Jump to content
TEAM SHELBY FORUM

Autocrossing 2009


ilmor

Recommended Posts

Well, I had planned to autocross my SGT on Sunday, however now there is rain in the forecast. I guess I'll keep an eye on that, and hopefully it will improve and I can go. Wet weather autocrossing is no fun to me.

Link to comment
Share on other sites

The weather decided to cooperate after all, so I'm heading to the autoX. I set up my iPhone on the console so I can try out my G Force & Pocket Dyno apps just to have a bit of extra fun. I don't expect to do so great on my all-weather BFG's; I really just want to wind out the SGT a little bit and flex its muscles!

Link to comment
Share on other sites

Whew! That AutoX was fun, and a workout!

 

First of all, it was a gorgeous spring day in CT, 70’s and sunny – we couldn’t have asked for better weather. Sorry, no pics though – yet – our club website will post some I’m sure, which I provide a link to later when that’s done.

 

I had to carry the Shelby banner alone, as the only Shelby present. There were 3 other Mustangs there, but none in my class. I was classified F/S, and they put me with the A/S group (they always do that for some reason) to eliminate any chance of me getting a trophy, but I knew that would happen and was only there for the fun anyway. I was wearing my Team Shelby shirt!

 

When I went thru tech, one guy suggested that I need to turn in F/SP when he saw my intake; however the other fellow knew of the car and told the first guy, “nope, that’s stock”! to the first guys surprise.

 

My cold tire pressures were 32 all around. On the first run, I hit one cone and ran a 39 second run. The car felt like I was sliding around on ice! On the second run, I ran a 38.5, but still way to slippery, and I hit 2 cones.

 

I checked my pressures and let 3 lbs out of the front and 2 out of the rears so the tires were now 32 psi all around hot.

 

On my third run, I ran a 39 flat and hit no cones. This time I also used my iPhone G-Force app. It measured max’s of .75 G’s accelerating and braking, and 1.2 G’s on left & right turns.

 

On the 4 run, I ran a 38.55, clean also. On this run, at the slowest corner, I downshifted to 1st gear and nailed the throttle down the one part of the course that was a straightaway, then 2nd for no more than a couple of seconds, then hard brake for the hairpin. On this run the G-Force measured .94 G’s max acceleration, .75 G braking, 1.02 G left turn and 1.25 G right turn.

 

Following this run, the announcer stated over the loudspeaker – “Bob, someone in our booth here wants to drive your car on the next run to make sure it’s not illegal” – he was kidding, but that gave me a laugh.

 

My 5th and last run was the best, at 37.8 seconds. The G-Force measured 1G acceleration, .79 braking, 1.10 left turn and 1.24 right turn.

 

That was it for the day. I headed home (about a 30 minute cruise) w/ the windows down. On the way back two old muscle cars passed in the opposite direction and we traded waves.

 

Truly a good day in a Shelby GT!!

 

Edit - Oh yeah, the stock BFG's are really crappy!! I noticed that my competitors were all running Bridgestone Potenza RE050A's.

Link to comment
Share on other sites

Way to go Ilmor... I've never done the AutoCross stuff before... Always been a fan of the track events :shift:

 

Gregg

07SGT0547

 

You should try it sometime!

 

I love being on the race track the most, but haven't done it in almost 10 years now. I hope to get the SGT out on one in October (meeting a buddy of mine who is now an instructor as Summit Point, WV).

Link to comment
Share on other sites

Can you run 255-mm wide tires for F Stock, or do you have to stick with the stock 235-mm size?

 

My understanding is that as long as you are using the stock or stock-size wheels, its OK to run the wider tires.

 

Edit - here is a good modification refererence list. http://www.sff.net/people/dburkhead/prepcompare.htm

 

 

In our club, "race rubber" is not allowed on stock classes, i.e., they must be "street" tires.

Link to comment
Share on other sites

Well, unfortunately there were only 2 pictures taken of me and neither has my car on track! How boring, I know...

 

In this one, I'm the guy in the blue Team Shelby shirt standing in line to sign up...

 

04190935.jpg

 

 

...and in this one, you can spot my SGT in the "pits" during the course walk.....

 

 

04190970.jpg

 

 

....and on this web page, if your interested in the details you can see all the info; results, event photos and coverage for April 19th...

