Ross's Subie Trip to the lower '48'

[dlomheim]

Ross:
Thanks for the great write up about your trip to Reno, etc. Do you have some summary numbers of your Subie's performance for the trip...avg. speed, fuel burn, mpg, cruising altitudes, etc. Any temp. issues or has that all been fully sorted out by now?

My dad is a retired USN pilot so I would really enjoy flying out to Reno with him someday as well; but first I have to move my "9A" from a collection of parts, to the real aircraft category!

CYA

Doug Lomheim
9A / 13B / FWF, canopy, wiring, etc, etc.

 

[rv6ejguy]

We cruised at 25 inches and around 4500 rpm. Averaged around 135-140 knots TAS at between 8500-10500 feet.

Fuel burn seemed to average around 7-7.3 US gallons/ hr. but since we couldn't fill the tanks, that may not be quite accurate.

Highest coolant temp seen was 80C (176F) in the climb through some moderate OATs (22C). Highest oil temp was 100C. In cruise, coolant temps were generally 70C (158F) with oil temps between 89C and 93C. EGTs were leaned to about 1380F in cruise.

The oil consumption has been rising for the last 100 hours or so and is now at about a quart every 5.25 hours. When the engine was new, it was about 40 hours between quarts. I believe the 100LL is sticking the rings. Could be something else however.

I've been running a lead scavenger since day 1 and lately a dose of MMO as well for the last 35 hours or so. I've always run Mobil 1 5/50 oil but plan to switch to Aeroshell 15/50 when I change it here to see if that helps anything. The compression had been falling slowly for some time but last time, was up a fair amount. I'll check again now and see what the story is and maybe check the turbo seals and scavenge pump.

Other than the oil consumption, the engine just whirrs along, never skipping a beat.

Our taxi driver in Idaho Falls thought we were pulling her leg saying the plane had a car engine in it.

I flew most of the way while my Dad did all the flight planning and radio work. Never used the auto pilot once. The Bendix GPS is just so nice compared to the old days in unfamiliar territory but we always had the map out too. There is a "gravity well" just north of the border where we always lose lock for a minute or so. You could become very dependent on this stuff.

Not one snag on the aircraft during the trip so I was pretty happy with that. What did I see at Carson City when I got there? A Canadian RV7 with the cowling off changing out a couple of misbehaving P-mags! Grumble, grumble.

Can I interest you in a Subaru?- and a case of oil.

Anyway, fantastic trip with my Dad. Learned a lot and hope the -10 is at least 40 knots faster.

 

[RichB]

Ross, good to see the Suby-6 is still humming along. Couple of questions though...

Re the -6, Why run 100LL vs premium pump gas? I guess that means no wideband lambda as well?

Re the -10, I know you've got the belly scoop to cool the H6, are you expecting any Mustang-style "Meredith effect" goodness from it, and if so, had you thought about dumping the exhaust into the hot-side as well?

 

[David-aviator]

We cruised at 25 inches and around 4500 rpm. Averaged around 135-140 knots TAS at between 8500-10500 feet.

Fuel burn seemed to average around 7-7.3 US gallons/ hr. but since we couldn't fill the tanks, that may not be quite accurate.

Highest coolant temp seen was 80C (176F) in the climb through some moderate OATs (22C). Highest oil temp was 100C. In cruise, coolant temps were generally 70C (158F) with oil temps between 89C and 93C. EGTs were leaned to about 1380F in cruise.

The oil consumption has been rising for the last 100 hours or so and is now at about a quart every 5.25 hours. When the engine was new, it was about 40 hours between quarts. I believe the 100LL is sticking the rings. Could be something else however.

I've been running a lead scavenger since day 1 and lately a dose of MMO as well for the last 35 hours or so. I've always run Mobil 1 5/50 oil but plan to switch to Aeroshell 15/50 when I change it here to see if that helps anything. The compression had been falling slowly for some time but last time, was up a fair amount. I'll check again now and see what the story is and maybe check the turbo seals and scavenge pump.

Other than the oil consumption, the engine just whirrs along, never skipping a beat.

Our taxi driver in Idaho Falls thought we were pulling her leg saying the plane had a car engine in it.

I flew most of the way while my Dad did all the flight planning and radio work. Never used the auto pilot once. The Bendix GPS is just so nice compared to the old days in unfamiliar territory but we always had the map out too. There is a "gravity well" just north of the border where we always lose lock for a minute or so. You could become very dependent on this stuff.

