racer5j

Anyone else find it interesting that the new 992 now uses iron cylinder liners in an aluminum block? I certainly remember taking a lot of heat for going with iron liners in my 4.2L M97, which was considered "a step backwards" in terms of innovation. Just saying.

"The primary motivational hardware—a twin-turbocharged 3.8-liter flat-six—remains largely unchanged with the exception of iron cylinder liners, cast-iron exhaust manifolds, and piezoelectric fuel injectors."

https://www.caranddriver.com/reviews...rototype-ride/

snaphappy

Does this mean they’re still wrestling with bore scoring? Or is there another reason for the change?

racer5j

Good questions that I'm sure no one outside of Porsche has the answer to. What is clear however is that a plated aluminum liner was not the answer.

doclouie

The only thing that jumps out at me is strength between the two. They are starting to put crazy pressure in the cylinders to keep bumping the horsepower with each new model. I am betting the aluminum just had to be too thick even with the coatings to be equal.

Fahrer

I had a 2008 BMW 535i. At that time BMW had a relatively new 3.0 they were using in their naturally aspirated 530 cars. But, for the new ( then in the 535) 3.0 twin turbo, they had to revert to the older 3.0 design and add irons cylinders to enable the engine to withstand the pressures.

Bruce In Philly

2009 C2S 148K miles

As I understood it, the whole reason for eliminating sleeves was to lower manufacturing costs.... not that iron sleeves are "bad". The way the non-sleeved process worked is that the block molds were doped with the sleeve material and the process of injecting the molds with aluminum, under very precise pressures and temps, caused the aluminum to react with the sleeve material to then form the Nikasil/Alusil or whatever-the-formulation sleeve. The casting of these blocks is not done by Porsche but by another specialty company that makes blocks for other car companies.

Back when Porsche started doing this for their newest, water-cooled engines, first installed in the '97 Boxster, the casting process had problems resulting in pourous blocks/sleeves. If a block failed a test at the Porsche factory, the block was then re-sleeved with an iron sleeve. The owner had no idea if the engine in his/her car had an iron sleeve or not. The consequence to this manufacturing problem is that not all pourous blocks were found and owners would have an engine failure from pourosity. For those with iron sleeves, some of the sleeves would slip and destroy the engine. Fortunatly, this failure mode was remedied early. I am not sure this was an issue in the 911 as they may have caught it by then.... not sure about this though.

BMW had the same issue at the time... same block maker... but backed their product by sending a letter to all owners that their engine warranties were extended to 100K miles. Back then, I wanted to buy an M3 but these new blocks were failing and BMW slowed importing them into the USA... this got me to look more seriously at Porsche and ultimately, I purchased a Boxster S in 2000.

Peace
Bruce in Philly

Balr14

Aluminum does not retain heat as much and has different expansion rates, than iron.

westlake10

I wouldn't be the least bit surprised if it was due to some environmental government regulation BS

Own Goal

Intresting. When I rebuilt the short block on my 951 (944 turbo) I went with iron sleeves. You can use the same pistons ( with proper clearance) but obviously different rings. I didn't use a deck plate however.

hexagone

I'm sure that there's a perfectly good engineering/cost/durability/quality rationale derived from hundreds of millions in R&D, hundreds of people and probably hundreds of thousand miles of R&D testing.

Any more armchair engineering speculation would be.... pointless.

workhurts

BMW’s issue on the S54 engines (some, not all, got the 100k warranty) was bearing clearances and maybe oil pressure issues. The cure was bearing replacement. Are there any other engines they gave a 6yr/100k warranty on?

Iceter

This could only be assumed if Porsche’s sole motivation was to build the best, most durable engines possible. We know from experience that that is not true, however, and that there are dozens of other considerations that drive corporate decision-making. Any combination of those considerations could push durability down the list.

Hypothesizing about why iron liners are being used is part of the fun. Don’t rain on the parade.

For my part, I like to go with the simple answers. Iron works. Other expensive, fancy, space-age stuff doesn’t always work. Therefore, iron.

Bruce In Philly

I am in error.... i could have sworn they had the same issue as they had (supposedly) the same block maker.... hmm... 20 year memory is failing, maybe I can get an extended warranty from my maker.. anywho.....I cut and pasted below the letter BMW sent to owners for the record. At a minimum, BMW had an issue and backed their product.

Peace
Bruce in Philly

http://m3forum.net/m3forum/showthread.php?t=4703

From 2002:

Dear Valued M Enthusiast,

We hope that you are continuing to enjoy your M car and that your BMW ownership experience is everything you hoped it would be. At BMW of North America we are committed to maintaining a level of automotive and service excellence that exceeds your expectations now and in the future. We are grateful to you for your passion and enthusiasm for M cars.

BMW has always maintained an open dialogue with our valued customers and BMW centers. As you may be aware, we have seen cases of damage to the connecting rod bearings resulting in engine failure. We are listening to your comments and concerns and have been meticulously researching this issue. We promise to keep you informed of any issues that affect your vehicle’s engine.

To further strengthen your confidence in your BMW and assure you of our commitment, we will extend the warranty on the above referenced vehicle identification number for all internal mechanical engine components that are lubricated by engine oil to 6 years or 100,000 miles whichever comes first. Enclosed is a copy of the extended warranty statement for your records. Please insert this page into your Service and Warranty booklet, as it is transferable to any subsequent owner.

We continue to recommend that you only use BMW approved SAE10W-60 synthetic oil in your engine. Please be aware that your engine needs to be at operating temperature before you take advantage of its full power at high engine speeds. Please do not overrev the engine under any circumstances. Be careful not to pump the accelerator pedal when there is no engine load, e.g. when the vehicle is not in motion. The best, most efficient and safest way to warm up an engine is to drive with moderate engine speeds until you reach the operating temperature.

We assure you that we stand behind our product and will always continue to listen to our customers. If you have any additional questions please contact your authorized BMW center or call Customer Relations at 1-800-831-1117.

We wish you many more safe and thrilling miles in your M car.

Sincerely,

Hans G. Duenzl
Vice President,
Aftersales & Engineering

workhurts

Yep, that's the one. Plus BMW was nice enough not to replace the bearings for M Coupe and Roadster owners but did so for M3 owners. Logic may have been the slightly reduced redline. They all seem to have their quirks

platinum997

I can't speak to why Porsche did it but I put ductile iron sleeves in my Civic back in the day. I had problems over 15 lbs of boost and cylinder walk. On an open alluminum deck design, to much pressure causes the cylinders to litterly move, which then scratches/breaks the seal on the head gasket and pop.

With the iron sleeves, no problem with 27lbs and a much bigger turbo.