Virtual Rally Training

Driving with low grip is a great way to improve your racetrack driving skill. That’s why the Kenny Roberts Ranch is a dirt track. It’s also why the Skip Barber Formula 2000 rides on BFG T/A Radials. If you want to get better at driving, leave the sticky tires at home and drive on all-seasons. The same is true of virtual training. Drive on loose surfaces and with hard tires if you want to improve your feel for vehicle dynamics and develop your car control skills.

DiRT Rally

My favorite rally sim is DiRT Rally. When I first discovered it, during the Steam Early Access release in 2015, I knew nothing about rally. But I soon became such a huge fan that I built my Yaris to do double-duty as a rally car. Truthfully, I haven’t done much rallying in real life. I attended the Primitive Rally School at the Santa Rosa Fairgrounds and goofed around a bit at the Prairie City Off Highway Vehicle Park. Those experiences told me 2 things: that rally driving is the best kind of driving, and that DiRT Rally felt pretty realistic.

So why don’t I do more rally? I only subscribe to a few YouTube channels, but one of them is “Racing Fail!”. I like it so much that I donate to it monthly via Patreon (you can even see my name at the start of the videos). Every week, Racing Fail! shows motorsports crashes from the previous week. And every week there are multiple rally drivers wrapping their cars around trees, driving off cliffs, and rolling through fields like mechanical tumble weeds. Occasionally they catch on fire. That’s sort of terrifying. Racing Fail! is a weekly reminder to stay safe and not to wreck my Yaris (or burn myself crispy).

Back to the sim world. DiRT Rally is old enough that it can be picked up on Steam for as little as $10 when it goes on sale. There are newer rally sims from the same developer, Codemasters, but neither DiRT 4 nor DiRT Rally 2.0 is actually better. One of the downsides of DiRT Rally is that there is no community-created content. While DiRT Rally has some great vehicles (by great I mean lower performance cars similar to what I drive) the collection cars and tracks are fixed. There’s nothing new coming. Community-content is what makes Assetto Corsa great. So that begs the question “how good is Assetto Corsa as a rally trainer?”

Rally Training in Assetto Corsa

While you won’t find much official (Kuno Simulazioni) rally content, the community has created plenty of cars and tracks. While the choice of rally cars ranges from the modern WRC Polo to the historic Lada VFTS, you don’t need a rally car for rally driving. For tracks, there are rally stages on gravel, dirt, and snow, as well as hill climbs, street races, and stadium rallycross. As with all AC community content, the cost is mostly free and the quality highly variable.

For training purposes, it’s a good idea to drive both RWD and FWD layouts because they behave differently. For RWD I go with the NA Miata because Miata Is Always The Answer. I say this even though I no longer own a Miata. The Assetto Corsa NA Miata is such a great model that it’s the first thing I turn to, even on dirt. For FWD, I like the Chevy Monza. The motor is on the weak side and the suspension is on the plush side, just like the cars I drive. The Miata is faster on asphalt but the Monza is faster on dirt. But they are very close on any surface, and make a great set of cars to play with for any occasion.

One of the things that makes rally driving unique is the co-driver. In DiRT Rally, you can have visual or audio cues, and you can specify how early or late you want to hear them. Personally, I use audio only and have them announced as far forward as possible. I really enjoy having a co-driver, but for the purposes of training it’s not necessary or even desirable. So while you can download a co-driver app for AC, and you can drive long rally stages, the best way to use AC for low grip training is on a small, closed course. Below are three tracks I recommend and some target times for a Miata/Monza.

  • Karelia – This is a fantasy rally circuit with a good mix of low and high speed corners as well as compromises. It’s probably my favorite rally trainer. Fast laps: 1:04.
  • Gentlemen Rallycross – Although the graphics are sorely outdated, the track is a great mixture of turns and surfaces. There is a joker section. Fast laps: 1:12 (non-joker).
  • Kouvola Rallycross – This is a stadium rally cross that alternates asphalt and dirt. The graphics on this track are much better than the others. There’s more than one fast line, so experiment. The lap features a joker. Fast laps: 0:50 (non-joker).

