The power loss with altitude thread.

[bergauk]

@Dancardesigner: What makes it different is the fact that its not something Steve wants, its just pointing out what should have been done already. Although I'm sure he wants it to be included. It isn't exactly a wish.

 

[dancardesigner]

Performance points will just change depending on the track, go high alt and it will go down (at different rate depending on car, excluding electric which will be the same), add a tuning parts/setting section before race to make adjustments.

I hate the Performance points system anyway, I hope it's not used in the GT career mode.

So i take it that you would assume the power drop would be fixed throughout the race and not dynamic for tracks with large elevation changes?

I really do believe this would be much harder to implement than it sounds, otherwise why would it have not been done, PD has 150 employees, im sure one of them would have put forward the idea if it was easy to implemnt and not too hardware tasking which it shouldn't be, if it's ''that simple''. Also even if it was added, it would only be an unwanted drawback imo, it's not like damage or tyre wear, things that bring in new gameplay opportunities, it's merely a hindrence, which even further backs up my stance on this topic and thread for that matter.

 

[JDigital]

Well, you guys are thinking about the wrong tracks I think. Obviously on a circuit like Suzuka or even the ring, elevation really doesn't change enough to make a noticeable difference... but what about rally tracks or sprints? Like the OP mentioned, if they bring back Pike's Peak where there is a 6000ft elevation change, do you go with the faster NA car to get an advantage in the beginning or would you run a "slower" FI car to make it up in the end kinda thing... little extra strategy thrown in there.


And as far affecting every car differently, it really would just come down to NA or FI. And its not like 11-20% really distorts everything if the other person lost 8-14% also...

 

[dancardesigner]

Well, you guys are thinking about the wrong tracks I think. Obviously on a circuit like Suzuka or even the ring, elevation really doesn't change enough to make a noticeable difference... but what about rally tracks or sprints? Like the OP mentioned, if they bring back Pike's Peak where there is a 6000ft elevation change, do you go with the faster NA car to get an advantage in the beginning or would you run a "slower" FI car to make it up in the end kinda thing... little extra strategy thrown in there.


And as far affecting every car differently, it really would just come down to NA or FI. And its not like 11-20% really distorts everything if the other person lost 8-14% also...

Actually that's a good point, i take back my statement of it bringing in no new gameplay opportunities, but i still maintain it would be hard to implement, complicate matters and i don't think we will see it in GT5.

 

[Jay]

So i take it that you would assume the power drop would be fixed throughout the race and not dynamic for tracks with large elevation changes?

No I don't want it fixed, I had Eiger in mind considering it was a example which is fairly fixed. As for tracks that have large elevation changes within the same track then thats part of the strategy just like in pikes peak hill climb, you can't have every car even for every track and situation by changing numbers around thats just silly. Just like I wouldn't expect my RWD car to be competative to a AWD car on a dirt rally.

I am all for deep tuning, like fitting NA cars with turbo or superchargers to suit the conditions, much like you could tune the Holden Commodore in GT4 with NA or Supercharged.

 

[Raitziger]

If there is a pikes peak hill climb this should be counted.

 

[albteman015]

It would be nice but it can't be done because thinner air does not affect just engine power. It also affects aerodynamics and the actual sound of the car believe it or not. Not to mention these stats are going to be different from car to car. Maybe in one of the next gt games. Not to mention many people are going to think there is a glitch in the game because they wont be able to understand the physics.

 

[chepe371]

I hope it's not used in the GT career mode.

Oh oh oh...don't say THAT, you're going to wake IT up.

 

[dancardesigner]

Oh oh oh...don't say THAT, you're going to wake IT up.

Care to elaborate

 

[Mooman117]

Naturally aspirated cars would not all be affected the same either. Most modern fuel injection systems continually vary the fuelling based on sensor data from the exhaust. So if there is to much uncombusted fuel (as you would get at higher altitudes) they adjust to minimise the effects. Carburettors can't do this and need to be manually balanced to adjust them, which is quite time consuming (mini game anyone). So cars with carbs would suffer much more if left at a sea level tune.

