistons when they stop/accelerate/stop/accelerate.

That doesn't mean that a rotary engine can spin as fast as it wants to, or that a piston engine will fall apart prematurely if you rev it up on a regular basis (w/o running into the redline), but in general, the rotary engine handles revs better.

---jps

Hercules

Now after insane engineering, BMW managed to make an engine that puts out 18,000RPMs! Imagine what a properly engineered rotary could do.. *drool*

Macabre

You're assuming that the theoretical limit for a rotary is higher than that of a piston engine? One of the benefits of a piston engine is that the movement of the pistons can be varied easily by the engine designer. The pistons in F1 engines barely go up and down at all, they have incredibly short strokes, to minimize the force applied to the crankshaft and also to lower the center of gravity. Something you can't really alter on a rotary. I suppose you could use small but very wide rotors, though you'd probably need a couple dozen spark plugs to get decent combustion :P. You still have to design a gear that can withstand those thousands of pounds of force. Then to have the rotary running at higher RPMs than the best piston engine to compensate for the relative inefficiencies. Of course, if you had said 30 years ago that you could have a piston engine running at 18k rpms making over 200hp/liter, you'd probably have been laughed out of the industry.

wakeech

yup exactly... just remember though, a rotary of the same displacement needs only rev half as high to get equalish output...

but ya, it's very difficult to change the "bore/stroke" ratio on the rotor, but that's exaclty how you'd do it...
and those challenges don't seem too high, to tell you the truth...

think of the energy in those super short stroke F1 engines: enough reciprocating energy to throw them into ORBIT (not kidding!!) at full song... then, think of the tolerances these components must KEEP while running 19K rpm, think of how much the con rod stretches and compresses through one stroke... THEN think of the voltage these bloody things need... and how to actuate the valves UP (down is a peice of cake) that fast without bouncing or shattering them... think of the hundreds of dinky little things, like wrist pins, or the caps for the crank, or uhhhh... the list goes on and on...

hardening the gear?? just a matter of meturlagy... if the FIA allowed the rotar (being "non-reciprocating" and everything, which is baloney) to be run, and millions were spent as a constructor like Sauber (with all their Malaysian backing... like Petronas and stuff) with big intrests in the Far East decided to do a factory operation with Mazda, and millions and millions were spent designing a rotary engine that'll run about 300km (well, soon to be about 1000km due to the new regs) before blowin' up, and my friend, i'm sure you'd see that it can be done...
but yes, i'm sure 3 or 4 plugs per rotor would be mandatory, but again, if the FIA allowed them to run it, and didn't break their ***** by cutting the displacement allowed by more than half, the rotary really doesn't HAVE to run more rpm: think of the volumetric efficiency advantages!!!! (see any 13B torque curve to see what i mean... like a pancake)

i am a staunch believer that rotaries have a far higher potential for comparable performance over piston engines, obviously...

**edit: ya Herc, it's actually 19K rpm (which was previously though to be the theroetical threshold, at about 18, 6** where the harmonic imbalance from the V10 layout would limit further development... but obviously, the FIA's engineers were very, VERY wrong... ) that BMW broke at Imola this last season...

Buger

Link: http://f1.racing-live.com/en/index.h...0758.shtml</a>

Macabre

Not true! Rotaries are inherently less efficient than 4-stroke piston engines. If they allowed 3.5L rotaries to compete with 3.5L 4-strokes, they would need to rev more than half as high to reach the same output. Still, the rotaries would have to pit twice as often or carry twice as much fuel (since they consume their displacement of air/fuel every rotation) making them completely uncompetitive anyways, so a 1.75L rotary that rev'd higher would make more sense. But is it possible using only conventional materials, since F1 does not allow exotic components inside the engine?

wakeech

my friend, if the displacement was the same, and the revs were only half as high (which wouldn't be the case at all), even accounting for the lower efficiency (which with enough research and competition in design), they then wouldn't need to carry twice the fuel...

but yes, the FIA would obviously cut the displacement in half, because if the rotary could hit 66.7% of the RPM limit the piston engine guys could (which is easy: only 12-13K rpm) they'd be making way the hell more power... true, the fuel cost is there in this case, and the inherent higher tyre wear, but that's why Ferrari does 3 stoppers with the power, speed follows, trust me. i don't wanna get into kart race tactics on this forum though

but "not exotic"?? they've banned certain fairly toxic metals, but that doesn't mean meturlagists at Ilmor, Ferrari, BMW, and Cosworth cannot use ones that aren't banned... and the regs say that the alloys have to be mostly aluminum (and only for most major components, whilst the plethora of other tiny little bits which are particular to each engine aren't regulated nearly as much), which is what they'd be anyways... also, they haven't banned ceramics, which are progressively finding new uses due to their heat resistance and light weight, although brittle, and carbon fibre components...
i mean, i don't blame you for not following the regs, 'cause who really cares anyways?? btw, the engine displacements were set back to 3.0L back in '98, i think... and the materials regs were put in place for the end of '99 (which is why Mercedes' engines have sucked thus far afterward... Illmor'd put a LOT of coin and time into beryllium...)
but ya, a rotary in F1 would be a very very competitive engine right from the get go... even at half the displacement.