I was browsing Facebook or LinkedIn and, on my feed, a Garrett article popped up about some e-turbo stuff; I snagged these pictures from the linked article. The Garrett Motorsports group in Brno, Czech Republic (there is also one in Torrance, CA being global company and all) hosted a tech day to show off some new tech. If you haven’t been keeping up, e-turbo is the next big thing in turbos as they essentially eliminate turbo lag and can also be used as waste heat recovery ala Formula 1. E-turbo has been used in Formula 1 since they transitioned to the current turbo era. Looking at the passenger car and commercial vehicle scenes, they are going heavy on electrification. So, it would make sense to see e-turbo pop into the mix shortly as they require the high voltage systems that hybrid powertrains can provide. Anyway, what was interesting were two pictures of an unidentified motorsports turbo.
Before we get to the newer turbo, this looks to be the Garrett motorsports turbo setup on the old Audi R15 Le Mans car. Where cost is no object, like the FIA P1 category, magnesium compressor housings were used for mass reduction. If you want to light up the night sky and blind everyone in a half mile radius, throw some chunks of magnesium into a camp fire in the middle of the desert. The R15 was the first motorsports application of a VNT; while it was diesel, it was still running seriously high EGTs and it had to survive the 24 Hour of Le Mans. So, what Garrett learned from this motorsports application, it applied into all of its production stuff to make their VNTs more durable. Notice Garrett launched a gasoline VNT within the past couple years. Check out that brace used to support the mass of the turbo.
So, check out this motorsports turbo. I’ll say with 99.99% certainty this is not a variant of the Ferrari Formula 1 turbo because there’s no way in hell any F1 team would show anything. But I think it’s also safe to say that the Ferrari F1 turbo uses some of the same tech. So, what is this turbo on display? I’m guessing it’s from the R18 which of course, Audi scuttled after Diesel Gate. This would also explain why Garrett can show it to the public. The key technology employed staring us in the face is the variable geometry inlet guide vanes used to condition the airflow before the air enters the compressor wheel. It’s an assembly that bolts onto the front of the compressor housing and uses an actuator to control it. I believe the adjustable vanes help improve compressor surge margin and they possibly help maximize the size of the peak efficiency island on the compressor map too. Notice the compressor housing has two outlets with each going to one bank on a V-engine. Looking at the backside of the turbo, you can see the thin-walled turbine housing for mass reduction.
The view showing the turbo from the rear allows us to see the lever used to control the inlet guide vanes. The turbo mounting links are pretty trick too. You can see the turbine housing is a twin-entry design matching the twin outlets on the compressor housing. The twin entries allow for use of a single turbo placed in the middle of a V-engine. So…. What’s this other rear actuator for? Based on the design of the turbine housing, I don’t think there’s a VNT in there due to lack of apparent space.
This brings us back to the compressor side of things. Zooming into the picture, the compressor housing appears to be in multiple pieces. This is partially due to the design being thin-wall, so it’s easier to cast in a few pieces. It LOOKS like there are inner and outer diffuser surfaces along with a random external fastener which may be holding those parts together. So, it’s my guess there is a variable geometry diffuser to again maximize compressor efficiency over the broadest map width possible. Vaned diffusers have been used to improve compressor efficiency at a specific operating point, so maybe this turbo is using some type of variable geometry vaned diffuser. I’m going to guess the vanes do not change angle, but move in and out; therefore, changes from a vaneless diffuser to a vaned diffuser. I could be completely wrong of course.