Finally got a moment to report on the RV-8 progress. I have about 2.5 hours of ground testing over the last month or so on the 20B RV-8 with mixed results. The Bluemountain stuff is working great and the display is crisp & bright in daylight as advertised. Very pleased so far.
The first attempted engine start after installing all the instrumentation resulted in a loud bang followed by the sound of dripping liquid (I was inside the hangar). The other 'first start' at last year's rotary roundup fly-in was with no instrumentation and the engine temporarily 'hot-wired' for the demo. Climbing out of the cockpit, I found gas dripping from the exhaust pipe into a sizable puddle on the floor. Note to self--- Perform all first starts outside in the future.
Problem turned out to be a misfire on one of the injector disable switches causing always on injectors. After correcting that and clearing the flooded engine, the engine started immediately and I thought the engine sounded much louder than last year's engine run. Before I had just the exhaust header on with no muffler or tail pipe and the engine was surprisingly quiet. I had added the rest of the exhaust system up to but not including the under belly muffler. I thought this might make it even quieter than it was before but the opposite was true. When throttled up to 24" manifold pressure the sound is powerful and defening. I will need something bigger than my golf cart with chocked wheels to test it at higher power. At 25" Hg and 5000 RPM It jumps the chocks and the RV-8 starts dragging it down the runway even though the cart parking brakes are on.
Having no vapor lock problems so far with the non-circulating fuel rail scheme. I used a remote fuel pressure regulator near the pumps (inside cockpit) so the fuel goes only one way to the fuel rails with no return. Return is from the regulator to fuel tank. This arrangement is used on most late model cars and vapor lock does not seem to be a problem. On my Mazda Tribute I do notice that on a hot start on a hot day there can be a momentary stumble from vapor in the rail but it clears immediately.
Not sure why but this engine seems much more critical in mixture tuning than any of the 13Bs I've run. The mixture control only has about 70 deg. range where the mixture is OK which is about half the range I have on other engines. The 20B injectors are about the only variable I can think of that could affect this.
Cooling is surprisingly good. On a 90+ degree day the coolant stabilizes at 200 F and oil at 185. This is much cooler than my RV-4 on extended ground runs.
The bad news is engine friction that I notice when pulling the prop through compression cycles. BTW, with only a little experience you can gauge the relative health of a rotary with just a few pulls of the prop through all 6 (or 9 on 20B) compression cycles. When cold this 20B feels close to normal for what I would expect on a freshly overhauled engine considering it has one more rotor than my 13Bs. But when it's hot the internal friction is much higher. When switched off after a run, the prop stops quite abruptly. Immediately afterward, it will not rebound from a quick pull into compression after releasing the prop. Hot starts are very sluggish and sometimes not possible with the tiny battery I'm using. I keep hoping this will change after break in but so far it doesn't look good. OTOH, the Renesis took a full 40 - 50 hours to break in. I do NOT want to open this engine again but it may be necessary. I keep having nightmares of Ed's ordeal with an engine that felt very similar to this. Time will tell. lots more things to test before making that decision.
Tracy
|