So, there the scenario! you got it. we have said many times, forget about turns, turn ins , transitions, etc etc, ONLY straigth line performance.

I dont think you know what your point was. I know what you are saying. you are talking about short shifting through turns.
Now, HERE is your CONFUSION. I hope you understand WHY you are confused. I dont know why im going to help you , but I am. probably because it is so sad you sit back, spew errors and just say, "your wrong" for your defense. Anyway, here it is. The power falls off up top, but its still at a level, where a shift would produce LESS torque to the wheels. This is why it pays to shift at or even sometimes, beyond redline. factory redline is usually safe, and sure, you are working the engine more than if you short shifting, but in racing, as I said, you are using the equipent to the max to go as fast as you possibly can (qual or a tight race), or you are just driving around for fun.
If you want to win or post a top time, you need to shift, usually at redline, unless your engine has a HP curve that doesnt pay to redline, as that does exist. the 996 isnt one of them.

my comments, as much as you want to poke fun at them or my wordy data enclosed responses, it doesnt matter if you run a 996, ferrari, 928 or a VW bug, if you have a peaky HP curve, you shift at redline to maximize acceleration.
Ive said it once Ill say it again.
acceleration =power/(mass x velocity) this means , at any vehicle speed, acceleration is directly proportional to power. (or as greg said and posted, torque at the wheels.)

Im beginning to think this is all a mistake. Now when I race VR, he will be taching out the 944 and give me more of a run for my money. :)



that sounds interesting, but in a 928, your engine will overheat without a thermostat. :) It does it because without it, the dual function of the t-stat of restricting flow and directing flow, is removed. the directing flow part, being removed, allows for no flow and the engine overheats.


Do you think anyone wants your opinion now, based on your inability to even read the charts and give us the gears where you would want or not want to short shift. YOU clearly said, 4-5th gear when in actuality, the torque, power or whatever , was less post shift if you did.
AGAIN, we are not talking about transition turns and cornering , traction areas of the track. ONLY straight line acceleration.

Now, you have a copy of what you said. Care to recant? How about this. give me your reason and I promise not to respond at all. That way , if it is some revelation, we can all benefit, and you dont have to listen to my critisism.
So, what is the reason you would want to short shift on a straight based on the 996 HP curves presented here?
If not, would someone please send a dyno chart posted on this thread to VR Dave, so we can hear this revolutionary reason? I guarantee, AGAIN, I will not post again in regards to any post VR makes from this point further! thats a racer promise! :)

Please tell. Im really curious. seriously!

with this gear box set up. Ill put the % rpm shifts below:
1st gear 3.818
2nd gear 2.20 57%
3rd gear 1.516 68%
4th gear 1.216 80%
5th gear 1.024 84%
6th gear 0.841 83%
Final drive 3.444)

what this means, is that for each shift of a gear, the resultant RPM is x% of the prior gear RPM.

look at that chart that shows rear wheel torque, and then use the 3.44 rear end multiplyer to see how much torque you lose by short shifting. in some cases, over 300ft-lbs lost by a short shift , as measured at the rear wheels. :eek:

A quick thanks to all those who sent me emails overnight. I hope my reply this morning answered your questions in the context of this discussion as well as Brinkley's video in the other thread.









Professional Racing and Driving Coach

Just for discussion's sake... with this engine (dyno below) I shifted the car around 5500 based on "feel" - this engine didn't pull past 6000 very hard and felt stronger in the next gear at lower RPM instead. I didn't need the dyno graph to realize the power drop as it was easy to feel. The new engine is obviously more fun - it's an x51! :)

I usually try to shift my little 3.4 (270rwhp) at 7k although it will rev to 7400. It all depends on the circumstances and specific corner....

