Model 3 Performance feels slow?

[GSP]

I had my Model 3 Performance after 2 years or so. I liked it but I started to miss the engagement and drama you get from performance based ICE vehicles. I am back in a Camaro ZL1, which destroys my Model 3 Performance in all areas except for 0-60mph. The hard AWD launch of the Tesla gets the edge, the ZL1 gets to 60 in about 3.6 seconds. But for about the same money as the Tesla I can trap at 125mph, Recaro seats, HUD, mag ride suspension, drive modes, E-diff, V8 dual exhaust note, sporty interior ability to disable the nannies and have some fun.

I drove a C8 on track but it did not feel as visceral as the ZL1. I am hearing good things about the new Nissan Z, and it comes with a manual. Even Toyota is adding a manual option to the Supra now. While EVs are great for daily drivers I am hoping they keep producing exciting cars for driving enthusiasts.

People still keep horses for recreation and sport. It would be a more blah world if they didn’t. I am confident that the same will hold true for IC engine vehicles. Motorcycles espically, as their primary use in the US already is for recreation and sport.

Like horses, I think ICEs are great for other people. I am happy with less maintenance and noise.

GSP

 

[Knightshade]

People still keep horses for recreation and sport. It would be a more blah world if they didn’t. I am confident that the same will hold true for IC engine vehicles. Motorcycles espically, as their primary use in the US already is for recreation and sport.

Like horses, I think ICEs are great for other people. I am happy with less maintenance and noise.

GSP

To be fair- they never banned the sale of new horses. That doesn't appear to be how things are going for ICEs long term.

 

[GSP]

To be fair- they never banned the sale of new horses. That doesn't appear to be how things are going for ICEs long term.

I seriously doubt IC engine “bans” will ever be absolute.

Norway is widely reported to have a ”ban” for 2025, but it actually is a “goal.” Norway intends to use this goal as a guide for how to phase out subsidies for EVs. The EU has a “ban” for 2035, but it still allows small manufacturers of 1000 or less cars per year to build ICE vehicles.

I don’t know if California’s ban is absolute or not, but when it gets close to the reality of an absolute ban in a year or two, then I predict that the rights of a handful of individuals to buy, sell, and build a few ICE cars will prevail over the extremely small amount of emissions from a small fleet of special use cars for racing or recreational driving. Of course my prediction can be wrong, but I would be willing to bet a lot that is not.

GSP

PS. Another point is that horse emissions were a huge public health problem, but horses were never banned. They were replaced with automobiles due to the economic advantages, and the public health problem was solved. At least until the automobile population grew to many times what the horse population was.

 

[mpgxsvcd]

I seriously doubt IC engine “bans” will ever be absolute.

Norway is widely reported to have a ”ban” for 2025, but it actually is a “goal.” Norway intends to use this goal as a guide for how to phase out subsidies for EVs. The EU has a “ban” for 2035, but it still allows small manufacturers of 1000 or less cars per year to build ICE vehicles.

I don’t know if California’s ban is absolute or not, but when it gets close to the reality of an absolute ban in a year or two, then I predict that the rights of a handful of individuals to buy, sell, and build a few ICE cars will prevail over the extremely small amount of emissions from a small fleet of special use cars for racing or recreational driving. Of course my prediction can be wrong, but I would be willing to bet a lot that is not.

GSP

There will never be an absolute ban of all internal combustion engine vehicles in the US. For example there will always be museums with them. They will probably still be used in some forms of racing for all of my lifetime.

However, I do think they will get banned for normal traffic on highways in California by 2040. In other places around the world it will probably happen sooner.

Even with those bans there will still probably be exceptions like there is now for “collector’s cars” and current EPA Driving regulations.

That number of ICE cars on the road will be so insignificant though. The transition to electric is already too far down the path to reverse it but for the time being there still is a need for ICE cars on the road.

Eventually all of the manufacturers will stop selling ICE vehicles. I think the last ICE consumer vehicles that will be sold will be the large pickups and SUVs. Those still need ICE as opposed to BEV to really do all of the functions buyers want them to do.

