Physics & Fast Cars #001 -- The Real Reason Toyota Chose the Name "MR2"

"way2blu does a rev update" (way2blu) 01/29/2018 at 10:10 • Filed to: Physics & Fast Cars, Toyota MR2, Polar Moment of Inertia, Physics, Science

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Many of us have been raised to think “MR2" stands for “Mid-Engine, RWD, 2-Seater” or “Midship-Runabout-2-Seater.” In my research, I’ve discovered the truth. I’m here to explain the truth behind the name “MR2" using physics!

With its mid-engine configuration, the MR2 has a much better moment of inertia than most other cars.

In physics, moment of inertia is, according to Wikipedia:

The moment of inertia , otherwise known as the angular mass or rotational inertia , of a !!!error: Indecipherable SUB-paragraph formatting!!! is a !!!error: Indecipherable SUB-paragraph formatting!!! that determines the !!!error: Indecipherable SUB-paragraph formatting!!! needed for a desired !!!error: Indecipherable SUB-paragraph formatting!!! about a rotational axis. It depends on the body’s mass distribution and the axis chosen, with larger moments requiring more torque to change the body’s rotation. 

Which is, in essence, the car’s willingness to rotate. It makes the car very capable in the handling department, but this willingness to rotate can be dangerous. It’s partially to blame for the snap-oversteer inherent in the handling of early-model MR2s.

So, with the heavy mass of the engine moved closer to the center of mass of the car (the point about which the car rotates, in this case) a smaller moment of inertia is achieved. The handling benefits are obvious.

As any dedicated car owner would, I set out to calculate the exact moment of inertia (in kg*m^2 or lb*ft^2 ) of my car.

As I refreshed my memory on the formulas, something stood out:

Physics equations via GSU.edu

What???

Allow me to highlight the key expression here: MR^2 . Sound familiar?

Could it be a coincidence that this car, built to minimize moment of inertia, has a name that shows up in a majority of moment of inertia calculations??

To the car-buying audience, “Mid-engine, RWD 2-seater” kind of makes sense. In my opinion, it was never the most elegant name for a sportscar.

But from the standpoint of physics, this name is amazingly obvious, and even more amazingly nerdy. It gives me heart that somebody at Toyota had the idea to name the car after a physics expression, of all things.

HondoyotaE38: A Japanese and German Collab...wait a minute > way2blu does a rev update 01/29/2018 at 10:14

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Illuminati confirmed

themanwithsauce - has as many vehicles as job titles > way2blu does a rev update 01/29/2018 at 10:16

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NNNNNEEEEEEEERRRRRRDDDDDDDD

Maxima Speed > way2blu does a rev update 01/29/2018 at 10:38

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Question, I’ve been recently changing my mind on what sports car I want. I’m not sure about the BRZ and I’ve been leaning towards an MR2 of the same generation as yours. I was wondering what recommendations you could give for it. I was never really a fan but then I saw a white one in person for the first time and was blown away by the looks. Did some research and it’s seems like the light weight, perky, sports car I want (and its Toyota).

Scouting For Zen > themanwithsauce - has as many vehicles as job titles 01/29/2018 at 10:40

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Ash78, voting early and often > way2blu does a rev update 01/29/2018 at 10:44

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I think it’s because Mr. Two in Japanese is roughly “Ni-san” and the car was secretly built by Nissan.

Case closed.

elevenafter9 > Maxima Speed 01/29/2018 at 14:12

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I have a 1991 naturally aspirated MR2. It’s a good car, it has the Toyota reliability in spades (it has always started right up every time for me, no matter how long it has been since I last started it, battery issues notwithstanding).

That being said, I wouldn’t call the car perky, unfortunately. Mine is obviously the slow version, and the one turbo that I’ve ridden in was a rocket (it had some engine work done to it as well), but I’d still categorize the MR2 as a bit soft around the edges. It doesn’t have the peppiness that I was hoping for; every Honda I’ve ever driven has that peppy characteristic and I was really hoping for that in the MR2, but it’s not there in my experience.

That being said, it is a fun car and handles itself quite well on the track. It’s also a looker for sure.

way2blu does a rev update > Maxima Speed 01/29/2018 at 16:30

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MR2s of the SW20/21 generation (20 is the Turbo, 21 is the NA) are a blast.

They weigh about as much as a BRZ but, in my experience, are actually much more practical. The big trunk behind the engine swallows everything I could possibly need to carry.

Even the non-Turbo SW21s like mine actually have more low-end toque out of the 2.2l 5S-FE Camry engine than the BRZ out of its flat-4. Peak hp in the MR2 is only 135 but it pulls much more consistently and has almost as much torque at 3500 as the BRZ makes at 7000. This is the base MR2.

Turbo models can be built up to ~350hp on stock internals and run very reliably even at that output. Obviously, that’ll leave the BRZ far behind.

Unfortunately, it’s hard to find good, stock examples for reasonable prices. Many are modified, but to varying degrees. I compromised on mine and bought one that was in poor condition, but still stock:

Investing a few grand in repairs was well worth it though, and now it looks like this:

I’d recommend searching very carefully and being patient. I took a few months before I found mine. Craigslist is your best bet, definitely post local ones to Oppo if you want NPoCP feedback :D

Maxima Speed > way2blu does a rev update 01/29/2018 at 18:47

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Sounds good, thanks is for advice. I’m hoping to buy one sometime next year. I’ll definitely ask Oppo about listings before I give them a try.

Maxima Speed > elevenafter9 01/29/2018 at 18:48

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Thanks, man. I would really like to give the turbo and nonturbo a try.