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Diesel Daydreams

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john(at)vormbaum.com
Guest

Posted: Mon May 29, 2006 10:08 am Post subject: Diesel Daydreams

Hi Bob,



Food for thought...



Merlyn products has a pair of approved conversions to go to a single-turbo 

version of the IO-540 Wide Deck engine. BOTH installs result in a gross 

weight increase. The kit adds weight, but less than 150 lbs. total (I think) 

and the GW increase is on the order of 400 lbs. The engines are rated at 

320hp for the low-compression engine and 300hp for the high-compression 

conversion (the 300hp turbonormalized conversion adds less weight and gets a 

more modest 250lb. increase). Granted, it's still an avgas engine, still a 

Lycoming, and still 540ci.....but it is new, it does add HP, and you do get 

a GW increase. And it's still Commander Loud.



1) How might the Merlyn conversion be OK with the FAA, but the Centurion 

engine wouldn't?

2) The fuel consumption is greater on the Merlyn increase...wouldn't it be 

easier to plead your case for a conversion with a lower SFC?

3) The diesel props turn considerably slower than the avgas props (2000-2100 

vs. 2575 I believe), which should make LESS noise, right?

4) Centurion has retrofitted a Duke with the 4.0 engine, and that's working 

out fine, but the diesels at 606 lbs. (with all accessories) weigh less than 

an IO-541. It's still a lot heavier than an IO-540....so I think a 

break-even GW would be a nice target, maybe. See the Duke at 

http://www.dukeb60.de/ under "news"

5) The Duke stats list the noise level as lower than they Lyc at 78db(A). 

This sounds pretty good to me (ewww...a pun).



It sounds like the biggest sticking point might be the engine mounts & 

airframe attach points, although I'm pretty optimistic about the strength of 

the Commander airframe.



The death knell might be the price. The Duke guy paid EUR 175,000 PER SIDE, 

which today is about $223,000 per side. For that price, I could just upgrade 

to a 690A.



I just received this from John Towner (he can't post to the list for some 

funky technical reason):



I read your message on the chat page about diesel engines.  Two years ago we 

investigated the diesel for the Aero Commander.  I think it would be a great 

mod but at the time the engine we looked at weighed about 600 lbs and that 

would cut down our usefuel load by about 400 lbs.  The other thing I have 

learned over the years with the 690 and Learjet flying, unless you can get 

above 18,000 extra HP does really not make that much difference in TAS 

overall.



I replied to him to ask if he was looking at the Thielert/Centurion 

conversion or if there are other players out there.



Cheers,



/John



---

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BobsV35B(at)aol.com
Guest

Posted: Mon May 29, 2006 11:44 am Post subject: Diesel Daydreams

Good Afternoon John,

 

My totally non fact based comments inserted as appropriate!

 

In a message dated 5/29/2006 1:09:33 P.M. Central Standard Time,  

john(at)vormbaum.com writes:



1) How might the Merlyn conversion be OK with the FAA, but the  Centurion 

engine wouldn't?

OB --It All Depends!

 

If the Merlyn Conversion was approved before the Part 36 standards were  

written, it would still be OK. Or maybe it does meet the Part 36  criteria!

 



2) The fuel consumption is greater on the Merlyn increase...wouldn't  it be 

easier to plead your case for a conversion with a lower SFC?

 

OB ---Fuel consumption and efficiency are not subject to FAA approval so  it 

would have no bearing at all on any approval. However, I agree that the  lower 

burn and greater efficiency would be a BIG selling point to the  users.

 



3) The diesel props turn considerably slower than the avgas props  (2000-2100 

vs. 2575 I believe), which should make LESS noise, right?

 

OB --- Good point.

 

Actually, if there is no application for a gross weight increase, I don't  

think they have to meet the Part 36 criteria, but I am not sure of that.

 

In any case, quiet is good!



4) Centurion has retrofitted a Duke with the 4.0 engine, and that's  working 

out fine, but the diesels at 606 lbs. (with all accessories) weigh  less than 

an IO-541. It's still a lot heavier than an IO-540....so I think  a 

break-even GW would be a nice target, maybe. See the Duke at  

http://www.dukeb60.de/ under "news"

 

OB --- Sounds good to me.



5) The Duke stats list the noise level as lower than they Lyc at  78db(A). 

This sounds pretty good to me (ewww...a pun).

 

OB --- That's even better.



 

Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503

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john(at)vormbaum.com
Guest

Posted: Mon May 29, 2006 12:38 pm Post subject: Diesel Daydreams

Hi Bob,



I'm not familiar with Part 36 noise standards...I guess I should read up on 

my FARs. Thanks for the comments. I'd love to see a wealthy, intrepid 

Commander pilot (is that an oxymoron?) take the plunge and try the diesels. 

Personally I think it'll be a while before the costs & benefits balance each 

other. In the meantime I'll continue flying my avgas-powered 500B until a 

sweet deal on a 690-series airplane catches my attention.



/John

---

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nico(at)cybersuperstore.c
Guest

Posted: Mon May 29, 2006 4:13 pm Post subject: Diesel Daydreams

Nice move to go diesel. As turbine costs come down it will come so close to

the cost of recip powerplants that a large portion of recip prospects will

prefer to upgrade. 

Pity that they couldn't find someone who speaks English to write their

website content. 

Nico

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