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  #21  
Old 07-02-2017, 11:13 PM
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rv6ejguy rv6ejguy is offline
 
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Originally Posted by rv7charlie View Post
How are you estimating the BSFC? Are you accounting for the greatly reduced drag at that altitude?

Numbers quoted at nosebleed altitudes are meaningless to me, and I suspect to 90%+ of other RV drivers. We just don't go there. I know that electronic engine control is more efficient than tractor ignitions and dribble mechanisms, but 10-1 compression is still a lot less than 17-1 (or higher). What would the turbo-diesels being discussed here look like at 17,000 feet?

Charlie
My estimate was from Dave's data knowing his displayed % power and AFR, applied to correct actual % power, came out to 69hp. In the end, doesn't matter what altitude, my point was- is any diesel RV capable of these TAS vs. FF numbers. I was waiting for some numbers from the diesel guys as a counterpoint to prove their assertions. I'd also like to know what a diesel can deliver up high.

Many people blindly believe the diesel is way more efficient than SI simply from the CR difference. The Otto cycle is theoretically the more efficient of the two. Modern CI engines designs have been dropping CRs lately while SI designs have been raising them. There is a diminishing return at very high ratios and pumping losses continue to soak up part of the gains with best BSFC vs. mechanical efficiency occurring around 16-17 CRs.

We must also compare pounds/hp/hr. not gal./hp/hr. to have a more apples to apples comparison.

People need to stop comparing fixed timing, SI engines running ROP with diesels because it's not a valid comparison in cruise conditions.

The fast turning geared diesel almost certainly has higher frictional losses than a DD Lyc. at 2200 rpm. The gearbox maybe sucks up another 1.5 to 2%. The injection pump can use up a percent or more too depending on design.

.33 BSFC sounds pretty amazing for an SI engine doesn't it? R3350s were doing around .37 LOP, 60 years ago with much lower CRs, driving superchargers, without variable ignition timing, without good mixture distribution but with turbocompounding making up some of the other inefficiencies. Really not that much of a stretch at 10 to 1 CRs IMO. Conti 550s are reportedly achieving .37 to .38 LOP with relatively low CRs, fixed timing and no turbocompounding.
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Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 414.3 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm



Last edited by rv6ejguy : 07-04-2017 at 05:31 AM.
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  #22  
Old 07-03-2017, 04:23 PM
kgood kgood is offline
 
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As usual, it's pretty pointless to share info about any new technology on this forum. Even if it is a certified product flying for over 10 years and over 5 million hours. As I've said before, it quickly boils down to bash session against anything that isn't a Lycoming. Much of it coming from folks who have very little or no experience flying diesel aircraft. But - I'll carry on anyway...

To respond to a few previous posts: Yes, the CD155 started out with 300 hour gearbox inspections, then went to 600hr a couple years later, then, two years after that, to 1200 hours. TBR went from 1200 to 2100 hours. Can anyone spot a trend here???

IMO Continental is being careful to make sure the engines are safe as they gain more hours. I appreciate that. So yeah, IIRC my alternator is to be replaced at 1200 hours, as is the HP fuel pump. Not a big deal to me. Traditional engines are not without problems. In just the past year alone, One friend's electronic ignition system gave up after only a few hundred hours, costing thousands to replace. Another friend had an STC'd supercharger on his Cirrus, that failed and cost him over $33k to get back in the air - minus the supercharger after all the problems it caused him. From my study over 35 years of flying, it seems that a significant percentage of "traditional" engines need top overhauls in order to reach TBO. We've replaced the mags twice on our Cirrus, well before TBO. I have a Cherokee that has required two new cylinders before reaching 1000 hours SMOH. And look at all the AD's out there, some pretty serious. While I certainly agree that our traditional engines are super reliable, they are not problem-free, even after 8+ decades of development.

I provided pretty solid proof that aero diesels are more efficient than traditional avgas engines (see the Kitplanes articles) in real world scenarios, side by side testing. Does anyone else have any such testing to prove the "theory" that gas engines are more efficient than diesels in aircraft? If so, I'd like to see it. Not guesses and theories from purveyors of electronic engine management systems. Id like to see side-by-side testing for the entire flight profile, not just hearsay about LOP economy cruise numbers at 17,500'. Most of us just don't fly that high on a regular basis.

That said, I salute those who have the the time, the expertise, and the desire to modify, tweak, adjust, etc, to get great economy out of their traditional engines. That's a good thing.

