AFT Ignition System

 

 
AFT ignition box on the left
Fuel Injection Control Unit on the right

 

Early tests on the prototype cars used the standard Capri 2.8i distributor
with minimum static timing set to avoid detonation.
 
We are talking 1982 and the concept of computerised engine management systems
 was in its infancy, especially for a low-volume vehicle that was
 desperately trying to keep its costs down.
 
At the time, Ford were producing the Escort RS1600i that used a computerised
ignition system from AFT (Atlas Fahrzeug Technik GMBH) with a magnetic
flywheel trigger to sense engine speed and rotational position.

 

 
The Ford RS1600i

 

While Ford were assessing the prototype cars, they expressed concern about the level of ignition
control on the Tickford and allowed access to a modified version of the AFT black box.
 
The factory in Germany reprogrammed the EPROMs with calibration data for the Capri.
 
The magnetic sensor on the flywheel proved to be a bit of a challenge.
 
 A tiny strip of mu-metal had to be micro welded on to one tooth.
 
A position was chosen to minimise contact loads from the starter motor - the flywheel
would only ever tend to stop in one of three positions,
as a piston was coming up to compression.
 
The welding had to be conducted very carefully to make sure that the magnetic
 properties of the strip were not destroyed.
 
While RS1600i production continued, Ford did the welding for Tickford.
 
Subsequently, Tickford were given the special spot welder
so they could do it themselves.
 
The actual pick-up for the magnetic strip was a stock RS1600i part,
inserted into a hole that had been drilled in the bell-housing
 and secured with a small bracket.

 

 
The magnetic sensor

 

Tickford's initial engine development had been based around the German
RS 2800 Werksturbo Capri that used the Cologne engine block with
a Garrett T4 turbo and singe Solex twin-choke carburettor.
 
Complications with tuning and mechanical issues meant that they subsequently
reverted to the standard Bosch K-Jetronic fuel injection, but the maximum
fuel flow through the Bosch metering system restricted
peak power to around 190bhp.
 
Tickford therefore added a 7th injector in the main air intake to the plenum
chamber, facing into the compressed air flow from the intercooler.
 
This ensured an even distribution of the additional fuel and further assisted
 with cooling the charged air.

 

 
The 7th injector - straight into the boosted airflow which helped
to provide an even distribution of fuel in the plenum chamber.

 

The additional fuel was only required at certain combinations of high engine speed and load,
so a bespoke Fuel Injection Control Unit was built by Electronic Racing Aids
in Birmingham (who later became Zytek).

 

 
Label from the Fuel Injection Control Unit

 

The control unit had a connection to the negative side of the ignition coil for sensing
engine speed and measured boost pressure via a split from the feed
to the AFT black box and boost gauge.
 
The unit must have had its own programmed EPROM chips inside,
but I have yet to explore this in more depth.
 
The standard Capri fuel pump was man enough to cope with the additional injector
so no modifications were needed in that department.

 

 
Diagram of the Tickford Capri ignition system

 

 
Photograph showing location of the 7th injector and air temperature
sender in the main charge air pipe coming from the intercooler.
 
The throttle switch is on top of the throttle housing.

 

Below you will find scans of the original data used to program the AFT boxes.
 
The graphs plot ignition angle against vacuum / boost pressure and RPM.
 
Click each thumbnail to open the graph in a new window

 

   
Field 0    >75 degrees C Field 1    50 - 75 degrees C
   
   
   
Field 2    25 - 50 degrees C Field 3    <25  degrees C
   
   
 
Field 1    50 - 75 degrees C    +480 millibar
 
Many thanks to John Atkinson (Build 073) for providing these scans

 

Chris Bale, who was the Lead Engineer for the Tickford Capri project, has kindly taken
the time to provide a detailed explanation of the graphs for us:
 
 

 

The AFT system can be a headache for Tickford Capri owners.
 
The black boxes are considered to be un-reliable and while they were still available,
replacements were horrendously expensive.
 
Then to make it even more complicated, there were several different versions of the box!

