GT6 Top Speeds Are Not Realistic, Please Fix PD!

[BlueShift]

From wikipedia, the power needed to figth the drag is :

I will do calculation based on this tonigth with the temperature + altitude of the track to find "p". Before, we need to find the exact power at rpm where she blocks in the VI, rpm is easily do-able comparing speed to tire size and gear ratio, power is... Well like ALL GT they don't give a proper scale, we'll use a rule put on the screen.

There's no speed difference between one straigth or the other (minus the hill) so that mean there's no front or rear wind, meaning v is the car's velocity.

I'll tame that, that starts to get me mad.

 

[Exorcet]

You have P (before losses), it's given in the game. You want to find F. Then you can compare to a real F computed from real A and CD.

Or by "p" did you mean rho, which is the little p like thing after 1/2?

 

[jimipitbull]

it really ruins the game for me to know that Im not driving a realistic simulation.

It's all about perception. Would it ruin a realistic simulation, if you knew you were playing a game?

People complained about GT5 having very little sense of speed. Easiest way to fix that, is to increase the speed.

I'd much rather a 10% increase in speed, as opposed to motion blur and lens flare trickery.

 

[fifomaniak]

I assumed 85% power transmission to the wheels


The weight reduction weight is closer to real life, also weight won't change the top speed.


Rolling resistance is too small to make so much difference.

At high speed it is also very important. Test your car's acceleration at high speeds with different tire pressures. It will be a lot faster with higher pressure.

 

[YZF]

Having not seen a road car do 230 mph with 490 HP doesn't say much. My math works out.

Your math is wrong because of this: "my hypothetical car essentially has a flat powerband, the engine makes 490 HP at every RPM"

SL55AMG (or any other road car) doesn't have such power curve, thus your math is wrong because it doesn't represent real road car engine.


When i said that '490hp is not enough to reach 230mph', i meant road going car with all of its engine characteristics, behaviour, etc. I absolutely don't care what kind of pushing power theoretical 490hp with flat power curve could achieve, I want real representation of cars in GT6. And the current top speed modeling in GT6 is flawed. Nothing more to talk about

 

[BlueShift]

You have P (before losses), it's given in the game. You want to find F. Then you can compare to a real F computed from real A and CD.

Or by "p" did you mean rho, which is the little p like thing after 1/2?

Yup. I can't find A (or S if you speak about S.Cx instead of A.Cd) on the web, that's the only data I miss.

rho is the "air", I want to measure if it's rigth or not. If it varies from 1.0 at 24°C at 0m to 0.87 at +/-5°C and +/-0m, there we are, 231mph instead of 201mph and the game is rigth.

Maybe I should use a car where I have an actual A.Cd instead of crawling the web to find the Corvette's, it's so new...

 

[Vegard]

If it varies from 1.0 at 24°C at 0m to 0.87 at +/-5°C and +/-0m,

That would also affect the power of the engine by a little bit, somewhat counteracting the increased density.

But seriously, are you saying that a 19 degree drop in temperatur would account for 30 mp/h
And, are you assuming that Chevrolet tests top speed in the worst possible conditions

 

[BlueShift]

That would also affect the power of the engine by a little bit.
But seriously, are you saying that a 19 degree drop in temperatur would account for 30 mp/h
And, are you assuming that Chevrolet test top speed in less than ideal conditions

You're rigth for the hp aswell.
1 to 0.87 doesn't seem a lot when you know what happens for water at 0°

Testing atm.

 

[Exorcet]

At high speed it is also very important. Test your car's acceleration at high speeds with different tire pressures. It will be a lot faster with higher pressure.

The rolling resistance is on the order of 50 lbs, so if you went from a car with normally inflated tires to perfect lossless wheels, you only reduce drag by that much. Aero drag is hundreds of pounds at speed.

Your math is wrong because of this: "my hypothetical car essentially has a flat powerband, the engine makes 490 HP at every RPM"

That doesn't make the math wrong. It also doesn't make what I said unrealistic. Give a car with any powerband a CVT or a car with a reasonably flat powerband and an 8 speed transmission and you get the same thing.

