If it\’s got an engine. . .

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Archive for the ‘Engineering’ Category

Engineering Overkill part 2: BMW door locks

Posted by ifitsgotanengine on October 2, 2006


What can be improved on typical car door locks? After all, all they have to do is lock and unlock the car, either with a key, lock button, or remote.

Let’s look at the E32 BMW door locks and see what they added. Remember, these cars first came out in 1988.


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  • The doors can be locked and deadlocked. When deadlocked, they will not open from inside. This prevents a thief from prying the window open enough to get a slim jim in and pull the lock knob. The lock knob and all rods internal to the door are physically prevented from moving. This also prevents anyone not familiar with the system from unlocking the door, even with the key, as unlocking a deadlocked door requires turning the key in the unlock direction, lifting the handle, then turning the key farther.
  • Heated door locks. If the temperature is below 38 F and you lift up on the outside door handle with the car locked, a heater in the lock energizes for 30 seconds to melt any ice from the lock.
  • Inertia switch. If the car undergoes a shock of approximately 5g’s, all doors automatically unlock, and the hazard lights turn on. This allows rescue teams to more easily locate a wrecked car and gain entry.

Posted in BMW, Engineering | 8 Comments »

Why do I love my BMW? Engineering overkill.

Posted by ifitsgotanengine on October 2, 2006

The picture to the right is a diagram of the E32 (1988-1994 7-series) BMWs’ windshield wiper assembly. What is not immediately apparent from this diagram is the level of attention given to the engineering of this seemingly mundane system.

To wit:

  • When in slow speed, the wipers will switch to delay mode when the car is stopped, picking back up again when the car starts moving.
  • The intermittent delay will vary with car speed, or can be user-programmed for any time interval from two to twenty seconds.
  • The windshield has heating coils built into its base which prevent the wipers from freezing to the it. These automatically power up whenever outside temperature reaches 38° F.
  • My favorite – Part #4 on the diagram above is a “pressure adjusting device”. It varies the wipers’ pressure against the windshield with the car’s speed, preventing the wipers from lifting or chattering at high speed.


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Perhaps the best thing about the wipers is that they just work. Probably 99% of the owners of these cars don’t know about any of the items above.

That is the mark of engineering excellence.

Posted in BMW, Engineering | 3 Comments »

Maximum Efficiency

Posted by ifitsgotanengine on September 12, 2006


It seems to me that the best engine from an efficiency standpoint is a single-cylinder engine. Practical experience bears this out – my Suzuki Savage 650 (single cylinder) got 70 mpg, while my Yamaha Maxim 650 (four cylinder) gets 48. Less moving parts mean less friction. less friction means more of the energy in that gallon of gas goes to moving the car down the road.

Less moving parts also means less parts to break.

Why do we not see three-liter singles in family sedans? Or five-liter singles in sports cars?

If you know anything about engines, you already know the answer to this. A large single-cylinder engine would vibrate so badly that it would shake the car apart.

What I propose is a hybrid single-cylinder engine. Couple a large single-cylinder engine up to an electric motor/generator. The electronics controlling the motor/generator would have to be fast enough to switch from motoring to generating every other engine revolution.

When the engine is on its power stroke, the motor/generator is acting as a generator, charging a capacitor (think really fast battery). On the other three strokes, the motor/generator is acting as a motor, since the engine isn’t doing anything productive.

The hybrid motor/generator isn’t there to improve efficiency through regenerative braking, as in other hybrids, it’s just there to smooth out the big single’s power pulses, allowing it to be used in civilized transportation.

Posted in Efficiency, Engineering | 4 Comments »

Sealed for life

Posted by ifitsgotanengine on August 11, 2006


How long does the average American who purchases a new car expect it to last before it needs major service?

100,000 miles? 150,000 miles?

I would be seriously upset if any NEW car that I purchased ended up in the shop with less than 100k on the clock.


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Why then do most domestic automakers continue to offer only three years or 36,000 miles for their warranty period?

On a semi-related note, my wife’s 1998 Audi A4 needs another wheel bearing replaced (this is the second one I’ve had to replace). It has 162,000 miles on it. The first bearing went out at 155,000 miles.

Years ago you could repack wheel bearings with grease. Actually, you had to – if you wanted them to last more than 25,000 miles or so. But if you kept fresh grease in them, they would last forever.

The automakers got tired of honoring warranty claims for worn out bearings with mysteriously fresh grease and started using the “sealed for life” bearings. Sealed “for the life of the bearing” is more like it. Nothing you can do will extend the life of these bearings, but they WILL outlast the warranty.

Posted in Audi, Engineering | Leave a Comment »