Street, Stock and Two Smoking Twins

[7thgear]

This will be a diary of the adventures of two autocrosses piloting similar cars in different ways through the lens of a go-pro and the binary of a datalogger.




I had recently picked up an Aim Solo DL and started taking it to my local events and slapping them on fellow FRS drivers. Nothing propels your learning curve than seeing what other people doing in essentially identical cars.


My buddy, @automatic , had pushed it further and started putting on a go-pro in identical locations for matched video to go along with the data.




you might have already seem a glimpse of this in my "the launch" thread

http://www.ft86club.com/forums/showthread.php?t=69812


My car is an FRS with a strano fsb and R1Rs (235/40/17) with everything else stock.


His car is a BRZ with Koni Yellows, Stoptech pads and 225/45/17 rivals on slightly lighter/better offset wheels.


we are both in C-Street and have already done 8 events this year.




Autocrossers have generally been traditionally been skeptical of datalogging, most dismiss it as an actual learning tool and relegating it to more of a perk for later video integration.


but I think when you have set objectives and can put it on similar cars, a lot of potential learning points can be pulled for further integration into one's driving style.

[7thgear]

July 20, 2014


our most recent event, taking place at an oval race track.

Our times were 0.2s apart, but boy did we get there taking different paths!!


Track wasn't tricky but featured TWO tight 180 degree hairpins.


the main question was do you drift the pin or do you do a full circle... and while doing a circle is generally the right way to go, the tightness of setup left some room for doubt.


judge for yourself in this split screen replay

[ame="http://youtu.be/NRbjF2sWSqg"]http://youtu.be/NRbjF2sWSqg[/ame]

[7thgear]

to follow up, here are the sectional times for us (I'm Serge)

[7thgear]

this is a datalogger of our entire run, I'm Red and he's Blue

**click on image to expand, it's rather large**

G-Load
Brake
Speed
Steering Input
Throttle

[7thgear]

and finally, the hairpin analysis




here is the shape of our entries





and focused datalogger analysis




hairpin 1







hairpin 2

[7thgear]

what we took away from this is that it was rather inconclusive as to whether drifting or gripping is the way to do such a hairpin, since I was 0.1s faster in the 1st while he was 0.1s faster in the 2nd


the reality would have to come down to the perfect execution




furthermore my FSB has all but eliminated the car's tendency to oversteer while his is still somewhat loose


this can be seen in the initial slalom and maybe a bit in the video


also interesting is past section 17, I would complete the left turns faster while he would complete the right turns faster.. a bit bizzare and would take some thinking to figure out why that is

[wparsons]

What I find really interesting in the video is how similar you guys drive at times, and how differently at others and yet are very close in the end. Combined, you could be unstoppable

[automatic]

I was so convinced during the event that power oversteer was faster that I kept on doing it...but was wondering why no one else was doing it (except a GTI who pulled the handbrake).

Driving the grip line seemed like so much coasting and wasted time so I didnt bother with that.

Looking back at the video/data, it looks like the benefits are negligible but powersliding opens the window to more introduction of driver error.

I believe if someone with good drift skills were to execute a 180 turn around the hairpin, it would be faster than the grip line everytime.

[bimmer635csi]

Originally Posted by 7thgear

what we took away from this is that it was rather inconclusive as to whether drifting or gripping is the way to do such a hairpin, since I was 0.1s faster in the 1st while he was 0.1s faster in the 2nd


the reality would have to come down to the perfect execution

You seem to have answered your own inconclusion (if that is a word)... drift the first so that the tires are heated faster and then grip the second after the tires are hot

[7thgear]

Originally Posted by bimmer635csi

You seem to have answered your own inconclusion (if that is a word)... drift the first so that the tires are heated faster and then grip the second after the tires are hot

yes but the opposite is what happened.. I grip, he drifts

[7thgear]

you often hear the mantra "you should either be on the gas, or on the brake"

Personally...I'd like to think that this is actually impossible.. or at the very least not always practical.

The graph below superimposes throttle , brake and steering on to one axis from my fastest run last weekend.

Places where I'm steering but neither on gas or brake (coast) I've filled in with orange

the bottom red graph is lateral Gs and I've put two black horizontal lines to reference 1.0 G.

you will also find at the top the section numbers, which correspond to the latter map of the course.

As you can see, my actual time spent coasting is very minimal, and is always during the turn-in phase.

Thinking about it I'm not all too sure whether I could have been even more aggressive in those cases, could I have carried a bit more speed and trail braked during the turn in phase.. would have really been better? In all instances I am approaching 1.0G side load, so the car is definitely hauling it...

because there are plenty of instances where you can see me braking during entry. Particularly section 16, where I brake on entry and maintain part throttle to hold almost a steady 1.0G all the way throughout.... only to completely coast during the entry to section 17.

also notice that I am applying throttle the moment I begin to unwind the steering wheel... this is actually kinda cool and I'm sorta proud of that. This tells me that I'm not getting on the gas too soon.. although perhaps I should still delay it just a tiny fraction.




anyway, I'd like to hear some of your thoughts on the coasting vs trail braking and whether one should always aim to be either on the gas or on the brake or if there are times when it would be best to let the car just roll on its own.


[ame="https://www.youtube.com/watch?v=HK1aLV0TK3Q"]2014 Autocross Regionals Event #6 : Barrie - YouTube[/ame]




click to expand