HPDE experiments, results and observations

[rhyary]

Originally Posted by FXMR

Have to drop in and say wow...I just read through all of this thread and there is a WEALTH of information. Awesome thread

rhyary I was the black F80 near you in the paddock at LRP on the 6th (note: not the black M4 that had the incident). Your car was killer and it lit the fire even more for me to get into an E92 HPDE car. Cheers!

Oh cool. Did we say hi?
Thanks for the compliments.
Which session were you running, int2 or advance? may be I can find you on my videos and cut you a video.

Do you know if the one that had the accident was the M4 GT4? I talked to the GT4 at length before the sessions started. It was a beautiful car and he was on Hoosier slicks and I had to ask about his lap times.

I passed that car at some point so it is on my video some place. Will look for it.

will you be coming on the 20th for the open day?

[FXMR]

Originally Posted by rhyary

Oh cool. Did we say hi?
Thanks for the compliments.
Which session were you running, int2 or advance? may be I can find you on my videos and cut you a video.

Do you know if the one that had the accident was the M4 GT4? I talked to the GT4 at length before the sessions started. It was a beautiful car and he was on Hoosier slicks and I had to ask about his lap times.

I passed that car at some point so it is on my video some place. Will look for it.

will you be coming on the 20th for the open day?

Unfortunately we did not! I was in Int1 so we were in opposing run groups. Although I've been doing HPDE for quite some time it was my first time running with SCDA at Lime Rock. It was a great experience, definitely doing it again but sadly can't make it to the event on the 20th.

Correct - it was the M4 GTS with the Hoosiers. That car was gorgeous.

[rhyary]

Originally Posted by FXMR

Unfortunately we did not! I was in Int1 so we were in opposing run groups. Although I've been doing HPDE for quite some time it was my first time running with SCDA at Lime Rock. It was a great experience, definitely doing it again but sadly can't make it to the event on the 20th.

Correct - it was the M4 GTS with the Hoosiers. That car was gorgeous.

oh no. That GT4 was pristine

[DRLane]

So, was it a m4 GT4 or a m4 GTS :

[rhyary]

Originally Posted by DRLane

So, was it a m4 GT4 or a m4 GTS :

The one that comes with the cage. I am not too knowledgeable about the model numbers

[DRLane]

Originally Posted by rhyary

The one that comes with the cage. I am not too knowledgeable about the model numbers

Gotcha - GTS. The GT4 is a factory built race car.

[dparm]

Fuck, a GTS? Those are pretty rare. I think only 300 made it to the US.

[rhyary]

Some stats on the 285/30/19 PS91:

Last two SCDA at LRP started with a sticker 2020 PS91.

209 laps about 215 minutes
most laps 1:03-1:04 range
many laps 1:02
few laps 1:01
two laps 1:00.9

There is one more day left on the front and it will be 4 hours of open track. I am sure this tire front set will be done, even if not on the cords.

This nice thing about these stats is that all three days will be at LRP which is average abrasiveness.

Given my driving is not perfect, I am 100% sure I can get below 60 sec on this $189 tire. And the question then would be, can I justify a more expensive tire to gain a second on HPDE day. I would say that sub 60 is good enough and the attention should be focused on driver skills.

If it last a third day, and I get the number of minutes, pace and price the quest to quantify the value of $189/tire would be answered to a point of useful information.

Because I have had some issues with tirerack that were resolved with a gift card and discount, I also have a 2020 MPSS 285/30/19 so I can run a similar comparison on a $334/tire.

[rhyary]

Originally Posted by dparm

Fuck, a GTS? Those are pretty rare. I think only 300 made it to the US.

You can see the car here in the Nov 6th advanced group

https://shawnpiercephotography.pixie...2020/advanced/

[rhyary]

Weather at LRP for Friday 20th shows no rain and 50 degrees. So lucky if it stays this way.

I have been testing the suspension around my house. I setup the rebound to higher number (slower), now sitting on mid point of 12 out of 24 clicks.

My plan is to trail break deeper in to big bend and into 3. Last time at LRP that made my rear light and I want to see if more rebound in the rear will help that.

