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Continental CD155 for RV-9A?

Can someone help me make sense of some of the data I'm seeing?

Cessna offers the 172 with a 180hp IO-360, as well as now with the CD155.
The CD155 is of course rated at 155hp.
From their book numbers, the traditional C172 has a max cruise of 124kts, and burns roughly 10gph of 100LL.
The Turbo Jet-A C172 cruises at 134kts (on less horsepower) and sips roughly 7gph of Jet-A.

That's significantly better performance (8% increase in cruise speed), for significantly less cost per hour (7 gph x difference in 100LL/Jet-A).

So, taking a leap of faith, in a -9A would it be safe to assume that using the CD155 instead of an O-320 would yield similar cruise speed enhancement? Fuel burn would be similar (only a little better), but you could take advantage of using Jet-A/diesel.

Has anyone done this yet for a -9/9A?
It seems like it might be a good fit (aside from price)...weight is similar.
 
Turbodiesels are inherently more fuel efficient than our standard old-school Lycoming engine (with the exception of the newer FADEC injected ones) so the improvement in efficiency is not surprising. The improvement in speed is going to be another issue entirely, as that is going to be strictly a function of horsepower into the prop, prop efficiency, and aircraft drag. Cessna may have made quite a few other changes to the Jet-A model besides the engine.

As for doing it in a 9A, I would have one in mine today except for the ludicrous price of the CD155. I can buy an awful lot of 91E10 autofuel for my IO360 for the cost differential.
 
funny you bring it up. I started looking at this question. Different config before I actually started building and even asked Vans and Austro engines about it...

The AE300 diesel at 170HP that is used in the diamonds is crazy reliable so far and has a far better track record than the Continental... but either way. The price of one of these engines is north of 65K and that is again a whole lot o Fuel. Not to mention Vans has a great design and if you go with alternative engines you are likely to extend build time by a few years....

Sad really I thought the RVs could be truly great platform.
 
Diesel Experimental

The price of one of these engines is north of 65K and that is again a whole lot o Fuel. Not to mention Vans has a great design and if you go with alternative engines you are likely to extend build time by a few years.... Sad really I thought the RVs could be truly great platform.[/QUOTE said:
For the IO-series, the experimentals are considerably less expensive than the certified versions. With that in mind, I did email Continental to see if there was any chance of adding experimental versions of their diesel engines. I haven't heard back yet.
 
Kinda two words, altitude & turbocharger

Since diesels will use higher compression ratio and the intake system is not throttled, they are limited on cylinder pressure. Turbocharging will allow the engine to be flat rated for some altitude yielding better power than the normally aspirated Otto cycle engine.

The diesels are have a box limit for cylinder pressure, exhaust temperature, and turbo speed. PCP on the ground, and either Ex-temp or turbo speed at altitude depending on the ambient temperatures.

All RV's fly pretty close to Vne, so allowing higher speeds with turbocharging might not get you much within the envelope. Starting with a 120hp turbo, now that is a different story.
 
Well, Continental does also have the CD135 (135hp).
Maybe that would be a better (more fuel efficient and less expensive) option?
I suppose that's kind of what I was implying in my original question.
Could you achieve similar/better performance with the CD135 vs an O-320?
 
Cost and weight

Take a close look at all the numbers.

I have an O-360 in my -9 and can cruise at 150 to 155 knots while burning around 7 GPH +/-, depending on the conditions, at 50 to 60% power.
75% cruise is right at 175 knots, if I want to pour that much fuel in it.

Up high I have seen as much as 159 knots while burning 5.2 GPH. While I would really like a diesel, at this time, I don't see the advantage of having one.
 
Welcome aboard!

Adam, welcome to VAF.

Any idea of the weight difference in the engines? Seems that could be a big factor....
 
Thanks Mike!
As near as I can tell, the diesels are about 20lbs heavier than a Lycoming O-320.
So, not too big of a deal.

Bill R. - thanks for sharing your numbers.
I was wondering if you could put an (I)O-360 in a -9/9A, as it's not shown on the website, and they specifically have a "why can't I put in a bigger engine" section.
Your 75% cruise (175kts, 201mph) puts you over the Vne.
Isn't that a concern?
I'm really new to Vans aircraft, so I'm really curious.
 
