Shift Points for Maximum Acceleration

[blue2000s]

There's alot of confusion here.

Depending on the power band, there CAN be a benefit to short-shifting but it's not common in production passenger vehicles and clearly not the case with the Boxster. This is deliberately done by the designers.

I encourage anyone who's really interested in understanding this stuff to look up "Fundamentals of Vehicle Dynamics" by Thomas D. Gillespie.

[z281974]

Excellent data and explanation blue2000s. Its torque at the wheels and only torque at the wheels that accelerates the car. Everything else is just an "old wives tale" repeated over and over, but still not true. If you're getting more torque at the wheels in first gear even beyond engine torque peak, then you stay in first gear until wheel torque is higher in the next gear or you hit redline. Every car (and motorcylce) is different and must be analyzed with this type of chart to determine shift points. I'm a state licensed professional engineer, so I speak with some knowledge of physics and mechanical engineering principles.

Tom

[Rondog]

I've GOT to invite you guys my next cocktail party!!!!

Cheers!!!!

[blue2000s]

Originally Posted by Rondog

I've GOT to invite you guys my next cocktail party!!!!

Cheers!!!!

Every time I've seen engineers at a cocktail party, they can only entertain each other.

[denverpete]

Originally Posted by blue2000s

Every time I've seen engineers at a cocktail party, they can only entertain each other.

Hmmm, this coming from an Engineer? If by entertaining each other they have discussions like this thread - then YEAH, small surprise there.

Personally, I've got better things to do at a party than bore people with detailed discussions of engineering and physics. For example, you can always bore them with Politics and Religion....

[blue2000s]

Originally Posted by denverpete

Hmmm, this coming from an Engineer? If by entertaining each other they have discussions like this thread - then YEAH, small surprise there.

Personally, I've got better things to do at a party than bore people with detailed discussions of engineering and physics. For example, you can always bore them with Politics and Religion....

We talk about what interests us which ends out boring everyone else including spouses and friends. When I see my lady's eyes gloss over (she's an actress with no interest in engineering whatsoever so it happens pretty quickly) I know it's time let her break away.

Usually I can find a couple of other car guys who like to talk about Porsches and Rx-7s.

Now we're totally off topic.

[Brad Roberts]

Great thread!!

I shift when it is safe. LOL

Try this: turn 8 at Willow Springs entering the corner at 120mph almost at redline in 4th gear. In theory I should up shift. No thanks. If I lift for the shift I'm spinning the car at 125mph

I have used this for years in drag racing: shift 500-800 RPM over peak torque to do exactly what has been described above. Hit the sweet spot that keeps the car accelerating.


B

[blue2000s]

Originally Posted by z281974

Excellent data and explanation blue2000s. Its torque at the wheels and only torque at the wheels that accelerates the car. Everything else is just an "old wives tale" repeated over and over, but still not true. If you're getting more torque at the wheels in first gear even beyond engine torque peak, then you stay in first gear until wheel torque is higher in the next gear or you hit redline. Every car (and motorcylce) is different and must be analyzed with this type of chart to determine shift points. I'm a state licensed professional engineer, so I speak with some knowledge of physics and mechanical engineering principles.

Tom

Thanks Tom, I'm a mechanical engineer as well. Just trying to spread a little knowledge.