HPDE experiments, results and observations

[ThunderMoose]

Originally Posted by rhyary

When I get into my car I blind test all the equipment including the tires. I care less what equipment I have, once I am on the race track

I manage the traction I have the best I can at the moment. I honestly don't say to my self I have R7, drive this way, or I have Cup2 drive that way.

All data is analyzed back when I am at home.

That's probably a good philosophy. I think tires tend to have a lot more in them than folks think. I saw my coach beat my PB by nearly 4 seconds on tires that I was ready to throw out.

[rhyary]

Originally Posted by ThunderMoose

That's probably a good philosophy. I think tires tend to have a lot more in them than folks think. I saw my coach beat my PB by nearly 4 seconds on tires that I was ready to throw out.

^

[dparm]

Do you have a math channel for slip angle yet?

[rhyary]

Originally Posted by dparm

Do you have a math channel for slip angle yet?

I don't. But I can create it if you give me the formula

[dparm]

Originally Posted by rhyary

I don't. But I can create it if you give me the formula

It's a little tricky, but here goes. Credit goes to Precision AutoResearch for providing these in a seminar a few years ago.



Understeer = (WheelAngle-RadiusAngle)/LatG

The output is in "deg/g". RadiusAngle is measured in degrees, and LatG is measured in g. A negative value indicates oversteer and a positive value indicates understeer.



As you can see, you have to do two nested formulas:


Wheel angle = Steer/SRatio

The output is in degrees. SRatio is the steering rack ratio. A negative value indicates left and positive value indicates right. The wheel angle is telling you how far the front wheels are turned for any steering wheel input.



Radius angle = 57.3*(wheelbase/12)/CornerRadius

This is also called the Ackerman angle. The output is in degrees. Wheelbase units are INCHES and corner radius units are FEET. Negative values are left, positive values are right. This formula is telling us the nominal angle the front wheels have to be turned for a given radius.

[rhyary]

Originally Posted by dparm

It's a little tricky, but here goes. Credit goes to Precision AutoResearch for providing these in a seminar a few years ago.



Understeer = (WheelAngle-RadiusAngle)/LatG

The output is in "deg/g". RadiusAngle is measured in degrees, and LatG is measured in g. A negative value indicates oversteer and a positive value indicates understeer.



As you can see, you have to do two nested formulas:


Wheel angle = Steer/SRatio

The output is in degrees. SRatio is the steering rack ratio. A negative value indicates left and positive value indicates right. The wheel angle is telling you how far the front wheels are turned for any steering wheel input.



Radius angle = 57.3*(wheelbase/12)/CornerRadius

This is also called the Ackerman angle. The output is in degrees. Wheelbase units are INCHES and corner radius units are FEET. Negative values are left, positive values are right. This formula is telling us the nominal angle the front wheels have to be turned for a given radius.

Well, someone perhaps can chew this further for me.

[ThunderMoose]

Originally Posted by rhyary

Well, someone perhaps can chew this further for me.

I'm stuck at how to calculate corner radius. I could in a skid pad but am not sure how to do it for the track.

Dan - do you have an example of how you've done this for MSRC ?

[dparm]

Originally Posted by ThunderMoose

I'm stuck at how to calculate corner radius. I could in a skid pad but am not sure how to do it for the track.

Dan - do you have an example of how you've done this for MSRC ?

It's no different than a skidpad.

Radius = (velocity^2 / acceleration)


I had to Google it for AIM since I don't have their software, so I think it's this:

abs(1/(GPS_Speed*MPH2FTS)^2/(GPS_LatAcc*32.2)

[ThunderMoose]

Originally Posted by dparm

It's no different than a skidpad.

Radius = (velocity^2 / acceleration)


I had to Google it for AIM since I don't have their software, so I think it's this:

abs(1/(GPS_Speed*MPH2FTS)^2/(GPS_LatAcc*32.2)

Very cool!

[dparm]

Originally Posted by ThunderMoose

Dan - do you have an example of how you've done this for MSRC ?

Here it is in Pi Toolbox as I'm going through "wagon wheel", where I always have fun dancing the car right on the limits of oversteer and understeer. You can see it in the trace -- notice how the line dips up and down, which indicates I am inducing and then catching very small slides.

[Bartledoo]

Originally Posted by dparm

Here it is in Pi Toolbox as I'm going through "wagon wheel", where I always have fun dancing the car right on the limits of oversteer and understeer. You can see it in the trace -- notice how the line dips up and down, which indicates I am inducing and then catching very small slides.

That's a pretty sweet tool.

[rhyary]

Originally Posted by ThunderMoose

Very cool!

Thunder, are you working on the whole formula?

[dparm]

Originally Posted by rhyary

Thunder, are you working on the whole formula?

My advice is to build 3 separate math channels, then simply embed them. It's much easier to troubleshoot that way.

Give it a shot, I think you'll find this is easier than you think. Plus, it will open the door to other interesting things. Understanding the "why" in the formula will be enlightening...it's all physics, in the end.

