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-   -   rear end ratios ? (https://www.rx8club.com/series-i-tech-garage-22/rear-end-ratios-207696/)

waNkLeR 11-12-2010 07:44 AM

rear end ratios ?
 
cruzing at 130 kmh (78 mph) is a lofty 4000 rpm
any other ratios out there ?

love the car though its a total blast !
tons of brakes and sooooooooooo balanced !

REDRX3RX8 11-12-2010 10:11 AM

My 07 6spd auto would be running about 2700 rpm @78 mph, and I even geared it down 3% with 225/40r18 tires.:)

Z0oMzo0m 11-12-2010 11:55 AM

my 07, at 78mph is around 4k possibly higher.. i have 225/45//18..


^^ how is yours a 6spd auto...??

REDRX3RX8 11-12-2010 12:18 PM

The 8 has always come with auto. The early models were 4spd, my 07 is 6spd.

I really like to shift gears, but I don't like all the associated troubles like throw out bearing noise, and 2nd gear synchro grinding.

This 6spd auto is really good on the track because I can concentrate on driving while the car does the shifting.

I don't even use the manual shift, I just leave in gear, it shifts @7krpm, and if I jump off the gas before 7k it stays in gear to be ready for the throttle in the corner.

fyrstormer 11-12-2010 12:28 PM

My 2nd gear synchro stopped grinding when I put better oil in the gearbox. Chances are, there's still some rubbing and grinding going on even in your automatic, you just can't tell because you don't have a metal rod connecting your hand directly to the transmission. A gearbox is a noisy place to live.

My car also runs 4000rpm @ 78mph in 6th gear. Don't bother me none -- rotaries run 50% higher rpms than piston engines anyway. So to do the math, it's the equivalent of running 2667rpm @ 78mph in a piston engine. That's quite reasonable.

FastFreddy61 11-12-2010 01:25 PM

[quote=fyrstormer;

My car also runs 4000rpm @ 78mph in 6th gear. Don't bother me none -- rotaries run 50% higher rpms than piston engines anyway. So to do the math, it's the equivalent of running 2667rpm @ 78mph in a piston engine. That's quite reasonable.[/quote]

I think you should reconsider this statement, and your math is wrong.

waNkLeR 11-12-2010 02:16 PM

it might just be me but....
perhaps the reason the gas mileage on the highway sucks is the gearing ?

waNkLeR 11-12-2010 02:19 PM


Originally Posted by REDRX3RX8 (Post 3782077)
The 8 has always come with auto. The early models were 4spd, my 07 is 6spd.

I really like to shift gears, but I don't like all the associated troubles like throw out bearing noise, and 2nd gear synchro grinding.

This 6spd auto is really good on the track because I can concentrate on driving while the car does the shifting.

I don't even use the manual shift, I just leave in gear, it shifts @7krpm, and if I jump off the gas before 7k it stays in gear to be ready for the throttle in the corner.

ever had the car "decide" to shift at 9/10ths in a corner ?
thank god for stability control...

i prefer to balance the car and keep in the same gear as god intended lol

REDRX3RX8 11-12-2010 06:01 PM


Originally Posted by waNkLeR (Post 3782246)
ever had the car "decide" to shift at 9/10ths in a corner ?
thank god for stability control...

i prefer to balance the car and keep in the same gear as god intended lol

Ha! Well ah yes and no. I like my auto because I knew auto was ready made for a smooth and low torque engine with a wide power band like a rotary. I'm retired, weak, and can barely walk, so my driving style on the track is: stomp the gas, stomp the brakes, yank the steering wheel, repeat. It works great on a track with a rotary, and yes, I like the traction control because it doesn't come on unless I'm out of shape.

So right after I yank the wheel, (all at once is the proper way anyway, not slowly turn) I jump the gas. As I'm settling in on the drift after slowing from say 90mph to 60mph, the tranny is shifting down hunting the right gear, and I feel the (low torque remember) power smoothly come in. I did say that the tranny stays in gear when I jump off the gas on a slow speed corner (say 40mph).

The auto doesn't sound like a pure race car, but its my dream car, and the newer supercars are gonna shift similiarly.:eyetwitch

REDRX3RX8 11-13-2010 06:10 AM


Originally Posted by waNkLeR (Post 3781743)
cruzing at 130 kmh (78 mph) is a lofty 4000 rpm
any other ratios out there ?

love the car though its a total blast !
tons of brakes and sooooooooooo balanced !

Yeah, like ya said sooooooooooo balanced!

Even with 6spd Automatic.

I also got the highway EPA mileage of 25mpg when I drove it to Dallas recently at 70-80mph with AC on.;)

TeamRX8 11-13-2010 09:31 AM

It will take a lot of gas mileage improvement to justify the expense, about $1000 or so installed

olddragger 11-13-2010 07:59 PM

there are 3 rear diff ratios that I know of.
the 4:44---04-08 6 speed car?
the 4:77--S2 6 speed ?
a 4:3 something--the autos?
The s2 trans also will change things for you
lower rpms will improve your mpg--but like team said--may not be worth it.
OD
OD

jasonrxeight 11-13-2010 08:49 PM


Originally Posted by olddragger (Post 3783201)
there are 3 rear diff ratios that I know of.
the 4:44---04-08 6 speed car?
the 4:77--S2 6 speed ?
a 4:3 something--the autos?
The s2 trans also will change things for you
lower rpms will improve your mpg--but like team said--may not be worth it.
OD
OD

S2 has a taller 6th gear so top gear speed/rpm is the same as S1 only 1st-5th gear are geared down.

TeamRX8 11-13-2010 09:54 PM

All the FD3 gears, all the SE3P gears, and the Motorsport 5.12 gear

https://www.rx8club.com/mazmart-88/every-diff-ratio-180758/

.

lilring 11-14-2010 01:26 AM

i belive the 04-08 autos have the 4:10

REDRX3RX8 11-14-2010 09:12 AM

My 6spd auto has 4.3 like OD said, but with 225/40r18 tires, I now have 4.44 like the big boys.:lol:

waNkLeR 11-14-2010 10:27 AM


Originally Posted by TeamRX8 (Post 3782911)
It will take a lot of gas mileage improvement to justify the expense, about $1000 or so installed

i do my own work so that isnt an issue :)

Rotaman 11-14-2010 02:14 PM

I changed my rear ratio from the standard 4.4-1 to 3.9-1 and that dropped the revs down by around 500rpm. So now at cruise speed which is around 130kph or about 80mph, my car sits at around 3500rpm. My car is a JDM 6speed.
The gear ratio set that I used was from a fd RX7.
I also hated the high revs the RX8 revved at on the open road. I was used to my RX2 which had a 5speed and 3.9 gears and sat at around 3-3500rpm at around the same speed.

Brettus 11-14-2010 02:31 PM


Originally Posted by Rotaman (Post 3783560)
So now at cruise speed which is around 130kph or about 80mph, .

You need a radar detector !

olddragger 11-14-2010 05:28 PM

i put the 09 trans into my 04 model--so my cruising rpms are lower.
i can get 25 mpg with my s.c'ed car.
od


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