991.2 GT3RS Data Analysis by Racewekz
Part 1: Motion Control Suspension (MCS) 3WWR
With racing suspended for the majority of 2020, we’ve had some time on our hands to work on a data portfolio for the 991.2 GT3RS. This is something we have done, in varying degrees, with different models over the years such as the e46, e9X and f8X M3’s/M4 as well as the 991.1 GT3/RS. This is, however, the first time attempting to do a write up for public use in detail, so bear with me.
With the exception of the 991.1 RS, these cars were fairly lackluster in delivered form. Sadly, this is all too common when you talk about the new “luxury sports car”. These cars give a taste of extra power, slightly stiffer suspension, maybe a special tire compound that’s not all that special and wrap it in some stitched leather and vents to deliver to the masses touting the race pedigree and refinement. Personally, I’ve always felt that after driving a new “M” car as delivered from the factory, it left me more frustrated than excited. They tend to be soft, overweight and missing the visceral feeling we, as drivers, long for. Even the 991.1 GT3 is guilty of this. You can see, and more importantly feel, where it was purposely cut short with inferior dampers, undersized tires and just plain wrong spring rates to extend the gap between it and the flagship RS. Don’t get me wrong, the RS isn’t perfect, but it definitely checks the “Sports Car” box. In testing, with both cars on proper dampers, spring rates and tire with a touch of extra aero for the non RS, the 2 cars are actually much closer than one would think, well within a second close.
Digressing from my wild tangent, I get asked all the time what works, what doesn’t and why. To be clear, there are many qualified, brilliant engineers, mechanics and general set up/data personnel out there, some with differing opinions. I always preach, practice your own due diligence and take ownership over your own conclusions and take the data for what it is and I will do my best to mitigate, or at least address any variables at play. Without further ado, here’s the start of the 991.2 GT3 RS Data Analysis where we’ll focus on suspension, dampers and springs specifically.
The 991.2 GT3 RS, as you will see, is an incredibly capable street legal car as delivered from Porsche. They (Porsche) have really put together a cohesive package with this car, I struggle to think of any car that is a better all-around package in stock trim. The C7 Z06 comes to mind but it’s plagued with problems that keep it from being a worthy contender. Not only is this car easily capable of properly fast lap times right off the dealerships floor, it also accomplishes something that very few cars even close to as fast as it can do. It’s a fun driver’s car. It’s also easily useable on your average commute with its axle lift suspension for steep driveways, decent stereo, Porsche fit and finish and basic creature comforts. I have personally driven one across the US and had no real complaints about it as a means of transportation, even the gas mileage is acceptable.
For these tests, unless otherwise stated, every data lap was generated using the following control points:
-OE sized sticker Dunlop Sport Maxx Race 2’s (SMR2’s) on OE sized Forgeline VX1R’s
-Wing angle Max available AOA on OE wing
-Our alignment settings and heights are constant across all data tests. (Tarett tension links and shims before first data sample)
-Ambient and track temperatures checked and kept +/- 5degrees Fahrenheit
-Same time of day +/-1 hour
-Dundon dive planes
All data was acquired with the AIM Solo DL2 and video provided by AIM SmartyCam. For this test, Motion Control Suspension (MCS) provided the dampers, 3WWR (3 Way With Remote) with Swift springs. All other items constant. It does bear mentioning that MCS did not compensate us for this test, nor did they give us anything for free as an incentive to promote them. I will do my best to keep everything very basic and easy to understand. Feel free to reach out to me if you have an interest in looking at the data files yourselves. I can email any files as long as there is an understanding that these files, as well as this report, are our property and not to be posted publicly without express written permission from us.
The first data set we’ll look at closely and start to break down is from the 2.5 mile track at Willow Springs International Raceway (WSIR) or Big Willow as it’s commonly referred to. This is a local track for us and comes with a very storied racing history as well, including Ken Miles and Carroll Shelby which you’ll notice if you’re a Ford v Ferrari fan. This is a bit of a different track than what most are familiar with these days. It only encompasses 9 turns, all of them with their own tricks and twists. It’s a fast track that is dependent on momentum to achieve any reasonable lap time. The surface is smooth in some places and unnervingly rough in others. This makes it a little unstable, especially through turn 8 which is a high speed right hander with a loose, poorly maintained outside surface and a bumpy middle/inside surface. This is a perfect example of where the stock dampers just weren’t up to the task and caused a fair amount of instability and created a lack of confidence for the driver, ultimately leading to an increase in time to navigate. The first screenshot we’ll look at is of the speed difference in turn 8 between oe dampers and MCS’s. The 3rd way on the MCS grants us bleed off from these bumps and allows the car to stay more composed and the driver more confident leading to a higher maintained speed, which is of course the key to any lap time.
