So I have some catching-up to do. This will be a long post.... Sorry!
We gave the Marco UP12 a solid shot. However, we encountered a problem.
Instead of mechanical bypass oil pressure regulation, we're using a form of electronic oil pressure regulation:
We installed the pump, and ran up the oil system. It was evident that with 2-3X the flow capacity of our old pump, larger pump gears (larger lever arm) and the same size motor, this pump wouldn't do.
The pump speed set by the FADEC to maintain 50 PSI with cold oil was SO low, and SO close to the stall speed of the motor (less than 60 RPM!) that the motor was drawing near it's stall current, which is around 25 amps! This is more than our poor electronic speed controller could handle.
We took another look at the old motor. We removed the pesky thermal breaker, and PROPERLY lapped the gears into the housing. Its spins freely now, draws much less current, and stays much cooler! I believe Miuge and his racing team purchased an aluminum end cap for their pump. I'll try to find one like it, so we can upgrade from our plastic version. I'm also looking for a DC motor heatsink that we could use to keep the motor cooler.
For now, it's working a treat.
We're moving forward with the design of the power turbine section. The renderings below are with placeholder NGVs, as we haven't collected all the information we need from the engine yet.
Lastly, our old turbo was a nightmare. The turbocharger we'd made used parts from 3 different turbochargers (and not even the same ones!). We'd smashed parts together from an ST-50, T-50, and VT-50 to make FRANKENTURBO.
Frankenturbo's shaft seals didn't fit very well, and consequently it leaked oil like MAD. Our first attempted starts of the engine went very poorly because of this. We could get the engine running (barely) with a red-hot turbine and scroll. There was a significant amount of behavior that sounded like surging. It turns out that this was all caused by a SIGNIFICANT amount of oil leaving the compressor shaft seal, being atomized by the compressor, and burning in the combustor and turbine.
This turbocharger wasn't going to do.
We contacted a company called
Blaylock TurbochargersAnd what followed was an incredible experience. They had VT-50 cores in stock, and remanufactured one for us in a week.
"Remanufactured" is an understatement. Blaylock does things a little bit differently, and they do things other shops would call impossible. If your compressor or turbine wheel crashed against the housing or sustained heat damage, they will clean it,
weld material to the tips of the blades, and grind the blades down to spec, or more interestingly
build and grind the blades to any spec you want.
They did just that for us. They installed a 0.130" oversized compressor wheel into the new turbo, and lapped the housing to within 0.010" clearance per side (as close as you want to get with these old turbos). The turbine is also oversized, having been welded and reground as described above. Looking at the wheels, you could not tell the amount of work that they had done. The results of this process are flawless.
My friends and I were in awe of what they were able to do.
We took our "miracle child" VT-50 back to be installed, and to test the engine again. The crusty 40-year-old housing gave no hint at the precise "black magic" work that had been done by Jim and the team at Blaylock. We're very thankful and would DEFINITELY suggest Blaylock for any sort of oddball wheelwork or turbo remanufacture you need.
With the new turbo installed, and the combustor reassembled and checked for heat damage from previous testing, we added some thermal protection sleeking to the oil lines, crossed our fingers, and started the engine:
The engine started and ran perfectly. The turbine was completely cool, and it can spool from idle to ~30 PSI P2 in about one second. Its performance is better than anybody on our team hoped for. We'll be collecting numbers soon.
We left the engine pegged at our maximum fuel flow for several minutes at a time. It was perfectly happy. Fuel consumption is on the order of 12-15 gallons per hour.
30 PSIG P2 is probably not full speed for the engine (we aren't running a tachometer at the moment), but it is currently full speed for our fuel pump.
We'll dig into the combustor once more and open the ends of the fuel needles a bit. They were previously "pinched" to restrict flow, because our earlier flow tests suggested numbers in the hundreds of liters per hour.
We will keep you updated with numbers from further testing.
Thanks for the help!
- Feathers
You give the manufacturer too much credit. They cranked it off the cheapest production line they could find which would turn them out without holes in it... As if they have any idea.