Bill's numbers are just a few knots better than mine, he has apparently done some better work than I have on drag reduction. In my case I don't ever cruise low enough to see 75% power in cruise, except during occasional goofing-off sessions, but yes you can approach Vne at low altitude where the engine can make good power.

At higher altitude in the mid-teens, the lower ambient pressure will put you in the 50%-60% power range and take the edge off the top end of the TAS, I typically cruise at 155 KTAS in the 14k-17k range burning 6.0-6.5 gph. Approaching Vne in cruise at those altitudes is not a problem, but on descent you definitely have to pull back the MAP to keep the airspeed in control.
 
Boat Anchor

The Thielert/Continental diesel design is based on the Mercedes diesel but uses a purpose built aluminum block. The Austro uses the Mercedes cast iron block and is much heavier. Seems to be more durable too, but Diamond had to beef up structure and increase gross weights to get the useful loads on the diesel DA40's and 42's back up to a reasonable level.

The Continental engine has a TBR, the Austro a TBO. Not sure if either applies to Part 91 and/or the experimental world.

The latest iteration of the Austro has higher power output but I think it's basically the same core engine with a bigger turbo and more boost. Not sure if it will have the same durability or longevity.
 
Here we go...

To answer the OP's question:
Yes, the CD155 would make a great engine for an RV9.

ON this forum you'll get all kinds of reasons why a Lycoming is better, but since you asked, I'll share my experience with the CD155. I now have 412 hours on my CD155 - powered Glasair Sportsman.

Dan is right, the numbers Cessna is quoting work because the CD155 makes full power to 9000', and only tapers off very slowly after that. It is a joy to fly behind.

A few facts: It is much more efficient than a Lycoming, FADEC or otherwise, especially when you consider the whole flight profile. If you'll check Kitplanes June 2015 issue, an apples-to-apples comparison was done between to similarly equipped Sportsman aircraft. Both perform similarly, but the diesel uses 1/3 less fuel. Depending on the mission, the CD155 can pay for itself easily even though the initial cost is higher. See Redbird's Redhawk website. In training scenarios, the savings are substantial. I know most of us don't fly like that, but if we use the plane a fair amount, we'll save.

It is much simpler to fly: Start it like your car. One lever controls everything. Set it for the % power you want, or fuel burn, and leave it there. If you haven't flown one before, you'll be amazed. SO simple. No leaning, no carb heat, no worries about shock cooling, no mixture, no prop control.

Compared to a similarly equipped Lycoming-powered plane, the installed weight of the CD155 will heavier, probably as much as 60-70 lb. Mine was about 90 lb heavier, but as Glasair has developed the installation package, they have reduced the weight. BUT - you can fly as far as your Lyc-powered friends with 60-70 lb less fuel on board, so you haven't lost anything. But when you want to go with a lighter payload and full fuel, you can go forever. I've flown 8 hour legs in my Sportsman with plenty of reserve.

Safety: one of the main reasons I fly Jet A. The fuel is much less volatile than 100LL or Mogas. Too many people are burned after surviving a crash. Diesel or Jet A gives a much better chance for reduced injury...

For now, I think this is all a mute point as far as the RV9 goes, because last I heard, Continental is not willing to sell these engines to homebuilders. The only way we were able to do it with the Sportsman was to make it available through the TWTT program, installed with factory supervision. It's not terribly complicated, but it's certainly not a known quantity like the Lyc is. The only way that we can get one is for Van's, or possibly some customer-assist center, to work with CMI and develop a package to be installed with assistance. We all know that Van's has no interest in doing this. I can't say I blame them, but I bet that some of their overseas customers would be interested, since the savings would be much greater for many of them...

Kurt Goodfellow
RV9 flying since 2008, Wilksch diesel, 560 hours.
Sportsman flying since 2014, CD155 diesel, 412 hours.
 
A few facts: It is much more efficient than a Lycoming, FADEC or otherwise, especially when you consider the whole flight profile.