 

   
The bottom board always contains the EPROM chips The top board has the main driver transistors and some
and boost detector (top right) versions also have the switching transistors

 

So to confuse everyone completely, here is a rogue's gallery of boxes........

 

   
This is Box 89/110 that I bought from Tickford as a spare The number 407.003 is actually an AFT part number
in 1991 and it has a label saying that it was tested and not an Aston Martin one
and working on 23/8/89  
   
   
Oh Great - the top board is different again compared to The switching transistors are on the
the two variants photographed earlier bottom board
   
 
   
   
This is Box 89/112 that I acquired later It has the same label indicating that it was tested ok
  at Tickford on 23/8/89
   
   
Oh Joy - the top board is the same as 89/110 Yep - identical!
   
 
   
   
Just when you thought it was making sense, here is the old This time we have an Aston Martin Eprom number of 400.165
box from Brian's car Build 031 where everything is and the same AFT part number of 407.330
mounted on a single board, even the driver  
transistor surrounded by a heatsink  

 

 

The reputation for the un-reliability of these boxes is a little unfair.
 
It is actually a very good system and most faults are either caused by other
components of the ignition system (e.g. ignition coil) or exposure
of the box itself to voltage spikes and/or static discharge.
 
In the case of my own car, the first fault with the black box was simply dry solder
joints failing under excess vibration.
 
On the majority of Tickfords, the box was mounted on a proper metal bracket bolted
to the lower dashboard behind the centre console.
 
Of course, this cannot be done on the Tickfords that have their radio in the centre console
as there just isn't room - mine had its mounting tabs cut off and was stuck to
the back of the lower dashboard with a bit of glue.
 
Over time it had become loose and free to bang around!

 

 
The correct location for the AFT box (photo is of Build 031)

 

Whilst the mounting of the main AFT box did vary,  the Fuel Injection Control Unit
was always bolted to a metal bracket under the glove box without exception.

 

 
Fuel Injection Control Unit is tucked-up behind the glovebox to the right of the
on-board fire extinguisher in my car
 
You can see the vacuum hose and multi-pin connector running to it

 

For a few Tickford Capri owners, problems with the AFT system have forced a move
 to an alternative, generally one of the MicroDynamics systems which require
the original Ford DuraSpark electronic ignition box to be retained.
 
 
 
 
Interestingly, between abandoning the RS 2800 Werksturbo research and settling on the
 AFT-based system, Tickford experimented themselves with MicroDynamics units.
 
 
 
Early photo of the prototype car in "test mode" shows an unidentified black box mounted on the offside top
of the bulkhead and no sign of the DuraSpark box or 7th injector.......confusing!
 
As a workhorse, the engine bay of FMJ624Y was becoming a little tatty and even
 the plastic retaining clip for the bonnet support was broken!
 
The engine bay photo highlights a number of differences and points worth mentioning:
 
Both the early prototype cars FMJ624Y and FMJ625Y were supplied as blue over silver 2.8i Capris and
then re-sprayed by Tickford, who decided that the engine bay of FMJ624Y
would look better in black to show off the engine and ancillaries.
 
At this time, no brass Tickford VIN plate on the front valance - more like a load of plates stuck on top of each other.
 
Lead Engineer, Chris Bale believes that the unknown black box may be an early version of the ERA
Fuel Injection computer used to control the 7th injector or some unknown ignition box.
 
The main charge air pipe running between intercooler and plenum chamber was made up of several black sections
where on all the other cars, it was a beautiful one-piece stainless steel affair.
 
 Chris Bale thinks there may be a 7th injector hidden underneath the straight black section as early experiments
 placed the injector down-stream of the charge air flow.  Tickford later changed it
to up-stream to improve mixing of the air and extra fuel.
 
 Chris also observed that there may be no 7th injector installed at all, as at one point Tickford
 tried using the cold start injector to add the additional enrichment fuel.
 
Charge air temperature sender seems to be mounted on the side of the plenum chamber, or it
may be a boost pressure sensor if there is a hidden MicroDynamics system somewhere.
 
Note the tarnished exhaust exiting from the turbo and dis-coloured water reservoir - symptoms of heat build-up.
 
