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Das Fun-DLC wurde mit folgenden Inhalten angekündigt:

Fun Pack DLC Contents

CARS

  • Audi Sport Quattro S1
  • Citroën DS3 RX Supercar
  • Renault R5 Maxi Turbo
  • Ford RS 200 Evolution
  • Audi EKS RX Quattro WRX
  • 1969 Ford Bronco 'Brocky'
  • Mustang RTR Spec - 5D
  • Mustang '66 RTR.

TRACKS

  • Circuit De Barcelona-Catalunya Rallycross
  • Brand Hatch Rallycross Historic.

Sehr geil, freue mich. Das Rallycross Zeugs macht unglaublich Spass

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Physics of the Japanese Car Pack DLC

Datsun 280ZX Turbo AAGT: You guys are gonna like this one; it’s a total hot rod. There’s not a ton of historical data for it as reliability issues kinda hindered its racing career, but we can look past that and just let it run strong as it did at its best.

AAGT was IMSA's take on Group 5-style regulations to get some new, interesting cars entered in the series. It allowed any engine to be installed in any chassis so long as they were from the same manufacturer. So here we have a 4.2L V8 from the Nissan President Limo, tweaked and tuned with the biggest turbo they could find. The lazy, 200hp road car engine ends up here with something in the range of 940hp@7500rpm when using full qualifying boost pressure of 36psi. It was good for 208mph at Daytona, fastest in a straight line in a field which included a number of Porsche 935 K3s.

Other than that, it wasn't the greatest car to be honest (hence the short racing career). Suspension is basic struts at the front and simple wishbones at the rear; nothing fancy but it makes for predictable handling. Power runs to the rear through a 5-speed Hewland and ZF-type clutch & plate differential; I expect they at least experimented with a spool to help put down the huge power in a predictable manner, like in the 935s. Aero additions with that massive bodywork on the rear end are mainly to help with high speed stability. I’m sure it was good for modest net downforce on the rear, but overall this thing was dominated by aero drag. Weight was 200kg heavier than a Porsche 935, so it didn't corner particularly well and it burns through tires quickly. But, man, is it a hoot to drive and it can hang pretty well on tracks that favor top speed.


Honda Civic Type-R: Nothing too fancy here other than being a well-polished FWD hot hatch design. It's a lot like the Megane RS275 with 30hp more and independent rear suspension, or like the A1 quattro with 50hp more and FWD only. Fun, fast little car. 310hp doesn’t sound like a lot these days, but it arrives in a useful manner and the 6-speed manual is geared so each ratio is properly spread for track use; no extra-long highway gear on this one. It is prone to the usual FWD behavior when driven hard and pushing the 235 rubber - a bit of torque steer, a bit more lift-off oversteer. Personal best here so far is a 7:53 at the Ring on sticky semi-slick tires, so that real world target of 7:43 is surely in reach for the faster drivers amongst you all.


Nissan Skyline GT-R BNR32 Group A: Godzilla, right? The fundamentals of this car are actually quite similar to the R34 we have in game. FIA’s historic database of old homologation forms was a valuable source of information in putting this one together.

Suspension uses a neat multi-link setup in the front where the steering axis is separate from the links which control bump/rebound motion. Sorta halfway between a strut, Ford's Revoknuckle concept, and a traditional double wishbone. Gives really compact packaging, 100% camber recovery, and a nice steering axis. Cool stuff. Rear is nothing unusual; just a fairly ordinary multi-link design with a lower A-arm. Again, same basic geometry shared with the R34 car.

Engine also has a lot in common with the R34’s RB26 2.6L-turbo straight-6 and is the real killer feature for the car. Early in its racing life, this thing was putting out over 600hp @ 3bar and just destroying the competition. That performance was pegged back somewhat with extra weight and intake restrictors, which is a method we’ve copied here. Two 33mm intake restrictors hold power to ‘just’ 490hp and is near max power in a range all the way from 6000rpm right up to the 8700rpm rev limiter.