 

[GSP]

@mpgxsvcd - Agreed. I would add that not only old cars, but also a few new ones will be built. Race car builders typically build less than 1000/year, so good for EU rules. They also could build a few road cars, like McLaren does. This was how the auto industry was in the beginning, with companies like Marmon building the first Indy 500 winner (in 1911), and also hand-built road cars.

GSP

It seems that I wandered a bit OT, but the connection is that EVs like the M3P, will outperform ICE sports cars, but ICE cars will still be fun to race. They still race horses, and there still is a lot of spectator interest.

 

[Apprunner]

@mpgxsvcd - Agreed. I would add that not only old cars, but also a few new ones will be built. Race car builders typically build less than 1000/year, so good for EU rules. They also could build a few road cars, like McLaren does. This was how the auto industry was in the beginning, with companies like Marmon building the first Indy 500 winner (in 1911), and also hand-built road cars.

GSP

It seems that I wandered a bit OT, but the connection is that EVs like the M3P, will outperform ICE sports cars, but ICE cars will still be fun to race. They still race horses, and there still is a lot of spectator interest.

EVs will out accelerate ICE sports cars for sure but ICE sports cars have significant advantages for overall motorsport activities that will take a long time for EVs to overcome. You simply carry much much much more energy per weight with gas so driving dynamics, length of drive, and refueling time are pretty significant advantages. But, other than that use case, EVs will probably be better for light, sporty driving in city and daily commute.

 

[mpgxsvcd]

EVs will out accelerate ICE sports cars for sure but ICE sports cars have significant advantages for overall motorsport activities that will take a long time for EVs to overcome. You simply carry much much much more energy per weight with gas so driving dynamics, length of drive, and refueling time are pretty significant advantages. But, other than that use case, EVs will probably be better for light, sporty driving in city and daily commute.

I totally agree with this. For straight-line acceleration electric has some real advantages right now. Once you put turns into the equation those advantages start to disappear.

 

[gearchruncher]

That isn't how this works and your math wasn't even correct even if you were comparing the correct things. You used diameter when you should have used radius there and yes that would have made your second number even lower. In addition your units of measure for that 1,250 number aren't actually Joules. That is Joules per second. You have to multiply that by 3.2 seconds to get Joules. Next, you need to accountant for all four wheels and tires and the weight difference is 10 lbs not 5 lbs. Finally, you used 5 lbs as the force there. That is the weight difference of the wheel not a force or torque being applied to the wheel. That makes no sense at all to use the weight there. You would need to use the torque being applied to the wheel there. However, none of that matters because your second number doesn't represent anything relevant to what we are talking about.

Didn't even bother to check my math here, just told me I was wrong, eh?

1 HP is 745 J/s because 1 HP is 745W. So 5 HP is 3730 J/s, times 3.2 seconds. That's 12,000J. Exactly what I said, and not off by 3.2.
That's the total energy you gain from 5HP. Which you, in your first post indicated was an amount so small to be ignored.

And no, I did not use radius in calculating the MMOI of a 5lb torus. Nor did I use 5LB as a force.
A 5lb MASS torus with an inner RADIUS of 10" and outer of 13" has a MMOI of 8.472 lb*ft^2.
This is a very conservative estimate, because I am assigning ALL of the mass to the tire which is at the maximum radius.

That torus spinning at 800 RPM is 60MPH. 800 RPM for that MMOI takes 1,250J to achieve.

Sure, you need 4 tires. So that's 5,000J. Now you claim it's 10LBS not 5. Ok, 10,000J.

It literally takes less than 5HP to accelerate 4, 10LB lighter wheels to 60 MPH. Yet you say 5HP is what you gain from a 1% change in diameter (or radius, funny how math works that way), and is irrelevant.

Let's not forget that a 4,200LB car at 60 MPH has about 685,000J of KE, just to show how little a 10KJ change makes. It's literally <0.002%.

