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