You may be behind the times and I'd question your "facts". I'm doubtful that it's much more efficient than a Lycoming with FADEC and programmable EI running LOP. Dave's 10 to 1 CR IO-360 RV4 numbers at 17,500 feet:

145 KTAS on 22 pph.
181 KTAS on 33 pph.

We estimate the BSFC is better than .33 lbs./hp/ hr. running LOP at 2200 rpm. As good or better than what the Austro AE300 claims for their cruise BSFC.

The savvy fliers are running lean on the ground and even in the climb with the EFI/EI when doing cross country work. Some even report running LOP during formation work. LOP drops the CHTs down while burning less fuel.

Several other RV9 fliers here with less sophisticated fuel and ignition setups have posted sub 5 GPH fuel burns at 135-145 KTAS in the past with 235s and 320s running LOP.

Flying school use where the Lyc is near full rich for most of it's life in the pattern, yup, gonna save a lot with a diesel. In cruise with modern electronic controls running LOP, nope, little or no significant savings there with US gas prices. In Europe, a different story of course.
 
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Given time, we'll see CD155's in kit aircraft. Continental is just being cautious, as they have cubic dollars tied up in the program, and it's doing well on the certified side. In comparison, EAB is the Wild, Wild West....rugged individualists and all that rot ;)
 
Nervous

While it's an interesting idea, liquid cooled engines make me nervous (apologies to all you Rotax drivers out there). I think suitable lead free AV gas replacements are on the horizon.
 
Why would you be nervous about a liquid cooled engine? How many aircooled cars are produced today?

Back to the Conteinental/Technify engine, the engine will be significantly heavier than an (I)O-320 or 360, I would guess 50lb, may be more. Now go look at the servicing requirements. Look at the component replacements required every 300 or 600 hours. On new engines the gearboxes are now 1200 hours (used to be 300), but there are other components that need to be changed, alternators, rail pressure control valves, HP and LP fuel pumps, and so on. Sure not required on an experimental, but ... The next question is getting Continental to sell you a motor, replacement motors sell for around Euro 35K, but they are only available from the factory and usually not to individuals. Spares are only available to Technify service centres, as are the service tools - for example to Canbus interface tool to interrogate the FADEC.

The Austro engine is heavier again - as a previous post said it has an iron block - now look at the component replacement schedule, particularly for the 180hp engine. How does a new cylinder head every 300 hours sound? Sounds expensive to me!! That number will increase as the engine accumulates time in service but ...

Right now both these manufacturers are concentrating on certified aircraft and don't seem very interested in selling to the experimental market (except the Glastar program). At first sight may seem like a reasonable option, but I think you will be $10 or 20K out of pocket on the initial install and possibly another $10K out of pocket after 1000 hours thereafter due to component replacements. Reduced fuel burn is not going to make up that difference.

Pete
 
Wow, very interesting. Thanks Penguin for bringing those details to light. That information always seems to be hidden away in the servicing manuals of aero diesels. Naturally, these things are rarely mentioned by the diesel advocates.
 
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You may be behind the times and I'd question your "facts". I'm doubtful that it's much more efficient than a Lycoming with FADEC and programmable EI running LOP. Dave's 10 to 1 CR IO-360 RV4 numbers at 17,500 feet:

145 KTAS on 22 pph.
181 KTAS on 33 pph.

We estimate the BSFC is better than .33 lbs./hp/ hr. running LOP at 2200 rpm. As good or better than what the Austro AE300 claims for their cruise BSFC.

snip

Flying school use where the Lyc is near full rich for most of it's life in the pattern, yup, gonna save a lot with a diesel. In cruise with modern electronic controls running LOP, nope, little or no significant savings there with US gas prices. In Europe, a different story of course.

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
 
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 think it probably happens quite a bit more than you suspect - speaking for myself I know that about 2/3 of all my flight hours in my 9A are above 15,000'. Granted, I do more lengthy cross-country trips than most, but the airfoil on the 9 just gets so darn happy up there. I flight plan 150 KTAS on 6.0 gph in the upper teens, it's a great place to cruise.
 
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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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
 
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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R3350's...

...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
 
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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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...
 
- 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
 
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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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!
 