All I've tried to do here in this forum is to provide info about aero diesels, usually in response to inquiries on the forum. Of course, I'm sharing my experience of over 900 hours flying EAB diesel aircraft. I try not to deal in hearsay or theories.

It's interesting how diesel naysayers love to focus on the initial cost and maintenance costs as if they would never be silly enough to spend their hard-earned funds on the extra cost of a diesel, but have zero problems coughing up untold thousands on panel upgrades, keeping on the cutting edge with the latest in electronic wizardry, none of which will do much good when the engine quits... What about paint jobs and interiors? Same thing. Truth be told, owning and flying an aircraft is not cheap, and each of us decides where best to spend our "plane money". I'm one who chooses to spend on power plants that I consider to be the up-and-coming thing. I may be proven wrong, but in the meantime, I have enjoyed experimenting with diesel power and sharing what I've learned with others.

Kurt
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  #23  
Old 07-03-2017, 05:59 PM
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rv6ejguy rv6ejguy is offline
 
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Originally Posted by kgood View Post

I provided pretty solid proof that aero diesels are more efficient than traditional avgas engines (see the Kitplanes articles) in real world scenarios, side by side testing.

All I've tried to do here in this forum is to provide info about aero diesels, usually in response to inquiries on the forum. Of course, I'm sharing my experience of over 900 hours flying EAB diesel aircraft. I try not to deal in hearsay or theories.

Kurt
Was this the article on your WAM powered RV9 which we already discussed several years back and several Lyc engined RV9 users already posted they were getting similar FF vs. TAS with their 235 and 320 Lycs running LOP as you with the diesel? The flight comparison did not include running the Lyc LOP nor did it have the latest in engine controls. If you want to say that a diesel gives better BSFC than a mag equipped Lycoming running ROP, I'll absolutely buy that assertion but this test was not a fair one on what a Lycoming is capable of in these days which is what my post above was saying. It's well documented that LOP operation can improve FF vs. TAS a minimum of 15% on Lycomings even with fixed ignition timing compared to best power mixtures. In cases with everything fully optimized 20-25% lower fuel burn is not uncommon. I don't think Dave Anders is making up the 40ish mpg claims on his RV4, nor do I think that something over 1800 aviation customers make up stories of noticeable fuel flow reductions using EFI/EI running LOP.

In a VAF thread on RV9/A performance in 2010 you reported 139 KTAS on 33.5 pph on your -9, Pete Howell with a 9A, reported 150 KTAS at the same altitude on 36 pph and 144 KTAS at 12,000 feet on 28.8 pph with a carb, 2 EIs and a CS prop. I just don't see the "much lower fuel burn" you claim with your WAM when the Lyc is operated using the latest LOP techniques.

We all appreciate real life experiences with products here but with regards to your WAM experience, you only told us the good points, not the bad ones. It led me and others to believe that the WAM was an amazingly well engineered, low production alternative at an amazing price, performing well with little or no attention on your part. When Dan Horton pressed you however, we finally got the real story- premature removal and return to the factory to address a significant loss of compression, frequent replacements of expensive pre-chambers and other internal failures in the field from other users, apparently as the result of torsional vibration issues.

Real world means ALL the facts, not just the ones that suit your side of the discussion.

I was hoping you'd report the FF vs. TAS on YOUR Glastar in cruise- at any altitude, so we might compare to SI powered ones running LOP with the latest engine control technology. I just posted the Dave Anders numbers as reported to me.

Is it really a stretch to take a known SI engine BSFC figure (Conti IO-550)- 8.5 CR, fixed timing not optimized for LOP operation, not so good mixture distribution with untuned exhaust and improve it around 10% by adding 1.5 points of compression ratio, optimized mixture distribution, superior fuel atomization, proper tuned exhaust and ignition timing optimized for the slower LOP flame speed?

In 2016 Toyota achieved 40% TE on their latest SI hybrid engine, bettering most diesel competitors and these had also been rated at higher highway mileage than comparable diesel competitors. In 2017 they have introduced other engines which are even slightly better and are aiming for 45% by 2019 and 50% by 2025. http://newatlas.com/toyota-tnga-engines/46830/ Both Toyota and Mazda are building production SI engines with 14 to 1 CRs.

Just to be clear here, I don't fly a diesel or a Lycoming. I'm just interested in the actual facts.