I think this is a perfectly valid thread IMHO. How many race teams do you see pumping up tyres by hand?

 

[dancardesigner]

Naturally aspirated cars would not all be affected the same either. Most modern fuel injection systems continually vary the fuelling based on sensor data from the exhaust. So if there is to much uncombusted fuel (as you would get at higher altitudes) they adjust to minimise the effects. Carburettors can't do this and need to be manually balanced to adjust them, which is quite time consuming (mini game anyone). So cars with carbs would suffer much more if left at a sea level tune.

I think this is a perfectly valid thread IMHO. How many race teams do you see pumping up tyres by hand?

Lol, that was just a bit of banter, lmao

 

[yeti]

Here's a question...

In Kenya (which is quite high) they only sell higher octane petrol (I believe the same is true in the Alps too) - to minimise the affect of higher altitudes...

Should this be taken into account? - Or do we always use high octane fuel in racing?

C.

 

[dancardesigner]

Here's a question...

In Kenya (which is quite high) they only sell higher octane petrol (I believe the same is true in the Alps too) - to minimise the affect of higher altitudes...

Should this be taken into account? - Or do we always use high octane fuel in racing?

C.

I think all race fuel is high octane, unless it's something like banger/campervan racing lol.

 

[niky]

I think we'll have to assume everyone not driving a diesel is on 100 octane... many of the race cars won't take any less.

Naturally aspirated cars would not all be affected the same either. Most modern fuel injection systems continually vary the fuelling based on sensor data from the exhaust. So if there is to much uncombusted fuel (as you would get at higher altitudes) they adjust to minimise the effects. Carburettors can't do this and need to be manually balanced to adjust them, which is quite time consuming (mini game anyone). So cars with carbs would suffer much more if left at a sea level tune.

I think this is a perfectly valid thread IMHO. How many race teams do you see pumping up tyres by hand?

This touches upon another thing, also...

Turbocharged cars are not all affected the same, either. Modern systems use Manifold Absolute Pressure sensors to continuously vary the amount of boost to make up for atmospheric conditions. In other words... while older turbocharged cars might lose less power at high altitude... newer ones might not lose any power at all.

And heat-soak would be a nice variable to add to professional mode, also.

Polyphony Digital has already touched upon the issue of variable engine performance with the implementation of oil degradation and engine wear in GT3 and GT4. While it may not be simple to add pressure and temperature induced changes in power, it's certainly possible to make approximate guesses on the effects on different engines and add the calculations to the physics engines.

(One hopes, of course, that they will recognize that these effects will be less on engines that have forced induction added to them, even if they're NA, or that "chipped" engines will suffer less from such issues)

 

[Sturdy]

I don't see how it will make PP calculating that difficult.

PP is just going to be an equation, and somewhere in there will be the horsepower figure.

Let's assume it was just p x w = PP (power x weight = PP)

All they need to do is add in the altitude multiplier for that type of car (NA, Turbo, Supercharger etc.)

So it would just become (where a is the altitude multiplier)

(a x p) x w = PP

Not complicated at all. As mentioned previously, thinner air will affect aerodynamics etc. as well, but I'm not convinced PD would need to pay that much attention to that, as that would surely be uniform for all the cars.

 

[lucag120]

OK, If GT is going to take this into account it will also have to include:

-Tyres blistering/graining
-Brakes overheating
-Loss of Downforce when following other cars closely
-Ect.

but even if GT includes this power loss due to the density of the air it will not add anything to the game that these options above can do. I think its a negligible point that will not add anything to the game. I'd rather the extra lines of programming go toward making windscreen wiper visuals look awesome when its raining or when you get oil on your windscreen......

 

[Marf]

concept is right, but in a game?

 

[Gotturbos?]

