wrote:

On Tue, 27 Apr 2004 10:48:31 -0500, Dave Driscoll
wrote:



As Pete commented, the DeltaHawk is rated for continuos duty throughout
its HP range (as are most aircraft engines), most automotive engines are
not. While there certainly have been a number of very successful
automotive conversions, all of the successful ones have been the result
of a significant engineering and test efforts (a program which I suspect
is probably not unlike developing an aviation diesel from scratch).



Mostly really interesting information Dave, but your remark about auto
engines not being rated at continuous maximum power prompts me to ask
if it's time to repost that article I have that was written by an auto
engineer who ran the engine test cells at (not sure which major
manufacturer he worked for but it's in the article).

To synopsize, they beat those engines up pretty well, trying to blow
them. They plan to sell not just hundreds, or thousands of engines,
but millions of them. Selling an engine that turns out to have an
endemic problem would be catastrophic for sales. So they run them
literally for hundreds of hours at full throttle and peak rpm. That's
just one test.

None of the auto manufacturers can afford to neglect this kind of
engine development so every single one does these types of destructive
tests to make sure the engine can stand it.

So while the typical auto engine may not be designed to produce
maximum continuous power, they sure can do it.

Corky Scott

PS, I will repost the article if there is enough interest. I get
requests to do so about once a year.




Corky,

I'm pretty sure I've read the article that you are describing in the
past and absolutely agree that testing in the automotive world is quite
severe. However, unless you happen to have access to those test
results, the true duty cycle of the engine is a unknown. There are a
number of very successful automotive conversions that are flying, and in
deference to your point, some of the them with fairly modest
modifications required for acceptable endurance. However, all of them
required some modification and then some serious testing to concretely
demonstrate their endurance. The thrust of my point was not to imply
that automotive engines cannot be successfully modified for use in
aircraft, they quite conclusively can, but rather to demonstrate some of
the challenges that can be encountered in making any required
modifications and what those modifications might be.

Given that the original poster in this thread was asking about the
converting an automotive diesel its perhaps appropriate to examine the
modifications that were made to the Thielert Centurion. The 1.7
Centurion is essentially a modified Mercedes engine, a product which is
certainly respected for endurance and reliability within the automotive
world. I have been told by Thielert representatives (and I'm going from
memory here) that the modifications included the crank, pistons,
injection system, oil pump, turbo, and obviously the reduction unit (not
what I would consider a short list and one that is certainly supported
by a cursory examination of the the engine). In addition, even with all
of these changes, the currently quoted TBR (replacement not overhaul) is
1000 hours (to be fair, they anticipate 2400 hours and I suspect that is
probably still a conservative figure). Personally, I think that the
Thielert engineers did a very professional job and from their published
data they have extensively validated their engine through testing..
However, this illustrates quite clearly the point that regardless of
pedigree, once modification of basic engine system begins it can get
quite complicated quickly.

Personally, potential commercial competition aside, I'd love to see the
original poster successfully convert a 10 cylinder VW diesel for
aviation. I think it would be a really cool project. I'd also do my
best as a citizen of the homebuilding community to help him do it safely
and successfully. That said, I've been down the path you're on
regarding your static test installation. If you're interested, shoot me
your e-mail with your number, I think I can save you some grief on that
project.

Dave Driscoll
DeltaHawk Engines LLC