Interesting article about Billet vs. Cast wheels

[Mwolf83]

Depends on the material being cut, Aluminum can be cut for practically forever with the same carbide endmill... Stainless or other high nickel alloys... not so much. The reason the wheels might be expensive is the fact that you need a 5 axis CNC mill to do turbo wheels. And the number of hands the part goes through by the time it gets to the end user. Machining aluminium with the right tooling is like cutting butter with a steak knife.
This isn't always the case either, yes when cutting aluminum the tooling will last longer, but the tooling will not last "forever" and sometimes not long at all. I work in a machine shop where we make aluminum cases for Polaris, Arctic Cat, Yamaha, Honda, etc....and we will end up changing some tooling whether its endmills, drills, facemill/bore head inserts, or whatever the tool may be every couple hundred to couple thousand parts. There are even some parts that may require a tool change ever couple part.
There are hardened steel shafts that get bored out by carbide inserts that can even last as long as a few hundred parts before a change is needed. Many many many factors.

[Shane@DBPerformance]

Regardless of if it costs $5 or $50 to make a compressor wheel, the main cost of new technology is normally going to be R&D. You can't spend a million dollars developing a new product and then sell it for $20 because it only costs $5 to make, unless you are going to be selling millions of them.

[FFPerformance]

I think there are some misconceptions about the wheels out there.... yes there is a bit of 'bling' factor that people are willing to pay for, and perhaps 'Billet' is equal to Titanium as a buzz word to sell by. Who knows.

I would agree that differences in comparing a cast vs billet wheel OF THE SAME DESIGN, would show similar results on the dyno, but keep in mind that most small run, and test compressor wheels are made by CNC. Generally these are of a newer design and potentially better performance than standard cast ones that have been around for a while.

But, to stir the pot ;), what about the material differences? A cast alum wheel is weaker than a billet version even if it's the same alloy. Most good billet pieces will be forged and therefore stronger. What does that mean? From some research I have done over the years, a stronger wheel will have less blade deflection, you would be surprised at how much the fins bend at full load, and you will have a performance gain from the added stiffness. What people should be talking about is the same wheel made of Titanium and see what happens.... ;P

$.02

-Bob

[Halon]

I would agree that differences in comparing a cast vs billet wheel OF THE SAME DESIGN, would show similar results on the dyno, but keep in mind that most small run, and test compressor wheels are made by CNC. Generally these are of a newer design and potentially better performance than standard cast ones that have been around for a while.


Exactly. I'm not trying to confuse the two, and what you said is exactly it. The reason I bumped this back up with another article is because I've heard from a few people recently who have said specifically that they were under the impression that a billet wheel will spool faster and produce more power simply due to the fact it is a billet wheel, and that it makes it lighter.

What makes the new billet wheels better is not because they are billet, it's because they are NEW. New better design, not because it's bling bling.

Also, which mainstream turbos are you aware of that are machined from a forged piece of aluminum rather than just a cast piece of aluminum? I ask because I have no clue.

Just because my BW is a cast wheel, doesn't mean it's not going to hang with, or exceed the performance of a PTE Billet of similar size :)

*Edit - from what I gather, it appears the new BW EFR comp wheels are forged billet wheels :)

[Super Bleeder!!]

But, to stir the pot ;), what about the material differences? A cast alum wheel is weaker than a billet version even if it's the same alloy. Most good billet pieces will be forged and therefore stronger. What does that mean? From some research I have done over the years, a stronger wheel will have less blade deflection, you would be surprised at how much the fins bend at full load, and you will have a performance gain from the added stiffness. What people should be talking about is the same wheel made of Titanium and see what happens.... ;P

$.02
-Bob

I have no background in manufacturing so take this with a grain of salt; but from what i know, a forging is strong/desirable because of the compressive residual stress near the surface which is manifested during the forging process. Once you start cutting into that surface and removing that layer, it no longer has the benefits of a forging. It is now a metal thing carved out of a larger piece of metal.