Model 3 Track Day: Laguna Seca

[LCR1]

Laguna is not Dakar. It appears Model 3's harsh suspension (even with DIY softening)
tips people to soften the suspension up with incorrect tire pressures for driving on asphalt.

Tires are not designed to be dampers. Their pressure is set according to dimensions and weight applied.
Pressures change somewhat when tires heat up but not that much.
Preference of softening up tires is the result of inappropriate suspension on the vehicle. It might theoretically
even help. Which is a sign of bad suspension.

Brake warning light therefore is flawed if it requires significant time to activate.
Luckily, brake failure was smooth and did not result in a crash.



Tell that to BMW M-division engineers. Those crazies use same brake fluid on their M3, M5 cars as on any other BMW. For many decades. They must be really bad engineers and people here must be really smart ones

Tire pressures are also a characteristic of the tire and what it's being used for. Different tires have different properties that require you to adjust pressure based on track conditions, temp, and setup. Dunlops have much stiffer carcass than Pirelli and therefore you need to make adjustments to compensate. If you can't adjust suspension you can adjust pressure and deal with higher tire temps.

Contrary to what you think and have posted pressure is set according to the required temperate on the track. Lowering the pressure in a tire provides more heat, if you need to cool the tire down you add air to it. You move the pressure to keep the tire at optimal temperature at the track. Our tires come off the warmers at 180 degrees and it's not uncommon for them to come off the track at 200-220 degrees.

You seem to think pressures don't change when tires heat up? A cold tire set at 32 psi will be at 36-38psi off the warmers, off the track will be even higher. If you don't think a 15-20% change off the warmers is a lot you again are confused, and it would be even more off the track.

Keep it all coming.

 

[JADCa]

I have a decent amount of track time at Laguna both teaching and driving. The car seriously needs big brake coolers, new pads and better fluids are helping the symptoms of the over heating brakes, but not solving the core issue of too much heat staying in the system. Brake coolers are not efficient aerodynamically, so it would be dumb for Tesla to put them on, but they are needed for true track use.

Every decent track car needs better brake coolers, from F1 to Porsche to Miatas. You need to pump a lot of cold air over the brakes if you are driving hard and the OP had a pretty decent line for his first session.

 

[mkspeedr]

So much work and in this thread philosophy to 4 wheel trackdays.

I commute on my new track motorcycles for a few break in miles - change the oil (nothing special) - then take it to the track.

I am looking forward to the day an EV can do the same without the commuting part.

 

[ELECTRIC4ME]

How are these Pirelli tires on the street? Much effect on range?

 

[sreams]

I have a decent amount of track time at Laguna both teaching and driving. The car seriously needs big brake coolers, new pads and better fluids are helping the symptoms of the over heating brakes, but not solving the core issue of too much heat staying in the system. Brake coolers are not efficient aerodynamically, so it would be dumb for Tesla to put them on, but they are needed for true track use.

Every decent track car needs better brake coolers, from F1 to Porsche to Miatas. You need to pump a lot of cold air over the brakes if you are driving hard and the OP had a pretty decent line for his first session.

I don't have extra brake coolers on my 1972 BMW (just vented rotors) and do just fine at Laguna Seca. Having the right pads and the right fluid is enough in my case. I'd try just those two things initially with the Model 3 and see what happens.

 

[McRat]

Couldn't disagree with you more. No volume production cars are set up for hot laps at Laguna Seca.

Today there are mass marketed cars that will take a lot of abuse. They aren't even expensive. We are in the Golden Age of Hotrods.

The Model 3 has no sport variant yet. Wanna get rich quick? Make a Track Pack for Model 3's. Tesla has never shown an interest in that demographic.

 

[mattcrowley]

How are these Pirelli tires on the street? Much effect on range?

Grip and cornering onto an onramp is great! Basic driving around town and highway driving...also great! I like the 19" wheel sidewall height better than the limited time I had with the 18" Aero wheels. The rolling through turns with the weight of the Model 3 and the combination of the 18" Aero wheels wasn't ideal for me. The car is much more compliant with the 19" Pirelli tires.

