TR7 Fan Posted June 23, 2019 Share Posted June 23, 2019 Hello, I installed a Lumenition optronic ignition system. Situation is: Lumenition optronic High tension lead from distributor to ignition coil: “High temp. double silicone”, measured resistance: 11,5 Kohm. High tension leads from distributor to plugs: “Lucas silicone speed lead”, measured resistance:: 6 to 8 Kohm. Ignition coil: Bosch 0221 119 030 Ignition coil connected via “eureka wire” from the car. Eureka wire resistance:1,9 ohm / Bosch primary resistance: 1,4 ohm. Total resistance:3,3 ohm. Spark plugs: NGK BP5ES Engine to be fitted with K&N air filters; Carb jets: BAL; Inlet and exhaust ports: slightly polished; Tubular exhaust system. Voltage at primary side of ignition coil when ignition switch is “ON”: about 5,7 volt (engine not running), battery voltage 12,2 volt. When trying to tune the carbs, the coil is getting hot , I measured about 50 degrees (Celsius) after some 20 minutes running. I can barely hold my hand against it. The engine is running well stationary. What temperature should a coil have ? Regards, Luc. Quote Link to comment Share on other sites More sharing options...
glang Posted June 24, 2019 Share Posted June 24, 2019 You can also measure coil secondary resistance from HT connection to the case and it should be between 5 and 20k ohms. Also check what the supply voltage to the coil is with the engine running as I don't expect it to still be 5.7 volts but it certainly shouldn't be battery voltage. In the end though I don't think that temperature is excessive as there's quite a bit of current passing through the coil and it generates heat which is normally dissipated by airflow when driving.... Quote Link to comment Share on other sites More sharing options...
RobPearce Posted June 24, 2019 Share Posted June 24, 2019 As glang says, I think you're probably OK. Twenty minutes with no airflow is enough to get the coil up to its ultimate running temperature. If the EI box were a clever one with dwell control then the coil would run cooler at idle, but I'm pretty sure Lumenition is a crude type, so the coil gets even hotter at idle than in normal driving. And 50 degrees is not hot - the coil is expected to tolerate a lot more than that. The six cylinder cars had it bolted to the engine block! Quote Link to comment Share on other sites More sharing options...
TR7 Fan Posted June 24, 2019 Author Share Posted June 24, 2019 Thanks for the replies. So I don't have to worry, maybe just when I am in a traffic jam with hot weather. Forgot to mention: Secundary coil resistance is about 12,7 Kohm, supply voltage to coil when running: about 9 volt. Regards, Luc. Quote Link to comment Share on other sites More sharing options...
Howard Posted June 24, 2019 Share Posted June 24, 2019 The ballast resistor inside the wiring loom was designed to reduce the coil voltage to 6v according to the information I have read. Since energy is proportional to voltage squared this would result in the energy dissipated increasing from 6x6x1.4=50 watts to 9x9x1.4=113 watts so it will get a lot hotter. Quote Link to comment Share on other sites More sharing options...
glang Posted June 24, 2019 Share Posted June 24, 2019 Think its difficult to measure the coil supply voltage running as the coil is charging and discharging rapidly to produce sparks but all these figures sound reasonable🙂 Quote Link to comment Share on other sites More sharing options...
RobPearce Posted June 24, 2019 Share Posted June 24, 2019 The whole "reduce to 6V" thing is an unhelpful over-simplification. Luc has measured the engine stopped coil voltage at 5.7V, which is as near as dammit 6V. So it's correct. Any other time you measure it you'll get more than 6V because, while the points are open, the coil is not grounded and there's no potential divider to give you 6V, so you have 12V there. In fact, Howard's result is backwards. When the engine is stationary, and the points closed, Luc is getting 6V, so 50W. With the engine idling, meter reading 9V, it's actually only 25W in the coil. Why? Because (to a first approximation) the 9V reading means the dwell is roughly 50%, so the coil is seeing 6V for half the time and nothing for the other half. Quote Link to comment Share on other sites More sharing options...
