Physics

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Project CARS: Addressing expectations on realism and simulation

This is not a FAQ. This is not a guide. During the development of Project CARS queries and realisations were made in discussions between the WMD forum members and the development team. What emerged was evidence that reality – as simulated in Project CARS – doesn’t always align with common expectations.

The idea here is not to provide all the answers, but to present the information and evidence from the development of Project CARS that challenged our assumptions and expectations, so that when you find something that might not seem right you’ll start asking questions, looking for information and delving further into the wonderful world of motorsport and the complex reality of driving dynamics that don’t always make sense when pushed to or designed for the limit.

The information here is focused mostly around driving dynamics and racing structure and is paraphrased from the actual conversations on the forum, but as it isn’t a FAQ or guide you are free to absorb the information as you like.

Further reading suggestions:

How to Drive - Ben Collins

Driving on the Edge - Michael Krumm

Monocoques & Ground Effects - János Wimpffen

Speed Secrets - Ross Bentley

Contents

KERS

What's with the LMP KERS system?

The KERS system works on % throttle pedal input, not on a button. This is per real life regulations


Why does KERS charge up even when I'm not braking?

This is due to the trickle charge from the battery, a real world effect.



PHYSICS

My MP12c-GT3 seems to be underperforming at this track!?

Traditional internal combustion engines run on a mixture of atmospheric air and fuel. The air density (the amount of air molecules per unit of volume) is related to atmospheric pressure via the ideal gas law, which states that if e.g. temperature and volume are kept constant, air density drops as atmospheric pressure drops. Note that atmospheric pressure drops as altitude above sea-level increases, which implies that the air density is lower at higher altitudes.

Now, turbocharged engines are per design able to make the same amount of power almost no matter the altitude; they basically just maintain their absolute boost level by spinning the turbo faster to compensate for the outside loss in atmospheric pressure, which means that the maximum amount of air+fuel mixture going into the cylinders will remain roughly constant from sea level and up. In contrast, naturally aspirated engines lose power at higher altitudes because the outside atmospheric pressure (or air density) dictates how much air can be sucked into the engine cylinders during each intake stroke, which in turn means that there is less air+fuel mixture to burn per power stroke at higher altitudes. Therefore a GT3 car with a naturally aspirated engine may be more powerful than a GT3 car with a turbocharged engine at lower altitudes but less powerful than the same turbocharged GT3 car at higher altitudes due to the loss in atmospheric pressure alone.


How is air temperature and density modeled?

It is all figured in real time according to your time acceleration settings and position on the track. Neither temperature nor pressure are locked in when you leave the pits.


I'm not seeing tyre wear?

Tyre wear is by default not scaled and will degrade at real world levels, i.e. you will likely get a full fuel stint out of even the softs in endurance categories. You can adjust it up to 7x in Multiplayer, but it will not be accelerated as much as the weather and race length can be, to save you destroying your tyres before the pits on lap 1...


The car loses all grip after a number of laps!

You're likely cooking the tyres, slow down a bit. Check the telemetry to see how the tyre heat is working as you race.


Some cars have too much grip, I can't get the back out?

The default setups are designed to allow maximum control and ease of use, especially given the large number of gamepad users. You can adjust setup to increase oversteer, the WMD forum even ended up with a section with recommended and user created setups. Note: See Jussi for OEM setups

Also, the default compound for most race cars is the SOFT slicks, so you're getting the highest grip tyre out of the box. Of course you may need to select a different compound depending on the weather, time of day, length of race and wear scaling (MP) in use.


Why can't I do burnouts in the GT3 cars!?

