IO 360 Power down (danger, long, rambling post!)

Hi, group. I've come to this august assembelage of persons to ask for
ideas, and to discuss a few of mine. I am the proud owner and flyer of
a lovely, new, RV 8A. Alas, I am not the builder, but as I am sure you
know, owning one begins the process of working with one...

At any rate, we have around 135 hours on this machine. Engine is an
IO-360-A1B6 with one Plasma ignition, one Bendix mag, Gami injectors,
Aero Composites CS prop, stock Van's intake with K&N filter on the
left front baffle shelf. Since the airplane started its flying life,
itsbeen power down. The engine is one of those Bulldog engines
imported from England. It has around 900 hours total, and is fresh
(just before installation) off of an overhaul. Compressions are fine,
plugs look good and I am taking good care of it.

Van's says a 200 horsepower RV8A will cruise at 210mph at 75% power at
8000 feet. Book says it will climb at 2500 fpm at 1500 pounds.

Mine cruises at 182mph and climbs at 1800 fpm. Now, nothing wrong with
that performance, but still and all...The airplane is straight and
slick. No unusual drag makers. It would seem that I am missing around
25 or so horsepower. Oh yeah, the engine SOUNDS like it is running
great, starts great. It is somewhat less great starting hot, and idles
badly, when hot...not something that one can't work around, but not as
good as it should. I have written that off as typical fuel-injected
lyc problems, but perhaps not. Oh yeah, the performance hasn't
deteriorated...pretty much what it was from the start. You might ask
why I have tolerated it up to now, but I really didn't consider that I
was limited until I flew with another RV 8A...which just walks away
from me. Makes me look like I make purt' much everybody ELSE look! :-)
The two aircraft are nearly identical in appearance, so I became
concerned.

The most common cause for missing hp is clogged fuel
injection/injectors. Now, this is a real possibility, given that the
fuel pressure misbehaves (I thought it was just a monitor problem, but
I am starting to wonder. I am also dealing with the afore mentioned
idle problem. The airplane also really doesn't run well without the
boost pump on. I was originally told that the boost pump thingy was
"the way that one works" but in the face of my power loss, I wonder,
now. Mitigating against that is that the airplane still burns 10-11
gallons per hour, and I would think that if I was fuel limited I would
burn less...but that is my speculation. Final point is that the
cylinders all run reasonably close both in CHT and EGT...so again,
speculating, I think that the injectors per se are OK.

Cause number 2 (or so) is a 1 tooth misalignment on the valve timing.
It would seem that such a phenomena occurs more regularly than one
would think. It is pretty easy to check...you just put the engine at
#1TDC and then, with the #2 valve cover off, rock the prop. If the
lifters of #2 don't move within 20 or so degrees...that's the
diagnosis. Certainly this one is possible, and easily checked.

Another possiblility is retarded timing. I have little speculation on
that.

Tuesday, I am going to go to an A&P who is a bud and we are going to
go through things. We'll start with the valve timing, given that it is
a trivial exercise. We'll clean out the injection system, 'cause it
likely needs it anyway. Of course we'll check the timing.

Any of y'all have any OTHER suggestions? The intake manifold would
look to be OK, no holes or the like.

Thanks for sharing my quandry.

Jim

Other possibilities for perceived low power:
* engine instruments out of calibration (how does the fuel burn compare
with expected?)
* bad propeller (wrong helix angle or blade pitch)
* airframe with excess drag

Good luck with your debugging!

Ed Wischmeyer

Mine cruises at 182mph and climbs at 1800 fpm. Now, nothing wrong with
that performance, but still and all...The airplane is straight and
slick. No unusual drag makers. It would seem that I am missing around
25 or so horsepower

I had a similar situation with my RV-4 when I bought it. Climbed OK but was
substantially slower than other O-360 powered RVs. It had a Sterba fixed pitch
wood prop at the time since metal fixed was not available yet. Tried a Sterba
cruise pitch prop with no difference. Got a Sensenich fixed metal 'cruise' prop
when they became available and it was like magic. 15 more MPH on the same RPM.
Climb RPM was 200 less but the rate of climb was the same. I always thought I
needed more power but now I'm not sure. On slightly cooler than standard days
my indicated speed is right next to Vne (215 if I remember). If your RPM and
manifold vacuum is similar to other make and model RVs with that engine then
the engine should be OK. Like mine, it could be the prop airfoil.

