General IndyCar Open Setup Basics - 2
Basic primer on in-car adjustments
Hello again! This is the second installment of IndyCar open setups primer. It will involve the in-car adjustments or “tools” you can use during a race. They are the weight jacker, anti-roll bars and fuel mapping.
Here is today’s fun fact about an IndyCar. Over the past 25 years, the horsepower has decreased from 1000 hp to today’s 650 hp for super speedways. Yet, the cars are still going 230 mph or above down the straight at Indy and they may set a new track record in 2015 or 2016. Impressive how far aerodynamics has come over the past few decades. Just wow!! Pushing the laws of physics to even higher levels..
To continue with my discussion from last time, I hope you all will tinker a bit with the car’s wings, wickers and ride heights. Try a test session by yourself. Set the car up from the default fixed setup (say, at IMS). Go out and run 5 or so laps. Pit and lower the ride heights (via the pushrod lengths) by 10 clicks. Go back out and try another 5 laps. If you are slower this time, then go back and add 10 clicks to each pushrod length. If you are faster, then take another 10 clicks out of each pushrod length. Keep doing this to see what you can find out about how ride height affects your overall speed. At some point, you will find the sweet spot for ride heights: being too close to the track surface will cause the car to bottom out in places, scrubbing off speed. On the other hand, being too far above the track surface will not create enough undertray downforce and you will go slower.
After you have found an optimum ride height, it’s time to reduce front and rear downforce with the wing angles and wickers. Try lowering the wicker heights (and lengths). Remember there are 3 wickers on the car: wing wickers, diffuser exit wicker and rear beam wicker. Run a few laps and see what you learn. Then, reduce wing angles in the front and rear, being careful to keep the car balanced. Balance is crucial. If you change the aero forces on the rear of the car more than the front of the car, the overall balance of the car will shift. You want the balance to be neutral (possibly with a bit of oversteer).
There is a chance that lowering the ride heights will not produce enough downforce to keep the car from losing grip and sliding in the corners. In this case, the normal “upper” wings and wickers can be used to increase the overall downforce even more
The trick is to get the car neutral in balance (so the front and rear of the car have the same forces on them) without the front biting more than the rear and vice versa. Plus, you want to reduce downforce and drag until the lap times are maximized but the car feels pretty stable. Obviously, the car can be “trimmed out” more for qualifying than for the race.
Now, comes the fun part – controlling the balance of the car with onboard “tools”. You will always hear a race strategist tell his/her driver “USE YOUR TOOLS!!!”. The weight jacker is a piece of cake to understand and use – the anti-roll bars (ARB), not so much. Here we go:
5. weight jacker – covered before in Primer 1, it is a hydraulic spring located in the right rear wheel suspension that raises and lowers its ride height. The end result is if the spring is extended, the front left wheel will grip more and understeer (“push”) will be reduced. If the spring is contracted, the left front wheel will grip less and oversteer (“loose”) will be reduced. Recall that the weight jacker is only used on ovals.
In effect, each time the weight jacker is invoked (by pushing electronic buttons on the steering wheel), more or less "weight" is re-distributed between the right rear and left front of the car. Understand that no actual weight is being moved in the car. The term "weight" is a bit of a misnomer. However, if scales were put under each wheel, you would see changes in the weight each wheel "feels". This "cross weight" surplus or deficit can make up for a car that becomes unbalanced during a fuel/tire run.
Each push of the weight jacker buttons will add or subtract about 13 pounds of "weight" to the right rear/left front of the car. So, one push of positive weight jacker will add 13 pounds to the left front of the car and subtract 13 pounds from the right rear of the car. This will create more grip in the front of the car and lessen understeer. The exact opposite can be said of one push of negative weight jacker. It will subtract 13 pounds from the left front of the car and add 13 pounds to the right rear of the car. This will create more grip in the rear of the car and lessen oversteer.
You will need 2 buttons on your steering wheel dedicated to the weight jacker – one to increase and one to decrease the spring. They can be programmed in the “OPTIONS” section of iRacing , under “CONTROLS”.