It appears as though many of you don't deal with turbocharged cars

This "altitude correction" for forced induction cars as explained in the first post is completely wrong. No offense. The correction is "outdated" you could say. It doesn't take 24psi of boost at xxxx elevation to make the same power as 18psi at sea level, and I'll tell you why:

Whatever means you're using to control boost is simply reading pressure. It doesn't matter if you're in space or at the core of the earth, 1psi is 1psi. So... say you take a turbocharged car at sea level running 18psi and its making 500hp, great. Move it up to 5000ft elevation now. This will work with any number but we'll use 18psi just for kicks. Now... your boost controller (or just wastegate spring if you're not using a bc) is going to be set to maintain 18psi of pressure, it reads this pressure from within the system, and doesn't care what the outside pressure is. So the only thing lowering the outside pressure will do is making the turbo work just a tad harder to get 18psi but not really change the peak power that much. Its only changing where you are on the efficiency map for whatever turbo you may be using. If you were to say "oh well the car is tuned for sea level and where I am is 4 psi less than sea level, so I'll just raise the boost 4psi and I'll be good" you would end up running way to lean and probably blowing your motor

That is a pretty vague description of why it doesn't work, but you guys should understand it. I'll try and clarify more if you need it... when its not almost 4am in the morning!

Jon

 

[dancardesigner]

I don't see how it will make PP calculating that difficult.

PP is just going to be an equation, and somewhere in there will be the horsepower figure.

Let's assume it was just p x w = PP (power x weight = PP)

All they need to do is add in the altitude multiplier for that type of car (NA, Turbo, Supercharger etc.)

So it would just become (where a is the altitude multiplier)

(a x p) x w = PP

Not complicated at all. As mentioned previously, thinner air will affect aerodynamics etc. as well, but I'm not convinced PD would need to pay that much attention to that, as that would surely be uniform for all the cars.

You shouldn't use an assumption to back up your argument, and anyway if you were using the variables power and weight it should be power divided by weight for correct performance values.

Yes the aerodynamics would stay constant for all cars, but the pp increase/decrease for alterations to wing/spoiler settings would have to be different for different elevations meaning that the PP would therefore not be constant for a particular car on all tracks. This complicates matters and would make the sorting of cars via PP useless.

 

[Punknoodle]

Great idea, but lets not run before we walk - the GT series does not even incorporate things like brake fade yet - and to be completely honest, that is more of a relevant issue, since most race tracks go through stuff all elevation changes, but production vehicles will experience massive brake fade after just a few laps with standard brakes.

Another thing that I'd say is more relevant in terms of induction charge is the temperature - if PD are to incorporate Day/Night cycles then realistically your vehicle should perform much better at night then during the day due to lower intake temperatures. Again, this is more relevant I think as it happens at every race track, not just the ones with massive elevation changes.

So I think that power losses from altitude, whilst realistic, is something that I imagine is down the list compared to some of the other dynamic effects that PD should be working hard to incorporate into their driving simulator.

Just my 2c.

 

[Sturdy]

You shouldn't use an assumption to back up your argument, and anyway if you were using the variables power and weight it should be power divided by weight for correct performance values.

Well as I don't know what the actual equation is that they use, how can I do anything but assume? Maybe I should have just used the word pretend.

May I reassure you I don't for one second think that the calculation is a) that simple, or b) a multiplication of power x weight as you correctly corrected me on, as that'd make no sense at all. 👍

Yes the aerodynamics would stay constant for all cars, but the pp increase/decrease for alterations to wing/spoiler settings would have to be different for different elevations meaning that the PP would therefore not be constant for a particular car on all tracks. This complicates matters and would make the sorting of cars via PP useless.

I was initially going to disagree slightly here that the difference in aerodynamics would be the same for each car, so the amount the PP differed would be constant.

Having actually given it some thought though, you are of course correct, as a car may derive most of its PP from having lots of aero let's pretend, which would then of course be less useful at high altitude, so that vehicles PP would drop more at altitude than say a vehicle whose PP was more influenced by being light weight.

In summary, having thought about it I agree with you, thank you sir

 

[Pupik]

Not going to happen, close thread

We will decide that...not you.

 

[sesselpupser]

So I think that power losses from altitude, whilst realistic, is something that I imagine is down the list compared to some of the other dynamic effects that PD should be working hard to incorporate into their driving simulator.