Yes; and how is that different from Glastars?
Not sure why the question. I don't see it as any different. Just saying that erroneously thinking that Vans is the "Airframe Manufacturer" will most likely get no where with Continental in the context of this thread's conversation.
 
Not sure why the question. I don't see it as any different. Just saying that erroneously thinking that Vans is the "Airframe Manufacturer" will most likely get no where with Continental in the context of this thread's conversation.

Actually, I should have been more precise. Continental will only work with the kit manufacturer at this point. They are not interested in the "wild west" of anyone just buying the engine and installing it.

Tim
 
To answer a few of Ross's questions: The testing done on my RV9 in 2010 was an actual side by side test against Van's factory RV9A with CS prop. It was conducted by a professional (Ken Krueger, Vans Chief Engineer, who I suppose would know a thing or two about testing aircraft). He does not mention in the article whether or not the factory 9A was running LOP in the "economy" test. However, as we were readying to do the test, he said: "this test is for best fuel economy. You use every trick you know to get the best economy out of your plane. I am going to do the same". My guess is, he would have done exactly as he directed, and would have run LOP. Of course, I could employ no "tricks" to improve my economy. For me, it was simply setting climb power for climb, cruise power for cruise, and landing when we were done. We both flew side by side, same day, same route. APPLES to APPLES. I achieved 33.2 Statute MPG and He achieved 23.9 Statute MPG. The trip was 166 Statute miles, covered at an average ground speed of 149 Statute miles per hour. And this was done with a diesel that is not as efficient as the Conti CD155. Were conditions "just right" for me and not for him? I have no idea.

Here again, this was not: "so-and-so reported getting XX fuel burn at XX altitude one day". I've come to believe that we pilots are somewhat like fishermen when we share our speed and fuel burn figures. How often in these very forums do we read "flying along at XX altitude, I've seen XX speed and XX fuel burn"?. What "I've seen" is really not a clear picture of what that particular aircraft or power plant actually does on a regular or average basis. I hope you get my drift here. I think most of you will.

If you read the article about the more recent test Ken did, you'll find that most of your questions are answered. The test was between a very light, well built Sportsman and my Sportsman (not so light, and not as well-built:)). The gas Sportsman had a Superior O-360 with one Lightspeed electronic ignition and one mag, turning a two blade Hartzell CS prop. In Ken's words: "This aircraft turned out to the ideal choice for the gas-to-diesel comparison because the airframe is completely standard and is likely the lightest Sportsman around". In this test, both aircraft were tested for economy and speed at different altitudes as follows, and I will only include the LOP figures because that's all you seem to be interested in.
Gas: Full Throttle and 2500 rpm cruise:
135 KTAS @ 5600' DA LOP 9.6 GPH, 14.1 NMPG
130 KTAS @ 9500' DA LOP 8.8 GPH, 14.8 NMPG
129 KTAS @ 11,800 DA LOP 8.2 GPH, 15.8 NMPG
Diesel 75% power cruise:
123 KTAS @ 5000' DA 6.0 GPH, 20.5 NMPG
126 KTAS @ 9500' DA 6.0 GPH, 21.0 NMPG
130KTAS @ 11,500 DA 6.1 GPH, 21.4 NMPG

I know that the next thing you're going to say is that the gas plane was not equipped with the latest electronics, and that with the finest technology, it would have bested the diesel. I have still seen no proof of that, and I think that most would agree that the this plane represents a fairly high percentage of traditional engine-equipped planes out there.

To address your Toyota Hybrid scenario: yes, Hybrids are inching ever closer to diesel economy, but it takes the assistance of batteries to do it. And look at all the extra cost, not to mention environmental waste, weight, and complexity associated with Hybrid solutions. I know there are those pursuing hybrid technology for aircraft, but that's another subject for another day...

