GT Sport Optimal Shift Points

[Vegard]

Does this make sens?
What do you think?

You may not be an engineer but you think like one, good work.

 

[breeminator]

Sorry Groundfish, but here is one last attempt to convince people with some equations. The guy in the post elsewhere that I linked to above had the same result, but it wasn't quite so obvious how exactly he arrived at it, so I wanted to show the derivation of it in a clearer way. I asked a friend who was top of his year in his engineering degree to verify that what I was saying was correct, and he presented another way of arriving at the same answer, so I will include both approaches so people can see that both methods, starting from basic standard physics principles, give the same answer.

Method 1:
Start with the following two basic equations:
(1) force = mass * acceleration
(2) power = force * velocity
Rearrange (2) to make force the subject:
(3) force = power / velocity
Combine (1) and (3) to eliminate force:
(4) mass * acceleration = power / velocity
Rearrange (4) to make acceleration the subject:
acceleration = power / (mass * velocity)

So at any given speed, and for a given mass of car, acceleration is directly related to power.

Method 2:
energy = 0.5 * mass * v^2
Differentiate this with respect to time to give the rate of change of energy, which is power
power = dE/dt = 0.5 * mass * 2v * dv/dt = mass * velocity * acceleration
(see e.g. https://www.physicsforums.com/threads/derivative-of-velocity-squared.302929/ if you don't understand the differentiation step)
Rearrange this to give
acceleration = power / (mass * velocity)

So two different methods, both arrive at the same answer.

 

[breeminator]

This is the simplest explanation I could find

I was a bit baffled when I watched this, as it seemed such nonsense, but I think I see the source of their confusion. The video says "Horsepower is torque applied over time.". I think the creator is confusing two different distances:

1. work done = force * distance
which leads to
power = rate of doing work = force * distance / time
which is said, verbally, as "force times distance over time"

2. torque = force * distance
so I think they have mistaken these two different distances as being the same, and come up with "power is torque over time".

The distance in 1 is the distance that a force moves through in the direction it is being applied.

The distance in 2 is the distance from the force to the pivot. The distance the force is moving in the direction of application per second is
(distance to pivot) * (rpm/60) * 2 * pi. Combining the torque with that equation will give the same result as working in terms of power.

 

[Groundfish]

Well now I think we agree Brem.
Real world times always result from physics laws.

Re the point. What I did when trying to learn shift points is test on mountain straight at panorama from a roll and dig.

 

[VFOURMAX1]

Torque only does work when combined with movement,

Torque as defined in the dictionary and its use to referring to the power output or characteristics of an engine is exactly as the dictionary defines.

It is the measurement of the amount force of an engines rotation power output at the crankshaft that hence is transferred through the transmission and driveshaft to the rear wheels in automotive applications.

Without that transmitting of rotational power output there is no such thing as a measurement for the horsepower output of the engine because without the rotational torque an engine produces there is no horsepower to measure.

I cannot understand why you seem to not be able to comprehend this when dealing with the differences in the ways of the different forces and the way they are measured in play in an engines power ratings.

And yes higher torque engine does initially move higher weights or loads easier and with more force or power than a low torque engine.

According to you the whole free world is wrong and torque as a measurement of power output in a rotational engine is just a made up fable or unicorn and does not have any meaning or even exist to make a difference.

Talk about being baffled about a person not understanding a concept!
torque
noun (1)
\ ˈtȯrk

\
Definition of torque
(Entry 1 of 3)

1 : a force that produces or tends to produce rotation or torsion an automobile engine delivers torque to the drive shaft also : a measure of the effectiveness of such a force that consists of the product of the force and the perpendicular distance from the line of action of the force to the axis of rotation
2 : a turning or twisting force

horsepower
noun
horse·pow·er | \ ˈhȯrs-ˌpau̇(-ə)r

\
Definition of horsepower
1 : the power that a horse exerts in pulling
2 : a unit of power equal in the U.S. to 746 watts and nearly equivalent to the English gravitational unit of the same name that equals 550 foot-pounds of work per second
3 : effective power

 

[breeminator]

Without that transmitting of rotational power output there is no such thing as a measurement for the horsepower output of the engine because without the rotational torque an engine produces there is no horsepower to measure.