Conclusion

While DiRT Rally is the king of rally sims, there are a few things Assetto Corsa does very well. It gives you a HUGE selection of cars and tracks to play with. And if you want to change the grip of any track, simply edit the surfaces.ini file. I’m not going to pretend I’m an expert on force feedback, but the Miata and Monza feel really good. Good enough to program your muscle memory anyway, and that’s the whole point of virtual rally training.

Postscript

Some people say that Richard Burns Rally (RBR) is the king of rally sims. That platform is so old that you can’t even buy it anymore. That said, there are people making content for it, even though the game never supported that. The only way to get RBR is by violating copyright, which I try not to do, so I don’t have personal experience with it.

FWD vs. RWD rain: part 2 (thanks Paul)

I have to thank YSAR reader Paul for sending me down this path, because it’s been really fun. I truly appreciate feedback that makes me look critically at a problem. In this part 2, I do some testing in Assetto Corsa, and come away with some surprise.

Testing scenario

To do the fwd vs. rwd and dry vs. wet experiments, I had to choose a track, two cars, and two grip levels. I like to use Brands Hatch Indy and the NA Miata as a baseline. Sometimes I use the Street 90s tire and sometimes the Street tire. The Street 90s are a couple seconds slower. When you have the AI drive the car, both tires have the same lap times. I think it uses the default (Street 90s) tire. So that’s what I did too.

For the FWD car, I chose the Chevy Monza Classic 500EF. This model is a free download. One reason I chose it is because the dry lap times are very similar to the NA Miata when both cars are on their default tires.

For the wet grip, I reduced traction from the default 0.98 to 0.75. That figure is a little bit arbitrary, but I’ve seen various tables that show a reduction of about that much.

  • Track: Brands Hatch Indy
  • RWD: NA Miata
  • FWD: Chevy Monza
  • Dry – 0.98 grip
  • Wet – 0.75 grip

How to modify Assetto Corsa grip

There are three ways to modify the grip of cars in AC that I know of: run a server, change tires, change track surface. The easiest is the last, but for completeness, I’ll describe the other two first.

If you set up your own server, you can set the grip level of the track. This requires a separate program running as the server. That’s why I’m not recommending it. But on the plus side, it’s just one line of one file.

If the cars are developed in the legacy way, they have editable text files for individual components like tyres (yes, that’s spelled with a ‘y’ because AC uses the British English spelling rather than American English). Most cars these days have binary files that aren’t easily edited. Both the Miata and Monza use binary files. This is why I’m not recommending this way.

If you look in a track folder, you will find a surfaces.ini text file that you can edit. A track may have several surfaces. For example the Brands Hatch Indy file has 11 surfaces. Before you go editing this file, first make a backup copy so that you can restore it to its original configuration later. The grip levels of the various parts of the track range from 0.98 on asphalt to 0.6 for grass. To simulate rain, I set everything to 0.75 because I was lazy and didn’t want to multiply everything by 0.75. But that would be a better way I suppose. However, I planned on driving on the track, not grass or curbs.

AI driver

The first thing I wanted to test was how much the AI driver was affected by reduced traction. Here are the values.

  • RWD -7.31% loss
  • FWD -6.95% loss

There is more loss in RWD than FWD. To put it into the perspective of a typical lap, if your dry time is 2:00 minutes, your RWD wet time will be 2:08.78 and your FWD wet time will be 2:08.34. 0.43 seconds is pretty significant in a sprint race, but we’re not talking about 10 seconds here. It’s just a little time. However, this is the AI driving. What about a human?

Human driver

Move over AI, it’s time for Ian to step into the car.

  • RWD -9.06% loss
  • FWD -6.92% loss

That looks a bit more significant. Let’s put this into perspective of my Toyota Yaris at Thunderhill last May. My fast dry time was 3:43. If we multiply these 223 seconds by 1.0906 and 1.0692 we find that the difference between RWD and FWD is nearly 5 seconds. That’s pretty significant! Given that my Yaris is heavier, higher, and less powerful, than a Miata, the Miata has all the advantages on a dry day, but given some rain, the advantage just might tip in my direction.