TR7 Fan Posted June 28 Author Share Posted June 28 (edited) Hello again to everyone, I took the car for a drive this week for a long drive in the hot summer weather. Drove about 50 kilometers on the highway at about 95 km/hour, no problem. When I got to the local roads, the problems began: The car nearly stalled at the stop lights, I had to get the revs up with the throttle pedal. Driving at 2000 rpm and accelerating, the car hesitated badly and was shaking badly. I had to go to a lower gear to get it going decently again. Getting back on the highway, the car ran normal again at 95 km/hour. The last part of local roads to my home the problems came back. Could this be a faulty coil or lumenition module? Regards, Luc. Edited June 28 by TR7 Fan Quote Link to comment Share on other sites More sharing options...
glang Posted June 28 Share Posted June 28 Wow could be a few things! Difficult to see it being coil or ignition module unless its temperature related ie runs cooler when going faster so problem goes away. Can you get the car hot and then repeat the problem while stationary? Quote Link to comment Share on other sites More sharing options...
65redspit Posted June 28 Share Posted June 28 this may sound basic and patronising (if it does i apologise) but is it the right coil for the system? i burned out a coil that wasn't recharging fast enough for the upgrades i had made to an engine once?? also there have been a whole batches of coils failing out there because the manufacturers quality control seems to have slipped Quote Link to comment Share on other sites More sharing options...
65redspit Posted June 28 Share Posted June 28 also, have you checked the plugs themselves? Quote Link to comment Share on other sites More sharing options...
TR7 Fan Posted June 28 Author Share Posted June 28 I ran the car stationary for a long time and the problem came back. Sometimes hesitating badly when accelerating, sometimes the engine stalled. I could always immediatly start the engine again and it ran stationary without any problem. I had chequed the spark plugs whem I got home after the long ride, they were ok (I mean lihgt brown color). The Bosch coil measured 1,4 ohms when cold and 1,8 ohms when hot. I connected an old Unipart coil GCL111 instead of the Bosch coil and ran the car stationary for a long time. The engine seemed to run normal now (maybe it didn't run long enough). I will take the car for another drive with the Unipart coil connected. I will give an update after the ride. Regards, Luc. 1 Quote Link to comment Share on other sites More sharing options...
glang Posted June 28 Share Posted June 28 Does seem to be temperature related so could also be the electronic ignition - is it all installed in the distributor and could you go back to points to discount it as the problem? Quote Link to comment Share on other sites More sharing options...
Matt306 Posted June 28 Share Posted June 28 (edited) Have you checked fuel isn't overheating the . The four branch manifold creates a lot more heat than you think . Turn the lights off in the garage when dark and rev it watch the exhaust manifold. There's a reason there are louvres in that bonnet. What's the water temp at. Have you checked the oil cap for white sludge. You should be a 12v ballasted coil . Edited June 28 by Matt306 Quote Link to comment Share on other sites More sharing options...
TR7 Fan Posted July 1 Author Share Posted July 1 Update: First some answers: Water temp is ok, gage goes to the first mark, not higher. No white sludge on the oil cap. I had a 35 km drive today in sunny weather but not as hot as last time. I had the Unipart coil mounted and the lumenition module mounted a bit further away from the coil. At first it was almost near the coil. I ran it stationary for a long time, no problem. I went on local roads, then highway and then again local roads, car is behaving good. When back in the garage, I immediately touched the coil and the module. The coil was hot, but not as hot as the Bosch coil. The module was significantly cooler than with the Bosch coil. I think installing it further away from the coil was good for the coil and the module. Question is: is the Bosch coil stil good or not? I suppose I will have to get the car out on a real hot day to know if the problem is really solved. Regards, Luc. Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted July 1 Share Posted July 1 Is it something to do with ballast resistor should you car have a ballast resisted coil or not Quote Link to comment Share on other sites More sharing options...
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