RX-Ben

...as reported by a datalogger. Click on the pics for a full view.
Countersteer under braking, loss of braking g's...rear ABS is working overtime here (T1 at NJMP T-bolt).

Actual turn-in is marked by the line that has numbers next to it.



And a bonus, some 115+mph, 1.5g dorifto action, final turn before the front straight. A few mph makes a difference, as does the 2nd lap on a hot track with dead A6s:

drivinhard

I've got the video of that slide. nice piece of driving

RDnomorecobra

Is there a link to that vid? I drive njmp so I eat up videos like these.

sebdavid

Yes, this thread is (almost) worthless without video.

travisnd

Ben which data logger are you using? Is it getting steering angle from the OBDII? I don't have my Traqmate setup to pull OBD-II data.

RX-Ben

I use a Race Technology DL-1. I pull steering angle from the stock sensors, same for brake pressure. You will need to setup an equation for the steering angle sensors as you need to deal with the outputs from the two sensors. I don't think the Traqmate supports math functions (it didn't when I was datalogger shopping). The brake pressure is a simpler connection, though I do some smoothing on mine since it seems to be a noisy sensor.

I think the drift video is NARRA property, I'll leave it up to Mark whether it is ok to post. Not sure if he has video of the braking zone since I think the Viper decided to hang out next to my rear wheel going into T1.
I think it is useful to see the lateral g forces under braking and the associated steering corrections, but I realize that other people don't spend their spare time looking at squiggly lines.

moespeeds

Ok, let me throw this up here because I've been wanting to ask someone this question. Last week was my first ever track day in a car, in my C5 FRC. Car is already setup for the track, pfadt coilovers, wilwoods in the front, stock rear brakes. I have thousands of track miles on motorcycles, both track days and a few years of racing. Initially with the car I was a hot mess, fighting the traction control coming out of the turns, but worse, going in I kept running wide. On my third session the TC/ABS failed, and I smoothed right out. I tend to trail brake a bit and it seemed like without the ABS the rear would slide a bit and point me nicely into the turn. Is this normal in a car? On a motorcycle we would use a combination of engine braking and rear brake to point the front of the bike at the apex on a fast entrance, so it felt natural to me. I have yet to get into the car with a real instructor, I'm trying to get into a PCA day but they just keep filling up on me.

RX-Ben

The rear on my car (w/ABS) slides as much (or more) as I need while trail braking.
Turn off TC and Active Handling.
Run a square tire size setup, that helps as well

moespeeds

I don't know if it was the ABS or the TC causing me to go wide, but the damn thing just wouldn't turn in on the brakes. I thought for sure it was my technique until the TC/ABS failed and suddenly it just felt good. I'm running a square setup 18x10.5 with continental slick takeoffs.

spazegun2213

Ben, while this may sound strange, what pads are you running? I know with DTC-70's F/R I'd really have to work the car to get it to rotate. Now that I have 60's in the rear, it rotates with just me thinking about trail braking.

I'm also glad you are liking the car I had a blast while I was there in mine.

RX-Ben

Hey Ross. It was awesome seeing you there long ago at the RTA event. I was choosing btw an Evo and a C5 and you definitely helped push me in the right direction!

Moespeeds - what pads are you using?

I run a hodge podge of rear pads, but generally in the ht-10/dtc 60/xr-1 range. I have some PFC01s and 99s too. I have not noticed any difference between the pads that I mentioned.

I have no aero, which would would be a help here. Odd that the 70s were not as effective as the 60s, maybe they were out of their temp range.

spazegun2213

yup, that was one of the last times I had the car out. She is up on stands getting a ton of new parts right now C5's are GREAT track weapons, and are stupid fast/fun.

Its not that they were "not as effective" I'd say that they had no braking bias, vs the 60's in the rear shift the bias toward the front. I'd assume that because of this bias the weight shifts as well, and with more weight up front on turn in, allows a little but of a looser rear? maybe... either way I've switched to 60's in the rear for good.

then again YMMV, I do have aero and stoptizzles

2MCHPWR

what was your top speed on main straight? chart tops at 139 but curious how much more you were pushing

moespeeds

I have Wilwood "H" compound on the rear and "A" on the front. The front was a bit grabby for me so I'm gonna try the "B" on the front Monday. Again, I'm a total noob so until my technique settles a bit anything I do could be lack of skill.