SL55AMG (or any other road car) doesn't have such power curve, thus your math is wrong because it doesn't represent real road car engine.

The powerband of the engine is unusual, but the thrust curve of the car, which is what matters, is not unusual.

the current top speed modeling in GT6 is flawed

No one has said otherwise.

Yup. I can't find A (or S if you speak about S.Cx instead of A.Cd) on the web, that's the only data I miss.

http://www.motortrend.com/roadtests/tuners/112_0710_the_science_of_speed/viewall.html

Use the Z06

 

[YZF]

You're rigth for the hp aswell.
1 to 0.87 doesn't seem a lot when you know what happens for water at 0°

Testing atm.

To ease your testing I suggest you to try CarTest 2000 software which does what you want. And you can adjust almost any settings (power, torque, rpms, gearing, drag coef, frontal area coef, etc, etc.) It will calculate you acceleration, top speed and so on.

 

[YZF]

That doesn't make the math wrong. It also doesn't make what I said unrealistic. Give a car with any powerband a CVT or a car with a reasonably flat powerband and an 8 speed transmission and you get the same thing.

That makes the math wrong in our context: driving in real life with real road car.

You can put any gearbox to such car and it will not do 230mph. It won't. I tried and got results and you didn't try. Thus your math is wrong

Try this and see for yourself. Neither 505hp Corvette, nor 550hp Ford GT, not even 600hp Viper can do 230mph

http://www.cartestsoftware.com/cartest2000_demo_applet.html

 

[Verbal]

rho is the "air", I want to measure if it's rigth or not. If it varies from 1.0 at 24°C at 0m to 0.87 at +/-5°C and +/-0m, there we are, 231mph instead of 201mph and the game is rigth.

For 231mph instead of 201mph you'd need to reduce air density by 34% (assuming for a moment that somehow you'd still manage to produce the same power), remember that the speed is cubed. From 24°C to 5°C air density will go up by 7%. A 34% reduction in theory would mean 125° C

 

[Exorcet]

That makes the math wrong in our context: driving in real life with real road car.

The only context is you were saying 490 HP can't get a car to 230 mph. Maybe you want to add to that that it's a car that could realistically be built.

Saying that 490 HP is not enough for any speed is wrong mathematically. As far as the car being realistic, I worked out the numbers. Sub 20 ft^2 and sub .3 CD are realistic even if they aren't common.

You can put any gearbox to such car and it will not do 230mph. It won't. I tried and got results and you didn't try. Thus your math is wrong

Try this and see for yourself. Neither 505hp Corvette, nor 550hp Ford GT, not even 600hp Viper can do 230mph

http://www.cartestsoftware.com/cartest2000_demo_applet.html

I'm assuming you tried with those three cars, all of which have more than 20 ft^2 area, .3 CD, or both. I can't look at it now anyway.

 

[fifomaniak]

The rolling resistance is on the order of 50 lbs, so if you went from a car with normally inflated tires to perfect lossless wheels, you only reduce drag by that much. Aero drag is hundreds of pounds at speed.

But rolling resistance is related to aero drag, because at higher speeds with downforce the car is being pushed harder to the ground, therefore tires flatten and create more resistance. Get on a bike and try to drive if with good tire pressure, then drop it a bit, then tell me it does have very little affect on top speed.

 

[Vegard]

But rolling resistance is related to aero drag, because at higher speeds with downforce the car is being pushed harder to the ground, therefore tires flatten and create more resistance. Get on a bike and try to drive if with good tire pressure, then drop it a bit, then tell me it does have very little affect on top speed.

Most road cars produce lift, some cars produce downforce.
Still, the total effect of downforce on top speed (with regard to increased friction, not drag) is minimal.

 

[BlueShift]

For 231mph instead of 201mph you'd need to reduce air density by 34% (assuming for a moment that somehow you'd still manage to produce the same power), remember that the speed is cubed. From 24°C to 5°C air density will go up by 7%. A 34% reduction in theory would mean 125° C

You mean the cars are faster at 100°C in very high altitudes ? Okay, didn't knew this.
So anyway, I agree by the numbers there is a problem.