As I said earlier in the thread, power is proportional to torque multiplied by angular velocity, so I'm not sure why you think I don't understand that.

The bit you quoted, "Torque only does work when combined with movement" is a simple scientific fact. I think it was somewhere around age 14 that we were taught at school "work is done when a force moves its point of application through a distance.".

 

[VFOURMAX1]

As I said earlier in the thread, power is proportional to torque multiplied by angular velocity, so I'm not sure why you think I don't understand that.

The bit you quoted, "Torque only does work when combined with movement" is a simple scientific fact. I think it was somewhere around age 14 that we were taught at school "work is done when a force moves its point of application through a distance.".

What came first the chicken or the egg? There is no egg without the chicken and no chicken without the egg!

 

[breeminator]

What came first the chicken or the egg? There is no egg without the chicken and no chicken without the egg!

It doesn't matter, we're trying to answer the question of what rpm to shift at. The simplest way to answer the question is to understand that
acceleration = power / (mass * velocity)
It's not me vs the free world with this - if you look at post #4 in this thread, he also doesn't reference torque, and that post has quite a few likes, so I conclude he and the people who liked his post agree with me.

 

[VFOURMAX1]

It doesn't matter, we're trying to answer the question of what rpm to shift at.

I agree but to answer that question the power traits of the engine being used at the time has a bearing on those shift points.

A high torque lower rpm engine can generally maintain better in the lower end of the optimal power band while a low torque peaky high rpm type of motor will generally perform better at the upper spectrum of the rpm band.

We may not agree on the reasons but the lower tractor style power band engines such as the GT3 Mercedes can pull off lugging out of the corners at a lower rpm level than say the GT3 Lambo which does not bode as well on power output lugging the engine down.

My experience with engine applications does reflect my opinion that the torque curve has a lot to do with the level and the width of an engines power band, cubic inches, bore and stroke as well but the information the game gives is to limited to say this is the optimum shift point for all situations with this car/motor combination.

It is trial and error and even driving style can alter a persons results.

 

[phil_75]

So...

Torque = How much you can pull
HP = How fast you can pull it

So doesn't matter how much torque you have if you cant pull it fast and doesn't matter how fast you can pull it if you cant actually pull it...Or shall i get my coat???

 

[breeminator]

It doesn't matter, we're trying to answer the question of what rpm to shift at. The simplest way to answer the question is to understand that
acceleration = power / (mass * velocity)

If anyone really wants to do this the hard way, then I'll convert that equation to torque:

power = k * rpm * torque, so
acceleration = k * rpm * torque / (mass * velocity)

rpm / velocity can be seen as the "whole car gear ratio", incorporating the gear, final drive and size of wheel + tyre, so if we define, for this purpose
gear ratio = rpm / velocity
we have
acceleration = k * gear ratio * torque / mass

you can also derive this directly from force = mass * acceleration, by calculating the accelerating force, which is the force at the contact patch between tyre and road, as k * gear ratio * torque. This is why Exotime found the same shift points doing it both ways.

@Exotime if you make the x-axis of the 2 graphs the same, it will be clearer. The two graphs you posted have different x-axis scales which is why I was originally puzzled by what you said about them, but I see now it's just because the x-axis scales are different. Additionally, if you plot power / velocity instead of power in the top graph, the shape should become the same as that of the bottom graph, as both will then be showing acceleration (multiplied by a different constant in each case).

So we have two equally correct ways to determine acceleration:

acceleration = power / (mass * velocity)

acceleration = k * gear ratio * torque / mass

Why is it better to use the first one to answer this question? Because the game provides you with a complete power curve, and calculating it that way is independent of gear ratio. So all you need to do to maximise acceleration at any given speed is maximise your power. Changing gear isn't changing any element in that equation. If you use the 2nd one, then when asking when to change gear, you are changing not only the torque but the gear ratio, so you don't maximise your acceleration by maximising torque, you maximise acceleration by maximising the product of torque and gear ratio, and this is harder to work out from the information the game provides, you need to do what Exotime did, and it's pointless because the game has essentially already done the work for you by providing the power curve.

