During the summer of 2006 I really started to make some
progress with my Megasquirt
ECU. I had suffered a number of problems, mainly fuel pressure
and mapping related.
After I got some of these problems sorted out I really started
to make some progress with the mapping. With the introduction
of an 'AutoTune' function that actively adjusts the map
against a target AFR map according to the wideband sensor
input things really seemed to start to come together.
At the time of my MOT test the mapping up to around 5000
rpm was pretty much finished, and as I drove home again
I did have to wonder why I was about to rip the Meqasquirt
out. However, the route home didn't involve any extended
revs and that is where the problem existed.
As the mapping had started to progress, so I had been able
to extend the rev range that I was using and venture to
higher rpm on a more frequent basis. I started to notice
that I was suffering from what felt like a misfire at about
4500 rpm. When accelerating it wasn't really noticeable,
only occasionally did I feel it. The problem was mainly
apparent when I held consistent revs in the problem 'zone'
at which point I would see all my shift
lights flash and feel a slight loss of power/hesitation.
When I checked back through some datalogs form the ECU I
could see no sign of a problem so I concluded that the problem
must be elsewhere. I tried a new crank sensor, and new spark
plugs. No change. I borrowed another coil pack and EDIS
unit (thanks Steve!) but again, no change. I then ran the
engine in the garage with the lights off and I could make
out some slight tracking along the HT leads. I bought a
new set from a local motorfactor and after an jubilant test
drive where the problem seemed to have gone, I gave the
engine some beans and was dismayed when I saw the shifts
flicker again. Another garage test and the leads still seemed
to be giving some tracking issues, so I arranged for some
high quality leads to be made to my measurements (slightly
different due to a Raceline
coil mounting plate). Again, the engine seemed to run better
but the problem remained.
Whilst driving to work I had one of those bolt of lightning
moments and thought 'I wonder if it is a rev limiter in
the ECU'. When I got home I had a look and sure enough I
had a limiter set for just over 7k. I effectively disabled
this by increasing the rev limit to above 10k and the problem
was gone. The shift lights would still flash, but the misfire
had gone. From this I deduced that the problem was the ECU
was getting a false trigger for the engine speed and this
was triggering the shift lights, and previously the rev
I next called on help from Kevin (Megasquirt guru with Zetec
Westie) and we arranged for me to pop down to him so he
could have a look. Kevin hooked up an oscilloscope and checked
various points on my loom and found some noise during the
closing of the injectors. To try to get rid of this I changed
a large part of the loom to move the ground all back to
a single point. Unfortunately it didn't make any difference.
It was at the point that I pretty much decided that I had
had enough of trying to find the problem. I didn't want
to give up the ECU as I had invested a lot of time and effort
into it and had enjoyed both the build and the learning
involved. However, I had to call an end to the seemingly
endless problems and throw in the towel. I don't have the
electronic knowledge and I didn't want to be reliant on
others to try and help me not just in the short term, but
obviously long term as well.
So, when I got back from the MOT, I ripped out the Megasquirt
and set about fitting an Emerald
M3DK ECU. I changed the location for the ECU from under
the dash where space was too tight to into the engine bay.
I also took the opportunity to fit a relay and fuse box
as I was removing the relay Board. As all the old wiring
went into the dash area, everything was long enough to reach
the new location, so it was simply a case of working out
the pin numbers and plugging the cables into the appropriate
positions. I got a starting base map from Brent, whose Zetec
was a similar spec when he fitted an Emerald.
Once completed, the engine started first time and ran much
more smoothly, so I can only assume that the ignition problem
was effecting the engine across the entire rev range. For
the remainder of the year I worked on tuning the map using
Good script and got a reasonable amount done. The only
problem is I am struggling to map the higher rev ranges
because a) everything is happening to quickly and b)you
simply don't get an awful lot of opportunities to use the
high revs on the roads. A rolling road day may be the order
of the day.
At the end of the day I have to say that I enjoyed the Megasquirt
experience and would have liked to have kept the ECU on
the car as I do like the idea of open source and some of
the developments being made were really quite cool. However,
I had to admit defeat and I have to say that the Emerald
experience was, and still is a very good one. I have had
excellent service from Emerald and as mentioned above, everything
worked first time. The Megasquirt is living on though, as
Tony has taken on the project for his K-Series car which
he is planning on upgrading with TB's and I believe he is
currently staging the upgrade so the Megasquirt will control
the injection and the standard Mems controlling the ignition.