June 2021 – The Quarky Engineer

The temperature differential with altitude is more than I would have expected. I have been out a few times today driving down to near 0 ASL, and driving back up to my house the drop has been >= 6 degrees.

Right now at 217 and 26 it is 102F, and here outside at my house it is 96F

The 96F degree temps have not really been that taxing for my climate control, as the inside temp is a steady 71 degrees, and the main floor heat pump has only gone to stage 5 a few times. Air temp coming out of the vents has been pretty stable at 51-53F degrees.

My house has a lot of heat load from both the color as well as the number of windows, so this is an interesting test of the total system capacity.

The server room AC hasn’t changed its pattern that much. It is running at around 600watts most of the time, and that room temp is usually right around 68-70 degrees, with 5-6kW of equipment running. It is interesting that I’m only using 600 watts of cooling, but heat pumps have greater than 1:1 CoP, and that room is buried and surrounded by concrete and then earth.

Tree

June 24, 2021 Jeff

What a fantastic day.

Plaid Data

June 17, 2021 Jeff

Interesting to see the Motortrend test of the Tesla Model S Plaid:

https://www.motortrend.com/cars/tesla/model-s/2021/2022-tesla-model-s-plaid-first-test-review/

On a prepped surface:
0-60: 1.98 seconds (with rollout of course)
1/4: 9.25 @152mph

On a non prepped surface:
0-60: 2.07 second (with rollout of course)
0-60: 2.28 second (without rollout)
1/4: 9.34@152mph

60-130: 4.7 s

Some interesting quotes:

“The Plaid covers distance so quickly, it’s difficult to even register what’s happening. The yoke gets light in your hands, your neck muscles strain as your helmeted head digs into the headrest, and your surroundings blur into mere shapes and colors as a quarter mile of pavement vanishes underneath you.”

“Even more impressive and true to Tesla’s word, the Plaid is capable of posting those times consistently, never varying by more than a fraction of a second or so each time we rocketed down the strip. We’ve never tested a car so robotic in its consistency.”

“Amusingly, the Plaid launches so ferociously hard, it generates more than 1.00 g from 0.2 second to 2.6 seconds after launch, peaking at 1.227 g at 32 mph. That’s more g than the car generated in its best 60-0-mph stop, which required 104 feet and peaked at 1.221 g.”

“Not content with shattering our 0-60 and quarter-mile records, the Model S Plaid claimed yet another one: Its blistering 0-100-0-mph result was 8.2 seconds, besting the previous record holder, the McLaren Senna, by 0.3 second.”

X5 Charge

June 13, 2021 Jeff

Kristin drives a 2021 BMW X5 45e, which is a plug in hybrid. It has a small battery (24kWh) that can give you about 35 miles of range before needing the engine. The car has a 290hp turbo straight six, plus a 111hp electric motor, so it feels snappy. 443lb-ft of torque too.

I just checked and for the first 6120 miles she used all electric 4353 miles, which is pretty good given we have done a few road trips in that car that were certainly almost all gas.

On a full tank you can get almost 500 miles of range, yet for most in town driving you can be all electric.

All in a pretty neat car…. of course you would not want to own this car out of warranty, but that is a given for modern BMWs anyways.

Plaid HP

June 11, 2021 Jeff

Last night Tesla displayed a graph of HP for the Plaid model S. I took a shot at converting that data into the equivalent engine torque you would need in an internal combustion engine, assuming a Nissan GTR drivetrain. The idea is to see what engine torque you would need to produce to make the same to the ground horsepower of the Tesla. This doesn’t take into account the cars mass and how that effects acceleration… but it is a very interesting look.

A couple of observations – 1st gear torque requirements are quite different from the other gears because the power output shown on the Tesla graph are much lower at low speeds…. none the less you would still need 570 lb-ft of torque at 1800 rpm to match it. That is part of the reason for the excellent 0-60 times.

I modeled this shifting the ICE at 7500 RPM, so the upper gears are only represented in that range. Once in 2nd gear you are looking at 900 lb-ft, falling down to 700 at redline. 3rd through 6th are all very similar with exception of the spike needed going into third of over 1000 lb-ft.

You can see the falloff of torque at higher RPMs, which is obvious from the flat HP curve. Still, it represents a very good combination of low end torque and high end power. This also assumes zero shift time, so there would be some slight loss there.

The engine torque is as measured and down converted at the wheels, but that assumption is mostly because the Tesla ‘drivetrain’ has very very little loss owing to no transmission.