Saturday, March 18, 2000BY ALAN VONDERHAAR
The Cincinnati Enquirer
Dear Al:
I recently saw a 2000 Toyota Avalon that had been dropped rear first off of a transport truck.
The car was demolished, but I noticed that the air bags did not deploy. My question is, do the air bags only deploy when the vehicle is hit head on or do they only deploy when the ignition is on?
Al E.
via the Internet
Dear Al:
Enquiring minds also want to know where "factory executive" cars come from, . . . but that's another, perhaps related, story . . .
I put your question to a Chrysler platform engineer. He told me the frontal air bags are controlled by a solid-state sensor that is extremely discriminatory - i.e., it "knows" that it should not send a triggering signal to the bags unless the impact comes from directly in front of the car, or at most, 25 degrees to the right or left of front center, and at speeds of more than 25 mph.
He said you could be sitting there idling and get hit from the rear by a semi doing 70 mph and the air bags would not deploy, although there would be quite a bit of commotion.
If the ignition is turned off, the bags are inoperative.
Dear Al:
A few years ago I heard that supercharged engines had problems lubricating the supercharger motor. Do the '99 and '00 cars still have this problem?
Earl H.
Bevis
Dear Earl:
There may be a bit of confusion here.
A supercharger is a belt-driven external air pump designed to force a larger-than-normal fuel-air charge into the cylinders, thereby producing more power.
It is not to be confused with a turbocharger, which is a set of turbine wheels on a shaft, located much closer to the action. One wheel is placed in the exhaust stream, where hot gasses turn it as they leave the engine. Its coaxial partner is located in the intake passage, and so, as the exhaust wheel turns ever faster as the driver "gives her the gun," so does its bud, cramming even more air into the engine. This is what's known as a closed feedback loop and would soon blow the engine apart unless damped mechanically or electronically.
At full boost, the little turbines can be turning at 100,000 rpm or more. That alone would generate some heat on the shaft bearings, to say nothing of the 1,500 degrees or so of the exhaust stream.
In the earliest days of the turbo, not enough attention was paid to cooling the turbo's bearings, so that if a driver did a hot run and immediately shut down the engine, heat from the exhaust side would build up and turn the oil on the bearings to carbon, with an expectedly dire effect on longevity.
Never mind that many manufacturers warned against treating a turbocharged engine that way; in their naievete, they buried the warning in the owner's manual, which may get less attention than a Gideon Bible. Early failures were common.
Then the makers got smart and provided better cooling - and motor oils improved apace - and the turbo became a respectable member of society once again.
The supercharger per se does not share this problem, though it is worth noting that in doing its job, it imposes greater-than-normal thermal loads on the engine. Accordingly, some manufacturers recommend more frequent oil changes, and a lot of cognoscenti advocate synthetic oil, known for its better heat resistance.
From what factory people tell me about warranty claims, and from following the yak on Internet newsgroups, I've concluded that neither turbos nor superchargers are particularly troublesome these days.
Alan Vonderhaar welcomes email at avonderhaar@enquirer.com and snail mail c/o The Cincinnati Enquirer, 312 Elm St., Cincinnati OH 45202.