VWjet

First post... new to the forum and world of rotary engines.

My question is basically looking for some of the uniqueness to the rotary engine. What is the redline? Where is max power and torque achieved on the powerband? I've tried to find some dyno sheets for the RX-7, but to no avail.

I'm considering the new RX-8, but have never driven or even heard a rotary engine. Can someone do something to sell me on this?!

zoom44

read this thread click me
and this thread click me too!
as for how they sound someone on here must have a soundbite for you :D

wakeech

this gets me to thinkin'... does anyone have torque(and thus power) curves for the 13BREW??? or how about any other motor?? that'd be one helluva thread, where the RENESIS could strut its stuff (on paper) against other motors (on paper... :p)

i'd do it, but i haven't anything like that.

Rich

If you want to get an idea of what I think of rotary engines, check out this thread:
"OMG! Just drove an FD again"
and this one compares it to the S2000.

I expect the RENESIS to be a lot like the S2000 engine with a bit more punch off the line, no VTEC "spike" in torque, and much, much, much more smooth higher in the rev range. Whereas all piston engines begine to complain (to varying degrees) as the revs rise, all the rotary engines I've driven get more and more smooth the more they rev. It's nice and comfortable to cruise at 6k in an FD, but it's not in any piston car I've driven.
There's a reason they make the rev limiter buzzer so loud in these cars! You can hit it without realizing it, and redline comes up *fast*.

PatrickB

Has Mazda traditionally geared its rotary engine cars (especially the final gear ratio) tighter than what people are normally used to in standard transmission cars?

For example, most people in "normal" cars shift at 3500 or so RPM, which comes at about 15-18 MPH in first gear in many cars. Does Mazda change the final gear ratio to get more power to the wheels, making the engine at a higher RPM at the same speedometer setting? It would seem to make sense to do that, but I've never heard anyone compare gear ratios on rotaries compared to other cars...

wakeech

i don't know about comparisons with other cars, but i do know that in the case of the FC, Mazda left the upper 3 gears on a closer and shorter ratiofor the NA than on the TURBO II to better use the higher rev limit (and lower level of power)...

so, my thought is maybe the gearing on the 8 will be pretty low... MikeW posted a thread about this before...

Buger

quote:
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Originally posted by PatrickB

Has Mazda traditionally geared its rotary engine cars (especially the final gear ratio) tighter than what people are normally used to in standard transmission cars?

For example, most people in "normal" cars shift at 3500 or so RPM, which comes at about 15-18 MPH in first gear in many cars. Does Mazda change the final gear ratio to get more power to the wheels, making the engine at a higher RPM at the same speedometer setting? It would seem to make sense to do that, but I've never heard anyone compare gear ratios on rotaries compared to other cars...
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Hi Patrick,

I believe Mazda has geared it's rotary cars similar to 4 cylinder cars in the past. The higher ratio and closer gearing in lower torque cars gives the car more torque to the wheels but would generally cause you to shift quicker. The important thing that rotaries have over 4 cyl engines is their almost linear torque curve and their very high redlines. These 2 things allows Mazda the opportunity to gear rotary cars with a higher ratio and still offer a driving experience where you don't have to shift all of the time (like the s2000).

The way the 3rd gen rx-7 was geared, it would be going 18 mph at 3500 rpm in 1st gear. This is based on 225/50-16 wheels and their 1st gear ratio of 3.483 and the final drive ratio of 4.1. Previous 5-speed rx-7s since 1986 have all had final drive ratios of 4.1. The rx-8 may be using the same 4.1 rear diff (to save costs) and have much closer ratios in the new 6-speed transmission. I would like to know what the numbers will be. Any guesses?

I hope this post was readable. I'm trying to type it very quickly while the wife is yelling at me to come and eat dinner.

I previously posted the below on the subject:

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The production gearing and diff ratios have been what I've been hoping would be leaked by Mazda but I think they want to surprise everyone.

Having an engine with the powerband and redline of the renesis gives Mazda a great opportunity to increase either the gear ratios or the final diff ratios so that the ratio for all gears will create much more wheel torque than people will expect.

I personally hope that they have a very high ratio because of two reasons.

First of all, the car was designed to seat 4 people and the gearing/diff ratios should take that into account and be much higher than the ratios on the last rx-7 which I believe had the below #s:

1st - 3.483
2nd - 2.015
3rd - 1.391
4th - 1.000
5th - 0.719
Diff - 4.1

and could only fit 2 people.

I would much rather have better acceleration than a high top speed. Even if the top speed were only 130 mph, I would (probably) never get to there (damn tickets).
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Rich

I think that the people who buy an RX-8 won't be "most people", and the RX-8 isn't a normal car. I rarely shift my Miata below 5k, and almost always above 6k; that's where the fun starts!

I do get what you mean though. The reason is less about the gearing and more about the fact that you don't have the normal engine thrash in a rotary that tells you when to shift. Rotaries love to rev, and there's not as much of a sign that you're getting too enthusiastic until you hit the buzzer. That's all I was getting at with my comments above.

BlueAdept

OK, I've reviewed a few of the clips I have here and I think that the clip that might help with the sound is this one:-

ftp://rx8:mazda@ftp.fsck.co.uk/tiirx7_incarlaunch.mpg

It's a TurboII RX-7, and probably has a louder pipe than the RX-8 will, but the thing to notice is the rev counter on the dash... the engine does not sound like the rev counter is pointing past the 7000 RPM mark at all.

And also you might like to see the other files on the FTP server depending on your bandwidth...

ftp://rx8:mazda@ftp.fsck.co.uk/

Hope this answers your question...

RedRotaryRocket

For those interested in comparing to an FD dyno curve, here is the curve from my FD when it was nearly stock...the only mod at the time was a downpipe.

Grimace

Ah, memories of my old FC...

You can hear the redline buzzer sounding in that clip if you listen carefully. He's shifting at redline.
(He also held 1st gear too long, you can hear the engine bounce off the rev limiter for a half a sec.)