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 a Weber carburettor
with turbocharger which is quite a common combination and found
on cars like the Lotus Esprit Turbo.
 
Complications with tuning meant that they subsequently reverted to the standard
 Bosch K-Jetronic fuel injection, but the maximum fuel flow through the Bosch
metering system would restrict 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

 

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.
 
The box is now long-obsolete and nobody has the necessary data to be able to
programme alternative EPROM chips.
 
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 from (if I recall It has the same label indicating that it was tested ok
correctly) Build 013 that was being converted to at Tickford on 23/8/89
a Cosworth engine  
   
   
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  

 

Think I'll convert the photos of the AFT boxes into a "Spot the Difference" game
and get them in the shops for Christmas!

 

 

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 has
forced a move to an alternative.
 
The MicroDynamics EMS5 Turbo Ignition Management and PIC5 Auxiliary Petrol
Enrichment System has been used with varying success.
 
Personally, I thought about a fully-tuneable system from DTAFast at one point.
 
It would be great to have the ability to monitor and tweak just about every
parameter, but I don't want to lose the characteristics and "feel"
of the original Tickford set-up.

 

   
The MicroDynamics system installed on Build 001 The DTAFast totally programmable system -
(bolted under the glove box) versatile, but hardly original!

 

 

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