I noticed the max HP is at 8500 RPM, would that be a good time to shift, or would you achieve the best times if you waited until around 9500, right before the fuel shutoff?

 

shift at 9000, that way just as you lift off throttle and clutch in, you will hover just below fuel cutoff for a moment before you engage the next gear.

 

Well it is where you landed in the next gear that counts really isn't it.

If you landed in the 4K next gear, and it is certainly less powerful than if you are in 5K in the next gear.

I shift where the red line is.

And you arguement of top power is not just. Yes the peak power is prob about 8500 rpm but the difference in 9K is not that much difference. Well certainly the difference is less than the difference b/n 4000 and 5000 rpm.

 

takahashi is corrrect; for max acceleration, you want to make the most power possible after the upshift. To do that, shift as high as possible before fuel cutoff.

 

I shift at 9K but I too thought that if it made the max HP at 8.5K that maybe I should shift there. Thanks for the explanation (and for posting this)...9K-9.2K (per a video from Japan I saw from a Mazda driver running the 8 on a track) is the sweet spot. But...I'll probably stick to 9K to be safe. :D

 

I have a Pilot shift light (I know it is from Japan) that plugs into the cigarette (12V) lighter.

It does not need to hook up to the PCM/ECU. It simply judge the voltage and hence the rev range. You have to set it up by pressing the button at, say 9000rpm. The shift light will record that voltage (or something) and can bling when it reaches 9000rpm. I set it up at 8500rpm due to my poor reflex, but hey if it is about 100 or 200 rpm out, I don't care. I can not that quick with my shifter, even with RP short shifter, anyway .

Yes, shift lamp is what I am recommending here.

 

I normally shift at around 9300-9400rpm. I figure it is right before fuel cut off, and will allow me to be at a higher rpm when I shift into the next gear. Not sure how good this is for the engine, so I rarely do it. But I drive my car like a grandma compared to a lot of people.

 

The idea is to shift at the point where you'll be making as-much, or more power than before you shifted. If you're making peak power at 8500 in 3rd gear, say, 190hp...and you hold the gear to 9400. Look at your dyno plot - if you are making more power at 9400 than you would at (whatever RPM comes after the shift) it's good to run the thing out. If you would have been making more power at (whatever RPM the next gear would be, at that speed), then you should have shifted...that make any sense?

 

also one more thing to factor in, the tachometer in the car is not super accurate either. I normaly shift at 8500.

 

Yea because I have seen the needle go close to 10,000 and not hit the fuel cut off, I think it is a little behind.

 

Take a look at some Dyno figures from any RX-8. There is a massive HP and torque drop off close to redline. If you wanted to calculate exactly where you should shift for maximum acceleration...do the following.

1) Take a print out of a typical RX-8 Dyno test.

2) Find out the RPM drop as you move through the gears during acceleration.
Note: Each gear shift might be different than the next and it will also depend on your shift point (RPM)

3) Plot the RPM drop as a horizontal line on the Dyno graph and find the RPM point that gives you the most torque and HP through till the next gear.

Shifting at the exact power peak or shifting so that the next gear will be at the power peak is not the way to go. You have to shift so the you have the most amount of power throughout that whole next higher gear.

 

Gosh...I thought you put it in gear and stomp on the gas...LOL

 

I would think that the idea is to shift at the point that gives you the best average power between BOTH gears not just the next gear.