Here are the good reasons , why a advance capsule MUST be connected to PORTED vacuum. If you don't believe, I can send a picture from a professionell "Bosch" book about "motor-management".
If you connect it to one of the 12 "pipes" between carb and inlet valve, you have MAXIMUM vacuum at idle. If you adjust the static ignition to 10 to 12 before TDC and add roundabout 16 degree (at the crank) from the advance capsule, you have roundabout 26 - 28 degreee ignition before TDC at iddle. At this amount of pre-ignition the motos has many "non-igniotions" at idle (the piston is too much before TDC and the compression of the small "gas-cloud" at iddle is too small, to ignite the micture in 100% of all revs), is shaking, and you have a very bad smell out of the exhaus because of unburned hydrocarbons. I have measured this all with a 4-gas tester. 2000 ppm of HC is too MUCH.
If you do like this, you have to turn the distributor back to roundabout 0 to 4 degree before TDC, that the motor is running "well". But if you do like this, you have much too less preignition at full throttle and the motor is a litle bit too lazy at full throttle. Maybe you don't feel this lack of punch on a english road. On a german highway you can feel it very easy beyond 120 mph. You press the pedl . . . . and the "rabbits" are still passing.
I have bought my EV12 in 2001. The owner has mounted a advance capsule und connected to the drilling at the LHR carb below (full vacuum at iddle). I fiddled 2 years with problems, spoke to some garage idiots, which know nothing about this problems, red some books and started thinking and investigation about ignition.
1. Every gas motor is running best, if the motor has a advance of roundabout some (3 - 12 degree before tdc) degrees at idle, a lot of degrees before tdc at part throttle and less degree before tdc at full throttle.
2. The motor delievers more horsepower at part throttle / or needs less gas for the same amount of delievred power, if the time of ignition is lets say at 3500 rpm and 20% cylinder filling (part throttle), earlier than of the same rpm and full throttle, because a lower cylinder filling has a lower pressure nearby TDC and is burning slower. Power is max, if the point of highest pressure of the exploding gases is roundabout 6 - 10 degree after TDC. If a small filling is burning longer, it must be ignited earlier.
How can a simple (analoge) ignition system realise this demanded "curves" ?
4. For the V12 and the XK-motor roundbaout 10 degree at idle are good for a stable idle. Therefore set static ignition on 10 degree before tdc.
4. For the maximum early ignition without pinking and detonation at full throttle the advance curve is "formed" by the advance system with the wights. The higher the revs, the more early the ignition. If the burning-time of a full load is the same, the ignition-timie must be more early at high revs, that the point of highestprssure in the cylinder is allways roundabout 6 - 10 degrees after TDC.
5. If the timing shall be earlier at part throttle, "pre-time" has to be "added" by a separate system, depending on the load. The amount of load you can measure by the amount of vacuum /pressure below normal pressure between the "air-door" in the carb and the valves of the motor.
6. The amount of added pre-ignition shall be low at idle. Therefore you need a construction which gives no vaccum to the advance capsule at idle. If the capsule is connected to a port 2 - 4 mm BEFORE the butterfly, the vacuum at iddle is low. The capsule need a minimum vacuum to start to work. Therefore zero added-pretime at idel. Works well.
7. If the butterfly of the carb is wide open, the amount if vacuum at this port is again low. No added advance timing at wot. The piont of ignition is maaged by the advance system of the wights. Works well.
8. At part throttle, the 1 mm thick "end" of the butterfly in the car is nearby the port, the cleft between the butterfly and the wall of the cabr is small, the gas speed is high and therefore the vacuum is high. With low load, slow burning of the mixture in the combustion chamber, a lot of pre-ignition is needed. The vacuum advance-system generates max vacuum, the capsule generates max advance. The motor works well.
I have done this at my car. I had to drill this port into my carb. After some fiddling with the drilling ending at the wrong positon , closing the drilling and drilling again, the motor runs very well.
The result of the added vacuum-advance system is, that the motor takes less gas at 90 of its running time. Maybe 5 % less gas consumption. I have not exactly measure before and after.
The original retard-system of the EV12 was just to run hotter / less colder in the minutes after starting, that the gas-poisons (HC and CO) in the burned gases are lower. The motor runs hotter and therefore becomes hotter more quick. If the cylinder load is ignited later, the gases are staying hotter when leaving the cylinder. The energy is not transformed into working power. The energy remains as heat in the gas.
If you have understood all, drill this hole into the LHR carb and connect a rubber hose to the advance-capsule.
I have done this all. The cars runs very well. Because of the information from the internet and my books I am shure, that the "stuff", what I have written her, is 95% correct.
I have mounted to my advance capsule a hand-pressure for vacuum. I drove 70 mph in steady state and gave vacuum to the capsule by hand. Then I opened a valve at the hand-pressure, that the vacuum fall to zero suddenly. I felt very clear a slightly beaking of the car and a speed which was 2 - 3 km lower. This shows me, that the power of a certain amount of gas-air mixture burned earlier at small part throttle is producing a little bit more power / torque than burned roundabout 16 (depending of the type of capsule) degree later without the vacuum-advance system. The diffence in gas consumption is not big. But in 16 years with 5 - 6000 miles every year it is becomming a nice amount, worth the money and work I have spent to mount the correct vacuum-advance system.
http://georgiajag.com/Documents/Vacuum% ... Retard.htm
Excuse my simple english.
Regards Wolfgang Gatza