If there are gas aircraft out there with better average economy than a diesel, I have not heard of them. It might be that there simply aren't enough FADEC gas aircraft out there and no one has actually tested them against comparable diesel aircraft. BUT - if we go to the automotive world, there certainly has been. Take the Ford F150 Ecoboost against the Dodge 1500 Ecodiesel. I happen to own several of the Fords (for my work) and one of the Dodges (my personal transportation). Unofficially we have compared the two in same-way conditions on the freeway between here (NV) and our Utah office. At freeway speeds, not babying either truck for fuel economy (just setting cruise at 77mph), we struggle to average 20 mpg with the smaller 2.7 Ecoboost. Even worse with the larger 3.5 engine. The Ecodiesel averages 27 mpg. But don't take my word for it. A quick look at Fuelly.com shows that, averaged over millions of miles, hundreds of owners, and all types of driving, the F150 Ecoboost averages 16.6 mpg. The Dodge Ecodiesel averages 22.7. Can we agree that both Ford and Dodge are employing the very latest in electronic engine management, maybe even more advanced that what we see in the EAB aircraft world??? Of course, the Ford has it's 700-lb-ligher aluminum body, which should give it leg up. If gas engines are do darned efficient, I wonder why Ford has announced a 3.0 diesel F150 for 2018??? Silly truck manufacturers:) I wonder why Cessna, Piper, Diamond, and Robin all currently offer diesel models, and Cirrus, Mooney, and others are developing diesel models? Could it be that they see a market for these products? Maybe they don't know what you know....

I understand that initial cost plays a huge part in overall cost to own and operate an aircraft. However, I won't share my initial cost; I don't know it! And because it does not even remotely represent what's available today. Because i was a first adopter, a developer of the CD155 FWF for the Sportsman, I had a LOT of costs that would not need to be spent today by someone installing a CD155. For example, we (Glasair and I) ordered an entire Cessna 172 conversion kit, figuring we would be able to use most, if not all of it in the Sportsman. We ended up using very little of the kit and now i have many thousands of $$$ in parts in my hangar that are of no use to me. This, along with all of the money spent to develop new parts. I also purchased tools and diagnostic equipment unique to the CD engine so that I can service it myself. Best as I can tell, and this is pure speculation, the premium for the CD155 should be no more than $15-20K over and above a Lycoming o-360/CS FWF package. The delta should be even less when comparing to a certified Lycoming engine/prop, which would be an apples-to-apples comparison. Of course, as the market matures and gets more comfortable with the diesel, that cost should go down. Hopefully it will.

As far as cost of ownership goes, this engine so far, at 420 plus hours, has cost me nothing, other than 100 hour oil changes (an oil changes runs about $200 in costs, with filters, oil, etc.), and fuel. Over the lifetime of the engine, there will be one gearbox inspection, (i'm not sure of the cost, but I think around $2500-3000), and a fuel pump, I think around $1200. As has been mentioned, as EAB, I'm under no obligation to follow these guidelines. When I was at the factory seminar, our instructor told us of operators who had received permission from their government (New Zealand IIRC) to run far beyond the mandated limits, with no issues. According to Ken's article, based on cruise alone, not factoring in taxi and climb, and all else being equal, it is $22.95/hr cheaper to fly the diesel Sportsman. Over the life of the engine, assuming current fuel price delta, that equals a $48,195.00 savings. Yes, some of that will be spent on maintenance, and you've spent maybe half of it on initial cost. But, considering the fact that the Lycoming will also most likely require maintenance, I think it's safe to say that you can still save money owning a diesel. Even if it's a wash, you've flown in a safer plane, and you've enjoyed its simplicity of operation. I do understand that there are many ways to "do the math", and frankly, I don't care. I enjoy developing and flying diesels and I know they're more efficient. Do the math the way you want...

There have been two service bulletins in the 3 1/2 years I have owned this engine: the first was to add a plug-in starter circuit mod in the starter loop and install engine software update. No cost. The second was to install a pin to alleviate a wear issue that some were experiencing on the turbo wastegate shaft. Mine had no such wear, but I installed the pin anyway. The factory provided the parts and a fixture. The fix was simple; took about 45 min.

I am hoping to replace the WAM in my RV9 with a CD155 in the near future. I think it will make it a good performer compared to a "standard" RV9, high-tech or otherwise. It will be interesting to find out if I'm right...

Kurt
RV9 WAM 120 diesel 560 hours
Sportsman CD155 420 hours.
 
Talk to Vans?

