To kick this one off – why
go to fuel injection?
Well, the answer is in three parts really.
The first is that I was never 100% happy with the Zetec on
carbs. I’m sure that with lots of playing around they
could have been made to work. The problem I believe was all
down to the progression phase of the fuelling. The carbs were
fine on the x/flow and I believe that the main difference
is that a 16v engine requires the main jets to be brought
on earlier than an 8v engine. You can have an extra progression
hole drilled in each chamber of the carb and if I had been
staying with carbs I may have tried this. This problem manifested
itself as a hesitation to pick up from lower rpm giving a
very much two stage engine feel – cruising or blatting.
The second part is that the trouble with carbs compared to
fuel injection coupled to a re-programmable ECU is that to
make any changes to the fuelling you have to have another
set of jets to hand, and these will then most likely effect
another set of jets. The quickest way is to book a rolling
road and spend a while checking different combinations –
which costs. Before this modification I didn’t realise,
or rather appreciate, the ease of making a fuel correction
sitting at a laptop in the garage, or at the side of the road.
I had reached a point where I wanted a bit more power, which
may have just been linked to the first parts above, drivability,
but more power is always nice – you don’t have to
use it. Right? Anyway, the next stage to more power is to
fit some up rated cams, which in turn need a ported head to
deliver their potential (both of which I will get to later).
The higher flow of air means you need to supply more fuel,
which would need loads of time spent of a rolling road. The
ECU allows you to adjust this on-the-fly. Brilliant. The carbs
would have limited the flow of air as they were only 40’s
which I felt were already limiting the engine.
So, to summarise, fuel injection allows easy adjustments of
the fuelling to match the needs of engine, whether tuned or
not. This meant that I could up rate my cams and fit a ported
head and tweak my fuelling to suit. It also allows much finer
control which means you can run a larger choke size, which
gives more power, but you don’t suffer the torque reduction
you would with carbs. The final reason, which doesn’t
really relate to how the engine performs is that with the
Gems ECU that I had running the ignition with the carbs, the
car was unreliable starting. I had tracked this down to the
way that the ECU read the crank position sensor. It basically
didn’t seem to wait long enough to fully determine where
the engine was, which meant that it would fire too early,
with the engine not fully up to cranking speed and it would
stop dead. I had fitted a work-around switch which allowed
me to spin the engine before firing up the ECU, which would
then fire as soon as it saw the signal (I rarely used this,
it was just a backup plan for my peace of mind).
So, how to go about it? I had a few things to decide. The
first was obviously what to do – how far to go with
things, what would everything cost, what would give me what
I wanted – a drivable engine with good power and torque.
The power side of things would dictate the rest of the project,
in terms of what I would need, so it was the best place
to start. I knew from a friend, Brent, that Piper
285 cams and a ported head would give around 200bhp. His
engine remained tractable which I wanted. I toyed with the
idea of fitting Kent
FZ2002 cams, which are of a similar spec to the Pipers,
but decided to go with those so I could tap into the knowledge
that Brent had gained during his upgrade. I then needed
a ported head – for which I already had a plan. I had
bought a spare head from a friend of Brent’s a year
previously. I had done so with the intension of having a
go at porting it myself. This I chickened out of, plus my
work went chaotic and I didn’t feel that I would have
enough time.
Next I would need a pair of throttle bodies. For these
I had only two options, the first was the easy option of
Jenvey
DCOE replacements. These simply bolt in place of the DCOE
carbs, onto the same inlet manifold. The other option is
to take a pair of modern motorbike throttle bodies, which
are typically individual, and fabricate / modify an inlet
manifold to suit. The throttle linkage would also require
some work to make sure they all opened together and could
be balanced. Needless to say, I took the easy option. The
main one was, again, time. I think it would have been quite
good fun to make everything for bike TB’s, but my time
was too limited to consider this. The other reason is that
the Jenvey TB’s look great – they are even the
same colour as my cam cover.
The last piece of the puzzle was the ECU. For this I didn’t
take the easy option! This would have been to buy an off
the shelf, the favourite being an Emerald.
The Emerald was designed to replace the Rover Mems ECU of
the K-series engine and simply plugs straight into the same
connector. Job done, other than mapping it. For my application
I would need to make, or get made, a loom to connect it
to the car. The option I took instead was to go for a DIY
ECU called Megasquirt,
or MS. This is an open source web based project that started
life several years ago in the US. The basic premise was
to design a unit which would be fitted to almost any vehicle
and could control a fuel injection system. It started out
as simply a means to add fuel injection to your carb fed
engine. The unit would take an ignition pulse from a distributor
and determine when to fire the injectors. The other task
it could perform was to replace a current injection control
system with one which the user could then re-program. I
suspect that the latter is now the most typical use, as
most cars are now FI to start with. The unit is incredibly
flexible and project examples range from 4 cyl cars, high
revving bikes, V8’s and rotary’s. I have even
seen someone claiming to have fitted it to a single cylinder
Briggs & Stratton lawn mower engine! The problem is
that as cars have become more complicated and most ECU’s
now control both ignition and injection in one. To cope
with this the MS has a number of off-shoot projects which
utilise the core design but which add various ignition control
methods, usually using some standard manufacturer’s
module. This is precisely what I have gone for. The project
I initially picked was called the MS’n’EDIS but
this was merged with a couple of other projects to form
the MS’n’Extra
code variant. This would give me the ECU’s normal control
of the FI and also a signal to drive a standard Ford EDIS
ignition module and wasted spark coil pack (both of which
were used on Zetec Escorts and Mondeos as well as some late
CVH engined cars). This system was perfect for my car –
as you will have spotted the Zetec word mentioned –
it was almost designed for my set-up.
Another key selling point is that you can tune it yourself
if you have a suitable lambda EGO sensor (Exhaust Gas Oxygen).
This gives a readout based on the exhaust gases and will
tell you if you are running rich or lean. The preference
is for a wideband sensor over the narrow band flavour as
this specifically tells you what you have as a figure whereas
a narrow band can only say if you are rich or lean, not
by how much. Pump gas fuel gives an ideal lambda reading
of 14.7:1, known as stoichiometric, but for power you want
it richer than this, between 12.5 and 13:1 for a nasp engine.
Having it richer also prevents the engine getting too hot
as the slight excess of fuel helps to cool things down.
The MS ECU can take an input from the wideband sensor and
use it to adjust the fuelling.
It can also data log all of the input channels to a laptop
and this can then be used at a later date to determine changes
to the fuelling map. The tuning cycles is therefore determine
a starting map and go for a drive, interpret the results,
adjust map, go for a drive… and so on.
Oh, and the DIY thing – you have to solder all the
components onto the PCB yourself, make the loom, create
your map and try to get it working…
So there we go – the decisions made, next was to put
it all together, in some kind of order and get it working.
NOTE: I have since changed the ECU to an Emerald due to
various issues with the Megasquirt but have decided to leave
te information here for anyone looking for information.
You can read about the Emerald swap here.
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