 

http://www.cartct.com/auto_results.shtml

 

Hopefully I'll be more photogenic in the next autocross!

Link to comment
Share on other sites

Cool! Liked the results...evo won raw time, but then he had to be seen in it haha!

 

I put my numbers where you did as well I want to get a magnetic sheet of whit and make a "cover for the rear windows with the number I am #471.

 

On the results page you are listed as A/S, you were in F/S though right?

 

 

Cheers, Awesome!

Link to comment
Share on other sites

Cool! Liked the results...evo won raw time, but then he had to be seen in it haha!

 

I put my numbers where you did as well I want to get a magnetic sheet of whit and make a "cover for the rear windows with the number I am #471.

 

On the results page you are listed as A/S, you were in F/S though right?

 

 

Cheers, Awesome!

 

 

Yes, I was the only car in F/S. I think unless there are at least 3 cars in a class, they move you to A/S and classify you as such. I don't understand that at all, but....

 

I would also like to get the magnetic material and do the same. I need to make sure I run every year at least a couple of times to keep my number, however. Two years ago I was #212 I think, and I didn't autox at all last year.

Link to comment
Share on other sites

Great post. :drool: I have always wanted to do an autoX but not having the right car and a not so supporting wife :rant2: , kept me out of it. My 2007 SGT has just under 5K miles on it right now so I am comfortable that it is broken in.

 

Last year, our club sponsored the MCA Grand National show here in Park City. We have Miller Motorsports Park as one of our sponsors. They set up an autoX course in the ski resort parking lot. This year we are moving to a hotel closer to town for our Intermountain Mustang show on 8/14 & 8/15. Shameless plug inserted here :hysterical:

 

Miller Motorsports is letting us hold the autoX, if you can call it that, on one of their road courses ot the track this year. It will be a little over 2 miles long. They setting up cones on the straights to keep the speeds down. They will have timing gear set up as well as EMTs and the safety crews on hand. All entrants will be classified in groups of similar cars

 

You get 30 minutes of driver training, one escorted lap, two practice laps and 2 guaranteed timed laps, or more if the daylight holds up. You also get 2 catered dinners. All of this for $135 per driver.

 

This may not be your typical Sunday afternoon parking lot autoX but it will be my first time to legally see what my car, and I, can do. :shift: :happy feet:

 

Good luck to you. Keep us posted on how you do over the summer.

Link to comment
Share on other sites

This may not be your typical Sunday afternoon parking lot autoX but it will be my first time to legally see what my car, and I, can do. :shift: :happy feet:

 

Good luck to you. Keep us posted on how you do over the summer.

 

Sounds great, and I'm sure you will enjoy it! One thing I was wondering about - should I ever get a supercharger I think the car would have uncontrollable power on an autocross course!! The SGT really moves about quickly as is w/ the N/A 4.6!!

Link to comment
Share on other sites

Sounds great, and I'm sure you will enjoy it! One thing I was wondering about - should I ever get a supercharger I think the car would have uncontrollable power on an autocross course!! The SGT really moves about quickly as is w/ the N/A 4.6!!

 

I came around a sweeper last year so insane on the throttle (and smoking sideways...slow way around) that I could see the course workers scatter in my periphieral vision... :hysterical: You can really throttle it around...super duper fun, I like it right before it goes squirrley :happy feet:

 

I am really wondering the same, now that I have the s/c... There were some big HP cars out there last year at Bremerton including a well modded and s/c'd Viper, built Cobra and a few modded Vettes. My instructor who was really great kept referring to the SGT as "high hp" for autocross it is at the 319, which is what SWEDE and I had beeen going around about on the old forum. These cars stock are so fun on a autocross track, I was hooked instantly. It is real easy to go real quick in the SGT. Gotta love it!!

 

I am really thinking that the S/C will come in handy in the Pro-Solo drag starts. I am not sure what class I will be in however?

 

Anybody know?

 

F/S is out as even though the S/C is "factory" it moves you into something else I believe. N/A SGT's rule the F/S class nationally as you know.

Link to comment
Share on other sites

I did know that the Shelby GT is the F/S national champion car, which is awesome. A Shelby GT has won all three national events in F/S so far this year.

 

190.jpg

 

By the way, as a follow up, my cold tire pressures for my autox were 30 front, 31 rear. At my next autox I might try taking out another 1/2 lb. in each to see what happens. I'll take my air tank w/ me just in case I need to pump back up.

