Autocrossing the Roadster - FFCars.com : Factory Five Racing Discussion Forum

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post #1 of 13 (permalink) Old 05-16-2017, 05:26 PM Thread Starter
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Autocrossing the Roadster

I got the opportunity to attend an autocross held by the local cobra club over the weekend. The event was small, but the course was setup to be pretty open. The result was lots of runs on a course well suited for a cobra.
It was great to really feel out the car and push it to the limit in a safe environment. It is amazing how responsive the car is and how predicable and controllable it is. Really a pleasure to drive. In the video below, the last corner was a sweeper where you could accelerate to the finish. Not the fastest way around, but what fun it is to steer with the gas pedal coming out of the corner.
This particular site had 3 very different surfaces. There was some fresh asphalt, which had great grip, old asphalt which didn't and concrete. What a challenge to manage grip, especially in the corners with multiple surfaces. The first long right hander started with the fresh asphalt, so I tried to stay tight to the inside and get as much turning done on that surface before transitioning to the old asphalt.
The car performed great. The coyote has power everywhere. I loved the 3.73 gears. The rev limiter in 2nd is at 71mph (7200 rpm). I clearly hit it on the first straight, but I think I soft touched it on the 2nd and 3rd straight too. My weak point is braking points and modulation, and this course forced me to do a lot of hard braking.
The only issue was a dragging left rear brake pad. Someone told me they heard it dragging on course, and I heard it squeaking on the way home. It is a repetitive squeak that varies with speed. I am concerned the stock 28 spline axles didn't like the torque of the coyote. Still checking it out, but I suspect I twisted an axle. I knew the axles would be a weak point for future upgrade, but that upgrade may be happening sooner than later. If so, I'll have to consider upgrading to stronger 28 spline axles or switching to 31 spline axles. The traction lock unit is still fresh and strong, so I am thinking about upgraded 28 spline axles.
MACC Autocross Run


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post #2 of 13 (permalink) Old 05-16-2017, 05:31 PM
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Its hard to twist an axle. Check alignment of the rear brake caliper to the rotor. check runout of the rotor/axle flange.


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post #3 of 13 (permalink) Old 05-16-2017, 06:13 PM Thread Starter
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Quote:
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Its hard to twist an axle. Check alignment of the rear brake caliper to the rotor. check runout of the rotor/axle flange.
I plan to check on those items. If it is twisted, it most likely happen a week prior, giving a ride to someone. I made a hard launch on some sticky concrete and it hooked hard. I read the stock ford 28 spline axles are good for 4,600 ft*lb... stock coyote at 390 ft*lb x 3.73 gear x 3.38 1st gear = 4,900 ft*lbs, minus drivetrain losses and rotational inertia. Might be difficult to twist one, but I think my combination could do it. Heck, even ford deemed it necessary to put 31 spline axles in the 05 mustang with 300hp/320 ft*lbs.

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post #4 of 13 (permalink) Old 05-16-2017, 06:18 PM
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Looks like a nice course

If you're on street tires you'll be out of traction looooooong before you can hurt an axle.

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post #5 of 13 (permalink) Old 05-16-2017, 07:05 PM Thread Starter
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The NT-01. Not a drag radial, but it it can actually hook 1st gear if you don't shock load it.

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Looks like a nice course

If you're on street tires you'll be out of traction looooooong before you can hurt an axle.

Jeff

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post #6 of 13 (permalink) Old 05-16-2017, 09:05 PM
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I run NT-01s also. They hook pretty good but will bust loose if the throttle is nailed in 1st or 2nd. I'm confident that they are the driveline fuse, not the axles

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post #7 of 13 (permalink) Old 05-18-2017, 11:16 AM
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A nice course well driven. Another AX convert!!

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post #8 of 13 (permalink) Old 05-18-2017, 05:57 PM
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That Auto-X course is much more suitable for our cars, than most any others I've seen posted on here. Great run, and it looked like a blast.
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post #9 of 13 (permalink) Old 05-18-2017, 06:45 PM
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Brian,
Didn't get a chance to talk to you much on Saturday, but that car is setup great and you drove it very smooth. And your times show it. It was a blast to watch your runs.
Really enjoyed when you hit the rev-limiter on the back straights. Sounds good too!


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post #10 of 13 (permalink) Old 05-18-2017, 07:16 PM Thread Starter
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No kidding! The only other autocross I have done in the roadster so far is this one: http://vid492.photobucket.com/albums...pstyyjxbaj.mp4
The top speed was right about 35mph. In retrospect, I should have done it in 1st gear. If nothing else, it would have brought some drama and excitement to the run. If I was lucky, the sound alone would shake the miata's and mini's apart.

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That Auto-X course is much more suitable for our cars, than most any others I've seen posted on here. Great run, and it looked like a blast.



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post #11 of 13 (permalink) Old 05-19-2017, 01:26 AM
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Yes that is a Cobra AutoX course, great driving. I am not a fan of technical parking lot AutoX. My favorites are within a race track or runway. On June 17th & 18th there is one on the Pocono infield road course.

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post #12 of 13 (permalink) Old 05-19-2017, 10:43 PM
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I agree with Sanford's assessment above regarding brake caliper alignment. Mine tend to do this on the track only, not on the street. I did notice that WITH a passenger, you were hitting the rev limiter sooner on the back straight than without. Guess maybe you were able to go through the first turn faster before the slalom on the straight. Really enjoyed watching your car on the course!

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post #13 of 13 (permalink) Old 05-20-2017, 02:42 AM Thread Starter
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MPTech, Purple Venom, Unfortunately, I can remember cars better than faces, so I remember seeing your cars there, but not necessarily that we met. It's bad at work when I remember what someone drives, but can't remember their name!
Anyway, thanks. I didn't touch the limiter at all in the first heat, but figured something out in the 2nd heat to keep it up there. What a fun course the guys were able to setup.
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