Technical Analysis for September 17, 2017 event at YYC

[Sprockett]

He also points out that, although he shed about 20 kph for the kink, he gained all this speed back accelerating between the kink and the right-hand turn before having to brake again. While true, I think that with less than half the power, it would have been a lot harder for me to claw back any speed I shed going into the kink. I think it's reasonable to approach the kink slightly differently depending on the type of car being driven.

I actually didn't point that out...or at least not like that as I didn't look at the data until this evening...and also don't think that is particularly relevant that I made the speed back. That said, I do believe a Miata would have made the speed back too, see below.

In the end, I do not accept that the correct line changes drastically from car to car. When I say line really I mean strategy...maybe you won't end up on the exact some line car to car but the what you are trying to do doesn't change. Even with little power you need to maximize the time on the throttle. Even with lots of power you can't drive triangles everywhere. I chose my line because it was the shortest distance from the end of the slalom to the finish lights. I would have attempted to do the exact same thing in a Miata. Lets not just look at power when deciding what to do in a Miata or 'low powered' car....because there is no such thing as a low powered and big and heavy and competitive autocross car. In an NB Miata that is some 1,000 pounds(!) lighter than my M2 I would not have had to slow nearly as much to make the left turn out of the slalom while being on the same line. Therefore would have had less to 'make up' on throttle. I would still have been on the shortest path to the finish and spent less time in the slow 180 degree turn.

It's possible I'm completely off the mark but I haven't heard a thing so far to change my mind.

[Reijo]

Here's Stephen's 1st post for this topic that is missing.   I don't see a way to post it where I want it unfortunately ... but at least it is here (I'll leave the other one separate for now just in case):

Had an interesting debate about line choice with Ryan after the event, and figured it could be an interesting topic for everyone else as well.

The last twenty seconds of the course consisted of a fairly quick slalom, followed by a left-hand link, followed by a fairly tight constant-radius right-hand turn, with the timing lights at the exit of that turn. In Julie's Miata, the slalom was fast enough that I was kissing the limiter at the end.

Here's my in-car video: https://www.youtube.com/watch?v=L53EnYaLFuU?t=34. Skip to the 34 second mark if the link doesn't automatically.

Here's a map of the section: https://i.imgur.com/7bpcbd3.jpg.

My approach was to lift right before the kink, shed the absolute minimum amount of speed required to make it through, then let the car drift all the way track right. This meant I wasn't able to set up for the right-hander at all, but since there was no straightaway afterward, I figured a big brake and keeping it super tight through the corner was the right approach anyway. This is Option B above.

Ryan braked before the kink so that he could set up more for the right-hander. After a squirt of gas between the kink and the turn, he entered the right-hander much wider than I did, allowing him to carve a larger radius through the turn and carry more speed. This is Option A above.

I'm curious -- how did you all approach these elements? Did any of you try both approaches? If so, what did you think?

Ryan crushed me at this event, so if in doubt, he's probably right.

Edit: Updated the course map and the descriptions of Ryan's line.

[Sprockett]

When I see Ryan at the top of the PAX scales in an ES Miata I'll retract my previous comments and agree with Stephen that the Miata is the car to have, until then Im not convinced.

While you may never see me at the top of any PAX standings so may be safe there... I'll point out for those with short memories that our current Index king did just fine in an ES car with two dead cylinders in 2014.

To add insult to injury he was also tops in RAW 

[Reijo]

He also points out that, although he shed about 20 kph for the kink, he gained all this speed back accelerating between the kink and the right-hand turn before having to brake again. While true, I think that with less than half the power, it would have been a lot harder for me to claw back any speed I shed going into the kink. I think it's reasonable to approach the kink slightly differently depending on the type of car being driven.

I actually didn't point that out...or at least not like that as I didn't look at the data until this evening...and also don't think that is particularly relevant that I made the speed back. That said, I do believe a Miata would have made the speed back too, see below.