Not one snag on the aircraft during the trip so I was pretty happy with that. What did I see at Carson City when I got there? A Canadian RV7 with the cowling off changing out a couple of misbehaving P-mags! Grumble, grumble.

Can I interest you in a Subaru?- and a case of oil.

Anyway, fantastic trip with my Dad. Learned a lot and hope the -10 is at least 40 knots faster.

Ross,

Sounds like it was a great trip.

For what it is worth with regard to oil consumption and 100LL, the attached image came in last evening from Rod Schneider, another Subby guy who is having fun tearing down the core from my parted out, overheated H6.

The engine did not burn oil, none. But the color of the interior of the combustion chamber is interesting. For the most part I used WalMart 93 mogas but did on occasion top it off with 100LL rather than buy the usual 83 mogas offered at airports.

I think the tan colored stuff is residual material from the lead scavenge stuff we use with 100LL and it may well be affecting valve seating. The final compression test on 7/24/08 was still above the min of 180 but just barely so.

Anyway, Rod is going to report what he finds as he disassembles the engine. My gut feeling all along is these engines do not like 100LL, period.

 

[rv6ejguy]

Ross, good to see the Suby-6 is still humming along. Couple of questions though...

Re the -6, Why run 100LL vs premium pump gas? I guess that means no wideband lambda as well?

Re the -10, I know you've got the belly scoop to cool the H6, are you expecting any Mustang-style "Meredith effect" goodness from it, and if so, had you thought about dumping the exhaust into the hot-side as well?

The big thing for cross country work is most airports don't sell auto gas. We don't use an O2 sensor so from that perspective, the 100LL is no problem.

On the -10, I'm instrumenting the scoop to measure velocities and pressures to see what sort of drag penalty we have in the radiator system. I'm not expecting any thrust from it. On the -10, it is not practical to use the exhaust to pump air though the radiator system without some really major changes IMO.

On the 100LL compatibility front David, we may indeed find that Subes do not enjoy this diet. There have been a few reports of premature valve problems from Australia although there may be other factors like high EGTs in these cases. I'll be interested to find what the tear down shows on your old engine. We are building a database on these engines slowly. It seems that there are a number of Subes getting 2000-3500 hours between overhauls when burning auto fuel used in gyro flight training.

I mentioned before that I saw no sign of lead deposits in the pan on mine last year running Mobil 1 but it is a fact that full synthetic oils do not hold lead in suspension as well as conventional oils. Whether this affects the ring/ land junctions or not is not well understood at this time. The high oil consumption on mine indicates a possible ring sealing issues rather than valves. We'll keep running, trying the Aeroshell oil and monitoring until we have to pull it to see what is happening.

 

[RichB]

Fair enough. I figure most people who want to run Subaru (or perhaps rotary) engines should assume a diet of 100LL then. Which leads to a couple more questions...

What oil was Rod's engine running?

How do the Subaru engines fare when running leaded race gas in cars? And if they do okay, what's the difference... just run time, or are there hotter sparks, more pressure, etc, to help clean the combustion chambers out as well?

 

[Geico266]

The big thing for cross country work is most airports don't sell auto gas.

You may or may not know this, but it is worth repeating for those who don't. AirNav as a feature under flight planning to only show airports that do have mogas. This would help in your CC to only use unleaded fuel in your Subie.

Just click on the automotive mogas link on the right hand side after filling out your airport and your destination. Works for me when flying Rotax engines. Also, click on the "24 hour service, no advanced notice". This will get you airports with credit card readers.

http://www.airnav.com/plan/fuel/

 

[rv6ejguy]

Fair enough. I figure most people who want to run Subaru (or perhaps rotary) engines should assume a diet of 100LL then. Which leads to a couple more questions...

What oil was Rod's engine running?

How do the Subaru engines fare when running leaded race gas in cars? And if they do okay, what's the difference... just run time, or are there hotter sparks, more pressure, etc, to help clean the combustion chambers out as well?

Very few Subaru road racing cars these days would use leaded fuel these days, more likely a higher octane unleaded fuel or pump gas. Drag racing ones probably do but never get enough hours on them for anything to happen.

I used to run road racing engines on 100/130 or 100LL for years and never saw any issues like this. Just a light coating of lead deposits on the valves and chambers like you'd seen in a Lycoming.

Thanks Larry for the tip. That could be very useful.