It has been hard to tell the biggest impact on range, since I swapped the wheels and tires from the stock 18" Aero wheels to the 19" Tsportline wheels with Pirelli tires. I swapped them a week after I got the car. It is also hard to tell if the averaging of the Tesla on-board trip computer is still balancing out my change of wheels or general Model 3 learnings. Yea, this question is good, but hard for me to answer. I don't have a good sense on what I see in the range, at the beginning of a trip and the final result. I am also not consistent when I drive, since sometimes I am doing more manual driving and other times it is in autopilot 90% of the trip. It would be good to see someone do a long term test, but it is tough to tell just off of general driving and external conditions (wind, ambient temperature, rain). Sorry, not a great answer...I just don't know.

However, the large 310 miles long range is a nice buffer for daily and long trips. Also it is nice to have a larger battery, when the battery loses 7-10% of capacity over time...it will still have a good overall range.

There are probably better range tires and wheels...I just like the look of these 19" Tsportline and Pirelli wheels better than worrying about range. The lowered Unplugged Performance springs make it look better as well.

 

[JADCa]

A 72 BMW isn't a fair comparison as it has no HP, no weight and no abs, so the brakes are hardly needed. Don't get me wrong, it is a fun track car, just not a modern, fast heavy car that needs extra coming for the track. My 911 needed brake coolers, an additional engine radiator, and a much larger transmission radiator to do more than 2-3 hot laps at Laguna, but that was doing 1:35s

 

[PhantomX]

It really comes down to E=0.5mv^2. Brakes need to remove all that kinetic energy, which gets turned into heat. So now brake pads and rotors need to dissipate that heat. On the street, v isn't typically very high, so E is general not too high. Street driving also doesn't load that energy into the pads and rotors as quick as they do on track, therefore more time for the system to manage heat. Lastly, track driving repeats this kinetic energy to hear often, which doesn't get the pads and rotors much time to release the heat before it needs to handle the next set of heat coming from braking event.

 

[sreams]

A 72 BMW isn't a fair comparison as it has no HP, no weight and no abs, so the brakes are hardly needed. Don't get me wrong, it is a fun track car, just not a modern, fast heavy car that needs extra coming for the track. My 911 needed brake coolers, an additional engine radiator, and a much larger transmission radiator to do more than 2-3 hot laps at Laguna, but that was doing 1:35s

My car makes 210hp and weighs about 3000lbs. It's a 3.0cs with a '91 M30 motor. Not nearly as light as a '72 2002 (about 50% heavier), and makes quite a bit more power (more than double). Yes, the Model 3 weighs 800lbs more and makes more power, but it also likely has much better brakes than what come on my 3.0cs. I'd still try proper pads and fluid in a Model 3 before jumping to more expensive modifications.

 

[mattcrowley]

If interested track and suspension mod people are in the Bay Area on March 21st (6:30pm-9pm), I am going to check out the Mountain Pass Performance team's prototype coilovers and in-development suspension arms for the Model 3 at Alice's Restaurant in Woodside.

Details of the meetup are in this Tesla Motors Club vendor thread: "Wednesday March 21 Evening Meetup - SF Bay Area".

It is an interesting beginning to a new world of electric car mod market. I am excited about this new space!

 

[mattack4000]

It really comes down to E=0.5mv^2. Brakes need to remove all that kinetic energy, which gets turned into heat. So now brake pads and rotors need to dissipate that heat. On the street, v isn't typically very high, so E is general not too high. Street driving also doesn't load that energy into the pads and rotors as quick as they do on track, therefore more time for the system to manage heat. Lastly, track driving repeats this kinetic energy to hear often, which doesn't get the pads and rotors much time to release the heat before it needs to handle the next set of heat coming from braking event.

Spot on, the problem gets worse as you do more laps on it as the heat just sits there. The heat never escapes and you end up boiling the fluid or overheat the pads. Factory brakes are not meant to do that. You can hotlap for 1 or 2, but anything more than that it is going to get really sketchy for most stock vehicles

 

[arnis]

Factory brakes are not meant to do that.

Are you talking about any specific vehicle?

