Alusil and cold weather

[Usaguy]

ran across this article that says: "What can be done to protect your engine from Alusil bunching? Optimally, limiting cold starting at extreme temperatures to a minimum is ideal"

link:

Cold Weather Car Problems : Mercedes Benz engine failure - Car Repair, & Performance | Fluid MotorUnion | 2108 W. Ferry Rd. Unit 102 Naperville, IL

Is it true that alusil blocks don't like extreme cold temperatures?

also they made a mistake in the article saying that alusil is a coating where in fact the entire block is made out of it.

[97 SL320]

Have a look on Porsche boards as they have this type of cylinder.

I didn't read the thread to see if " Alusil bunching " is covered.
Re-ring Alusils? - Page 29 - Pelican Parts Forums

With the car in your link, my money is on this car had frequent cold start then immediate foot to floor on the freeway cycles through the winter. If an engine is brought up to full power from a cold start, piston expansion rate will exceed that of the cylinder and clearances will get very tight causing this scuffing.

[oldsinner111]

one reason,I shy away from aluminum blocks.

[Usaguy]

I think there could be some truth to the fact that alusil engines dont like cold weather and if you own one you should let it warm up a little bit in the winter.

looked into the service manual for 450SL (Iron block) and 560SL (Alusil block) and here's what I found:


Piston clearance:


450SL: 0.020-0.030
560SL: 0.008-0.018


Ring gap:


450SL: 0.25/0.35 - 0.40/0.55
560SL: 0.20 - 0.35


Clearances are tighter on alusil engines and I think that's because the block expands more

[97 SL320]

An aluminum piston in an iron block will have decreasing piston clearance as things warm up due to aluminum expanding at a greater rate than iron.

An aluminum piston in an aluminum block will have piston clearance more or less constant.

The qualifier for either engine is if the engine is run hard from cold , the piston will heat up much faster and expand much greater than the block causing a temporary decreased clearance and possible scuffing.