Kurt,

It's really exciting that you're looking to put a CD-155 in your RV-9. I'd love to hear how that works out for you!

As part of the process, would you reach out to Van's about this, and perhaps start the conversation between them and Continental?

Thanks for sharing your Ford/Dodge anecdotal data. That confirms what I've been thinking. Car manufacturers are using the best EFI they can for both, and diesels still seem to be more efficient (except for Hybrids, as mentioned, but that's a whole different animal).

What started my interest in posting this thread was seeking:
- Simple operation (complete FADEC)
- Lower fuel consumption and price of fuel

And btw - if you ever do put that CD-155 in your RV-9, I'd love to come for a ride!!!
I've got family in NV and UT, and used to fly out of KMEV
 
CAFE Foundation Data

An oldie, but an interesting read on the gas side.. CAFE got some really good numbers out of the factory -9A with what sounds like very strict procedures. I wish they had published a 150 smph low power cruise and that my plane could beat the CAFE numbers!

https://cafe.foundation/v2/pdf_cafe_apr/rv-9a.pdf pages 7,8,9

A LOP, 150 mph cruise, powered by ~$2.25(after rebates) mogas satisfies my frugality needs. We used it to fly for burgers and(for my wife) beers in
Wisconsin tonight! (Dan - we to find a way to get the Leinie's Runway Ale for the social)

I keep saying I'll replace the carb, but my economy is good already- maybe someday, but carb heat is what I use to run LOP.

Kurt - I'd love to see more pics of the diesel on he -9A. Please keep innovating!
 
Kurt:

Good things - your comparison of the diesel vs gasoline by comparing "tank mileage" that include all phases of the operation. Having spent a decade doing/reviewing comparisons of the same for Class 8 trucks (competitor engines) and also looking at dyno controlled point by point data. The real world has all the variables accounted, not corrected in them (the ones we know). Side by side, warm up, taxi climb, cruise, descent, taxi and refill is the best way to compare the fuel efficiency units. But don't just use gallons, or lbs, use energy (BTU) as the basis. Energy would make your comparison ~19% better for your diesel. Economics is a whole different dissertation.

If you could provide some location for the article, it would be appreciated.

Bad things - forget about any combustion cycle comparison with cars-trucks to further any efficiency case. The operating cycles are hugely different. Not worth more words except to say, don't. Ever.

Pete: Getting to $, Like the real world cost/mile with mogas. Looks perfect for local operations. I just looked at low$ 100LL today to high$, in the same area, the high is 42% higher price. WOW
 
The economy factor is something that at least some of us can't ignore. I don't fly enough to even justify owning a plane. But if I did fly a lot, diesel really would make a lot of sense. I can have my on fuel supply on my field if I desire, and off-road diesel is easy to get. Recovering the taxes on mogas is a convoluted process in my state, but 'farm' diesel can be bought without the road taxes.That, combined with costs that are lower than even E-free mogas, and real world fuel burn numbers that are going to be better than gas, means real $ per mile differences.

For a fair comparison, I want to see some *diesel* numbers on Dave Anders' -4 after a couple of decades' worth of cooling drag reduction work. We shouldn't forget; that airframe was at least 40 statute mph faster than the typical -4 on the same fuel burn, *before* he started playing with electronic engine control. I wonder if that could contribute to its fuel efficiency.....
 
As a Sportsman owner I've been following Kurt's progress with great enthusiasm. I would LOVE to own a diesel but obviously am far too late to participate in the Glasair TWTT program that would allow me to actually obtain an engine. And I've already got a brand new certified Lycoming and Hartzell on the airframe. Bad timing on my part, by about a decade... LoL

Thanks, Kurt, for sharing the lessons learned in a thousand diesel-powered hours of flight.
 
A point of consideration.
To match performance, you ideally would want an TIO-320 160HP engine.
But I cannot find any such exists. The closest, seems to be a 180HP or 200HP IO-360 depending on if you are trying to match cruise at roughly ~10K or ~20K.

