VW Reality

On Feb 2, 5:48 am, Stealth Pilot
wrote:

Bob I admire your work so I'm going to irritate you with an argument.
I wish someone would post a concise guide to a style of VW conversion
that is durable and simple. have never seen one that had the tests of
time behind it. 1600 or 1835cc for preference.
-------------------------------------------------------------------------

Dear Stealth,

Allow me to share with you something I just saw on the internet. Some
old geezer said:

"As far back as Rockford, at least three builders of converted VW's
appealed to Pope Paul to use the EAA's bully pulpit for educating
homebuilders about the realities of automobile engine conversions. At
least two of us (me and Ted Barker) even offered to provide the
required torque-stand. But the EAA was (and is) more interested in
selling tent-space and full-page ads than in contributing to the basic
store of USEFUL homebuilt information."

Ain't that a hoot? Stupid ol' fool actually thought the EAA was about
doing something USEFUL, like, mebbe, what you said up there at the
top.

-R.S.Hoover

I could be very, very wrong, but my understanding of efficiency is that 25%
efficiency means that a quarter of the energy goes to torque and 3/4 to
heat. That would mean you throw away THREE horsepower's-worth instead of
four, no?

Jim



since such engines are no more than 25% efficient when it comes to
converting the heat of combustion into torque at the crankshaft. That
means that for every horsepower measured at the crank you must
generate at least four horsepower's-worth of heat in combustion.

RST Engineering wrote:
I could be very, very wrong, but my understanding of efficiency is that 25%
efficiency means that a quarter of the energy goes to torque and 3/4 to
heat. That would mean you throw away THREE horsepower's-worth instead of
four, no?

Jim



since such engines are no more than 25% efficient when it comes to
converting the heat of combustion into torque at the crankshaft. That
means that for every horsepower measured at the crank you must
generate at least four horsepower's-worth of heat in combustion.


You are correct, but that is also exactly what he said ---. i.e.
generate four hp in heat, only one available at the shaft.

Charles

"Charles Vincent" wrote in message
t...
RST Engineering wrote:
I could be very, very wrong, but my understanding of efficiency is that
25% efficiency means that a quarter of the energy goes to torque and 3/4
to heat. That would mean you throw away THREE horsepower's-worth instead
of four, no?

Jim



since such engines are no more than 25% efficient when it comes to
converting the heat of combustion into torque at the crankshaft. That
means that for every horsepower measured at the crank you must
generate at least four horsepower's-worth of heat in combustion.


You are correct, but that is also exactly what he said ---. i.e. generate
four hp in heat, only one available at the shaft.

Charles

Well, with only slight rephrasing, that is what was said at the beginning of
this thread. The rephrasing would be that we "throw away 3 horespower's
worth of heat out of every four".

Actually, that is slightly worse than I was taught; but I really did not
regard it as the primary issue under discussion--so I let it be. The number
that I was taught a little more than 40 years ago was 30% when running at a
moderately high percentage of power. I understand that there has been
considerable improvement since then, which could have brought the efficiency
up to around 33%, and I have read recently (from a forgotten source) that
the theoretical maximum is around 37% efficience for spark ignition engines.

So, for the moment, it is unclear (at least to me) whether the 25% figure is
slightly low, pertains to rich mixture opperation, or is related to the low
compression and the intake and exhaust plumbing of the engines in question.
In any case, even the 25% figure is really much better than we can obtain
from our supposedly more efficient automobile engines--especially when you
consider the waste in time spent idling or simply "spun up" to avoid lugging
(because the cost of not doing so is far greater).

However, the basic point of Bob's original post is very real; even on the
highway, cars and trucks normally run at a very low percentage of power--and
the few exceptions, such as pulling trailers far about the rated limit, seem
to result in increased failure rates and short TBOs.

I admit that I still believe a 1600, and especially an 1800, is fully
capable of producing 60 hp on takeoff and 30 hp in cruise with a 52 inch
diameter prop--and that the addition of thermal barrier and dispersant
coatings might allow a climb power approaching 40 hp. But none of that
detracts from the basic points--that cars and trucks normally opperate at
surprisingly low ower levels, and that 100 maximum continuous hp from a
Continental O-200 really does mean continuous. Taken in that context, tha
1600 might well be 40 hp maximum and 30 hp cruise; and the thermal coatings
might raise that to 45 hp maximum and 33 hp cruise.

Peter
(Former engineering student and shade-tree mechanic)

On Feb 4, 12:23 pm, "Peter Dohm" wrote:

I still believe a 1600...

------------------------------------------------------------------------------

That'll make a fine epitaph.

An engine doesn't give a **** what you believe. Nor what some
huckster has told a tent-full of the faithful to separate them from
their money. Engines are painfully honest -- often fatally so.

Build a few. Put your beliefs aside and listen to what the ENGINE has
to say.

-R.S.Hoover

Peter Dohm wrote:
"Charles Vincent" wrote in message
t...

RST Engineering wrote:

I could be very, very wrong, but my understanding of efficiency is that
25% efficiency means that a quarter of the energy goes to torque and 3/4
to heat. That would mean you throw away THREE horsepower's-worth instead
of four, no?

Jim




since such engines are no more than 25% efficient when it comes to
converting the heat of combustion into torque at the crankshaft. That
means that for every horsepower measured at the crank you must
generate at least four horsepower's-worth of heat in combustion.


You are correct, but that is also exactly what he said ---. i.e. generate
four hp in heat, only one available at the shaft.

