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ISI Simulations in Action
ISI Simulations in Action




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On Assignment-rFactor Motorworks International
Recently, Motor Chronicle Magazine was given the rare opportunity of a totally unrestricted look behind the scenes of the four main players in the rFactor Motorworks world.� In addition to once in a lifetime exclusive interviews, we were given access to some of the hottest cars around, from the �not so docile� Rhez, to the monstrous FIS�and live to tell the tale.�

Consisting of Vayline Motors, H6, Kodi, and Raceworks Motorsport this dynasty of auto manufacturers decided to pool their resources in late 1990, becoming an official entity in early 1991.� Not only does rFactor Motorworks manufacture some of the most popular automobiles in the world, it is their assistance to the end user in a racing environment that has truly established their reputation as a manufacturer who is more than willing to not only make a profit, but further the interests of their customers in ways other companies can only dream about.� Through the use of their �virtual assembly lines�, anyone can manufacture just about any car they can imagine.� Through the use of VEH, HDV, MAS, SFX, and GEN blueprints, all provided at a small cost to the user, the sky is the limit on just how radical or conventional your car can be.� In fact, Dale �Moonshine� McCoy and Dennis �Shotgun� Hatfield recently settled many of their legendary (see Career section for more information on these two�) off track battles in a one off car co�created by them both at the Mills Grand Prix track.� I recently had the good fortune to be invited to a week long manufacturer�s conference, where rFmotorworks, among other things, let the world in on some of their plans for the future.� It was an amazing opportunity, and I was afforded the luxury of meeting many of the principals in this recently formed collaboration and it was nothing short of astounding.� As an added bonus, Kramden MotoGear Inc. LLC was also there�and they were more than happy to give me a very in depth and detailed look at their DAS 2500 Data Acquisition and Mapping System, an aftermarket add-on that can be used for everyday tasks such as GPS location displays, or as a full blown racing data acquisition and display unit with nearly unlimited programmability.




A Spin Around Mills with Achim

Ladies and Gentlemen, today we'll try to examine Mills from both the driver's and the engineer's point of view.

First you need to get to know the track. If you have not done so yet, take the Howston and drive 15 to 20 laps. We'll use the default setup and then work from there.

On the first five laps, try to follow the racing line loosely. The main goal is to memorize the sequence of corners, to give your brain some landmarks which will trigger the necessary actions later on, when you drive too fast to see every detail.

After 5 laps, speed up a tad and follow the racing line more competitively. Not quite at race speed yet, but fast enough for it to be interesting. Release the throttle considerably earlier than you normally would, and start braking early, so that you won't have to brake hard and will be slow early enough to have time to see exactly what each corner is like and how you have to drive it. These 5 laps are for understanding how each corner works, including the entry and exit phase.

By lap 10 you should have determined approximate braking points; you should also know in which gear to take every corner, and you should know what follows the corners.

Now, it's time to go fast. For another 5 laps, try to go as fast as you _safely_ can. The emphasis is on 'safe'. Still brake earlier than you think you should - it'll be too late quite often anyway. Try to be on the racing line, and memorize what the car does in every corner. Does it oversteer or understeer, and if so where, and what were you doing at the time with the throttle, steering wheel and brake. Are there bumps before/in/after the corner which upset the car? Any spot that seems particularly slippery? Are the curbs usable or not? Is the perspective deceiving you about the actual trajectory of the corner and the appropriate racing line? Is the corner followed by a high speed section (which would mean that exit speed is dramatically more important than entry or mid-corner speed), is the apex where it seems to be or is it earlier/later, and what errors are you making, i.e. what are you trying to do naturally and is this optimal for the corner or not, and if not, in which way (like - are you trying to be on the throttle too early, are you taking the wrong line, braking too late/early etc.)

Is a corner followed by another corner and does using the optimal line or speed through one corner compromise the line or speed for the subsequent corner? Do you reach something just short of the redline on the speedo at the fastest spot on the track when you entered the section decently well and fast? Do the gears match your cornering speeds, or are you at a very high or very low rpm somewhere through a corner but cannot shift to a better gear because that then would again be too high or low in terms of rpm?