Was generous in the aero model and gave it a bit of downforce (very small amount) with modest drag levels. Research showed most comments on the Group A version were that the front makes some lift and the rear wing gives good downforce to the rear, so expect a moderate amount of aero-induced understeer...on top of some mechanical understeer thanks to the strong front bias to weight distribution of 60%. The suspension setup compensates somewhat by being stiff at the rear to encourage low speed oversteer. Interesting combination which is apparently also used by few modern GT3 cars.

Cool thing about these Skylines is that they were, at the heart, RWD and the AWD system was computer controlled to engage a clutch in the center and lock the two axles together only when the rear axle started to lose grip and spin. Our model is set up the same way, just with simple friction and viscous clutch action mimicking all the electronic control in the middle. Funny thing is that Nissan tested the Ferguson system (as in the Lotus 56) early in development of the Skylines as it does mostly what they were after - no lock until axle speed difference is above some threshold - and the system they ended up making basically does the same thing, just with massively more dynamic control where the Ferguson system was fully passive.


Honda 2&4 Concept: Neat to see a concept car that truly works as designed! The reference material Honda provided had great detail of the suspension geometry - including spring and anti-roll bar rates - so that very little guesswork was needed in taking this from experimental concept to something that actually works on track.

Didn't pull any tricks in the suspension design from the CAD reference and it works quite well with the BAC Mono dampers. The simple chassis structure, known mass and known components made it easy to approximate weight distribution at roughly 53% rear and center of gravity height at a mere 30cm above ground without the driver on board. With driver, these number shift to around 53% rear and 28.5cm high thanks to sitting so low and far back in the car. Another neat finding is that the offset chassis and driver position combine to just about cancel each other out for any lateral weight bias. More signs of this as a radical yet functional concept. Nice one, Honda.

The RC213V is a pure MotoGP race engine, which usually brings about some uncertainty as to claims of power level and such, but this one was fairly simple to put together due to the customer versions of the same thing on the market. All research signs point to it being a very strong unit matching the claimed 220hp at 13,500rpm and a fat power band keeping it above 190hp for everything north of 10,500rpm. A VFR1200F DCT does the job of putting that power to the ground through too-skinny rear tires. I say ‘too-skinny’ because 220hp is a lot to manage(!) and, despite 56% rear weight, the rear rubber only has a 51.7% bias in width. It’s still a lot of grip and it is stupid fast - almost on pace with GT3 at Long Beach where top speed isn't vital - while rewarding smooth driving. Don't overcompensate in slides; it'll probably correct itself if you don't add more energy with big inputs. Really fun drive so long as you keep it smooth and let the car do most of the work. 

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Physics of the Fun Pack DLC

Ford Bronco RTR 'Brocky': Drivetrain for this guy is a classic off-road racer setup. Engine is a Ford Performance Z427 cranking out 600hp@6500rpm and 560lb-ft@5000rpm. Power goes through a stock TH400 three-speed automatic and transfer box to give either RWD or 4WD -- You can use the center ‘diff’ Spool to toggle this in setup. Spool=Yes for 4WD and Spool=No for RWD. The final drive ratio has a setting for the transfer box low range gear, but really this is only useful for rock crawling. There are also some optional TH400 gear ratio sets you can run, but the real thing is stock as is default setups with the 2.48, 1.48, 1.00 gear ratios. Typical differential setup Vaughn uses is a spool at the rear and ratcheting locker in the front.

We had the real Brocky scanned for art production and this proved ideal for drawing up the long-travel suspension geometry, even the 4-link solid rear axle works great over its 18" range of travel. The complete truck weighs in around 4500lb with about a 50:50 weight distribution. Motion ratios of the suspension mean it balance well with a 650lb/in front main spring and 200lb/in at the rear. Dampers are matched to some similar King units, but there is a big adjustment range in these things depending on the type of terrain being driven. We’ve gone fairly stiff and digressive for the rallycross tracks present in game, and that seems to work pretty well.