Charles


Well, with only slight rephrasing, that is what was said at the beginning of
this thread. The rephrasing would be that we "throw away 3 horespower's
worth of heat out of every four".

Actually, that is slightly worse than I was taught; but I really did not
regard it as the primary issue under discussion--so I let it be. The number
that I was taught a little more than 40 years ago was 30% when running at a
moderately high percentage of power. I understand that there has been
considerable improvement since then, which could have brought the efficiency
up to around 33%, and I have read recently (from a forgotten source) that
the theoretical maximum is around 37% efficience for spark ignition engines.

So, for the moment, it is unclear (at least to me) whether the 25% figure is
slightly low, pertains to rich mixture opperation, or is related to the low
compression and the intake and exhaust plumbing of the engines in question.
In any case, even the 25% figure is really much better than we can obtain
from our supposedly more efficient automobile engines--especially when you
consider the waste in time spent idling or simply "spun up" to avoid lugging
(because the cost of not doing so is far greater).

However, the basic point of Bob's original post is very real; even on the
highway, cars and trucks normally run at a very low percentage of power--and
the few exceptions, such as pulling trailers far about the rated limit, seem
to result in increased failure rates and short TBOs.

I admit that I still believe a 1600, and especially an 1800, is fully
capable of producing 60 hp on takeoff and 30 hp in cruise with a 52 inch
diameter prop--and that the addition of thermal barrier and dispersant
coatings might allow a climb power approaching 40 hp. But none of that
detracts from the basic points--that cars and trucks normally opperate at
surprisingly low ower levels, and that 100 maximum continuous hp from a
Continental O-200 really does mean continuous. Taken in that context, tha
1600 might well be 40 hp maximum and 30 hp cruise; and the thermal coatings
might raise that to 45 hp maximum and 33 hp cruise.

Peter
(Former engineering student and shade-tree mechanic)




That (the last paragraph) does seem to agree pretty well with my results.

For whatever that's worth...


Richard

wrote in message
...
On Feb 4, 12:23 pm, "Peter Dohm" wrote:

I still believe a 1600...

------------------------------------------------------------------------------

That'll make a fine epitaph.

An engine doesn't give a **** what you believe. Nor what some
huckster has told a tent-full of the faithful to separate them from
their money. Engines are painfully honest -- often fatally so.

Build a few. Put your beliefs aside and listen to what the ENGINE has
to say.

-R.S.Hoover

Sorry to have upset you.

Peter

"cavalamb himself" wrote in message
...
Peter Dohm wrote:
-----------------much snipped--------------

I admit that I still believe a 1600, and especially an 1800, is fully
capable of producing 60 hp on takeoff and 30 hp in cruise with a 52 inch
diameter prop--and that the addition of thermal barrier and dispersant
coatings might allow a climb power approaching 40 hp. But none of that
detracts from the basic points--that cars and trucks normally opperate at
surprisingly low ower levels, and that 100 maximum continuous hp from a
Continental O-200 really does mean continuous. Taken in that context,
tha 1600 might well be 40 hp maximum and 30 hp cruise; and the thermal
coatings might raise that to 45 hp maximum and 33 hp cruise.

Peter
(Former engineering student and shade-tree mechanic)




That (the last paragraph) does seem to agree pretty well with my results.

For whatever that's worth...


Richard

Actually, it's worth a great deal because it provides further confirmation
for the maximum continuous power; and does so within a range of speeds that
approximate maximum performance climb for a lot of small experimentals.
That's probably about as close as it gets for a useable rull of thumb.

BTW, it seems to me that they are not that far from Veeduber's maximum
continuous numbers.

Peter

Way back when I was a university student I got stuck fixing a girlfriends VW
"Bug". (I think she liked the Bug more than me but kept me around 'cause I
could fix it.) From that experience I developed a strong dislike for the
"Bug". My Volvo 544 was both more comfortable and more reliable while
providing about the same gas milage.

Once while chasing VW parts in the Volvo (Never happened the other way
'round) I struck up a conversation with a German mechanic at a VW shop.
Refering to the little flat 4, he said, "Well, it was a good idea when it
made 36HP - not so good when they increased the power. "What do you
drive?", I asked. He pointed to a brand new Caddy and gave me a slow wink.

If you want a light weight engine why not look hard at state of the art
Japanese "liter bike" engines instead of a 60 year old VW design? My
Kawasaki cranks out 108HP and is reputed to be bulletproof. Of course a
PRSU would be manditory given that the little Kawi would be turning almost
9,000 RPM.

Somebody made a 2.8 liter V8 out of a pair of Hyabusa cylinder blocks.
Making a flat 4 shouldn't be any harder.
See: http://thekneeslider.com/archives/20...usa-v8-engine/

On Mon, 04 Feb 2008 13:06:29 -0600, Charles Vincent
wrote:

RST Engineering wrote:
I could be very, very wrong, but my understanding of efficiency is that 25%
efficiency means that a quarter of the energy goes to torque and 3/4 to
heat. That would mean you throw away THREE horsepower's-worth instead of
four, no?

Jim



since such engines are no more than 25% efficient when it comes to
converting the heat of combustion into torque at the crankshaft. That
means that for every horsepower measured at the crank you must
generate at least four horsepower's-worth of heat in combustion.


You are correct, but that is also exactly what he said ---. i.e.
generate four hp in heat, only one available at the shaft.

Charles
What he's forgetting is the 1 available at the shaft is STILL heat
energy.
Fuel makes 4
Pistons catch 1
cooling and exhaust loose the other 3.


--
Posted via a free Usenet account from http://www.teranews.com