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Knurled.
Knurled. GRM+ Memberand MegaDork
11/21/19 1:48 p.m.

In reply to rslifkin :

According to Audi, in 1980, with 1980 technology for all systems relevant, the breakeven point was about 100mph.  If it took, say, 100hp to go 100mph, the tires were more efficient enough with four at 25hp/tire than two at 50hp/tire that the benefits more than made up for the losses.  And those old 016 drivetrains were extremely lossy.  Tough as all heck, but lossy.

 

With that in mind, I wonder about the efficiency effects of duallies.  (Counterpoint: Big singles, although I mainly see those on trailers, not tractors)

rslifkin
rslifkin UltraDork
11/21/19 1:51 p.m.

I wonder how sidewall height impacts that equation?  I'd expect a shorter sidewall to show a smaller difference than a tall one.  

Also, with a 100 mph breakeven point, that means for 99% of the driving most of us do, AWD would come out less efficient (especially in traffic where the extra weight hurts more).  

Knurled.
Knurled. GRM+ Memberand MegaDork
11/21/19 1:53 p.m.

In reply to rslifkin :

Germany.  smiley

 

I personally wouldn't do without it anymore.  And even then, finding myself spinning tires trying to cross a wet road is maddening.  I don't like being limited by my equipment.

mtn
mtn MegaDork
11/21/19 2:12 p.m.
Keith Tanner said:

For example, the single motor (RWD) Model 3 Long Range has a single 283 hp motor and weighs 3800 lbs. The AWD has a 252 hp rear motor and a 197 hp front and weighs 4072 lbs. The Performance has the 283 hp rear motor from the RWD and the 197 hp front motor and is rated for the same weight. All of those have the same battery pack. The RWD is a little more efficient, 26 kWh/100 miles vs 29 kWh/100 miles.

0-60 is quoted as 5.0, 4.4 and 3.2 for the three variants. Some of that is the extra power, some of it is the extra traction. Like it or not, AWD will provide more forward thrust when traction is marginal for the needs, whether it's due to a low coefficient of friction on the road or a high torque delivery at the wheel.

 

Pretty sure you're well past the diminishing returns of "MPG" at that point, unless you drive 100k+ miles a year. Probably less than $100 difference in electricity costs (just a guess though, no calculations thrown at it). A quick search shows that the range doesn't change at all for the 3 of them. Can you explain that to me? I don't understand how they have the same battery pack, the same range, but the AWD is using more power. 

 

Ultimately though for the Tesla, it comes down to do you want crazy supercar performance for more money, or just normal supercar performance for less money. Obviously wiht the driving dynamic differences of AWD and RWD involved as well.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
11/21/19 2:33 p.m.

According to the wiki article on the Model 3, the range does vary depending on which measuring system you use. The EPA combined rating is almost identical even though the RWD version did better on both city and highway EPA ratings. The WLTP and NEDC show a much bigger difference. I can't explain, which is why I decided to quote the efficiency instead of range. The "long range" RWD is actually no longer available but I used it because it was the closest comparison to the AWD cars.

We went with the AWD dual motor Tesla because of traction - when you're crossing the 10,000' Red Mountain pass in January, that's a legitimate concern.

captdownshift
captdownshift GRM+ Memberand UltimaDork
11/21/19 6:18 p.m.
Keith Tanner said:

...it also means RWD doesn’t carry a packaging penalty, so it’s a more viable option for companies that prioritize handling. 

All three of them. 

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