Hans' RV3 - O-320 with a twist
After a hiatus of about a year, the withdrawal symptoms from selling my share in the RV-4 became too much. And so I have bought myself a -3. The plane is in need of a fair dose of TLC, which I plan to give it.
Coming from a number of Subaru powered aircraft projects that are still racking up trouble-free hours and outperforming all expectations, the knee-jerk reaction was to lose the O-320 and put one of my Subaru conversions on. But I really think I'll pass this time and go with Lycoming. With a twist.
My plans thus far - and comments VERY welcome. These Lycomings are new to me ;-)
1: The plane comes with a mid-time O-320 C3B. I believe it to be somewhat of an oddball, only used on a twin (can't remember which one) in the mid-1950's. Old style parallel mounting points. 7.0:1 compression. Hollow shaft. Carburetted. I don't fancy buying a new engine and then try to get this one off my hands. So the plan is to keep this engine as the starting point.
2: As much as I'd love to go all-out, paying 13K for a C/S prop is not in the books for this plane.
3: I want to run mogas in it. 100LL costs upward of $12 per gallon here, even in this economy. Mogas is still $7-ish per gallon, but gets things within the realm of affordability. Mogas here is 98 RON, which is about 93 in US measurements.
So, the plan for the engine:
Take the cylinders off, do a valve job, check the valve guides.
Change the pistons for 8.5:1 items. I was thinking of the ASC75089F from Combustion Technologies. (what's the word on their products?). I believe 8.5 is about as far as I can go with Mogas, right?
Do I need thick piston pins for these?
Then - Can I fit new rings, or should I then also hone the cylinders?
Injection and ignition will come from two Link ECUs:
Each tank will have its own high pressure fuel pump (preferably IN the tank to eliminate all vapour lock issues) and fuel return line. Each side will have its own fuel rails and fuel injectors. And its own ECU.
Each ECU will also run its own set of ignition coils and (automotive) plugs.
Since you don't want both ECUs injecting fuel at the same time, two externally connected switches (to eliminate any single point of failure) will kill the power to the injector drivers of one ECU at a time.
There will be no more fuel selector valve. The ECU that is at play for injection determines from which tank fuel is used.
Each ECU has its own battery en bus. Batteries are fed from the alternator through a FET coupler.
So basically the only thing that is not redundant is the alternator. I can live with this. If it fails, I'll have two batteries to run things until I land.
If anything else fails, it will be on one site. I then also lose the availability of the fuel in that fuel tank. My flying is not between Iceland and Greenland, so I can live with that.
So, to continue:
Now that the carburettor is no longer needed, and carb icing no longer is an issue, I might as well get those intake runners out of the sump and get some cold air into the engine, rather than lukewarm. So I'll weld up a new oil sump and new intake manifold, with one big throttle body, and some ram air.
And yes, I know. There are vendors out there who deliver excellent products for what I am thinking of here. A few of them are even RV pilots. It's just that after half a dozen engines (including a 600 hp Ferrari V12 in a car project), I feel up to the challenge of developing my own mouse trap.
So... What do you guys think?
Oh, and what power output can I expect? I figure coming from 150 hp, the 8.5:1 will give me 160. The fuel injection and more accurate and stronger ignition 5, the cold air induction another 5 and maybe a handful for better flowing of the intake? So between 170 and 175? Or would that be overly optimistic? It would be somewhat important when ordering a prop from Catto...
Hilversum, The Netherlands
PH-KLT Resurrecting an RV-3B, with Subaru EJ25
PH-BRR Bowers Fly Baby; Imported and upgraded
PH-MGA Jodel DR1050; Built, with Subaru EJ25
PH-SUM RV-4; Imported and upgraded. Sold my share :-(
PH-EIL RV-4; Imported and upgraded for friend. Sadly crashed
PH-ERD Robin DR300; Built with Subaru EZ30 for friend.
Last edited by Lufthans : 06-02-2020 at 03:14 PM.