TRev's BRZ RTR Autocross Build

[Ninjin]

Is the rear subframe re-alignable to correct left-to-right camber variation without aftermarket (i.e. Non-stock-legal) parts?

[TRev]

Originally Posted by Kido1986

Holy-rear-camber-variation! I thought mine was bad at -.8 and -1.1!

Yeah, it was so far off that the first alignment shop thought his equipment was off. I got the Nascar alignment going on haha.

Originally Posted by Ninjin

Is the rear subframe re-alignable to correct left-to-right camber variation without aftermarket (i.e. Non-stock-legal) parts?

Not that I am aware of. I heard mention of loosening and shifting the rear sub frame but not sure how that could help based on the suspension geometry.

[TRev]

Had drying conditions in first heat at the Peru Match Tour today. Very windy so course conditions were drying fairly quickly. Big change between run 1 and 2 and then continued to get better so fourth run is the one that counted.

I didn't get the rebound dialed in quite the way I wanted. The additional toe in in the rear definitely has allowed for more power on corner exit but now I am experiencing some push on corner exit only. Going to try to dial it out with rebound and if needed will back off the toe in a bit in the rear. My fastest last run had the rebound even front and rear at 1 3/8 from full soft versus a more front heavy bias prior to the recent alignment changes.

Mark Andy put some pressure on me with his third run and was .135 seconds ahead (PAX). I cleaned up my line and dropped .64 seconds for the win by .386 (PAX) on our fourth and final runs. Congratulations to Bill (Scooby South) for taking 2nd in STX!

Having problems with my new Samsung S4 and the external GoPro control so I don't have the outside overlay shot. My lateral G was about .1 off of Lincoln. I didn't get a chance to calibrate the G sensor but think most of it was the dampness in the concrete and cool temps.

Here is the windshield mount view of my best run with data.
[ame]http://youtu.be/7xIpbZs6Vp8[/ame]

[Kido1986]

Damn it, Im jealous of all of these big tours you guys get to run. Everything is so far for me.

Nice driving but I can see/hear the understeer you're talking about.

[TRev]

Made the LCQ today and then missed advancing to the second round by .2 seconds.

[ame]http://youtu.be/sbVyI1XfrKg[/ame]

[rx3]

Thank you for sharing all this information.

Originally Posted by TRev

Corner entry over steer: Soften rear rebound
Corner entry under steer: Stiffen rear rebound
Corner exit over steer: Stiffen front rebound
Corner exit under steer: Soften front rebound

Have you noticed a significant change over the stock shocks and more importantly: Does the adjustment of the Koni shocks easily influence over or under steer behavior or is it negligible compared to the sway bar settings?

Originally Posted by SVThis

2) Turn earlier...and less. To go faster, the arc you are running must be bigger. A bigger arc requires less steering. To make a bigger arc that is centered in the same place, the arc must start sooner (turn earlier).

Doesn't this contradict the 'late apex rule' or am I misunderstanding something?

[TRev]

Originally Posted by rx3

Thank you for sharing all this information.

Have you noticed a significant change over the stock shocks and more importantly: Does the adjustment of the Koni shocks easily influence over or under steer behavior or is it negligible compared to the sway bar settings?


Doesn't this contradict the 'late apex rule' or am I misunderstanding something?

I wouldn't say it is a significant advantage with regard to times over stock though the ability to adjust rebound definitely has a significant influence on under steer/over steer if desired. The sway bar will affect corner entry/exit but not to a similar effect that rebound does and vice versa with regard to mid corner over steer/under steer and the front sway bar.

To me the comment is more slated towards smooth inputs (not upsetting the car) and maintaining speed which is especially important with the Twins due to available power. Definitely still want to almost always backside cones and not get late though.

[rx3]

Originally Posted by TRev

I wouldn't say it is a significant advantage with regard to times over stock though the ability to adjust rebound definitely has a significant influence on under steer/over steer if desired.

But this is very useful. In a course with sweepers you can for instance make it more prone to oversteer by adjusting the rebound (stiff rear and loose front)?

Originally Posted by TRev

Definitely still want to almost always backside cones and not get late though.

Yes this is what you do when you late apex a corner. And this what one also does in a skiing or even a soapbox race. Maybe by turning early he meant, for instance, that one turns left early before a cone on your right and turning right, so you will approach the backside of the cone.

(One would only early apex a corner after a long straight which is ending in a long slow section, which is rarely the case.)

[xwd]

Originally Posted by rx3

But this is very useful. In a course with sweepers you can for instance make it more prone to oversteer by adjusting the rebound (stiff rear and loose front)?