Thing is maximum fun at the RX tracks. It's about 4-5s slower than the RX cars, but being so big and changing direction so much more slowly makes it all feel like a real event as you slide around. It becomes a beast in RWD mode; not fast at all, but great at doing donuts and it drifts like a champ. It's neat how responsive it is to setup changes. You get something completely different with AWD, max ride height of 40cm and balanced anti-roll bars versus lowering it some, changing to RWD, and setting up the ARBs like a circuit racer. Very big toy truck.


Audi S1 EKS RX: This one was fun to assemble as Audi sent over some wonderful reference details. The suspension geometry - struts all around as usual - has some interesting anti-dive/lift/squat properties which combine with springs which are a bit stiffer than some other RX teams use. Set up with 400lb/in springs on all corners and big front anti-roll bar makes it handle almost like a soft, tarmac road course setup. That matches up pretty well with how we can see the chassis move in recent race videos. No complaints here; it drives great with all that information applied.


Audi Sport quattro S1: Great fun researching this car; it's famous enough and cloned enough that there is quite a lot of information for it on the web. The more you read about it, the more amazing it is that it worked at all! They basically started with an Audi 80 and kept cutting bits out of the middle until the wheelbase was only 2.2m to try and make the handling more nimble. That works in theory, but being an Audi you still have the engine slung way out beyond the front axle, so early homologation versions had horrible weight distribution like 62% front. Moving the cooling system to the rear and various other tweaks eventually helped get it to a 51:49, but all articles I've found still say that the chassis really works best if you are aggressive with it to get turn-in rotation.

Engine for the S1 version is generally described as peaky with quite a bit of lag, and that comes through here - and it makes sense when the dashboard gauge reads all the way up to 2.5bar (36psi) boost! It is a smooth 450hp, but you'll find yourself waiting a bit for the power unless you row gears and help hold it high in the rpm range. They even ran it a few times with Porsche's early PDK gearbox - also used in some Porsche 962C factory cars - to stay on boost better. It's neat, in some old videos you can clearly hear the difference in the PDK car shifting and how smooth that unit flows through geares. Impressive to think that our Audi 90 IMSA GTO is an evolution of this same basic engine 4 years down the line and it was then doing 700+hp with 10psi less boost. Turbo tech came on very strong in the '80s.

The early quattro system as in the race cars used a kind of planetary/Torsen/viscous combination center differential. It let them adjust fore:aft power balance, do some torque biasing on slip and still lock up if one end loses grip completely. Works really well when copied into our systems. Feels a lot more typical of AWD road cars than something like the modern RX designs and reminds me a lot of our time in the Subarus at DirtFish. Front diff defaults to a viscous LSD and rear to a typical ZF-type Salisbury LSD, which appears to be how it ran most of the time.

Suspension is simple MacPherson strut all around. Aero is nothing special but does help stabilize the car nicely. Gearbox is the 6-speed manual it ran most of the time with ratio set pulled from the old FIA homologation forms. Have let it use the same tire set as the modern RX cars. Probably a good bit better than period rubber (Or maybe not! Group B was pretty wild and using F1 rubber compounds in period wouldn't surprise me) but it's a good drive on them out of the box and good fun to slide.

So...it's a chassis that understeers until you push it hard enough, aero that works mostly to keeping things pointed in the right direction once a slide does start, plenty of power but only above 6000rpm and with some lag, and a great AWD system to put that power on the ground and pull out of corners. Racing this thing is fantastic once you get the hang of keeping it on power and how it likes using pendulum turns for initiating turn-in.


Renault 5 Maxi Turbo: Ceci n'est pas un rallye. The Maxi was Renault hanging on to an aging format in a time with AWD was clearly the way forward in rallying. Mid-engine, RWD, double wishbone suspension, 60% rear weight bias, and 2.5kg/hp may as well be specs from the Renault R.S.01 GT3 car, and this comes through in how it drives. This car was a tarmac specialist in 1985 and it really is one terrific circuit racer. On the whole, it matches up quite well with the Audi quattro, with the per track favorite being all down to how much gravel there is. Daytona is 85% tarmac and gives the Renault a 0.5s advantage per lap; Loheac flips that and the Audi is a 1s favorite; circuits like Hell or DirtFish are more balanced and the match-up is nearly even.