Does the rear end get very lose as you shift down for some corners? A remedy to this is to shift down later or to move the brake balance further to the front, but the latter has severe tradeoffs, so if you're still on the default settings, you should only chose the first option. Do the front wheels tend to lock up excessively? Does the car over or understeer during acceleration out of the corner? Can you point it towards the straight quickly after the apex?

Also watch the behaviour of the car itself - where does it follow your steering input well, and where does it not do this. And where does it do things you do not want it to do?

If 5 laps at speed were not enough to answer these questions, drive another 5. After 20 laps, however, you should have enough information to return to the garage and start discussing the driving and setup of the car for this track.

Alright, I assume you've driven those 20 laps now and have the answers to the questions that will come up during the following discussion.

Let me now take you on a lap at Mills how I see it, so that you can reflect upon the differences between my perception and your's, and see the things I watch out for in such situations. I always drive with all driving aids OFF, so this will be the settings for this little guide, but since there are racing series which feature traction control, anti-lock / ABS systems and other electronic driving aids, feel free to enable them as you wish. But be aware that they will change the car's behaviour, so some of the things we say here might no longer apply when driving aids are enabled.

Lets assume we've completed a warm up lap and are now on that short straight stretch preceding the final lefthander leading back onto the main straight.

I try to enter the final lefthander from the right hand curb; since this corner is followed by a long straight, any bit of speed advantage I can take with me out of this corner will remain effective for an in racing terms very long time.

Therefore, I will if necessary sacrifice some speed before entering the corner to make sure I am able to accelerate as soon and as hard as possible out of the corner. I need to have absolute control of the car around the apex to be able to point it into the right direction for the subsequent acceleration as soon and as perfectly as possible.

I start from the right hand curb, I steer early, I use the lower part of the left hand curb when I'm in the Race, I might use the higher part of the curb in Qualifying, but only after I've made sure my setup permits this. Softer suspension settings might allow me to keep the car smooth across the high curb, stiffer settings might not.

Basically, I will point the car to a point somewhere at the end of the right hand curb following the corner, by gradually reducing the steering lock. Smooth driving is an absolute must in rF like in a real car.

Hence, I will not nail the throttle, but will depress the pedal further in three or four steps, while gradually opening the steering lock. The car will probably snake a little, but all that matters is that I can continuously accelerate as hard as your rear wheel's grip allows you. If I can, for now everything is alright. If I cannot, I'll need to change something, either in the setup or in my driving.

Now, I find that the car behaves ok; I'll accelerate flat out until I see the right hand curb preceding T1L (the first corner, it's a left hander).

Again I drive onto that curb. Then as I reach the end of that curb I stay on the throttle and steer left a tad earlier than my eyes would make me believe. There are two reasons for this: for one, at this speed the centrifugal forces will drive the car towards the outside of the corner. So, I need to make some provisions to counter-balance them to still be able to touch the inside curb at the apex of the corner (or wherever I am aiming for), and have the car pointed into the right direction for optimal exit.

It is fairly easy to get through this corner if you follow this advice. However, do not make the mistake to dwell upon your satisfaction about this success. This is one of the major errors a driver can commit - keep his mind focused on the past instead of on what is ahead of him. No matter whether a maneuver went well or not, store it in memory for later reviewing (when you're back in the garage) and concentrate on what is ahead of you.

In T1L, immediately when you have reached the apex - provided you have the speed you should have in the Howston - you have to start braking for T2R. Most of you will have had problems getting through T2R in one piece - this is simply because no matter how happy you are about the speed you carried through T1L, you have to sacrifice that speed immediately to prepare yourself in time for T2R.

Obviously, the car will not want to slow down; it will wiggle and buck. Concentrate on braking and on smoothly bringing the car over to the left hand curb before T2R.

The car indeed doesn't feel too stable, but since the default setup is already a fairly stable one, making the car more stable would make it too slow. We'll have to live with this for now.