There are actually a number of factors. While the GT3 cars produce a lot of power, this does not mean the tyres are not up to the task of transferring all of that power to the ground and maintaining grip! The GT3 cars in Project CARS have Soft Slicks equipped in default configuration. Also, the GT3 tyres are pre-warmed in all racing sessions in game, so even starting Free Practice your tyres will be sitting at 90ºC. Another factor is the race track material itself and track temperature, which can create extra grip to help the tyres stick (look up track rubber build-up). There are a couple of other things to check or change if you really like doing burnouts rather than getting the most grip from your tyres!: Firstly, shorten the gear ratios if possible (this has a greater impact than you might think!), Check that Traction Control isn't enabled. Set the differential to 100% accel lock. Change compound to Hard. Or just drive around a lot so your tyres either overheating or worn and slippery! Race cars are designed to get off the line quickly and run at high speed most of the time, not waste precious rubber.


This car has no power!?

Some cars in the game have a small engine with a large turbo, so you need to keep the turbo spooled to keep up the power, try changing down an extra gear or keeping some throttle on during cornering (I.e. GRP 5 cars).


Throttle response feels laggy

That's because Project CARS uses a simulated volumetric throttle model. It will probably feel more ‘analogue' than you might be used to virtually. This is real world behaviour, in contrast to the "x% throttle pedal input = x% engine RPM" physics that is common in racing simulations/games. This also means that each engine/car has a different throttle response. So all cars will feel and respond differently on the throttle, which adds a lot to the (sub-)conscious character you'd get from each car.


I can't match real world times for this car?

Those real life times may be from qualifying with max boost. Up the boost in the car setup, but don't expect the car to last long (just like real life! - Lotus 98T, Sierra, etc.). Other factors include: simulated tyres are ‘perfect’ in condition and structure compared to real life, especially for historic cars, virtual tracks are smoother and of consistent surface material, tracks are changed in real life all the time, tyres compounds vary in capability between manufacturers, you’ll take more risks virtually, car setups are tuned per track and for conditions in the real world, which may not match the conditions you are using, etc. There are a lot of factors to consider!


This car feels different than before

Check the following: time of day, location, track temperature, compound selected, assists, amount of fuel. Also, the tyres a pre-heated at different levels depending on the session you are in. For Free Practice, you start with cold tyres. Qualifying they are pre-warmed, Race session also pre-warms them. For Time Trial mode, the tyres are pre-warmed to 'optimum' temperatures, i.e. sets them up as though you've been lapping getting ready for the 'ultimate' lap. During a race rubber will also build up and so your fastest laps may end up better than Time Trial even though the track conditions haven't otherwise changed. Check the telemetry HUD to see the differences


Why are my testing times slower than those in the race while everything else remains equal?

Track activity builds up tyre rubber during events IRL, which adds grip. A 'rubbered in' track is faster than a clean, "green" one. In pCARS, the racing surface on race day can end up with 3-4% more grip than on test days! Of course if it rains that will remove the extra rubber build up to an extent, so beware.


My lap times change a lot driving in the rain

Project CARS models real world wet weather behaviour. You will see 'drying lines' appear as cars remove water from the track. You'll have to manage tyres so that if you have wet tyres and the track starts drying out you'll need to drive off the racing line to keep temps down. There's far more to the dynamics of driving in the wet so further research is encouraged!


Some cars are really hard to drive in the wet!

This is likely because the default setups are designed for the dry track. There are setups changes you might need to make, especially in the really stiff race cars like the FA. Start with things like increasing the ride height, softening the suspension and reducing camber and again start researching because effective real life changes will be just as effective in Project CARS.


Boost pressure appears to be displaying wrong in the gauges?

Boost pressure is measured at the plenum in the manifold and correct for that.


Can't see brake glow on the Formula A or some LMP cars?

The brake discs are fully enclosed, it is a common approach in the real world with the modern race cars.


The car keeps leaning slightly under throttle?

the inertia of the engine is causing that. When you step on the gas the crankshaft accelerates in one direction, which causes a reaction in the opposite direction. Apparently most engines rotate clockwise (when looking from the front of the car), which makes the car lean counter clockwise. This should happen if the car has a longitudinally mounted engine. If the engine is mounted sideways the car should lean front or back slight when revving. If the effect is strong enough, it can even lift the inside front tyre off the road, which will happen in the game with for instance the Boss Mustang (try it!)


