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Ignition Investment - UPDATED

Simeon

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blog-0414931001447836302.jpgAfter reading good things on the FAQ and reviews around the web, I decided to invest in a Summit Racing 'MSD' CDI ignition. I have to say, this is an impressive package. EVERYTHING about this product (build quality, instructions, part numbers, specification, installation kit etc) screams that this is an MSD product. If MSD are not making this, or getting a cut out of Summit, I would be very surprised and I would suggest that MSD need to get a better lawyer.

http://www.summitracing.com/int/parts/sum-850610/overview/

Opening the box we have the sturdy unit (Aluminium heat sink case), wiring harnesses with good quality sealed plug couplers at the one end and well installed crimp terminals at the other. There is a comprehensive fitting kit with all manner of small parts that someone may have thought would be even vaguely useful (it even comes with a small screwdriver for adjusting the rev limiter pots). They really have tried to think of everything here. The installation instructions I have given below are really the same for a real MSD branded product as there is no difference that I can see between this and a MSD 6AL digital or similar at least as far as configuration, if not performance.

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I have been slowly modifying my ignition system in advance of future engine modifications and in an attempt to rid myself of a persistent low RPM misfire that gives me an unsteady idle. Ultimately I intend to get a 123Tune distributor but in order to try and delay that, I have gone down this road (with a view that this can be perfectly switched by the 123 at a later date). At the back of my mind, I am concerned by reliability and while the postage from Summit to South Australia was pretty quick, I don't want to be completely stranded if the box should go on the fritz so I needed an installation that would allow me to revert to conventional points / inductive ignition at short notice.

I had originally intended to use my original, well worn, vac advance distributor with a Hot Spark Pertronix knock-off to switch the unit but gave up with the Hot Spark when I went to all of the trouble to fit it, just to find that it was not working. I gave up and pulled the whole distributor, replacing it with a distributor that I had on the shelf that someone had modified its curve and removed the vac advance. This is in better overall condition (less jumping of the timing marks) but I had put it to one side as I really wanted the advantage of vacuum advance for my (currently) mildly tuned street motor. I will take the vac advance distributor to a local specialist to see how much they charge for a rebuild (or put the money towards that 123Tune).

The CDI box works without a condenser, with the points acting as a simple low voltage switch which then trigger the firing of a capacitor which charges quickly, quicker than the difference between each cylinder firing in turn. This removes all of the concerns about the reduction in time for the coil primary field to charge as the revs rise. It also allows, in the case of a 'multiple spark discharge' ignition like this one, multiple sparks for each cylinders compression stroke under 3,000 rpm. This improves the ignition at low revs through extending the 'burn time'. With a CDI ignition, the coil works more like a conventional transformer, transforming the now raised primary voltage of approximately 480v to up to 40,000v (depending upon the coil primary to secondary ratio).

The first job was to mount the unit in the engine bay and plan the routing of all of the wiring. I chose an area on the front of the right hand inner wing. After drilling the mounting holes, I used the included resilient rubber mounts in the rear. The jury is still out as to whether these are entirely necessary - the concept seems to be for 'high vibration' applications, which mine probably isn't and some people say that they allow circulation of air in rear which may be more important for longevity. The unit has two plug couplers and flying leads for battery + and ground. The battery + wire was run around the front of the engine compartment to connect to the battery positive terminal. There is no fuse in this wire so to minimise risks of short circuiting causing it to overheat it was given secondary insulation with some loose plastic wiring sheath and tied to existing looms running behind the radiator. The ground was extended by soldering in a new length of 4mm2 wire and run with the battery + around to the battery negative terminal direct. No problems with poor power connections here.

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The wiring loom with the small plug coupler is run to the ignition coil. Here the orange and black wires connect to the coil + and - terminals respectively and the red wire is connected to the green switched ignition12v wire (which is now disconnected from the coil) using a male 1/4" terminal. The orange and black wires will be live at up to 480V so it is best that you stay away from them when the ignition is on - I added rubber boots from an electric fuel pump over the wires to avoid accidental contact. It is also worth remembering that you will not be able to measure 12V at the coil terminal any more as this will only be live in pulses when the capacitor is delivering the 480v into the coil primary since it does not need to charge an electric field within the coil.

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The second loom, from the large plug coupler, runs toward the distributor. One section of loom is the 'magnetic pick-up' wiring (green and violet) this is terminated on a two pin plug coupler and in my application is unused. There was a lot of this to 'lose' tidily within the wiring so I cut the wires off short and insulated with heat shrink.

The white and the grey wires from this loom were initially run around to the distributor before I established the need for the tacho adapter. The white wire was directly connected to the points at the distributor which are switching the CDI box's connection with ground and the grey tacho wire was run around to connect with the black wire that was previously connected to the terminal on the distributor. The section of black wire between the distributor and the coil was left disconnected previously at the coil and secured out of the way / insulated.