For information, I found another bug and this one is reproducable and see-able
Go in Road X, check the temp (21°C, 6:45 am). Mess around with the timer, notice how temp change when back in 6:45. I can get 25° at the same hour now

377kph at somewhere near 5950rpm in VI.

VI x Final = 0.597 * 3.420 = 2.04174 rmp/wheel rev

She's got 285/30 ZR 20 in the rear => diameter is 679mm / 26.7in. xPi = 2.133m per wheel turn

=> 2.133m / 2.04174 = 1.04469 m/rpm

@5950rpm => 6215.90 m/min => 372.95 kph.

There's no motor loss. That's a 100% rendering machine and no tire diameter variation, here is the bug, guys !

Please a car ingeneer look in my numbers and say where I'm wrong ? I have a friend that works in Renault's gearboxes, I will ask to him (but I see him once every 3 years).

 

[YZF]

The only context is you were saying 490 HP can't get a car to 230 mph. Maybe you want to add to that that it's a car that could realistically be built.

Did you forget what this thread is about? It's about real cars in GT6 and in reality. It's not about your oversimplified math which is not suitable here.

Saying that 490 HP is not enough for any speed is wrong mathematically.

I don't care about mathematics, I care about results i see on the screen. There is no car in real life that can achieve such speed. I can give you 20 examples and all of them will prove your conclusions are wrong.

Until you give me at least one example with a real life, road legal car which can do that, your theory means nothing.

I'm assuming you tried with those three cars, all of which have more than 20 ft^2 area, .3 CD, or both. I can't look at it now anyway.

Those 3 cars was just one example out of hundreds.

 

[Exorcet]

I assumed 85% power transmission to the wheels

It seems like this wasn't factored in correctly. So my assumed max CDA should be 85% of what I stated (.3*20 ft^2).

Did you forgot what is this thread about? It's about real cars in GT6 and in reality. It's not about your oversimplified math which is not suitable here.

My math is completely suitable. The thread is about an apparent mismatch between simulation car speed and real car speed. Your claim that 490 HP is not enough to reach a certain speed is wrong because speed depends on more than just HP. Since this is true, I went to correct your statement because it is of no use in the discussion. In other words, anyone assuming that top speed can be found by looking at power alone is wrong.

I'm not here to argue for the sake of arguing, but it should be pretty clear that what I said is correct, you can't judge top speed from just power. If anyone thinks they can, that's not going to help solve the problem here.

I don't care about mathematics

Then you don't care about what you see on screen. All you see on screen is math.

There is no car in real life that can achieve such speed.

This means nothing. Show me math and prove that 490 HP (or any HP) is not enough to reach 230 mph.

I can give you 20 examples and all of them will prove your conclusions are wrong.

Then do so. You haven't so far, and you've had plenty of chances. Going "you're wrong" without any supporting evidence won't get you anywhere.

Until you give me at least one example with a real life

This is not necessary.

Those 3 cars was just one example out of hundreds.

Those 3 cars are unrelated to the discussion.

 

[Vegard]

It seems like this wasn't factored in correctly. So my assumed max CDA should be 85% of what I stated (.3*20 ft^2).

Yeah, I got 514whp reqiured with your numbers and a 2000lb car.
Frontal area of 20ft^2 is higher than a McLaren F1, and .30 is far from super slippery though.
The Opel Calibra, launched 1989, had .26!
The Turbo model did ~150 mp/h with 204PS ~200 hp:

Still; the Mercedes, and all cars I've tested, fly past their official top speeds at SSRX and something is very wrong there.

 

[YZF]

The thread is about an apparent mismatch between simulation car speed and real car speed. Your claim that 490 HP is not enough to reach a certain speed is wrong because speed depends on more than just HP.

