really slow truck

woo hoo! getting closer to an answer!

would anybody mind giving me a quick run down on the difference between hypereutectic and cast aluminum???

i remmeber hearing somewhere that the hypereutectic pistons werent as strong as some other pistons, but i dont know if that was right (they could have been comparing them to forged pistons for all i know...)

thanks

bryan

-Joseph-

iTrader: (12)

Here's a little info on what the name "hypereutectic" comes from:

[quote]United Engine currently uses gravity feed permanent molds to produce aluminum pistons. Aluminum, alloyed with copper,magnesium, nickel and silicon are common piston alloys in use today. Silicon is the major alloying element added to the aluminum. It offers a number of benefits in the area of piston production and piston operation.

Machinability
Corrosion Resistance
Weight Reduction
Improvement in Hardness and Strength
Improvement in Expansion Characteristics
Improvement in Wear and Scuff Resistance

Aluminum silicon alloys used in pistons fall into three major categories: eutectic, hypoeutectic and hypereutectic. Probably the easiest way to describe these categories is to use the analogy of sugar added to a glass of iced tea. When sugar is added and stirred into the iced tea it dissolves and becomes inseparable from the iced tea. If sugar is continuously added, the tea actually becomes saturated with sugar and no matter how much you stir, the excess sugar will not mix in and simply falls to the bottom of the glass in crystal form.

Silicon additions to aluminum are very similar to the sugar addition to the iced tea. Silicon can be added and dissolved into aluminum so it, too, becomes inseparable from the aluminum. If these additions continue, the aluminum will eventually become saturated with silicon. Silicon added above this saturation point will precipitate out in the form of hard, primary silicon particles similar to the excess sugar in the iced tea.

This point of saturation in aluminum is known as the eutectic and occurs when the silicon level reaches 12%. Aluminum with silicon levels below 12% are known as hypoeutectic (the silicon is dissolved into the aluminum matrix). Aluminum with silicon levels above 12% are known as hypereutectic (aluminum with 16% silicon has 12% dissolved silicon and 4% shows up as primary silicon crystals).

Pistons produced from these alloy categories each have their own characteristics. Hypoeutectic pistons usually have about 9% silicon. This alloy has been the industry standard for many years but is being phased out in favor of eutectic and hypereutectic versions. Most eutectic pistons range from 11% to 12% silicon.

Eutectic alloys exhibit good strength and are economical to produce. Hypereutectic pistons have a silicon content above 12%. Silvolite’s KB Signature Series pistons use an alloy containing 16-18% silicon. In addition to greater strength, scuff and seizure resistance, the hypereutectic will improve groove wear and resist cracking in the crown area where operating temperatures are severe.

It is the primary silicon that gives the hypereutectic its thermal and wear characteristics. The primary silicon acts as small insulators keeping the heat in the combustion chamber and prevents heat transfer, thus allowing the rest of the piston to run cooler. Hypereutectic aluminum has 15% less thermal expansion than conventional piston alloys
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-Joseph-

iTrader: (12)

Here's another comparison, don't look at the brand, I haven't really liked their pistons, but they have good info <img src="images/icons/smile.gif" border="0">

[quote]Hypereutectic -vs- Forged Pistons
Hypereutectic pistons are used in some original equipment engines. They are favored because of reduced scuffing, improved power, fuel economy and emissions.

Hypereutectic 390 refers to a unique aluminum piston alloy that contains dissolved and free silicon. The material can be T6 heat treated to high strength and stiffness. Non-heat treated 390 hypereutectic alloy aluminum has slightly less strength than conventionally cast F-132 aluminum. With this in mind, we caution the reader about the use of non-T6 heat treated O.E. design hypereutectic pistons for high performance. Silvolite and others do make replacement-type hypereutectic pistons that are worthwhile for stock replacement applications. Original equipment design is almost never suitable for performance applications.

The KB line of hypereutectic pistons were designed around the 390 alloy. The result is a high performance part intended to give the performance engine builder access to the latest in piston technology. Forgings have long been the mainstay of the performance business and did well in the big cubic inch engines of the 60’s. Now, with focus on peak cylinder pressure timing, ring sealing dynamics, cylinder air tumble and swirl, combustion chamber science, and extended RPM ranges, we need to consider some new piston options.

The KB T6 hypereutectics are considerably different than the forgings. The KB pistons have shown improvement in power, fuel economy, cylinder sealing, service life, and cost effectiveness. The reduced thermal expansion rate allows the piston to be run with reduced clearance. A tight piston is less likely to rock, make noise, and burn oil. A rocking piston wears rings and increases blow-bye. The close fit of the KB piston allows the piston rings to truly seal, minimizing blow-by.

The design flexibility enjoyed by the KB series of pistons has an advantage over present day forging practices. The die for a forged piston must be designed so it can be easily removed. This limitation makes it difficult to make a light weight piston without sacrificing strength. The KB pistons' utilization of the permanent mold with multiple die parts allows undercut areas above the pin hole and material distribution in the skirt area that stiffen the entire piston unit. The forged piston requires thick skirts to achieve comparable piston rigidity. A rigid piston rocks less in the cylinder and improves ring seal. The forged pistons' thick skirts add weight. The design of KB pistons gives us the option to build the lightest pistons on the market. Some current KB pistons are not super light for several reasons. If the piston is to be used as a stock replacement, more than a 10% weight reduction will mandate that the engine be re-balanced. Common sense suggests that the introduction of a new product be extra strong at the initial release. As the product becomes accepted, weight reductions are scheduled as regular product upgrades, as justified with actual race testing.

There will always be a market for custom forged pistons. Small runs of forgings are more economical than small runs of permanent mold pistons because of the complexity of permanent mold tooling. Where quantities justify, expect to see future KB pistons developed that are lighter and stronger than anything else on the market. Machined head profiles are easily changed with our CNC equipment so we will stay current with new cylinder head developments. Volume production is expected to keep the price reasonable. Our pricing policy has given the impression to some that we are building an economy, or in between, piston. The truth is, we are striving to build the "State of the Art" piston that is best, regardless of price. Reasonable pricing is just an added benefit.
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-Joseph-

iTrader: (12)

I'm thinking that the heads are the same, not sure. We thought the pistons were different (true flattops vs. dished) but all the part numbers I looked up were the same. I'm still researching a few things for Jason's engine. I did find some off the shelf SRP forged pistons that would work in a 6.0L block easily (4.030" bore). Pricing isn't all that much different though than having some made. It looks like we may save $100, I think I'd rather have some made up for our setup. I'm sure we don't need to bore Jason's 6.0L block, so it would actually be cheaper to have the $600 pistons made for the standard bore size.

really slow truck

thanks joseph!

y2khawk

iTrader: (5)

If i recall, the Caddi is a "Premium Fuel Required" setup.

Pretty sure the advance curves are more aggressive because of it.

-Joseph-

iTrader: (12)

Someone get me a VIN from each engine and I'll check the numbers on the programming, I won't be able to see exactly, but GM does put part numbers on each different program to identify it.

Neil 6.0

'lade = 1GYEK63NX2R165184
HD = 1GCHC29G92E137739

Here's even a VIN from a GMC C3 & a Denali to compare:

C3 = 2GTEK69U011384375
'nali = 1GKEK63U51J265997

-Joseph-

iTrader: (12)

Thanks Neil, I'll check it out after work. <img src="images/icons/grin.gif" border="0">

Neil 6.0

Did ya find anything else out Joseph?