 

[Exotime]

@breeminator
Actually, both x-axis are the same, but they are 2 separate screenshot, not exactly the same, that's why lol.

I agree with you saying that the torque graph is useless most of the time..
I just think it helps when tuning is allowed. to compare 2 gears ratio (longer first gear vs shorter first gear.)
(Even though it is common knowledge that a shorter gear will provide a better "acceleration" than a longer one but on a shorter distance... if grip permits it of course)

I could calculate that, but how do I find the value of the velocity? (If it's possible..)

Here is the graphs: (I've only used the 3 first gears for readability)

Supra Gr3
x-axis : Speed (KM/H)
y-axis : Torque/HP (See the legend below)

These are the calculated values that produce the graphs above.

 

[breeminator]

I could calculate that, but how do I find the value of the velocity? (If it's possible..)

It's speed, basically, so if you plot power divided by speed, it should be the same shape as the graph with torque and gear ratio combined together.

 

[OGMowerman]

Umm... It's not that simple (in real life - whether this applies in GT Sport or not I can't comment)

You don't want to shift "Just as the power drops" but when it will be at an equal point in the curve at the new RPM. As such every shift point is dependent on the gear you're going from, the gear you're going to and the rev drop for all of gears themselves.

For example:

Gear 1 -> Gear 2

Hypothetical situation: Car has a symmetrical and triangular power curve and a 1000 rpm rev drop between the two gears. Peak power is at 6,000rpm. The optimal shift point is actually then 6,500rpm, not 6,000rpm. As such it is not an exact science at all and varies on lots of different factors.

All of this information is practically impossible to deduce from the miniscule power curves that GT Sport provides, especially with no grid and no correlative details of each gear including a rev drop.

At the very least, combining the power curve graph with the gear ratio graph would be helpful, but still not much use without finer details.

Best option is to drive the car yourself and work out whether it is quicker (using something like braking point speed) or slower when you shift earlier or later in the rev range.

Negative. You never want to push past the cliff. You are cutting power on both sides. You are past peak on current gear and losing torque range in the next gear. For instance, with the McLaren 650s, at 7800 rpms power falls off. Shift gear and next gear comes in a little over 6k rpms. Torque starts at 6k so you are almost optimal for power band usage. If you push higher, you fell out of power and at the top and are reducing the range for next gear because you kick into the gear at a higher rpm. Add to this you are burning more fuel to do less so you lost there too. You do have the extra rpms that can be used to reduce tire wear via less torque in corners but would be better off riding low in the next gear to get tire wear and fuel down

 

[fastone371]

Engine Torque is not that important for acceleration. After all, the amount of torque going to the wheels can be multiplied by the gearbox. Power can’t be multiplied in a car.

This is why relatively torqueless vehicles with vtec can still accelerate as fast as cars with the same power/weight ratio and much more torque.

Power and weight are the most important factors in how fast a car accelerated. And, at high speed, wind resistance, but you couldn’t change that by shifting anyway so it is kind of irrelevant in this discussion.

This is some of the most incorrect info I have ever read. Torque is the most important function of accelerating a vehicle, HP as a rule of thumb is the cars ability to maintain speed once the torque accelerates a vehicle to speed. If all you needed was a lot of HP and gear reduction semi trucks would not have 1600ft lbs of torque and only 575HP. Conversely F1 cars wouldn't have nearly the HP they have now if it wasnt for the enormous torque of the electric motors they use as part of the hybrid system because they would need to redesign the ICE for more torque to accelerate out of corners sacrificing hi RPM HP. A vehicle needs ample quantity of both torque and HP to accelerate and maintain speed once it gets there.

 

[behindwalters]

The interesting thing about GT Sport is the shift bar is dynamic; it will flash at peak power instead of engine redline. So for most cars, shifting at the ‘flashing blue’ or slightly thereafter will be the ideal shift point. Because of this, compiling a list of all 62 cars, with almost the same shift points, is kind of pointless.

