Best RPMs for shifting

I am getting used to my 996. But what is the best RPM to shift from gear to gear?? In my F348, I usually shift between 5-6K RPMs. Is it the same for the P car? Thanks!

6800 rpm

It kind of depends on the driving situation... How much power you need and why. I'd say between 4k and redline in normal for me.

+1 4k to redline max of 4200 until warm though cruising of 2.5-3k is OK on the freeway IMO but why would you...

Sometimes a man just has to downshift.

just not at redline - right

Before the porsche tiptronic when going for fastest acceleration it was around 500 short of redline where speed shifting the revs wouldn't go past redline with me leaving the gas floored between gears. Quick press of clutch and gear change then foot off the side of clutch pedal so lifting the leg wasn't a slowing action. You could feel for the torque in acceleration to drop off then shift. To be technical you can observe where in a dyno sheet the engine starts to level out in torque and horse power and shift there. All to taste in driving needs of speed or just daily shifting.....I'd imagine in town just plugging away with the public just make sure your low rpms don't drop you down below 1,300 or so. Try to remember the life span of an engine is in revolutions with the higher rpms adding more wear and tear. It is good to at least once in a while to do some higher rpms to clean the upper cylinder walls but every day shifting at 5-6k is not required. I could ride my sport bike in 1st gear town and hwy and not go past 3/4's of it's rpm range of 14,000. Clocking higher rpms just isn't needed for common cruising. Not that winding it out isn't good though. Porsche does advise doing hwy runs for extended periods to eliminate moisture and other bad stuff in the oil.

Some guys with their "red" obsession. Here's some red for you to obsess over.

dont go there with me - I am a redhead and i dont like em!!! well, maybe this one wont hurt

http://www.youtube.com/watch?v=eIsdu...eature=related There's a tear in your eye, And I'm wondering why, For it never should be there at all. With such pow'r in your smile, Sure a stone you'd beguile, So there's never a teardrop should fall. When your sweet lilting laughter's Like some fairy song, And your eyes twinkle bright as can be; You should laugh all the while And all other times smile, And now, smile a smile for me. Chorus When Irish eyes are smiling, Sure, 'tis like the morn in Spring. In the lilt of Irish laughter You can hear the angels sing. When Irish hearts are happy, All the world seems bright and gay. And when Irish eyes are smiling, Sure, they steal your heart away. For your smile is a part Of the love in your heart, And it makes even sunshine more bright. Like the linnet's sweet song, Crooning all the day long, Comes your laughter and light. For the springtime of life Is the sweetest of all There is ne'er a real care or regret; And while springtime is ours Throughout all of youth's hours, Let us smile each chance we get.

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"It depends." If you are trying to maximize your fuel economy shift around 2500 to 3000. If you're going for maximum performance, shift where you always keep the engine in it's optimal torque production range (both before the shift and AFTER). If you shift prematurely, you wind up dropping the rpms below the optimum torque production range and then will be lugging the engine a bit until you get the rpms up. Of course, with these higher displacement engines you can get away with a lot more sloppy shifting than in the days of a 2.0 or 2.2, 2.4 litre engine.

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I noticed that her drapes are red...wonder if her carpet is red?

yeah,,,, you are in a car you can just drive... and not have to worry about the perfect shift..... I am still trying to wrap my head around this question.... Shift whenevery the **** you want.... You wanna play speed racer, shift at 6800 you want to play panzy, shift at 2500...... this thread has to be some kind of joke

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Between 7800-8200. -td

Why even shift at all? Just start out in second and let 'er rev. Keep things under 7k and you'll be fine up to over the legal limit most anywhere. These motors play a sweet symphony in the upper Rs!

I've only answered this question for my track cars (GT3 and spec boxster) and it is VERY easy to figure out. Print out a copy of your hp/tq curve to see where the "meat" of the power is and then you can determine the range of rpm that is "best". Then print out a copy of your gear sheet and determine where each shift point will land you in the next gear. Not as easy in the street boxes to hit it perfectly which is why I had the box in my GT3 regeared. Here's a couple pics of what I am talking about (from my Boxster race car). It shows that the best part of the power band (the meat) is roughly from 4250-5800 rpm. The key, is to not only shift where it drops you in the meat of the band (or as close to it) in the next gear but also not using rpm that is on the decline (6000+ in this example where both hp and tq drop sharply). Obviously, the optimal shift point is different in each gear but having a good number for all gears (6K in my example) works for all gears. Alternatively, since I have a shift light setup I also have each gear programmed for each own individual optimal shift point.

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hey hey hey - we'll have none of THAT on this board !!

