BHP changes once you buy a car!

[YZF]

You are - in fact powertrain losses can be different in each gear in the same car. The ballpark figures are around 15% for really efficient cars with the engine on top of the driven wheels (FF, RR and, to an extent, MR), more for those where they're at opposite ends and even more for cars that do both (4WD), with losses increasing as components sacrifice efficiency for durability.

This doesn't explain why I am wrong. Again - drive train (gearbox, wheelshaft, wheels, etc.) - remain the same for the same car and very similar for very similar another car. Losses may be different in each gear, and that's fine, but the gearbox is the same (we assume that), so the loss will not increase at the same rate, if you just increase the power.

For example, you take M5, and add 30% of engine power. Will the friction inside the same gearbox or wheels, suddenly increase 30% as well? No. Friction (and hence loss) will stay the same. So "percentage calculation" (i.e. taking % from engine power to get loss) is not correct.

Driven wheels have effect on loss, there is nothing new here, it's completely true, but again - calculation is more or less constant between the same car configuration, i.e. if one sports car (RWD, 6sp gearbox) has a 500HP engine and a 50hp power loss, then another similar sports car (also RWD, 6sp gearbox, etc), will have roughly the same power loss, even if it has 1000 HP engine installed. Again, not the same due to loss in the engine it self, but not a "percentage difference" either.

Unless someone else gives a proof that this is not the case.

You tuned them? You can't really be comparing like-for-like at that point, even if all you've done is lengthen the gears.

No. I just increased gear ratios for some cars, so that the test would not be limited by rev. limiter. I am not testing rev.limiters, I am testing maximum possible speed the engine can make a car achieve. This is completely valid thing to do, because PD, when they accidentaly introduced "artificial boost", did not adjust gear ratios to match this boost. Ofcourse. That's why this is bug and not implemented feature.

And when I test a GT6 car, which doesn't need gears to be adjusted, and compare the 'gain' vs. GT5, this gain is more or less the same as for the GT6 car, which had it's gear ratios increased.

So adjusting ratios doesn't increase/decrease/impact this artificial boost / bug / flaw. It just allows me to have more cars tested.

In GT5 nothing was changed.

A stock E60 M5 will, without the limiter, hit a rev limited 211mph in 7th

You mean in game or in real life? If in real life, then I have yet to see a stock car in real life, which will hit the engine rev. limiter in top gear (not electronic limiter/speed limiter). No sense and I haven't seen one ever, anywhere.

 

[Famine]

This doesn't explain why I am wrong. Again - drive train (gearbox, wheelshaft, wheels, etc.) - remain the same for the same car and very similar for very similar another car. Losses may be different in each gear, and that's fine, but the gearbox is the same (we assume that), so the loss will not increase at the same rate, if you just increase the power.

For example, you take M5, and add 30% of engine power. Will the friction inside the same gearbox or wheels, suddenly increase 30% as well? No. Friction (and hence loss) will stay the same. So "percentage calculation" (i.e. taking % from engine power to get loss) is not correct.

What?

Are you genuinely trying to say that if the gearbox loses 30hp at 300hp crank and you tune the car up to double that power it'll still lose 30hp? Only it doesn't... Parasitic losses eat a percentage of the power supplied to them - that's why efficiency is measured in percentage!

You mean in game or in real life? If in real life, then I have yet to see a stock car in real life, which will hit the engine rev. limiter in top gear (not electronic limiter/speed limiter). No sense and I haven't seen one ever, anywhere.

The rest of that post makes clear that it's in real life and then adds the reasons why it won't do that...

A stock E60 M5 will, without the limiter, hit a rev limited 211mph in 7th, but the CdA and approximate wheel power rating suggest it'll max out at 198mph. Handily that occurs at 7,750rpm in 7th, which is also exactly where the peak power is - as if BMW knew what they were doing

If the car in either game will cruise past that on the flat at SSRX, it either has too much power or too little drag and I largely agree with you that it's the drag that's lacking.

If you can't be bothered reading all that again:

Real car geared to 211mph
Real car runs out of power at 198mph
If GT cars go faster, they have too much power or not enough drag.

 

[Sage Ages]

Lotus Elise 11 134BHP, Garage 133BHP
Bmw CSL 355BHP, garage 354BHP
S2000 06 238BHP garage 235BHP
Mazda Rx8 Type S 246BHP garage 248BHP

Is a 1-2hp difference really that relevant?

 

[Stephanos82]

Is a 1-2hp difference really that relevant?

You are missing the point of this thread! Furthermore, it's way more than 1-2 bhp for some cars!

 

[Sage Ages]

You are missing the point of this thread! Furthermore, it's way more than 1-2 bhp for some cars!

I do see the point of the thread, I am just asking about a select few cars.

 

[YZF]

What?

Are you genuinely trying to say that if the gearbox loses 30hp at 300hp crank and you tune the car up to double that power it'll still lose 30hp?