I wanted to retain the distributor through body connector with the two male 1/4" terminals associated with the condenser so I took an old spare condenser, cut the wire off flush with the plastic terminal plug and hacksawed the capacitor cylinder off from the fixing bracket. This was then reinstalled with the fixing screw to secure the through body connector plug to the body of the distributor.

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If I have any problems with the box that needs a quick reversion, I will: add a new condenser to the distributor and reconnect connect the black wires back onto the condenser terminal. Disconnect the orange and black leads from the coil and reconnect the green switched 12v currently connected to the CDI red wire to the coil + terminal. I will then disconnect the black wire at the coil from the CDI box white wire and reconnect to the coil - terminal and I will be back to points. I reckon this would take me about 10 minutes and can be accomplished at the side of a dark road.

From reading posts about this and legitimate MSD ignitions, it appears to be a pot-luck as to whether the grey tacho wire will work directly with our tachos. The tachometer works by sensing the coil flyback voltage pulses when the points are opened. The Ignition provides an 'artificial' square wave output at 12v to simulate the flyback voltage pulses which has an equivalent dwell angle of 86 degrees (or 24% duty cycle as described in the instructions). Variations in the components within individual tachos may be less able to discriminate this input, instead the tacho is looking for the 'ringing' of the coil and so the tacho adaptor is required. My tacho did not work, with it staying resolutely at zero.

After looking for some time on Summit's site I could not find the tacho adapter listed in the instructions. A Google search on the part number took me to a page which said it was unavailable and suggested a Mallory part which looked exactly the same but... also unavailable. The Mallory page then suggested the equivalent MSD part so I emailed Summit technical support who advised me to use the MSD part. These tacho adapters are basically a coil wired with just an equivalent to the primary winding which charges and collapses its field as the points close and open. This will then provide a sufficient back EMF pulse to trigger the tachometer. This basically fits between the switched 12v and ground via the points. They also include a diode which is installed between the white wire and the points to presumably protect the ignition box from this pulse. I drilled two holes and screwed mine to the bulkhead behind the coil where the wiring was easily within reach of the usual cluster of terminals at the coil.

I needed to rearrange the wiring from the original configuration to accommodate. The red wire was connected to the green switched 12v wire and the jumper used to connect the red wire on the ignition box. The white wire from the adapter was cut short after teasing out of its protective sheath, re-terminated and connected to the black wire that was previously connected to the coil - terminal (which was hanging disconnected with the earlier set up). The grey tacho wire from the box was disconnected and insulated with heat shrink and left running parallel with the loom across the top of the bulkhead. The grey wire isn't used with the adapter but I left it in place as it can be used to drive other, rpm dependent equipment.

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The unit includes a rev limiter which is set by adjusting two potentiometers concealed behind rubber plugs next to a diagnostic LED that lights when the points are opened. The rev limiter pots are set, one for the thousands of revs and one for the hundreds by turning with a small screwdriver. I set mine at 6,200 rpm which gives me some safety margin against the factory red line. This can be adjusted up to 9,900 rpm so this gives me a bit of leeway for future modification. The unit needs to be configured for operation with a 4 cylinder, it comes out of the box set for an 8 cylinder engine. There are red and blue loops of wire projecting out of one of the wiring grommets -These are both cut. I insulated mine with heat shrink so they could be spliced and soldered in the future - jusssst in case I ever decide to swap the engine for a 6 or 8 cylinder - it pays to be prepared. :)

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I took the opportunity, when ordering the MSD tacho adapter, to order a Pertronix Flamethrower coil. This maintains a 3 ohm primary resistance which matches the stock Bosch coil and is probably a mild upgrade. I did consider something like an MSD Blaster II coil but this has a low impedance primary that would definitely need a ballast resistor to run with points. This is an added complication for my reversion strategy so I will stick with the blue coil that doesn't need an external resistance as the total voltage, even with a stock coil is likely to be overkill on this engine.

What is the impact? I had not expected it to be too dramatic in terms of performance enhancement but it has certainly crispened up the throttle response and I would swear that it has gained some power at the low to mid range. The unsteady idle has improved a lot. So much so, I am willing to think that the ignition is now 'sorted' and look to fueling for any other improvements. I checked the timing and found that it was slightly advanced from its setting of 36 degrees at 3,000 rpm. I tweaked it back again and had to play with the idle speed a little (though I seem to be having coincidental water choke issues with my Weber 32/36).

Overall I am pretty pleased with the kit. It is very well made, with good instructions and easy to fit. The benefit is noticible, I will be interested to see if I can detect any improvement in MPG. It was a bit disappointing that I needed the tacho adapter as it is a little bit clunky and it required some rework to fit. This seems par for the course though with many people reporting different results, even with the same cars. I can see that this has kicked the purchase of a 123 Tune off over the horizon a bit - at least until I rebuild my engine to seek a little more power. At that point I will be interested in the tune ability of the ignition but having the CDI means I will not have to worry about 'the amount' of spark available.

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Always great to see a new idea.

personally I’ve been on the 123 for a number of years without incident, that is incident related to 123.

 

Good luck with the Summit 

 

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