The heat shields around the main exhaust were missing - they were supposed to protect the power steering
pump and wiring that ran down the side of the inner wing from melting.
 
All the later Tickfords had the fuel filter mounted on top of the inner wing beside the ignition coil, but on FMJ624Y it was

 bolted to the side of the inner wing.......right beside the main exhaust pipe that had no heat shield!

 

 
Different "show mode" photo of the prototype car with a MicroDynamics EMS3 mounted on
the inner wing and there must be a DuraSpark box hidden down the side
as you can see its two multi-pin plugs beside the EMS3,
but still no 7th injector.

 

The factory diagram scanned below shows the wiring for the combination of Ford DuraSpark
electronic ignition with the MicroDynamics EMS3 Turbo Control System:
 
 
 
The instructions mention the use of a MicroDynamics MacroSpark coil
 
I can't find any reference to this unit on the Internet, so they may have
meant the MegaSpark 2 coil as instructions for one of these was
found in the factory files after it closed

 

Before we go any further, here is the "Observer's Guide" to MicroDynamics boxes:

 

   
EMS3 Turbo Control System MegaSpark 2 coil and ballast resistor
   
   
   
EMS6 Boost Retard System Adjustable Boost Switch
   
   
 
EMS5 Turbo Ignition Management System with PIC5 Auxiliary Petrol Enrichment System
 
These are the boxes used on Build 001 after its recent total restoration

 

It wasn't until I started to research the information for this page, that I realised
just how many Tickfords are now running MicroDynamics systems
in addition to Build 001 above:

 

 
Build 026 - DuraSpark and EMS6 Boost Retard System
 
 
 
Build 028 - DuraSpark and EMS6 Boost Retard System again
 
 
 
Build 036 prior to restoration
 
DuraSpark, EMS6 and MicroDynamics Adjustable Boost Switch where the air temperature
sensor should be -  this optional switch is used to activate the EMS6
 
 
 
Build 056 - Unidentified engine management system to nearside of bulkhead
 
PIC5 Enrichment System, no sign of a DuraSpark
 
 
 
Build 057 - DuraSpark, but no sign of a MicroDynamics box
 
 
 
Peter Theunissen's Alternative Tickford Capri
 
DuraSpark and EMS3 Turbo Control System as per the slightly later prototype Tickford

 

I am assuming that all the cars fitted with just DuraSparks and EMS6 Boost Retard
Systems still have their original Tickford Fuel Injection Control Units
working and controlling the 7th injector.
 
This is quite feasible as the Fuel Injection Control Unit only needs a feed from
the negative side of the coil and a sample of the boost pressure.
 
Build 056 has a PIC5 Enrichment System, so I'm guessing that its original
Tickford Fuel Injection Control Unit died.
 
Cars running the EMS6 Boost Retard System should have just a boost
sensor which seems to usually be mounted on the side
of the plenum chamber.
 
Cars with the EMS3 or EMS5 systems will have a boost sensor and a
over-boost protection switch, both normally found on the side
of the plenum chamber.

 

 
Boost sensor and switch on the plenum chamber of Peter Theunissen's
Alternative Tickford Capri
 
 
 
But they are missing on the prototype car that is supposed to
have the same system!

 

Finally (for now at least) here are scans of the instructions for the various
MicroDynamics units that were kept on file at the Bedworth factory
and they all date from around 1985 / 1986:
 
Click on each thumbnail to open it full size in a new window

 

   
MegaSpark 2 - Page 1 MegaSpark 2 - Page 2
   
   
 
EMS 3 Turbo Control System
 
 
   
EMS5 Turbo Ignition Management - Page 1 EMS5 Turbo Ignition Management - Page 2
   
   
   
EMS6 Boost Retard - Page 1 EMS6 Boost Retard - Page 2
   
   
Many thanks to Chris Richards from the Tickford Capri Facebook Group
for generously providing scans of all these instructions

 

So to complete the story, there are still a few things I need to find out:
 
Instructions for the PIC5 Auxiliary Petrol Enrichment System
 
Exactly what system is being used on Build 056 and 057?
 
Just how successful are the MicroDynamics systems?

 

 

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