On the way to AZ, I had the car pegged in 6th gear. The speedo showed 148 but my Meridian GPS showed 145.7 MPH. From what I could see, there was about a 10 mph tail wind.

Anything over 135 or so the back end felt a little unstable but overall it was solid.

Nice!....you are so very lucky to live out there west where there are miles of hignway straightaways....check out my east coast speed posts in the NE FORUM.......:) --dont you just love the acceleration from 60mph on up. Zoooooooooom

your top speed will actually come at redline in 5th gear... i think you left a few mph on the table that you can find next time

Top speed in fifth not sixth? How does that work?

because the 1 to 1 ratio between engine out-put and tanny out-put is in 5th gear

In 6th gear the wheels are turnning faster then the engine......... ok lost my logic it is supposed to be 6th..... right?

Six Speed (238)
Gear Ratio
1 3.76
2 2.27
3 1.65
4 1.19
5 1.00
6 0.84


Automatic (197)
Gear Ratio
1 2.79
2 1.55
3 1.00
4 0.69Theoretically, without supposed limiter and/or wind resistance you would be able to top out at 157mph on 5th and 186mph on 6th at 9000rpm.

Which would co inside with what that guy on the dyno got, 176mph.

Now this isn't taking into account the amount of air being pushed into the intake at 176mph considering he's on a dyno. Which explains the missing few MPH.

Theres an interesting article about how much ram-air really does help in C&D ill scan the article and post it up in a few.

At the same time that ram air is helping the engine, the car's drag is hurting the engine. In fact I would think the drag would have a much greater impact than the ram air. Therefore, in theory, the car should be slower than the dyno test.

I have seen similar speeds. We are power limited in 6th gear. It just stops accelerating. For top speeds runs it is best to not touch 6th gear.

Originally posted by Prod
At the same time that ram air is helping the engine, the car's drag is hurting the engine. In fact I would think the drag would have a much greater impact than the ram air. Therefore, in theory, the car should be slower than the dyno test.

indeed thats why the guy did 176 on a dyno however if u stick a fan that blows 38,000 cubic feet of air per sec in front of that car on the dyno you would see the 186 number brothervoodoo was talking about.


Originally posted by murix
I have seen similar speeds. We are power limited in 6th gear. It just stops accelerating. For top speeds runs it is best to not touch 6th gear.

Not power limited drag limited.

A guy in the UK ran some numbers, I took the basis of his information and computed the outcomes for our 6-speed and Automatic models. I've posted it here:

http://www.rx8club.com/showthread.php?s=&threadid=25420

you have more torque multiplication in 5th gear, which gets converted into more forward acceleration/force (same reason you accelerate faster in 2nd gear then 4th gear), which means there is more force to overcome the drag force

6th gear is just too damn tall to do a top speed run in unless so have some serious mods

Gents, just reading through your notes and looking at my local data....

I cruise at less than 80MPH at 4000RPM. If I say 79.5MPH, then the 79.5 / 4000 * 9000 = 178.875. Even if folks are getting 80 at 4000, that would work out to 180.

I think the threads that state 186, are... optimistic.

Lastly, the real world top speeds in stock vehicles at 148 is very believable, cause I been to 135 and there was still room to run.

Twin 8s!: Yes, that's exactly the point. What they're saying is that the engine should theoretically be able to push the car to 186 mph--but that either an electronic limiter or the aerodynamic properties of the car are holding it back. Thus, the top speed of the car is 145-150 mph, but it's not that the engine has run out of power.

Peace
policy

I concur to Dugless -albeit euro spec- my car topped out at 149 mph (240Kmh).

I read once somewhere? That fifth and sixth gear will give about the same top speed 148-149mph, because in 6th gear the engine is electronical limited - 7000rpm max.

<beats head against wall >

the car is drag limited in 6th gear, and rev limited in 5th gear.... it just happens rev limited in 5th gear is faster then the drag limited speed in 6th gear