Good Guys Dual in the Desert- CSX3170

Cobra #3170 · #1 (**permalink**) 11-23-2015, 11:28 AM

Hi Guys Good News and Bad News,

Bad News, we lost again, Good News CSX3170 had the fastest scratch time of the weekend and finished 3rd. We also had more runs in the 65 second range than any other car but had a little pylon trouble.

The story: We brought a great handling car to the shoot out but that was the wrong approach as we found Friday during the practice sessions.
The car needed an evil handling snap over steer set-up to work on the tight little track that was laid out. We were 2 seconds off the pace Friday despite shock, sway bar, tire pressure and rear ride height adjustments.

The fix: Friday night we went through our computer data and previous set up approaches over multiple beers and decided that a very radical change to the car was the only thing that might give us a chance. We had installed a new splitter that I mentioned previously on CC that required a slight increase in front ride height and spring rate. I designed the front suspension around a 3" front ride height and we were now at 3.25" so we decided to go back to basics and dump the splitter. Saturday morning we went back to the track at 6:00 AM and used the truck headlights to unload the car and get it on jack stands with all 4 wheels off. we set the front up for a front ride height at
3.00" with 2.5 degrees of camber and .125" of toe out and 450 lb front springs. I reset the bump and rebound of the shocks to our standard autox
settings. We raised the rear ride height to 4.125", added 2" of rear bar, decreased the bump by 2 clicks and increased rebound by 2 sweeps in an effort to improve power down and increase throttle off over steer. We also switched to 315 Rival rear tires in place of the 335's to make the car over steer. We got done just in time to make the first run of the day. Tires were 275x18 Bridgestone fronts at 28 PSI and 315x18 Rival rears at 23 psi.
The car was a lot better but was still not putting power down well. Scott was checking car over just before qualifying and found the throttle cable frayed and ready to break. We got permission to miss the first qualifying session as long as we made the second one at 1:00 pm. We took the car back to our trailer and installed a new cable (so lucky I had a spare made when I did the original). We decided to reinstall the 335x18 rears and set them at 21 pounds and .5 degree less camber for a total of 1.75 degrees on the rear. We just made qualifying session 2 in time and the car was right there with everybody else that was fast (Danny Popp,
Jr. Johnson) We were finally competitive, but Scott had no time to learn the nuances of the new set up. He made it through the ladder to the 4th round and got beat by JR Jonson in a Corvette by a few hundredths.
Scott also clipped a pylon on that run. He then had a run off for 3rd place and won that with a time that was fastest of the weekend (65.1)but also clipped the same pylon. We looked at the computer and saw that he could have run a 64.5 time. In fairness to Scott he could have been very competitive if he only had more time in the car with the correct set up but that is racing. I have never set the car up with this much over steer and would not even try it any place else.

PS the engine ran great this time, so our Arizona EFI tune was good.

This is a short video about the event that you might enjoy.

https://m.youtube.com/watch?feature=...&v=JgHo19bbB6w

Nedsel · #2 (**permalink**) 11-23-2015, 11:40 AM

Bruce, you did great. Congratulations you you, Scott, and 3170.

Cobra #3170 · #3 (**permalink**) 11-23-2015, 12:07 PM

Quote:

Originally Posted by Nedsel

Bruce, you did great. Congratulations you you, Scott, and 3170.

Thank You Ned, it means a lot coming from you. We are beginning to get a handle on what it takes to make the car work under different conditions. It is just taking me too long to get it there.

Grey 65 · #4 (**permalink**) 11-23-2015, 01:15 PM

Bruce, It looks like I snuck into the video at the 3:45 second mark..... It seems all Cobras look alike to the guy editing the film......

2016 will be your year......

Kevin....

LMH · #5 (**permalink**) 11-23-2015, 01:53 PM

Nice job! I know someone who was competing in the Optima Battery Challange series but didn't see her in the video. I'll have to find out if she was there.
She has a yellow Lotus.
Larry

Cobra #3170 · #6 (**permalink**) 11-23-2015, 02:40 PM

Quote:

Originally Posted by LMH

Nice job! I know someone who was competing in the Ultima Battery Challange series but didn't see her in the video. I'll have to find out if she was there.
She has a yellow Lotus.
Larry

I believe that might be Alexandria Zust aka Julie Weichert driving a yellow Lotus.
The dual in the desert is for 1972 and older cars only so the Lotus would not be eligible to run. Many of the Optima Cars are older muscle cars so they are eligible. We are contemplating another run at the Optima but not with the Cobra this time have not chosen a car yet though.

LMH · #7 (**permalink**) 11-23-2015, 02:49 PM

Yes, that's her. I thought she'd be at that meet you were at but guess not. Alex is a fierce competitor and a really nice person to boot. She was down to Inde to drive with us a few weeks ago.
Larry

Cobra Chris · #8 (**permalink**) 11-23-2015, 06:29 PM

Loved to see you out there again...Nice to see that car used for what it was made for...Drive the heck out of it..

Chris

DAVID GAGNARD · #9 (**permalink**) 11-23-2015, 07:32 PM

One word comes to mind:

OUTSTANDING.............

David

REAL 1 · #10 (**permalink**) 11-24-2015, 06:04 AM

Bruce: Great work. Scott too. Keep the Shelby Cobra running with the big dogs!!!

Not bad for a 50 year old car!!!!

cobrajeff · #11 (**permalink**) 11-24-2015, 06:30 AM

Congratulations Bruce and Scott! Well done!