One thing about that is that you've got more power at 6400rpm than you do at 5000rpm, and a lot more than at 4250. I'm not a racer but wouldn't it make more sense to rev out to redline? The gearing is such that there's no point where power at redline is less than power at the rpm of the next gear. Edit: That was in response to LVDell More edit: Basically, why not use the rpm range where power is in decline if it's still higher than the power available in the next gear?

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It's not about hp that you need to take advantage of, it's the torque. And in my example, it was just approximates for sake of example (for all gears). Im my race car, the optimal shift point is actually just a tick under 6200rpm (not redline) if you want exact numbers. **look at the torque value for 6400 versus 5000**

Okay this is getting into a torque vs. power tangent but I was under the belief that peak power is far more important than peak torque. And I know that math doesn't equal the real world but Power = Force * Velocity, where Force includes all drag forces and acceleration. Shifting at 6000 rpm based on that dyno doesn't even get you to the engine's peak power.

It's not getting off on a tq v hp tangent. It's getting into an explanation of WHAT IS OPTIMAL. Sounds like somebody needs to read up on what hp and tq is FYI.....you need to re-read my last post. Just a tick under 6200 is the optimal shift point not 6K. 6K was a generalization (and technically the just under 6200 statement since it is specific for each gear). The whole point that should be taken away from this discussion is that to maximize acceleration you want to shift where you are able to take advantage of the available torque. Looking at where you will ned up NOT where you are is the key! **if we want to get VERY specific (like has been done on my race cars) then you need to factor what the torque is at the entire rpm range for EVERY GEAR. This is a general discussion not specific so I don't think it is appropriate for this thread**

I understand what torque and hp are and I know how they're related. But acceleration is directly linked to power and you'd be robbing yourself of power by shifting too early. Simply put the power is greater at 6500rpm than it is at the rpm where the shift would come. With closer gears that wouldn't be the case and you'd want to shift earlier.

Apparently you don't understand. I give up.

Well you're not exactly saying anything for me to understand. I'm asking why you would plan your shifts around maintaining optimal torque instead of planning shifts around maintaining optimal power when power is directly related to actual acceleration, not torque. Edit: I completely understand that you plan shifts for where it will put you in the next gear, but I'm saying you should base that on the power curve, and I want to know why you say base it on the torque curve.

Actually hp and torque are DIRECTLY related. Here's a fact to help understand it: You can accelerate as FAST (read "the same") at two different rpm's in the same gear where the TORQUE is the same. Remember, it's a curve not linear. This is why HP can rise while torque remains relatively constant. So don't get caught up in the game of what your hp number is. If we are both accelerating and I shift a few hundred rpm's before redline while you continue on while you lose both torque and hp rapidly, you are losing acceleration (and time) while I have shifted back into the meat of the power power. While you will land in the same range as I did (and dependent on gear you might have a slightly higher hp number, we will have the same torque value and even further, in some gears YOU will have a lower torque value). I don't have time to sit down and put together a matrix of shifting at redline versus shifting at under 6200 (or whatever each gears optimal range is) right now as I have to finish writing a test to give in a couple hours. I have done this extensively with my engineer for my race cars so trust me the values are optimal. FYI....here's a formula to play with different numbers to see the relationship HP = TQ*RPM/5252

Made perfect sense here Dell. the point I get is you when you shift into the next gear you want to be in the "meat" again so you don't have to wait for the curve to match speed again. and btw, was a good explanation.

Very welcome. It's VERY CLEAR if you have the time to put together a shift point matrix for various rpm's.

do we really care about this thread anymore apart from the redheads...... those pics woke me up.

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This is just not true. An ap1 S2000 has the same torque at 3500rpm as it does at 8500rpm. They will not be accelerating the same at 3500/8500, it will be accelerating much much harder at 8500rpm because the power is over twice as high at 8500 than it is at 3500. Just look at an LS2's power curve, if you base shift points on torque alone you'll be shifting at something like 5000-5500 rpm, well below the 6000rpm power peak. Hell, an LS2 has the same torque at 2300rpm as it does at 6000, definitely won't be pulling as hard at 2300. Except I will have higher power in the last few hundred rpm than you after you shift, and when I do shift I will come into the next gear at higher rpm and power. That power will translate to more acceleration. This is a general statement since I don't know the specifics for your car, but if you were shifting from 4250-5800, the meat of your torque curve, and I was shifting based on the meat of the power curve I would be significantly faster (I know you're not shifting at 5800). I'm not saying your shift points are wrong, I'm just asking about the reasoning. Edit: I understand completely the torque/power relationship. Completely. I also understand that acceleration = power / (mass*velocity) (Not counting for drag forces there but it doesn't change the acceleration/power relationship, just the coefficients). Edit 2: I also want to make it very clear that I know you're timing shifts for where you'll be in the next gear; you're just doing it based on torque and I'd do it based on power.

