I remember that Sev once posted that to obtain optimal times he shifted just before cut off and not at redline - can someone else corroborate this? Does shifting at cutoff give you better times than shifting at redline??

I don't doubt what the mighty Sev says I was just wondering if someone else has experienced this. We all know that Sev has a stronger car than most so I am not entirely sure if his powerband matches a stock S2K's powerband exactly.

 

You have more torque in the lower gears. Shift right before cut off in any car to maximize times.

 

Based on the HP/torque curves in each gear that have been posted here, there is no crossover where increasing RPM causes lower torque to be available. Normally, this is where you'd shift - at the RPM where torque in the lower gear matches the increasing torque curve in the next gear. Since the engine design precludes that crossover, shifting at as high and RPM as possible would be the fastest way to accelerate. Using the rev limiter as the absolute max. RPM is the goal but be sure to not actually invoke it since the timing of the shift may cause power loss...

 

In GT3 (as well as when I take my S2K out in the real world), the theory of holding a lower gear past the redline WILL result in quicker acceleration. The reason: when you shift, your RPMs decrease (along with your hp & torque). So, by holding the lower gear longer you will accelerate faster. In addition, when you do finally up shift, the RPMs will be higher than they would be if you shifted at the redline, thus reduce the loss of hp & torque. . .

 

[QUOTE]Originally posted by jguerdat
[B]Normally, this is where you'd shift - at the RPM where torque in the lower gear matches the increasing torque curve in the next gear.

 

Actually, it has to do more with gearing then anything else.

Power is important, however it is the gearing that dicatetes whether an upshift is warranted. You want to be in the gear that gives you the most torque at the wheels, in 1, 2 and 3 you should stay untill cut-off, in 4 and 5, you shift at redline, 1-2-3 are further away from each other while 4-5-6 are closer so once the engine torque and thus the HP starts droping past peak HP which is 8300 RPM, you will reach a point that it is better to upshift.

Here is a quick example of what it looks like:



I believe it was made by Soloracer...

 

[QUOTE]Originally posted by Sev
[B]Actually, it has to do more with gearing then anything else.

 

Actually, you do shift based on torque. What really matters is the rearward force the tires exert on the road. That is what accelerates the car. This force is strictly a function of engine torque, gear ratios, and tire diameter (ENGINE TORQUE times GEAR RATIO times REAR END GEAR RATIO divided by TIRE RADIUS).

Ignoring rev limits for the moment, any engine's torque curve eventually falls off at high rpm. The optimum rpm to shift is when ENGINE TORQUE times GEAR RATIO (which is what the driveshaft sees) falls below what it would be in the next higher gear.

Depending on the shape of the torque curve and the gear ratios, redline or the rev limiter may force you to shift before the crossover occurs. You can see this in the curves posted by Sev.

I'm sure this has been discussed many times, but never seems settled.

 

Based on the Stock Stook dyno chart I saw, Stook's power curve peaks so late that redline is not the best shift point in any gear. ('cuz you drop to 6000RPM after each shift at redline. The horsepower there is significantly less than that at 9000RPM in the previous gear) So somewhere beyond the redline is better than redline. Too bad dyno charts don't show things beyond redline.
To conclude, try to shift at fuel cut-off - if you know where it is....

Yee Man

PS BTW, where is the fuel cut-off? 10000RPM? I only see the tacho blinks when I reach the redline. Sorta like winning a jackpot...