Made some interesting discoveries about Holset "replacement parts" today...

[RWD4G63]

So, I ordered up a replacement turbine wheel from ebay for this HX40 I had here at the shop. There are only a few makers of aftermarket wheels for this turbo, and I doubt any of them are more quality than this.

While at first glace this looks like a viable replacement part. Upon closer inspection, you start to notice some differences.

The first thing I noticed was the backside of the turbine wheel. You can easily see with your eyes that the exducer fins are much thicker. You can even see from the side that the blades are a bit thicker in the middle.

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I figured I'd go ahead and weigh them.

Replacement wheel: 436.9 grams
OEM wheel: 394.4 grams

That's right, the replacment wheel 42.5 grams heavier!

This blew me away, so I had to measure the wheels at this point.

Replacement inducer: 75.64mm
OEM inducer: 76.2mm

That's a .26mm or .010in difference on the inducer!

Replacement exducer: 63.98mm
OEM inducer: 64.13mm

That's .15mm or .006in difference on the exducer.

So basically you're increasing the clearance inside the turbine housing, plus a heavier wheel, and the end result is a slower-spooling, less efficient turbo with one of these turbine wheels. Another good reason to buy OEM Holset parts for your Holset turbo.

 

[JusMX141]

You'll also notice the factory turbine's blades are a bit redder- this is the type of Inconel used by Holset versus the aftermarket turbine which is mostly Stainless Steel. This redness is quite visible when new:

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I'm a huge advocate of using Genuine parts....and I always use Genuine internals if the factory Holset thrust parts are worn, but if a customer sends a turbo in with turbine damage, it's often a difficult sale when a new Genuine turbine adds $200-$250 to the repair bill.

My experience with the high-quality aftermarket replacements is pretty damn good- in two different turbos they've taken over 40psi, one making over 600hp on pump gas with meth injection.

Another fun tip- the HX40 that Dave has been running for the past three years and is getting ready to take into the 8's was rebuilt using a TraderGreg HX35/40 kit but I re-used the factory thrust hardware because I was out of Genuine kits at the time.


Now I recently had a bad experience with the turbine from a complete Rotomaster CHRA for a GTP38 on a customer's Powerstroke turbo- turbine inducer tips sheared off after just 5K miles and wiped out a good portion of the turbine wheel despite there being no further damage to the internals from any type of oiling issue. There's a situation where the aftermarket turbine couldn't even hold up to standard use at roughly 20psi on the factory application.

Some aftermarket parts are perfectly acceptable- you just need to be picky and buy from a trustworthy seller.

 

[WES_393]

Interesting.

With the "OEM replacement" turbines I've purchased, the blades are the same thickness but obviously made from a different (and weaker) material. After a few short miles and 1 episode of anti-lag, the replacement turbine already has some erosion on the inducer and discoloring from heat. My Holset turbine was put through much more, for much longer, and still looks new (minus the white ash from E85). Spool time is increased as you mentioned (although there's other factors involved) and it just doesn't sound like the same turbo. It doesn't sing like my Holset did.

So my discoveries are a little different but the point is the same: There's no replacement for a genuine Holset. High quality aftermarket will work just fine, but genuine parts are definitely worth the extra cash.