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It's about the area under the curves. So, although the point of intersection is optimum, the goal is to stay in the rev range that optimizes area under the curve.
This is exactly right for maximum performance. For maximum engine life you'll be shifting at substantially lower rpms most of the time (but not where that ridiculous up-shift indicator on the dash would suggest).
The power curve on my 997.1s is at 6500 rpm. You can feel it so clearly in second gear. Beyond that it’s a case of diminishing returns. The 997 engine is an amazing piece of engineering in that it can fit in with the daily commuters and putter along at 3-4k rpm but when asked can light up to 6500 and beyond and make mothers clutch their children closer. I love the Dr. Jekyll and Mr. Hyde character to my car. Enjoy the power every once in a while. It’s fun and the engine is designed to handle it. Why else would you have a 911?
The relationship between when to shift and the load on the engine is relative, so try cruising through a main street with a 30 MPH speed limit in 1st or 2nd gear. It's ludicrous. Go ahead and shift into third, and you're breaking every rule given to you by anyone who thinks they 'know when to shift'.
Under almost no load, on a flat grade, you can cruise at 30 in 3rd gear. Should you crawl up a hill or stomp on it in 3rd at 30 MPH? No.
When to shift? If you have to ask, you need an experienced person going through dozens and dozens of real-life scenarios as they sit next to you in the car.
If you're truly driving the car for performance, then you obviously will shift when going higher in RPMs gains you nothing. The key to shifting (which I shouldn't even have to write here on a PORSCHE forum) is to shift so that when the next gear is selected (as you are going up through the gears) it winds up in the peak of its HP production--otherwise you wind up lugging the engine. Shifting prematurely causes the engine speed to be beneath the optimal RPM point in the next higher gear, resulting in a lugging of the engine until you get the RPMs up again.
For example, these engines come on 'the cam' at around 4000 rpms so make sure that when you shift the needle winds up at 4000 as you select the next gear--and then accelerate to wherever you need to be to hit 4000 at the next shift. Fortunately, these are much higher displacement engines than ever before and you need not worry so much about lugging these engines as you used to--they can generate quite a bit of HP even at rpms much lower than ever before.
Originally Posted by Quadcammer
no.
you aren't lugging a 997 motor at 2000rpm. Unless you are opening up the throttle in a high gear, you aren't lugging it at 1500rpm. You'd have to do something pretty stupid to lug a modern porsche engine. This aint a roller bearing 356 or 2.4 that has maybe 130lb ft of torque at its peak.
I don't have a 997, but under normal driving, I shift my 993tt at about 3000rpm. Under hard driving, whenever I feel like it.
so maybe lugging was overstated ?
But isn't Edgy01 onto something ?
If your goal was to go zero to 120 mph in as fast a time as possible .... would the "Shift at X thousand RPM, such that the RPMs end at 4,000 after the shift" be the way to get the fastest 0 to 120 mph times ? Any other ideas of how to shift to accomplish the goal ?
Is this called keeping the car in the Power Band ?
The power curve on my 997.1s is at 6500 rpm. You can feel it so clearly in second gear. Beyond that it’s a case of diminishing returns. The 997 engine is an amazing piece of engineering in that it can fit in with the daily commuters and putter along at 3-4k rpm but when asked can light up to 6500 and beyond and make mothers clutch their children closer. I love the Dr. Jekyll and Mr. Hyde character to my car. Enjoy the power every once in a while. It’s fun and the engine is designed to handle it. Why else would you have a 911?
Is the power curve the same in all gears ?
Do you suggest shifting at 6,500 rpm in all gears for getting low times in 0 to 120 mph ?
Originally Posted by Bullseye7
Before buying my '06 C2S, the seller took me out and let me drive it. When we got out of traffic and properly warmed up I brought the car up to about 4,000 rpm before shifting into 3rd gear and then a bit later up to almost 5,000. The seller's eyes opened up like saucers and he told me that "this car has never been driven this hard before. Please slow it down until you own it yourself!"
Transmission is mutually exclusive of engine power so doesn't mater what gear you are in for power curve of engine vs RPM. For fastest acceleration in straight line 0-120 maximize area under power curve. Our trans are geared such that shifting to next gear at redline maximizes that area even with power tapering. So shift at redline for best 0-120. Simple math.
Transmission is mutually exclusive of engine power so doesn't mater what gear you are in for power curve of engine vs RPM. For fastest acceleration in straight line 0-120 maximize area under power curve. Our trans are geared such that shifting to next gear at redline maximizes that area even with power tapering. So shift at redline for best 0-120. Simple math.
Area eh ?
Hmmm.
When driving under the max conditions ....
Anyone know what the RPM drop typically is ?
Say I perfectly shifted at 7500 RPM, when the next gear is ready .... what RPM am I at ?
When to shift? If you have to ask, you need an experienced person going through dozens and dozens of real-life scenarios as they sit next to you in the car.
.
OP: You've been given some good advice throughout the thread, however Phil provided you with wisdom.
The right time to shift is based on the exact situation you find yourself.
Yes, there are guidelines and should be followed as required (or desired) in any given circumstance.
I suspect that for many of us, the dynamic nature of driving + a 911 = pure unadulterated joy and provides the passion necessary to divert our attention solely to driving these special cars, while becoming accomplished at piloting these vehicles safely AND with as big a stupid smile on our faces as is possible in any given circumstance.
Having an experienced driver as your co-pilot who could help create numerous operating scenarios would be invaluable and will provide a great foundation for more practice on your own!
The 997 engine is an amazing piece of engineering in that it can fit in with the daily commuters and putter along at 3-4k rpm but when asked can light up to 6500 and beyond and make mothers clutch their children closer.
The power curve on my 997.1s is at 6500 rpm. You can feel it so clearly in second gear. Beyond that it’s a case of diminishing returns. The 997 engine is an amazing piece of engineering in that it can fit in with the daily commuters and putter along at 3-4k rpm but when asked can light up to 6500 and beyond and make mothers clutch their children closer. I love the Dr. Jekyll and Mr. Hyde character to my car. Enjoy the power every once in a while. It’s fun and the engine is designed to handle it. Why else would you have a 911?
Too bad there is no "like" button on this site! You said it all, vsomoza!!!
That's an interesting and useful (to me anyway) graphic there. Any chance you can tell me where I can find one for the 997.1, or is the gearing all pretty much the same? Even if it is the same, I'd love to have the 997.1 version for my records. Thanks.
07-07-2016, 12:24 PM
