Why the Engine Coatings at all? Nikasil, Sumabore, etc

So I've been stydying up on the BoreScoring and other problems and You can't study that without learing about the engine coatings. It just occured to me, why the coatings at all? I've been a motorhead most of my life and I've never really heard much of engine coatings until I got into the Porsche World. Maybe I'm completely wrong, but does anyone other than European Manufacturers coat their engines in something? Domestic Auto Manufacturers. What would happen without the coatings? As far as I know Corvetts and Mustangs, Vipers and GTRs have very descent engtines without coatngs. Or do they have coatings.

I think the answe is that aluminum is soft and needs a coating. But better qualified folks can answer the question.

reduce friction, ie wear and help promote longevity. Some coatings, as we know, can have issues from enriched fueling.

I had my engine coated with Nikasil by Millennial Tech. I did a lot research both online and talking to Millennial Tech. Go to their website and check it out. I live by the statement '" don't believe anything you hear and only half of what you see ". The coating is 10 times more wear resistant. MT does many different vehicle ( Automobile-Track cars, Motor cycle, snow mobiles, etc.

I'm sure it's never a single reason for why coating are used. The type of metal the engine is made from, tolerances, wear resistance, longevity (especially under hard operating conditions), friction, overall engine characteristics (compression, rpm range etc) all probably play into the equation.

Aluminum is so soft you can cut it with a sharp knife. An uncoated aluminum cylinder would wear out in a couple minutes. Coating the aluminum with a hard material prolongs the service life - if done properly with the correct materials. In fact coating a steel cylinder with hard material prolongs the service life as well. It's a big thing in piston engine aviation, where the engines can sit around for long times and have very high rebuild costs.

the EPA push for lower emissions is the driving force:::MFG's have no choice but to make changes or pay penalties... Up untill the late 1960's most all MFG's used gray cast iron for cylinders, some like Bridgestone motorcycles used Chrome plating for high performance/low friction, but was very uncommon...Gray Cast Iron would last 90K -100K but was then worn so bad you had to use a "ridge-reamer" to cut the lip from the top of the cylinders just to get the pistons out.. In the 1970's Government Motors used Reynolds 390 ( aka Alusil) cylinders in the Vega and was a huge failure... By the late 80's Nodular Iron was being used by most MFG's and would have hardly no detectable wear at 100k, and would go 200k-300k...but the EPA was still pushing and threatening penalties Porsche used Aluminum-Silicone and Nickle-Silicone cylinders as well as many other MFG's to get lower blow-by , lower friction,lower emissions, higher efficiency......the good news is all this ALSO equates to more horsepower !! CGI (Compact Graphite Iron) , Somebore, and Plasma-Spray techniques are some of the newest cylinder treatments, to try to squeeze a little more out of the ICE...

What @Porschetech3 said. And performance as well. I owned a BMW Z4 with an N52 engine, and a BMW Z4 with an S54 engine, both at the same time. The S54 has a cast iron block, the N52 has a magnesium alloy block. That made a 200 pound difference in the weight of the car, all of it in the front end. The N52 car felt so much different because of it.

Interesting list of Audi, Mercedes, BMW and Porsche engines using Alusil. https://en.m.wikipedia.org/wiki/Alusil

I'M 60... I've been fixing bore scored engines since I was about 15.. This is far from a new thing, it just happens to get your attention when its a 25K+ bill ... All the old 2 strokes, Boat motors, and it didn't matter whether it was Aluminum or a steel sleeve, Over fueling will KILL the bore of any engine.. I rebuilt a Jag XKE V12 motor for my High school English teacher in 1978 main issue was the Webbers we're worked on by a guy who should not have touched them.. The piston skirts and bores looked pretty much like what you see in a 996 or a Subaru. Luckily I lived in a town with a small steel mill that built logging equipment, had access to guys who knew stuff..