A warning to SuperTurbo modders about rings
A warning to SuperTurbo modders about rings
I see the same thing over and over on the turbo models. The upper rings almost always have chipped contact surfaces that originate from the bottom of the ring.
If its not all the way around the circumference of the ring, its in one localized spot.
My theory:
First owner breaks in car and drives a particular way. Sells by 150k miles to second owner. Car is still in good condition and 2nd owner treats as such. 15 years after original purchase, car is a bit beaten and is sold to someone who drives much more 'spirited' than the first 2. The engine has 200k miles on it.
The upper cylinder taper has been created and there is a pretty decent ridge there now. Any heavy driving causes the pistons to heat up and expand. Thus, the upper ring is smashed against the ridge and the ring land on the piston.
With nowhere to go, it chips.
totaldisaster
05-09-2011, 05:36 PM #1I have opened at least 10 of these engines; turbo and NA.
I see the same thing over and over on the turbo models. The upper rings almost always have chipped contact surfaces that originate from the bottom of the ring.
If its not all the way around the circumference of the ring, its in one localized spot.
My theory:
First owner breaks in car and drives a particular way. Sells by 150k miles to second owner. Car is still in good condition and 2nd owner treats as such. 15 years after original purchase, car is a bit beaten and is sold to someone who drives much more 'spirited' than the first 2. The engine has 200k miles on it.
The upper cylinder taper has been created and there is a pretty decent ridge there now. Any heavy driving causes the pistons to heat up and expand. Thus, the upper ring is smashed against the ridge and the ring land on the piston.
With nowhere to go, it chips.
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
willbhere4u
05-09-2011, 05:40 PM #2The rod bearings loosen up over time as well
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
That usually not the problem. They are most often re-usable if the engine was maintained. Wrist pins wear out before them (more heat, less oil supply).
But, assuming that both were worn out (pins and bearings), that would help prevent the rings from being smashed against the ridge.
The piston would sit lower in the cylinder due to wear, and the force from the compressed air in the combustion chamber keeps the piston low.
totaldisaster
05-09-2011, 05:47 PM #3"The rod bearings loosen up over time as well"
That usually not the problem. They are most often re-usable if the engine was maintained. Wrist pins wear out before them (more heat, less oil supply).
But, assuming that both were worn out (pins and bearings), that would help prevent the rings from being smashed against the ridge.
The piston would sit lower in the cylinder due to wear, and the force from the compressed air in the combustion chamber keeps the piston low.
(05-09-2011, 06:09 PM)DeliveryValve Pictures please!
What? You don't believe me?
I may be wrong, it could just be fatigue as I have found the chips also on the second rings. But they are much more prevalent on the top ring
I suppose its possible as the ring wears, on the bottom primarily, the outer layer flakes off due to the angle of 'twist' by the ring.
The rings get sloppy and find more freedom in between the lands then start making contact on different locations than where they have 'set'.
The ridge theory is debatable. But this failure is not.
totaldisaster
05-10-2011, 12:24 AM #5(05-09-2011, 06:09 PM)DeliveryValve Pictures please!
What? You don't believe me?
I may be wrong, it could just be fatigue as I have found the chips also on the second rings. But they are much more prevalent on the top ring
I suppose its possible as the ring wears, on the bottom primarily, the outer layer flakes off due to the angle of 'twist' by the ring.
The rings get sloppy and find more freedom in between the lands then start making contact on different locations than where they have 'set'.
The ridge theory is debatable. But this failure is not.
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