That looks a little more sophisticated (and probably more expen$ive) that what we used to do in the North Lot of Ford World Headquarters about four decades ago

Jeff

Ron61 · #12 (**permalink**) 11-24-2015, 06:59 AM

Thanks for posting the video and congratulations on your finish. It is great to see the original Cobras still running with a great deal of success.

Ron

rodneym · #13 (**permalink**) 11-24-2015, 07:12 AM

Always makin' us proud, Bruce!
Great job.

TimG427 · #14 (**permalink**) 11-24-2015, 08:01 AM

Great video, I'd love to watch in person some time.

Snake2998 · #15 (**permalink**) 11-25-2015, 03:25 AM

Thanks for posting - I enjoy your notes re suspension set up - am always amazed that you find that even 1/4" difference in ride height makes a noticeable difference in handling. You have certainly taught me something. (I know that my driving skill level is way below being able to notice the impact of such changes - you have convinced me to concentrate more at increasing my sensitivity to what my car is doing on track days)

Keep posting with lots of detail.

Cobra #3170 · #16 (**permalink**) 11-25-2015, 05:40 PM

Quote:

Originally Posted by Snake2998

Thanks for posting - I enjoy your notes re suspension set up - am always amazed that you find that even 1/4" difference in ride height makes a noticeable difference in handling. You have certainly taught me something. (I know that my driving skill level is way below being able to notice the impact of such changes - you have convinced me to concentrate more at increasing my sensitivity to what my car is doing on track days)

Keep posting with lots of detail.

Thank You,
We actually adjust ride height by as little as .1" and it will effect handling.
It shifts the roll axis which in turn shifts tire loading between the front and rear wheels. Once you are happy with spring and bar rates it becomes a fine tuning tool that can be used on the grid very quickly. We normally operate in a vary narrow range +/- .1 " but in this case we had to get a major shift to over steer so the big difference in ride height. I would rather do it with springs and keep my roll centers at optimum location but this worked well and did not hurt power down. We also found that a 3.73 rear end ratio with a Trac Loc differential was the best choice at Good Guys, We tried a 3.54 and a Torsen TR-2 Diff. but it did not like the amount of torque we put through it.
I would go back to the 3.31 for big tracks and use this set up for Good Guys only because a high ratio is actually slower than a low ratio that does not spin the tires so easily. We found that starting in second was faster than using 1st on the big american autox courses. We also ran a Salisbury diff but found that it under steered too much on tight corners. Robby Unser loves them but they don't seem to work well in a Cobra weight vehicle. We are discussing running the early March event in Scottsdale with this set up so we can develop it for the entire event then we will have something that works
on Friday morning in November 2016. Rival is changing their tire construction next year and Bridgestone is coming out with a 285x18 so some tire testing will be in order too. I don't know if I mentioned it but we are pulling over 1.45 G's now in corners on concrete we have gained .1 g every year
since 2014. We also get 1.2 G acceleration to about 60 mph and are still pulling .9 at 93 mph, all on concrete of course, with 200 TW tires.
We only got 1.31 at Scottsdale but not bad on asphalt.

Snake2998 · #17 (**permalink**) 11-25-2015, 10:58 PM

Quote:

Originally Posted by Cobra #3170

Thank You,
We actually adjust ride height by as little as .1" and it will effect handling.
It shifts the roll axis which in turn shifts tire loading between the front and rear wheels. Once you are happy with spring and bar rates it becomes a fine tuning tool that can be used on the grid very quickly. We normally operate in a vary narrow range +/- .1 " but in this case we had to get a major shift to over steer so the big difference in ride height. I would rather do it with springs and keep my roll centers at optimum location but this worked well and did not hurt power down. We also found that a 3.73 rear end ratio with a Trac Loc differential was the best choice at Good Guys, We tried a 3.54 and a Torsen TR-2 Diff. but it did not like the amount of torque we put through it.
I would go back to the 3.31 for big tracks and use this set up for Good Guys only because a high ratio is actually slower than a low ratio that does not spin the tires so easily. We found that starting in second was faster than using 1st on the big american autox courses. We also ran a Salisbury diff but found that it under steered too much on tight corners. Robby Unser loves them but they don't seem to work well in a Cobra weight vehicle. We are discussing running the early March event in Scottsdale with this set up so we can develop it for the entire event then we will have something that works
on Friday morning in November 2016. Rival is changing their tire construction next year and Bridgestone is coming out with a 285x18 so some tire testing will be in order too. I don't know if I mentioned it but we are pulling over 1.45 G's now in corners on concrete we have gained .1 g every year
since 2014. We also get 1.2 G acceleration to about 60 mph and are still pulling .9 at 93 mph, all on concrete of course, with 200 TW tires.
We only got 1.31 at Scottsdale but not bad on asphalt.

Thanks - fascinating info. If I lived in the USA I would be begging to spend some time in your pits.

Cobra #3170 · #18 (**permalink**) 11-26-2015, 05:33 PM

Here is a video of one of the 65 second runs, you can see how tight the course is.

[ame]https://www.youtube.com/watch?v=a5W9eZEiE5I[/ame]

cobrakiwi · #19 (**permalink**) 11-26-2015, 06:08 PM

Very cool, so great to see your car doing what it does best!!!
Congrats.

twin turbo · #20 (**permalink**) 11-27-2015, 09:19 AM

That is such a tight course it is almost absurd. It amazes me all the fine tuning involved when tailoring your car to each course. Kudo's to you to for being able to solve the puzzle.

On a side note, around 1.1 G's acceleration is the max limit my tires will hold on the street with drag radials. That's impressive you can hold down 1.2 G's. Cheers.