Like the Audi quattro, there is a great deal of information available about it in the form of old homologation papers and people who have restored and maintained the cars since their heyday. The chassis is a very simple design as far as suspension geometry, with the measured kingpin and caster values of 15° and 11.5°, respectively, giving good steering feel especially during opposite lock situations and powering out of corners. Drive comes from the C7K 1,527cc turbo 4-cylinder for 360hp at around 3bar boost absolute, through a 5-speed manual and 40% lock clutch & plate differential on the rear axle. The turbo had a very early anti-lag type of system which recirculated boost airflow to keep it spooled up so long as you don't spend too long off throttle; once boost does drop, it takes a good few seconds for it to come back on.

The restoration folk were a big help in having already measured typical wheel rate of the rear springs and torsion bar front suspension. It runs significantly stiffer than the Audi - again, showing its focus on tarmac events - and with a chassis balance that is far more typical of GT cars than pitching it sideways into gravel hairpins. What's especially telling of differences in the two cars is the chassis moments of inertia that fall out from our models. While both are similar overall dimensions and the Renault is 18% lighter than the Audi (900kg vs 1090kg), the moments of inertia are upwards of 60% lower for the Renault! That's the value of having most of the mass concentrated within the wheelbase; the car is much more eager to turn and respond to steering inputs. Nimble chassis via basic design rather than through modifying a car to make up for deficiencies.

So it's a much nicer handling car, but where the challenge arises is putting power down on the gravel. Power per kg is similar with the Audi, but going to only two tires means you have to be doubly careful about its application. This car doesn't like being tossed around and backed into corners for you to then plant the throttle and power out; that's far more likely to just end in a spin or the engine bogging down. How it gets speed is by using the brakes to rotate the car into a tight, late apex, use just enough power to keep the rotation from stalling, and then feed it back in through the exit with opposite lock to control direction if necessary. It's a lot more difficult than the Audi where anything goes to help fight the natural understeer of its chassis-drivetrain design; that car is all about being rough to make it do what you want while this one is about being smooth to take what it will give you. That's the trade-off of being a tarmac specialist. Loose stuff is pretty tricky, but you can more than make it up by treating it like a flyweight GT on any pavement sections; brake super late, smooth fast apex, power down hard through the exit. Sweet little car.


Ford RS200: Like the other Group B cars, this one proved great for research as 1.) there is a ton of interest in the car and 2.) people who have restored them share tons of old documents and information. Scanning through the original owner's manual is particularly cool, with a whole section on starting and driving the car written by Jackie Stewart.

This car is a classic example of huge potential which didn't have a chance to develop. Ford had spent a ton of time developing the front-engine, rear wheel drive Escort RS1700T for Group B only to throw it all away before entering a race as they saw AWD was the future. And so work started on the RS200 in mid-1983, well behind the rest of the competition and using a lot of parts which were left over from existing projects.

The engine is a Cosworth BDT 1.8L turbo 4-cylinder developed for the RS1700T and is a fine engine, producing upward of 440hp@7500rpm with a wide powerband that runs from 5500rpm right up to the rev limiter at 8500rpm. The parts-bin special nature of the early RS200 cars meant it was fairly heavy, though, at 1050kg and this put the engine at the small end of the displacement scale for its weight class. Evolution versions of the BDT-E, had they competed, were enlarged to 2,137cc and people who have since tweaked and tuned them can see upwards of 800hp!

