EDIS on a supercharged B

If you have read the other pages on how EDIS works, then what we are looking at here is the fitment with the specific difference that the front pulley on a Hi-Flow s/c'd car is very different to a standard B Series front pulley.

• Fitting the Trigger Wheel
• Fitting the VR Sensor
• Fitting the Throttle Position Sensor
• Fitting the Coil Pack
• Linking up and starting
• Comments
• An update - 29th May 2006
• A trigger Wheel on a Moss pulley

Phil returned to the UK recently for a short break away from his Australian studies to catch up with his mistress, and one of the jobs scheduled was to fit the EDIS system to partly allow for a dedicated advance curve and overcome a worn distributor.  Whilst a new distributor might have shown equal benefits in smooth running, the EDIS has the advantage that has he upgrades the engine to the special cam and vernier pulleys at a later date, he can then re-map the advance curve at each stage.  Our thanks to Matthew Kimmins for his assistance on the final fit.

Fitting the Trigger Wheel

Being a 1972 c/b car, access is impossible to the front pulley, so the job will start with removal of the radiator, which offers a nice view on completion of the serpentine path of the s/c belt.  This was an ideal time to change the coolant, too, as part of an overall service we carried out this last week.

Now, of course, the crankshaft pulley is the focus of attention in order to mount a trigger wheel.  It has to go here to avoid any timing errors that may result from slippage of the belt.  On closer inspection of the crank pulley we noted that it had a sophisticated locking tab as shown below.

The pulley has very little clearance with the steering rack although we measured 14mm which seems to be a little more than the 10mm measured by Michael Beswick on his Moss equipped s/c'd Roadster.  However, we compounded the problem by fitting a new steering rack as part of an MOT to-do list and probably reduced this clearance by about 1-2mm.  However, the pulley is approximately 140mm, so before Phil got here, Matthew Kimmins ordered up a 5.75" (146mm) trigger wheel with 1/2" pilot hole from Trigger-wheels.com. (See photo below, showing the trigger wheel marked up for cutting.)

Our immediate thoughts were to remove the locking tab, and to cut the trigger wheel to fit over as a new permanent locking device.  Of course, had we not tackled this on a Friday evening, we probably could have drawn up the dimensions we needed and had a machine shop cut out the trigger wheel to the same dimension as the locking tab, with recessed bolt holes to aid clearance, too.  But a few hours on Saturday morning with the drills, Dremel and file soon got a decent enough hexagon cut in the centre with four holes drilled for the holding bolts.  Given that the trigger wheel is 5mm thick laser cut wheel, this took up a good proportion of the available clearance, and add the bolt heads in, and it's a very tight fit as you can see here - but so far so good!

So there we have the first stage done. This is probably the most difficult part of an EDIS fitment, although much easier on a r/b car where the radiator can stay in position.

Fitting the VR Sensor

The next stage is to position the engine to TDC on number 1 piston, and to make a bracket to hold the Variable Reluctance sensor.  As per Matthew Kimmin's guidelines we positioned the sensor at 9 o' clock, with the missing tooth at 12 o' clock.  In order to hold the sensor, we made up a bracket from sturdy metal - in fact one of the top-hat section bush brackets from my rear anti-roll bar I binned a few years back when I lowered my r/b BGT.  We located the end on the lowest front plate bolt (we used a slightly longer bolt to compensate for the bracket thickness), and shaped the bracket to pass around the belt with clearance in case the belt ever worked loose.  The final fit looked as per the photo below.  The pulley had very minimal run-out and allowed for the sensor to be mounted within 3mm of the trigger wheel.

Fitting the Throttle Position Sensor (TPS)

The final fabrication involved mounting a TPS onto the carburettor spindle.  Although the EDIS system normally employs a MAP (Manifold Absolute Pressure) sensor to tell the EDIS module what load is on the sensor, Matthew Kimmins has always employed a TPS instead - the inlet manifold on a standard B Series SU set-up doesn't seem to encourage steady readings for the MAP - however, on a s/c'd B, this is of course under pressure rather than vacuum.

I am assuming the Moss unit is the same, but on the Hi-Flow supplied SU HIF 44, the throttle spindle, unlike the earlier HS/HIF, has two flats on the exposed side away from the linkages and cables.  This meant we could use some suitable flattened s/s tube to act as a connector between the TPS variable resistance pot and throttle spindle.  As the oil reservoir on the side of the supercharger had a reasonably substantial bracket we used this to mount the TPS as below (the reservoir is unclipped in the photo to show the attachment to the existing nut/bolt).

