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Unread 02-12-2018, 07:35 PM
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Default Re: Vorshlag/AST EVO X - Project / Deveopment Thread

continued from above

The short answer was NO, the weight disadvantage of the EVO X cannot be overcome for this SCCA "STU" class.



I recently spent some time looking at the Nationals' STU results from 2009-2017 and EVO X has never placed in the top 10, ever. There's just no getting around the 3600 pound weight of the X chassis compared to the 2950-3100 pound weight of the EVO VIII and EVO IX chassis. Carrying 500 extra pounds on the same skinny 245mm tires just doomed this car from the start - and frankly, I should have known better.



The 2009 STU season was dominated by EVO VIII and EVO IX models - a 2004 EVO took the top spot and a 2003 EVO took 2nd, and the image above shows that 7 of the top 10 cars were VIIIs and IXs.



We struggled all week at Lincoln to dial in the setup on the grippy concrete, a surface which we had not done much testing on all year - much less with the recently added 245 tires. Man I cannot describe how different the car was on 275s compared to this!



Having "blocked out" this event for nearly 9 years I never looked closely at the images from this 2009 Solo Nats. The shot above shows the outside front tire with massive deformation (tire pressure was too low) and the inside rear tire off the ground. The AWD system also doesn't deal well with a lifted tire. The lifted rear, the skinny tires, plus the heavy front loading led to considerable understeer.



My co-driver in the EVO X in STU class that year was once again John Schier. While only a tenth apart over two days we were both 3.2 seconds back over the two courses. That's an eternity - yet running nearly the same times as each other led us to believe we had a serious car determent. Neither of us wanted to compete in this car on 245s ever again.



It didn't seem to matter in STU-Ladies as Amy had a huge 2.5 second lead going into the last runs on Day 2 for her class. She was fighting the setup but we had raised tire pressures to try to deal with the push. Of course it rained before her runs and she was driving in wet but drying conditions - which she always does well. There was a protest in STU-L the day before against a car that was visually illegal in 3 ways, but the protest was thrown out because the driver "came from so far away". I cannot make this stuff up folks.



With a massive lead going into day 2 it wasn't a worry and we expected Amy to once again salvage our poor showing in Open with a win in Ladies. The DSG trans had been acting funny for a month and it was really giving her fits on Day 2. On her last run the wet pavement was really drying, so she pushed it to ensure that none of the other competitors could drop a hero run on her.



On Day 2 the auto-shifted DSG transaxle was possessed - and the damned thing auto-downshifted from 3rd to 1st in the final offset before the finish, which caused Amy to snap spin her last run away. She was super pissed off when she came in, but we thought still comfortably in the lead. Of course the car that was much more prepped, 600 pounds lighter, and visibly illegal had a hero time - dropped massive time on the final drying run, and nipped her time for both days by .069 sec, dropping Amy to 2nd. Just figures, right? We should have pushed the protest on this car through, over the weak sauce objections of the National Solo group.

Still, the EVO X was the wrong car for either class, when penalized with the 245mm tire. We had no business bringing the car to this event, so the results it generated should have come as no shock. We had to be there for various company/sponsor reasons, but it still made for a bitter end to our time with the EVO X.

WHAT DID WE LEARN?

Running this 2009 Solo Nationals, and the previous year of autocross, track and suspension development with this EVO X taught me a great many things. I will try to list out the major points learned or reinforced with this project:



1. Most cars are usually easier to class and compete with equally in NASA Time Trial than in SCCA Autocross
2. You can't beat physics: a 600 pound weight penalty with the rest being equal (tires, power, aero) is insurmountable
3. Prepping and racing in a new car that is A) under warranty, B) has monthly payments, and C) owned by somebody else is a bad idea three times over
4. Never trust the SCCA to follow their own rules (protest)
5. Never build around SCCA autocross classes when they are fundamentally broken (took me a few more years to learn that)
6. I am a better driver in NASA Time Trial than in SCCA Autocross (has taken a decade to figure this out)
7. Brand new technology (DSG) is often unreliable and problematic in the first year
8. Most "All Wheel Drive rally cars" are still very front weight biased, and chew up front tires quickly
9. You cannot race a car all year on a 275mm tire and then jump to a 245mm at the 11th hour without setup and performance repercussions
10. Without any controls on weight-related advantages, class winners tend to narrow down to a single chassis within each class

Now not all of this was learned immediately after this year in the EVO X, and not all of these things were the EVO X's fault. The DSG had been giving us a few clues as to its issues that popped up on Day 2, which cost Amy the win in STU-L.