I changed my front road damping from 6 to 10 and I am testing grip on ramps around my house. It is more tout config now, but the traction control is not lighting up. For the track it goes +4.

PSI cold is now known, so I am done messing with that..

I am starting on the front with PS91 285 and do not expect them to last all 4 hours. l will switch to the 265 Cup2 at some point.

I expect the Rear 295/30 MPSS to last all 4 hours of open track day.

[Bartledoo]

If you don't want your rear end to get light, then don't trail brake. That's kinda the point of trail braking.

Increasing rear rebound damping will transfer weight off the rear faster under braking, unless you meant decreasing rear rebound damping.

What is "front road damping"? Low speed compression damping?

[rhyary]

Originally Posted by Bartledoo

If you don't want your rear end to get light, then don't trail brake. That's kinda the point of trail braking.

Increasing rear rebound damping will transfer weight off the rear faster under braking, unless you meant decreasing rear rebound damping.

What is "front road damping"? Low speed compression damping?

In the front I change the HS damping +4 when I get to the tack and -4 to go home (i call it road setting) I don't change the rear if I like it on the track. I am happy with the LS so I keep the same.

I hear you about the rebound, I will change it from the mid point based on how I feel.

I understand what you are saying about the trail braking. if my car was to "soft", then just moving it to half point does not mean now it is too stiff.

[rhyary]

Unfortunetly on 11/6/20 he had a car off and a flip on the hill.

And again on 11/20/20 we had some one hit the wall, bounced off and rest by the bridge.

A reminder that this is fun with at times
consequences, just like friend with benefits.

[rhyary]

Late apex, aka don't try turnning if you forget to get off the brakes.

A reminder that asking from the tires to turn while on 1400psi brake pressure is asking too much.

Or, don't use mixed tires.

Chose your description. Be creative

[rhyary]

Stats
Date: Nov 20 2020
Organization: SCDA
Track: Lime Rock Park, CT
Weather: Dry beautiful day
4 hours Open Track

Tires Front: Ecsta PS91 2020 day 3
285/30/19

Tires Rear: MPSS 2016
295/30/19 day 4

Time: 1:00.96
Many laps on 1:01 and 1:02


Comments:
Second time I am going below 1:01.
However, more laps on 1:01, more laps 1:02.
Many situations of managing traffic, managing off-line situations. In general feeling more comfortable at a lower lap time.

59 second is still illusive but that will have to wait for 2021.

Tires.
No complains about the PS91. They last, they run at 150 degrees and are predictable. They may not be a 57-58 sec lap time, but they can definitely do sub 60 LRP.

The MPSS are great too but at a higher cost.

[rhyary]

Some other stats:
Total laps 109
Total laps 60.x sec 1
Total laps 61.x sec 27
Total laps 62.x sec 35

Total laps below 63 seconds 52

[rhyary]

Miata fun. Observed from safe distance.

[rhyary]

Here are my frequencies plugging what I know into @tsk94 spreadsheet:

** Update with divorced set **
.

[tsk94]

Originally Posted by rhyary

Swaybar calculation for the H&R using the Hotchkis information:

The H&R are 42% stiffer than stock
The Hotchkis are 52% front and 56% rear

The Front is 295 x .8 = 236 lb/in
The Rear is 175 x .75 = 131 lb/in

If I did my math correctly

Stock M3 sway bar rate are as follows:
195lb/in front
112lb/in rear

Using these numbers it should be quite easy to calculate the bar rate of your H&R's

[tsk94]

Using 42% stiffer then stock (assuming both front and rear are 42% stiffer) I get:
277lb/in for the front H&R bar
and 159lb/in for the rear

[rhyary]

Originally Posted by tsk94

Using 42% stiffer then stock (assuming both front and rear are 42% stiffer) I get:
277lb/in for the front H&R bar
and 159lb/in for the rear

This is way better.
Yes front and rear 42%
i didn't know the OEM lb/in numbers.

Thank You!

[rhyary]

Very educational during the off-season

Specifically I found it useful to know that the tires scrub can generate -.2-.3g (deceleration) and the rest is trail braking

And a good explanation of the friction circle and now I can actually go back to my lap times and understand better my data.