Optimum shift time in Boxster S

[DJ SEVEN]

Well after a lot of saving finally managed to get myself an early Boxster S a couple of days ago - wow, what a car!!

I noticed in a technical spec somewhere that it develops it's 252BHP at 6250 RPM and having changed from third to fourth at 6250 and pinning the throttle again it seems to drop right back into the power band..

Other cars I've had go faster overall if you take them to the limiter. Do you think it's faster to change around 6250 or to take it to the limiter?

Thoughts anyone?!

[blue2000s]

For optimum acceleration, most auto makers will design gearing and powerband in their performance vehicles to be shifted at redline. The Boxster is one of these vehicles.

[Brucelee]

Yes, you should run the car at redline at all times. I am told that the car will last much longer if you keep the pedal to the floor always.

[Bob Z.]

If you can keep the revs between 3 and 4k (blip the throttle) I think you'll find it will perform nicely; however, running it up higher all the time will surely make it feel faster but it cannot be good for the car to be run up to near redline on every shift!

And yes, I know Brucelee was only kidding.

[David N.]

Pretty sure BruceLee wasn't kidding. Although keeping the throttle pinned at all times might certainly be overdoing it, the engine does need to be revved up and down, at least above 4. It clears the valves and simply allows the engine to wear correctly.

[racer_d]

What you also need to consider is when is peak TQ? By keeping the motor between those two peaks, you should have the most power.

You also want to not run the car to redline because, unless the HP and TQ curves show otherwise, peak HP and TQ will drop off (relatively) at that point. I know in my stock 911SC, peak hp was somewhere around 5200rpm and fell off quite abit thereafter (redline was 6250), and peak TQ was around 3700 rpm for instance.

You also dont mention what you wish to optimize? I am assuming speed/acceleration as opposed to Fuel Economy

[ut_cougar]

I agree with brucelee...I don't think he was kidding. Everyone is so afraid of running their cars hard. Times have changed from the mustang and camaro days, with the RX-7's and the mitsu 3000GTs and the supra's... cars are more high-tech and built to last much longer and take more abuse.

I also thought it was stupid to always push your car, hitting red-line all the time... but after my ex bought her new lexus IS300 a while back i took it to the dealer for an oil change and the mechanic said "make sure you floor it and shift at redline everywhere you go"... at first i thought it was a joke, but then he told me the cars need it and thrive off of it. This must have been around 2004 I think, and he said all the cars (2004's and other later models, 03, 02, etc) were the same way, they will thrive and there is no negative to driving them as hard as you possibly can. He also said that he noticed the elderly crowd who would always say they pamper the cars were the ones bringing the cars in after 3 or 4 years due to engine problems, etc. He said the 20's crowd and the group who has rims, mods, etc only came in to the dealer for oil changes, and scheduled visits. He was the head mechanic also that told me this. Since then friends have told me the same thing about their cars when they buy'em new.

[Halfbreed83]

"Times have changed from the mustang and camaro days, with the RX-7's and the mitsu 3000GTs and the supra's... cars are more high-tech and built to last much longer and take more abuse."

Too bad my RX7 didn't make it Also, alot of RX7 owners are throwing in LS1's too make more power and reliability.

[blue2000s]

OK, here's the way it's done. This will probably lead to some useless torque vs power debate that I won't be participating in.

You look at the torque produced at the wheels in every gear for a given vehicle speed. This gives you a set of curves of torque vs vehicle speed. In fact, this will often give you 3-4 gears to choose from at a given speed. You choose the gear that gives you the highest torque at any given speed and you stay there until redline or until the torque curve drops below the torque curve of the next gear. This is part of the process used to define gear ratios and it's also the process you use to decide what shift pattern will give you the best acceleration. In the Boxster, as with just about every other high performance sports car, redline is where you shift in almost every gear.

Here's a spreadsheet showing what I'm talking about. Take off the .txt extension and unzip it.

http://986forum.com/forums/attachment.php?attachmentid=3282

Keeping RPMs between the torque peak and power peak is incorrect and shifting at power peak is incorrect. You ALWAYS have to look at the torque at the wheels if you want to answer this question correctly.

[Brucelee]

It clears the valves and simply allows the engine to wear correctly.

Not sure what you mean by this. Can you elaborate?

[BoxsterLewis]

Shift at 6k and you'll be good to go

[2000SoCalBoxsterS]

Originally Posted by blue2000s

OK, here's the way it's done. This will probably lead to some useless torque vs power debate that I won't be participating in.

You look at the torque produced at the wheels in every gear for a given vehicle speed. This gives you a set of curves of torque vs vehicle speed. In fact, this will often give you 3-4 gears to choose from at a given speed. You choose the gear that gives you the highest torque at any given speed and you stay there until redline or until the torque curve drops below the torque curve of the next gear. This is part of the process used to define gear ratios and it's also the process you use to decide what shift pattern will give you the best acceleration. In the Boxster, as with just about every other high performance sports car, redline is where you shift in almost every gear.

Here's a spreadsheet showing what I'm talking about. Take off the .txt extension and unzip it.

http://986forum.com/forums/attachment.php?attachmentid=3282

Keeping RPMs between the torque peak and power peak is incorrect and shifting at power peak is incorrect. You ALWAYS have to look at the torque at the wheels if you want to answer this question correctly.

O.K. so is this spreadsheet interactive where I can plug in my wheel size, tires, torque... and it will give me my shift points?

[blue2000s]

Originally Posted by 2000SoCalBoxsterS

O.K. so is this spreadsheet interactive where I can plug in my wheel size, tires, torque... and it will give me my shift points?

Yup. You put in the data in the yellow fields and it will output the estimated wheel torque curves. Then you choose the gear that shows the most torque at any given speed.

I think the torque curve in the spreadsheet now is for a 911. I don't remember what car I was looking at when I made that sheet.