Any body running an engine notice that or is it just
my RV4? Also the mixture is rapidly varying which of course
could be caused by the rapidly changing fuel
pressure. My pressure regulator is referenced to intake
manifold pressure. Is everybody doing that?

It is so bad I can't believe the engine runs.
Now that I have learned to steer the RV I can focus
on what is going on with the engine :)

Paul Lamar

How are you monitoring your fuel pressure?

Matt-

With an electronic sensor and an EFIS in the cockpit

There is also a steam gage but I can't see it as it is
under the cowl. I need somebody to stand out there
and read it with the cowl off. Somebody I can trust
to not get in the way of the prop.

Here is a short movie so you can hear it run.

------------------------------**-----------------
I suspect the manifold pressure is jumping up and down affecting
the pressure regulator and what Tracy's EC manifold pressure sensors
are seeing.

Here is how the road racers damp the manifold pressure for EFI.

This is easy to try so it will be one of the first attempted
fixes.

Paul Lamar

I'm getting right around 37-39 PSI pretty consistently, regardless of
engine speed. I use the stock regulator and fuel rails. Tracy's fuel
pump(two of them, but both only on landing and take- off). Regular
350 psi automotive fuel hose.  What type of pressures are you getting?

Brian Trubee

Fuel pressure is bouncing around pretty bad. 30 to 50 psi.

Are you using the manifold pressure tap?
I know you had a lot of trouble tuning.
Are you using the oil hole pressure taps?

Mike put the manifold  pressure tap just south of the throttle body
in the dynamic chamber. I am sure that place is jumping around all
over the place. I have not yet put the pressure data acq on Mike's
airplane.

The other thing that could be going on is Mike's Aeromotive
adjustable pressure regulator could be leaking at low manifold
pressure ranges. I am thinking of using RTV to seal it.

Paul


Paul,

Would I be correct in assuming this plane flew with these components
before?
If the manifold pressure is erratic, you can install a pulse damper. What
is
the tap type and thread size? Amot makes restricters with 1/4 NPT male and
female threads. You can spec the port size from a few selections. 0.015" is
the smallest I know of. Also between the restriction and the pressure reg,
use
a larger diameter tube or hose. The extra volume will help settle the
pulses
down. Also what is the pressure range of the regulator? If it is close to
the
lower limit it may unseat and seat again rapidly and give erratic output as
will too large a capacity unit.
contact   sales@amotusa.com
They will be able to direct you to a local distributor.

Dale Davies

Yes it flew but Mike was not happy with the tuning.

Paul Lamar



Before making any mods, I suggest finding said trustworthy person to
watch the mechanical gauge while the engine is running.  Or set a
camera up to watch it.  Or put a longer hose on it so you can see it
from the cockpit.  Or tie the tail down to something so you can watch
it..

You might have an instrumentation problem - floating ground - driving the
EFIS.

Make sure there's an actual fuel pressure problem before trying to fix it.


Regards,

Matt-

Matt,
Look! :)

Paul Lamar


Why do you even bother asking the group, Paul??  You already know what to
do..   ;)

Sorry, I apparently missed that part of the thread..

So, you see the same fluctuation in fuel pressure with the mechanical
gauge?


Matt-

I have not tested it yet. I was not happy with my mickey mouse
plumbing job so I re plumbed with steel brake line this morning.
I need to leave bright and early tomorrow morning so I won't
get a chance to run the engine again until I get back in about
a week.

I discovered Edelmann automotive fittings, hoses, lines & tubing.
These are the hot tip for mechanical pressure gages. Super robust.
The 3/16th OD black steel line is easy to bend and work with.
These MUST be reliable as they are car brake lines. Much cheaper
than AN braided lines.

http://www.plews-edelmann.com/

With out the engine running it is a solid 40 psi.
As you can see the vacuum lines are tapped into the dynamic
chamber. There is lots going on in there aerodynamically speaking.

I will eventually move them to the now unused oil injection holes
in the rotor housings. It will mean retuning the engine.


Paul Lamar
-

Sounds good.

I wonder how quickly the regulator can respond to changes in manifold
pressure.
I don't know precisely how the mechanism works but imagine it's probably a
little chamber with a diaphragm that pushes on a spring loaded tapered rod.
I imagine there's some mass and maybe some friction that probably already
damps the pressure.


Matt-

Paul,

How long has it been sitting?  Have you disassembled the fuel pressure
regulator to inspect for corrosion?  Seems wort 15 minutes to verify that it
is working properly.

Mark S.

Good idea. Maybe the auto gas with alcohol affected the diaphragm.

Paul Lamar