Yes. Because the gearbox is the same, and friction inside it is the same (assuming that internal rotation speed is the same, i.e. rpms do not change twice).

Only it doesn't... Parasitic losses eat a percentage of the power supplied to them - that's why efficiency is measured in percentage!

It can be measured in anything you want, but most likely in the power (resistance power), e.g. Nm. Percentage is just a way to achieve this number.

As I said previously, if you think so, that's not a proof. It's just your opinion.

For example the tyre-to-road resistance or aerodynamic resistance will also remain the same, no matter what engine power the car will have. Even if this resistance can also be measured as percentage, someway, somehow.

The rest of that post makes clear that it's in real life and then adds the reasons why it won't do that...If you can't be bothered reading all that again:

Real car geared to 211mph
Real car runs out of power at 198mph

So it does but it doesn't? What?

Anyway, the answer is that (in real life) M5 will not hit rev limiter in top gear. It will not have enough power to do that.

In GT6, though, most of the time all those sports cars will start bouncing of the rev. limiter like crazy, or achieve speeds that are possible only by having extra 200-300 (or more) HP.

Huge mistake by PD and ofcourse nowhere near "Real Driving Simulation"

 

[Sage Ages]

Yes. Because the gearbox is the same, and friction inside it is the same (assuming that internal rotation speed is the same, i.e. rpms do not change twice).

He just explained why you're wrong. It's a percentage, not a set amount.

 

[DrkPhnyx]

He just explained why you're wrong. It's a percentage, not a set amount.

This always bothered me too. I always thought that if you hooked a torque wrench up to some component (output shaft, drive shaft, axle/wheel, whatever) you'd get an absolute measurable amount of friction/drag. And sometimes you can have, based on the % calculation, some absurd amounts of hp loss through the exact same drive train when you apply forced induction or nitrous.

(@YZF ->) However, that's thinking about static loss, not dynamic. Dynamic will result in greater inertia of components to overcome, and increased heat generation, so it will result in greater HP absorption afterall. (meaning that xHP loss at yHP crank levels, will not remain x at 2y crank levels)

However, the %s thrown around are all wrong too. It's nearly impossible to back calculate based on any fixed number, unless you run the engine on a stand dyno, then install it and put the car on rollers. (then repeat both steps if you add power)

So it IS a percentage (and not a fixed #, it will increase with increased engine output), but not necessarily a fixed percentage. And not something you can apply to all cars of a type (eg - rwd, etc).

 

[Sage Ages]

Never said it was a fixed percentage either. Just a percentage.

 

[ImaRobot]

Yes. Because the gearbox is the same, and friction inside it is the same (assuming that internal rotation speed is the same, i.e. rpms do not change twice).



It can be measured in anything you want, but most likely in the power (resistance power), e.g. Nm. Percentage is just a way to achieve this number.

As I said previously, if you think so, that's not a proof. It's just your opinion.

For example the tyre-to-road resistance or aerodynamic resistance will also remain the same, no matter what engine power the car will have. Even if this resistance can also be measured as percentage, someway, somehow.

The fact of the matter is that the percentage will always stay relatively the same, what is changing is what the percentage equates to in terms of HP. 15% of 300 is 45, 15% of 600 is 90. This is exactly why you're calculations are wrong. Guess what, its not an opinion, either, its just math.

 

[Famine]

Yes. Because the gearbox is the same, and friction inside it is the same (assuming that internal rotation speed is the same, i.e. rpms do not change twice).

No. The "friction" doesn't require a set amount of power to overcome. It scales with power (well, torque, actually) because the "friction" scales with power. Friction is thermal energy loss and the more energy you put in the more thermal energy you lose. It's not an absolute value, but a percentage of what is put in.

The ratio of energy in to useful energy out is called efficiency and efficiency is measured in percentage.

For example the tyre-to-road resistance or aerodynamic resistance will also remain the same, no matter what engine power the car will have. Even if this resistance can also be measured as percentage, someway, somehow.

Tyre-to-road resistance scales with weight - it's about 0.135% of the car's weight (and that weight includes any downforce, since weight is a force downwards). Aerodynamic resistance scales with speed - it's a cube of the speed. Neither is an absolute value.

So it does but it doesn't? What?

How can you post this and then this next line?

Anyway, the answer is that (in real life) M5 will not hit rev limiter in top gear. It will not have enough power to do that.

You're clearly getting it, but then clearly not at the same time.

Let's start over.
IF you can spin the E60 M5's engine as fast as it can go in top gear it will stop accelerating at 211mph because it runs out of revs to give. It cannot spin any faster than that. This is the geared limit.
BUT you can't do that because the E60 M5 doesn't have enough power to reach that speed. It has enough power to reach 198mph, assuming that peak power is available at that road speed (handily it is). This is the aerodynamic limit.

What a car is geared to and how fast it can actually go are not the same thing - a C6 Corvette is geared to something ludicrous like 270mph, but it is aerodynamically limited to far, far less than that.