S**t is the 02 fast...And an acceleration ?

I have been babying my 02 for the past few months. Breaking the car in, shifting at 5000 rpm etc. But, tonight, I turned the mileage corner and pushed the car. Every gear was sensational. I came from an M5 which was just a beast on the highway and had mountains of torque. Have to say, I am more impressed with the 996. Great off the line and surprisingly awesome on the highway. Handling speaks for itself! Question: At what RPM should I shift out of 1st and 2nd to achieve maximum acceleration? At the red line? Thanks

Uh....would the answer be "redline" each shift?

Glad to see you are enjoying your car!! Word of caution. The P-car is not a dragster. The combination of rear weight bias and heavy tires make those tires grip the road, and you can easily butn your clutch.

[quote]Originally posted by smjjpres: <strong>Question: At what RPM should I shift out of 1st and 2nd to achieve maximum acceleration? At the red line?</strong><hr></blockquote> Maximum acceleration is not achieved by shifting at redline. Rather, the optimal shift point is just as the torque is about to fall off. Torque decreases substantially well before redline. Once the torque decreases, the car will pull much less notwithstanding the higher revs. The key to quick acceleration is to keep the engine in the maximum torgue range, with the maximum pull. A stock 996 achieves maximum torque between 3500-4500 RPMs (<a href="http://www2.us.porsche.com/national/models/911/c2/technicaldata/default.htm" target="_blank">See 996 Specifications</a>). Therefore, if the goal is to maximize acceleration, the optimal shift point is apporximately 4500 RPMs (perhaps a tad higher). Craig (L.A.)

To get best acceleration from a car the gear should be held until torque at the wheels has dropped below the level which would be achieved at the current road speed in the next higher gear -&gt; the optimal shift points depend on the gear ratios and the shape of the torque curve. For example, shifting 2nd -&gt; 3rd would typically mean a ratio about 35% higher, 3rd -&gt; 4th about 25%, for most "high performance" cars torque holds up pretty well at higher rpm so it would be unusual to come across a high performance road car that would benefit from shifting earlier than just before the limiter cuts in.

I don't think shifts at redline in THIS car give max acceleration. I have found that shifts around 4-5k rpm do it well. I don't have it spec'd to detail because I have to keep my eyes on the road as well as the tach. My old Boxster worked better with the at or near redline technique.

I can assure you that at the start of a race, if you short shift the car the entire field will stream past. As JohnM indicates, the torque is multiplied by the gear ratio so, yes, you want to shift in a manner that utilizes the maximum torque available to accelerate the mass of the vehicle. As you can tell by the seat of your pants, it is almost always in a lower gear. If you go to Club Race, ask anyone on the grid if when the green flag falls they will be shifting at anything other than redline (or beyond &lt;G&gt .

Near the rev limiter before next shift so tach needle would stay in the comfort zone of 4k+ rpm where the trq will be on next shift. Regards. Mike

To get peak performance, you should shift at the point where the next gear will place the engine speed at the point where peak torque is made. Shifting at the redline may work for some gears, and not others.

[quote]Originally posted by Jim Sloves: [QB]...I have found that shifts around 4-5k rpm do it well...QB]<hr></blockquote> That can't be true. If you shift at 4000, next gear, you'll be at 3000-3500 and you'll be dragging along very slowly. Like others already said, when you shift close to a red line, you'll be way closer to your torque peak at next (bigger) gear. Take a look at any race car (F1, GT, whatever), there's no one there who shifts lower that the redline. Also, the fact that torque drops after the peak... That's true but it's (torque) still more that what it will be after the shift (if the rpm's are around 3k), plus, the fact that you have higher gear at that point, so you need more torque (to accelerate as fast as you did before the gear change) anyway. Hopefully, someone understands what I mean.

isn't the idea of track cars to take advantage of gearing? this is why the HP is at max rpms...so that you stay in gears longer, putting the power down? this is definitely true of F1 cars. it seems muddled in variocam plus 911s, but still makes more sense, in all out acceleration, to take advantage of gearing and stay in each gear as long as possible for fastest forward propulsion?

Seems it might be worth explaining the process of shift point selection in a little more detail To do the job properly it is necessary to know the gear ratios and torque versus rpm curve for the car. To decide the best point to shift make an initial guess (e.g. 500rpm below the redline), look up the torque at that point on the torque curve and multiply it by the gear ratio - that gives the transmission's torque output at that engine speed. Then use the gear ratios to work out the revs that would result in the next highest gear if a shift were to happen, read the figure for that rpm from the torque curve, and multiply by the ratio of that next gear - that gives the transmission's torque output after a shift at the initial point chosen. If the torque figure is higher than before the shift the shift point is too late, so repeat the process for a slightly earlier shift point. If the figure is lower, repeat the process for a higher shift point (but stop when you reach the redline ). A tedious series of repetition will then yield the optimum shift points for each gear. That is really only a first approximation to doing the job accurately, as the shape of the torque curve (how quickly it rises and falls, positions of dips/peaks in it) can mean that the ideal shift point would be a little lower or higher than indicated by the simple method above. Despite this, in the lowest gears the drop in ratio is so large that it is always best to shift just before the limiter cuts in. However, at the higher ratios, and particularly if you have a lot of ratios in the transmission (7 is typical in an F1 car these days, for example) it is worth calculating the shift points accurately (especially when the transmision control system can ensure that is exactly where the engine will shift every time ). Most professional race teams will have software to help them choose the gear ratios and shift points for each circuit.