Here are the graphs for the simulation experiments.

However, this is a human driving a simulator, what about in real life?

More data diving

Let’s look at the actual laps from the race. On a dry track, I was averaging about 3:50 in traffic. Bring on the rain and that drops to 4:20. So about 30 seconds. I had to make a lot of passes, and when I had a clean lap, I got down to 4:03, which is a loss of just 9%. Driving around slow cars in the rain really kills your lap time.

Some of the fast RWD cars I passed included the Miata of Eyesore and the Celica of Uncle Joe’s. Eyesore’s fast lap was 3:29 but in traffic it was typically 3:35-3:40. They dropped to 4:35-4:40 in the rain, a loss of 60 seconds. Uncle Joe’s fast lap was a 3:34 and it’s traffic laps were in the 3:40-3:45 range. In the wet, they dropped to 4:25-4:30, or about 45 seconds.

Two of the fast FWD cars I passed were the Integra of Big Test Icicles and the Neon of Neon Pope. The Integra went from 3:50 dry to 4:25 wet. The Neon was 3:45 and 4:30.

The race winners, Shake and Break (E30), were typically lapping at the same speed as Eyesore in the dry (3:35) but much faster in the wet (4:10).

Let’s take a look at the relative losses of these cars.

  • Yaris -13%
  • Celica -20%
  • Miata -28%
  • Integra -15%
  • Neon -20%
  • E30 -16%

Summary

Given equal lap times on a dry track, a FWD car definitely has an advantage over a RWD on a wet track. How much? I think it depends a lot on the skill of the drivers. At the high end, maybe 0.5 sec per lap. At my level, a couple seconds. At the “you can’t drive for shit in the rain” level, I think it’s less about which wheels are connected to the engine and more about the driver lacking the skill and confidence to maximize traction in the rain. Pedal mashers who over-brake and then hammer the throttle are the ones most severely affected. A Miata doesn’t normally spin when you stomp on the throttle. But it does in the rain, and if one’s driving style isn’t very nuanced, rain will be very unkind to your lap times. However, in a FWD car, stomping on the throttle may cause a bit of understeer, which is easily mitigated by lifting. FWD cars are more noob friendly. I’m not a noob, so I don’t see that FWD and RWD are that much different. But to someone not used to sliding their car around, RWD could be a major disadvantage.

I just watched the “you suck at racing in the rain” video again asking myself “where does the Yaris have an advantage?” The expectation is under acceleration. But that’s not where I’m catching people. It’s under braking. There is no FWD braking advantage. If you’re thinking it’s because my car is newer than the others and has ABS, that’s a good idea. However, you can hear the tires sliding in some corners when they lock up because my ABS has been broken for a while.

So to sum it all up, the reason for Yaris Rain Domination (YRD) is a little bit of FWD advantage and a shit-load of “most people suck at racing in the rain”.

FWD Drifting: Part 2 and Cones in Practice

Last week I talked about some of the tuning and techniques for drifting FWD cars. Some readers may be asking “why bother?” Well, because it’s a driving skill. And if you can drift a FWD car, it will help you drift a RWD car. Inducing oversteer by dynamically changing the balance of the car is important regardless of which wheels are providing power. I shot the video below on the skid pad at Thunderhill between coaching sessions.

The first part shows an exterior view of some switchbacks. It’s sort of comical how slow I’m going and how little my car looks like a racecar. But even at slow speeds it will slide around corners. In the second part, the camera is inside the car. You can see that I don’t use the hand brake. The car oversteers by changing the balance of the car, not locking the rear wheels. It’s also set up with a lot less grip in the ear. The car has RE-71R tires on front at 26 PSI (cold) and Hankook runflats on the rear at 38 PSI (cold).