I agree that brake fade and some other factors are more important, I think the altitude issue is going to be important if there's any hillclimb events such as Pikes Peak, since that's the whole reason Pikes Peak cars are the way they are - massive horsepower, even bigger wings, and completely insane. Without the altitude issue, you could take a standard looking Skyline with 1000+bhp, add a wing like you could in GT4, and somehow be competitive against this

.

In other words, it won't exactly be the most convincing thing, and as far as I'm concerned, would make including Pikes Peak pointless. Unfortunately, it seems as though that just means they won't put it in rather than realistically mapping the effect of altitude on engine power outputs...

 

[Stevisiov]

It appears as though many of you don't deal with turbocharged cars

*snip*

Jon

Yes Niky brought that up too, the calculations I used in the first post is for a specific type of turbo, one which adds a specific amount of pressure to a system, the turbo you speak of aims to achieve an absolute intake pressure, so if air pressure drops the turbo fan spins faster to compensate, assuming it can still maintain efficiency.

So in this lets say the new turbo still adds 10psi of boost at sea level, intake pressure is 24.7psi

However at Eiger where air pressure is 11.8psi the turbo will add 12.9psi to the system to maintain a constant intake pressure of 24.7psi.

I agree, essentially in this situation the turbo doesn't loose power (although will take longer spooling at high altitude).

Either way PD program should program it appropriately, I would be almost certain that PD already have all the information required from the manufactureres to simply program what is a fairly simple relationship. 👍

You shouldn't use an assumption to back up your argument, and anyway if you were using the variables power and weight it should be power divided by weight for correct performance values.

He wasn't really assuming, rather using a hypothetical situation to help explain the direction he is coming from, one I actually agree with.

Yes the aerodynamics would stay constant for all cars, but the pp increase/decrease for alterations to wing/spoiler settings would have to be different for different elevations meaning that the PP would therefore not be constant for a particular car on all tracks. This complicates matters and would make the sorting of cars via PP useless.

Somewhere in PD's massive physics code there will be something which designates what level of downforce and drag causes a certain multiplier in PP. The changes in downforce and drag levels don't affect this, rather read a lower multiplier.

Putting it another way, when PD designed their drag model, somewhere in there should be a density of air variable (or could be constant if they are being lazy). All that really is required is a new value for the density of air which is appropriate for that altitude, and the PP will rise or fall as a result.

Great idea, but lets not run before we walk - the GT series does not even incorporate things like brake fade yet - and to be completely honest, that is more of a relevant issue, since most race tracks go through stuff all elevation changes, but production vehicles will experience massive brake fade after just a few laps with standard brakes.

I completely agree that brake fade is another important aspect of the physics engine which needs to be addressed, there are lots of areas which PD could improve upon, I personally feel PD should try and address as many as possible.

Another thing that I'd say is more relevant in terms of induction charge is the temperature - if PD are to incorporate Day/Night cycles then realistically your vehicle should perform much better at night then during the day due to lower intake temperatures. Again, this is more relevant I think as it happens at every race track, not just the ones with massive elevation changes.

That's not strictly true, its likely the car will perform better during the day although of course it depends on all sorts of factors. While the temperature drop means denser air and thus more power, the car also has to shove denser less viscous air out the way also. Perhaps more importantly the warmer temperatures can potentially make a great deal of difference in terms of tyre grip, depending on the tyres operating temperature.

When you look at endurance races, the fastest laps tend to be set during the day but the night time stints actually make up more time because the tyres last that extra stint. I have made a weather/night thread in the past because of the added strategy it brings to long races, I certainly don't doubt how much realism it could bring to the table, I felt altitude was another important factor, so I decided to make a thread on it too.

So I think that power losses from altitude, whilst realistic, is something that I imagine is down the list compared to some of the other dynamic effects that PD should be working hard to incorporate into their driving simulator.

Just my 2c.