Fitting the Coil Pack

The final stage of component fitment before Matthew could begin his task of final wiring is the coil pack.  Whilst there are a variety of places to chose from, and we looked at the bulkhead as an option since Phil does not have a remote servo, we settled for the right hand inner wing.  I used the bulkhead on my 1980 BGT as I have an inline servo, but on most others it is usually around the area of the original coil.  It is a case of keeping the coil pack near the EDIS module box to minimise wiring length and electrical noise, but then needing longer HT leads to the plugs or vice versa.  Phil's car previously had his windscreen washer bottle on the right-hand inner wing just behind the radiator diaphragm, so we moved this to the earlier location over on the bulkhead on the left hand side.  This gave us adequate space to mount the coil pack, although we should have really moved it higher up as the oil cooler hose runs a bit close now.  We used long self-tapper screws fitted through lengths of cut fuel pipe (to act as dampers) to mount the coil pack to the wing, as per the photo below.

Linking up and starting

By this point, having refitted the radiator, the final connections between the coil pack, VR sensor and TPS were made into the EDIS module inside the car.  A couple of small issues, such as getting the leads in the correct order on the coil pack were sorted, and she fired up!  But at 10.00pm on a Saturday evening, we decided to call a halt given the likelihood of the neighbours being upset by the rumble from the garage.  I should point out that although having started on Friday evening removing the radiator, we were side tracked on a fair number of occasions with meals, friends visiting etc, so in reality the job should not be a whole day.  But it was rather satisfying to look at the view below showing the laptop and EDIS module on the centre console.

Comments

Well, disappointingly, the car did not have the pep of the original distributor.  In fairness, the original settings had been done on Peter Burgess's rolling road, with a measured 110bhp at the rear wheels, and I have to say that since repairing the HGF last year, it had been a different beast altogether, with superb performance - something I had often emailed Phil about much to his dismay being in Australia thousands of miles from his car!

Ok, so what went wrong?  I think we ran out of time to do it justice.  The initial map was a guess to begin with, one that has worked extremely well on my 1860cc stage 2 engine - as many will attest given the ability to rev to in excess of 6500rpm!  However, on Phil's car, the improvement in starting and the smooth tick over were testimony to the potential of the system once it is properly mapped.  We found that by pushing the idle advance up to 34° we got a very smooth idle, compared to the lumpiness at a figure of 12°.  However, one thing I have learnt is never to take values as absolute, so we got the timing light on the front pulley and discovered to my horror that somehow in mounting the trigger wheel I had induced an offset of about 17° which means this will have to be added to the numbers when we create a new map.  Or we may be able to reposition the sensor to take up this difference.

Another issue is the tachometer.  Whilst it works ok on mine, for some reason the tachometers fitted on the 71/72 years had a feed from the ignition through the tachometer to the coil.  We managed to get a reading on the rev counter, but weirdly at 1/2 the actual engine revs as shown on the runtime display on the laptop.  Matthew Kimmins is working on this.

I think a session on the rolling road again with the laptop making life so much easier will bring improvements to the performance.  The benefits are of course still there with EDIS, even if we only match the previous performance on the distributor, although I am sure we will see a gain given the wear on the old unit.  The benefits of the EDIS are:

• the easier mapping after each engine upgrade (cam, vernier pulley, increased boost etc.) with an infinite number of permutations compared to playing with spring tension and bob-weights,
• the fact that the system stays in tune permanently, and apart from checking the spark plugs and valve clearances, will reduce the service effort, especially as the plugs should last longer, too,
• smoother running and easier start-up (which, in fairness, would be achieved by a new distributor, but at a similar cost to EDIS),
• a built in rev-limiter and shift light out-put!

Do check back in the near future for more updates as we find the time to fine tune the settings.

An update - 29th May 2006

Well, the puzzle of the very advanced timing has been solved.  The photograph taken by Matthew Kimmins below shows what happened during the fitting up.  Somehow, compared to my earlier photos above, the sensor got re-positioned and is pointing at the tooth above the marked tooth, hence it is reading at least 10° too late.  So this should be a simple fix.  Once we find the time!

June 2006

Seen recently at Silverstone, this car, equipped with Moss s/c unit, and EDIS set-up.

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