At what rpm should I aim to be in the next gear to achieve maximum acceleration?
I read somewhere that you should shift such that in the next gear your engine will be at the torque peak. So, with this Audi it's at around 2600rpms.
But that's completely ignoring the horsepower curve?! Is horsepower irrelevant for acceleration or what?
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also posting the original picture so you can edit it and show me what rpms should I aim for
The point where max torque and max hp meet
at redline? when you shift later, even if you're at a lower torque/hp then max, you're still at a gearing disadvantage by shifting up.
ex
Car A makes 100lb-ft torque at 5000rpm.
Car B makes 1000lb-ft at 5000rpm.
assuming the gear ratios are the same between both cars,
car A accelerates in first gear.
for the sake of simplicity, first gear is a 1:20 ratio, meaning for every 1lb-ft of torque it sees, it multiplies that by 20.
Car B accelerates in 4th gear which is a 1:1 ratio.
this means that Car A will see 2000lb-ft of torque at the wheels, while Car B will see 1000lb-ft of torque at the wheels despite it having 10x more torque to start off with.
same thing applies with different gears in the same car, if your peak torque is 200lb-ft, and redline is only 150lb-ft, shifting into a higher gear means less torque at the wheels, even though you're shifting to a point in the powerband that has more torque.
This is wrong.
OP its extremely complicated. Simple answer is, the manufacturer has done the maths for you and you should shift at the redline for maximum acceleration.
Read this. practicalmotoring.com.au/car-advice/when-should-you-change-gear-for-maximum-acceleration/
5252 RPM?
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tl;dw redline
Peak torque is the maximum specific work.
i.e. most work per engine cycle
Peak power is maximum work per unit of time.
i.e. most work per minute
You should shift at peak power because that's when the engine is doing the most work.
The clue is in the name:
MAXIMUM POWER
do you know what gears are or what they do?
Torque and speed manipulation.
The power is still the same regardless of gearing.
You should shift after peak power so you have the broadest range of power in your usuable powerband
I have actually read the whole thing, and it says that what you say is bullshit.
>you need to change gear such that maximum average torque is delivered to the wheels with consideration to gearing, which means a change up when the torque you can deliver in the higher gear exceeds that of the gear you’re in now. And to achieve that, if you want a basic rule of thumb, sports cars are generally designed so that if you change up close to redline you’ll maximise acceleration.
the shift near redline rule only applies to sportscars
ITT: people who don't know what they're talking about
obviously you cannot read
I just shift at 7
no, you were too lazy to actually read it
I don't drive a sportscar. Sportscars are usually gasoline powered with large engine displacement.
A turbodiese is a completely different story. There is no reason to redline a turbodiesel, actually it's contraproductive as the torque peak is set very low
you want to shift when in the next gear you will be at maximum torque
>dd turbo diesel truck
>from 35000rpm onwards literally gutless, below 2000rpm also gutless
>engine feels like just pumping air and not burning fuel from 4k to 5k
I hate diesels
No! Peak torque is a meme.
Spin that cunt out to maximum power rpm
>The power is still the same regardless of gearing.
At the flywheel, yes. Torque at the wheels is the torque at the fly after it is modified by the gear ratio of your current gear.
It depends entirely on your car, its engine and its gearbox. For most cars however, first, second and often third should be taken up to redline.
More complicated explanation: you should shift when the percentage difference between peak torque and current torque exceeds the percentage difference between the ratio of your current gear and the next gear.
For example, assume you have a car with an engine that has its redline at 8k, it makes peak torque at 5k and after which the torque curves downwards in a linear fashion until it reaches 65% of its peak torque at redline. Let's also assume the gearing is as follows 3.150 > 1.950 > 1.325 > 1.175 > 0.975.
There is a reduction in ratio between 1st (3.150) and 2nd (1.950) of 38.1%, which also means torque at the wheels would be 38.1% less in 2nd than in 1st at a given RPM. What this means is that the wheel torque in 1st at any point in the rev range past peak torque will be higher than the wheel torque in 2nd gear if in the peak torque range, because the difference between torque at its peak and at redline is smaller than the difference between the two gear ratios. Therefore 1st would be taken right up to redline for the fastest acceleration.
The difference between 2nd (1.950) and 3rd (1.325) is 32.05%, which is slightly below the difference between peak torque and redline torque, so you'd seek to shift just below the redline.
And so it follows on like that. You work it out for each gear.
>At the flywheel, yes. Torque at the wheels is the torque at the fly after it is modified by the gear ratio of your current gear.
spastic
post gear ratio
It's easy. Yellow area limited on top by wheel power curve (definite integral) should as big as possible. In this case you should shift at @4200-4300 RPMs
>At what rpm should I aim to be in the next gear to achieve maximum acceleration?
Shift at maximum power.
Try again, bud.
True, but you can't argue with TDI fags and their highly calibrated butt dynos. I own a TDI, have timed my pulls, and consistently get faster 0-whatever times by shifting at peak power, not lower.
Why are you refuting "power is the same regardless of gearing" by talking about torque instead of power? Other than that, you're explanation is pretty sound. You usually want to shift at redline unless the next gear ratio is close, and torque drops off enough to make wheel torque higher in the next gear.