In the end, I do not accept that the correct line changes drastically from car to car. When I say line really I mean strategy...maybe you won't end up on the exact some line car to car but the what you are trying to do doesn't change. Even with little power you need to maximize the time on the throttle. Even with lots of power you can't drive triangles everywhere. I chose my line because it was the shortest distance from the end of the slalom to the finish lights. I would have attempted to do the exact same thing in a Miata. Lets not just look at power when deciding what to do in a Miata or 'low powered' car....because there is no such thing as a low powered and big and heavy and competitive autocross car. In an NB Miata that is some 1,000 pounds(!) lighter than my M2 I would not have had to slow nearly as much to make the left turn out of the slalom while being on the same line. Therefore would have had less to 'make up' on throttle. I would still have been on the shortest path to the finish and spent less time in the slow 180 degree turn.

It's possible I'm completely off the mark but I haven't heard a thing so far to change my mind.

After I walked the course in the morning the first time I had it memorized.  I thought what an easy course to memorize ... and drive?  hehe ... I guess I was wrong.   

Of course, I helped setup the course on the evening before but that is never the same as walking the course with the purpose of analysing what you need to do.

Interestingly enough, by coincidence more than anything, I drove two very different cars (BMod thingie with aero, and a 2005 M3 STU car).  Unfortunately we got disqualified on sound in the BMod (but that is another story ... it seems the wind shifted and despite our efforts to reduce sound, sound got worse ... but that is another topic).

In the end, Clara kindly offered her M3 to drive in the afternoon which you could say was more of a momentum car - not overly powerful, much wider and no aero.

1.  The B-Mod car - was surprisingly powerful (670cc Rotax/CVT trans - hence BMod ... and not FM (max. 500 cc) ... never mind the aero) and, of course, very narrow and short.

For the first run I was plagued by being tossed around in the seat side-to-side resulting in jerkiness in steering compounded by massive understeer which meant I picked up a number of cones.  Warned on sound (think it was 92.9 db). 

2nd run - tighten the seat belts = more control but still tossed about in the cabin and picked up more cones but the time picked up a few seconds.  Massive understeer:  I tried everything I could to get some traction/weight on the front wheels but there is only so much you can do.  The second slalom was flat out in that thing!  Keep steering!  lol ... fun stuff.  At the end of the slalom, interestingly enough, the car turned in!  I think the front wing at speed was starting to work so I could actually steer the car.  A light lift, turn-in as per Ryan's method (shortest distance more or less) seemed to work really well and I thought was the ideal line.  Even with the speed, I could basically choose whatever line I wanted - such was the turn-in.  Over on sound despite the mods (93.0 db).  Or is that right on?  Another discussion for the future. 

3rd (and final) run:  One more mod to sound and now I used my fleece jacket between the body work/frame and myself to hold myself in position.  The run was much better however this time we blew over 94 db despite our "improvement"!  After the run I got out of the car (I had sat in the car the entire 3 runs due to difficulty of getting in and out) and noticed that the wind had shifted toward the sound across the track.  Anyway, we called it quits there.  Incidentally on that last run I also changed my line into the final corner to aid the sound so I went wider to be further from the sound and more like the line Stephen mentioned.  My time was about a second faster (and 1st clean run) however that was more due to learning the car, controlling the massive understeer as best I could (slow in the corners ..  ugh!), and actually being held in place better by the belts and fleece padding!  But that last run did not seem like the ideal line after the 2nd slalom since I had to slow down more to make that last corner ... and longer distance.  The last corner felt slow in comparison to the first two runs.

2.  M3/afternoon:  Obviously this is a much heavier car but a good, balanced car but not with the greatest tires (Continentals - current DW equivalent) and stock alignment.  I had to slow down for all the 2nd slalom cones and for the left kink at the end of the slalom because I would've shot past the next pointer otherwise (a certain difference in momentum, eh?).  Nevertheless, a quick stab on the brake and the car would rotate into the kink however with the greater mass and the tires, it did not want to turn as much as I would have liked so I went with the flow and probably drove a line in between what Stephen and Ryan were talking about.  I think with some alignment work and better tires, I could have got the car further to the left or obviously more brake.  Basically I compromised and went with the flow and it ended up being a hybrid run shall we say (no pun intended  ).  Hmmm....so interestingly I found a slightly "different" line seemed to work for this car.