I definiitely short shift at a specific corners where too much torque could push me over the edge. Backside of Cotton Corner's at Buttonwillow comes to mind as it's a off camber, downhill turn into a short straight that has sent many cars off into the desert or worse. Another example would be T8 at Willow Springs, a high speed sweeper leading to a short straight and brake zone. I shift a touch early into 6th approacing that turn as my max grip of 1.6-7 G's is easily obtained in the taller gear at the lower RPM's. Conversely, I take it to 7200 or more in 4 & 5 coming out onto the banking at Cal Speedway where you absolutely need to stay up in the power band to make it around T1 & 2 at your max speed. So my $.02 is that your shift points are relative to the track and the turns you're facing. If I have a big lead or I'm way behind I take it easy to save the mechanicals and tires. But what the hell do I know.....

The best way of determining shift points is to use the completion backwards principle. Starting from the point of maximum velocity just before braking, compare speed and gear and minimize back in reverse order the QUANITY of shifts above the torque curve you wish to employ.

so, now after this discussion, you can now see how much time you are leaving on the table. If you shift your engine at 5500, from 3-4th gear, the resultant rpm puts you at 4400rpm post shift. thats 235hp down to 200hp. shifting later, gives you a 250hp shift ending up at 235hp. at first glance, thats a 20hp diff of average HP. But, that doesnt tell the story. you shift at 7200rpm , near 250hpand you drop down to 235hp. (otherwise you shift at 235hp and drop to 200hp. This means, you are really down near 50HP . Youre not the first to be fooled by your butt dyno. :)

Now, your graph makes it a lot more complicated, because of the dip. this is where some area under the curve work, or HP-seconds (J) needs to be taken into consideration. certainly the shifting early is killing your performance by 20 to 50hp , without question.. I could give you more accurate differences if you really think you need it.

my advice. fix that dip in the curve, if possible. shift at redline for best straight line acceleration.

Edit: a summary of the above, is that by shifting at 5500rpm, you are almost 2 full gears down post shift, and thats a rear wheel torque difference of nearly 50% !!! Its one thing to see, feel and hear engine torque loss at the high rpm, its quite another to incorporate gearing and power (multiplied torque) and make a correct gear selection opinion.

The "best way"?? I dont know really about that, but the easiest, (which I think is the best) is to just what we are talking about here. just maximize HP as best you can by getting the greatest time spent in the highest HP range, and you maximize hp, regardless of top speeds on a track. usually, as we see with the 3.6L 996, this means shifting at near redline. (whenever possible, and you wont be upsetting the car in a turn, transition, etc.)

The discussion really is about straightline acceleration. maximizing acceleration of the engine when you can. sure, a short shift in areas like you say, similar to coming out of the corkscrew for some cars, and certainly coming out of the "wart" at thunderhill, where redline WOT, might just not be possible. (thunderhill turn 5 yes, need to short shift, corkscrew, not anymore)

anyway, its a discussion if the top end of the RPM curves are noise, or power. by definition the curves show power, so this is very easy to see for the semi trained eye, with access to a set of gear spacing %.

Please send me this information if you recieved it via PM. I will not discuss on this list. I am curious what we are missing here if we are are incorrect in our calculations. My guess is that short shifting from VR Dave's perspective, is related to traction or car control issues at certain parts of the track. It would be a revelation, if any straight line acceleration hypothesis detailed out in our discussion, can really be challenged.

Mark

I've decided that Mark and Dave are like North and South Korea. They both speak the same language but are not having any sort of intelligible conversation. There's aspects of both positions that are correct but neither seems willing to concede that anything the other says has any merit. It's a shame really because there's some very good racing technique information that people could draw from the contributions of both guys but there's so much crap to wade through it's not really worth finding the valuable information. I think jrgordonsenior sums it up pretty well though.

