Chevy LS2 and Trans??? any real issues besides weight

MrV wrote:
Hey Dan good info. Question what is considered "High Load"? My plan
is to run the system at a max of 65%. from personal exp i know running
my auto at 5k rpm will shorten its life but i also know that it'll run
damn near forever at 3500 rpm.

Question for you: What torque/rpm setting do you use to arrive at 65%?

Take a generic direct drive aero engine, and some ballpark figures for
the sake of an example to explain my question:

Let's say cruise flight is at 7,000 feet, wide open throttle, and near
max rpm. Max power is at sea level, wide open throttle, max rpm. More
numbers- let's say this cruise setting translates to 2,500rpm at 24".
Max power is 2700rpm and 29". Use some simple math and simplifying
assumptions (flat torque-rpm curve) about the engine to calculate
"percent" power...

2500/2700 x 24/29 = 77%

(pretty close to the popular definition of cruise power, 75%)

Anyway, just curious what numbers you use to get 65%. Note I don't have
any issue with the figure, I realize it's an arbitrary decision in
performance/reliability tradeoff.

By the way, the first hit on Google for keywords 'chevy ls2 rpm
horspower' gives 400hp at 5200rpm.

well given sea level standard temp i'm looking at ~250hp at 3500 rpm
which from the graphs i've seen translates to about 360-375 lb-ft
torque at that point. now the graphs are few and far between but i'm
sure i can tweak it to atleast this level.

well given sea level standard temp i'm looking at ~250hp at 3500 rpm
which from the graphs i've seen translates to about 360-375 lb-ft
torque at that point. now the graphs are few and far between but i'm
sure i can tweak it to atleast this level.

It's that torque that will kill the transmission. No car,
especially a 'Vette, needs 360 ft-lb of torque and 3500 RPM to cruise
the highway, even at 90 MPH. Torque places a LOT of pressure on gear
teeth so that the friction heats them up, and the relatively high RPM
just multiplies the heating. And we haven't even discussed bearings
yet.
All that power in the car gets used to lay a strip of rubber a
few feet long perhaps a few dozen times in the car's life. More than
that, and the gearing starts to suffer. It's not used for cruising.

Dan

On 13 Nov 2005 14:27:10 -0800, "MrV" wrote:

well given sea level standard temp i'm looking at ~250hp at 3500 rpm
which from the graphs i've seen translates to about 360-375 lb-ft
torque at that point. now the graphs are few and far between but i'm
sure i can tweak it to atleast this level.

MrV, as others have indicated there are a lot of design issues that
make using an auto engine a lot more of an engineering problem than
you might think.

First and foremost, you really need to rethink the idea of using an
auto/truck transmission, even a Corvette tranny. It just doesn't make
sense from an engineering standpoint. It's WAY too heavy for the job
being required, and you are carrying around extra gears and shafts as
dead weight. Not only is it dead weight, it's weight kinda behind the
center of gravity. Plus, the gears you would need to use simply are
not up to the task of transmitting even 50% power, given that you are
talking about an engine capable of putting out 250+. Now that you are
talking about adding bearings to support and isolate the propshaft,
you are adding yet more weight, this time well behind the center of
gravity. Are your wings going to have the ability to swing forward
and aft in order to compensate for the different weights of the
pilot/passengrs and luggage?

There was a guy who tried really really hard to make a go of
installing the Buick/Olds 215CID aluminum V8 in the back of a Long
E-Z. Look for E-Racer on the internet. He kept blowing them up.
Some of the blowups were because he did not research in the hot rod
community about the engine. Had he done so he would have learned that
you cannot bore the engine out to 300 CID and go racing. That doesn't
leave enough material to support the cylinder sleeves. There were
many other problems that caused catastrophic engine failure. His name
is Shirl Dickey. He finally decided to install a Chevy V-6 and last I
heard, he'd yanked it and was using a Lycoming.

This is the setup you are talking about, except that you keep
insisting you can use an auto transmission too.

Driving a prop using a driveshaft has been done successfully before.
See Curtiss P-39 Airacobra and P-61 King Cobra. But the driveshaft
was MASSIVE, as was the engine (Allison V12).

It's admirable to want to build a quiet airplane but it is definately
not a trivial matter. Are you an aerodynamics engineer? If not, you
should be doing some extremely heavy reading to see what such will
take.

Ben Haas has a very clean looking auto engine conversion using an auto
engine. But he has a racing background and the engine is not a stock
unit. He had built a number of engines that raced, prior to
attempting to install something in his airplane. In addition, he did
not design his airplane, he left that headache to Zenith.

