1.9 tdi powered Cessna 172 Silver Hawk

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
There have been several, but the weight-to-power ratio isn't especially great. Diesel also weighs more than gasoline. Plus, on a plane that size, again for weight savings and simplicity, air-cooled engines are typically better (although there have been air-cooled diesel engines).

So it never was "why" it couldn't be done, more a question of "why would you?" In this instance, the same could be said for using a 180hp VAG gasoline engine, too.
 

QuickTD

Veteran Member
Joined
Feb 25, 2002
Location
SW Ontario
TDI
2003 Audi A4Q 5spd 2.0 TDI 2056VK R783, 2006 Audi A4Q 6spd 2.0 TDI, 2007 A4Q 6spd 2.0 TDI
Oilhammers response is precisely the reason I don't post any threads detailing my TDI swaps anymore. If you've done it and it didn't work out, that's fine. But if you're sitting in a "gaming" chair and you're telling me my work is not worth doing, forgive me for saying that you are an ass.

A friend sent me this a few years ago. The quality of the workmanship is outstanding. I can get pretty close to that now, but it gives me something to shoot for.

To anyone that says "why would you do that" I say, why would you sit on the couch watching TV? I do stupid crap like this all the time, just to understand it. I'll go out on a limb and say I think I'm a better person for my struggles. You cannot buy the education that projects like this provide at any price. I just can't fathom the nobility in watching dancing with the stars I guess...

Just looking at that thing makes me grin. I can't even imagine the pride of the owner, to get that done and fly it, while 10000 people just like Oilhammer wandered in and out of the shop telling him he was an idiot. The strength it took and the satisfaction in having finished it must be otherworldly. I'd like to shake that mans hand and hear his story some day. That person is an important individual.
 

QuickTD

Veteran Member
Joined
Feb 25, 2002
Location
SW Ontario
TDI
2003 Audi A4Q 5spd 2.0 TDI 2056VK R783, 2006 Audi A4Q 6spd 2.0 TDI, 2007 A4Q 6spd 2.0 TDI
In this instance, the same could be said for using a 180hp VAG gasoline engine, too.
I would implore you to step into an airplane powered by a 2009 audi 2.0 TFSI and go for a ride. In fact, I dare you.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
Heh, I wouldn't trust that engine on the ground, let alone in the sky. But that wasn't what I was talking about (those make 200hp). I was talking about one of the old belt driven 1.8t engines. Like my AWM. It has pushed (and continues to push) two tons of AWD Passat down the road through a slushbox for 17 years and 1/4 million miles. THAT I would trust, although in stock form it only made 170hp. I think it makes about 185 now thanks to Rocketchip. :)

I never said anyone was an idiot. And I don't appreciate being called an ass.

The TDI powered plane I was most impressed with used the all aluminum 3cyl (1.0L?). It had a much better power-to-weight ratio, and its shorter length made it closer in size to what the airframe that was being used was made to hold (which was a smallish Rotax engine).
 

redbarron55

Veteran Member
Joined
Jul 10, 2010
Location
Navarre, FL.
TDI
2012 Touareg TDI Executive
A problem with Diesel 4 cylinder aircraft engines has been the relatively harsh torsional impulses and the lack of overlap of those pulses unlike a 6 cylinder engine.
The early modified Diesels used in small aircraft years ago had problems with the coupling to the propeller which has it's own torsional vibration issues.
As I remember these engines were modified MB Diesels and the failures were in the DMF and power transmission issues.
All in all these engines were originally well received, but the problems with reliability plagued them.
Diamond aviation produced a twin engined aircraft with the Diesels. The DA 42 was introduced in 2004. By 2008 reliability problems resulted in the bankruptcy of Thielert. Diamond re-engined the DA42 with the Austro Engine AE 300.
Thielert was bought by the Chinese owner of Continental Motors and has been developed still using MB based engines.
Aircraft engine conversions are not as easy as they seem.
 

[486]

Top Post Dawg
Joined
Mar 1, 2014
Location
MN
TDI
02 golf ALH
I bet the stock application dual mass flywheel provides quite a bit of damping of the torsional rattle.
The pictures show that they did in fact use one of them in there.

Gotta wonder if they could avoid the gearbox on the propeller all together by flipping it over upside down and doing the dry-sump oiling dance. Probably result in needing to pull the glowplugs to drain oil out of the combustion chambers before each start, heh...
Also need to make a custom bracket for the injection pump, it wouldn't like being upside down, end up full of air eventually. Maybe just add a small orifice bleed hole (small enough that the cold start valve is still able to regulate the injection timing) to the return line from the bottom of the case to keep the air bubbles sent back to the tank, though that might not work good without the "separating bowl" of the QA chamber.
 