And let's just prove to ourselves that this works. 685KJ over 3.2s is 214KJ/s. 214KJ/s is 290HP, delivered continuously over that 3.2 seconds. Sounds basicity exactly right for a M3P which has to limit power at lower speeds and falls off up top.

It appears that you are trying to calculate the energy at at constant speed for the wheel in that second part. I am not sure why you think that is relevant? That isn't going to tell you anything about acceleration. Your analogy just isn't correct at all.

Yes, because the only thing that matters is the energy it took to get to that speed. Outside of wheel spin, gear ratios, etc, all that matters is the rate of energy put into the system and total energy needed. The total energy needed to get 10 lb lighter wheel to 60 MPH is 2,500J. You have 3.2 seconds to do that. That's 781 J/s. That's exactly 1 HP per wheel that 10 lbs per wheel saves you.

I have shown you exactly why rotational mass is so important with both the equations and with actual data from controlled tests. I am not sure what else I can do to convince you that changing to smaller and lighter wheels works.

No, you have completely screwed up the equations, and done uncontrolled tests with different diameter and mass wheels and tires. So you haven't proven that the wheel size matters at all, and you've dismissed diameter completely even though it has a larger impact to the equation by your own admission than the mass change.

If you're gonna refute this run the actual math, with numbers, don't just tell me I did it wrong or that "rotational mass matters more."

 

[gearchruncher]

Oh, and if you want to use Jason's numbers....
0.878 kgm^2 at 800 RPM = 3,081J
0.486 kgm^2 at 800 RPM = 1,705J

A difference of 1,376J per wheel. Surprisingly close to my 1,250J estimate from a 5 LB difference, and much less than the 10LB I used above, because as I said I applied the mass much farther out than 9". So if you want to stick with Jason's numbers, we're at 5,500J less to get the smaller wheels to 60 MPH, which over 3.2 seconds takes....

2.3 HP. Half of the irrelevant amount of 5HP that the diameter change makes.
Thanks for backing me up Jason!

(Oh, and while diameter=gearing, gearing impacts all 4,200 lbs of the car's acceleration, while wheel mass changes only impact that <200lbs of wheels and doesn't do anything for the remaining 4,000 lbs)

 

[buckets0fun]

Note to self: @gearchruncher is also a number cruncher and positively obliterated the retort to his previous ‘back of the napkin’ math, that turned out to be beyond correct.

Dear sir, you win many internet points for the day. well done.

 

[mpgxsvcd]

If the 1% diameter isn't relevant, and you believe you can do the math, what about the 18" wheels gained you 0.08?

(FYI, 5HP over 3.2s is 12,000J, and a 26", 5lb ring at 800 RPM is 1,250J)

This is all you wrote in your post. I couldn't tell what you were doing to come up with your 1,250J. The 5lbs made no sense to me because the difference in wheel weight is actually 10 lbs and I never said it was anything else. Jason's data is based on a smaller weight difference because his car had the older 20" wheels instead of the UberTurbines. I didn't realize you were representing the mass as a ring where the tire is. Jason had treated it like a thin walled cylinder. That is fine treating it like a ring I just couldn't tell you were doing that from the data you gave. Because you used half the weight it looked like you had used the diameter instead of the radius.

I can see where you are getting your 1,250J from now that you explained where you were getting your numbers from. Yes, absolutely we are talking about a very small difference in moment of inertia compared to the total inertia of the car. We are also dealing with a small difference in acceleration. .08 seconds is very small but not insignificant.

I was wrong when I said it is orders of magnitude different. You correctly pointed out that the 80% difference applies to a small portion of the energy while the .8% difference applies to a much larger portion of the energy output. However, I didn't see where you calculated what the affects of the .2" diameter difference would be. .8% of the 290 HP you gave would be 2.32 HP. Definitely not orders of magnitude different like I incorrectly stated. I acknowledge that. However, it is about half of the 4HP that the rotational inertia would give you according to your calculations.