Going on memory since I am feeling too lazy to look up the numbers.
The FWF package on the C172 is 54K.
Compared to a Superior IO-360 is 35K, plus you need to spend ~6K on parts for the EFI systems, and likely another 6K for a shop to install/tune it for you (I asked two shops with dyno/test stands the estimate to install an EFI on an IO-540, came in at 8K in labor, so I guessed 25% cheaper).

That means you are likely comparing 54K for a CD-155 versus 47K for an IO-360.

When you look at the Sportsman pricing, you now see they no longer offer a premium price for the diesel, it is the same price.

Therefore, the price delta between the engine choices is declining...

Hopefully someone can do a little research and get more accurate numbers.

Tim
 
Why would you be nervous about a liquid cooled engine? How many aircooled cars are produced today?

Because virtually every break-down I've ever had with a car has been due to a problem with the cooling system - hose, pump, radiator.

I read someplace that nearly every P-51 that went down in WWII with engine trouble was the result of the cooling system getting compromised. There's a good reason airplane engines are air cooled. They follow the KISS principal... :D
 
Because virtually every break-down I've ever had with a car has been due to a problem with the cooling system - hose, pump, radiator.

I read someplace that nearly every P-51 that went down in WWII with engine trouble was the result of the cooling system getting compromised. There's a good reason airplane engines are air cooled. They follow the KISS principal... :D
I agree with you that KISS is indeed a good idea, and it doesn't get much simpler than air cooling (if you don't count the but baffling issues).
Eventually, though, you have to deal with the limitations of any system. When was your last cooling system problem? Just curious. The last time I can recall having a cooling system related issue with any vehicle I have owned was when our kids were in high school, when a water pump on an old and very poorly maintained Toyota we bought for them to drive disintegrated internally. Yes, I used to have a lot more problems when we were young and dirt poor and ran radiator hoses until they burst, then used duct tape to patch them. Not so much as a leaky radiator cap since, oh, about 2002. Maybe I've just been lucky.

Since no one is shooting at my RV-12 and materials have gotten a little better since the 40s, I'm not so worried about the P-51's problems.

Even Harley-Davidson is moving to water cooling. Slowly, but they're doing it.
 
I agree with you that KISS is indeed a good idea, and it doesn't get much simpler than air cooling (if you don't count the but baffling issues).
Eventually, though, you have to deal with the limitations of any system. When was your last cooling system problem? Just curious. The last time I can recall having a cooling system related issue with any vehicle I have owned was when our kids were in high school, when a water pump on an old and very poorly maintained Toyota we bought for them to drive disintegrated internally. Yes, I used to have a lot more problems when we were young and dirt poor and ran radiator hoses until they burst, then used duct tape to patch them. Not so much as a leaky radiator cap since, oh, about 2002. Maybe I've just been lucky.

Since no one is shooting at my RV-12 and materials have gotten a little better since the 40s, I'm not so worried about the P-51's problems.

Even Harley-Davidson is moving to water cooling. Slowly, but they're doing it.

I agree. Cooling systems are pretty reliable these days. IMO, one of the best things for aviation liquid cooling is silicone hoses. Both of my diesels have them and I've had no troubles. And I live in Las Vegas! It's 114F here today...

Kurt
 
Stumbled on this very interesting article from The Aviation Consumer by Paul Bertorelli on actual lifecycle costs of the CD engines vs. Lycoming and other diesels: http://www.aviationconsumer.com/iss...t/Diesel-Reset-Improved-Economics_6962-1.html

His conclusion was that there were no great savings in the US using the CD series diesels. If you were to invest the initial purchase money saved, it would be a complete wash. If you added the installation price, the diesel is quite a bit more expensive. That may change as the TBO/TBR improves but lots of Lycomings in Experimental and flight schools are operated well past 2000 hours on condition too.

No fuel burn specs were given for any engine types so we don't know what figures were being used for the comparison there.
 
Ross,

I also crunched the numbers, assumed replacement/overhaul at TBO/TBR. Using contract fuel prices for Jet-A and LOP of .39 for avgas, I would save 500 bucks in the USA. The real savings came in two forms. One international travel, Jet-A is a lot cheaper. Two the Jet-A has a longer rangeb so could save time.

When I get home in a couple of weeks I can look for the spreadsheets if want them.

Tim
 
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