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-   -   RPM too high in 6th gear? (https://www.rx8club.com/rx-8-discussion-3/rpm-too-high-6th-gear-93807/)

Ninonemo 07-05-2006 05:09 PM

RPM too high in 6th gear?
 
I got to do some long-distance highway driving and took a look at the RPM meter. I was shocked that at 60mph, it's at about 3000rpm. At 75mph, it's at about 3500rpm!

Isn't this too high, or are all rotaries like this? Or is just my car?

Old Rotor 07-05-2006 05:29 PM

This is normal for a rotary, it has very little torgue in the lower RPM's. You must drive V8's.

daisuke 07-05-2006 05:35 PM

forget rotaries, pretty much all manual cars run at those revs, my saturn runs at 3300 in 5th gear at 75, any lower gearing and you don't have any pulling power when in final gear. My aunt has a celica 5 spd (newest model) and it's running at around 4000 when doing 80, there is a 6 spd model though and I assume that runs a bit more relaxed.

having driven a 6-spd toyota truck, I almost found the 6 gears to be more of a pain in the ass than anything else because you can basically skip gears in nearly every situation. 1st-2nd-4th or 1st-3rd-4th was all I was doing... but that's another ballgame I guess.

Edit: forget what I said about pretty much all cars, just make that pretty much all 4-bangers.

1.3L 07-05-2006 05:51 PM


Originally Posted by Ninonemo
I got to do some long-distance highway driving and took a look at the RPM meter. I was shocked that at 60mph, it's at about 3000rpm. At 75mph, it's at about 3500rpm!

Isn't this too high, or are all rotaries like this? Or is just my car?

No, that is normal. And don't forget, when the tach shows 3000 RPM, the rotors are only spinning at 1000 RPM, which isn't much.

Also, as a comparison, a Honda S2000 spins at 3250 RPM at 60 MPH, so the RX-8 is right in the ball park (in terms of crankshaft and eccentric shaft speeds).

1.3L

3rdRXlover 07-05-2006 05:57 PM

I'm no engineer, but I believe that is how the rotary makes up for the small displacement of the engine.
To get the necessary Energy you have to burn X amount of fuel, either slowly in large gulps with a large cylinder or quickly with small sips. I think that's why the acceleration is so smooth with a rotary vs. a piston.
This is no problem for your engine, I have heard it is better not to baby the rotary as it is designed to be run hard.
Hope you love the car!!
:ylsuper:

expo1 07-05-2006 06:00 PM

The 4.44 rear axle ratio along with 6th 0.843 ratio doesn't help.

lurch519 07-05-2006 06:45 PM

in 6th gear, multiply your rpm times 2, then divide by 100, or just drop the last 2 zeros, and that is your approximate speed

PIGBAIT 07-05-2006 06:53 PM

when you have an engine that redlines at 9500, 3500 doesnt seem all that high to me.

In my 2002 Jetta going down the highway at 80mph it was turning at 4000rpm.

Ninonemo 07-05-2006 06:54 PM

Wow, good to know it's normal. I was pretty scared when I saw that, I really thought I did something bad to my engine.

Hey 3rdRXlover, I've heard the same thing about this car, it sure makes this a great car. Can't wait to reach 1000! I have almost 500 miles on it now... I need to drive more. ;)

Ninonemo 07-05-2006 06:57 PM


Originally Posted by lurch519
in 6th gear, multiply your rpm times 2, then divide by 100, or just drop the last 2 zeros, and that is your approximate speed

Kewl, that works pretty good.

SayNoToPistons 07-05-2006 07:32 PM

its about the same on the FC's and FD's..

mysql101 07-05-2006 07:34 PM


Originally Posted by Ninonemo
Wow, good to know it's normal. I was pretty scared when I saw that, I really thought I did something bad to my engine.

Hey 3rdRXlover, I've heard the same thing about this car, it sure makes this a great car. Can't wait to reach 1000! I have almost 500 miles on it now... I need to drive more. ;)

if you want some fun, try driving around town in 3rd gear and hold it at 6,000 rpm. Instant power on tap :)

expo1 07-05-2006 07:52 PM

Just to compare a Mustang GT has a 3.55 rear axle and a .068 overdrive gear. Even though it doesn't redline at 9,000 it's turning MUCH less revs @70 MPH.

lurch519 07-05-2006 08:46 PM


Originally Posted by mysql101
if you want some fun, try driving around town in 3rd gear and hold it at 6,000 rpm. Instant power on tap :)

yeah, and in 3rd gear, just drop the last 2 zeros off of the rpm and you will have your mph

kartweb 07-05-2006 10:54 PM

A couple weeks ago I filled up just before jumping on the highway and setting the cruise control at 75 MPH for the 42 mile ride home. Except this time I was in 5th gear. Rather then turning in my nieghborhood I drove 2 more miles to the local Phillips 66 and filled up again. 2.1 gallons, or about 21.4 MPG. Normally I get between 21 and 22 of course using 6th gear.