I didn't say that 5 HP is an insignificant amount. I said that the affects of reducing the outside tire diameter are insignificant. The issue I have is that you are basing your calculations for reducing the tire diameter on the specs for the tire. It is too imprecise to just take that .2" spec as gospel. Is it .2" difference when mounted? Is it .2" when mounted but at a certain tire pressure? It isn't a measured value and if it is just .1" off when it is on the car that would drastically change the calculations of the affect it has.

I tried lowering the tire pressures in the car drastically. That reduces the radius of the tire at the point of contact. However, it had zero affect on the acceleration of my car. Yet, all of the other 50+ passes I did showed the exact same differences each and every time. I went from running 11.4s to 11.3s over and over again regardless of the tire diameter but each and every time I was using the smaller and lighter wheels. Once I switched back to the 20" wheels I went back to running the same times I had before.

Sorry I snapped at you. I see what you are calculating now and it definitely has merit. I just get frustrated when people repeatedly say that reducing size and weight of the wheels has no affect whatsoever and they claim gearing affects it more. I think your own calculations show the wheel's size and weight have a greater affect. In addition, all of the testing I have done never shows any improvements from gearing differences at all. If that gearing mattered then simply reducing the air pressure in the tires would reduce the times but that never seems to be the case.

You are correct to point out that there can be other things that can affect the performance. However, I don't believe the tire diameter difference has the affect that you think it does. I plan on testing that though. Once my current tires wear out I am going down to a 225/45/18 tire. That will reduce my outer tire diameter down to 25.9" from the current 26.3". That would certainly be a big enough difference to demonstrate if it matters or not. That is just over a 2% decrease in tire diameter instead of .8%. I suspect I will gain some acceleration on the 0-60 mph if it really does reduce the diameter by over half an inch. However, I think it will reduce the acceleration after the Horsepower peak at 55 mph and end up making me slower the faster I go. It is worth the test though.

 

[gearchruncher]

This is all you wrote in your post.

Yeah, because it was a response to you saying this:

You have to realize that a 1% difference in HP is at most 5.4 HP if a fully preconditioned Model 3 has 540 HP. It isn’t even really 5.4 HP. The difference in diameter is closer to .8% which would be about 4.32 HP.

On top of that everything you gain below the HP peak at 55 mph you lose after that speed.

Wheel diameter differences of less than 1% are irrelevant. I can adjust the tire diameter by that much just by letting some air out of the tires. I have tried that too and it doesn’t make it faster.

Where you were doing some math yourself, and claiming 5HP was irrelevant. I don't see how you can claim you didn't say 5HP was irrelevant when you specifically said less than 1% wheel diameter is insignificant because it's only 5HP.

So I asked you do to the rest of the math, since you seemed willing to use math. And I gave you some really simple hints as to what the math should look like.
Math that was really simple if you really get it. But all you could do was call it wrong.

And BTW, you never mentioned 10lbs at all. I guessed at 5lbs, which is probably pretty accurate if you have a wheel 10lbs lighter, and then have to add a tire with more sidewall to keep the same diameter.

Ignoring all of that, I think the data you have is really interesting. But it's not a test that only changes one variable. I've worked with a lot of people that have worked for Tesla over the years, and they have all sorts of stories about what can gain a tenth in a Tesla. Anything that limits weight transfer for instance. I wouldn't be surprised if the actual difference is the larger sidewall in a 18" wheel/tire, which allows more deflection. Like an actual drag radial behaves. But the energy math on lighter wheels just doesn't pan out. It's much more likely this is about how the car hooks up and how early it can put the power down than the mass.

What we really need to see is motor power curves over every run, then you could see if it was that there was more total power output, or the exact same power led to quicker acceleration.

We also need to make sure we are clearly talking 0-60 vs quarter mile. Everything so far is 0-60, but now you're suddenly bringing up quarter miles, which involve much higher speeds and longer integration times, which may change what is a dominant factor.