I can't wreck the brakes?

Brake wear rates are per real life, you will need to really abuse them in an endurance session to do proper damage, but the damage is there.


I can't keep the tyre temps up!?

You might not be using the downforce enough. Some tyres rely on downforce to get the heat into them, but it requires you to 'trust' it through corners. Also, check the track temperature and select a suitable compound for the conditions or adjust tyre pressures.


This car understeers too much

Some cars have much wider tyres on the rear or the aero is rear biased (i.e. big rear wing). Adjust as necessary for your style, but beware for these cars it will be the same ‘problem’ that the real drivers had to adjust to. Not all cars are created equal.


I cannot draft the opponent ahead of me!

Project CARS uses real world values for drafting behaviour which some may initially find surprisingly low. But be careful as there is definitely enough drafting power that it can reduce braking and/or turn-in ability for aerodynamic-dependent vehicles.


Why do some cars have higher/lower fuel consumption even in the same Class?

Project CARS calculates fuel usage for each car based on car-specific factors such as engine aspiration (turbo vs. normal), aero efficiency and driver behaviour among others.


I can change gears without using a clutch!

Real racing gearboxes have a bit more tolerance around the 'ideal' shift range over road cars (road cars have some) that will allow you to straight shift without clutch. You will damage the clutch if you keep getting it wrong. Another case of modelling real world behaviour.


Tyre pressure seems a bit low?

This is the cold pressure. When you get on track the tyres heat up and the pressure increases, sometimes up to 10psi or so. Project CARS models this behaviour


Why do I spin out immediately when flooring the throttle, coming out of the garage?

That's how cold tyres (don't) work. Take it easy for one or two laps to get same heat into the rubber, and only then start pushing hard(er). Be aware Free Practice starts you without pre-warmed tyres in most cars (they're warmed though for some). For Qualifying, Race and Time Trial modes, the tyres are pre-heated.


The Formula A feels like on rails!

The FA comes with standard tyre warmers in your favourite colour, so it has maximum grip right from the start. And a Formula A car is a very expensive machine exclusively designed and constructed for maximum grip under all circumstances. You have to push hard to make it come loose. But be prepared that it will bite you when it does...


The car keeps trying to snap out under brakes after a while?

This could be because there is a large difference in temps between left and right side tyres. If the track has mostly left or right corners there is high potential for this to happen. You would need to adjust the tyre pressures (among other options) to even out the heat...or drive slower.


The Boss Mustang keeps pulling to one side on acceleration?

The Mustang (among others) utilizes a live rear axle with a panhard bar. Due to this suspension configuration, the car will actually pull slightly to one side under hard acceleration. To eliminate this pull, 'wedge' can be dialled in, but this is a compromise in that dialling in enough wedge to offset the pull under acceleration will typically make the car pull in the opposite direction when coasting or braking. The exact amount of the effect depends on your throttle %, gear ratio used, setup, and other stuff so it is hardly a constant effect. pCARS not only has some wedge modelled to counter this (doesn't completely remove it in lowest gears), but also dynamically determines the Roll Centre from the resulting angles.


When my car is standing still, if I turn the steering wheel from side to side the nose seems to go up and down... What's going on?

That's the jacking effect of the front suspension caster angle alignment


I'm not noticing any brake fade on the road cars. Shouldn't this happen like real life?

Project CARS actually simulates iron, carbon and ceramic brakes of various configurations. But in game the road cars are specified as if they were slightly track-prepped for the brakes. 99% of road car brakes are complete toast after only a few minutes of hard driving and representing this faithfully would quickly become a frustrating experience. Imagine that the cars have been modified with better brake-pads/-lines/-fluid and maybe a little bit of extra cooling to allow them to be just that little bit more suitable for being tracked hard.


Why did my engine suddenly give up during the race?

