Ronan

I just came across a thread that does a superb and complete explanation of bore scoring and the engines it affects:

https://www.pistonheads.com/gassing/...0&f=&t=1752333

seanseidman

that is helpful, thanks for posting

Bacura

Interesting read. Does this bore scoring only happen to either very high mileage or track driven cars? Would a low/medium mileage car that isn't taken to the track also suffer from this?

jumper5836

Happens to all I think mileage plays a part. I believe there are many variables to it. oil thinness, broken down or contaminated, cold start temps, high heat stress due to lack of cooling on bank 2 like after a track session or could be just from a very hot day and caught in stop and go traffic.
Also depends on if you have early Lokasil, the later Lokasil mix with iron piston coating or the later the Loasil mix or the Alusil with plastic coated pistons. For the 9A1 the post refers to shrinking bore clearances at the bottom of the cylinder. This seems to be like a completely different problem with some similar to the ovality problem but not entirely the same. Alusil is the strongest of all liners with exception to a nikasil coated liner and I would think they have gotten rid of the plastic piston coating it would be the least resistant to all of the issues that cause scoring/scuffing.

There was just a post about scored 991 GT3 makes we wonder if the 991 GT3 even have nikasil coated cyliners now or they are now all just alusil. Thinking the would explain it if they are just alusil.

boman993

Out of 4 of the Canadian 997.1s I PPI'd in the last half year, 3 of them had evidence of bore scoring. One of those 3 was already on its second engine from Porsche due to scoring issues in the past. Mileage varied and so did condition.

Charles Navarro

The piston to cylinder clearance on a stock MA1 9A1 DFI engine is .0008". Needless to say, that's why I would expect colder climates or cars driven in colder weather would be susceptible to scoring more than warm climate cars. Piston squirters can only do so much.

Bacura

Then I am glad my car is 100% garaged with no very cold starts. The 997.1 was prone to scoring. I asked my service guy if they are seeing this in the 9A1 engines and he said no. He could be lying. I guess time will tell.

cartwheel

Having witnessed far too many people jazzing cold engines I don't have any surprise that modern tight tolerance engines develop these issues. I used to work with a guy who drove a lexus and he would redline the thing leaving the parking lot at the end of the day regularly. It can't be all operator error but it would only take once...

Johnny DB

Were you involved with these 4 PPIs?

theiceman

I thought this was prevalent on cayennes also !
If so that would eliminate the " track talk"

Charles Navarro

The majority of Cayenne V8 engines we see are from Canada, but I have a Panamera V8 as well from the south that I'm pretty sure never saw any really cold starts. All these engines utilize the same bore technology with an Alusil bore (or in the case of the M96/M97 Lokasil) and a high silicon content piston with ferrostan coating (Mahle's iron skirt coating) to prevent aluminum on aluminum contact and galling (scoring).

jmh981

So is this happening with other manufacturers or has Porsche somehow forgotten how to make a durable motor? Jeez, the basic technology is a hundred years old - you would think they would have perfected it by now.

theiceman

they did ..... then went water cooled ...

boman993

Not sure what you mean. But, I paid to have Porsche shops borescope the 4,5+6 bank along with a regular PPI when I was shopping for my car over the last year. PCO did one for me back in November on an 07 C4S I was very interested in. That was the last .1 I had PPI'd before changing my mind and holding off a bit to get into a .2 .

Charles Navarro

It happens with other manufacturers. Alusil and Lokasil are common in BMW and Mercedes and they too suffer scored bores if you search. Problem, is you don't see it as often as you don't have such an enthusiast driven market as you do with Porsche owners.