Clever positioning of the 5-speed gearbox meant an even weight distribution of 50:50 (ideal, in theory) and a simple double wishbone suspension controls the chassis well. The AWD system is comprised of three Ferguson viscous limited slip differentials left over from Escort and Sierra projects. No exact rating for these RS200 diffs online or in old books, but we know from the Sierra Group A car that they tended to run in the 100-500Nm range. Standard setup is for 63% power to the rear with the viscous center controlling differential slip between the axles. It's a good configuration for stability, viscous diffs all around, but does generate a fair amount of understeer. Steve Millen once said "It's quickest to drive the car into a turn very hard, pitch it in with oversteer and maintain that attitude through the corner with the throttle." and that definitely works; it's a car that takes well to the Scandinavian flick technique and chassis rotation follows the steering quite directly. Still, it tends to drive a little tight unless you are rough with it; not slow by any means, but less exciting than the other two above.

This 1986 version of the car sorta feels like it lands squarely in between the Audi and Renault. It has the mid-engine and tarmac handling of the Renault combined with the AWD traction (and inherent understeer balance) of the Audi. Further development probably would have made the car significantly lighter or more powerful and solved any handling issues to produce a truly strong competitor. But Group B was cancelled in 1987 and the RS200 project ended after only a 1-year run.


Ford Mustang RTR Spec 5-FD: Star of the show in this pack, I suppose. smile.png Fundamentally, this thing is pretty simple and works almost like a dirt track racer. Take a basic Mustang shell, strip it down to basics, add a Roush-Yates V8 making stupid power levels, drive it through a 4-speed Andrews dog box to a ratcheting locker rear end, and change up the suspension geometry/setup to make the handling dominated by those rear tires.

Neat aspect of the Formula D rules is that the chassis-side suspension pickup points must remain stock but wheel-side is free. Up front that means a custom control arm for the strut to push the wheels out for wider track and a significant increase caster angle. The rear gets more interesting. Standard Mustang rear end uses a funky multi-link suspension which is surely great for road car use, but probably a little finicky to deal with when tuning a race car. So to get around this, they’ve used the stock pick up points mixed and matched with a custom upright and control arms to make a pure double wishbone configuration with the right kind of anti-squat and roll center properties to help with drifting. There are some good pictures on the interwebs showing what they did.

The trick in drifting it really is mostly about finding a setup that suits your style. We’ve included a few baseline options to get you started. The competition setup runs super low tire pressures and softer rear end to lift the inside front tire like you’ll see Vaughn’s car do in FD events. It’s a good way to get huge drift angle at high speed, but takes massive commitment to hold that edge without over-rotating or straightening and spearing off in the other direction. The ‘drift’ setup takes more of a demo day approach with higher pressures and more rear end stiffness to balance with the front. It is easier to get into a drift but generally slower through turns as a result; which is fine, we’re doing this for fun and not to impress the judges during a tandem run. I’d recommend playing with both setups to see which feels better as a starting point for your personal style then mainly tweak tire pressures and anti-roll bars from there. Small changes to handbrake strength can have a good effect in tuning the car, as well, for those of us without full analog handbrake hardware.

Being late in getting these notes written up, I’ve already seen some of your videos drifting the car and it’s great stuff to see. Love the tandem runs and seeing others get on with such a different driving style. Try it in VR if you have a chance!!


Ford Mustang RTR 1966: There's a lot in common between this one and its main competition, the 1969 Trans-Am Camaro: 5L V8, control arm front with Hotchkiss rear axle, ~2800lb total weight, and decent aero for the time.

For the engine, we took the GT350 302ci V8 as a reference point. There were claims of race-prepped engines cranking out 480hp@8000rpm for Trans-Am, but this is a fairly big number considering the homologation street car (not all that different) was generally agreed to produce 350hp and the Camaros it raced against were dyno-tested to show something in the low-400 range...and those won most of the races. Our model uses dyno data from similar cars and balances it in the 415hp range at 7800rpm to fit well with the rest of the class. FIA's historic database came through again with lots of good information, including a wide range of the gearbox options used in 302ci Mustangs from that era and all are present here.

This car benefits from an improved model of the Hotchkis rear suspension design. Many thanks to you guys for isolating the issues our old version of this geometry had on the Camaro. The investigation into why that one would fall apart resulted in a much more accurate model within the chassis solver limitations (no flexible links) with a roll center that moves more correctly with chassis motion. The Ford Escort models have been revised for this new approach as well.

