Traction Control

[Cobra #3170]

Scott and I spent almost all day yesterday tuning the FAST XFI 2.0 traction control. Although I have been critical of the FAST XFI systems inability to learn quickly in the past I have to say the traction system is excellent. I have a 45 tooth reluctor wheel mounted to the differential driveshaft flange. I used a GM truck ABS sensor that costs about $14 and is way cheaper than earlier sensors. It is mounted to a bracket mounted on the differential. I built a circuit than converts its voltage variations to a 5 volt square wave pulse so the FAST system can read it. We set up a marked strait of about 150 feet and Scott would floor it at the first marker and let off at the second marker.
THE fast system records engine rpm, drive shaft rpm, MPH, drive shaft acceleration rates, throttle opening, spark advance all vs time as I have it set up.
We adjusted the following factors:
The amount of drive shaft acceleration before intervention
The minimum speed before intervention
The amount of timing retard
The time before reacting to detected slip
The amount of time before full timing is ramped back in
The slope of the intervention curve

I have to say the system worked wonderfully well we went from 70 mph for the test distance to 76 mph. The acceleration peak was also flatter and more sustained using traction control. We made up 4 different programs for use on different surfaces depending on available grip. The system picks up wheel slip before a complete revolution of the rear tire and way before Scott can feel it
We can now use full available throttle body opening instead of disconnecting the secondaries. We retard the spark a maximum of 20 degrees for short periods of time so it will not hurt the engine either. No ignition cut that pounds mechanicals either. I have a couple of crappy Iphone videos of the runs but do not know how to post them here. All in all a very productive day. We will try it in competition next weekend at Goodguys in Pleasanton.

[twobjshelbys]

Upload your videos to Youtube and post the link.

What you are doing is incredible. What's your next appearance?

[Cobra #3170]

Traction control video: https://www.youtube.com/watch?v=MAnL2KlY8no 0 to about
74 mph

Hi Tony,
We are running Pleasanton Goodguys this weekend, then the CAM invitational in Lincoln Nebraska followed by Solo2 Nationals on Tuesday and Wednesday then the Loveland Colorado Goodguys September 7-9. I still have some mechanical work to do between now and Thursday so I am going to be busy!

Scott gave a friends 15 year old daughter a ride in video, she said it made her neck hurt. She really liked the ride though.

[twobjshelbys]

I'd love to see you run. I went to the Loveland Good Guys with the Cobra and GT, but then we moved to Vegas. We are going to be in Colorado the week before for the Shelby American Collection fundraiser party on Sat 1-Sep. Are you going to be in CO then? If so you should come down to Boulder and drop in. It's a big deal with lots of the original Shelby crew. Carroll used to come. I'm sure your car and story would draw a lot of attention.

[Cobra #3170]

Originally Posted by twobjshelbys

I'd love to see you run. I went to the Loveland Good Guys with the Cobra and GT, but then we moved to Vegas. We are going to be in Colorado the week before for the Shelby American Collection fundraiser party on Sat 1-Sep. Are you going to be in CO then? If so you should come down to Boulder and drop in. It's a big deal with lots of the original Shelby crew. Carroll used to come. I'm sure your car and story would draw a lot of attention.

I am sorry Tony we will be in Nebraska on the first and not back in Colorado until the evening of September 6th. We will be entered in the big shootout at years end in Scottsdale Arizona on November 16 - 18 if nothing breaks between then and now.

[Snake2998]

Very interesting, thanks for posting this. What impact will it have on the handling of the car around corners? Especially when you come back on the power after the apex, will you be able to come back on harder and earlier?

[Gaz64]

Originally Posted by Snake2998

Very interesting, thanks for posting this. What impact will it have on the handling of the car around corners? Especially when you come back on the power after the apex, will you be able to come back on harder and earlier?

I would say should be able to drive as hard as you like now, so much faster overall, and much easier to drive.

[Cobra #3170]

Originally Posted by Snake2998

Very interesting, thanks for posting this. What impact will it have on the handling of the car around corners? Especially when you come back on the power after the apex, will you be able to come back on harder and earlier?

Yes it is more stable in the corners and exits much quicker.

UNFORTUNATELY IT WORKED SO WELL THAT IT FAILED MY LH UPPER DIFFERENTIAL MOUNT. We are dead in the water and may not make any upcoming events including the Nationals. I don't know if I can replace it without removing the rear bulk head so very bad news.

[1795]

Sorry to hear that. You have put so much work and ingenuity into the car. Unfortunately that is what tends to happen in racing; we take things to the edge performance wise and that increases the likelihood of mechanical failures. Hopefully it does not take you too long to get it repaired. Good luck.

Jim

[Cobra #3170]

We are taking it to Kirkham Monday for a proper repair, bulkhead, fuel tank and dry sump tank have to come out as well as trunk liner

[twobjshelbys]

Are you going to get the structures fortified to take the additional stresses or are you going to abandon the traction control? The stresses from the fact that it doesn't slip have to go somewhere.

How much down time?

[Cobra #3170]

Originally Posted by twobjshelbys

Are you going to get the structures fortified to take the additional stresses or are you going to abandon the traction control? The stresses from the fact that it doesn't slip have to go somewhere.