Jim

On 4 Jul 2004 19:26:44 -0700, (Jim Harper) wrote:

Hi, group. I've come to this august assembelage of persons to ask for
ideas, and to discuss a few of mine. I am the proud owner and flyer of
a lovely, new, RV 8A. Alas, I am not the builder, but as I am sure you
know, owning one begins the process of working with one...

At any rate, we have around 135 hours on this machine. Engine is an
IO-360-A1B6 with one Plasma ignition, one Bendix mag, Gami injectors,
Aero Composites CS prop, stock Van's intake with K&N filter on the
left front baffle shelf. Since the airplane started its flying life,
itsbeen power down. The engine is one of those Bulldog engines
imported from England. It has around 900 hours total, and is fresh
(just before installation) off of an overhaul. Compressions are fine,
plugs look good and I am taking good care of it.

Van's says a 200 horsepower RV8A will cruise at 210mph at 75% power at
8000 feet. Book says it will climb at 2500 fpm at 1500 pounds.

Mine cruises at 182mph and climbs at 1800 fpm. Now, nothing wrong with
that performance, but still and all...The airplane is straight and
slick. No unusual drag makers. It would seem that I am missing around
25 or so horsepower. Oh yeah, the engine SOUNDS like it is running
great, starts great. It is somewhat less great starting hot, and idles
badly, when hot...not something that one can't work around, but not as
good as it should. I have written that off as typical fuel-injected
lyc problems, but perhaps not. Oh yeah, the performance hasn't
deteriorated...pretty much what it was from the start. You might ask
why I have tolerated it up to now, but I really didn't consider that I
was limited until I flew with another RV 8A...which just walks away
from me. Makes me look like I make purt' much everybody ELSE look! :-)
The two aircraft are nearly identical in appearance, so I became
concerned.

The most common cause for missing hp is clogged fuel
injection/injectors. Now, this is a real possibility, given that the
fuel pressure misbehaves (I thought it was just a monitor problem, but
I am starting to wonder. I am also dealing with the afore mentioned
idle problem. The airplane also really doesn't run well without the
boost pump on. I was originally told that the boost pump thingy was
"the way that one works" but in the face of my power loss, I wonder,
now. Mitigating against that is that the airplane still burns 10-11
gallons per hour, and I would think that if I was fuel limited I would
burn less...but that is my speculation. Final point is that the
cylinders all run reasonably close both in CHT and EGT...so again,
speculating, I think that the injectors per se are OK.

Cause number 2 (or so) is a 1 tooth misalignment on the valve timing.
It would seem that such a phenomena occurs more regularly than one
would think. It is pretty easy to check...you just put the engine at
#1TDC and then, with the #2 valve cover off, rock the prop. If the
lifters of #2 don't move within 20 or so degrees...that's the
diagnosis. Certainly this one is possible, and easily checked.

Another possiblility is retarded timing. I have little speculation on
that.

Tuesday, I am going to go to an A&P who is a bud and we are going to
go through things. We'll start with the valve timing, given that it is
a trivial exercise. We'll clean out the injection system, 'cause it
likely needs it anyway. Of course we'll check the timing.

Any of y'all have any OTHER suggestions? The intake manifold would
look to be OK, no holes or the like.

Verify your airspeed. If you have access to a GPS, you can derive
true airspeed by flying the cardinal headings, noting the
groundspeeds, and plugging the values into this applet.

http://www.reacomp.com/true_airspeed/

This way you have a solid number to compare/contrast any changes you
make to the engine/prop/airframe combo.

I would also suggest doing some timed climbs (noting density altitude)
to compare/contrast against.

-Nathan

"Jim Harper" wrote in message
om...
Hi, group. I've come to this august assembelage of persons to ask for
ideas, and to discuss a few of mine. I am the proud owner and flyer of
a lovely, new, RV 8A. Alas, I am not the builder, but as I am sure you
know, owning one begins the process of working with one...

At any rate, we have around 135 hours on this machine. Engine is an
IO-360-A1B6 with one Plasma ignition, one Bendix mag, Gami injectors,
Aero Composites CS prop, stock Van's intake with K&N filter on the
left front baffle shelf. Since the airplane started its flying life,
itsbeen power down. The engine is one of those Bulldog engines
imported from England. It has around 900 hours total, and is fresh
(just before installation) off of an overhaul. Compressions are fine,
plugs look good and I am taking good care of it.

Van's says a 200 horsepower RV8A will cruise at 210mph at 75% power at
8000 feet. Book says it will climb at 2500 fpm at 1500 pounds.