The next series of shots are what I’m calling point to point. It’s just going around two cones but with different turn radii. I start with a large radius and progressively shorten it. Which one do you think takes the least time? Back in December, I posted on this topic. See Cones in Theory. If you don’t want to read that whole post, here’s the short version: I make the statement that path A takes less time than B, C, or D. That’s the experiment I’m performing in the point to point videos above.

I timed the various runs and indeed, the tiny radius is the fastest (path A). It’s also in a very bad spot in the power band. I’m driving in 2nd gear the whole time, and there just isn’t as much power when driving the tighter radii. But it didn’t change the outcome. Path A is the fastest way around a brace of cones.

FWD Drifting: Part 1

There are a lot of people out there who think FWD is not fast and not fun. Well, as an owner of both FWD and RWD track cars, I can say that I have just as much fun in a FWD Yaris as a RWD Miata. One of the big reasons to hate on FWD is that you can’t drift it. Drifting is cool. Delicately balancing a car as it swings around a corner looks and feels awesome. It’s not always the fastest way around a track, but it definitely looks the coolest. I’m not a drifter and I don’t really understand drifting competitions, but I sure do understand the fun. In the next couple posts I’m going to share my thoughts on how to drift FWD in theory and practice.

First off, drifting is simply oversteer. That term simply means that the front wheels have more grip than the rears. A better way to think about it is that the rear tires have little grip. There are several ways to create oversteer. Before getting to that, let’s talk about tuning. Most cars come from the factory with understeer built into the design. After all, it’s safer if cars don’t spin. To get your car to oversteer, you may need to do one or more of the following.

  • Turn off traction and stability control if you have it. This nanny can totally kill all efforts to drift.
  • Use very lopsided tire pressures. Fronts should be a little lower than usual and rears should be near maximum.
  • Use different tires front and rear. Fronts can be a typical 200 treadwear sport tire while the rears should be hard and skinny all seasons.
  • Tighten up the rear suspension with higher rate springs or/and anti-roll bar.
  • Increase the toe in the rear. Normally, cars are aligned to be toe-in (negative) in the rear for safety, but toe-out (positive) helps oversteer.

So now that you car can oversteer, how are you going to go about it? In powerful RWD cars you can mash the throttle and the tires will spin too fast to make good grip with the pavement. Hey, anyone can stomp on a pedal, that’s cheating. How else can you create oversteer?

  • Lift – The simplest way to lose rear grip is to quickly lift off the throttle. This deceleration will shift the weight of the car forward on to the front tires. Since FWD cars naturally have more weight on the front, simply lifting off the throttle can induce oversteer. Try going around a circle at the limit of traction and then lift. You will oversteer.
  • Brake – You can very quickly transfer weight forward by braking. Really, there isn’t much difference between lifting and braking in theory. In practice, they can feel very different because the brakes act on all 4 wheels while lifting works only on the drive wheels.
  • Scandinavian Flick – If you want big drifts, lifting and braking may not be aggressive enough. Not only do you want to transfer weight forward, but also sideways. To do this, you steer in the opposite direction to load the weight on what will become the inside of the turn. Then turn as normal and the shift of the weight from inside to outside will help break traction.
  • Decrease radius – The speed you go through a turn is determined by the turn radius. Larger radii have higher speeds. So if you turn the wheel tighter it has the effect of slowing you down. This transfers weight forward, which helps oversteer. But if you’re scubbing the front tires because you turned the wheel too much at the start, turning it more won’t do anything.
  • Hand brake – Grabbing the hand brake shifts the weight forward and only applies rear brakes. It’s almost like it was made for drifting. That said, I generally don’t do it. It seems like cheating to me. Also, you could flat spot tires by locking them up. You can get all the oversteer you want without the hand brake.
  • Clutch pop – Another technique I don’t do. Seems like it puts unnecessary wear on the car. On the other hand, try coasting around a corner and then pop the clutch. It can spin you (more so in RWD). If nothing else, this is a reminder not to pop the clutch.