I am personally hoping PD will make a large jump with regards to physics accuracy for GT5 I don't think we should limit ourselves to just a few physics improvements, if its a perfectly valid improvement then PD should aim to incorporate it. I agree they can't do everything, but I don't think this one is too much to ask.

 

[Jay]

Yes Niky brought that up too, the calculations I used in the first post is for a specific type of turbo, one which adds a specific amount of pressure to a system, the turbo you speak of aims to achieve an absolute intake pressure, so if air pressure drops the turbo fan spins faster to compensate, assuming it can still maintain efficiency.

So in this lets say the new turbo still adds 10psi of boost at sea level, intake pressure is 24.7psi

However at Eiger where air pressure is 11.8psi the turbo will add 12.9psi to the system to maintain a constant intake pressure of 24.7psi.

I agree, essentially in this situation the turbo doesn't loose power (although will take longer spooling at high altitude).

Either way PD program should program it appropriately, I would be almost certain that PD already have all the information required from the manufactureres to simply program what is a fairly simple relationship. 👍

Which covers pretty much all semi-modern wastegated and boost controlled (air pressure controlled wastegate) turbo engines you see, many older turbocharged cars like 70's BMW 2002 turbo are the exception.

 

[Grandi]

I think modeling power loss is a great idea. The more technical things get, the better

 

[Gumuz]

I know GT is a simulator, but i think this is taking it abit too far

 

[JDigital]

It appears as though many of you don't deal with turbocharged cars

This "altitude correction" for forced induction cars as explained in the first post is completely wrong. No offense. The correction is "outdated" you could say. It doesn't take 24psi of boost at xxxx elevation to make the same power as 18psi at sea level, and I'll tell you why:

Whatever means you're using to control boost is simply reading pressure. It doesn't matter if you're in space or at the core of the earth, 1psi is 1psi. So... say you take a turbocharged car at sea level running 18psi and its making 500hp, great. Move it up to 5000ft elevation now. This will work with any number but we'll use 18psi just for kicks. Now... your boost controller (or just wastegate spring if you're not using a bc) is going to be set to maintain 18psi of pressure, it reads this pressure from within the system, and doesn't care what the outside pressure is. So the only thing lowering the outside pressure will do is making the turbo work just a tad harder to get 18psi but not really change the peak power that much. Its only changing where you are on the efficiency map for whatever turbo you may be using. If you were to say "oh well the car is tuned for sea level and where I am is 4 psi less than sea level, so I'll just raise the boost 4psi and I'll be good" you would end up running way to lean and probably blowing your motor

That is a pretty vague description of why it doesn't work, but you guys should understand it. I'll try and clarify more if you need it... when its not almost 4am in the morning!

Jon

You're overlooking the fact that there is less oxygen at higher altitudes. 24psi at sea level contains much more oxygen than 24psi at 10000ft.

 

[Jay]

There is less oxygen because the air is less dense, pressurise the air back to sea level (roughly 14.7psi) and you have the same oxygen, the oxygen percentage doesn't change but the density does. This is why planes can pressurise the cabin (never to sea level usually around 9000ft agl) and you have adequate oxygen to breathe.

(There are other factors involved like humidity/moisture, but I don't expect that modelled)

 

[WolfRacer543]

There's a lot of half truths and incorrect physics going on in this thread But that aside...

What's the point in modelling altitude's affect on aero and power if the affect of temperature isn't taken into account?

Forget altitude, lets just talk about the same altitude but different temperatures. This will vary engine performance as well as Aero. Aero depends on density which in turn depends on temperature and pressure. A couple of months ago I was doing some wind tunnel testing and from the start of the day to the end of the day the density could vary around 3 to 4%, and that's within a room, not outdoors (its a closed loop wind tunnel but its an open test section).

Going from one track to another with wildly different temperatures and humidities will massively effect tires, which on will affect suspension, it massively affects engine performance, it can also easily affect aerodynamics by several percent (given that many of the aerodynamic devices on race cars will only affect aero a percent or two anyway). That's all without changing altitudes at all.

Lets also bring in cross winds which can totally screw things up