In the context that we are talking about, my claim is correct. Speed depends on many factors, but all others (except power) are more or less equal between similar cars, thus they aren't important. All sports road cars have more or less the same aero, friction, tyres, etc, etc. There are differences, but these are insignifican compared to the 30mph difference at over 200mph

As such, saving my time and effort for redundant typing of 'almost fixed constants', I mentioned only the most important factor (engine power) in this context (road cars, sports category).

Usually people are capable of understanding such things (a.k.a 'reading between the lines'), but it seems that you are having problems with that. Or maybe you don't want, whatever.

So now that we have finally cleared out the real cause of this discussion, the only thing that's left is for PD to fix this issue, as everyone agrees that it's flawed.

 

[Exorcet]

Yeah, I got 514whp reqiured with your numbers and a 2000lb car.

You should have posted that before, I didn't think too much of my original numbers since .3 is better than average for a large sports car, but YZF's datasheet reminded me that the SL already had a really low CD.

Still; the Mercedes, and all cars I've tested, fly past their official top speeds at SSRX and something is very wrong there.

Yes, this isn't in dispute, but we need to understand how to find to top speed to say what's wrong.

In the context that we are talking about, my claim is correct. Speed depends on many factors, but all others (except power) are more or less equal between similar cars, thus they aren't important. All sports road cars have more or less the same aero, friction, tyres, etc, etc. There are differences, but these are insignifican compared to the 30mph difference.

In my link CD ranges from ~.3 (911) to .39 (Viper). CD goes from 19ish to 22. Go outside to other examples and things vary even more (Viper ACR CD, Lotus/Miata frontal area, etc). If we want to keep my original 20 ft^2 A, .25 CD is required. Go with 18 ft^2 and CD goes up to .28, this is quite realistic for a sports car.

Usually people are capable of understanding such things (a.k.a 'reading between the lines'), but it seems that you are having problems with that. Or maybe you don't want, whatever.

It's not reading between the lines, it's inaccurate.

So now that we have finally cleared out the real cause of this discussion, the only thing that's left is for PD to fix this issue, as everyone agrees that it's flawed.

It's been this way from the start. Again, showing that 490 HP is good enough to reach 230 mph does not mean I'm saying that SL55's should be going 230 mph.

 

[BlueShift]

http://www.motortrend.com/roadtests/tuners/112_0710_the_science_of_speed/viewall.html

Use the Z06

Thanks.
My turn to help : Carrera *couch* S *cough*

 

[Exorcet]

But rolling resistance is related to aero drag, because at higher speeds with downforce the car is being pushed harder to the ground, therefore tires flatten and create more resistance. Get on a bike and try to drive if with good tire pressure, then drop it a bit, then tell me it does have very little affect on top speed.

A bicycle with deflated tires isn't a good reference for comparison, the drag/resistance ratio is completely different and you wouldn't drive with deflated tires.

Using info from the Z06 I posted, I find 750 lbf drag at 197 mph. Add 50 to this to represent rolling resistance. So 800 lbf total.

sqrt(8/7.5)*197 = 203.5 mph. Switching from normal tires to perfect tires gives you 6.5 mph if you assume 50 lb of rolling resistance. GT is overshooting by 20 mph+ for ~200 mph cars.

 

[Swagger897]

You mean the cars are faster at 100°C in very high altitudes ? Okay, didn't knew this.
So anyway, I agree by the numbers there is a problem.

For information, I found another bug and this one is reproducable and see-able
Go in Road X, check the temp (21°C, 6:45 am). Mess around with the timer, notice how temp change when back in 6:45. I can get 25° at the same hour now

377kph at somewhere near 5950rpm in VI.

VI x Final = 0.597 * 3.420 = 2.04174 rmp/wheel rev


=> 2.133m / 2.04174 = 1.04469 m/rpm

@5950rpm => 6215.90 m/min => 372.95 kph.

There's no motor loss. That's a 100% rendering machine and no tire diameter variation, here is the bug, guys !

Please a car ingeneer look in my numbers and say where I'm wrong ? I have a friend that works in Renault's gearboxes, I will ask to him (but I see him once every 3 years).

