Differences between automotive & airplane engines

LJ wrote:
Not realy.I don't know what your asken me?

Ernest Christley wrote:

LJ wrote:

Also level the plane as it would fly though the air.Only my $0.02.
LJ


And use the measurement to the engines CG. You do know where the CG
is on each of the engines, don't you?



CG isn't something unique to airplanes. Every object within the reach
of gravity has a 3-dimensional point where all the objects weight could
be thought of as being concentrated...engines included.

Take the riduculous case. You have an aircraft engine that stretches
from station 8 to station 10, as the designer put it on paper. The
engine weighs 100# and the CG is at the center. The moment arm is 900.

But you want to substitute the new SuperRev engine, 'cause it only
weighs 75#. 900/75 = 12, so you need to move the engine out 3 stations.
Now the engine will stretch from station 11 to 13. Now what if it is
the same length, but somehow all the weight got concentrated in the
front end. The front end would need to be placed on station 12, and the
back end would be on station 10.

Engines are not homogeneous chunks of metal, and the CG can vary
considerably from one configuration to another. When I bought my
rotary, it was nice and balanced around the center. When I removed the
manual flywheel (~30#) the thing practically flipped up onto the other end.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

My ignition system consists of dual MSD boxes,one fed
throught the main buss and the other fed straight from the battery. I
run a Optima gel cell unit that has 950 cca and can deliver enough
voltage to run the ign for hours. The DAR that inspected my plane asked
that very question and together we calculed I would have to land three
times for fuel before the ign would fail from low voltage. I would like
to think I am not dumb enough to take off the second time in that
failure mode. G

Ben
www.haaspowerair.com


Ben
Your ignition that is "fed straight from the battery." is it straight or do
you have a high current isolation diode in there (and hopefully fused!)?
If not it could fail and take down the battery/alternator and main buss
also.
John
Just curious, no flames ;-)

Richard Lamb wrote:
Lou wrote:

I'll agree with the automotive engine with PSRU being heavier, but are
you sure about your other statement "the lighter the better"?
I'm currently looking at an engine that is 100lbs lighter than the one
recommended for my plane. Although cutting 100lbs from the total
weight is a dream come true, it brings up the question of weight and
balance. I can move the engine forward to make up the difference in
balance, but I don't know how far or how to find out.
Lou


Googling this group for weight and balance yields 25 pages...
So I picked up one of mine here (Dec 10, 2002) and included
Brian's note at the bottom...
(Unfortunately, there was no link attached, so here is the text).



There is a lot of smoke and mirror magic around weight and balance
because so many people understand it so poorly.

At the heart of all of it, though, is a rotational force about a
reference point. the rotational force is called a MOMENT, and
the reference point is called the DATUM.

Sometimes the datum is located at the tip of the spinner.
Sometimes it's located at the main gear axles.
Sometimes its located at the leading edge of the wing.
It doesn't particularly matter where it is located, as long
as you use the same location to work the problem.

You'll often see the term STATION. This is the distance from the
datum to a particular place on the aircraft. Say, for instance,
the instrument panel?

The station numbers change according to where the datum is placed.
But the instrument panel stays in the same physical location.
It's all an offset from a zero point.

One reason to place the datum at the tip of the spinner is because
all the station numbers are positive. No negative distances to
confuse things.

One reason to place the datum at the axles is because the datum
is station zero.zero. Multiply the weight on the wheel times
zero (the ARM is zero at the datum) and the moments for that
wheel come out to zero. Makes the arithmetic a little easier?

And, the reason to place the datum at the leading edge of the wing
it because that's where we are going to wind up anyway. The results
of our CG calculations will finally boil down to a point some given
distance aft of the leading edge.

CG range is often refereed to in terms of a percentage of the wing
chord. Say 25% would be the forward CG limit, maybe 33% would be the
aft limit. So our end number actually refers to a distance aft of
the leading edge. The actual numbers will be different, depending
on where the datum is located, but they all (hopefully) come out
at the same place on the airplane.

First rule:

weight x distance = moments pounds x inches = pound inches (!)
So,
moments / inches = pounds
and
moments / pounds = inches

Practical example:

A bowling ball, held at the chest, has a certain weight.
Held at arms length, it has exactly the same weight!

But due to the longer distance (called ARM) it has a much higher moment.
\
THAT's what feels so heavy.
That rotational force.

So, to solve your little weight and balance question.

The only distance from anything. that matters, is the
distance from the CG of the instrument to the DATUM
specified for that aircraft.

If you have a "before" weight and balance already done,
multiply the weight of the instrument times the distance
from the datum given in the "before" problem.

Then add that moment to the airplane's moment,
and the instrument weight to the airplane's weight.

Divide the new moments by the new weight and you get the
new CG location.

Does that help?

Or do you maybe feel like I sometimes do after some
of your answers???





Thanks Rich,
This information does help quite a bit, and I'm happy that I could
make you feel a little smarter everytime I answer one of your posts.
Lou

Lou wrote:



Thanks Rich,
This information does help quite a bit, and I'm happy that I could
make you feel a little smarter everytime I answer one of your posts.
Lou


Than YOU, Lou, but

Looks like I missed the "level the aircraft first".
I think it was in the original thread somewhere prior.

