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Old 02-01-2011, 10:03 PM   #1
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Default Valentine's day present for my wife (AKA friction circle)

I spent a lot of money making this Valentine for my wife. I hope she likes it.



I was playing around with plotting friction circle data for some telemetry I logged at TWS last year. I believe this is the session where my brakes were toast but it is still interesting to look at.
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Old 02-01-2011, 10:20 PM   #2
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You know she's a keeper when she both appreciates and understands it
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Old 02-01-2011, 10:24 PM   #3
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This is one of those rare intersections of nerdy and cute that doesn't make me throw up in my mouth. Awwww.
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Old 02-01-2011, 10:42 PM   #4
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I could come up with all sorts of G spot jokes, but I must refrain..
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Old 02-02-2011, 01:08 AM   #5
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And here I thought "friction circle" was going to be a euphemism for something.
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Old 02-02-2011, 12:56 PM   #6
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Quote:
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And here I thought "friction circle" was going to be a euphemism for something.
this
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Old 02-02-2011, 01:34 PM   #7
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I thought the fact it came out as a heart shape was funny. Changing the dot color to red makes it even funnier. The line pattern through the center is, I believe, from the fast straights at this particular track (TWS).

But, now for the real reasons I included this in the race prep section. This shows my track Miata is achieving ~1.2g lateral accelerations on NT-01s. It also shows that there is a lot more speed to be had with this car, at least at the track where I logged the data. With some more manly driving there are some corners where I can 'spread the dots' farther out to the edges of the theoretically achievable friction circle.

Here is a quick read on friction circle analysis. I would like to see some others friction circle data if you have it. If you know how to use Excel then creating this plot is pretty easy. Just do an X-Y scatter plot on your lat and long acceleration log data from a couple of hot laps.
http://www.trackpedia.com/wiki/Data_...riction_Circle
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Old 02-03-2011, 11:08 AM   #8
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Top left is really loaded up with dots because of the banking right? I assume the banked turns are left handers which means you weren't trail braking much on right handers (not many dots on the bottom right)?

This makes me want to look at some of my friction circles more...
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Old 02-03-2011, 11:23 AM   #9
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Here's one from me at Mid-Ohio in an SSB Civic Si. BFG R1 tires, lap times were within 1s of the lap record.
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Old 02-03-2011, 12:00 PM   #10
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Within 1 second of lap record in a car that doesn't accelerate is pretty impressive.
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Old 02-03-2011, 12:34 PM   #11
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When I read "friction circle" in the title, I thought you meant you were installing a skidpad for Valentine's Day.
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Old 02-03-2011, 12:56 PM   #12
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Quote:
Originally Posted by Efini~FC3S View Post
Here's one from me at Mid-Ohio in an SSB Civic Si. BFG R1 tires, lap times were within 1s of the lap record.
Very nice, good driving. You can really see the outline of the edges of the friction circle, and the graph is really 'hollow'.

I think the bunch of dots that are skewed to the left (lateral) is due to the mostly right turn nature of the track running CW. The turn 2-1 combo is a really long turn and I was definitely not carrying as much speed through there as I could have. The clumping inside of the circle reflects the lower than optimum acceleration through those corners. There is something about exiting onto the front straight, over a sharp bump from the banking transition, with a concrete wall in your face, going ~100 mph, that is a little unnerving.

I need to go back and look at my data to see where those low lateral g-spots are located so I can push harder on those next time out.

There, the g-spot pun, I used it
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Old 02-03-2011, 12:59 PM   #13
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Double post
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Old 02-03-2011, 02:01 PM   #14
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Quote:
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Within 1 second of lap record in a car that doesn't accelerate is pretty impressive.
Well, the track record is held by the exact car I was driving (different driver, different day) so I would hope to be close to it.

And yes, SSB (Showroom Stock) cars don't accelerate quite like a turbo miata. Better than SSC cars though...
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Old 02-03-2011, 02:22 PM   #15
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Quote:
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I was playing around with plotting friction circle data for some telemetry I logged at TWS last year. I believe this is the session where my brakes were toast but it is still interesting to look at.
That is an admirable amount of longitudinal acceleration. Almost 1/2 a G? Wow. Was that with the turbo or LS1 car? Only time I get over 0.15 g's is when I'm pulling out of the pits in 1st gear, and even then I'm lucky to see 0.20!.
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Old 02-03-2011, 02:31 PM   #16
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I can do the exact same thing with my Professional Datalogging Set. It's easy to set up, too -- you simply install your g-meter (length of floss tied to rear-view mirror, with an Sharpie marker tied to the other end), then uncap the Sharpie (or, more precisely, your g-force recording device) and hold a sheet of paper underneath the Sharpie as you drive.

The resulting datalog looks a little different though:

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Old 02-03-2011, 02:42 PM   #17
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Quote:
Originally Posted by wildo View Post
That is an admirable amount of longitudinal acceleration. Almost 1/2 a G? Wow. Was that with the turbo or LS1 car? Only time I get over 0.15 g's is when I'm pulling out of the pits in 1st gear, and even then I'm lucky to see 0.20!.
That was the LS1 car. 320 RWHP, 350 ft*lbs. It is an instant throttle response torque monster compared to a turbo car of similar power level so it accelerates well out of the corners.
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Old 02-03-2011, 02:56 PM   #18
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Quote:
Originally Posted by ZX-Tex View Post
That was the LS1 car. 320 RWHP, 350 ft*lbs. It is an instant throttle response torque monster compared to a turbo car of similar power level so it accelerates well out of the corners.
Understatement of the year!
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Old 02-05-2011, 09:19 PM   #19
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Your G-G shows little trail braking is occurring for whatever reason. Most Miatas aren't so hot at it. Trail braking is when you brake for a turn and then ease off the brake at the same time as you increase cornering load. This speeds you up since the car is spending more time at the limit of traction available from the tires.

Below is a G-G showing lots of trail braking into RN turns. The way that car is setup, it is easy to use the tires to the limit without premature brake lockup curtailing the fun.

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Old 02-05-2011, 11:13 PM   #20
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Part of the trick with trail braking with this car is the torque load from back driving the LS1. With the brake balance set just right (in cockpit adjuster) if I let the clutch out under braking, especially trail braking, the extra back torque brakes the rear tires loose and the car wants to spin. So I need to work on my clutch releasing, maybe holding it disengaged until right after I get off the brakes and right before I get back on the throttle.

Life would be a lot easier if it had a slipper clutch like the bikes I used to race. Slipper clutches are really, really nice, especially in heavy braking corners.
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