Link to comment
Share on other sites

I love this "autocross" stuff. When I started (first event was in 1958, in an MGTD) it was called "slalom"; come to think of it, it was still called slalom when I quit (last real event was like 1979). Whatever it's called, it's great fun, a real test of skill and car setup, and as close as you can get to track days without worrying about the po-lice.

 

I was a competent slalomer in several cars and an excellent slalomer in one car, a 1966 Lotus Elan, a car built by a genius who somehow managed to translate his genius to the users of his products. In various cars I won a number of trophies, class wins, and a couple-three yearly championships in class. Cars I used regularly were the MGTD, an Austin-Healey 3000, an MGB GT, an MGB roadster, the Elan, a Vega Kammback, a Vega GT coupe, a TR7 convertible. I drove a Ferrari Dino in a couple of events (same class as the Elan, so the first-place points counted) and a Toyota MR2 once that I remember. There may have been others, but it was a while ago.

 

After a 20-year layoff, I drove my Mustang V6 convertible in half-a-dozen or so autocross events, and the GT/CS coupe in another.

 

I mention that history not to impress anyone with my accomplishments, modest as they are, but to indicate I've been thinking about the essential and arcane aspects of autocross/slalom for quite a while. As is true for every question about performance driving, there is usually more than one answer, more than one solution to every challenge. So many variables influence performance that it's hard to make meaningful, concise statements about any of them.

 

Just get a load of the problems related to tire pressures: when dealing with racing tires, it is usually best to ensure that the entire width of the tread stays in contact with the road surface. Over- or under-inflation may cause the tire tread to bow and reduce the traction available across its face. In a road tire, that effect is less likely to occur, but another contact patch-reducing phenomenon can have a similar effect, allowing the inner edge to lift off the ground.

 

I think the compromises built into street tires - flexible sidewalls and relatively rigid belts, thick tread - mean over-inflation has less of a deleterious effect than under-inflation. The tread belts do a good enough job of keeping the tread flat to compensate for the slight bowing of over-inflated tires. In a street suspension, the wheel is going to lean to the outside of a turn, and the majority of cornering power is from the outside half of the tire, anyway.

 

For my part, I like the slightly crisper response of a radial tire that is inflated to ten or fifteen percent above the factory recommended pressures. It's my impression that standard or under-inflation results in the steering inputs being delayed while the tire sidewall bends and takes a set; that delay is still present with more pressure, but is a shorter one, and allows for more precise timing.

 

With GT-takeoff swaybars and Pirellis/Bullitts on the V6 convertible, I'd start the day with 40 PSI front and 35 PSI rear. Turn-in was quick and predictable, and the no-limited-slip rear came around pretty good. It seemed to me the tread blocks were wearing as evenly across the tread as could be expected, given the lack of special adjustment in the alignment. The stock tires with tall tread were definitely "greasy", but the sliding was controllable and predictable. You'll find the fast guys buy their fancy "street" tires and immediately have them shaved to eliminate the block-bending that reduces accuracy and G-capability. The Potenzas you mentioned start with about twice as much tread depth as they have when a serious racer will put them on the course.

 

Lowering the pressures by three pounds at both ends seemed to work best for those tires and that setup.

 

Later on I had stiffer sway bars on both ends, and wider wheels and tires (9/10x19 inches vs 17x8 stock; 275-35 vs 235-55 stock). That really hooked up, and kept the tires even flatter on the ground. Adjusting the front swaybar and the adjustable shocks, it eventually was practically neutral-steer with over- and under-steer available through application of technique. It worked great, was great fun to drive, but way to heavy for the task at hand.

 

After all that "development", my V6 performance improved from ranking about 135th to 110th overall, out of maybe 150 entrants. Then I got the Potenzas ( RE-01Rs @ 245-45x18 on SVT "fanblades" 18x8.5). They felt much stickier on the street, and they were stickier on the track. I didn't have them shaved, and my performance was improved markedly; and they say tires in those conditions don't "come in" to their full potential for two or three events. Using good equipment made it clear that I no longer had the reflexes to keep up with the machine, and I haven't run a competitive autocross since that first effort with the fancy tires.

