I think this gains us the knowledge that our RX-8's are pretty powerful cars, inspite of some gear ratio compromises in the transmission. I delved into this because many folks tend to compare the RX-8 to the S2000 and even the much more powerful 350Z. Now that we have become a bit more aware that the RX-8 6-speed transmissions are possibly a bit more of a compromise (all-out acceleration vs fuel economy) than the competition, maybe we'll tend to be a little more happy with what the Renesis can muster up?

1.3L

 

6th gear is, if anything, too low. Cruising at 4000 rpm at 80 mph is wasteful. A taller gear would be more appropriate, though I imagine there's an acceleration limit below which Mazda didn't want to go. With the small amount of torque available, on-demand acceleration in 6th with a taller gear would be feeble indeed.

How to make everyone happy? - space 1 through 6 more closely, and add a 7th gear! :D

 

hahha nice sentiment but it wont make anyone happier.

 

Changing the gearing ratio would get you to redline quicker downside is the compromising fuel economy and it would be harder to drive for your average joe blow .

This cars gearing has been set up for easy use for the average daily driver .

Anyway i dont find the need to justify my gearing to either the S2000 or the 350z drivers .

Some people are best kept in the dark

cheers
michael

 

Ah, maybe not. After reading this, I did some calculations based on the published data that 3000 RPM in 6th gear will get you 60 MPH. From that, I came up with the following speeds at 9000 RPM:

1st = 39 MPH
2nd = 66 MPH
3rd = 90 MPH
4th = 129 MPH
5th = 150 MPH (hypothetical)
6th = 180 MPH (hypothetical)

All of these speeds are very close (except 4th, which was published as 124 MPH. I didn't do the math, but I guess that equates to about 8750 RPM) to the ones I found published by the popular automotive magazines, so it appears that the drivers were going past the 8500 RPM point where max rated power is achieved. Also, if they proceeded on to where the fuel cut-off comes in (9250, presumably) as someone suggested, I calculated the following:

1st = 40 MPH
2nd = 68 MPH
3rd = 92 MPH
4th = 132 MPH
5th = 154 (hypothetical)
6th = 185 (hypothetical)

As you can see, there's not much speed to be gained by forcing the Renesis to the fuel cut-off point. I would think that hitting the fuel cut-off point would just add another (small) element of inefficiency to equation simply because the engine would sag for a split-second, just before a gear change up??

1.3L

 

wow

 

"6th gear is, if anything, too low. Cruising at 4000 rpm at 80 mph is wasteful. A taller gear would be more appropriate"

I Agree - It would be much better to cruise the freeway at 2000 RPM and
downshift if I need the power - That would help there MPG #'s

I have been tring to drive at under 3500 RPM but find it difficult to only drive 72 MPH

 

well, you definately don't want to hit the fuel cut off, that would without a doubt negatively affect acceleration. but going past peak power, and even past red line, but shifting before fuel cut off could be benificial. see my post post at the bottom of page 1 for a possible reason as to why this may be so.

and i agree with some of the people in that 6th is too low. i would much rather it be taller and be able to run highway speeds at a lower rpm. if i wanted it to be a race car and only a race car i'd replace the stock transmission with something that was specifically designed for the application.

but oh well. the car is what it is. its a great car, and i love every minute that i drive in it, but it isn't without fault. can't think of a car out there that doesn't have some fault to it. but i think it is a damn fine car that has the potential to put a smile on any one's face that drives it, and at an extremely reasonable price.

to quote my dad after i let him drive my 8, "i could very easily get into a second childhood in that car. i can't believe how smooth it drives and how well it handles".

 

I take it that the RX8 cannot actually get to 9000 RPM in either 5th or 6th gears. It must max out at 8500 in 5th and 7200 in 6th (148 mph). If the engine spins any faster than this, and you can only go 148 mph, then something must be slipping, i.e. the clutch, differential, or tires.

 

Huh? The definition of a drag-limited top speed is that the engine cannot overcome the aerodynamic and frictional forces. If you put the car on a chassis dyno where aero drag doesn't exist, you can easily get the speedo to read over 148 mph in 5th or 6th gears.

 

I think someone should make a mod and a DIY on replacing 6th with a real overdrive gear. say 80mph @ 3000 rpm.

 

I've got it! It needs a 7-speed tranny! :D

1.3L

 

Oops. Sorry I wasn't clear. I've never really given this much thought before. If the car has a 148 mph max speed, it must be true that you can't get the engine to cruise at 9000 RPM in 5th or 6th gears -- on the road. I hadn't heard the term "drag-limited top speed" before, but it makes sense. And I haven't actually ever observed the 5th or 6th speed limits.

 

I was looking at a power graph published on the M/T website and while I'll admit that it's not the most finely detailed graph in the world, it appears that the power curve increase to peak HP @ 8500 RPM is pretty much the same shape as the power curve down side beyond 8500. So, I think by going past the redline, you would lose about as much as you'd gain and therefore would see little, if any, difference.

1.3L

 

f*** it, im swapping in a TII tranny.

 

since the power output is the same, going past redline isn't a negatively affecting performance, and after you shift, you'll be at a higher rpm than if you shifted at at peak power, which will help keep you more in the sweet spot of the power band.