Back in the days of "I can't drive 55" I had a 911S - it got better mileage on the highway at legal speeds in 4th then 5th. Volumetric efficiency.

daisuke 07-06-2006 12:07 AM


Originally Posted by expo1
Just to compare a Mustang GT has a 3.55 rear axle and a .068 overdrive gear. Even though it doesn't redline at 9,000 it's turning MUCH less revs @70 MPH.

yeah but that's a friggin V8, you have 3 times the torque so you don't need the revs to keep you going.

spork 07-06-2006 11:01 AM


Originally Posted by mysql101
if you want some fun, try driving around town in 3rd gear and hold it at 6,000 rpm. Instant power on tap :)

Haha, that is a crap load of fun. I like doing that but everytime I do it I feel really guilty ("how much gas am i wasting?") so I don't do it nearly often enough.

the_burtons 07-06-2006 04:20 PM

When I read the title of this thread, I thought "RPM too high in 6th gear? Your going WAY too fast."

toxin440 07-06-2006 04:46 PM

from the guy that drove around in 5th the whole time and got the same milage?

Is this an indication that 6th gear is pretty useless? I mean unless I'm on a 50 mile highway trip... but I've always operated under the assumption if I want to save gas I need to get to 6th gear ASAP. SHould I just ignore 6th gear from now on unless I'm on a road trip.... since it doenst seem to save any gas?

RX8Maine 07-07-2006 07:32 AM

My '99 Civic Si cruised at 70mph/4000 RPM 80mph/4500

When I had my ECU tuned for the supercharger, I could have made more power from 2500-5000 with an early VTEC engagement, but delayed the VTEC until 5000 for this very reason. VTEC = Thirsty.

TomAssBender 07-07-2006 08:21 AM


Originally Posted by 3rdRXlover
This is no problem for your engine, I have heard it is better not to baby the rotary as it is designed to be run hard.
Hope you love the car!!
:ylsuper:

My dealer wouldnt shut up about this, and used the term "Tach this baby!" more times than I care to remember. He even mentioned another one of his customers that races his 8 who came in to the dealer to try to remove the fuel cutoff so that he could take the renesis up to 12,000 rpm's, and he claimed it wouldnt hurt the engine too much (though my dealer was skeptical). But yeah, the harder you ride it the better it runs.

Aseras 07-07-2006 08:36 AM


Originally Posted by TomAssBender
My dealer wouldnt shut up about this, and used the term "Tach this baby!" more times than I care to remember. He even mentioned another one of his customers that races his 8 who came in to the dealer to try to remove the fuel cutoff so that he could take the renesis up to 12,000 rpm's, and he claimed it wouldnt hurt the engine too much (though my dealer was skeptical). But yeah, the harder you ride it the better it runs.

the engine is good to 18,000 rpm or higher.. it the other stuff that breaks like the clutch and pressure plate, input shaft on the transmission and water pump, alternator etc.... just not designed for the huge duty level change of 800 rpm to 10,000+ rpm

The Ace 07-07-2006 08:48 AM


Originally Posted by Aseras
the engine is good to 18,000 rpm or higher.. it the other stuff that breaks like the clutch and pressure plate, input shaft on the transmission and water pump, alternator etc.... just not designed for the huge duty level change of 800 rpm to 10,000+ rpm

If by "the engine" you mean also the eccentric shaft, which obviously you do, then boy are you wrong :rollingla

The shaft in the Renesis (i.e. with two rotors revolving) has been balanced to around 12K RPMs. Anything above that, and you start getting oscillations that will inevitably lead to the fracture of the shaft (and the destruction of the entire engine).

Do NOT go above 10,5K-11K RPMs MAX....

beachdog 07-07-2006 08:19 PM


Originally Posted by 1.3L
No, that is normal. And don't forget, when the tach shows 3000 RPM, the rotors are only spinning at 1000 RPM, which isn't much.

1.3L


Sure about that? Isn't rotor speed 1/2 of shaft speed?

Rotary Rasp 07-09-2006 09:08 PM

1/3 !


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