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Posted by David Sherman [24.32.202.83] on Monday, February 01, 2010 at 23:09:44 :
In Reply to: Re: Toyota Recall story posted by michael hernke [75.204.2.55] on Monday, February 01, 2010 at 22:05:56 :
The rule of thumb in vehicle design is that the brakes can dissipate 10 times the HP of the engine, at least for a brief time. Hence, stopping distance from any given speed is roughly 1/10 of accelerating distance to that speed. Obviously high-performance cars accelerate faster, but that's the rule of thumb.
Thus, brakes can out-power the engine for a short time. The key in using the brakes to stop a vehicle with a racing engine is to apply them hard and bring the vehicle to a stop as quickly as possible. Obviously if you ride them long enough, they'll overheat and then you're SOL. Also, I'm wondering why these drive-by-wire systems don't cut the fuel when the key is turned off. Or are the drivers so dumb these days that they don't even try that? If a driver won't turn off the switch, and won't apply the brakes (or do they have brake-by-wire nowadays too?), I'm not sure how much more Toyota can do to hold their hand.
When I was a kid, my dad had a runaway situation with his '60 T-bird (the "old car" that I was supposed to get when I got old enough to drive, but that's another story). The throttle stuck at freeway speed and he didn't realize it until he was on the off-ramp at 70 mph with a stop light and busy street 100 yards ahead. He turned off the ignition, but the V8 kept running, which a gas engine will do if the RPMs are high enough. He knew if he took it out of gear it would blow up or at least throw a rod. All he could do was brake hard and hope the brakes held. It had an automatic tranny so it was hard to say whether slowing the car would slow the engine enough, but fortunately the brakes and tranny held and once the RPMs got reduced enough, the engine quit due to no spark. I suppose most drivers nowadays would just freak out, crash through a bunch of traffic, kill or maim themselves and half a dozen other people, and the lawyers for the survivors would win a huge settlement from Ford. Of course most drivers nowadays didn't do a full combat tour navigating B17s over Nazi Germany, where freaking out doesn't get you back to England alive.
Our failure ana.lysis showed that the stuck throttle was caused by a pack rat. He had smelled wood smoke briefly during his drive on the freeway, but assumed it was from someone burning a fire nearby. The car didn't get driven regularly, and we had removed pack rat nests and seed caches from the exhaust manifold several times. The throttle cable tube was lined with plastic, which was melted. His theory was that the heat of the exhaust manifold ignited the pack rat nest, causing the wood smoke smell and heating the plastic around the throttle cable. Since he was cruising at a steady speed on the freeway, the fire burned itself out and the plastic congealed with the cable in the "open" position. That might be the only time in the history of automobile that a pack rat caused a stuck throttle, but it came very close to making my mother a widow.