8_wannabe

yo, take care out there ferrett. Handling a camera at 130 mph ain't exactly conducive to long life expectancy. We'd like to see you at one of our San Diego gatherings -- in one piece!

btw, what's that black thing sticking up over your dash, at about the 1:00 position on the steering wheel?

FirstSpin

Ramblin Man, it's been my experience and I've seen others post it on here, that speed is about 1/100th of rpms in third. That is, at 6,000 rpm's you're apt to be going about 60; at 5,000 - 50 mph etc. I know this is true on my car up to 75 or so. While I've been to the low 90's mph in 3rd I couldn't "testify" about the tach at that speed. I heard no buzzers or bells and wasn't trying to red-line it so my guess is that the relationship gets non-linear at the higher speeds.

Are you sure you were going 88 at 6,000 in 3rd?

sferrett

I try to limit the number of ridiculous things I do to about one a month - yes I do not recommend repeating my actions and I won't be doing it again myself either (although I am a little bummed about the refelction)

The black thing sticking up is a GPS antenna - I have a mount for my Garmin GPS-V on the dash there so it's easy to see when I'm driving or using it for directions.

eclps0

I toped 4th gear at 130-135 and put it in 5th going up to 140 and then i shutdown and just put it in N and coasted to 90 and then rev matched in 6th. I saw my gas needle go down its pretty freeky

joejoe

I did it trying to see if it would save me some gas. You shift about every 2 sec and it did not save me any gas.

Mitch Strickler

The calculated max speeds are:
44
79.5
122

By calculated, I mean taking the gearing, in mph/1,000 rpm, and multiplying by the 7,500 rpm redline. This should be accurate for the first three gears, because they should be able to hit redline despite wind (and rolling, etc.) resistance.

Fourth is more interesting. One poster said his AT seemed to cut out at 125, as if Mazda had set it that way. Because the AT is geared at 23.5 mph/1,000 rpm in fourth, the theoretical top is 176. And you might make it with a hurricane tail wind, if you weren't blown off the road or hit with a falling tree first. Based on Mazda figures for the European standard engine, which has a 5 speed manual geared closer to our AT than the MT, I think an ungoverned AT would do about 140. If I get a chance at a long straightaway at Summit Point this Spring, I'll report on how mine performs.
One hint about a Mazda-imposed 125 top would be the rating of the 16" tires that come standard with the AT. The 18" ones for the MT (which I bought in the option package) are rated W: 168 mph. Would someone please give the speed rating for the 16s -- and the wear and heat/traction ratings, too.

TM45

Road and Track's calculations are quite close to those reported above, but differ.
They tested a 6-speed Rx-8 and at 9000 RPM, reported the following:

1st-39 mph
2nd-65
3rd-89
4th-124
5th-147
6th-148 at 7650 RPM (electronically limited)

I have found 6th gear to be very close to 20mph per 1000 RPM, so I would reckon the speeds to be slightly higher than Road and Track--more in line with what others calculated above. Speeds over 148 are supposedly not possible, however. I won't be challenging that claim, but has anyone else?

Mitch Strickler

Once you get into tiny differences in estimated speeds, it's time to step back and realize that we can't be perfectly precise. The exact diameter of a tire, for example, under different conditions and with different tread wear, or whether the surface is glass-smooth. Sure, 6th in MT is close to 20 mph/1,000. According to Road & Track, 19.4. They doubtless got that with sophisticated instruments, run by experienced testers, and they list the temperature and wind conditions so you can guess at adjusments to your own situation on a given day. For sure, more accurate than comparing a tach and the (optimistic, almost by law) speedometer. My calculator says that R&T's 148 mph is the product of 7,650 rpm -- something that can be checked pretty accurately, I think -- times 19.4. To return to my main point, 148 is a good number, and 146 may be all right, too, or even 150, if it makes someone feel better.