Funny. yes, racers all will have different take on style and trade offs for maximizing performance. Its the way of sports. I have a 1000 things I would do different that dave on the track and have logical, thought out reasons for them, and IM sure, dave would have the same. so many trade offs in all areas, and in the end, I respect most all of them and certanly would try them all as well. HOWEVER, there is only ONE thing I disagree with completely .
That is, when an engine makes a hp and has a HP curve, you can easily use that hp curve (based on gear spacing) to determine shift points. I really dont think this is debateable. really, and so far, in the 100s of pages of this stuff, he has never put down one single solitary bit of information to the contrary, other than to say I am "wrong". So, he fired off some PMs and emails this AM to explain his thoughts, and Im really curious as to what they would be. :rolleyes: Seriously, if you make less hp after a gear shift, you are accelerating at a LESSER rate. PERIOD. And I have to say it again, because it is glazed over, this is not applicable during traction or handling related issues on the track. ONLY straight line performance. He says he shifts early due to that engine rpm area just being "noise". I say, that "noise" is greater hp , thus greater ability to accelerate even if HP is rapidly falling off . (if the falling off is greater than the post shift HP.) easy to prove in theory and reality. you cant fool Newton! many have tried! :)

I think Gordon did sum it up perfectly and its what we have been saying all along. Most of us anyway. shift at redline, unless you cant due to traction or upsetting the car, so why not save the engine if you cant use the power. totally agree with that and practice that myself.

VR Dave Scott said:

"...The 996 street motor generally makes more noise than power at the very top end of the range. I have spent some seat time in Spec 996 cars, and I find that my times are better if I generally upshift slightly short of redline. Plus, this is a bit easier on the equipment."

What you call "crap" is--from me at least--my total unwillingness to post the proprietary data of my clients, and thus sell out one of their competitive advantages. Despite Mark's 90,000 word avalanches, my statement, which he has bolded and posted many times along with my name, is still true. Garrett's graph shows that power falls off pretty dramatically just before redline with this particular street 996 motor...and it is simply slower to try to use a falling power curve rather than a rising one.

Again, in what we refer to as the real world, things are often different than in what folks can Google. So if you want to call that "crap", knock yourself out. I have nothing to prove here, whereas Mark apparently does. Folks here can make up their own minds.








Professional Racing and Driving Coach

So, Dave,
Im still really puzzeled. you have kept us in the dark regarding your revelations of how to bend the laws of physics, so just clear up one thing that you already said, and was corrected by many of those participating in this thread.

The reason I bring this up, is that if we find our what part of the chart you are looking at, maybe we can figure out what you mean. I know you are not a dummy, but sometimes your ideas and thought process is not very clear. So, im sure you have a good reason for saying what you say below. in otherwords, clearly, beyond a doubt, you DO need to shift at redline to take advantage of the available HP of the 996 engine. why did you say you dont?

curious......
..>>>>>>>>>>>>>>>>>>>>>
VR Dave Scott, said:
So wait....this chart seems to show that--GASP!--you don't really need to upshift at redline with this motor. But...but...but...how could that be? 42,000 defensive words of protest in 2 separate threads seem to indicate it is impossible! Zut alors!!!
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>




Now, I also want to hear from the 9 soles that also think that the upper rpm activity in a 996 engine is just "noise" and it pays to short shift. Why do you think this, when the data would suggest otherwise? Do you just think its not a big deal to lose 20-40hp for a second or two?
that saving the engine from extra abuse for that short of a gain, is not worth it.
If so, then the fastest possible lap time, really isnt that important to you.

Im really curious, because I certainly understand the other 10+ listers that will follow VR off a cliff, thats just natures way. some of us, just have blind faith. :)


One thing for sure, this could help us on race day (those of us that dont believe VR), in that there are 20 racers that follow him blindly, or dont understand the concepts, so if 50% of the racers /followers, are out here, thats 5 guys that will be at a distinct disadvantage when it comes to race day if they are already close on power! They will probably be blaminng their corner balancing or their wing settings when they lose! :)

[QUOTE=JustinL;8285965]Here you go. At 7000RPM you have to make the decision as to rev up or shift. These options are highlighted in bold.

QUOTE]

I rest my case. Korea will never be reunited. Have fun bickering fellas...

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