Hanchey had done most of the track driving in this EVO X, often using the auto-shifted Super Sport mode that keeps the revs above 4000 - so it shifts a lot. Left Foot Braking tricked the trans into down shifting at times when it shouldn't have. Brian noted a "trans overtemp" condition about 8 or 9 times, even once or twice after we did the DSG fluid cooling mods above. We were worried about the SCCA Solo rules with respect to cooling mods, as well as potential warranty problems, so we just "dealt with the issue" as best we could by removing the fog light from in front of the DSG cooler. The DSG trans was so new that none of the local dealers could or would even service the fluid.



Starting in 2014 the STU class was thrown a major curve ball with the addition of the Nissan 350Z and Chevy Corvette C5 (non-Z06), both of which can run substantially wider tires than the previous RWD chassis that competed in this class (E36 M3). From that point on the once popular "AWD Rally car class" looked completely different, and the total entrant numbers that nearly topped 50 for many years in a row fell to 18 in 2014, 36 in 2015, 39 in 2016, and 29 in 2017. Nissan 350Z cars have won STU class for the 4 years in a row since.


During 2014 the S197 Mustang, C5 Corvette and 350Z were all lumped into STU. The S197 later moved to STP

How did this change in chassis dominance happen so quickly and completely? Well the suspension on a 350Z and C5 Corvette are both better than what comes on the E36 M3, Subaru STIs and Mitsubishi EVOs (McPherson struts). These two cars can also fit the 2WD STU class limit of 285mm tires, which is a damn sight larger than 245s. These two RWD chassis have Naturally Aspirated engines (3.5L V6 in the 350Z, 5.7L V8 for C5) that can also make pretty decent power within STU limits, unlike the S50/S52 engines in the E36 M3. And in STU trim the 350Z can dip into the 2900 pound range. So you have the lightest car, on the biggest tires (+40mm wider), with the same (300+ whp) or more power than anything else in class... confused as to why this 350Z is now the STU class overdog?



The EVO X never had a chance in STU, even before the dominant chassis changed from AWD rally cars to 350Z / Corvette chassis in 2014. It was always too heavy (I usually worked Impound and weighed STU class EVO VIII RS cars on the scales at 2950 lbs) and the rules did not allow us to get any substantial weight out. In their infinite wisdom SCCA precludes any tire-to-weight based rules in Street Touring and most other classes - the hard 245mm limit for all AWD cars handicaps the EVO-X massively.


Something as simple as even a casual look at what cars weigh could alter SCCA classes enormously

NASA does a much better job of creating rules around these weight related factors. Their rules are more based in measurable things like power/weight (ie: physics) than hearsay and old wive's tales. These are the most important aspects of rules within NASA:

1. Power-to-weight ratios are part of Every. Single. Class.
2. Tire-to-weight ratios and imbalances are addressed
3. Upgraded Aero is also factored into the P-to-W and T-to-W limits




I've had a number of great battles over the past decade in NASA Time Trial racing, and have even run against some EVO IX and EVO X cars in our shop Mustang and other cars. With the power-to-weight, tire-to-weight, and aero balancing that this series bases their rules around we have seen that it almost doesn't matter what chassis you start with - you can make a winner out of virtually any car, with the right amount of prep.


Racing rules that preclude a clear "chassis advantage" leads to much more car diversity within classes

There also seems to be much less of an advantage with AWD vs 2WD chassis when speeds get above about 45 mph in the dry and additional tire width from stock isn't prohibitive. This has shown to be the case up and down the grid within NASA, at all power and weight levels. Even in SCCA autocrossing, when the 2WD cars get a tire width advantage (245mm on AWD turbo vs 285mm on 350Z) the "AWD Advantage" also seems to go away. Exception is ProSolo, which always has a straight, drag race style start.



I am not going to explore all 10 points of things I have learned from the EVO X, other than to say "racing is complicated". We welcome you to read our other posts on this forum to see all of these detailed extensively.

WHAT'S NEXT?

Thanks for catching up with us! That will be the last post I write about a particular car that we stopped developing and driving in 2009. We have another EVO X in the shop right now getting a roll cage and many other upgrades, which I will detail in future posts.



We have since found ways to get weight out of the EVO X chassis, as this one lost 447 pounds in about two days, before we started adding the roll cage. An EVO X race car will likely never be as light as an EVO VIII or IX, but the small differences once prepped don't really matter when you are running in a power-to-weight restricted class. We will go over this and more next time.

Cheers,
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