Yes this is what you do when you late apex a corner. And this what one also does in a skiing or even a soapbox race. Maybe by turning early he meant, for instance, that one turns left early before a cone on your right and turning right, so you will approach the backside of the cone.

(One would only early apex a corner after a long straight which is ending in a long slow section, which is rarely the case.)

The point is just being early on a turn instead of late, doesn't really have anything to do with late apexing or early apexing. Chances are if you are early you have a better chance of late apexing, like your slalom example.

On a road course you know where your turn-in points are generally and you have a lot of time to setup so you usually aren't "late" but in autocross things come up so fast most people are late to turn. Then too much steering angle scrubs off speed, puts you in poor position for the next element, etc. Easy in theory, not so easy in practice.

[TRev]

Originally Posted by rx3

But this is very useful. In a course with sweepers you can for instance make it more prone to oversteer by adjusting the rebound (stiff rear and loose front)?

Yes, though rebound has much less effect mid-corner. For example on a long sweeper the car is already set for most of the sweeper and the sway bar is what you would want to adjust.

[rx3]

Originally Posted by dwx

The point is just being early on a turn instead of late, doesn't really have anything to do with late apexing or early apexing. Chances are if you are early you have a better chance of late apexing, like your slalom example.

Well, I just think the words are confusing or not ideally chosen: Since when you turn early you also do a an early apex as seen on the blue line here (and which is what you are not supposed to do):

However, in order to get to do the turqoise line you typically need to turn left early in order to do a late apex on the following turn.

Originally Posted by dwx

Then too much steering angle scrubs off speed, puts you in poor position for the next element, etc. Easy in theory, not so easy in practice.

This is the much better explanation. And this is for instance even more important in a skiing race, since there you are even missing an engine (should you ever scrub off speed in a turn).
Maybe a clearer explanation would be: The tightest turning radius must happen early and not late in a turn.
Sorry, for filling up this thread with this 'early turning thing'.

Originally Posted by TRev

Yes, though rebound has much less effect mid-corner. For example on a long sweeper the car is already set for most of the sweeper and the sway bar is what you would want to adjust.

Ok, this makes sense. At least, a stiff rear (thanks to the stiff shocks) may get your rear around a bit on sweeper entry, so you need at least less turning during mid corner.

[qoncept]

TRev, I'm on the fence about Solo Storm. On the one hand $200 isn't a lot but on the other it IS a lot for what might essentially end up being just a cool toy. Can you tell me a bit about using it? Specifically, I'm wondering:

1) What do you get if you don't use an external GPS?
2) Can you use it quickly enough to get a useful analysis between runs, or is this just an after-the-fact thing?
3) If you look at your runs at the end of the day, is there something you can learn for next week?
4) How do you start recording? Does it remotely control your GoPro or do you have to start both of them manually? My GoPro battery life is already incredibly bad and it takes constant babysitting to get all of my runs recorded.

[xwd]

1) You really need an external GPS. The built-in ones do not sample at a high enough rate to be that useful. There is data gained from using the built-in accelerometers as well but really only for figuring out where turns are by the software.

2) You can easily use it quickly enough between runs.

3) At the end of the day you have more time to analyze the runs obviously. I do not use it with a device which can also record (Nexus 7) so afterwards I sync the video to the data and can get more out of it that way.

4) It will remotely control the GoPro. You can set a "staging marker" on the course or let it figure it out and it will start the camera at that point. It will stop the camera when you reach the trigger to stop logging the run (like 10mph for more than 2 seconds). It's been a little hit and miss for me. It requires you leave WiFi turned on which kills the GoPro battery even more, so I usually have a spare battery in the car. There is a function to download the video off the GoPro but for me it has been so slow it's unusable.

[TRev]

1) I agree with DWX that the sampling rate is not high enough with the phone GPS.

2) It is easy to use between runs but not with video overlay. The video overlay can take an hour or more for a run depending on the length recorded. 80 seconds for example would take about an hour. I am using an S4 and was previously using a Droid Razr Maxx HD.

3) Yes, the accelerometer data, comparing splits between runs and video overlay with % of throttle input and MPH is all helpful.

4) I manually start and stop the video and find that works best for me. I use it to turn my GoPro on/off via Wi-Fi and it does eat up battery. I bought two extra Wasabi batteries with a charger on Amazon for $20 and they work great.

I am using the v1.3 preview which has support to combine the GoPro video with the phone video. It worked most of the time on the Droid Razr Maxx HD but it does not work on the Samsung S4. It is a preview release though. I am sure it will work in the final and everything else has been working good.