I imagine a line through T2R ending on the lefthand curb behind the corner and try to find the right combination of speed and control input to keep the car on that line. T2R is followed by a straight, so exit speed is more important than speed before the apex, and I'll act accordingly by rather trying to prepare for an optimal exit than trying to maintain top speed through the corner.

As I pass the apex and try to be on the throttle early, I notice that the car pushes badly towards the outside curb. I have problems getting it to steer to the right, while at the same time under acceleration it seems very snaky. I make a mental note that I will reduce the differential lock on the power side or the preload to get some oversteer into the car. I may only reduce the preload as the problem mainly exists while the throttle is fully depressed, but of course the preload also affects the coast side, so I'll have to see if I want the car more oversteering on the coast side (off throttle) as well, and if I perhaps only want it a little more lose on the power side with a little less than full throttle applied and would like to regain that extreme stability with the throttle fully depressed - in which case I would reset the preload to, say, 3.

Of course I could change the overall balance of the car, by adjusting the weight balance, or the anti roll bars. Or even by changing the suspension settings, namely the slow action side of the shocks to use weight transfer to achieve a change in the car's balance in specific circumstances. But, the differential lock is a nice way of achieving the same without changing the car's balance, or introducing unwanted side effects. More rear weight will reduce the steering precision, stiffer anti-roll bars will increase tirewear and also reduce the oversteering tendency in static situations. Increasing weight transfer will only have an effect while the weight is being transferred. The diff lock is really the best option for me at the moment.

The camber is already high enough - or even too high. The car feels nicely responsive with more camber, but increasing it does not always increase the overall grip, and it will also increase tyre wear on the inside of the tire.

I could of course decrease the camber at the rear end to get more grip under acceleration, as since under acceleration the rear suspension gets compressed, which increases the camber and might lead to the fact that under acceleration the rear wheels only have contact with the asphalt on the inside, instead of on their entire width. I might end up with more rear end grip under acceleration like this - which might actually be a point to note if I feel that I don't have enough rear end grip under acceleration. But right here the diff remains the best way to go for me.

You can use third or second gear. Second feels faster, but third may actually be faster as the car will not become so untidy under acceleration, and also because shifting down to second under braking might upset the car unnecessarily, and keep me from aligning it for the fastest possible exit.

For now, though, I try to play with throttle and steering wheel to get the car pointed in the right direction. Since the car, depending on the setup, responds differently to control input, I'll just have to try which combination of control inputs gets the desired response from the car, but the theory is to upset the car moderately and perhaps lose a bit of grip at one end of the car (the rear end in this case) to make it easier to point the car into the right direction quickly.

Again, once the car is pointed in the right direction, it is time to return to smoothness immediately. I accelerate flat out towards the right hand curb preceding T3L. This is a very slow lefthander, and you know by now that it is a hairpin type of corner. I start braking smoothly quite a bit before the tiremarks - at least for the Howston these always start too late to server as absolute brakemarkers. You can only use them as relative brakemarkers.

I notice that as I am off the throttle and braking, the car pushes quite hard, it understeers. This can be caused by too much brake balance set to the front wheels. It is now on 69/31, so I'll set this to 60/40 later on. A wheel can only generate so much grip, and this overall available grip is distributed among and shared by all the forces applied to the wheel (or rather, the contact patch, the patch of rubber which is actually touching the road). Hence, if there's more braking done at the front end, the grip remaining available for the steering will be reduced; or be completely annihilated if I lock up the front wheels up entirely.

I must be careful though not to move the brake balance too much to the rear, because that again will make the car hard to control under braking. Directional stability will be lost by having too much brake balance shifted to the rear wheels. I will instead again use the differential lock to make the car more oversteering, but this time I'll use the coast side. I'll reduce the lock on the coast side from 50 to 25 to make the car a bit more oversteering in off-throttle situations.

Again the reduced preload will help, but I'll reduce the coast lock setting as I want a stronger effect and I want that effect at every throttle position and speed situation.