[admranger]

Originally Posted by dparm

My advice is to build 3 separate math channels, then simply embed them. It's much easier to troubleshoot that way.

Give it a shot, I think you'll find this is easier than you think. Plus, it will open the door to other interesting things. Understanding the "why" in the formula will be enlightening...it's all physics, in the end.

Science doesn't matter if you believe you're right.

[rhyary]

Competition showed up in force to win the NYST HPDE today.

First time I see here Ferrari that means business.

[Bartledoo]

Originally Posted by rhyary

Competition showed up in force to win the NYST HPDE today.

First time I see here Ferrari that means business.

Wow she has some long hair.

[DRLane]

Originally Posted by Bartledoo

Wow she has some long hair.

I didn't even notice her.. ha!

[rhyary]

Not a bad day today.
The Corvette did a track record of 1:27.8. Self reported. I don't have a way to verify it. But the driver promised to send my a video link to verify. Driver said car is 3050Lbs with him sitting in the car

Previously it was a Viper ACS @ 1:28.9

The Ferrari driver (not the long hair) self reported 1:32 in previous track day. He was not keeping time today. He said.

I managed 1:37.35 but the Cup2 were gone in 5 x 20min sessions.
Cruised the 6th on 1:44, and gave up on the 7th.

Did many 1:38.x and 1:39.x

My camera got knocked off position and my 1:37.3 had the data feed, but the camera was pointing at the dashboard. Grrrrrr

Here is a spent 2016 sticker MPSCup2. It got me home.

Temp hot was inside 152 and outside 152. I am happy with the setup and the -3.5 camber. It is the first time I consume the middle of the tire.

PSI was 36 hot. I started at 31 and thought it would go up to 38. but it did not.

[rhyary]

Stats
Date: June 12 2020
Organization: GottrackLi
Track: NYST
Weather: Dry

Tires Front: Stickers MPSCup2 Star
265/35/19 Tire Rack new day 1

Tires Rear: 2018 Proxa RR
2018 eBay new day 2

Brake Threshold: 600 psi (the tone you hear)

Best laptime: 1.37.35

DSC: On

Comments:
This was a fast setup. 1:37.35 is the fastest I went with none slicks on the front. For the first time I went thru 8-9-10 starting at 107mph at 8 and over 100 between 8 and 9.

I am happier with my trail braking but it is no perfect by any means. I was carefully to not induce understeer with getting in the throttle too early but the car still understeer. But it feels like a safe understeer so I am happy about that.

I reviewed the Corvette 1:27.8 video and the one impression I had is that he goes the shortest distance and cut thru all the corners. With 315 A7 he just take the turns straight with out trying to ne clever. I can do that line if I go 1:44, but no way for me to do that at sub 1:40.

I also noticed he does not go over the curbs. perhaps because he is so low that he can't, and at the same time, he does not need to.

Anther observation is that his lowest speed thru the turn is not night and day, but most of the turn he is faster than 1:37 pace.

What I am going to try on next NYST day is to go his line at the speed I can do it and see how fast I can do that line.

I don't have a video as I said previously because the camera got nocked down and was filming the dash :-(

Oh... one can dream about A7 all day long....

[Kelse92]

Originally Posted by rhyary

Here is a spent 2016 sticker MPSCup2. It got me home.

Temp hot was inside 152 and outside 152. I am happy with the setup and the -3.5 camber. It is the first time I consume the middle of the tire.

PSI was 36 hot. I started at 31 and thought it would go up to 38. but it did not.

I would try a lower hot pressure on the Cup2’s, like 30. Middle of the tire delaminating like that seems like pressure a little too high

[rhyary]

Originally Posted by Kelse92

I would try a lower hot pressure on the Cup2’s, like 30. Middle of the tire delaminating like that seems like pressure a little too high

hmm, this sounds like a drastic change.

I have another pair of 2016 Cup2 so I can try 32?

The interesting thing is that I ran Cup2 MO-1 on 38 hot and they were consumed as expected.

[rhyary]

Stats
Date: June 13 2020
Organization: SCDA
Track: Lime Rock Park
Weather: Dry

Tires Front: Stickers Ecsta PS91
2019 275/30/19 Tire Rack new day 1

Tires Rear: MPSS
2019 275/35/19 used eBay day 1

Brake Threshold: 1000 psi (the tone you hear)

Best laptime: 1:03.2

DSC: On

Comments:
Oh Boy. This is so much faster track than NYST.
End of straight 138mph

Worked on trail braking and not hitting the throttle too early.

I just could not get bellow 1:03. I don't have a good explanation. Car felt good.
Perhaps driver fatigue?
Perhaps the much faster pace that it was just too scary to push harder?
Many congested laps with slow traffic?.

It was a perfect trackday but I just could not get faster than 1:03.

Perhaps the tire combination never gave me the confidence to go faster.

Perhaps the the setup was too soft for the speed. For the last session I did clicked +1 on the shaft for all 4 corners. The car felt better and more reassuring but did not resulted in a better time or willingness to push harder on the last session. Should have done it first session

Video is not very interesting, but will upload later for completeness

** Edit **
Video link