How much down time?

We are going to upgrade the mount structure have to keep improving the cobras speed to stay up with new cars.

[Gaz64]

Originally Posted by twobjshelbys

Are you going to get the structures fortified to take the additional stresses or are you going to abandon the traction control? The stresses from the fact that it doesn't slip have to go somewhere.

How much down time?

Why does that need to happen?

Traction control allows the car to be driven hard to the limit of adhesion, better than a human can, managed with electronics, certainly faster than a human can ever be.

[twobjshelbys]

I can't explain it here on a cell phone but suffice it to say the the laws of physics have not been repealed. The energy lost to friction on a slide has to go somewhere

[Chilibit]

Traction control lets you take advantage of the difference between a slipping coefficient of friction and a non-slipping one.

[Gaz64]

A wheel loses traction, it's wheel speed goes up, and in a split second decision, engine power is reduced with less ignition timing, less fuel injector pulse width, less throttle angle, in a combination of these.

Faster than any human can.

I don't know why we are worried about energy lost to friction on a slide, when it barely happens with traction control enabled, compared to the losses that DO occur without traction control.

[Iluvspeed]

Great news about your traction control. Bad news about your diff mount....(!)

A little off topic... about 20 years ago I did about the same in a CanAm tribute car. I was running Corvette hubs on a scratch-built chassis, and used three of the Hall effect ABS sensors as my inputs--one on each rear stub axle (mid-engined car) and one sensor on the driver-side front suspension (as a "reference" wheel). I converted the Hall digital outputs to analog, and used op amps and comparators to sense wheel slip. I then took that output signal and applied it to my (then state-of-the-art Electromotive TEC 2) knock sensor input. With the TEC software I was able to adjust the ignition timing to soften the output of my engine (a small block Chev, with twin turbos, intercoolers and 850 HP at the wheels. Worked pretty well--cured my wheelspin and got my 0-60 MPH time down to 2.8 seconds..

Glad to hear you are pushing the technology on your Cobra! Great effort.

[olddog]

I have to admit, I'm not seeing how the traction control caused the failure. The traction control is reducing power from the engine to keep the tires from spinning faster than the ground is moving under the car. So less power to the diff. Now I do understand that keeping the tires hooked to the ground allows a higher speed through a turn. So was it side forces from the turn that caused the failure? I could see that. I do not see how reducing engine power increase forces. I do see higher speed in a corner with more traction putting more forces on the suspension. Just trying to understand what you are thinking happened.

[Morris]

Bruce

Since the rear end is bolted solid to the frame in 2 locations.....front below the pinion mount and rear above the stub axles on the rear end........I believe the traction control caused the tires to stick better with greater traction which .....transferred into the chassis via the suspension........In turn caused more of a load on the chassis......which caused the chassis to flex .....which caused one of the ears on the top left chassis where the rear end mounts with a through bolt that is stronger then the rear end top left chassis bracket mount......

That was one of the reasons we made our Torsional plates that attach to the bottom of the chassis rails, to box in the frame rails and stiffen the chassis.

So My point is that replacing the bracket that broke needs better thought process then just replacing the bracket.....

Sorry for the long post.....just another opinion....plus your chassis has a bit of age on it.....

Morris

[Cobra #3170]

Originally Posted by Morris

Bruce

Since the rear end is bolted solid to the frame in 2 locations.....front below the pinion mount and rear above the stub axles on the rear end........I believe the traction control caused the tires to stick better with greater traction which .....transferred into the chassis via the suspension........In turn caused more of a load on the chassis......which caused the chassis to flex .....which caused one of the ears on the top left chassis where the rear end mounts with a through bolt that is stronger then the rear end top left chassis bracket mount......

That was one of the reasons we made our Torsional plates that attach to the bottom of the chassis rails, to box in the frame rails and stiffen the chassis.

So My point is that replacing the bracket that broke needs better thought process then just replacing the bracket.....

Sorry for the long post.....just another opinion....plus your chassis has a bit of age on it.....

Morris

Morris you are correct on all counts. We will upgrade the gauge and design of the brackets. I would like your system better but need to consider originality too. I think we can make it work, the RH bracket held and the left cracked before and we wire welded it (a mistake). I think this will work for a year or so till 3170 retires. Olddog when the car spins the tires it blows them off so completely that the available friction goes down so it does not load the chassis nearly as much as pass after pass with maximum adhesion. Think of it as a burn out where the tires slip but the car barely moves. Same thing happens on a reduced scale so that loads are greatly reduced.

I have a 2018 Ford GT coming in early October so CSX3170 will get more rest time. It started on the production line in Canada this week. I am sure it won't be as wild a ride and won't sound as good but it has killer aerodynamics so should be interesting to track. I don't think you can adjust much but maybe we can add some improvements starting with tires.

I have tried various traction control systems over the years and even built a few. One actually turned lights on in my helmet so I could see that I was losing traction and react. Others were too hard on equipment this system allows you to tune for exactly what you need. Thanks to all the drag racers for developing the system to such a high level.