All of these racers from the Trans-Am era went through some intense modification to cut weight and become race ready; coolest of these processes being an acid dip to thin out sheet metal. They commonly got the cars so far below the 2800lb minimum weight that large amounts of ballast could be placed around the car to get an ideal weight distribution, taking the car from maybe 55% front to balanced at 50:50 or even a little extra on the rear if it suited the track. Suspension setup leans heavy on vintage GT350 data and it works out very well here. It drives like an old muscle race car. Good power but nothing compared to modern cars, loose bias-ply tires so the chassis moves around a lot but never really snaps away suddenly, aero that is fairly neutral, very average brakes and good cornering from wide tires in an era where rubber was just starting to get really sticky.

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Mehr Details zum SETA Reifenmodell von pCARS2

 

SETA TYRE MODEL DESCRIBED

Seta tyre Model (STM) is a full dynamic tyre simulation. Actually, it is three coupled simulations, one for the tyre carcass, one for the tyre tread and contact patch, and one for heat transfer simulation. It is also modular, where different carcass and tread simulation techniques can be used interchangeably. For example, off road racing may use a different tread simulation.


CARCASS SIMULATION

The carcass simulation used in Project Cars is a finite element simulation with specific computational optimizations specific to real time tyre simulation. The carcass is discretized into small connected “elements”, each one flexing and deforming due to forces.

Features:
 

  • Elastic behavior changes with speed, temperature, and pressure
  • Rolling resistance changes with speed, temperature and pressure
  • Sidewall buckling at low pressure
  • Bias Ply, Radial, or Hybrid construction
  • Gyroscopic Effects
  • Dynamic response such as vibration, telescoping, and twisting




TREAD SIMULATION

The tread simulation used in Project Cars is a finite difference simulation of the contact patch, with the tyre tread “flowing” through the contact patch. The whole tread itself is discretized into elements much like the carcass, but the contact patch itself is a finite difference grid.

Features:
 

  • Flash Heating, which is the change of temperature in the outermost rubber layer through the contact patch.
  • Componentized grip model. Each component is affected differently by road surface conditions, wetness, and temperature.
  • Deformation – the rubber deforming in and around asperities, resisting sliding motion.
  • Adhesion – the rubber bonding to surface rubber and material.
  • Tack – the sticky tacky grip you can feel on your shoes when walking a rubbered in track, related to adhesion.
  • Tearing – the ripping of rubber from the tyre
  • Cut – grip from the geometry, edges, grooves, and siping of the tread, with particular effect in dirt and gravel
  • Tread channel depth and water handling.
  • Discretized and temperature sensitive wear
  • Curing
  • Temperature sensitive elastic properties



The carcass and tread simulations are coupled such that there is no roughness or “stepping”, while still preserving the detail of both simulations. The contact patch size, shape, and pressure distribution is determined by the carcass simulation and is used by the tread simulation. The forces on the tyre from the road surface are simulated in the tread simulation and transferred as external forces to the carcass simulation.



HEAT TRANSFER SIMULATION

The heat transfer simulation handles heat flow between brakes, wheel well, rim, carcass, and tread layers. The heat transfer amongst tread elements, from tread elements to the road surface, and from the tread elements to the air are handled directly by the tread simulation (including advection and evaporation). The pressure of the tyre is maintained by the carcass simulation via the ideal gas law.



Emergent Effects

Most effects just “fall out” of STM without explicit coding for effect:
 

  • Fy, Fx, and Mz vs slip angle curves, complete with realistic nuances, such as Mz inversion
  • Inclination effects such as camber thrust
  • Complex and sometimes subtle changes in behavior due to load, heat, pressure, and speed.
  • Proper behavior at a standstill and very slow speeds, although due to limitations of consumer force feedback devices, oscillations may still occur. Many tyre models break down at a standstill.
  • Flatspots
  • Hydroplaning
  • Changes in behavior due to surface differences, such as surface roughness, track rubbering in, wetness, and dirt.

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