Like it or not, initial acquisition costs are an important consideration to overall cost per flight hour on a chosen powerplant along with standard maintenance items and fuel burn if we want a true picture of what it should cost to fly that engine 1000 or 2000 hours.

I agree, not all Lycomings or any other engine, may go to TBO without replacing some expensive parts. Mechanical things can and do break. These costs would be added our other basic costs above based on our actual running experience with a particular engine as we flew it over that time period.

A run down of your expenses on your CD155 to date would help us compare those aspects to a typical Lycoming installation.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 414.3 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm



Last edited by rv6ejguy : 07-04-2017 at 05:46 PM.
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  #24  
Old 07-04-2017, 12:05 AM
dlomheim dlomheim is offline
 
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Default R3350's...

Quote:
Originally Posted by rv6ejguy View Post
...R3350s were doing around .37 LOP, 60 years ago with much lower CRs, driving superchargers, without variable ignition timing...
Ross: Just curious: Do you know if your ".37 LOP" number was derived from an R-3350 that was equipped with three Power Recovery Turbines (PRTs)? My dad flew EC-121s (in the USN), and he told me that each PRT would return about 150 hp (450 total) which normally was dumped overboard...

Doug Lomheim
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  #25  
Old 07-04-2017, 05:35 AM
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rv6ejguy rv6ejguy is offline
 
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Originally Posted by dlomheim View Post
Ross: Just curious: Do you know if your ".37 LOP" number was derived from an R-3350 that was equipped with three Power Recovery Turbines (PRTs)? My dad flew EC-121s (in the USN), and he told me that each PRT would return about 150 hp (450 total) which normally was dumped overboard...

Doug Lomheim
Yes. These were the later engines which also had direct injection. My Dad flew the Canadian Argus ASW aircraft with the same basic engines. PRTs were jokingly referred to as Parts Recovery Traps. I think these engines only had a CR of 6.85 to 1 too which didn't increase their TE but the PRTs made up for that compared to other engine types.
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Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 414.3 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm



Last edited by rv6ejguy : 07-04-2017 at 05:48 AM.
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  #26  
Old 07-05-2017, 12:11 AM
weissfamily97 weissfamily97 is offline
 
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Default Very Interesting

Thanks to all for the responses.
Some of it was very insightful, and much of it was unexpected!

While it's difficult to sift through everything, here are my takeaways:

- Continental for some unknown reason is not making this engine available for experimental use yet. If they do, it would be great for them, and for us.

- Fuel flow *should* be better than equivalent Avgas engines. Numbers from the new Cessna 172 seem to confirm what Kurt is seeing. Also, when you look at automobiles, TDI engines get better mpg than gas. I don't think that's really debatable. Even if fuel flow ended up being similar, the cost of Jet-A is so much less than 100LL, and way more available than Mogas (for my intended destination airports). I think it's a great solution.

- Initial cost of the CD155 is super high, which is why I petitioned Continental for an experimental version (still no reply). For me, unfortunately, it's probably prohibitively high at this point. But I'm not ready to start building yet, so I'll keep an eye on it.

- This really got me thinking...if I can't get an affordable diesel, maybe I'll look into a "low cost" complete ECU solution for an (I)O-360? Maybe even develop my own? Is there an (I)O-360 injector/spark control solution available?

Thanks again everyone for the comments...
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  #27  
Old 07-05-2017, 07:18 AM
tspear tspear is offline
 
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Quote:
Originally Posted by weissfamily97 View Post
- Initial cost of the CD155 is super high, which is why I petitioned Continental for an experimental version (still no reply). For me, unfortunately, it's probably prohibitively high at this point. But I'm not ready to start building yet, so I'll keep an eye on it.
I tracked down and talked to Continental staff; the decision was made at an executive level that for now, all diesel sales must go through the airframe manufacturer. So you would have to convince Van's. If you get Van's to listen, I know who they should deal with at Continental.

Tim
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  #28  
Old 07-05-2017, 07:24 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by weissfamily97 View Post
Thanks to all for the responses.
Some of it was very insightful, and much of it was unexpected!

While it's difficult to sift through everything, here are my takeaways:

- Continental for some unknown reason is not making this engine available for experimental use yet. If they do, it would be great for them, and for us.

- Fuel flow *should* be better than equivalent Avgas engines. Numbers from the new Cessna 172 seem to confirm what Kurt is seeing. Also, when you look at automobiles, TDI engines get better mpg than gas. I don't think that's really debatable. Even if fuel flow ended up being similar, the cost of Jet-A is so much less than 100LL, and way more available than Mogas (for my intended destination airports). I think it's a great solution.

