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

Kevin Horton wrote in message ...

Please detail how you determined the cruise speed and climb rate. If you
used the IAS and converted to TAS there are a lot of ways that errors can
be introduced. For example, I've seen reports of ASIs with over 10 mph of
instrument error, and I've communicated with builders who found that flush
static ports causing the airspeed to read over 10 mph too low. A local
RV-8 builder had that problem recently. And some of the methods that
people quote for using GPS to get TAS aren't mathematically sound,
although the error here would only be a few mph, unless you've done
something really creative.

Lots of info on how to figure out TAS from GPS data, how to calibrate ASIs
and how to measure static source position error at my web site:

http://go.phpwebhosting.com/~khorton...ex.php?&PID=48
http://go.phpwebhosting.com/~khorton...ex.php?&PID=49

If you used the VSI to determine climb rate, be aware that VSIs can have
very large errors. You really need to use an altimeter and a stop watch.
And you need to understand that the rate of climb that Van quotes is
almost certain an extrapolation down to sea level at standard temperature.
You are almost certainly at a higher altitude when you do your testing,
and the temperature may very well be warmer than standard, so your rate of
climb would be a bit less than 2500 even if everything else is sorted out.

First to Jerry: Yep, am a member of the RV-8 list. Got a couple of
great ideas from them.

Now to Kevin: Yer right. I am currently using TAS from a Blue Mountain
Efis compared to GPS ground speed. The two seem to match up pretty
well. I am fully cognizant that the the GPS ground speed is affected
by wind, but over a hundred hours or so I am recognizing that the two
track quite well. This ain't science, yet. :-)

Climb rate is absolutely based on VSI and again, agree that there is
substantial error present...possibly.

What started this quest was more of a global sense that we were way
off from the standards...followed by a flight with an acquaintence's
RV-8 with ostensibly the same set-up as mine (well, different prop,
and no nose wheel)...and he made me look like I pretty much have been
making everyone ELSE look.

As I said, we went through everything on Tuesday and are replacing the
gas filter for one that is less restrictive and tuning the prop
governor for FULL take-off power. I am quite a lot more confident that
there are no subtle engine problems, and it is likely going to be a
fix each aerodynamic detail at a time to get it to where I want it to
be.

We have also fixed the fuel-flow indicator, and between that and the
BMA EFIS's ability to record flights, I am going to be able to
actually generate some data. My first two projects will be actual
time-to-climb vs fuel usage and the leaning exercise needful to work
with the GAMI folks so I can further tune my fuel system.

I will be (after I have some better data (as opposed to
impressions...hey, impressions are good enough for newsgroups, I need
data to dicker with manufacturers)) talking with the aerocomposites
folks to make sure I have the right prop. They are advertising an RV 8
with fairly spectacular performance with one of their props (but a 74
inch prop, mine is considerably shorter, but with (I think) a
considerably wider chord). We'll compare and contrast and see if we
can gain from the prop losses that I suspect are occuring.

Then on to the nickle-and-dimers...off with the tie-down rings, better
seals at the various interfaces, maybe have a look at a different
cowl/induction system.

I have an outstanding airplane. It is fast, climbs very well, and is
more airplane than I have ever flown. And a great deal of fun. Now I
just want more! :-)

Jim

In article ,
(Jim Harper) wrote:

Kevin Horton wrote in message
...

Please detail how you determined the cruise speed and climb rate. If you
used the IAS and converted to TAS there are a lot of ways that errors can
be introduced. For example, I've seen reports of ASIs with over 10 mph of
instrument error, and I've communicated with builders who found that flush
static ports causing the airspeed to read over 10 mph too low. A local
RV-8 builder had that problem recently. And some of the methods that
people quote for using GPS to get TAS aren't mathematically sound,
although the error here would only be a few mph, unless you've done
something really creative.

