Subscribed

 

i was thinking of this awhile back, why not. it all sounds like a positive to me

 

Are they lighter than a factory original wheel and therefore spin up faster?
depends if the person who deigned the wheel took material out or not.. cast vs forged of the exact same shape will weight the same.


Are they stronger than a factory wheel?

Forging is physically stronger..which allows them to cut away more materal from the fins... so the strength ends up being about the same.
Less ammount of stronger material =/= more ammount of weaker material. and the forging tolerating the fatigue better than cast over a long duration.




Are they more durable?
should be no reason to worry about durability.. if something strikes the impeller in any case you have bigger issues.
but YES that is their main advantage. more durable.
can tolerate the stretching and shrinking more/longer than cast.





Do they move more air or move it better?

maybee.. did someone in china design the wheel cause it looks cool. or did a hydrodynamics master spend 1000's of hours on a computer and in a dyno room?



Whats the 411 or is it just bling?

here is a garret 88mm billet vs cast
https://www.enginebasics.com/Advanced Engine Tuning/Images/Billet Vs Cast Compressor Wheel 5.jpg




The main reason they came out is.. lets say you are making the worlds greatest turbo for a 8v T2 car,. you figure best case you need to make 200 turbos.. so now you have to find someone to make your wheel.

you want to CAST them.
setting up to cast costs $15,000 for the molds and design . each wheel costs about 5$ to physically cast. total investment 16,000$


you want to FMW/billet them. Deigning the wheel costs 2,000$ for the CAD and solidworks design. Each wheel costs about 35$ to make. 7,000$ total for the wheels.. Total investment 9,000$.


Do you want to CAST your turbo wheel or get Billet turbo wheels for your amazing turbo? for smaller batches billet comes out cheaper than casting. for 10,000 units or more. it makes sense to cast them..
for only a few hundred units its much cheaper to set up billet wheels.

 

sadly in this day and age the word billit is a little over used for marketing and dosen't really mean so much unless preceeded by the word forged .. then you've got something

cold rolled would be better than a cast block of material too

denisity and molicule arrangement = strength

- Dad used to sell metals I picked up a few things when he probably thought I wasn't listening

like cast "pot" metal parts - if weak and easily broken , largeish flake like bits in the break mean to much lead in the alloy

he used to work for canada metal here in toronto (a US company).. which closed down not long after he quit and went to american iron (a canadian company )
I guess $40 000 000 in business following him out the door kinda hurt ...

every ford elecrical part that said made in canada had material he sold them in it from the early 80's through the end of the 90's

 

my interpretation of the compressor map(s) is the billet is slightly better,
with a little extra at low flow/low psi which is nice for transition boost,,

but not significantly better in flow, thus that would not drive the decision imo

 

what are the prices for cast vs billet,?

for e.g. our T3 TD .48 or ford .60 wheels ??

 

I did a little Google brain research and the most common answer is there for the most part is no measurable gain in performance. Not in every case but in most cases if the wheels cast Vs. machined are the same shape, size, etc. Secondly, as reported above, it is a small batch cost math problem. You can CNC out a limited number of wheels cheaper than you can have the same wheel cast. The cost to tool up for a cast wheel is up front pretty costly, and for a machined wheel much less. So if you only need a few (hundred) for example, it costs quite a bit less to have them CNC'd. At some point though, the cost and point of return lines cross and its actually cheaper at that point to go cast. A third reason has to do with the strength of the final product. Like a dragster tire that swells and thins when a dragster leaves the starting line, so does a compressor wheel. Over time, the expanding and contraction forces can and in very rare cases can cause a hub failure where the wheel cracks from the center outwardly and then flies apart. Picture a jet engine blade coming out and a catastrophic failure occurring. The CNC wheel, if made from a quality billet will be stronger and more resilient to this expanding and contracting and less likely to fail. However, this is quite the rare occurrence in a small turbo in everyday use but apparently is more likely to occur in an engine that idles a lot then goes all out then back to idle frequently...like a city bus would do.

Cast Vs. CNC Compressor Wheel

• Less expensive to manufacture in small quantities
• Typically, no increase in performance if the wheels have the same profile and measurements
• Higher durability in some applications
• Just bling in other applications

 

I did a little Google brain research and the most common answer is there for the most part is no measurable gain in performance. Not in every case but in most cases if the wheels cast Vs. machined are the same shape, size, etc. Secondly, as reported above, it is a small batch cost math problem. You can CNC out a limited number of wheels cheaper than you can have the same wheel cast. The cost to tool up for a cast wheel is up front pretty costly, and for a machined wheel much less.

I concur. Most people report hardly any gains at all. I would say do more digging around and like buddy says, I wouldn't rely to much on 'Google brain' for this one.

 

An Inside Look at the New Garrett GTX Turbochargers
5 very good pages of reading
GTX DBB = GTR DBB + a billit wheel (more or less)

I've been personally debateing a GTR 30/82 vs a GTX 30/82 myself

I'll add the GTX is significantly more expensive so that kinda shoots down the reduced cost argument .. at least at the consumer's end of the deal

 

Yes they are lighter and give slightly better transient response Depending on design.

Yes they are stronger and can support higher boost and more stable in boost.

Yes they move more air. IF the wheel is a Direct copy, it will move more air because there is more space between the blades. (billet allows the blades to be thinner)

What you are really looking for is an Upgrade design like the tall finned wheel in your pic. Put a GTX style billet wheel in the stock TII turbo and you have now increased air flow everywhere And increased the overall PR of the wheel. (completely different map) The turbo will now sustain higher boost with much more stability.