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BMW Engine Powered by Aluminum Piston

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Dave Palmer
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Re: Is aluminum strong enough?
Dave Palmer   7/16/2012 5:42:08 PM
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@Chuck: Yes, Mercury used their proprietary Mercosil low-copper hypereutectic alloy, along with a nickel-based piston coating, for some 15-25 HP engines in the late '90s.  As far as I know, they never used it outside of that horsepower range.  I'm not quite sure why it hasn't been more widely used, since it does seem to have offered a number of benefits.

Mercury's decision to keep most of their casting in-house and to develop it as a core competency has paid off; the Mercosil alloy is sold commercially, along with a series of die-casting alloys, called Mercalloy, which Mercury developed.  Mercury casts these alloys for outside customers, and also licenses the alloys to foundries.

While Evinrude closed its die-casting division prior to the OMC bankruptcy, they have held on to their lost-foam casting facility; in fact, they recently won Best-In-Class in the AFS Casting of the Year competition.  Like Mercury, they also do work for outside customers.

RICKZ28
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Platinum
Re: Is aluminum strong enough?
RICKZ28   7/25/2012 3:07:00 PM
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I believe the GM "LS" series V8 engines used in rear-drive cars since 1997-1998 is an all-aluminum block (no iron cylinder liners).  It was first used in the 1997 Corvette.  The LS engines are used in the current Corvette and Camaro high-performance cars.

http://en.wikipedia.org/wiki/GM_LS_engine

http://www.gmhightechperformance.com/tech/0901gmhtp_ls1_ls6_ls2_ls3_l99_ls4_ls7_ls9_lsa_engine_history/viewall.html

 

Personally, I own a 1998 Chevrolet Camaro Z28 that is factory equipped with the LS1 5.7 liter V8 with aluminum block and heads (and 6-speed manual transmission).  I have 135,000 miles on the car, and it still runs like new...brutal power and acceleration by normal car standards.


For most GM truck applications, the LS engine blocks are cast iron.

During the late 1970's, I had a 1973 Chevrolet Vega with the aluminum block.  It drank about one quart of oil for every 100 miles, due to the aluminum cylinder wear.

Ockham
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Gold
what's the big deal?
Ockham   10/11/2012 4:56:39 PM
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Don't quite get the point of this article.

Aluminum pistons, cast, hypereutectic and forged have been standard fare for piston technology for decades, some of them in very high stress applications.

They're talking about 93kW per liter. O.K. that's a 250 hp 3 liter diesel. Great. I was getting over 600 kw out of a turbosupercharged 7 liter V8 over two decades ago, and it had typical OEM forged aluminum pistons. They seemed to hold up just fine, even with over 20 inches of turbo boost...and I did all that design with a piece of paper and a slide rule and OEM components! :-)

Aluminum blocks? So? That's no big shakes either...and long before the Vega, too. They've have been around in various GM products since the early 1960's (Buick 215, Corvair flat six, etc.)

The much maligned Vega used aluminum block and cylinder with a spray coated cylinder wall which failed rather miserably in the Vega. But (like so many other technologies prototypd on the Vega, such as the HEI ignition system) very similar technologies eventually made their way into the GM product line, like the LS1.

Pardoning the pun, why are we suddenly so gassed about an aluminum pistoned turbo diesel?

 

 

Dave Palmer
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Re: what's the big deal?
Dave Palmer   10/11/2012 7:43:34 PM
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@Ockham: Here is an article that describes in more detail why these pistons are a big deal.  Was your 7L V8 turbodiesel for racing? If so, you probably didn't need to worry too much about thermal fatigue.  Also, two decades ago, you probably didn't need to worry about emissions too much.

Aluminum pistons are obviously nothing new, but in order to reduce diesel emissions, it's desirable to get piston bowl temperatures as high as possible.  Unfortunately, if you get them too high, the aluminum will melt. (Also, at temperatures near the melting point, the fatigue strength of the aluminum is greatly reduced).

Interestingly enough, when the aluminum melts and resolidifies, its mechanical properties are greatly improved.  This is the idea behind Federal-Mogul's Durabowl process.  I have no idea how they got the idea, but I wouldn't be surprised if it occurred to someone while looking at a failed piston.

Ockham
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Gold
Re: what's the big deal?
Ockham   10/11/2012 9:37:01 PM
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Hi David, Thanks for the article. Makes sense re: racing my turbo BBC. Nope, I drove it on the street - for almost three years. Street racing is illegal! :-)

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