I agree with Ryan's comments in that (don't remember who said this originally) that all cars are momentum cars - e.g. you drive the same line.  In fact, that is one of my "secrets" of why I can drive so fast in almost any car!  I drive the same line.  Go figure, eh?     Even in a so-called HP car, it takes much longer to accelerate back to speed than it takes to lose the speed (look at distances/time/G's for braking and acceleration ... braking is superior). Momentum is the way to drive fast in any car - QED.

And, in the words of Joe Cheng (of Vancouver and A-Mod fame from the '90's some time), if in doubt (about line), choose the shortest distance (in autox).  That way, you may or may not have the ideal line but you will certainly not lose much to the "ideal" line ... maybe a tenth or two.  BTW, in my opinion, it is also one of the reasons road racers don't often make good autoxers because of the different lines.

As a final note, I found Murray's comment interesting and telling in that he did not find much difference no matter which line he used (his runs were within tenths of each other).  So, in the end, I have a suspicion that there was not a whole lot of difference in the time based on line (within reason - not including extreme) in that last section as long as you drove it well which is interesting!  I think this would have been a good time for data analysis to really figure it out.  And, as I found out, i.t could be a little bit dependent on the car.

As for that B-Mod, I figure it could have gone a couple of seconds faster with more wing in the front (e.g. fill in the wing missing in the center of the car - more than doubling the front wing area) which would have given the front end some bite in the corners and hence more speed in the bigger but slower corners.  I suspect it needs more work on alignment as well as spring rates (I was picking up the inside front wheel coming out of corners which was kinda fun but indicative of not enough spring rate in the back due to compression).  It is a work in progress.  Look for it to go faster.  As for sound he can't do more with pipes but he could put up more body work to "hide" the engine and Dave said he was going to put a turbo on it to silence it some more!  LOL    Thanks Dave!  That was a fun ride! 

[Reijo]

I'll just add a bit of a disclaimer here:  I'm not entirely sure I am correct either!

Some data analysis would've been the best way to figure this one out ...

And a final note, reflecting upon this a bit, I think I was adjusting to the M3 more and more each run, incrementally cleaning up the runs/corners/slaloms/inputs etc. and I found I was carrying more and more speed in the 2nd slalom and as the speed picked up I was tending to drift slightly more and more to the right closer to Stephen's line.  A couple of times I had to dodge the next cone around the kink ... so pretty far out.  However there did not seem to be as much difference in the final corner speed compared to the B-Mod.  Curious.

[MurrayPeterson]

I have a simulator where I can set up autox courses of my choice and run them with cars of my choice.  If I have enough time (probably this winter), I will set up something like that sequence and go at it repeatedly.  Or if anyone else wants to have a go, let me know and we can make an evening of the exercise.

[Reijo]

I have a simulator where I can set up autox courses of my choice and run them with cars of my choice.  If I have enough time (probably this winter), I will set up something like that sequence and go at it repeatedly.  Or if anyone else wants to have a go, let me know and we can make an evening of the exercise.

Ooooooo.......now that could be fun!   hahahaha

Count me in!

R

[Terry Johns]

Ryan says

because there is no such thing as a low powered and big and heavy and competitive autocross car. In an NB Miata that is some 1,000 pounds lighter than my M2 I would not have had to slow nearly as much to make the left turn out of the slalom while being on the same line.


That's because the Miata wouldn't have been going as fast.

I wholeheartedly agree with Stephen to win in PAX at YYC a 300 HP car is a real advantage, that must mean that a big HP car has an advantage, and by definition the lowered powered car is disadvantaged. Just take a look at the time difference between the fastest RAW big power Corvette and the low powered CS Miata of Murray, who is one of our very best drivers, 3.992 slower, than the Corvette. I buy 3 tenths, or even 8 tenths difference, but Murray nearly 4 seconds slower, no sorry dont buy it.