Maybe a short explanation of the preload and lock settings is due.

The higher the preload, the sooner (in terms of throttle position and speed differential between the wheel on the left and the one on the right) the lock will kick in. With no preload and a high lock, you get max lock when the speed differential between the left and right wheel becomes very high. In this case, the lock kicks in late and hard. With a high preload setting, the lock kicks in early and softly, i.e. at low speed differentials between left and right wheel.

Back to the track. I've steered in following the tyre marks, again using the righthand curb before the corner, and the inside curb at the apex. Be aware that the apex in this corner is way late due to the high degree of directional change this corner takes us through. For optimal acceleration out of this corner - and this is yet again a corner followed by a long fast section, hence exit speed is more essential than entry or mid-corner speed - I actually try to hit the inside curb at a point somewhere following the actual apex. The criterion is to as early as possible get the car aligned in such a way that you have a fairly straight line ahead of you for early and determined acceleration into that fast section.

I won't describe where that line is, it is not so difficult to find out, it is clearly apparent.

During exit, I will once again allow the car to drift over to the right hand curb and even use it. If you get on the grass, don't panic. As long as you don't steer hard, the car will let you get away with getting half a wheel on the green. Hence, if you feel that you're touching the vegetation, if you are pointed more or less in the right direction, just stay on the throttle and wait until you're fully back on the tarmac.

The combination of corners we are approaching now is the most fun part of the track. A lefthander across a hill, followed by a kink to the right and another fairly tight lefthander. For reference, we'll refer to them as T4L, T5R and T6L.

Although I hate to lose speed, and want to keep the speed up through these corners, I am aware that through these corners, it is faster to drive the optimal line even if I have to sacrifice some speed for it, than to try to stay at max speed at all cost.

T4L you have to enter from the right, and aim to be on the left where those two well known blue little plastic cabins are. This, for practical purposes, is the apex of this corner, and in this case the apex is not a point, it's a stretch. Do not accelerate at the apex, but wait a tad and only accelerate when you are sure that you will not hit the wall of T6L on the right. From that location after the apex of T4L, you drive a straight line to the leftmost point of that wall. Just before you get there, you turn left and aim to get your left front wheel into the grass to the left of that curb, and way before the apex of that corner.

Cutting across the grass will not be a problem, you're too fast and the contact with the grass is too short to be a problem, and your speed will nicely carry you over to the right and back onto the tarmac.

Do not accelerate too long before T6L as you approach that wall to the right before you turn left, and coast more or less at half or zero throttle through T6L. If you are too fast in T6L, you will get carried over to the right too far upon exit from T6L and cannot accelerate properly for the short straight following T6L.

Let the car drift over to the right as far as necessary, and once you've aligned it with a point allowing you to accelerate without danger of getting carried over to the right and off the track, accelerate.

Again, like in T2R, you can chose between two gears, this time it's fourth or third. Third feels faster, but fourth may actually be faster as the car will not become so untidy under acceleration, and also because shifting down to third under braking might have upset the car unnecessarily, and have kept you from aligning it for the fastest possible exit.

I've driven an example lap which you might want to download and see what gears I use. It'll be made available for download together with the two setups I've prepared for the Howston and the F3.

The next corner, T7R, is tricky in that this track section is shady, and several hours of the day you won't see your braking points as your eyes are not able to adapt quickly enough from the light to the shadow.

The secret is to brake a tad early. It's not a great problem, as this corner allows a nice drift across the inside curb at the apex and hence a fairly high cornering speed. If you've braked a little early but not too hard, you will hardly lose any time as you can keep the mid-corner speed up.

So, brake a little early but not too much, and try to almost hit the grass inside the inside curb with your right front wheel a good measure before the actual apex. Considering the high speed, this should take you through this corner in a nice four wheel drift. Concerning re-acceleration - do not accelerate too far. If you start accelerating and then have to make corrections because you get carried over to the left, that will cost you more time than being smooth and accurate and perhaps a tad late on the throttle. Make sure the car is pointed in the right direction before you accelerate.