NOTE: THE RIGHTMOST NUMBER ON THE OVAL STEERING WHEEL DISPLAY INDICATES THE WEIGHT JACKER’S POSITION. Push your 2 buttons and you will see the number change from 0 to +20 in the positive directions and 0 to -20 in the negative direction. I have found that between 5 and 10 clicks is where you can really feel the changes. Look out for + or – 15 to 20. It is a HUGE change and you won’t believe how much it will affect the handling of the car.
Also, make sure you neutralize the settings to 0 at the next pit stop. Adding +5 to +10 will really help your car with aero push, but be careful not to keep that setting in clean air. You WILL hit the fence, I assure you!!!
Rule of thumb: add 5 clicks at a time to reduce understeer (“push”) and subtract 5 clicks at a time to reduce oversteer (“loose”).
6. Anti-roll bars (ARB) – now the fun begins! There is a front ARB and a rear ARB and they do just what they sound like they do. They either stiffen or soften the tendency of the car to roll in turns. The confusion is that they work opposite each other. To affect an overall change in the handling of the car, you must stiffen the front and soften the rear (or vice versa).
If you look at the cockpit of an IndyCar, there are 2 pull/push levers located near the driver’s left knee. The front ARB lever is marked “soft….hard” and the rear ARB lever is marked “hard…soft”. So, the driver doesn’t have to do the math. Pulling both levers down will harden the rear ARB and soften the front ARB automatically (and vice versa for pushing them up). Check out the INDYCAR.COM website, go to FAN INFO, then ANATOMY OF AN INDYCAR, then COCKPIT, then ANTI-ROLL-BARS. Watch the video!! You will see the signage on the side of the interior of the cockpit above the ARB levers and sure enough – they are opposites of each other!! One says “HARD” the other says “SOFT” (and vice versa). You can also see the levers move in the iRacing DW12 cockpit (you may need to remove the driver’s arms to see them). Sure enough, they move opposite to each other.!! Try it and see for yourself.
Below is an image of the anti-roll bars adjustment handles to the left of the steering wheel (by the driver's left knee). Note they are labeled "R" and "F" and both are pushed as far forward as possible. Since they work opposite each other, these handle positions indicate that the rear ARB is at the full "soft" position and the front ARB is at the full "hard" position (which would help to cure oversteer, as explained in a few paragraphs!):
Our problem is that we have no levers to pull/push. You will need to dedicate 4 buttons (I found 4 together on my shifter I wasn’t using). They can be programmed in the "OPTIONS" section of iRacing, under "CONTROLS".
Try to find 4 button in a row (they are horizontal on my shifter). Dedicate the left 2 to front dec/rear inc and the right 2 to front inc/rear dec. That way, if you push the left 2 buttons together, you will be decreasing (“soft”) the front ARB and increasing (“hard”) the rear ARBs in tandem. Conversely, if you push the right 2 buttons together, you will be increasing (“hard”) the front ARB and decreasing (“soft”) the rear ARB. You will normally use the buttons in tandem – left 2 together or right 2 together.
NOTE: THE MIDDLE 2 DIGITS ON THE OVAL STEERING WHEEL DISPLAY INDICATE THE FRONT/REAR ARB SETTINGS. EACH DIGIT HAS A VALUE FROM 1 TO 6. You will see them displayed together, so a “53” might appear as the 2 digits. That means the front ARB is set at 5 (out of 6) and the rear ARB is set at 3 (out of 6). Normally, you will want them to be opposite of each other, so: 16, 25, 34, 43 52, 61. Make sense?
What do they do?? Well, stiffening an ARB keeps the front or rear from rolling in a turn. The net result is that the tires tend to slide rather than grip. Conversely, softening an ARB allows the front or rear to “roll with the punches” so to speak and the tires tend to grip more. So, hardening up the rear and softening up the front ARBs will cause the car to rotate more, reducing understeer (“push”). Conversely, softening up the rear and hardening up the front ARBs will cause the car to rotate less, reducing oversteer (“loose”).