Lots of info on how to figure out TAS from GPS data, how to calibrate ASIs
and how to measure static source position error at my web site:

http://go.phpwebhosting.com/~khorton...ex.php?&PID=48
http://go.phpwebhosting.com/~khorton...ex.php?&PID=49

If you used the VSI to determine climb rate, be aware that VSIs can have
very large errors. You really need to use an altimeter and a stop watch.
And you need to understand that the rate of climb that Van quotes is
almost certain an extrapolation down to sea level at standard temperature.
You are almost certainly at a higher altitude when you do your testing,
and the temperature may very well be warmer than standard, so your rate of
climb would be a bit less than 2500 even if everything else is sorted out.

First to Jerry: Yep, am a member of the RV-8 list. Got a couple of
great ideas from them.

Now to Kevin: Yer right. I am currently using TAS from a Blue Mountain
Efis compared to GPS ground speed. The two seem to match up pretty
well. I am fully cognizant that the the GPS ground speed is affected
by wind, but over a hundred hours or so I am recognizing that the two
track quite well. This ain't science, yet. :-)

Climb rate is absolutely based on VSI and again, agree that there is
substantial error present...possibly.

What started this quest was more of a global sense that we were way
off from the standards...followed by a flight with an acquaintence's
RV-8 with ostensibly the same set-up as mine (well, different prop,
and no nose wheel)...and he made me look like I pretty much have been
making everyone ELSE look.

As I said, we went through everything on Tuesday and are replacing the
gas filter for one that is less restrictive and tuning the prop
governor for FULL take-off power. I am quite a lot more confident that
there are no subtle engine problems, and it is likely going to be a
fix each aerodynamic detail at a time to get it to where I want it to
be.

We have also fixed the fuel-flow indicator, and between that and the
BMA EFIS's ability to record flights, I am going to be able to
actually generate some data. My first two projects will be actual
time-to-climb vs fuel usage and the leaning exercise needful to work
with the GAMI folks so I can further tune my fuel system.

I will be (after I have some better data (as opposed to
impressions...hey, impressions are good enough for newsgroups, I need
data to dicker with manufacturers)) talking with the aerocomposites
folks to make sure I have the right prop. They are advertising an RV 8
with fairly spectacular performance with one of their props (but a 74
inch prop, mine is considerably shorter, but with (I think) a
considerably wider chord). We'll compare and contrast and see if we
can gain from the prop losses that I suspect are occuring.

Then on to the nickle-and-dimers...off with the tie-down rings, better
seals at the various interfaces, maybe have a look at a different
cowl/induction system.

I have an outstanding airplane. It is fast, climbs very well, and is
more airplane than I have ever flown. And a great deal of fun. Now I
just want more! :-)

Jim

One possibility is that one or more of your hydraulic lifters is not
pumping up properly, thus inhibiting valve opening (and proper fuel/air
charge). One sure sign of this ailment is a loud tapping noise when the
engine is idling. You can also check the tappet clearances and make sure
that they are within tolerance.

Jim,

Just to eliminate all errors, I guess you don't misstake knots with mph, but
210 mph is 182,45 knots, what units is your ASI and GPS reading?

Jan Carlsson
www.jcpropellerdesign.com

"Jim Harper" skrev i meddelandet
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. 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

"Jan Carlsson" wrote in message ...
Jim,

Just to eliminate all errors, I guess you don't misstake knots with mph, but
210 mph is 182,45 knots, what units is your ASI and GPS reading?

Good thinking, good question. Knots. :-)

Jim

I was typing in the figures for the RV8 in my program when notis that 210mph
was 182 knots.

by the way, with all settings at standard it gave an optimum diameter of 72"
but there are many but's.

Jan Carlsson
www.jcpropellerdesign.com

"Jim Harper" skrev i meddelandet
om...
"Jan Carlsson" wrote in message
...
Jim,

Just to eliminate all errors, I guess you don't misstake knots with mph,
but
210 mph is 182,45 knots, what units is your ASI and GPS reading?

Good thinking, good question. Knots. :-)

Jim