Pics of KB's 2.6L unit.
#16
05-14-2006 | 05:17 PM
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Joined: Aug 2001
Posts: 1,987
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From: MA
Originally Posted by Tim Skelton
Methinks you paint with too broad of a brush.
"Billet" is a process, not a material. Start with soft alloy, and you will end up with soft part. Start with a hard alloy, and you will end up with something stiffer than any casting can produce.
Like most large aluminum parts, supercharger cases are usually cast because it's much cheaper than the machining required to produce it from solid stock (AKA "billet"). When machining a large part, the material costs are also way higher because you have to buy a lot of metal that ends up as shavings.
"Billet" is a process, not a material. Start with soft alloy, and you will end up with soft part. Start with a hard alloy, and you will end up with something stiffer than any casting can produce.
Like most large aluminum parts, supercharger cases are usually cast because it's much cheaper than the machining required to produce it from solid stock (AKA "billet"). When machining a large part, the material costs are also way higher because you have to buy a lot of metal that ends up as shavings.
(Except ofcoarse the smoking issue!)It comes down to money. Cast is cheap. Billet process is expensive.
#18
05-14-2006 | 07:07 PM
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Joined: Jul 2004
Posts: 465
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From: Fayetteville, NC
Originally Posted by Tim Skelton
Methinks you paint with too broad of a brush.
"Billet" is a process, not a material. Start with soft alloy, and you will end up with soft part. Start with a hard alloy, and you will end up with something stiffer than any casting can produce.
Like most large aluminum parts, supercharger cases are usually cast because it's much cheaper than the machining required to produce it from solid stock (AKA "billet"). When machining a large part, the material costs are also way higher because you have to buy a lot of metal that ends up as shavings.
"Billet" is a process, not a material. Start with soft alloy, and you will end up with soft part. Start with a hard alloy, and you will end up with something stiffer than any casting can produce.
Like most large aluminum parts, supercharger cases are usually cast because it's much cheaper than the machining required to produce it from solid stock (AKA "billet"). When machining a large part, the material costs are also way higher because you have to buy a lot of metal that ends up as shavings.
#19
05-14-2006 | 09:22 PM
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Joined: Dec 2000
Posts: 2,365
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From: Elkton, MD
The Gen 2 Lightning specific was the only cast supercharger casing I've seen from KB. I'm sure cost and overall appearance was a contributing factor. However, the 03/04 Cobra, 05/06 GT, etc. are all billet superchargers and flex doesn't seem to be an issue.
I personally like the looks of the billet casing, rather than the cast.
I personally like the looks of the billet casing, rather than the cast.
#20
05-14-2006 | 09:25 PM
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Joined: Jul 2004
Posts: 465
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From: Fayetteville, NC
Originally Posted by 99svtlightning
The Gen 2 Lightning specific was the only cast supercharger casing I've seen from KB. I'm sure cost and overall appearance was a contributing factor. However, the 03/04 Cobra, 05/06 GT, etc. are all billet superchargers and flex doesn't seem to be an issue.
I personally like the looks of the billet casing, rather than the cast.
I personally like the looks of the billet casing, rather than the cast.
Last edited by NCsvt2003L; 05-14-2006 at 10:26 PM.
#21
05-14-2006 | 10:05 PM
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Joined: Feb 2003
Posts: 413
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From: Kihei, HI (most of the time)
The debate between the merits of cast aluminum, like alloy 356-2 vs forged material, like 6061-T6 has raged for years. Here are some sample numbers:
356 has a yield tensile of 24,100 pounds per sq inch.
6061-T6 has a yield tensile of 40,000 pounds per square inch.
356 will elongate 3.5 percent before it fractures.
6061 will elongate about 12 percent before it fractures.
So, the 6061 or "billet", does win the battle on strength. However, cast material tends to be quite a bit more stable, with less post-machining distortion. A chunk of 6061 big enough to make that blower housing is going to warp a whole bunch once all the material is removed from the center. If I were machining the housing myself, I'd rough machine it to within about 1/16 inch of final size and have it cold stabilized. I'd then finish machine it, knowing it was still going to move.
I've seen latent stresses in 6061 distort parts for a month after final machining.
So, given a choice, I'll take my blower housing as a casting, but still want my pistons to be forgings.
356 has a yield tensile of 24,100 pounds per sq inch.
6061-T6 has a yield tensile of 40,000 pounds per square inch.
356 will elongate 3.5 percent before it fractures.
6061 will elongate about 12 percent before it fractures.
So, the 6061 or "billet", does win the battle on strength. However, cast material tends to be quite a bit more stable, with less post-machining distortion. A chunk of 6061 big enough to make that blower housing is going to warp a whole bunch once all the material is removed from the center. If I were machining the housing myself, I'd rough machine it to within about 1/16 inch of final size and have it cold stabilized. I'd then finish machine it, knowing it was still going to move.
I've seen latent stresses in 6061 distort parts for a month after final machining.
So, given a choice, I'll take my blower housing as a casting, but still want my pistons to be forgings.
#25
05-16-2006 | 08:39 AM
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Joined: Mar 2001
Posts: 830
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From: Plymouth, MI
