Quote:
Originally Posted by ttoyoda
The crankshaft and connecting rod bearings in the engine are just plain bearings. They have no balls or rollers, just a thin metal shell insert with an oil groove which "rubs" against the crankshaft.
Lots of pics, here, look at the half-circle sheet metal looking things.
http://images.google.com/images?hl=e...h+Images&gbv=1
You know how your car tires will hydroplane when you go fast enough thru deep enough water. The bearings work on this hydroplaning principle. If the rotational surface speed of the bearing is fast enough (fast enough engine rpm) the crankshaft will hydroplane up on the oil film and never touch the bearing shell when the engine is running.
Otherwise, it will rub and wear the bearing. You will not know it is wearing for a long time, and then it will be too late and you will hear knocking noises when the engine idles. This noise is caused by the clearance in the bearing getting bigger due to wearing away the bearing shell. At this point people put in thicker oil and sell the car.
I would suggest not using full throttle at very low rpms for this reason. You combine high bearing loads with low bearing surface speeds. |
I know this fact
I decided to risk it anyway - and would (and will) do it again.
I had a car with the same engine (but the non-turbo carb version), and managed to run it dry on oil a few times, including times where I would accelerate around a corner and the oil pressure light would come on, and other times (twice) where it would 'squeak' due to no oil (I topped it up at this point). This all happened due to a large oil leak it had. This car lasted from 150,000 up to 230,000 miles like this, then died due to an unrelated problem.
My last car (1.8 Turbo Bluebird) went from 120,000 to 176,000 miles, with a lot of that being extreme hypermiling. The car was almost certainly 'clocked' (and had been abused from some things I found). It was more worn than my 240,000 miles Bluebird mentioned above. I drove thousands of miles with repeated engine-off coasting, sometimes shutting off and restarting the engine a few times in each mile (as long as no-one was behind me), and dropping to 20mph before going into 5th gear and lugcelerating
up to 35mph before EOCing back down to 20mph. I had an oil pressure gauge which helped.
I think the important thing is that when I went back into 5th gear each time, I would bring the revs up with the ignition switched off so oil pressure came up. Also the engine was slightly lower compression than usual. Finally, by avoid actual 'lugging', the bearing loads were kept within reasonable limits.
With petrol prices as they are, my UK car was worth about 450 pounds, but petrol is probably about 65 pounds per tank now. So, the car is worth 6-7 tanks. Once I have hypermiled 12 tanks at 100% above EPA, then the car has paid for itself. I hypermiled so many tanks in that car that it paid for itself several times over.