Confused about the weird turbo?
Well, when I first read about this "super" turbo I was confused too.
As some of you might know recently a customer and good friend of mine bought a car from Munich with a completly blown turbo charger.
For those asking how bad it was, feel free to watch it:
It was a wonder that the compressor wheel didn't suck itself in. Especially when you consider how loose it was already.
So - finding the issue was easy. Throwing in a new turbo and IC resolved it completely. Especially the later one was filled with extreme amounts of oil.
Yet nobody gives me a car just to fix it.
No - this one had a clear goal. +250HP with high responsiveness, especially from low RPM areas.
Usually the TD04-15T or TD04-19T spool around 2000-2250RPM, depending on the exhaust flow, which was totally unacceptable in this case.
Customer is king, no discussion needed.
Therefore, I started doing some research about some Garrett GT28 and 30XX chargers. While these featured indeed better spooling, they were also really pricey with around 1200-1500€ for an original unit.
To have a comparison - a TD04-15T or 19T from Arashi with an install kit costs just 680€.
Suddenly Holset came into my mind.
For those who never heard about Holset - they are the biggest single turbo manufacturer on the market. Their turbos are mostly targeted for industrial use in trucks, excavators or ships. Some of their turbos were even used in Formula 1 vehicles in the early 70s.
Yet many of their heavy duty chargers, especially the HX35w and HX40w, were used in the 9000. But would there be a solution for the 9-5 as well?
Turns out that Stavtech made an interesting article about the Holset HX successor HE. Especially the HE211w and HE221w grabbed my attention. With a TD04-15T housing these were basically bolt on to the downpipe and flange.
Besides that it was the only turbo to spool at around 1750RPM. Earlier than any Garrett or MHI could do and that with the same, if not even higher durability.
All of that for just 680€!
Here a side by side view of the HE221w vs a TD04-19T.
However, it is not as simple as it might sound.
Issue No.1 - Big inlet
As you can see the inlet is massive being scaled at 3". Most people would run that for their downpipe or exhaust system, but Holset takes it serious from the start.
One could probably just swap the housing completely to a 15T, but I didn't waste almost 700€ on just some CRHA unit I could have got for less than the half. Lets not even mention the loss of the anti surge compressor housing.
Instead there are two options. Either make a custom cobra pipe or just cut one in half, so one could connect a 90Â° elbow reducer silicone hose to both ends. As my customer did not demand more than 300HP this should still deliver enough air and provide the least cost and effort.
Issue No.2 - Cooling
Another "speciality" for the HE221w is that it is - unlike the TD04 series by MHI - solely oil cooled. There are no water feeds or returns, meaning the T piece for the TP to water return needs to be set dry or directly connected to the waterpump.
The other question will be how we can properly cool the turbo once the engine has been shutdown. While it is possible to skip on that, if one drives it off properly, I am really curious to see, if one could modify the T7 code to keep the engine running for 30s-60s, once the key has been pulled off.
Issue No.3 - Boost control
Since the HE221w is a very early spooling turbo, it is absolutely necessary to protect the crankshaft from becoming bent like a banana. Therefore, it is extremely important to keep the airmass as low as possible during low RPM areas, while not loosing to much as we wouldn't benefit from the fast spooling characteristics the Holset features.
As of now I could mostly drop the workload onto the APC, yet the idea of hysteresis seems to be an interesting way to extend the turbos possibilities (more about that later).
But before I can finally throw it in, I still need to remachine and surface an old 15T turbine housing...