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[mr singh]

a stone chip can happen at any time BUT if a vehicle isnt driven and kept in a garage the glass will hold up, however even at idle the engine is moving, and as a result the failure point will come under stress more often than a stationary piece of glass

[Problemchild]

stationary doesn't matter as its the growing and shrinking of the glass with temp changes

if all parts broke within months through material flaws then quality control would have to be so very high that parts would cost far too much. they are engineered to cope for a long time.

some examples from my work

gas turbine fan blades - all flaws have to be removed due to forces involved. The level of NDT and quality needed means 1 single ring of low pressure blades on 1 typhoon costs £1M. High pressure high temp blades are "grown" from a single crystal to have ZERO flaws.

body armour - the structure make up of the ceramics is essential for ballistic protection. small flaws can propagate over time reducing the effectiveness and until synthetic biology comes into play and we can shape the material structure (i'm talking the material/molecular structure) to remove these flaws. Millions of £.

I doubt whoever make the con rods in 40yr old mitsubishi engines or pattern parts for suspension components put huge amounts of efforts into making the metals free from flaws.

3000 revs per min means the piston goes up 3000 and down 3000 times per min.
6000 changes in direction per min.
60 miles @ 60mph = 1hr of running per 60 miles.
60x6000 = 360,000 changes in direction per 60 miles.

say car has done 60,000 miles  thats 360 million changes in direction in that time.

thats gonna start impacting on even the smallest flaw

(sorry if my maths is awful haha)

JJ

[steddie eddie]

JJ, i think its very interesting and a bit of an eyeopener about how often the crankshaft goes around and pistons go up and down.
Greetings,
Eddie.

[mr singh]

iv worked for Jaguar near enough 14 years (minus 4 months spent at Volvo) and in that time i personally have replaced just 3 engines. 1 was on an x-type where it blew a turbo, and the other 2 were on new XE's with less than 7000 miles on the clock, the 2nd XE had only 34 miles before the engine seized.

i have seen about 4 engines replaced by others, and one of the old boys that i worked with did say 'if anything is going to fail, it will be within the first year the car is on the road'

if your car hasnt been modified to produce more power than the engine components can cope with, the engine will last forever, given if its been looked after correctly and fluids changed regularly.
yes the manufacture says this engine produces 100 BHP but the components could and will cope with up to 170 bhp.
take the Jaguar AJV8 gen 3 engine, supercharged version produces 500 BHP in the XFR but look towards the F-Type SVR and its 570 BHP, and look even further at the up coming XE SVR that figure is closer to 600 BHP.

i appreciate your line of work works with VERY high stresses but they all for the jobs they are designed for, but car engines are put under no where near the stressed of aircraft and body armour armoured vehicles

[Problemchild]

And the turbo failure was because of the owner?

I agree that faults with manufacture or assembly can and probably often can fail early in their life.

BUT the life of a car is long and stressful. You can’t blame all failures on people. You said it yourself, cars aren’t put under the same stresses so the quality of parts are lower also.

Parts can and do fail

JJ

[mr singh]

the turbo failed because one of the oil seals had poped, the car was under warranty then.

parts can and do fail, but if an engine has done 100,000 miles trouble free then it will go another 100,000 miles trouble free IF its cared for correctly.

if its neglected like the engine in question, then obviously its going to fail.

[Brabs]

IMHO one of the most likely reasons a turbo fails is because the oil isn’t changed regularly and not using a good quality synthetic. Also not allowing the turbo to cool... idle the engine for a for a while after being under high speed use. Cam chains also need regular oil changes and a good quality synthetic oil. Regular maintenance is king! A trusted mechanic friend of mine says that extended service intervals of for example 20,000 miles are a cost cutting bad idea. He had a MINI come into his shop that had the spark plugs impossible to remove (using normal tools/methods) because they hadn’t been removed in 4 years/20,000 miles. Had to remove the head and use some unconventional methods!! 

[cecil]

If someone wants to pop in the correct values for our cars to find out the forces in a piston engine here is a fill in. http://www.cargister.com/piston-calculation
The acceleration and thus forces  involved in movements can get large very quickly. As they found out, with the airliner Comets ,fatigue in metals can have catastrophic effects.  Even when the forces are well within those that the metal should have been able to have taken. The more you find out the more amazed you get that everything holds together for so long!

[Problemchild]

yeah the dH comets would snap in half due to stress fractures after around 3000 flights due to constant pressurisation and depressurisation

at least we now all have round windows in planes

JJ