My argument all along is that PAX isn't accurate and is dependant on course design.

I am more than happy to let any of our quickest drivers in high powered car, Cam, Ryan, Tom, Stephen borrow my car and see if they can beat or equal their own time in a low powered car.

Who'd like to take the challenge???

[MurrayPeterson]

That's because the Miata wouldn't  have been going as fast.

I have to disagree with you here Terry.  The Miata may be acceleration limited, but those increasing offsets in the slalom would allow a lighter car to go much faster.  The Miata should be the one needing extra braking.

[E6Cueman]

I imagined that I was doing something like C, taking an obviously shorter line with a faster exit from the slalom.  Slowing down to get left was not a consideration...

It feels like this was the wrong choice -  something I chalk up to my inability to see the exact lay of the land during my walk.  I think if I grew a few more inches, I could really get that birds eye view that I'm looking for.

I may also be horrifically impatient on course, and often overdrive the car, carrying too much speed into elements and thinking it's OK because the car still fits between the lines.

[MurrayPeterson]

Looking at Stephen's video as well as the Reijo's photos, it appears that there are/were three approaches to the corner:

1. Keep the most speed possible past the last slalom cone
This appeared to be Stephen's line, and I feel that it adds distance without gaining any speed into the finish.  He ends up close to the first cone on the final curve (see 37 second mark in his video).

2. Go for shortest distance (point to point)
Aim for the leftmost cone of the final curve that is visible after the slalom exit.  In  other words, go in a straight line from the slalom exit to a point tangent to the final curve, and then follow the curve around into the finish.  From Stephen's video, this means that the second cone of the curve is where the car comes closest.
This is how I drove this element most often.  And what Quentin shows.

3. Backside the final turn
More distance here, but allows a longer acceleration zone into the finish line.  Keep left longer, and then turn in so that you do not comes close to either the first or second cones of the final curve, but the 3rd and last cone is where you come closest.

Ryan -- was #3 your line choice?  The photo evidence suggests that this is the case.

[MurrayPeterson]

Quentin -- I love your diagram, but I think things are a bit misleading.  The actual finish is very close to the point where the curve finishes, not way out right.  Which means the acceleration zone is very small after coming around the corner.  Which makes it not so obvious that your line was wrong.

[Terry Johns]

That's because the Miata wouldn't  have been going as fast.

I have to disagree with you here Terry.  The Miata may be acceleration limited, but those increasing offsets in the slalom would allow a lighter car to go much faster.  The Miata should be the one needing extra braking.

You cant be serious, if the lighter car is going much faster, how do you explain your nearly 4 seconds slower than fastest RAW.

[MurrayPeterson]

That's because the Miata wouldn't  have been going as fast.

I have to disagree with you here Terry.  The Miata may be acceleration limited, but those increasing offsets in the slalom would allow a lighter car to go much faster.  The Miata should be the one needing extra braking.

You cant be serious, if the lighter car is going much faster, how do you explain your nearly 4 seconds slower than fastest RAW.

I didn't say faster for the entire course, just at that particular point.  Ryan's car will get up to maximum speed in that slalom long before me.  However, due to his car's weight and width, that maximum speed will be slower than the Miata's.

[Terry Johns]

That's because the Miata wouldn't  have been going as fast.

I have to disagree with you here Terry.  The Miata may be acceleration limited, but those increasing offsets in the slalom would allow a lighter car to go much faster.  The Miata should be the one needing extra braking.

You cant be serious, if the lighter car is going much faster, how do you explain your nearly 4 seconds slower than fastest RAW.

I didn't say faster for the entire course, just at that particular point.  Ryan's car will get up to maximum speed in that slalom long before me.  However, due to his car's weight and width, that maximum speed will be slower than the Miata's.

As long as your convinced I guess that's all that matters.

Standing half way along the 1st slalom which where I marshalled Ryan and Cam where noticeably quicker than anyone else by a country mile.