I'm going to ground my airplane until I get to the bottom  of this. I can
tune it on the ground and it will run just fine all the way  from idle to
full throttle. I get about 5300 rpm at full throttle at 29 in  hg. MP. I
have 12 hours in the air so far but can't get past this issue.  Other
than this, the plane is an absolute joy.

When  I get off  the ground, when I go through around 5400 RPM, I start
to get stumbling and  engine roughness. At this RPM I am about 18 inches
MP. Just below this  point, I am making about 50% power and the engine
will run  smoothly.

I went to another airport and had a lot of roughness on  takeoff, but I
am used to it and so continued on my way to my home airport.  When I got
back I found out that someone at the other airport wanted to  report me
to FSDO because he thought my engine was going to blow up, but he  didn't
get my tail number.

So, I thought I had it sorted out before  I flew today, but it's back to
the drawing board. I've tried both leaning  and enriching the mixture at
all throttle settings, but to no avail. At and  above 5400 rpm I start
getting all sorts of roughness so I think that it  has to be an ignition
issue. My injector wiring is separated from my coil  wiring, but could I
be getting inductance between the different coil  wiring?

I have a 93 13 BREW normally aspirated, 2.85 RWS redrive, EM2,  EC2, 88x
74 CAtto Prop. This is getting to be really frustrating. It's got  to be
something simple that I'm overlooking. I don't know anyone with  an
ocilliscope, and have never used one.

Brian  Trubee


Does the intake system still look like this?  If so  remove
the large right angle pipe before the throttle body and fly it  again.
Don't worry about where it is getting the intake air. There are  probably
enough
leaks in the cowling to supply enough air for the  engine.

That pipe is resonating somewhere in your RPM range. Probably  around 5500
RPM. I
don't know for sure if that is the problem but it is  worth a quick try.

Is there an opening in the cowl on the bottom for  the intake air?
If so take some pictures of  it.

---------------------------------------------------------------------

I  am looking for a different response Brian. Without the pipe
it still may  run rough so it will need to be re tuned for that
configuration. In  principle it is a good idea to keep the length
of the intake tract up to  the throttle body as sort as possible.
That means an air intake some where  near the throttle body
on top of the cowl.

I am sorry but every time I hear about these  kinds of problems I get angry.
If I put on my programmers hat I know that  Tracy's EM2 engine monitor
could be ten times better if only he added a USB  port and sent all the
data to a net book, tablet or God forbid even a  recent cell phone.

Back in the
early days of the personal  computers and the Apple II we immediately
discovered that less than 80  characters per line and 25 lines was not
a viable user interface. The EM2  screen is a far cry from this minimum
required user interface. Now a days  we can have 100 characters and 100
lines on a high resolution color net  book or tablet screen.

Here is the problem. You can not see a complete  map of the mixture as
a function of RPM and intake manifold pressure on the  EM2 screen.
This makes it far more difficult to trouble shoot these intake  manifold
problems.

As an illustration of what I am talking about here  are a couple of the
possible tuning screens on a Megasquirt system. The  Megasquirt has an
USB port to talk to a PC, tablet, net book, notebook,  etc., etc.

I am not advocating Megasquirt as it is not optimized for  aircraft use
and it has a steep implementation and learning curve despite  its open
software and hardware. I am advocating a much higher res EM2  display
screen and or a USB interface.

Tracy's computer already has  one or more serial interfaces that
can be converted to USB ports. Here are  some examples of cheap hardware
that can do it. The PC software can be  programmed in something
simple like Visual Basic.

It would be way  less of a tuning problem if everybody built P-ports.
That is the closest  thing we have to a standard intake manifold
configuration over a wide range  of 13B engines starting in 1973 up
to the current RX8  engine.

Unfortunately there are a lot of engines still out there  with
all sorts of variations on side ports not to mention some with  turbo's.

The side port engine can be a nightmare if there are two or  more resonant
intake systems in series. The stock RX8 intake manifold is a  classic
example.

Paul Lamar


I believe that the EM3 has such an interface as an option.

Rich

Excerpts from Tracy's web site.

------------------------------------------------------------------------
EM3 Engine Monitor


Data Logging (Parameters logged at 1 second intervals. Includes software to display data on PC)     $259.00 additional



The EM3 is designed with a separate data acquisition module (as opposed to the integrated, one piece design of the prior EM2 unit).  This allows the data acquisition module (DAqM) to be placed closer to the engine sensors, which can simplify the number of wires running between the engine compartment and the instrument panel.

The DAqM utilizes screw terminal blocks (instead of the connectors used on the EM2), simplifying wiring and eliminating the troublesome soldering of thermal couple sensors to connector pins.  The DAqM is connected to the display by a simple 3 wire connection.


The data logging option allows recording of all monitored engine functions at one second intervals.  Data is logged on a common, inexpensive USB thumb drive.  Even a small thumb drive will hold hundreds of hours of data.

The data logging option includes software to display engine parameters on your laptop or PC.  This can be invaluable for analyzing engine, cooling and other system performance problems.
-------------------------------------------------------------------------------

This is a step in the right direction but it is not what I had in mind
for easier tuning. It is no where near what Megasquirt offers.

The price is high as one can buy a data logger for about $100.

Here is a good one I have used on a Rotary Powered Mustang II.
From the sounds of Tracy's web site this data logger is wired
in a similar fashion with direct connect to the sensors or
injectors and coils.

http://www.hytekautomation.com/Products/IUSBDAQ.html

Does anybody have an EM3 with data logging?


Paul Lamar