- Initial cost of the CD155 is super high, which is why I petitioned Continental for an experimental version (still no reply). For me, unfortunately, it's probably prohibitively high at this point. But I'm not ready to start building yet, so I'll keep an eye on it.

- This really got me thinking...if I can't get an affordable diesel, maybe I'll look into a "low cost" complete ECU solution for an (I)O-360? Maybe even develop my own? Is there an (I)O-360 injector/spark control solution available?

Thanks again everyone for the comments...
As has been discussed, Continental is taking a careful, measured approach which is prudent given the past diesel introduction problems with Thielert, SMA, WAM etc. They want this to go smoothly. Once they are satisfied all is right, you may see more being offered for Experimentals. The Glastar project was step in that direction and I say kudos to Continental for that. I'd be surprised if the price drops much though. They have a lot to recoup and it's a certified engine to boot. They'd have to drop the prices across the board. I don't believe these engines will ever be offered directly to homebuilders as Lycomings are.

My point with various posts on fuel flow was that useful (more than 10%) diesel fuel savings are only there when comparing against SI engines operating ROP which you don't have to be doing. EI equipped Lycomings operating LOP can virtually match the cruise FFs of the existing aero diesels. I've provided some examples.

Taxi and climb use very little mission fuel in an RV and with EFI, we can cut that portion down some more, especially using LOP in the climb portion. Comparing a Lycoming being operated with old school techniques as in the test mentioned, is not valid in my opinion. Test both engines using the best possible techniques for each.

Actually, the very latest SI auto engines are now matching or exceeding their diesel counterparts in thermal efficiency and highway mileage while also truly meeting their emissions targets. Many diesel manufacturers are now turning their backs on diesels after the VW fiasco in favor of electric and electric/ SI hybrids. SI engine development has made very fast progress in the last few years , witness Mazda SkyActiv and the Toyota developments mentioned.

Use a diesel if that's your desire or passion as it is for Kurt. I totally get that. But look at the cold hard numbers if you're looking to save money as a result of that decision. Initial acquisition costs are real and part of the equation. These tie up a chunk of investable cash right from the start which won't be recovered in the first 1000 hours for most folks flying cross country trips. That's about 10 years of flying for your average RV flier. If you're pattern flying like in a flight school operation, payback would be much quicker and makes sense. If you fly in Europe or somewhere where avgas is hard to get or much more expensive, the diesel makes great sense again.

I'm glad to see Continental take this engine more mainstream, support it and develop it further. Choices are important in the market, especially in places where avgas pricing and availability are not like it is in North America. Some of my friends in Europe pay quadruple what we do here for avgas making a $100 hamburger flight not worth it in most cases.

Jet fuel availability at many small airports is not as good as avgas here but certainly available enough not to impact most route planning too much.

All engine choices have their advantages and disadvantages whether those may be price, hp, weight, fuel burn, reliability, availability and support etc. I'd be researching all aspects well before spending $30-$60K on any of them.

If you decide to go the Lycoming route, you have 3 basic choices for integrated EFI/EI systems- Eagle EMS, EFII and SDS. You can also go conventional with Bendix type FI and a variety of EI systems. You can see these work well for many people too. Look at each one yourself, contact the vendors and users, compare and decide for yourself which route suits you best.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, Marcotte M-300, IVO, RV6A C-GVZX flying from CYBW- 414.3 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi.htm



Last edited by rv6ejguy : 07-05-2017 at 10:45 AM.
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  #29  
Old 07-05-2017, 10:14 AM
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Lower fuel consumption, price and availability are not the only reason for diesels.

I have close to 100 hours on different AC with Thielert and Austro engines now, what they all have in common is that they vibrate way less than the best balanced Lycoming.

Have not heard about the UL-power RV-7 for weeks now so my RV14 will get an IO390 as its first engine, I hope there is a diesel or electric-hybrid alternative for when it is time to change.
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  #30  
Old 07-05-2017, 10:55 AM
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RVbySDI RVbySDI is offline
 
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Originally Posted by tspear View Post
I tracked down and talked to Continental staff; the decision was made at an executive level that for now, all diesel sales must go through the airframe manufacturer. So you would have to convince Van's. If you get Van's to listen, I know who they should deal with at Continental.

Tim
Not quite sure how that would play out. Vans is NOT the "Airframe Manufacturer". We are!
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