Once the back end of the car is coming around and you’re pointed farther into the corner than necessary (that’s oversteer), what next? First, you have to do some counter-steering to prevent the car from spinning. Frankly, this takes a lot of practice to know exactly how much. Second, don’t hit the throttle. This will transfer weight to the rear wheels and kill the drift. This is where FWD and RWD are really different. You set up the oversteer the same way: by moving weight to the front and side. However, throttle improves RWD oversteer and kills it in FWD. So you have to be patient and wait until the oversteer is mostly over before adding throttle.

Here’s my thought process as I grab some FWD drift.

  1. Drive in an arc to keep the suspension loaded on one side
  2. Turn the opposite direction in a decreasing radius
  3. Snap off the throttle
  4. Drift initiated
  5. Countersteer
  6. Wait for it
  7. Keep waiting
  8. Patience
  9. Throttle it out and recover

Tune in next week for a demonstration…

Oversteer overanalyzed: weight transfer & brake bias

Whether you’re talking about drifting, e-brake turns, trailing-throttle oversteer, or Scandinavian Flick, oversteer looks awesome. It’s not always the fastest way around a corner, but it’s the coolest. Unfortunately, oversteer often leads to spins and crashes. Understanding oversteer will make you safer and faster, so that’s the topic for a few posts.

First off, let’s define oversteer. It’s pretty simple really. It’s caused when your tires are sliding and your front tires have more traction than your rear tires. Assuming your car has 50/50 weight distribution (half the weight on the front tires and half the weight on the rear tires), when you start to slide, the front and rear tires will slide equally. But this assumes you’re not accelerating or braking. As soon as you accelerate, weight and traction shift to the rear. This causes understeer. As soon as you brake, weight and traction shift to the front, which causes oversteer.

Wait-a-goddamn-minute, if accelerating causes understeer and braking causes oversteer, how the hell does drifting work? That’s totally different and has nothing to do with weight transfer. If you spin your tires really fast, the friction starts to disappear. The rubber begins to liquify and gasses build up at the tire-road interface. That’s some slippery shit. But even drifters initiate their turns with weight transfer. It’s the key to understanding oversteer.

So how does one add weight to the front of the car while driving?

  • Brake
  • Hand brake
  • Downshift (RWD only)
  • Trailing throttle oversteer
  • Downhill

Brake

Probably the most obvious way to shift weight forward is by pressing the brake pedal. But what isn’t so obvious is how much of the braking effort is being done by the front wheels vs. the rear wheels. Generally, the front brakes are designed to do more work than the rears because the engine is in the front of the car and the weight is also transferring to the front. Adjusting the brake balance between the front and the rear can make the front or rear tires lock up first. If the brake balance is too far to the rear, the rear tires will lock up first, which will cause additional oversteer beyond the weight transfer. How can you change brake balance/bias? That’s a topic for later.

Hand brake

The hand brake does double-duty for oversteer. (1) It transfers weight to the front (2) It causes the rear wheels to lock up. Grabbing a fist-full of e-brake is one of the most common ways to make a FWD car oversteer. There are a couple reasons for this. First, FWD cars can’t liquify their rear tires, so that’s out. Second, FWD cars have most of their weight forward anyway, so locking up the rears gets them to pivot very easily.

Downshift (RWD only)

Engine-braking a RWD car slows down the rear wheels only. This effectively changes the brake balance toward the rear. Downshifting and feeding out the clutch is therefore a good way to cause oversteer because the weight is transferring forward and the rear brakes are doing more work. A sudden pop of the clutch is a lot like grabbing the hand brake.

Trailing throttle oversteer

Driving at constant speed requires some throttle to counteract air resistance and mechanical friction. As soon as you lift off the throttle, the weight shifts forward. This is called trailing throttle oversteer (TTO). It’s basically a milder form of downshifting.

Downhill

If you’re driving on a downward slope, there is naturally more weight on the front than the rear. The car wants to oversteer simply because of the geometry of the track. Downhill corners are therefore the most prone to oversteering (and spinning).

Quiz

See if you can determine why these crashes happened.

