I am interested in your comments on the three shifting techniques with the Renesis. As we all know this motor's output is:

238 BHP @ 8,500 RPM
159 ftlb @ 5,500 RPM


1) MAXIMUM PERFROMANCE
Shift at 8,500 or above(above to compensate for RPM drop while clutch is depressed). You get best acceleration and overall perfromance with poor fuel economy.

2) BEST BALANCE
Shift at 5,500 RPM(max torque), get good perfromance while maintaining good fuel consumption, best overall balance in everyday driving.

3) BEST FUEL ECONOMY
Shift at 3,000 RPM, slow but helps the dreaded fuel economy of the Renesis.

:cool:

None of the above.

If you have access to a dyno source data, there are many shift plot excel spreadsheets on the net.

What works best for 1-2 may not work the best for 4-5.

I still have yet to look into this, but it has to deal with the power curve, and how it tapers off near redline.

do a google and you will find some.

The optimum shift point occurs as the available torque tails off to the point where there is more torque available at the wheels in the next gear. However, the relatively flat torque curve of the Renesis, combined with the ratios in the RX-8 6-speed, mean that there is no point where this happens in any gear.

See this post (http://www.rx8club.com/showthread.php?s=&postid=96246#post96246) for a set of cascades which illustrate this point. If the curves intersected, the intersection point would be your optimal shift point, but since they do not, your optimum shift point for performance is as the redline in every gear.

i read in this week's autoweek about them doing acceleration trials on the v6 corvette. and, they said that by shifting into 2nd gear sooner (ie not waiting for 1 to redline i guess), they were able to get 0-60 under 6 seconds. the reason was because the vette's 2nd gear really is where all the power boost is at.

does the 8 have something similar for us to do? does anyone know?

The max torque point on a motor usually coincides with the peak volumetric efficiency, which is where the motor is sucking air/fuel the best, so it is not conducive to best economy. I remember something about Nascar drivers having to back off the throttle as they passed the max torque area, to avoid tranny "overstress".

During some of Canzoomer's early explorations of the power band, he noted the mixture got really lean, with lots of power, between 5500 and 6500 rpm. I ran a whole tank of gas at those revs, so basically never getting into 6th or even 5th gear even on the highway :Eyecrazy: . Fuel mileage didn't improve, but it was really a LOT of fun!

S

The optimum shift point occurs as the available torque tails off to the point where there is more torque available at the wheels in the next gear. However, the relatively flat torque curve of the Renesis, combined with the ratios in the RX-8 6-speed, mean that there is no point where this happens in any gear.

See this post (http://www.rx8club.com/showthread.php?s=&postid=96246#post96246) for a set of cascades which illustrate this point. If the curves intersected, the intersection point would be your optimal shift point, but since they do not, your optimum shift point for performance is as the redline in every gear.

Spot on... :icon_tup:

so... are u saying that for the rx-8, if we want to get the fastest acceleration for 0-60 we should keep the car between 5500-6500 rpms?

who is canzoomer? is he just some guy or do we have info on this subject from some sort of authoritative source?

thanks for the info.

During some of Canzoomer's early explorations of the power band, he noted the mixture got really lean, with lots of power, between 5500 and 6500 rpm. I ran a whole tank of gas at those revs, so basically never getting into 6th or even 5th gear even on the highway :Eyecrazy: . Fuel mileage didn't improve, but it was really a LOT of fun!

S

This topic has been discussed numerous times. do a search if you want more info.

so... are u saying that for the rx-8, if we want to get the fastest acceleration for 0-60 we should keep the car between 5500-6500 rpms?

who is canzoomer? is he just some guy or do we have info on this subject from some sort of authoritative source?

thanks for the info.

Just keep it in the rpm range between peak torque and peak hp, lots of shifitng work but fun and challenging.

The optimum shift point occurs as the available torque tails off to the point where there is more torque available at the wheels in the next gear. However, the relatively flat torque curve of the Renesis, combined with the ratios in the RX-8 6-speed, mean that there is no point where this happens in any gear.

See this post (http://www.rx8club.com/showthread.php?s=&postid=96246#post96246) for a set of cascades which illustrate this point. If the curves intersected, the intersection point would be your optimal shift point, but since they do not, your optimum shift point for performance is as the redline in every gear.

Amply illustrated in this video

http://video.google.com/videoplay?docid=8237690307702536941&q=%2B%22rx-8%22

Amply illustrated in this video

http://video.google.com/videoplay?docid=8237690307702536941&q=%2B%22rx-8%22

I disagree. I think this video is great for showing heal-toe down shifting, but the driver starts in 2nd and only hits 4th and each time he takes the car to 9500 rpm before shifting. Again, revving it to the moon doesnt always produce the best power. Its all about a dyno graph and seeing where the car makes its peak power and keeping it in the power band.

the driver has to shift at a point *after* the point of max horsepower - correct? and not shift *at* the horsepower peak. Because, after the shift, the rpm drop will still keep him closer to the peak power point than if he shifted at the peak power.

So maybe thats why he is going past approx 8.5k (understand peak power depends from car to car - but approx its at 8.5k).

Just my guess.

Bodi