All of this is fine and dandy, but keep in mind that the anti-roll bars are on the car to keep it from rolling in the corners. Road/street courses benefit from them the most - because they have several left/right turn complexes that cause the car to roll or tip to the outside of a corner. Ovals don't have that situation in their corners, so you will find that ARBs work much better on road/street courses than ovals. You might find them of some use on shorter ovals, where the car tends to "lean" a little more than on a superspeedway.
Rule of thumb: use the left 2 buttons you programmed to reduce understeer (“push”) and the right 2 buttons you programmed to reduce oversteer (“loose”). This is, of course, assuming you programmed the buttons as mentioned above. LEFT 2 BUTTONS: FRONT DEC/REAR INC. RIGHT 2 BUTTONS: FRONT INC/REAR DEC.
(Anti-roll bars will be discussed in much more detail in the documents on suspension units, mechanical grip and mechanical balance).
7. fuel mapping - you can choose different fuel mapping positions during practice or a race. Found in the "drivetrain" option in the GARAGE, map "1" is full rich/maximum power, 2 through 5 are for green flag fuel saving, 6 and 7 are alternate throttle/power shapings (at full power), and map "8" is for maximum fuel saving under yellow flag conditions.
You will need 2 buttons on your steering wheel (or keyboard) dedicated to fuel mapping positions. Each button will be used to select a fuel map position (either up or down). They can be programmed in the "OPTIONS" section of iRacing, under "CONTROLS".
NOTE: THE MIDDLE DIGIT ON THE OVAL AND ROAD COURSE STEERING WHEELS DISPLAY INDICATES THE FUEL MAPPING SETTING.
The following fuel mapping information may help you decide which one to use:
fuel position 1 - max. rpm = 11,930 max. fuel rate = 43 grams/second
fuel position 2 - max. rpm = 11,789 max. fuel rate = 42 grams/second
fuel position 3 - max. rpm = 11,540 max. fuel rate = 41 grams/second
fuel position 4 - max. rpm = 11,305 max. fuel rate = 40 grams/second
fuel position 5 - max. rpm = 10,636 max. fuel rate = 40 grams/second
(above fuel positions 1-5 use a linear mapping algorithm: 10 % throttle = 10% power, 50% throttle = 50% power, 70% throttle = 70% power, 90% throttle = 90% power, etc.)
fuel position 6 - max. rpm = 11,929 max. fuel rate = 43 grams/second
fuel position 7 - max. rpm = 11,925 max. fuel rate = 43 grams/second
(above alternate fuel positions 6-7 use a progressive (non-linear) mapping algorithm: 10% throttle = 5% power, 50% throttle = 35% power, 70% throttle = 60% power, 90% throttle = 90% power, etc. This allows for less power output from the lower throttle inputs; more power output from the higher throttle inputs)
fuel position 8 - max. rpm = 10,914 max. fuel rate = 22 grams/second
From the above graph, it can be seen that fuel positions 1 - 5 use a linear throttle/power relationship - and a reduction in maximum power from positions 2 to 5. However, fuel positions 6 - 7 use a non-linear throttle/power relationship - and no reduction in maximum power.
This non-linear throttle/power curve for fuel positions 6 and 7 can be used to help control wheel spin out of a slow-speed corner onto a straightaway. Since wheel spin is a function of engine power (RPMs and torque), less power output with the lower throttle amounts can keep engine power below wheel spin thresholds. Also, notice that maximum throttle creates maximum power output - so, you are not losing any power, just redistributing it (less power with lower throttle input, more power output with higher throttle input).
I have no idea if any of this makes sense to you. Please please please ask me (or others) if you are having trouble with this stuff. It is way cool to be able to control your car’s handling during a race. The weight jacker and the ARBs are the tools you have, so play with them and see for yourself.
One last thing: try these tools out in a private test session. Run IMS with the default fixed setup provided by iRacing. Go out on track and add weight jacker. You will see the difference – and probably lose control of the car if you add or subtract too much. Do the same with your ARBs. They are less dramatic of a change (a bit more subtle) but the real IndyCar drivers swear by them. Zach Veach is a dear friend of mine and he uses these tools all the time during a race. Food for thought.
See you guys soon! I’ll be the one using my weight jacker and ARBs!!
Best,
Pete Ramberg