The heat never escapes and you end up boiling the fluid

AFAIK, convection is happening everywhere as we are in Earth's atmosphere

 

[Puddles]

Spank me if I missed this discussion, but why would you put regen on low, especially on the track? You’re either full on throttle or brakes most of the way round so why not get all the help you can braking? Is there “high” regen setting?

The only reason I can think of is that the batteries might get even hotter.

 

[mattcrowley]

Spank me if I missed this discussion, but why would you put regen on low, especially on the track? You’re either full on throttle or brakes most of the way round so why not get all the help you can braking? Is there “high” regen setting?

The only reason I can think of is that the batteries might get even hotter.

I put the regen on 'Low', instead of 'Standard' because I wanted to initially lower the possibility of power unit heating issues. My intent was to try 'Standard' later in the day, if 'Low' regen worked. However, I went in thinking this whole thing wasn't going to get past two laps anyway. So, I was initially happily surprised that I didn't experience thermal limiting on the power unit under 'Low' regen setting. When the brakes wore out, then the day was over, so I didn't have another opportunity to test 'Standard'. Obviously more testing is needed and we don't know if higher ambient temperature and/or 'Standard' regen will ultimately power limit the system. Finding out will be fun!

 

[sreams]

Spank me if I missed this discussion, but why would you put regen on low, especially on the track? You’re either full on throttle or brakes most of the way round so why not get all the help you can braking? Is there “high” regen setting?

The only reason I can think of is that the batteries might get even hotter.

It probably throws off the balance of the car. It adds extra braking force to the rear wheels only.

 

[Daniel in SD]

If battery, motor, and motor controller heat aren't a problem then the AWD regen should help but keep in mind that regen maxes out at about 70kW or so on a Model S. Full braking at 100mph probably needs about 750kW. Wolfram|Alpha: Making the world’s knowledge computable
So you'd only be getting about a 10% improvement.

 

[mongo]

If battery, motor, and motor controller heat aren't a problem then the AWD regen should help but keep in mind that regen maxes out at about 70kW or so on a Model S. Full braking at 100mph probably needs about 750kW. Wolfram|Alpha: Making the world’s knowledge computable
So you'd only be getting about a 10% improvement.

3,800 pound car at 100 MPH is 1722310 J (W×s) or 0.478 kWh. 100 MPH is 147 ft/sec, so stopping at 1G takes about 5 seconds. Deceleration in 5 seconds takes 344 kW and 370 ft.

So regen would take 20% of the heat off the brakes in that situation assuming 70kW limit.

750kW would stop you in 2.3 seconds but at 2 Gs.

Edit: kinetic energy is 1/2×m×v^2 that value divided by deceleration time gives watts needed.

 

[Daniel in SD]

3,800 pound car at 100 MPH is 1722310 J (W×s) or 0.478 kWh. 100 MPH is 147 ft/sec, so stopping at 1G takes about 5 seconds. Deceleration in 5 seconds takes 344 kW and 370 ft.

So regen would take 20% of the heat off the brakes in that situation assuming 70kW limit.

750kW would stop you in 2.3 seconds but at 2 Gs.

Edit: kinetic energy is 1/2×m×v^2 that value divided by deceleration time gives watts needed.

The 750kW is the instantaneous power at 100mph. 750kW decelerates you at 1G at 100mph, 2G at 50mph (Not actually possible to do much more than 1G on tires) and infinite Gs at 0mph. You're not decelerating from 100mph to 0mph on a race track. A more realistic scenario is 100mph to 50mph which would be an average of 566kW: Wolfram|Alpha: Making the world’s knowledge computable

Force = power * velocity so the faster you go the more energy you need to accelerate/decelerate at the same rate.

 

[mongo]

The 750kW is the instantaneous power at 100mph. 750kW decelerates you at 1G at 100mph, 2G at 50mph (Not actually possible to do much more than 1G on tires) and infinite Gs at 0mph. You're not decelerating from 100mph to 0mph on a race track. A more realistic scenario is 100mph to 50mph which would be an average of 566kW: Wolfram|Alpha: Making the world’s knowledge computable
View attachment 285227
Force = power * velocity so the faster you go the more energy you need to accelerate/decelerate at the same rate.

You're right on all counts, didn't realize that you were solving for 1 G deceleration.
(And again I forget that I can't average power over deceleration)