The "Latest" Rig

The "Latest" Rig
Bodnar Wheel w HPP Pedals (Added Rift in Summer 2017)

Tuesday, December 26, 2017

Aero and Gearing Setup for the iRacing FR2.0 Part 2

Aero for the iRacing FR2.0 Part 2
Wings, Rake and Drive Train--Practical

Intro:

OK, now with some basic background information gained from testing, let’s get practical and work on just how to choose the ideal aero settings. First, we have to choose a reasonable starting point, and then we need to understand the cause and effect of adjustments.

To start, let’s hear what two really fast guys had to say recently in the iRacing Forum:

“The vast majority of tracks in this car will be 'full downforce', meaning 31 front and 12/13 rear. This car is very low drag even with the wing on it so unless a track has very very long straights you can usually turn the wing right up and gain speed.

Ultimately you just have to test and see what is faster, but glancing at the schedule, Laguna Seca will be full downforce, so will Donington.  Silverstone, Canadian Tire and Road America may slightly reduced.”

---Thomas Jordan (iRating=6311)

and

 “I did some testing in Watkins Glen today and managed a 41.9. Replay is attached and hope it helps someone to analyse. I was driving a high downforce-setup with 31/15 wings.”

----Fredy Eugster (iRating=8011)

Take a look at the following diagram. We will use it to generally compare the advantages and disadvantages of high and low downforce. The car approaches point “A” at high speed, under full throttle. The driver “lifts” and begins braking.

In the Braking Zone from “A” to “B”, the car with high downforce will have an advantage. Brakes can be applied later and harder since the tires have more grip. The ideal relative front vs rear wing settings are affected by brake bias, spring and damper settings.



As the car approaches the Corner Entry Zone, brakes are modulated (reduced) and steering input is added. Again, high downforce generally provide an advantage here.  Higher downforce produces the biggest advantage in the Mid Corner Zone, although the relative front vs rear wing setting is also very important, Too much relative rear wing will cause understeer; too little will cause oversteer. In addition, the ideal front vs rear wing settings are affected by other set-up parameters, such as spring, damper, ARB and camber settings as well as rake--and especially the differential settings.

Another important factor in Mid Corner is driver input in the Mid Corner Zone as well as driver input in the prior Braking and Corner Entry zones. (Faster entry and trail braking will produce more rotation.)

As the car approaches the Apex, and the Corner Exit Zone, full throttle is introduced as steering input is reduced. Again, higher downforce generally produces an advantage.

So, from points “A” to “D” and to the Track Out, higher downforce produces an advantage. But, at that point the higher drag that accompanies higher downforce will reduce acceleration, resulting in an average lower speed from points E to F and a lower terminal Top Speed.

So, essentiailly we are balancing the benefits in A-D against the penalties from high downforce in E-F. We are also adjusting the relative front vs rear settings to achieve the optimum overall speed through the corner.

Developing a keen sense of whether the car is understeering or oversteering in various sections is critical for making adjustments—of wing settings and rake, as well as many other set-up settings. 

So, always be aware of what the car is doing in sections A-B, B-C, and C-D. A-B is Corner Entry, B-C is Mid Corner and C-D is Corner Exit. There are many definitions of understeer and oversteer. The engineering definition has to do with “slip angle”. Slip angle being the difference between the actual line of tire travel as compared to the line of travel that would occur with the tire rotating without any slip.

Here is my simple definition from a driver’s point of view—Understeer is where the car is rotating and changing direction more slowly than you would like. Oversteer is where the car is rotating and changing direction faster than you would like.  So, by my definition, understeer and oversteer, like beauty “is in the eye of the beholder”.  A veteran pro driver once told me: “When the car is understeering, you see the wall as you hit it going forwards, but when the car is oversteering you hit the wall going backwards.”  

When we get to the final fine tuning, we will use tire temperatures to help bridge the gap between the driver’s point of view and the engineering definition, but at the start, focus on the driver’s perception.

 OK, again. “How do I choose a starting point?” 

There are two schools of thought on this. One is to start with low downforce—optimize the handling with the ideal chassis adjustments and then add downforce for additional cornering speed. I prefer instead to start with high downforce and a “baseline” chassis setup. The driver goes out and pushes the car hard, “driving it like he stole it”.  With the extra downforce, the car will theoretically have reserve grip and recovery from mistakes is easier.

BTW—When I refer to “baseline” chassic setup, I AM NOT referring to the Baseline provided by iRacing.  I will address “How to build three baseline setups” in a later article. For now, use the setup you liked the best for Mazda Laguna Seca for a starting point. If you have no clue—use the iRacing “low downforce” setup, and change to 800# springs all around, reduce fuel to 2 gal, and set Rear ARB to P1 Stiff as a starting point.

