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TDI Power Enhancements Discussions about increasing the power of your TDI engine. i.e. chips, injectors, powerboxes, clutches, etc. Handling, suspensions, wheels, type discussion should be put into the "Upgrades (non TDI Engine related)" forum. Non TDI vehicle related postings will be moved or removed. Please note the Performance Disclaimer.

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Old December 26th, 2017, 19:15   #16
crazyrunner33
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The downside about billet wheels is that while they can be made to out perform a cast wheel at peak power, but they're typically slower to respond. A billet wheel is almost always heavier than a cast wheel of the same size.
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Old December 27th, 2017, 01:20   #17
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The downside about billet wheels is that while they can be made to out perform a cast wheel at peak power, but they're typically slower to respond. A billet wheel is almost always heavier than a cast wheel of the same size.
Almost all compressor wheels i used in the hybrid turbos I have made were slower to respond compared with cast wheels on OEM turbos. I have seen many claims that compressor wheels are stronger than cast wheels but invariably every turbo I have rebuilt was made with a larger compressor wheel so itís bound to perform differently. Exception was a gtb2260vk to which I fitted a titanium compressor wheel of almos the same dimensions (60mm) but with larger trim and 10 blades instead of the usual 6+6. It made boost ok although it was a lot slower to make boost in the low range and it surged badly in the 70-80 Mph/2500-3000 rpms range and the drivetrain did not liked it one bit ! It was also much noisier than a similar stock gtb2260vk on boost ! If OEM turbo comes with billet wheel then by all means use it, if it doesnít then leave the cast wheel in there- it does just fine !
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Old December 27th, 2017, 02:42   #18
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Almost all compressor wheels i used in the hybrid turbos I have made were slower to respond compared with cast wheels on OEM turbos. I have seen many claims that compressor wheels are stronger than cast wheels but invariably every turbo I have rebuilt was made with a larger compressor wheel so itís bound to perform differently. Exception was a gtb2260vk to which I fitted a titanium compressor wheel of almos the same dimensions (60mm) but with larger trim and 10 blades instead of the usual 6+6. It made boost ok although it was a lot slower to make boost in the low range and it surged badly in the 70-80 Mph/2500-3000 rpms range and the drivetrain did not liked it one bit ! It was also much noisier than a similar stock gtb2260vk on boost ! If OEM turbo comes with billet wheel then by all means use it, if it doesnít then leave the cast wheel in there- it does just fine !

"I have seen many claims that compressor wheels are stronger than cast wheels but invariably every turbo I have rebuilt was made with a larger compressor wheel so itís bound to perform differently .. so how can you compare cast to billet?

EFR, GTX, even new GTD have billet. its lighter and stronger. if the turbo dosnt perform better with billet then the turbo has not been set up proper after the rebuild.. every tuner and turbo builder in uk will tell you billet over cast every time. billet is far stronger that cast..just look at what billet parts are used over cast in performance builds.. billet blocks , heads , flywheel cranks . all far stronger easier to ballance and often a good bit lighter.

i put a 11 blade billet in my vb hybrid and it made a massive difference in spool time. it was savage lol . far better than heavy brittle cast unit.

cast works fine . but billet it better..imo.. lets just agree to disagree on this one mate, i didn come here to argue.
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Old December 27th, 2017, 04:07   #19
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Your 11 blade billet wheel must have been a better design to what i have used! To be honest, the 11 blades many have used are slower to build boost from low revs and a lot noisier than 6+6 jobbies however if its nice and shiny they must be better! Efr turbos are a lot different and the upgrades doesnt just end at the compressor side!