Others have mentioned that engineering an auto engine conversion is
not a simple task. Designing and building an airplane is REALLY not a
simple task. You are suggesting you want to do both.

I wish you the best of luck.

Corky Scott

PS, seeking information from this group is not necessarily a good
sign. As Groucho Marx put it, "I would not want to belong to any club
that would have me." ;-)

PPS, for those who think stock Detroit engines are not up to the task
of putting out a continuous 65% power, is it time again for me to post
the description of what one auto manufacturer does typically to test
it's engines? If you've never read it, you will be agast at the
punishment.

thanx charles it was just an idea to use the auto tranny.

just wondering if it would work so maybe just maybe i would have less
engineering work even considering the weight.

on a side note: does anyone have any hard numbers on the weight of an
Ls2 configured to run? I just spent an hour at an off road shop that
is selling me the engine and they say the shipping weight fully
configured is less than 300lbs. this is an off road racing optimized
ls2 i'm considering purchasing. 2 of us actually picked the thing up.
i really don't believe this but these guys build atleast 10 cars per
year.

btw good info charles.

hey can u post those test procedures i would really like to see it for
myself

On 14 Nov 2005 13:21:23 -0800, "MrV" wrote:

just wondering if it would work so maybe just maybe i would have less
engineering work even considering the weight.

1. It has been proven several times that it does not work. Even with
relatively low power engines, it doesn't work. It was tried using a
Honda Goldwing engine. Tranny failed after a while for all the
reasons cited previously. A more powerful engine would fail the
tranny, probably more quickly.

You do have a choice though, there are several businesses
manufacturing PSRU's built specifically for high power V-8's. The
afore mentioned Geschwender folks, and also Northwest Aero, they make
a psru for a high output Chevy, or used to.

So you do have the choice of bolting on a PSRU that you know will
work, thus negating at least that piece of engineering. You will
still have to think about the driveshaft, the coupling at both it's
ends, and all the issues that plague rear propped airplanes.

Corky Scott

Charles K. Scott wrote:
On 14 Nov 2005 13:21:23 -0800, "MrV" wrote:

just wondering if it would work so maybe just maybe i would have less
engineering work even considering the weight.

1. It has been proven several times that it does not work. Even with
relatively low power engines, it doesn't work. It was tried using a
Honda Goldwing engine. Tranny failed after a while for all the
reasons cited previously. A more powerful engine would fail the
tranny, probably more quickly.

You do have a choice though, there are several businesses
manufacturing PSRU's built specifically for high power V-8's. The
afore mentioned Geschwender folks, and also Northwest Aero, they make
a psru for a high output Chevy, or used to.

So you do have the choice of bolting on a PSRU that you know will
work, thus negating at least that piece of engineering. You will
still have to think about the driveshaft, the coupling at both it's
ends, and all the issues that plague rear propped airplanes.

If I were determined to use a driveshaft there might be a good case
for putting the redrive at the prop end and having the driveshaft turn
at engine speed. This is done in some large turboprop installations,
there is a relativly long shaft.

Pusher props are really not that great an idea. Few successful designs
used them.

When I was in Europe, I saw a Fantrainer fly. What ever happened to
that airplane? I think it started with a recip and went to production,
such as it was, with an Allison turboprop.

Pusher props are really not that great an idea. Few successful designs
used them.


Hi all,

Not sure if this was mentionned in recent posts.
Does this document ring a bell ?

http://ibis.experimentals.de/downloa...lvibration.pdf

FWIW,

Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr

"Charles K. Scott" wrote

PPS, for those who think stock Detroit engines are not up to the task
of putting out a continuous 65% power, is it time again for me to post
the description of what one auto manufacturer does typically to test
it's engines? If you've never read it, you will be agast at the
punishment.

Yep, it's time, and this time, I'm going to save it, too. There is another
thread going somewhere else, about auto engines. It might be over in
RAPiloting.
--
Jim in NC

On Mon, 14 Nov 2005 18:36:12 -0500, "Morgans"
wrote:

Yep, it's time, and this time, I'm going to save it, too. There is another
thread going somewhere else, about auto engines. It might be over in
RAPiloting.
--
Jim in NC

Ok folks here it is in it's entirety, note, the comments in
parenthesis are sometimes mine. I originally posted this some five or
six years ago to this group:

Max Freeman is the engineer in charge of GM's Premium Engine programs
and has written an article for Mick Myal in the latest "Contact!"
magazine regarding the development and testing of their new PV6
aluminum 90° bank angle V-6. It's a lot of technical stuff about why
they chose this configuration or mechanical design over that, which is
why I like it.