High Downforce Setting

We will have a discussion regarding the FR2.0’s special three spring, monoshock front in another article,  One should realize that roll stiffness on this design is achieved very differently than with the conventional four spring suspension found on the Pro Mazda for example. And, the rear ARB will produce much different effects. One can achieve increased roll stiffness by increasing rear spring rates, but again, the resulting effect will be different than on other cars. We will go into this in more detail later. 


So, follow the advice of the experts, Jordan and Eugster.  Start with 31 front and 15 rear. Leave the front wing alone and test reducing the rear wing from 15 down to 12. Choose the rear setting that gives you the most comfort (understeer vs oversteer in the fast corners) and best lap times. Then, test the other setup variables changing from your original baseline settings.  When you feel you have a “balanced” race car, with the right balance of understeer and oversteer that suits you, as well as tire temperature “balance” front to rear on the same side, keep driving to improve your lap times until you consistently get close to your optimal lap time consistently over 3 or 4 laps. Note your top speed at the end of the longest, fastest straight.  (Compare this to other laps you can see on iSpeed, iAnalyze, VRS, or YouTube videos. I always view Thomas Jordan, GTROS (Spanish) and Apex Academy, as well as other drivers’ YouTube videos and always gain some insight/s.)



More or Less “Balanced” regarding Tire Temps (Note camber will make inside warmer)

A reminder: Higher downforce produces the biggest advantage in the Mid Corner Zone, although the relative front vs rear wing setting is also very important, Too much relative rear wing will cause understeer; too little will cause oversteer. In addition, the ideal front vs rear wing settings are affected by other set-up parameters, such as spring, damper and camber settings as well as rake.  So, if the car is understeering or ”pushing” in mid-corner, reduce rear wing a click and try again. If the car is oversteering or “loose” in mid-corner, consider adding rear wing, or reducing front wing a click. (One remedy to a car that rotates too quickly (oversteers) at the beginning of the mid corner is to use “maintenance throttle” but generally there are other more effective ways of dealing with that on the FR2.0.)

Keep in mind the car will not be the same in every corner, so the final “best” is the setting that produces the best overall lap time. Concentrate most on the corners where you using 4th or 5th gear in Mid Corner--downforce is big at 100 mph+. 

Now, test running with lower downforce. Reduce front and rear wings, maintaining the general relative balance between the settings. You will see your top speed increase. You will probably also note significant changes of understeer and oversteer in various corners which may require minor setup adjustments. Continue to reduce downforce as long as your lap times improve.

Note: If you hit the rev limiter in 7th gear only briefly, you may wish to leave it in low 7th , especially for lone qualifying or time trials. In a race, where drafting might be very important, consider going to the high 7th.


Medium High Downforce Setting

One big word of caution. Often, drivers make adjustments to the setup as they are practicing and see lap times improve. They mistakenly assume the setup adjustment was the cause, when in fact, it was simply their driving that improved.  Always go back and reverse the change to see if the perceived advantage from the setup change disappears.

Another word of caution. Often drivers will see their lap times improve when they reduce downforce because they did not utilize all of the tire grip when using the higher downforce settings.  Higher wing settings will provide higher grip and more cornering speed—and to a point—the faster you go through the corner, the faster you CAN GO through the corner. So be sure you are driving the car to the limit all the time during your setup testing. Most inexperienced drivers do not achieve the ideal slip angle for the rear tires, so keep in mind that the car will go faster if you sense a slight oversteering tendency in the Mid-Corner and Corner Exit.

Medium Low Downforce Setting

Ultra Low Downforce Setting

Other than LeMans, the Medium Low Downforce Setting is probably as low as most drivers will ever need, so I assume that the practical range is:

Front Wing:     24---31
Rear Wing:       5---15

Warning. iRacing tinkers with the physics from time to time, so you should assume that some of the “perfect” settings will need to be revised from time to time after updates. (Many can remember that issue in the Pro Mazda.) The process presented here for determining the perfect setting for you should continue to apply.

With experience, you will develop “intuition” and will be able to home in on the correct settings quite quickly.  You can also cheat a bit by discovering what other fast guys are using. But, as I have said—no two humans are the same and often the best setup for you is NOT the same as another guy is using, especially when the other guy has earned an iRating a few thousand points higher than yours.  And, to a degree, wing settings are dependent on other setup settings.

Finally, remember that all humans make mistakes, and in a race, you will encounter many unexpected circumstances. Be sure you have a final setup for your race and time trial that has some “reserve” handling that allows you to maintain control.




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