View attachment 826992

Here above is the Gr.3 Supra power band. As you can see, peak torque occurs at ~5,600 and then drops off a cliff — and power only plateaus from there, and increases by a very negligible amount until redline. Because of this, you’re going to want to shift the Supra at 2/3rds instead of the ‘flashing blue.’ This is pretty rare though, especially for a new race car. I’m showing you this because it’s what you want to look out for.


View attachment 826993

Here’s another example, the McLaren F1 GTR. As you can see, similar to the Supra, power plateaus, and there’s really no point to wringing it out that extra ~1000rpm since torque is gone. So you’d want to shift the McLaren F1 when the bar fills up, but before the ‘flashing blue’ occurs.

View attachment 826994


This is the McLaren 650s Gr.3 — with a nice healthy powerband all the way to fuel cutoff. This car, you’ll want to ring out as long as possible.

Hopefully this helps you understand what you’re dealing with. As I said before there’s only a handful of cars that need a special shifting regiment.

I've never noticed that with the line indicator, I'll have to check it out. Thanks.

There is only one way to find either engine speed at peak power, max horsepower or max torque. Only one of these is actually measured, that is torque. Horsepower is a calculation based on torque to show where an engine develops peak power. Since GT gives you two variables, the equation to determine around what rpms you need to shift (max power) is,

RPM = (HP * 5250) / TQ

5250 is the magic number and ultimately part of where the term horsepower comes from. For example, my wife has an Odyssey that has 250hp and 250 lb/ft of torque. Because of that I know the engine speed it makes max power is 5250 rpms.

An easy way to get an idea of where to shift is comparing the HP and TQ. If HP is higher than TQ, you will shift gears after 5250 rpms. If HP is less, then before. I have an E55 with 469hp and 512lb/ft, so it's rpms at peak are a little over 4000. It's also why diesel trucks pull so well. They have much more tq than HP and can tap into it much lower on the tach.

Of course this depends on how the game was created, but that's how it's done in real life.

 

[breeminator]

For example, my wife has an Odyssey that has 250hp and 250 lb/ft of torque. Because of that I know the engine speed it makes max power is 5250 rpms.

No, that's not correct, because the peak power and peak torque are not necessarily at the same rpm as each other. The equation you stated relates power to torque at the same rpm.

 

[fastone371]

No, that's not correct, because the peak power and peak torque are not necessarily at the same rpm as each other. The equation you stated relates power to torque at the same rpm.

Not only that but in real life most cars accelerate quicker when shifting g above peak torque, you want the engine to fall into the "meat" of the torque curve after the shift point.

 

[behindwalters]

Just so it's here...

I didn't go all the way through the thread but there are quite a few misconceptions that I believe stem from not knowing the difference between hp and tq. Torque is measured and HP is a calculation based on torque. Max Torque tells you how much power a car has period and is usually the given variable needed to figure everything else out. Max HP tells you where (at what RPM) the engine produces it's maximum power. This is important to consider for determining where in the RPM range designers want their engines producing max power (turbo vs. SC, etc.)

There are 3 variables (TQ, HP & RPM) and one constant (5252, remember this #) in the formula to figure this out. You need 2 in order to get the other. I drive an E55 that I will use as an example.

Stock it has, max, 469hp & 516 lb/ft of tq. Right off the bat, I know my engine produces it's max power lower than 5252 RPM (because it has more tq than HP) so I should never let it Rev out to there. Diesel trucks are a more extreme example of this. If you think about the E55 engine, this makes sense because it's supercharged and thus, force fed induction through a chain. At some point, the effort to spin the SC faster for more power cannibalizes overall engine power where a turbo wouldn't because it's exhaust driven. The benefit over a turbo is instant, low end power. Since I'm not at the track all the time, I like this better.

Here's how you figure out how much power an engine produces at any given rpm.

(TQ x RPM)/5252 = HP @ that RPM. (Tq is the max engine tq number here)

You can rearrange this formula to get whatever you need. Using this, max power for my car is produced at 4,773 RPM. And even though it redlines at 6,200, I shouldn't take it there unless I'm trying to save time from a gear change for a corner or something like that .