[Image-only post; no author-written text. Original image references:] https://rennlist.com/forums/images/smilies/popcorn.gif https://rennlist.com/forums/images/smilies/popcorn.gif https://rennlist.com/forums/images/smilies/popcorn.gif

Dell, While I can see your logic in the rpm range you've selected, it seems that the gear ratios of the car are not being factored in for the true "optimum" shift points. To check your numbers, you may want to use some of the various shift point calculators that use mathematical formulas that factor gear ratio and hp at various RPMs. I would expect you will find that you are shifting too early and that you would actually need to hold each gear a little longer to get the maximum benefit.

yup. shift at redline. don't short shift. it's not just engine power, but gears are obviously involved as well (multiplier) shifting anything below 3k RPM during street driving is kinda weird. it's almost like lugging the engine. I typically hit 4-5K RPM because it not only feels best, but also sounds best.

It really depends on the engine and gearing. Some engines will run out 1500rpm past their peak power so it only makes sense to redline the first few gears, then you'll want to keep the shifts focused around the peak as the ratios tighten up for the higher gears. I'm bored and was just looking at some different power curves and it was the Audi 1.8T that peaked a little over 5000 but steadily dropped to redline at 7k. An engine like that you'd shift somewhere around 5500 to 4500 going from 5th to 6th (numbers from memory, saw it about half an hour ago). That's a bizarre engine, you figure they'd tune it for a little more power at the high end if they were going to have the redline that high. I'm a mechanical engineer working on a job doing scheduling. This is such a bottled-up energy outlet for me I apologize if I've been a little overzealous.

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As I said, this is NOT exact and I have tried to purposely not go into mind numbing detail. Those exact numbers you are looking for have been figured out based on the hp/tq curve and gearing and are programmed into my AIM system in the race car for optimal shift points for each and every gear. For obvious reasons I am not posting those values here. Sure, gears factored into the calculation would be nice as well but this is the 996 forum not the racing forum. That is a discussion I have no desire to get into. Just search the racing forum and you'll see why I don't participate in those discussions. If y'all want to shift at redline, be my guess. I'll shift where it's optimal. ********* Dave, I'm sorry you don't seem to understand fully the relationship between torque and horsepower. That's ok. I'm done with this conversation. No offense, I have to get to work though. Please do some more reading on the relationship.

I though Dell's points showed incredible thought and backed with data and real life track experience...any of you think you can pass him at the track, feel free to try... he knows what he is doing and works on these things to tweak out parts of seconds/lap times...I for one am impressed at how deep he gets into these things and its not just on shifting... you can ask him about nearly any subject from alignment to braking zones and tail pipes to iPod setting... Dell is a NO BS Get it done kind os P-Car owner!!

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I really don't appreciate the forced condescension. Edit: I'll retract that because it's nasty. Just know that I completely and fully understand torque, work, power, acceleration and their relationships. Edit: I know, that's why I was trying to see why he planned shifts the way he does. Having seen how much he knows it bothered me to see something he said disagree with what I know.

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So then I think it is fair to say that when you say optimal, you mean optimal for you but not scientifically optimal. Run the specs of 996 or 996 GT3 through four or five shift calculators and that might optimize the thinking here.

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Don't be so damn sensitive. Geez. There was no condescension. I guess a smiley would have helped? I literally meant that I wish you knew more about the discussion so I didn't have to keep explaining it. That's all. I would have explained further but I am out of time. Heck, I'm typing this is the middle of giving a test. Gotta love lecture halls with internet terminals Like I said, read up on it. That's how I learned about this stuff. My example that I was talking about was for the 2.5L boxster but the same concept applies to all the cars (normally aspirated). Back to the topic, red heads

someone say red heads? like this?

Did she drop something...?

Now we're back on track!

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Proper cam. lifters, rods and pistons and she'll be good.