QuickTD

Veteran Member
Joined
Feb 25, 2002
Location
SW Ontario
TDI
2003 Audi A4Q 5spd 2.0 TDI 2056VK R783, 2006 Audi A4Q 6spd 2.0 TDI, 2007 A4Q 6spd 2.0 TDI
A problem with Diesel 4 cylinder aircraft engines has been the relatively harsh torsional impulses and the lack of overlap of those pulses unlike a 6 cylinder engine.
Literally every light plane has a 4 cylinder engine, so I don't know how this is relevant. Torsional vibration problems are just that, problems, that can be solved by altering flywheel mass or moment of inertia. None are insurmountable, and they are generally immediately apparent if you get yourself out of an office chair and set yourself in the seat. This is not different from automotive drivetrain engineering. Make sure the moment of inertia of the driver (engine/flywheel) exceeds that of the driven elements (the prop) and continue on. The most basic concepts in mechanical engineering need to be observed.

I live 40 minutes from diamond aviation in London, Ontario That place is a manure expo... Whatever you do in the aviation industry, I would suggest that you do not emulate those people. They sell experimental aircraft to the general public.
 

QuickTD

Veteran Member
Joined
Feb 25, 2002
Location
SW Ontario
TDI
2003 Audi A4Q 5spd 2.0 TDI 2056VK R783, 2006 Audi A4Q 6spd 2.0 TDI, 2007 A4Q 6spd 2.0 TDI
Gotta wonder if they could avoid the gearbox on the propeller all together by flipping it over upside down and doing the dry-sump oiling dance. Probably result in needing to pull the glowplugs to drain oil out of the combustion chambers before each start, heh...
Also need to make a custom bracket for the injection pump, it wouldn't like being upside down, end up full of air eventually. Maybe just add a small orifice bleed hole (small enough that the cold start valve is still able to regulate the injection timing) to the return line from the bottom of the case to keep the air bubbles sent back to the tank, though that might not work good without the "separating bowl" of the QA chamber.
The gear reduction is more about available power at a given engine speed. A continental O-200 displaces 201cu/in, so a 3.2l 4cyl. Naturally due to its displacement, you cant spin the thing very fast, so it is tuned for 100hp at a max of 2800rpm. Cruising rpm is around 2300-2400. those engine speeds are good for a standard size/pitch prop. The diesel wants to spin a bit faster for max power, closer to 3500rpm, so the gear reduction is necessary to achieve a good takeoff rating at 3500 rpm and good fuel economy at a 2500-2800rpm cruise.

You could theoretically just use a finer pitch prop, but other factors get in the way. The prop tip speed can become supersonic at max rpm, this destroys performance and is very loud. Another problem is that the automotive engine does not have sufficient thrust bearing capacity to deal with the loads imposed by the propeller. The gearcase is designed with rolling bearings on the prop shaft to accept the thrust loads.
 

redbarron55

Veteran Member
Joined
Jul 10, 2010
Location
Navarre, FL.
TDI
2012 Touareg TDI Executive
4 cylinder engines have issues that can be solved. In the case of MOST 4 cylinder aircraft engine they are direct drive with no flywheel. (other than the prop).
Geared engines are (Almost) always six cylinder or more due to the non overlap problems. Diesels are harsher and often have some kind of coupling between the crankshaft and prop.
As a matter of fact the Jabiru (Australian) engine had problems with the 4 cylinder (not the 6) shearing the flywheel bolts due to these torsional vibrations. I was involved with the RAAS investigations of this problem and the solution.
The four cylinder engines sheared the bolts at about 200 hours as the calculations (after the fact) predicted. The six cylinder with 2/6 more horsepower did not have this issue at all.
In the case of the Jabiru the factory increased the size of the bolts, but experimentally we proved that increasing the torque to the bolt manufacturer's limit would solve the problem.
For reference the final bolts always finished shearing (the final bolts) on start up so no aircraft were lost that I am aware of.
To be exact the bolts did not shear, but rather they failed with fatigue fractures due to repetitive stress and the two parts not clamped where they could not move in relation to each other. Very small movement. Flex the bolts about 1,000,000 times and there you go.
Often these failures are misdiagnosed as the bolts shearing, but microscopic or careful study indicated the failure mode.
 
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[486]

Top Post Dawg
Joined
Mar 1, 2014
Location
MN
TDI
02 golf ALH
The gear reduction is more about available power at a given engine speed. A continental O-200 displaces 201cu/in, so a 3.2l 4cyl. Naturally due to its displacement, you cant spin the thing very fast, so it is tuned for 100hp at a max of 2800rpm. Cruising rpm is around 2300-2400. those engine speeds are good for a standard size/pitch prop. The diesel wants to spin a bit faster for max power, closer to 3500rpm, so the gear reduction is necessary to achieve a good takeoff rating at 3500 rpm and good fuel economy at a 2500-2800rpm cruise.

You could theoretically just use a finer pitch prop, but other factors get in the way. The prop tip speed can become supersonic at max rpm, this destroys performance and is very loud. Another problem is that the automotive engine does not have sufficient thrust bearing capacity to deal with the loads imposed by the propeller. The gearcase is designed with rolling bearings on the prop shaft to accept the thrust loads.
I kinda figured that the thrust bearings wouldn't be up to it, lol little tiny things that they are.
I was mainly going on the assumption that the gears were mainly used for keeping the thrust axis up where it's supposed to be.
Planes are way neat, but they take way too much math for me. I'm more a "plop it on, weld it up and see how it does" kinda guy. :\
 
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