For T8L you need to use the right hand curb before entry. Again, try to almost touch the grass at the inside apex of T8L with your left front wheel, but not as much before the actual apex as in the preceding corner - simply because this is a slower corner.

A clean, early and uninterrupted acceleration out of this corner is absolutely essential, because the straight following it is so long. Hence, sacrifice everything necessary for a clean exit.

As you brake for T9L (way before the tiremarks btw), you will notice that your front wheels lock up even before the crest of that little climb preceding that corner. Apparently there's a bump in the road which briefly messes up the wheel's contact with the road.

To brake optimally for T9L, if this happens, you have to briefly release the brake pedal entirely. Don't try to only release it a bit, it won't work as well as simply releasing the brake, allowing the wheels to start rotating again, and then reapplying brake. For those of you who are interested, the theory behind releasing the brake entirely is that without the torque (the momentum of the rotating wheel) there simply is not enough grip at the contact patch to get the wheel turning again. You have to add the wheel's own torque to the equation as quickly as possible to have grip and become able to brake again.

T9L has no secrets - enter from the right, pull over to the apex on the left a tad early again, find a straight line to a point _before_ the apex of T10R, and turn left into T11L from that point. For T12R, again you need to turn early and remain glued to the inside curb for a moment. If you do this you can accelerate early and hard, but do not wait too long before you brake, as once again, you need to align the car optimally for the final corner.

If you feel courageous, you can try to hook the right front wheel into the curb to counter the centrifugal forces, but it is easy to upset the car badly this way - try at your own risk.


Setup considerations

We've already briefly addressed the differential lock issue. In general, the default setup is quite stable and easy to drive. However, it emphasizes directional stability over agility, which of course limits it's ability to achieve lower laptimes.

I would not touch the suspension for now. The default settings allow pretty fast laps and give a basically very usable car.

I'd set the brake balance more to the rear because in the default setup, the front wheels lock up too soon.

I'd set the transmission ratios to match the track's fastest straight. You should stay just under the redline at the fastest location on the track.

I've increased the rev limit to the max - we trust our engines to be good quality and survive this. In extreme endurance races or on very hot days, you might reduce this again - or simply shift earlier.

I've set the weight distribution to 50/50 as I feel it gives me more control over the car. With a front bias, the car will be more stable and precise in terms of directional control, but with a 50/50 weight distribution you leave its characteristic more open, and can decide for yourself whether you want it to be over or understeering. The downside of this is - the car may surprise you as you don't know for sure in advance whether it will over or understeer. You have to introduce that certainty otherwise through the setup if you want this.

I've reduced the brake pressure because the front wheels lock up too much. With reduced brake pressure this is more easily controllable, but too little pressure would of course prevent me from getting maximum braking force.

I've changed the diff as described in the text above.

I've softened the front AR bar one notch to get a tad more grip in corners at the front end. This minor modification did not reduce the directional stability but works towards a less understeering characteristic.

I've reduced the front Camber to -2.5 because at the default setting only the inside of the tires ever touches the ground - clearly visible through the temp distribution across the tires. Good temp deltas from inside to outside are below 10 degrees.

I've also reduced the Camber at the rear. -1.5 may not give me optimal lateral grip in high speed corners, but I get more tire on the asphalt (thus increasing the contact patch) under hard acceleration.

I've changed the tire pressures to get evenly distributed tire temps

And I've changed the Caster from 3.0 to 5.0 for more directional stability. For those who don't know what Caster is - it's nicely visible on motorcycles. Racebikes have a low Caster. Their front fork is a lot more vertical than that of a Custom chopper like in the famous Easy Rider movie. Lower Caster values make the steering more nervous and agile. Higher Caster settings add directional stability at the cost of agility.

But since my setup is oversteering anyway, I don't need that much directional stability. Sometimes setting the front to out values to a higher negative value can also help you steer in - but it didn't seem necessary to use this at Mills.

Good luck out there on the track now, and don't forget the golden rule of racing - to finish first, first you must finish ;-)





 
 
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