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Okay fair enough it came across as condescension, but I think it comes across like that because you're assuming I don't know what I'm talking about when it comes to torque and power--I do, very well, from school, work and engine specific reading. And I think you're mistaken when it comes to the torque, power and acceleration relation. You're thinking torque is proportional to acceleration but it's power--it's easiest to think of it like this (I dunno what you've done with kinetics but I'll make it quick in case you haven't dealt with it): Power is the amount of work you do per an amount of time (work is energy) so you get power = energy / second. The kinetic energy of an object is based on the mass and velocity (1/2mv^2). So you have power, which is rate of change of energy, and velocity, which is energy. Simply put, power is the rate of change of velocity, which is acceleration. That's why it's throwing me off when you say you want to keep it in the meaty torque band and not the meaty power band. Now, for the torque-power relation. Torque is the torsion force the engine applies at any given speed, work is force times the distance that force is applied (rotational work in this case), and power is how fast you can do that work. Power is 100% dependent on the torque the engine produces (P=T*rpm/5252 like you said), yes, but power is really the value you want to think about when it comes to acceleration; torque is for pulling stumps. This is longer than I wanted and probably confused but I'm bored and tend to ramble. I found this, which does a much better explanation of what's going on than I did that you can read later if you like: http://www.fjr1300.info/misc/torque-power.html (Myths 3 and 4) Of note is this bit in there: What he's saying there is that the wheel torque is higher in the lower gear at the same speed in the higher gear even though the engine torque is lower. Edit: Again Dell I'm not knocking your setup and don't mean to be since I bet it's setup just right for the track, it's just that there's a lot of weird information on torque/power and I like clearing it up since it's such a confusing topic.

Here is my take. I am sure everybody will appreciate my insight ha ha. You can have torque and hp whoopy. What you need is a good engine to start with right. I don't think some know whats going on at higher rpms. I wont exactly say Dell is right....because you'll quit reading First point is hydrolic lifters. I don't know if Dell has been in a life of radical rpm cams or not but hydrolic lifters start dropping out at higher rpms specificly around 6-7k. They are not a contender at 8k for sure. Roller cams and non hydrolic lifters are needed for real responses at higher rpms. In laymen term shiza just starts floating in the high rpms with hydrolic lifters even with stronger valve spring. Secondly numbers my foot Figure torque as how hard the power can pull you from what ever speed to higher and HP as staying power. Turdly when applying power and setting up the suspension you want availability of working space to keep yourself so that there is HOPEFULLY (for a novice) always more higher rpms available in which ever gear you are in during a turn to keep the suspension settled. When things get squirly in a turn it IS NOT the time to change gears, brake or let off the gas. That is unless you are not snatching gears correctly and at the highest possible speed of the turn. So change gears when ever wanted and race Dell as much as you like and my bets on Dell whopping your tails Dell races and knows while some of us are thinking straight line and numbers.

Pheh! I have a break between classes so I can play for a bit Dave, It sounds like there is a little bit of truth in both angles we are attacking this. While I agree that hp is what I want on the straights (high speed sections) it's torque that I value in the mid speed sections. For a street car that is relatively heavy with a stock box we need all that torque we can get to put that hp down. If I had a high revving lightweight car, no question would I want hp. My brain hurts right now....are we getting closer together?

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Tell your brain I'm sorry, and I hope this helps: The thing that made the lightbulb first click in my head was thinking like this, "Torque is how the engine makes power, power is what you feel in the seat of your pants." For a sportscar all you really need to care about is the shape of the power curve and the peak power, everything else is just extra to confuse you, like if you did a dyno run and they gave you a power, torque and conn. rod #3 tangential force chart. So just scrap torque, forget about it, and when somebody says they've got lots of torque just pretend they said "I've got good low-mid range power" and leave it at that.

DOH !! no longer safe for work

God I'm glad thats over with........

Truce...

Thanks for everyone's input. I will see how my car responds to shifting between 4K-5k RPMs.

I just take it easy around the neighborhood. Works for me and the neighbors. Especially the little kids.

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With all those freckles it is a good bet.

Wow...3 years later and the redhead is still getting attention!

This thread is further proof that anything on RL can become a pecker contest.

What oil is best?? What weight? Does temperature matter?

Depends how long you want your engine to last ! While there is some satisfaction to go to 7k when oil is up to temp ...you are going to get a lot of thrills at 5-6k and have a hard time finding public roads where it makes much difference beyond that. Likewise these engines don't like to be driven under 3k all the time ( or so they say). Will engine last longer with fewer excursions to redline ? Not sure .. But seems to make sense ...

Mostly common sense: Don't lug it Don't rev the **** out of it when it is cold Vary your RPMs a bit A driver who is in tune with his vehicle knows where to shift it as it feels right. On my 2 lane road commute my tach is between 2-3K most of the way with the odd blip up to around 4k here and there.

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Yup, agree! The voice of common driving sense! I also subscribe to Dell's torque optimization theory .... 3 yrs later. Good thread!