If you're too busy doing the calculations for eache gear redline is still the "best" quick measure....especially for people who can't multiply or divide! <img src="graemlins/c.gif" border="0" alt="[ouch]" /> <img src="graemlins/c.gif" border="0" alt="[ouch]" />

Unless you have a "shift light" that goes on at or close to redline, in the real world you will be shifting below redline. Otherwise the chances of you hitting the rev limiter increase with the consequent seconds lost from that and the additional seconds lost as the engine recovers in "safe mode". Anyway, as I stated before, the P-car is not a dragster. A host of cars, like the 'vette, and even the lowly M3 (heh-heh ) will beat it in a straight line. You want to see it perform? Take it to the track. In no time you will be in the so called "red group", the car is just that good.

I would say that anyone with a tip should know the answer. If you are driving a tip and you press it to the floor, the tip should change gears at the optimum rpm. So here you go: any guys driving a tip with the correct answers? What are the rpm's for each gear?

Flynn, You're right. I spaced that one. I meant that when I upshift I don't let the revs fall below 4000 and often let them bottom out a bit higher when I'm driving and shifting aggressively.

I keep reading on all the forums that the M3 is quicker than the 996 in a straight line. I know what the magazines claim. Varrying results can put the cars at par in a straight 0-60 shot. After spending much time in both, IMO a pre 2002 996 would lose the 0-60 battle, and a 2002 + would win the battle. I find the 02 so much more responsvie than the 3.4l car. The torque/pull is a night and day difference. I believe that Porsche dropped the 0-100 km/h times by 0.2 seconds too??? I have yet to have the opportunity to race an M3 off the line. When I do, I am sure I will win!!!!!!!!!!!

I know people have beaten E46 M3's with the 3.4 and same can be said the other way too. The 0.2-0.3 second difference(0-60) is so small that it comes down to driver experience. Regards. Mike

JohnM is right. You can calcualte the shift points based on your dyno results and gear ratios. <a href="http://www.prestage.com/carmath/dynochart.asp" target="_blank">This site </a> can do that for you if you have dynoed your car. If you have, post the results as I have not seen dyno results for the 2002 yet.

P.S. I ran the dyno results for my Viper into the program and suprise, it suggested shifting at my 6000 rpm redline....

Great site, Jeff! I plugged in the numbers for my 993 and, surprise surprise, best shift point for every gear was at the redline. This is usually the case for naturally aspirated cars, only get different results if the engine makes peak torque fairly low and torque drops away as revs rise (get this characteristic from most diesels and some turbo engines, depending on how the boost is managed).

....and the circle is complete

Interesting website...but... It doesn't ask for the final drive ratio?? What do I do with my individual gear ratios to get it to include the final drive ratio? multiply? (First gear is 3.5, 2nd is 2.059, 3rd 1.4, etc) I had the car dyno'ed and I plugged in all the numbers... 1st to 2nd it indicates that I should be shifting at 3000rpm??? All other shifts it shows 6000rpm (last data point I had, so redline). To give you a rough idea..I plugged in: 3k = 125 4k = 181 5k = 244 5.4k= 248 (peak, just about) 6k = 227 And I entered data every 200 rpm. It gave me this (among other info): Best shift point for the 1-2 shift is 3000 with a LOSS of 438 Lb/Ft of torque. Best shift point for the 2-3 shift is 6000 with a LOSS of 214 Lb/Ft of torque. Best shift point for the 3-4 shift is 6000 with a LOSS of 98 Lb/Ft of torque. Best shift point for the 4-5 shift is 6000 with a LOSS of 98 Lb/Ft of torque. So either something is messed in the little program...or I entered something wrong.. It's no big deal, I'm just curious.

I wondered about this at first but then realized the final gear ratio does not matter as it is the same for all gears and doesn't effect the comparison of torque between gears. So don't enter the the rear end ratio. I briefly entered your data and it suggested shifting at 6200(!) for a gain of 340 ft-lb from 1st to 2nd so check your numbers.

Played around today and really paid attention to the tach. You guys are right: close to or maybe at redline is it. Definitely higher than I previously posted. <img src="graemlins/c.gif" border="0" alt="[ouch]" />

One thing I have to say that for those who track are push at/near redline for maximum trq advantages a good way of not passing redline and get that power loss is place a yellow arrow sticky at around 500 rpm before redline so that way when the red needle hits the yellow sticker it's time to shift. It's a cheap way to do it versus getting one of those shift lite gadgets. I noticed on earlier P-cars they are able to turn the guages where redline is facing 12 o'clock so much easier to see but 996's cannot do that. Give it a try with the yellow sticky pointer-works for me. Regards. Mike