Well that was sorta a useless video
What's the deal with these HX40's. Any Holset guys on here? A HX40 seems to be a 60mm turbo with a huge 76mm turbine and a t4 housing? Correct? I guess they are turbos designed for large displacement diesels. That'd explain the large turbine and a small compressor.
On a small motor like the golf such a large turbine wheel/housing will result in slow spool. It just seems to me that it's a mismatched turbo for small engines?
A turbo is a turbo. In this case, the HX40 is on par in terms of size and power potential with the Borg Warner S360 series. The compressors range from 60lbs/min to 69lbs/min stock, there is a billet version of the 69lbs/min wheel and a batmowheel made by Bullseye Power that has clocked over 70lbs/min. It's just a big ass turbo capable of 600 ~ 750whp pending your setup.
For the most part you are right, it's a bit large for that Golfs motor, unless it was built for larger turbos/meant to flow and actually put such a big turbo to use but not many people think that far ahead and slap the biggest fucking turbo they can get into a car to say 'hurrrrrrr i gots teh big sausage1'.
They are cheap too. To diesel trucks/Cummins guys they are tiny useless turbos, but to gasoline powered cars they are mid sized to larger. They are cheap, I bought my HX35 (s256 sized) for $150, it's the 7 blade compressor which flows 60lbs/min. The hotside on it is comparable scale is 0.89ar, stock 12cm divided T3. It might be a bit large but it's perfect for this top end turbo. I see 20psi by 3.4 ~ 3.6k RPM. Bullseye Power makes various T3 and Mitsu flanged hotsides for the Holset series, so you can get varying sized hotsides if you'd like (yes the stock ones are HUGE on the HX40).
One more note, just because they are cheap doesn't mean they don't last. They were built to be beat to shit, over boosted and over heated - most diesels are running these at 40+psi all day. In the car world most will be in the high 20s and the guys going for serious power can probably afford to replace something if it breaks lol. Hope that helps.