Some real data
RAMPEYBOY said:
I don't mean to debate one engine versus the other. I started this post to see if there were any out there flying the engine who could offer real life experience with it. I'm not interested in the claims of those selling parts for the conversion. They usually do have high opinions of them
If you have your mind made up go for it. If it works out great. If not you can bolt on a Lycoming. I guess my point before was you are taking a little more, shall we say, risk, at least a risk in that the out come is a bit of an unknown. If I can help let me know. I have an engineering background, structural analysis.
There was an article on 10/95 in the RVator. I have a copy from the 16 years of Rvator. Jerry Schweitzer has a V6 ford RV-6 flying.
Here are the highlights:
----------------------------------------------------------------------------------
Empty wt 1130, W&B solo is within but near the fwd limit. "Our RV was the heaviest we saw at Oshkosh"
(NOTE: in 94-95 typical RV's had lighter props and panels. In the 21st century RV's have gained weight with bigger engines, c/s props and fancy panels. However 1130 is not that bad.)
Thrust line is 2.5" higher than normal.
Vert stab is displaced 1" left, no rudder needed in level flight.
Engine installation:
392 lb w/o coolant, oil, hoses or exhaust
Prop: Sensenich W71T5 H23-8- fixed wood
Engine: Ford 3.8L with "every enhancement of value for aircraft use $4200
Northwest Aero Belted re drive 1.7 to 1, 4" shaft extension $2800
Cooling: Custom radiator, surge tank, hoses, etc $375
Exhaust: from automotive pipe, no labor $17
Oil Tank: Friend welded $24
OTHER ITEMS USED BUT NOT REQUIRED:
Ellison throttle body injector $1500
Christen oil valve and fitting $227
Sensenich prop and adapter $1600
Performance:
Press Alt:.........7,500...8,000...10,000...2,000
OAT C:.............25........25........20........31
eng RPM:.........4726....4777.....4811.....5010
prop RPM:........2780....2810.....2830.....2947
MAP:...............22.......21.5......20.2......26.7
egt C:.............870......870......870........850
TCAS (mph):...175.4....173.....175.7......184
fuel flow:.........8.1.......8.1......8.0........N/A
General:
Vibration: Our Ford, except when starting and stopping, does not run more smoothly than a well maintained Lycoming. There is a narrow range where out engine exhibits a vibration somewhat like the 2100/2200 rpm range of many O320's with metal props. Settings in normal operations are quite smooth.
Reliability: 460 hours of ford flying experience, 400 in a PA-22 and 60 in the RV.
Cooling: 40 hours when surface temp was 90-105F with out cooling problems. Our cooling systems ad associated air inlets/outlets may be contributing to unnecessary drag.
A timed climb from 1000-8000' at 100 mph with outside temp around 32F calculated to 863 fpm.
LATER updated on 12/95
Changed from wood Sensenich to IVO gnd adjustable prop.
Cowl clean up, removed sharp edges in air intake opening
More efficient air entry into throttle body
TCAS (mph) at 8,000' went from 173 to 183.8 with FF went from 8.1 to 9.1 gph.
(To put this in perspective; This is about 4 mph slower than a 150hp RV-6. A 150hp RV-6 at 75% power should be around 7.5-8.4 gph. So the Ford is a few mph slower and about 1 gph more burn. If you compare to 160/180hp, their respective cruise is 191/199 mph at about the same or slightly more fuel burn.)
----------------------------------------------------------------------------------
This shows several things. One auto engines can be a continuous process of improvement and experimentation. That sounds like fun. They mention their suspicion their cooling is costing them drag. No doubt.
As far as performance its a little slower for the same fuel burn (184 mph/9.1 gph). Not good, bad or indifferent. It is what is is. Also it shows getting a good prop is a bit of hit an miss. Climb rate was not great for a RV, but that is to be expected.
Cost was almost $11,000 (in 1995). That was with a home made mild steel exhaust. No mention of engine mount modification. What was a used Lycoming in '95 going for? Also note the do it yourself spirit. Again I think when you get the real unsensationalized info you see that there is no free lunch. It takes so much HP to go so fast. Engine efficiency between one internal combustion is not much better than another. The real challenge is making a light weight installation and minimizing drag.
BOTTOM LINE: Are you going to be happy with a plane that climbs slower and cruises slower. One of the fun things to do s fly with other RV's. The circa 95 bird above would have a hard time keeping up with other RV's. Also at $11,000 and no mention of engine mount modification, plus the time to modify the cowl and so on, does a used O320 not sound a little better? I would guess a 150hp Lyc could out run this above installation and weigh much closer to 1000 lbs than 1100lbs. It is not about carrying extra baggage or gizmo's, it is about handling, stall speed and climb rate. Weight is a big factor on how "light" the control feel.
If this is not big deal than you are the guy to do an V6 conversion. Again if you need any stress analysis I might be able to crunch some number for you.
George