He also wrote about the kind of developmental testing done on the
engine to make sure that customers get an engine they can depend on,
and I'd very much like to quote that section in full because it should
lay to rest the question of whether auto engines can take the kind of
power settings aircraft engines routinely manage.

"PERFORMANCE

The engine in production form for 1999 develops 215 HP at 5600 RPM and
230 foot pounds of torque at 4400 rpm. As a routine part of an engine
development program we tested the engine at full power, maximum RPM.
We ran it at 6000 RPM, pulling 215 HP at wide open throttle, for 265
hours. That's a continuous 265 hours of wide open throttle, far worse
than autobahn driving, because even on the German Autobahn, you
wouldn't be at 6000 RPM. THAT IS A STANDARD DURABILITY TEST.
(emphasis mine) We run many engines through this test as a matter of
course.

Specific development focus is on the crank, pistons, rods, block
structure, timing drive wear; we get a lot of full load cycles in a
hurry. It isn't necessarily designed to replicate customer driving
but to get development answers. Wear and fatigue are accelerated. The
test is particularly applicable in proving out dampers and their
effectiveness. If the damper is not properly tuned to the engine the
crankshaft will inevitably break in that time period. (note, this is
evidence you should not discard the stock damper when using the auto
engine for aircraft power)

A number of other engine tests are utilized. We use a variety of
specific tests to accelerate engine wear and to look at fatigue
failures. The cyclic endurance test is now called PTED (power train
endurance). It closely approximates cyclic durability. The engine is
cycled from its torque peak to its horsepower peak, at wide open
throttle, then down to idle, then accelerates up to shift points, then
back down to the torque peak and then horsepower peak. This test is
run for 400 hours. Once again, it's a wide open throttle test for 400
hours. The RPM for this engine, ranged between 4400 and 6000 RPM,
back and forth in about a 5 minute cycle. The dyno computer will
occasionally bring the engine down to idle, up to 6500 RPM shift
points, and then back to the 4400 - 6000 RPM 5 minute cycle.

Thermal cycle tests are run to define engine capability under cold
weather condition. We run the engine at full throttle at 4000 RPM,
bring it down to idle, stop it, switch the coolant valves to drain the
hot coolant, pump the chilled coolant from the chiller until the metal
temperature stabilizes at 0 degrees F. Frost forms on the outside of
the block, as the cold coolant rushes into the engine. When it
stabilizes at 0 F, we motor the engine, start it, come to full
throttle at 4400 RPM, the valves switch and the coolant temperature
starts to climb. It climbs back up to 260 degrees F. It takes 10 -11
minutes to complete one cycle. The engine must pass 600 cycles
without any sign of failure. We typically run 1200 cycles and a probe
test will run 1600 cycles. That's a (sic) excellent gasket killer
test. Head gaskets are the first to fail because of the rapid
expansion and contraction.

A powertrain endurance test simulates in-vehicle operation. The
Ypsilanti plant uses it for testing transmission. We, of course, use
it to look at engine performance. The equipment consists of an
engine/transmission combination, which sits on a dyno with large steel
inertia wheels. The inertia wheels are being driven by the
transmission output shaft, just like in a car. They cycle is brutal;
the engine is at idle in gear. The engine accelerates wide open to
6200 RPM, upshift occurs, 6200 RPM is reached, upshift occurs to 3rd,
6200 RPM is reached, upshift occurs to 4th, the wheels turn up to 135
MPH depending on the application. The second half of the cycle calls
for a closed throttle down to 70 MPH, then wide open throttle with a
downshift to 2nd, the engine goes back up to top speed, coasts down so
that the transmission selects down to a lower range. The engine is in
an overrun condition all the way down to idle; i.e., the engine is
being used for braking. That's one cycle. One transmission life
cycle is typically 12K - 13K cycles of the above test. We will run an
engine through 4 or 5 transmissions. This is a very harsh schedule
for the engine, particularly because of the overrun braking. Cylinders
and rings suffer the most on this test.

We run some idle tests to verify low speed operation. The engine is
run at idle for about 2000 hours to make sure of adequate oil flow at
idle.

We use all those engine tests in addition to fleet tests and extensive
vehicle road testing. The customer can be assured that the PV6 engine
is a thoroughly tested advanced design that matches or exceeds
competing offerings."

Corky's comment: I don't believe engine testing for aircraft
certification approaches this intensity, duration or severity.