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Post by zonker on Oct 16, 2019 4:17:41 GMT
While perusing thru YouTube, I came across a bloke who took a early 70's Honda 600 2 cyl car and adapted the stock dizzy, a MSD capacitive discharge box, and a late model two tower distributor-less style ignition coil to make 40k volts occur at the plug on his little antique.
I'm wanting to try this on my DAF46. I sourced a mid 90's Mitsubishi Galant (and Land Rover Discovery) two tower ignition coil, a Mark 10 CD ignition box, and a pair of plug wires with the correct terminals for the coil.
Plans are to measure the resistance of the coil and add a ballast resistor that will mimic the requirements of the CD box, then cut the condensor wire and use the points as the trigger for the CD box.
Should make for a smoother running and better performing DAF. Your thoughts on this?
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Post by bobdisk on Oct 16, 2019 5:25:21 GMT
I wouldnt have thought it would work on the Daf (or any engine with a normal HT distributor) A "wasted spark" system fires the plug at every down stroke of the piston. It uses the spark to ignite the mixture on the normal ignition stage of the cycle, but the plug also fires on the exhaust stroke, doing nothing for the power output(hence "wasted" spark). These engines are designed for it, the Daf is not. An example is the NSU Prinz. This has two 6v coils connected in series, one for each cylinder, and one set of points.
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Post by zonker on Oct 16, 2019 7:32:18 GMT
I like the thought of higher voltages which translates to larger spark plug gaps (and a stronger ignition spark). I also think one of the advantages of a wasted spark system is it allows the spark plug to fire when not under compression pressure, lending itself to clear off any spark impediments like oil fouling.
In regards to the DAF, I see only one caveat, and that's the choice of initial spark timing. Setting initial timing at the factory setting of 5 degrees ATDC will most likely cause the wasted spark event to fire when the intake valves are starting to open, meaning unburned fuel in the intake manifold could prematurely reach the firing spark plug. I'm guessing in order to make this work on the DAF, the initial timing will need to be set at some value BTDC, and that means the advance curve will most likely need to reduced, like possibly plugging off the vacuum advance.
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Post by zonker on Oct 17, 2019 6:36:06 GMT
Today the Capacitive Discharge Ignition kit (CDI) arrived and of course I could not wait to install it asap. I mounted it between the battery and the jack and ran the wire harness to the coil along the positive battery cable. It's all hooked up and running and although I have not drove it yet, I had to readjust the idle speed and mixture because it jumped about 50 rpm. I was getting an occasional misfire at idle before but not any more. The motor smoothed out and the timing light flashes consistently (before it would occasionally skip a beat). Next step is the land rover twin tower coil pack and two spark plug wires. Hopefully the parts will arrive before Monday so I can complete the conversion over the weekend. So far parts cost is $70 for the NOS CDI unit, $15 for a Land Rover Coil, $6 for a set of 8 new spark plug wires (hopefully I can find the perfect length out of those), and $25 for 12 spark plugs (3 different heat range sets in both standard and extended tip length). I'm thinking the ideal will be the extended tip plug, one heat range colder than stock, and gapped to .040". Plug P/N's are as follows: NGK Std Tip: B5HS, B6HS, B7HS NGK Extended tip: BP5HS, BP6HS, BP7HS Pics or it didn't happen so...
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Post by zonker on Oct 18, 2019 15:38:59 GMT
OK, next step is done - the mitsubishi waste spark coil is in and working beautifully! No issues regarding timing being after TDC like I was concerned. It has never started in the cold so easy.
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andrew
Likes DAFs
Posts: 1,097
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Post by andrew on Oct 18, 2019 16:33:09 GMT
Intriguing! I wonder what advantages this would give over and above a conventional electronic ignition system? I also think that advancing the timing more than 2 degrees would present problems of pre-ignition and would also mean you'd need to run on 98-99 octane fuel. This IS available in the U.K., but I was under the impression that American petrol (gasoline) has a lower octane rating than this.
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Post by zonker on Oct 19, 2019 1:55:08 GMT
Since I am using points as the trigger and not a magnetic pickup, this could be argued this is not an electronic ignition. I'd call it an electronic ignition though. The points are merely being used as a trigger, and things like gap and dwell settings are really not a big concern. Its a perfect means of maximizing the use of the stock distributor by creating a system that produces a much higher voltage at the plug. And a lot of that extra voltage capacity happens because the ability of the capacitive system to make for a larger dwell event on the coil, and of course the coil's available output.
Using a stock oil filled coil is usually good for up to 20k volts at the plug, modern coils can reach as high as 80k volts. What this means is one can increase the spark plug gap size to force a higher voltage be created in the combustion chamber and that will decrease the odds of a cylinder misfire. One can even run excessively rich, or lean mixtures and the combustion can still occur, as opposed to a misfire on a lower voltage created from a smaller gap or lesser dwell. Also, getting rid of the rotor and cap reduces voltage being lost during the transference of juice from the coil to the plug gap.
As for advance, when I bought the car, the timing was probably set around 5 degrees BTDC and it would ping on regular gas. If I set the timing anywhere from 2 BTDC to 5 ATDC there is no pinging. But initial advance is only part of the story. How loose the advance weight springs are, allowing advance to "kick in" prematurely, or how much vacuum advance is achieved also weigh into the equation.
So far, my car likes a setting of around 0 BTDC, but I have other issues that prevent me from really dialing it in. I need to repair the carburetor, it has a flat spot off idle and I am having to turn out the mixture volume screw out way too much. Probably a clogged passage in the idle air emulsion system of the carb. As soon as the carb gaskets arrive from dafhobby, I'll be addressing that.
As for USA fuel vs UK fuel and octane ratings, us yanks use a different measuring system that gives a lower number. UK uses RON and USA uses RON+MON/2, Our 87 octane regular is about your 92 octane, and our 91 octane premium is around 97 octane in the UK.
Same goes for the gas mileage and capacities - our gallons are larger so our gas tank capacities and fuel economy numbers will read lower.
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