Mine cruises at 182mph and climbs at 1800 fpm. Now, nothing wrong with
that performance, but still and all...The airplane is straight and
slick. No unusual drag makers. It would seem that I am missing around
25 or so horsepower.

snip

Any of y'all have any OTHER suggestions? The intake manifold would
look to be OK, no holes or the like.

Thanks for sharing my quandry.

Jim

How about a bad camshaft or follower? You could pull the valve covers and
plugs, then rotate the engine by hand and measure the movement of the rocker
arms to see if you have a worn cam lobe or follower. This is a simple way
to determine if there is a valve that doesn't get the same lift as the
others...

By the way, do you have RPM and MP data on the engine? Are you gettting the
reduced performance you quote when running at 75% per the lycoming
rpm/mp/temp charts?

Is it possible that your tach is off or your MP is low because of a clogged
air filter or some other induction problem?

KB

You are missing more horsepower than that. You are in the regime where
the cube rule applies: to go 11.5% faster (182 to 210) on hp alone,
you'll need 55% more horsepower!


(Jim Harper) wrote in message . com...

Van's says a 200 horsepower RV8A will cruise at 210mph at 75% power at
8000 feet. Book says it will climb at 2500 fpm at 1500 pounds.

Mine cruises at 182mph and climbs at 1800 fpm. Now, nothing wrong with
that performance, but still and all...The airplane is straight and
slick. No unusual drag makers. It would seem that I am missing around
25 or so horsepower.

On Mon, 05 Jul 2004 13:19:04 +0000, JFLEISC wrote:

If your RPM and manifold vacuum is similar to other
make and model RVs with that engine then the engine should be OK. Like
mine, it could be the prop airfoil.

Jim

The engine could be way down on power, yet still have the normal rpm and
manifold pressure. For example, if you have a constant speed prop and you
shut down the engine at high speed using the mags or mixture, it would
windmill at the rpm as before, and the manifold pressure would be
unchanged. Of course the rpm would fall off once you slowed down, but it
illustrates the fact that rpm and MP are not guarantees of power if you
have a constant speed prop.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

(JFLEISC) wrote in message ...

I had a similar situation with my RV-4 when I bought it. Climbed OK but was
substantially slower than other O-360 powered RVs. It had a Sterba fixed pitch
wood prop at the time since metal fixed was not available yet. Tried a Sterba
cruise pitch prop with no difference. Got a Sensenich fixed metal 'cruise' prop
when they became available and it was like magic. 15 more MPH on the same RPM.
Climb RPM was 200 less but the rate of climb was the same. I always thought I
needed more power but now I'm not sure. On slightly cooler than standard days
my indicated speed is right next to Vne (215 if I remember). If your RPM and
manifold vacuum is similar to other make and model RVs with that engine then
the engine should be OK. Like mine, it could be the prop airfoil.

Jim

Is a constant speed propellor, so all bets are off there. Nice idea, though!

Jim

"Kyle Boatright" wrote in message ...

How about a bad camshaft or follower? You could pull the valve covers and
plugs, then rotate the engine by hand and measure the movement of the rocker
arms to see if you have a worn cam lobe or follower. This is a simple way
to determine if there is a valve that doesn't get the same lift as the
others...

By the way, do you have RPM and MP data on the engine? Are you gettting the
reduced performance you quote when running at 75% per the lycoming
rpm/mp/temp charts?

Is it possible that your tach is off or your MP is low because of a clogged
air filter or some other induction problem?

KB


Thanks to everyone, so far for the excellent suggestions. Kyle: we are
gonna check for valve timing, and will pursue looking for a worn cam
lobe or follower. Good suggestion, thanks.

My tach has been confirmed by an optical tach, so those are both spot
on. MP? One of the things we are wondering about is an induction
problem, but so far that doesn't look likley. Regarding your comment
about RPM/MP data. Yes, I have RPM and MP data, and can cruise at the
appropriate RPM and MP for 75% power at a given altitude and
temperature. However, if the engine was somehow "derated" to 180 HP,
wouldn't I just be getting 75% of 180HP? The constant speed prop is
going to adapt to the power output to maintain the appropriate RPM,
and the MP is just the MP.

One of the things that lead me to this group was the comment elsewhere
that IO 360 were hot running engines. Mine is pretty cool running.
Hence my suspicion that I am not producing the horsepower!

Thanks again, all.

One hopes we'll have an answer in a few days!

Jim

shut down the engine at high speed using the mags or mixture, it would
windmill at the rpm as before, and the manifold pressure would be
unchanged.

good point.

Jim