Gtx series are better suited to petrol engines as they make boost higher up the rev range! If a billet wheel is designed the same as the cast wheel it replaces but its lighter then it will spool better however there are so many variables and most turbos are upgraded with wheels with different trims and larger exducers too! There are many ways to skin a cat...
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Old December 27th, 2017, 06:06   #20
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Your 11 blade billet wheel must have been a better design to what i have used! To be honest, the 11 blades many have used are slower to build boost from low revs and a lot noisier than 6+6 jobbies however if its nice and shiny they must be better! Efr turbos are a lot different and the upgrades doesnt just end at the compressor side!
Gtx series are better suited to petrol engines as they make boost higher up the rev range! If a billet wheel is designed the same as the cast wheel it replaces but its lighter then it will spool better however there are so many variables and most turbos are upgraded with wheels with different trims and larger exducers too! There are many ways to skin a cat...
i suppose i could put it this way, a well made and designed cast wheel will work better than a badly designed billet one. different pitch , curve tip height ect. but that being said all thing being equal a billet will out perform a cast, plus its stronger woth it a big plus
i had a gtx style 11mate and tbh it was a LOT quieter .. my stock va make more noise than the vb with the gtx 11..
.. also when i was looking to buy my next hybrid , iended up with td md445 from turbo dynamic) but also spoke to AET, turbo technics, the turbo clinic , trp and x man and all said 11 blade for fast spool and 6x6 for better top end. all i know is what i exp matched what they said, i went 6x6 this time

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Old December 29th, 2017, 11:31   #21
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6+6 blades always make more boost low down/mid range but they choke at high speeds. Gtx style 10/11 blades do surge badly on lower revs and support more flow as the revs climb ! As above, a billet compressor wheel can be made lighter than a cast one however many I have seen are built heavier by many grams compared to similar cast wheels OEM...
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Old December 29th, 2017, 11:33   #22
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I would not compare the va to the vb, the vb has a better exhaust housing and vnt mechanism !
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Old December 29th, 2017, 14:05   #23
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I would not compare the va to the vb, the vb has a better exhaust housing and vnt mechanism !
about 2 mm in it.. if that1 and vnt in thre vb is 1st gen just like the va.
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Old December 29th, 2017, 14:10   #24
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6+6 blades always make more boost low down/mid range but they choke at high speeds. Gtx style 10/11 blades do surge badly on lower revs and support more flow as the revs climb ! As above, a billet compressor wheel can be made lighter than a cast one however many I have seen are built heavier by many grams compared to similar cast wheels OEM...
most billets are 20% lighter, my 11 blade do not surge as low revs , they spool up very quick but do seem to have less top end pull than 6x6.. go ask any decant turbo maker.. they echo what ive been saying.
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Old December 29th, 2017, 21:43   #25
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6+6 blades always make more boost low down/mid range but they choke at high speeds. Gtx style 10/11 blades do surge badly on lower revs and support more flow as the revs climb ! As above, a billet compressor wheel can be made lighter than a cast one however many I have seen are built heavier by many grams compared to similar cast wheels OEM...
It's like all your info is flipped backwards

the two-height inducer compressor flows more but surges ever so slightly earlier
Think of the outer ones as a separate compression stage from the rest, it packs in a slightly larger volume from the greater open space.
Much like a thinner profile hub, it lets you choke flow more, but the surge line will also move to the right as that extra air has very little angular velocity being that it's close to the compressor's axis. Little velocity means little ability to support any sort of pressure ratio.

machined wheels are generally regarded to be stronger and lighter, but there's so much geometry changes going on that you can't really compare the two reliably.

You can do a lot of nutty (and stupid) geometry stuff to a machined wheel that on a cast wheel you wouldn't get from prototyping to the actual casting process. All wheels start off prototyped as a machined wheel, the casting tooling is only made up after the design work is all done with machined prototypes.
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Old December 30th, 2017, 00:52   #26
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Sorry if My information seems to contradict your facts however I experienced the opposite: less flow on a billet wheel compared to a cast OEM wheel. Must have been a badly designed compressor wheel... I have had better results with stock larger turbos than with modified ones. I have experienced with quite a few billet compressor wheels and the most notable designs features are extra tip height, slimmer hubs and larger inducers...they do make huge differences compared with OEM cast wheels. As 486 noted, there are so many things you can change in a low run milled compressor that it’s rather difficult to compare like for like.
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