Since we are using the tire diameter, wouldn't it be more efficient to use the circumference? And if so, where would you calculate in game circumference, and would you account for the surface area, or two points where the road and air meet I between the tire?

 

[whereSTheFUhd]

Since we are using the tire diameter, wouldn't it be more efficient to use the circumference? And if so, where would you calculate in game circumference, and would you account for the surface area, or two points where the road and air meet I between the tire?

He did use circumference. It's calculated from the stock tire size that the car comes with.

Not sure what you're trying to account for with the surface area.

 

[jlmcmillan1978]

It's all about perception. Would it ruin a realistic simulation, if you knew you were playing a game?

People complained about GT5 having very little sense of speed. Easiest way to fix that, is to increase the speed.

I'd much rather a 10% increase in speed, as opposed to motion blur and lens flare trickery.

If that's the case then I wish that those who complained about little sense of speed had kept their opinions to themselves. Slow cars move slowly, fast cars move fast, but if this is 'the real driving simulator' than the speeds should match those of the cars in real life, period.

If on the other hand PD wants to turn this into 'the real arcade simulator' then it's the beginning of the downfall of the title. I want nothing to do with the game if they are moving away from realism just because some seem to think that realistic isn't exciting enough.

 

[BlueShift]

Since we are using the tire diameter, wouldn't it be more efficient to use the circumference? And if so, where would you calculate in game circumference, and would you account for the surface area, or two points where the road and air meet I between the tire?

I did use the diameter to calculate the circumference:

She's got 285/30 ZR 20 in the rear => diameter is 679mm / 26.7in. xPi = 2.133m per wheel turn

I don't really understand what you meant about surface areas. The A.Cd of a car take all the car into account if you are telling tires should have independent aerodynamic models.

 

[iLex]

It's all about perception. Would it ruin a realistic simulation, if you knew you were playing a game?

People complained about GT5 having very little sense of speed. Easiest way to fix that, is to increase the speed.

I'd much rather a 10% increase in speed, as opposed to motion blur and lens flare trickery.

I thought the same thing.
However, I prefer no messing with the sense of speed or with the speed itself

If on the other hand PD wants to turn this into 'the real arcade simulator' then it's the beginning of the downfall of the title. I want nothing to do with the game if they are moving away from realism just because some seem to think that realistic isn't exciting enough.

What I think PD needs is a proper competitor on the Playstation. They need a competitor that makes them drop 2/3 of the cars (they just can't manage the huge amount of cars), makes them really think about the physics of the other 400 and makes them really think about the gaming/racing aspects.
I don't know how the physics of pCars are, but looking at the feature list (and graphics and sound) I think it is going to obliterate GT7 unless PD steps up their game. pCars seems to have everything to please the whole GT community, with the exception of a huge car list…

 

[jlmcmillan1978]

I thought the same thing.
However, I prefer no messing with the sense of speed or with the speed itself



What I think PD needs is a proper competitor on the Playstation. They need a competitor that makes them drop 2/3 of the cars (they just can't manage the huge amount of cars), makes them really think about the physics of the other 400 and makes them really think about the gaming/racing aspects.
I don't know how the physics of pCars are, but looking at the feature list (and graphics and sound) I think it is going to obliterate GT7 unless PD steps up their game. pCars seems to have everything to please the whole GT community, with the exception of a huge car list…

Couldn't agree with you more Mate. 👍

 

[Cosbuster]

People complained about GT5 having very little sense of speed. Easiest way to fix that, is to increase the speed.

Messing around with what you are supposed to simulate in a simulator is the worst way possible to "fix" something so trivial, vague and subjective. What's next, halving the weight figures for cars that don't corner as fast as some people "feel" would be appropriate? The easiest way to "fix" the sense of speed "issue" would be allowing users to fully adjust their field of view manually.

Like you said, sense of speed is perception-based. You can't just go messing around with the few factual numbers you have in order to improve something that cannot be proven as being wrong.