 

I did do a practice event, a dozen runs or so, in the GT/CS on the stock BFG KDWSs, when the car had about 350 (three hundred fifty) miles on it. I was delighted with how well it answered the helm with stock everything and tall tread blocks. I used 38 PSI front and 35 PSI rear, cold.

 

The point of this is to say (aside from I don't think you'll be able to notice a half-pound difference in pressure with heavy street tires) were I you, I'd inflate to 40 front and rear, cold, the night before the event. Measure it again in the morning before leaving the garage, and start with even pressures at the lowest one you find. Make a run and see what happens. If under-steer seems to be a problem, let two pounds out of the rears and try another. If it seems to be going the wrong way, let four pounds out of the other end. You'll be able to test two things - if lowering pressure increases traction and what is the effect of differing pressures front and rear - and still have room for adjustments without going to the tank.

 

If you are serious about autocrossing, there are books and videos by experts, many of whom are actually qualified to give pointers. Horsepower is nice, but not the most important thing in autocross. Practice is. Experience. Next is tires, then suspension.

 

I hope you enjoy it as much as I did. Good luck!

 

LotHV01o.jpg

Link to comment
Share on other sites

Thanks, I appreciate and understand all your very good points . As for me, I've been autocrossing since the early 80's, and was involved in amatuer road racing for for over 10 years. I have a number of 1st and 2nd place trophy plaques to show for all that fun. I used to see all the cars you mentioned and drove from time to time and they were great! We don't see those much anymore.

 

Based on my experience in my Shelby GT w/ the KDWS, I started with them at 32 all around, and the car was like it was on ice. When I reduced the pressures, the grip improved considerably. I will try your recommended high pressures next time, but I don't think that will work. Even at the lower pressures I used, the tires were not rolling over onto the sidewalls noticably at all. I attribute this to a very well set up Shelby GT suspension. The car was extremely flat and neutral, but these KDWS just aren't able to cope with that and the power.

Link to comment
Share on other sites

Thanks, I appreciate and understand all your very good points . As for me, I've been autocrossing since the early 80's, and was involved in amatuer road racing for for over 10 years. I have a number of 1st and 2nd place trophy plaques to show for all that fun. I used to see all the cars you mentioned and drove from time to time and they were great! We don't see those much anymore.

 

Based on my experience in my Shelby GT w/ the KDWS, I started with them at 32 all around, and the car was like it was on ice. When I reduced the pressures, the grip improved considerably. I will try your recommended high pressures next time, but I don't think that will work. Even at the lower pressures I used, the tires were not rolling over onto the sidewalls noticably at all. I attribute this to a very well set up Shelby GT suspension. The car was extremely flat and neutral, but these KDWS just aren't able to cope with that and the power.

 

Gentlemen,

 

My autocrossing experience dates from the early 80s running a 911SC and a 944T. As a local PCA "instructor" I also had the privilege to drive corvettes, ferraris , and Trans Ams of that era. Frank's recommendations of starting out high in terms of air pressures with higher pressure differentials at the higher weight end of the vehicle worked well back then. After every run I would run my hand across the tread of all four tires. I was looking for even apparent temperatures across the tread. I suppose these days you would use a pyrometer. I always had a tire pump on hand to make small adjustments. You want 100% of the tire working for you at all times. That doesn't happen with under or over inflation. Certainly better tires will make a difference but the goal of optimizing balance and traction remains the same.

 

At the end of the day it's the timer that tells you if your strategies are working.

 

Good luck and let us know what you discover.

 

jpl

Link to comment
Share on other sites

Gentlemen,

 

My autocrossing experience dates from the early 80s running a 911SC and a 944T. As a local PCA "instructor" I also had the privilege to drive corvettes, ferraris , and Trans Ams of that era. Frank's recommendations of starting out high in terms of air pressures with higher pressure differentials at the higher weight end of the vehicle worked well back then. After every run I would run my hand across the tread of all four tires. I was looking for even apparent temperatures across the tread. I suppose these days you would use a pyrometer. I always had a tire pump on hand to make small adjustments. You want 100% of the tire working for you at all times. That doesn't happen with under or over inflation. Certainly better tires will make a difference but the goal of optimizing balance and traction remains the same.

 

At the end of the day it's the timer that tells you if your strategies are working.

 

Good luck and let us know what you discover.

 

jpl

 

Also very good points.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...
...