I can also use this to say my engine produces 255bhp @ 2,600 RPM. This is the version of the formula I use for the game since they give us the maxs. And granted, these are race cars, so there's probably not any examples like my car, which is why I used it as an example. I think it can help clear some confusion. It ALWAYS depends on what RPM you're at. Keep in mind, BoP changes things. They usually give max HP and you have to work backwards. In gt7, I ballpark the tq by going by back to the garage and ching HP to match BoP, since you can't see the graph in a race under car settings (please fix that Gran Turismo).

The 5252 number comes from way back when they were trying to determine how much work 30k (I think) horses could do in a hour or something like that, Its been awhile but it's out there if you're interested in the history.

Anyway, hope this helps.

 

[behindwalters]

Just so it's here...

I didn't go all the way through the thread but there are quite a few misconceptions that I believe stem from not knowing the difference between hp and tq. Torque is measured and HP is a calculation based on torque. Max Torque tells you how much power a car has period and is usually the given variable needed to figure everything else out. Max HP tells you where (at what RPM) the engine produces it's maximum power. This is important to consider for determining where in the RPM range designers want their engines producing max power (turbo vs. SC, etc.)

There are 3 variables (TQ, HP & RPM) and one constant (5252, remember this #) in the formula to figure this out. You need 2 in order to get the other. I drive an E55 that I will use as an example.

Stock it has, max, 469hp & 516 lb/ft of tq. Right off the bat, I know my engine produces it's max power lower than 5252 RPM (because it has more tq than HP) so I should never let it Rev out to there. Diesel trucks are a more extreme example of this. If you think about the E55 engine, this makes sense because it's supercharged and thus, force fed induction through a chain. At some point, the effort to spin the SC faster for more power cannibalizes overall engine power where a turbo wouldn't because it's exhaust driven. The benefit over a turbo is instant, low end power. Since I'm not at the track all the time, I like this better.

Here's how you figure out how much power an engine produces at any given rpm.

(TQ x RPM)/5252 = HP @ that RPM. (Tq is the max engine tq number here)

You can rearrange this formula to get whatever you need. Using this, max power for my car is produced at 4,773 RPM. And even though it redlines at 6,200, I shouldn't take it there unless I'm trying to save time from a gear change for a corner or something like that .

I can also use this to say my engine produces 255bhp @ 2,600 RPM. This is the version of the formula I use for the game since they give us the maxs. And granted, these are race cars, so there's probably not any examples like my car, which is why I used it as an example. I think it can help clear some confusion. It ALWAYS depends on what RPM you're at. Keep in mind, BoP changes things. They usually give max HP and you have to work backwards. In gt7, I ballpark the tq by going by back to the garage and ching HP to match BoP, since you can't see the graph in a race under car settings (please fix that Gran Turismo).

The 5252 number comes from way back when they were trying to determine how much work 30k (I think) horses could do in a hour or something like that, Its been awhile but it's out there if you're interested in the history.

Anyway, hope this helps.

Edit-

I went and checked the gr3 vette on the game and got the ideal rpm For max power both with and without the BoP hp/tq #s and got almost exactly the same ideal rpm (5176). So, maybe you can just run the formula on the "normal" car setup and it will work for BoP as well. This way you don't have to go back and forth all the time.

 

[behindwalters]

Can I ask a simple question? What exactly engine torque does?

It moves the car. HP is a calculation derived from torque. Torque is measured by a torque bar. All this discussion is really trying to get at how engine designers use torque to effect acceleration in different scenarios depending on the engines purpose. There are other factors, but ultimately you cannot have HP without torque. Period. As far as how torque and HP relate to each other and when to shift, I put the formula used to determine power somewhere in here.

 

[behindwalters]

I always liked the quirky saying "you can have torque without power, but you can't have power without torque"

Then again, I've also always liked a Snickers as well. Fun fact, they're awesome when you keep them in the freezer.

You can't have a chicken without an egg... Or is it the other way around? I forget.