Endurocross Aug 19

[Loren]

I'm the only one to get slower wow sucks to be me

Blame the car.

[Loren]

Eva, when I do something weird with a course, like add unusual options, I like to know how they worked.

Oh, and taking smooth S turns rather than Z turns is absolutely the fast way around those sweeping turns. Recognizing things like that is one of the reasons you're becoming a faster driver!

I think it's very possible that for SOME cars, the outside line on the far turnaround would have been faster. Why? Because "the most important turn on any course is the one before the longest straight". Now, we didn't really have any significant "straights" on this course, but if you had enough grip to get through the slalom without lifting (pretty much everybody but me), that slalom could almost be considered a straight, as you could accelerate through a good portion of it. So, EXIT SPEED of the turn-around = higher speed in that slalom. (or at the very least, hitting terminal velocity EARLIER in the slalom) And that could potentially be worth more than the little bit you'd give up by taking a slightly longer line through the turn-around.

Now, I'm gonna geek out and throw math at it... just to satisfy my curiosity.

The inside line gives an effective "skidpad" diameter of about 106 feet. The outside line about 125 feet.

Inside line distance = 166.5'
Outside line distance = 196.3'

Disregarding that the outside line will carry more speed, reducing the time factor a little bit... if a driver took each line at exactly 30 mph, the time to get around the turn-around would be:

Inside = 0.063068182 seconds
Outside = 0.074356061 seconds

So, the turn-around by itself would have been less than .011 seconds faster to take the inside loop. In any car that couldn't reach grip-limited terminal-velocity in the slalom, there was probably more than that to gain by having higher exit speed on the turn-around.

I could do more complicated math to try to determine that... like figuring out what each car's speed through the turn-around speed would have been at 1G to come up with the exit speeds... and figuring different acceleration rates over... say 500 feet (the distance from the exit apex to about the middle of the slalom).

I'll leave that as an exercise for those who are more geeky than me. Suffice it to say that the potential time lost in the turn-around was minimal. The real difference was whether or not taking the wider entry gave you a benefit that you could leverage on the exit.

If all you "fast car" guys would spend some time in a "slow car", you'd understand all this "momentum" stuff!

[garage west]

http://youtu.be/1vrLPZbcuSM

Tried to hold second on the way out first lap-- bouncing off the rev limiter.

[impalanut]

In the few runs I made I took the inside line on the turnaround. If I hit the correct line and brake point, I could mat the gas at the last cone in the turn itself. If I hit it wrong, I pushed out to the grass and couldnt really get on the gas until the double gate. My number three connecting rod looks like a pretzel. will post a pic when I get a chance. Haven't opened the motor yet.
After getting home, I went to start my cadillac to go to my brothers and the clutch and/or tranny is shot. Went to get a motor for the Legrand. It was in Lakeland. Just as I arrived the radio and gauges quit and it appears the alternator is shot. Fortunately, it was just the cable from the alternator to the battery, and the guys at the salvage yard, being the motorheads that they are, helped to fix it enough to get me home rather than wait for triple a to come and get me.
Don't let me near any of your cars.

[WAFlowers]

Something wrong with your math Loren. At 30mph you are travelling exactly 44 feet person second.

That makes the inside line 3.784 seconds. Geez, how fast would you have to go to do it in a few hundredths of a second?

I think you divided by 60 one too many times. (Edit: therefore times you posted were for 1800mph!)

Oh, and the outside line time would be 4.461 seconds.

[Loren]

Well, at least I know somebody was paying attention (more than me, apparently!).

What I did was multiply by 60 to get from "hours" to "minutes". So, my numbers were minutes, no seconds. Multiply by 60 again to get seconds:

Inside = 3.784090909
Outside = 4.461363636

Difference 0.67 seconds. More significant, of course. Really means that the increased speed of the outside line needs to be factored in... probably would reduce the time difference by about half.

And it means that the answer as to which way is better is even LESS clear! Lose a couple tenths on the turn around, gain a couple tenths in the slalom... it's really going to be a personal preference/driving style/car setup thing... but pretty much a wash!

Being lazy and hating complicated formulae, I plugged some numbers into a skidpad spreadsheet that I have...

Assuming a cornering rate of .95G, it would take 4.13 seconds to drive the inside loop.

At the same .95G, it would take 4.49 seconds to drive the outside loop.

So, the actual difference between inside and outside (assuming a driver could drive either line at a constant .95G): 0.36 seconds.

And the exit speeds:
40.3 fps = 27.5 mph
43.7 fps = 29.8 mph

Isn't math fun?

[Loren]

http://youtu.be/1vrLPZbcuSM

Tried to hold second on the way out first lap-- bouncing off the rev limiter.

Dayum, John...

Those last two laps were smokin'! Where'd you learn to drive like that?

[Spin Out]

Had a gret time at this one. I love big sweepers, so I loved this course . My second run was in the very wet. This actually worked out great for me. It was my first autocross in this car, so I got 5 laps in the dry and 5 laps through puddles. Pretty much ideal to feel out the car all in one day. I can only hope the workers enjoyed my back to back spins.

Very smooth event. I'm going to steal several ideas for PCA events. Oh, and my thanks to Mary for being an excellent pit crew.

[snookwheel]

We did enjoy your spins! Especially the second one, a perfect 360 ending with you lined up perfectly for entry into the turnaround!

Scott

[Loren]

Mark: For the record, the Endurocross idea was stolen by me in 1997 or so from the Cal Poly Sports Car Club website. They billed it as pure mayhem, "Brakes will fade! Radiators will boil!" And the way they did it, it probably was. They did runs on the order of 20 minutes! But, they had a membership of like 5 people, so they could get away with it.

I've put on an Enduro every couple years since then, usually with 4-6 minute runs on a fairly easy course. (no forced 1st gear downshifts, not too hard to follow, etc)

[Cpt_Rum-bo]

Seems like I missed a great event

Suffering from extreme withdrawal right now

[buddy bodean]

What, no pictures yet? Looking forward to seeing your work again Greg!

[twistedwankel]

If all you "fast car" guys would spend some time in a "slow car", you'd understand all this "momentum" stuff!

I totally agree with this statement. By alternately driving the flexible flyer stone age Mustang torque hammer I definately can better utilize the torqueless Scalpel Rx8 and can get more carving speed out of it. And vise versa.

[garage west]

Just as I was thinking to myself, "SpinOut has got some pretty tasty drifts going on through the sweepers," he spun out. Twice.

[Loren]

Dammit. I think I flat-spotted my RF tire. Not bad, just enough that I can sort of feel it through the floorboard at about 35 mph. I guess if I take the tire pressures and shock settings out of competition mode, it will probably be okay...

[snookwheel]

i just couldnt get the Track Addict overlay vid. to load. Here's the last two laps from our GoPro.

http://www.youtube.com/watch?v=bNFAOpGQYx0

Just repeating mself and others, but that was a great event, Loren!

[Loren]

Scott... was that... smoothness? You almost looked relaxed.

[snookwheel]

Thanks, Loren! I have been trying to pay attention to your 'suck less' training... Maybe it's starting to sink in a little.

I can see some time I left out there, and I had better start finding it or Mary's going to be schooling me

Scott

[Greg]

I was only able to get a hand full of pictures, sorry




















Ed took these two




Big sizes
http://www.flickr.com/photos/eunos89/se ... 187444680/

[Native]

Quality trumps quantity! Nice work...and I must compliment your subject - and that's one mofo of a spider!