Diesel RV-7 & RV-9

[kgood]

Bill, I think you misunderstood the intent of my post.

I was trying to point out that that in "real world" scenarios, (the whole flight profile, not just the cruise), the diesel has advantages. I used the Redhawk as an example because it is a documented "real world" scenario. I know that these planes are used for training, not what us RVr's do. But even using your logic, with all being equal, 5.3 gph is still 40% better than 7.5 gph.

The point is that the diesel used less than 1/2 the fuel doing the same mission. I also pointed out that the Lycoming uses substantially more fuel on climb, which would help to explain the difference in fuel consumption - since training involves a lot of take-offs and climbs.

When I tested my Wilksch diesel in a "RVr's real world scenario" against Van's own RV9A, we did a "same day, same way" flight, which included climb and cruise. We flew side by side, exact same flight profile, only we (Marc Cook and I) were 70lb heavier. Ken Krueger from Vans set the rules: "Use every trick you know to cut the fuel burn, and I'll do the same". For me, it was simply full power climb, then set the cruise power at 75% and fly. At the end of the flight, we topped off and we had burned 5 gal, while the factory plane had burned 7.2. We also did a cost comparison for the flight, and, since Jet A was much cheaper, that widened the cost gap even further.

Believe me, I'm not beating up on Lycomings - they are well proven, reliable, reasonably priced powerplants. In LOP cruise, they're pretty darned efficient. I'm only trying to demonstrate that in some applications - even with the higher purchase price - diesels can save money.

Kurt

[rzbill]

Now that last example is great. Planes flying side by side which means same (or darned close to it) power expenditures. Fuel usage right where the thermodynamics says it ought to be for both craft. Unarguable comparison. That's what I was driving to.

I do get the other example as how a company could save money but the saving was half efficiency (diesel over gas) and half in reduction of craft performance and operation style which muddies the water.

Deltahawk was supposed to be the next big thing. Hope you're still not holding your breath.

[Bevan]

I don't think we're going to see a diesel "aircraft" engine in the same price range as we currently typically see for a new Lycoming (say $20-30G) unless is it a modification of another common engine made for automotive, marine, or ground power units etc. This is mostly due to economies of scale.

Is anyone working to convert the Subaru boxer diesel for aircraft use?

Bevan

[rv6ejguy]

Originally Posted by Bevan

I don't think we're going to see a diesel "aircraft" engine in the same price range as we currently typically see for a new Lycoming (say $20-30G) unless is it a modification of another common engine made for automotive, marine, or ground power units etc. This is mostly due to economies of scale.

Is anyone working to convert the Subaru boxer diesel for aircraft use?

Bevan

The EE20 Subaru has not worked out too well. Broken crankshafts, bearing problems and cracked blocks in 2007 to 2009 models at least. Maybe the problems are solved now. The crank design looks pretty scary for a diesel.

[Bevan]

Originally Posted by rv6ejguy

The EE20 Subaru has not worked out too well. Broken crankshafts, bearing problems and cracked blocks in 2007 to 2009 models at least. Maybe the problems are solved now. The crank design looks pretty scary for a diesel.

Hi Ross,

Are you saying they didn't work out too well in aircraft, or in the vehicle?

Bevan

[rv6ejguy]

Originally Posted by Bevan

Hi Ross,

Are you saying they didn't work out too well in aircraft, or in the vehicle?

Bevan

Vehicle.

http://www.subaruforester.org/vbulle...diesel-120394/

http://www.autoklubi.com/forum/print....php?tid=15700

http://www.subaruforester.org/vbulle...ailure-270186/

Looks like they are still failing in 2010 MY.

[Bevan]

Wow, those pictures of broken cranks are disturbing especially in an automotive environment. I wonder if it's a manufacturing defect that takes x number of cycles to failure, or just a design flaw. Shouldn't be too difficult to redesign for lengevity. I've always thought of subaru as master engineers, but still human evidently.

Bevan

[rv6ejguy]

Originally Posted by Bevan

Wow, those pictures of broken cranks are disturbing especially in an automotive environment. I wonder if it's a manufacturing defect that takes x number of cycles to failure, or just a design flaw. Shouldn't be too difficult to redesign for lengevity. I've always thought of subaru as master engineers, but still human evidently.

Bevan

The crank looks pretty wimpy for a diesel IMO, not what you'd see on a Landcruiser diesel crank. I guess they may have gone a bit too light. Usually the process control is exceptionally good in the automotive world. The goal is 1 defect per million typically.

Subaru has got things wrong before- problems with EJ25 head gaskets, oil pickup tubes falling off, improper mapping leading to piston failures on STis, shortened skirts on EJs leading to cold piston slap etc. Certainly not infallible. The bad thing is they rarely admit to anything so they often lose new buyer loyalty if that buyer encounters issues like this. Might as well 'fess up and do the right thing. They need to do some better QC and validation perhaps.

[rv7charlie]

Originally Posted by rv6ejguy

The EE20 Subaru has not worked out too well. Broken crankshafts, bearing problems and cracked blocks in 2007 to 2009 models at least. Maybe the problems are solved now. The crank design looks pretty scary for a diesel.

Well, that's disappointing to hear. I've been really hopeful that it would be a good candidate for a/c use. Of course, any new design is likely to go through teething problems, like the very early Mazda rotaries. The only real issue with them over the last 20+ years is Mazda's insistence on using crankcase oil for 'top lube' of the apex seals, and that's an understandable choice since most drivers these days don't know how to open the hood.

If the EE20 has been in production for 7 years, you'd expect a company like Subaru to get it rock solid reliable by now. Please post any updates you may find. If it has evolved into a reliable engine, it should be a pretty good (and affordable) fit for 2 seat rv's.

As to the original question: I think a $30K+ price tag (more than the cost of an entire airframe) for an overgrown VW engine that's been around for half a century is insanity from square one. It's really difficult to justify over twice that for a replacement engine design, even if the replacement is a somewhat better engine.

Charlie