Project CARS has detailed simulation of engine heating & cooling systems so you will need to monitor your water and oil temperatures during a race. The default radiator settings should be sufficient for most race conditions but for extremely hot races (or if you manage to damage your radiator) you will need to monitor these temperatures via MOTEC display pages or warning lights on the dashboard instrument cluster. If your temperatures are rising near or above 100 degrees celsius, you may have to reduce throttle usage (more coasting and/or lower rpm shifting) to bring the temperatures within normal operating levels. Immediate repair work is advised, as prolonged high temperatures will destroy the engine and your race! You can increase the radiator opening for increased engine cooling in the car tuning menu but you will incur increased drag and therefore lower top speed as a result.

SETUP

Why such limited gear ratio options?

Provided as per real world homologation regulations, blame Real Life™


Adding rear downforce on the C9 Sauber seems to have the opposite effect, broken?

Adding additional rear downforce actually enhances the underbody air effects, creating in turn more front downforce. This is real world behaviour.


Why does the SLS-GT3 have such long gearing, 6th is practically useless!

It's like that in the real world too.


Minimum wing downforce means no downforce, right?

No, minimum downforce is just the setting of the particular wing that will provide the least downforce. It may actually create 0 downforce, but adjusting the ride height or things that affect it (tyre pressure, camber, suspension) will also change the downforce and so in pCARS the real number is dynamic around the wing setting.


Why do some cars have smaller/larger fuel capacities even in the same class, is that a mistake?

These differences (and others) have been carefully modelled after their real world racing series homologation (e.g., FIA GT3) or manufacturer factory specifications.



FORCE FEEDBACK

FFB doesn't feel right?

Here's a guide to tuning the FFB settings in game *link* or you can use the in-game help text. Or here's some recommended community settings *link*. Also note the FFB is derived directly from the physics, so changing the car setup will affect FFB (i.e. caster, camber, tyre pressure, etc.). Everyone loves options!


My FFB wheel is shaking at times!

You probably locked up the wheels while braking and flat spotted a tyre. The stronger your FFB settings, the more this will be enhanced. It is derived from the physical tyre model. If you have shaking in other situations, check your FFB settings, there are lots to play with!


FFB keeps getting hit by something on wet track?

That'd be the standing water, you're aquaplaning. The physical representation may not be 1:1 with the visual puddles with the current tech (but it should be in the same areas), so use the FFB to help you know what's going on.


I can’t feel the kerbs?

The kerbs are physically modelled, so if the kerb is rather flat in real life you won't feel much in the FFB.



OTHER

The cars are impossible to drive, I can't get round a single lap without constantly crashing!

You're going too fast; pCars is a simulation so you need to drive with a real-life attitude. Start slow and build your speed as your confidence grows. Use your brakes and learn the track, follow the AI for a few laps and let them show you the braking points, use the driving line, turn on driving assists. There's a lot available in the game to help you drive like the pros!


Why can't I choose more opponents at some tracks?

The number of opponents allowed at each track depend on the pit spaces available. This reflects real life where possible. Use Le Mans if you want them all.


Why are my tyres showing such high temperatures? A real tyre wouldn't heat up that much!

Check the units displayed. Imperial may be default, so the temperature may be showing in degrees Fahrenheit. Change to Metric in the in-game options as required.


The kerbs at Road America seem too bumpy!

They’re actually like that in real life too!


Why are the AI hitting me all the time?

The AI drivers in Project CARS are quite dynamic and modelled on real-life racing. They will try and overtake if you give them the chance, they will be defensive and they will give track position to avoid collisions to an extent. They are also inclined to follow the best racing line, so if your line is significantly different you might clash a bit. It's an opportunity to learn race craft, learn the lines, learn that trying to overtake everyone by the first corner does not provide the best racing, and that the AI will respect you properly if you show them respect too! You might be used to static AI that just obey these lines, so the AI in Project CARS will demand a bit more 'human-like' consideration.


I can't think, my head hurts?

Mind. Blown.