Yup, for 99% of cars.
It doesn't matter.
You'll always be slow.
You'll never be able to compete.
Don't look for an actual number, just feel it. Unless you're racing and every millisecond counts you won't notice a difference.
>Why are you refuting "power is the same regardless of gearing" by talking about torque instead of power?
Don't mind me, just failed to read properly.
Just after the power peak if your gearing is optimized. If your gearing is not optimized you may get faster times by running to the rev limiter
IT DEPENDS ON THE DIFFERENCE IN GEAR RATIOS.
Gear ratios multiply torque... It's generally best to rev as far as she'll go.
Get a 1000cc sport bike and do low 3s 0-60s
>Get a 1000cc sport bike and do low 7s 0-60s
FTFY
Most people who ride 1000cc sport bikes can't come anywhere near maximizing the performance of the bike in a straight line let alone a corner.
Do you have any idea how hard it is to do a consistent max performance launch on a literbike? Most people with traction control equipped CARS can't manage a magazine/manufacturer claimed 0-60 time, the average squid tard on his GSXR-1000 would flip the fucking thing over if he tried to launch it as hard as the test rider did for the manufacturer, and he knows that, so he bogs it on every launch out of fear.
You want to ignore the torque curve the torque at the wheels is the engine power/wheel speed (Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488) not engine speed so you want to be maximizing power from the engine as this will always give you more torque at the driven wheels.
So looking at your graph assuming 225/45R18s at 100kph you are looking at around 800rpm for the wheels you have 1.3 times more torque at the wheels at peek power than at peek torque.
Between 4.2k and 4.3k in that case.
Just before that huge drop in power.
You realize engine RPMs plummet after you shift right? It's where you end up that matters, not where you start. It's completely dependent on gearing, you can't tell where to shift from that graph alone because you don't know what the gear ratios are.
99% of cars (that aren't shit) just shift at redline, that's what they're geared for.
Your prius or whatever is probably not geared for acceleration, it's geared for efficiency, but if you're doing dyno pulls to figure out exactly where shift a shit car you fucked up a long time ago.
With a spreadsheet including plotted horsepower @ rpm and gear ratios, you can see where the power in second gear becomes higher than the power in first gear at the same road speed, without calculus. That's your shift point.
>you should totally rev to the redline despite losing 50% of the power
If you don't know what you are talking about you should not post.
Just go pedal to the floor in second gear and hold it until the car stops pulling you super hard, bang it into 3rd and do the same.
I shift my 4cyl at like 5k but mine has a supercharger so an na might be better to do it sooner?
>shift at 4k
>next gear is 70%
>I'm now at 1.5k rpm
It
Depends
On
Gearing
Also, nobody gives a fuck about diesels, learn how to read a graph, learn how to do elementary math, and then realize that the people making the fucking car did all of this already and the gearing (which they designed) is optimized to shift at redline (close to peak engine output).
Nobody who drives an A6 cares about "peak acceleration", if they did they would buy a new non-shit car. Pick any, ANY stock petrol car that uses it's 0-60 times as a selling point, and I promise you the person who set that time was shifting at redline like the car was designed to.
Nice strawman you have there.
But that won't change the fact that you are wrong.
Past 4.3k this engine loses power fast (50% over 200 rpm). Is true you will gain couple % back when you upshift because the engine will be higher in the revs but you won't gain enough to compensate for losing 50%.
So again, stop posting if you are retarded.
???
But you appear to completely lack understanding for what he says, either that or you simply can't read.
Shift point depends entirely on gearing, where you are in the power band before and after the shift respectively depends entirely on gearing.
But we have the gearing for the model. Is right there in the first post.
From 3rd to 4th shifting around 4.3k is better than shifting at 3.8k (peakpower) or 4.5k (redline).
Past 4.3k you have less power if you don't change gears than you will have upshifting.
Read this again
>It
>Depends
>On
>Gearing
Then do this
>Pick any, ANY stock petrol car that uses it's 0-60 times as a selling point, and I promise you the person who set that time was shifting at redline like the car was designed to.
>OP asks when he should shift for max acceleration
>gives us gearing
>HURR DURR IT DEPENDS ON GEARING HURR DURR
Holy shit you are retarded.
Conversation has evolved fuccboi, I said multiple times that nobody gives a single fuck when you should shift an A6, sell it and buy a car that isn't a diesel and doesn't have a shit powerband, then just shift that car at redline.
You're saying the mechanical advantage of staying in a lower gear beats out the power gain you might get from shifting back down into the powerband.
I can tell you you're wrong. My turbo miata will go all the way up to 7600rpm, but power falls abruptly after 6000. It barely accelerates past 6800. When I shift up the power comes back on hard enough to push my head back. There's no way in hell it would be faster running up to redline.
Than why the fuck are you arguing with me when I was just answering OPs question?
Are you that desperate for attetion?
>Mfw Veeky Forums is this retarded
OP we need to know what gear box you have in order to determine the proper shift points (including engine data you nitpicky shitfarts).
Anyone pulling numbers without this information is just throwing guesstimated bullshit.
What this guy said.
ITT: people who think acceleration depends on torque
this. embarrassing.