Looking at this graph we can see some very important factors. The most important graph whenever we’re looking at data is Speed (not counting Time variance, which is the +/- time and the combination of all graphs and effort in one line). Almost always, higher speed leads to faster lap times. Exceptions are pretty limited; one would be longer route travelled but I won’t get into possibilities too much. If we look at the speed comparison between the OE suspension package and the MCS’s, we can see a massive 7.1mph peak difference in T8 (Circled in Green) as the aforementioned 3rd way bleeding off bump travel allows the car to stay composed over the rough surface. Averaging a 6mph increase in speed through T8 and the extra stability from the improved platform in t9, the combination of T8/9 net us over 0.700 seconds gained (Circled in Orange) in just 3,000ft, which needless to say is impressive. This is validated not only by the driver’s comments, but the increase in Lateral G (Circled in Blue) which shows a continuous gain across the entire turn and peaking at a +0.21g improvement.
On the subject of Lateral G, one of the things I look for when making adjustments to cars, after speed, is Lateral G. Higher average speed is mostly a byproduct of higher cornering forces, of course power and drag are variable factors as well (ie. higher aero forces may yield higher cornering speed but the increase in drag may reduce straight line speed enough that you see a net negative). This of course opens us up to the question of balancing a car for a given track, but that’s a topic for another day. Looking at the Lateral G graph below, we see that there is a consistent gain in G load basically across the board. This is a good sign that you’ve made the right changes/adjustments so far.
Some of these spikes lead me to believe the set up with the new dampers isn’t quite perfect for this track with these tires, but more test time would determine what else we can get out of it. My bet is that if we had this car hooked up with shock pots we would see the higher G load on the Lat graph, and a higher frequency with lower total compression travel giving us the platform but seeing larger spikes from the bleed off from the bumps in the surface. This is really just a theory from experience though.
Now is when we start getting into what I call soft data. This is anytime where the likelihood for variable change is greater than typically acceptable to the engineer, crew chief or whoever is handling setup of the car to ultimately make a change based on the graph. In this instance, we’re looking at throttle input, which I like to use as an indicator of driver confidence and overall speed. In my eyes, if the driver can spend more time on throttle and this correlates with an increase in time variance from your reference lap, the cars set up is better.
Take this with a grain of salt though for two reasons. The first being I have had many discussions with many very qualified people surrounding this and it’s always a point of debate. One conversation with a friend who is, without question, a better driver than I am comes to mind. He has driven every kind of GT car at the professional level around the world and his comment is this: In certain mid and rear engine race cars, lower throttle scatter plots are common in drivers posting faster lap times, ie. less throttle use is faster. This may sound counterintuitive, but the reason made, and well made at that is that race drivers have been known to be a tad, overzealous. This can create an over worked and ultimately slower car, especially in the long run of a race. “Be responsible with the throttle” has never held more meaning to me. The second. Without having an immediate debrief with a driver after a session, it’s very hard, borderline impossible to determine certain things in data. One graph in particular would be throttle. Being that the reference lap and the MCS lap were on different days, the attitude and mental state of the driver can change, if even slightly, and you can see that come out in data. With that in mind, we can either believe that the set up is better, allowing the driver to be on throttle more and explain the increase in throttle activity. Or concurrently, we can question whether this is a variable and the driver was driving more aggressively that day.
Rarely can you ever look at one graph and come to an answer, so this would be taken into consideration with other graphs when deciding on set up. Personally, I would look up and see the increase in G load, time variance and speed and conclude that there is more stability leading to a faster car and not being over driven. This could be looked at more closely if you had tire temp sensors and shock pots to see what else is changing and have data that confirms if the tires are being over worked or not.
The Time Variance graph above is all that is needed and is the telltale graph to confirm a positive result. Seeing a relatively linear Variance graph like this tells us that we haven’t just improved one characteristic or been lucky/unlucky in a given corner but have improved the car as a whole. Taking all of this into consideration, I am more than just pleased with this change. I’m sure there’s some more time available in set up, but the proof of concept is there in droves. Seeing this kind of time gain, on a track this fast, with a car already this capable is incredibly impressive to me. We usually see these kinds of numbers from dampers and springs alone on what we already covered as todays “Sport Luxury” cars that are in serious need of help, not true sport cars like this 3RS. What makes these dampers even better is the comfort level on the street isn’t compromised, it’s actually arguably improved. Of course, it’s rare in cars and motorsport to be able to gain something as significant as this on track improvement and not make it a tradeoff for something else.
Next, we’re looking at trading the SMR2’s for the Cup2R’s with these dampers. We have test data showing the Cup 2R’s alone improving lap times 2 seconds over the SMR2’s on OE dampers. Randy Pobst, who of course needs no introduction, was able to click off a 1:23.6x on a stock car with basic track set up and Cup 2R’s. This is consistent with what we have seen with data on the 2R’s. This makes us curious to see what kind of gains can be achieved with tires and dampers alone. Of course, with the considerably higher price tag of the Cup 2R’s and the, relative, affordability of the SMR2’s, mixed with the depression inducing fast wear rate of the Cup 2R’s, the MCS’s are a lap time bargain by comparison. Begs the question, will tires show the same gains with motorsport suspension that they did with the OE pieces, or do the tires cover up or perhaps exacerbate some of the issues of less than optimal suspension. The hunt for the
fastest lap continues…