Minor little detail, but So important.

So much for smarter...

Richard

Your points are well taken. The cost of just replacing the O2 sensor
is not
exorbitant.

Is there any really easy way to tell what engines are available with
non O2
sensing ECMs?


////////////////////////////////////////////////////////////////////////

I would assume any engine that is marketed to a foreign country that
doesn't require the use of unleaded fuel would be compatable. I know
for sure the GM LS1 series are available with both style puters, I
think the Caddy northstar engine comes that way too. There are
companies that manufactuer "test" units that mimic O2 sensors so that
is an option. On my Firewall forward package I kept things VERY simple.
One Holley carb with the Mcneilly mixture leaning block installed gives
precise fuel metering, is cost effective and bulletproof. In my
application I have a high wing so if by a million to one shot I lose
both fuel pumps ,gravity flow should keep the motor running till I get
her down safely. My ignition system consists of dual MSD boxes,one fed
throught the main buss and the other fed straight from the battery. I
run a Optima gel cell unit that has 950 cca and can deliver enough
voltage to run the ign for hours. The DAR that inspected my plane asked
that very question and together we calculed I would have to land three
times for fuel before the ign would fail from low voltage. I would like
to think I am not dumb enough to take off the second time in that
failure mode. G

Ben
www.haaspowerair.com

Chris Wells wrote:
Ok, I've been scolded for using the word "automotive" and then I was
scolded for using "automobile". It would seem to me that in this
context, "automobile" would be correct, but can someone give me a final
ruling?


Well if it makes use of the Otto cycle you can call it an Ottomobile
too.

BTW, this has been a very informative thread. This is exactly what I
read message boards for.


--

FF

John wrote:
My ignition system consists of dual MSD boxes,one fed
throught the main buss and the other fed straight from the battery. I
run a Optima gel cell unit that has 950 cca and can deliver enough
voltage to run the ign for hours. The DAR that inspected my plane asked
that very question and together we calculed I would have to land three
times for fuel before the ign would fail from low voltage. I would like
to think I am not dumb enough to take off the second time in that
failure mode. G

Ben
www.haaspowerair.com


Ben
Your ignition that is "fed straight from the battery." is it straight or do
you have a high current isolation diode in there (and hopefully fused!)?
If not it could fail and take down the battery/alternator and main buss
also.
John
Just curious, no flames ;-)


Yes to the later of the above.................................

I agree,Ernest!
I was merrily adding to the problem,as I fly a tail dragger.
Just nit picking I guess. The old one,LJ

Ernest Christley wrote:
LJ wrote:

Not realy.I don't know what your asken me?

Ernest Christley wrote:

LJ wrote:

Also level the plane as it would fly though the air.Only my $0.02.
LJ


And use the measurement to the engines CG. You do know where the CG
is on each of the engines, don't you?



CG isn't something unique to airplanes. Every object within the reach
of gravity has a 3-dimensional point where all the objects weight could
be thought of as being concentrated...engines included.

Take the riduculous case. You have an aircraft engine that stretches
from station 8 to station 10, as the designer put it on paper. The
engine weighs 100# and the CG is at the center. The moment arm is 900.

But you want to substitute the new SuperRev engine, 'cause it only
weighs 75#. 900/75 = 12, so you need to move the engine out 3 stations.
Now the engine will stretch from station 11 to 13. Now what if it is
the same length, but somehow all the weight got concentrated in the
front end. The front end would need to be placed on station 12, and the
back end would be on station 10.

Engines are not homogeneous chunks of metal, and the CG can vary
considerably from one configuration to another. When I bought my
rotary, it was nice and balanced around the center. When I removed the
manual flywheel (~30#) the thing practically flipped up onto the other end.

("stol" wrote)
My ignition system consists of dual MSD boxes,one fed throught the main
buss and the other fed straight from the battery. I run a Optima gel cell
unit that has 950 cca and can deliver enough voltage to run the ign for
hours.


Ignoring paperwork issues for the moment: Is this an ignition system that
could be easily(?) retrofitted to a standard Cessna 172 / Piper Warrior?

If yes, (guesstimating) what would the performance gains be over the factory
stock ignition systems they're running now? 1%? 5%? 10%?

Or is it mostly a reliability issue?


Montblack

Ignoring paperwork issues for the moment: Is this an ignition system
that
could be easily(?) retrofitted to a standard Cessna 172 / Piper
Warrior?

If yes, (guesstimating) what would the performance gains be over the
factory
stock ignition systems they're running now? 1%? 5%? 10%?


Or is it mostly a reliability issue?


Montblack


//////////////////////////////////
It is VERY reliable for sure. If I were to"experiment" with this
concept all one would have to do is install a crank trigger to fire the
boxes, have it set up so the plugs would fire every 360 degrees as to
keep the distributing simple, who cares if the plugs spark during the
overlap period, Two strokes do this. The MSD units can be fitted with
timing curves so that will give a performance gain for sure. As for
amount of HP gain, if I were younger and still had my R&D dyno I sold
to Jasper engines a few years back I would experiment just to see what
numbers would come up. My gut feeling is................8-12%