Bad driving tip #8: downshitting

Downshifting is the process of selecting a lower gear, generally on the approach to a corner. Downshitting is spinning a RWD car while shifting because the rear wheels locked up. There can be multiple sources of downshitting. The simplest is to miss a gear change and put the car into 1st instead of 3rd.

More commonly downshitting is caused by people who habitually engine-brake (i.e. use the friction of the engine to slow the car down). In racing, this is wrongity-wrongity-wrong. Your brake balance should be set up with pad compounds and prop valves to provide the ideal braking balance WITHOUT the engine. As soon as you put the engine into the equation, you are changing brake balance. In a FWD car it’s not a big deal. It just puts more braking power on the front of the car, which paradoxically increases your stopping distance because your rears are doing less work. But in a RWD car it is a big deal because once your rear brakes overpower your front brakes, you will spin, even going in a straight line. Do that in a corner, and you’ll snap around so fast you’ll think you were hit.

Intentional or not, the source of downshitting is releasing the clutch pedal when the vehicle is going one speed and the driveline is going another. The driver below gets his foot caught under the throttle and can’t get the revs to match. I’ll bet if he had a do-over, he would have kept the clutch in and coasted around the corner.

 

GRX: alpha test 1

Today, I took the GRX (Generic Racecar Experiment, 2007 Toyota Yaris) for a test-n-tune day at Thunderhill West with Ace Robey’s Exclusive Track Days (which despite the name is rather inclusive). I had 2 goals for the day (1) test the RaceCapture telemetry device (2) learn how to drive the Yaris more aggressively.

The RaceCapture is a tiny device that you plug into your OBD2 connector. It draws power from there and then broadcasts telemetry data over a Wifi signal. It reads various car sensors over CAN bus and has high resolution GPS and accelerometers on board. It’s not available to the public just yet. I got my unit early as part of the beta test group. There are some bugs to work through, but it’s clear it’s going to be the most bang for the buck in racecar telemetry.

rc

 

A B-Spec Yaris doesn’t really have much you can tune. There’s tire pressures and that’s about it. So the test-n-tune day was more about testing and tuning the driver than the car. I did a little research on B-Spec lap records, and they tend to lag Spec Miata by +6-8%. That is, if a Spec Miata can do a lap in 100 seconds (1:40) a B-Spec would take 106 to 108 (1:46-1:48). My mostly-stock Miata on 200 treadwear tires tends to run about 5-7% off SM pace. So I need to get my Yaris times close to my Miata times. No rush though since I am aiming for the 2018 SCCA Runoffs. I have about 2 years to get my driving to the National level.

The day started with rain, which was a little unexpected for early October in Northern California. The initial rain after a long dry spell tends to be extra slippery because of the oils rising off the pavement. As advertised it got very slick. Most of the cars decided to park, but some of us stayed out and had a great time.

In the second session, the track was drying, but I was fiddling around with the RaceCapture and missed most of it. I decided to put it away and work on my driving the rest of the day.

Session 3 was just before lunch. The track was now completely dry and the weather was perfect for lapping. I looked at my lap timer mid-session and was surprised to see 1:34.1. I was hoping to break into the 1:35s and there I was knocking on the door of 1:33. In the last lap of the session, I got a great drive out of the last corner but fumbled the upshift. Crap. Another 1:34.1.

I had a light lunch and then when back out with the rest of the open passing group. Everyone was behaving themselves really well, and I was able to find some space for a few flyers. I got a couple more 1:34.1s and then tried a new line through T1. Driving the Yaris is different from the Miata, and I’m learning the nuances. It’s not just FWD vs. RWD. One difference is that the Yaris is geared tall with huge spaces between gears. It’s ANNOYING! But I’m adapting. And I threw down a 1:33.7. When I checked the timer and saw the time, I literally screamed all the way through T1. I don’t have that on video because the damn 12V adapter kept falling out. Thankfully there was a track photographer.

4tr_5489

So how does a 1:33.7 at Thunderhill West compare with my Miata? About 1 second off. Not bad. Not bad at all.