LVDell

Just a bit confused as I was reading through my manual and came across the engine hp/torque bands. While the hp line appears to be linear (for the most part) the toque line appears to have a huge dip between 5K-6.5K rpms.

Does anybody have an expantion on this? My rationale for this is that I am trying to find where the optimal rpm shift point is based on the numbers supplied by PAG/PCNA in the manual. Would it be 6.5K??? Of course I love taking it to 8K like everybody else....that scream is intoxicating. But, and this is a big but (not butt ), why would you shift above 6.5K when you start to have a huge decline in toque?

TIA!

DanH

You need to consider where you will arrive in the power band in the next gear, not just where it starts to drop off in the current gear.

So ideally you need a cascade curve which is a job for a computer

99firehawk

what he said, you need to have the rpm in a spot (and your speed) where the gear change puts you back into the the band

LVDell

Uh-oh, now my brain hurts. So in that case, looking at the transmission graph, it appears that a gear change between 7-7.5K would drop you back in the 5-5.5K rpm range for the next gear up change and thus at the meat of the torque band and on the steep slope UP at the end of the hp band. Am I reading that correctly?

DanH

Yep but you need to factor in the revs you lose as you lift off the gas and perform the shift, so maybe a little higher I guess. This has been discussed before and I think 7.8 was suggested as the sweetspot although it varies a bit by gear I would suspect.

ltcjmramos

Having reviewed the chart in the Tech Manual, and not being nearly as technical as most, I inquired this of a PCA driving instructor, he being a GT3 driver, too. He recommended 7.5-7.7. I didn't get into a technical discussion about it, just asked, and do. I'd assume the low-end to compensate for the fact it takes me (being an old guy) some time to recognize and act.

Nordschleife

OK - lets get a tad educational here - think V - what begins with the letter V. Apart from the V Letters that is.

R+C

LVDell

Victory?

DanH

Viagra?

ltcjmramos

Velocity?

CT03911

vroom, vroooooom

Z06

HP is measured by torque..at 5250 rpms they are equal...300hp would equal 300lbtq at 5250rpm.

when looking for shift points you need an engine dyno or chassis and try to get as much total power under the curve of the gearing..

For the gt3 you want it to land at least 6500 rpm and up.

zoomzoom

variocam turns on around 5500rpm IIRC, and it's also where the resonance flap will open. One of the diagnostic checks is for correct actuation of the resonance flap... they have been known to fail on a few cars which causes a dip between the 5-6.5krpms from which the dyno never recovers. Worth checking if your dyno reads low.

Earlierapex

What you are really asking about is HP vs. Torque. While a lot of people think Torque is more important because HP is just a "mathematical calculation," the truth is that that mathematical calculation takes into account the gearing of the car.

Your car will have the highest rate of acceleration at it's torque peak in any particular gear, but if it had a continuously variable transmission, it would have the highest overall acceleration at the HP peak.

Here's how to judge the best shift point:
1) look at the hP curve
2) calculate whether the HP is higher in the lower gear or the next highest gear after taking into account the HP drop due to the drop in RPMs when you shift. As an example, let's say you drop 2000 RPMs between 2nd and 3rd. Is the HP higher at 8000RPms (2nd) or 6000 RPMs (3rd)?
3) stay in the gear with the higher HP for as long as possible (almost always take it to redline).

Even though the engine torque starts to fall off, the torque multiplication due to the lower gearing will give you more effective torque at the wheels in a lower gear. Usually, this more than compensates for the torque drop as RPms increase.

To measure the relative torque difference between gears, just divide by the RPM drop. In the example above, the 3rd gear overall torque multiplication would be 75% of second gear (6000/8000). In other words, the engine would have to produce 25% more torque at 6000 RPMs than at 8000 RPMs in order to justify using a higher gear before redline.

Most people mistakenly think Torque is king. In reality, RPMs (and HP) are where it's at. Look at F1, they don't rev to 15,000 plus RPMs just to sound good.

Stay in the lower gear and bang it off the rev limiter; that's what these cars were made to do.

1999Porsche911

In the 3, shift near redline in each gear to maintain maximum velocity.