2022 Autocross season in review -

[Davemk1]

Well, the snows of have winter have arrived in the Northwest region of the USA and this makes it a good time to look back on this past season of autocross competition in my 2014 Westfield Mega S2000. I had a good set of results this year so I apologize in advance for the following humble-brag.

 

I made some changes to the car before the season started that really made the car quicker and easier to drive at the limit. The biggest single change was the installation of the +35 mm wide track front suspension kit from the good people at Siltech racing. This really made the car easier to drive and more intuitive at the limit…the place it was really felt was that I’m now able to stay on the gas during rapid lane changes or slaloms. In the past I’d have needed to mind the tail coming around and eased off a bit to keep it in line. With the Siltech wide A arms and a ARB that I made the nose turned in very sharply but the tail stayed in line even when on the throttle. Stay on the gas, turn in violently and everything does what one would want it to do. It’s wonderful.

 

I also changed the alignment some to deal with the inherently high slip angles of the wide Avon slicks I’m using. I now run 2mm of toe-out on each front tire, 2mm of toe-in on each rear tire and 1.2° of camber all around. This really aided turn-in without having to keep the tail in line and combined with the new front suspension the car went from very good to great.

 

Here’s a few of this year's stats - 

 

17 days of competition

17 times setting FTD (Fastest Time of Day)

172 runs in total over those 17 days

1 set of Avon A15 compound slicks used to the full

0 mechanical breakdowns

2 times setting fastest PAX time (a handicap factor based on the car’s potential/class so that cars of different classes can be compared)

3 second place PAX finishes

11 top five PAX finishes

Largest winning margin over 2nd place - 6 seconds. Smallest margin - .6 seconds

Lastly - I set a new fastest ever time on our club’s “Index Course” where we can compare times to those set all the way back to 2012. I held the previous fastest Index time and beat it this year by .4 seconds on a very hot (slow) day.

 

 

I’ve got some plans to make the car better balanced next year which should help the handling even more. I’ll be modifying the fuel tank so that it will carry nearly all of its load on the passenger side of the car which should benefit the handling. I’m already at the minimum weight for my class (1420 lbs or 644kg for the car with me in it) but I’ll be taking some more weight out of it so that I can bring it back up to minimum weight with ballast on the passenger side to further help with right/left weight distribution…in effect I’ll be shifting weight to the passenger side of the car. And lastly I hope to install Siltech Mirco Adjust rear A arms to get rid of the one rubber bushing left in the suspension and to make toe and camber adjustments more precise and easier. Winter is long in Montana so I have plenty of wrenching time over the coming months.

 

If anyone is interested in Autocross and I can help in any way please let me know. It's so much fun. I'm already excited for next season...it's only 6 months away!

 

Thanks for reading,

 

Dave

[Ian Kinder (Bagpuss) - Joint Peak District AO]

Fantastic results. Thanks for sharing!

 

[LoneWolf]

Sounds like you had great fun 😊

Any video where we can see your car (and you) in action?

[IainCameron]

Very impressive stats.  I'd be very interested to know how front toe-out helps steering under throttle; it sounds counter-intuitive to my ill-educated mind.

Do you have any idea how your spoiler affected performance?  I recall the debate during the design and installation phase, but it clearly didn't act like the air brake that it looks like! 

I find it a fascinating balance (about which I know nothing) between down-force, drag, suspension geometry, etc etc, and it would be interesting to hear how you worked it out.

[Davemk1]

Thanks for the questions.

 

I don’t think I would say that front toe-out helps specifically with turn-in under throttle…I would say that front toe-out helps with turn-in under all conditions. It’s my understanding that toe-out helps because it preloads the tire’s slip angle meaning that there is less time taken up with waiting for the slip angle to build before one gets an actual change in direction. The bias ply slicks I use have awesome ultimate grip but their construction means that the slip angle is very high compared to a radial street tire…and that means that the turn-in response can be slow. I have definitely found that the front toe-out helps to get the front to dig in and head in the new direction much better.

 

Also of benefit on turn-in is using the short steering arms which give more Ackerman effect…which means that toe out increases as the steering comes off center. The greater the steering angle the more toe-out. So on slower and tighter corners there is huge toe out and very aggressive turn-in and at lower steering angles it’s less aggressive.

 

 

 

The performance benefit from the rear spoiler is harder to define. At lower speeds I’ll bet it does very little to add grip. At the same time I also doubt it adds much in the way of drag at low speeds so there is very little downside. The spoiler weighs only 1 pound so the added weight is of little concern. At higher speeds it feels like the car is better planted in the rear. On a smaller and tighter course my high speed will be only about 60 mph to 65 mph but on larger more open courses I’ll see about 85 mph. So my guess is that on smaller courses that the benefit of the spoiler is small and for only a short period of time (when at peak speed) but on larger courses much more time is spent at 60-80 mph and there the benefit feels more obvious. It does act as an air brake I suppose but I always have more power than grip so the added drag is OK as long as the car stays stuck to the floor.

 

In the end it’s a matter of “accumulation of incremental gains” and none of the small changes alone amount to much. But if the spoiler drops .1 seconds (on a 60 second run time) and the front toe drops .1 seconds and the closed underbody drops .1 seconds and the front splitter drops .1 seconds……etc….pretty soon you have a can that is easier to drive faster and you’ve dropped 1/2 second…and 1/2 second is a solid winning margin.

 

 

 

When I started autocrossing 20 years ago I assumed that the fastest cars must be very difficult to drive. After all my slow car was hard to drive so going faster must be even harder. I clearly had this wrong. The fastest cars are the easiest to drive and that’s the thing that makes them quick. When I first built the Westfield in late 2014 my car was hard to drive. It was a lot of work. It understeered and oversteered and was unpredictable and hard to read. Now it’s easy and any reasonably skilled driver would be quick in it first time out. It’s really fun!

 

Dave

[Davemk1]

6 hours ago, LoneWolf said:

Sounds like you had great fun 😊

Any video where we can see your car (and you) in action?

 

I shared this video some time back and it's the only one I have. I apologize if it's a repeat for you.

 

This was taken at an event this past spring at a local very small church parking lot. This is about as small, tight, slow and technical as autocross gets. My top speed on this course is about 63 mph (100 kph). Considering that the parking lot is only 450' x 250' hitting 63 mph while also constantly changing direction it feels plenty quick.

 

But this will give a little bit of a feel for what it looks like.

 

dave

 

 

[Davemk1]

I found another video taken that same day, on the same course, but from a slightly different perspective. It's interesting to see the tires right on the edge of letting go so much of the time. That's a really cool feeling.

 

dave