| Author |
 Topic  |
|
Bruce Sutherland
United Kingdom
1564 Posts |
 Posted - 01/04/2016 : 12:53:50
|
Shouldn't this topic's postings be in the Technical Forum?  |
 |
|
|
ags
United Kingdom
275 Posts |
Posted - 01/04/2016 : 19:57:56
|
Hi Gordon,
There is no particular secret to the temporary ignition set up I am using. The ignition control box is an Aldon Amethyst one being fed from a locked up Bosch 010 distributor. Before this I had tried the marginally cheaper alternative of an Accuspark Stealth box. The advantage of the Aldon unit is that it can be triggered by a set of points whereas the Accuspark one relies on a Kerr effect transistor for switching. As a result the Aldon set up is rather more resistant to the voltage surges given by my three brush dynamo set up, as it is quoted as able to handle up to 20V. When I first tried the Accuspark unit I had not fully appreciated that the limit of 15V set by the switching transistor was a bit marginal since the dynamo was occasionally going up to 15.5V. Result - an expensive lesson leading to a constant misfire at medium to high revs.
In addition you do need to be very careful with RF suppression and a set of good quality resistance leads (properly connected to their terminals and tested) together with resistor plugs and a by pass capacitor on the 12V lead to the coil are all needed. With these precautions in place I have been misfire free for months now.
Note that whilst these modifications are acceptable to MGCC scrutineers they will fail the more stringent VSCC rules, and this is why my set up is temporary until I get my DK4A set up to my findings (and of course checked out properly on roads and hills!).
More technical ramblings from
Andrew Smith MMM571
PB Abergavenny |
|
|
|
Gordon
United Kingdom
691 Posts |
Posted - 01/04/2016 : 22:54:53
|
Hi Andrew,
Thanks for your detailed and most useful reply. I am familiar with the Amethyst unit and employ this on my 1930 Talbot 14/45 6 cylinder car. I fully agree with your recommendations and have found Magnecore cables to completely suppress RF so I have not needed to employ extra suppressor or resistive plugs. As the original car spec called for a max advance 63 crank degrees, with static set to 1 degree before TDC, this needed a careful redesign of the rotor arm tip to cover the range. Also this range means that the available charge time for the coil is limited at high revs so a coil of suitable inductance must be chosen. I have not fitted a by pass capacitor on the 12v lead to the coil. I think this is a good idea - can you recommend a suitable capacitor please.
I developed a new advance curve on rolling road and the new shape gives 8 to 10% power increase with significantly more torque below 2000 rpm ( 15%) and has transformed the car. It took an hour on the rolling road and gave me back to back power curves so I could see the results and cost less than £100 which I regarded as money well spent.
The car has a dynostarter and and needs the battery to be kept in optimum condition. The dynamo part is equivalent to a 3 brush dynamo so the max current can be set. I have a specially designed electronic voltage regulator fitted in the field circuit. This allows the max voltage to be set for the particular type of battery and controls the charging to exactly what the battery needs depending on it's state of charge. It works a charm - no more boiled or undercharged batteries!
Gordon
ex owner of PB 0331, MG4473
Derby |
|
|
|
ags
United Kingdom
275 Posts |
Posted - 04/04/2016 : 16:37:46
|
Hi Gordon,
There is nothing particularly special about the suppression capacitor for the coil/fixed chassis and dashboard wiring. I worked from a good article "MG MMM Radio Interference" (relating to a J1 by JRE dated Jan.15 - for which very many thanks!). I think that this can be found amongst the Technical Downloads, but should be available via the re-vivified Search function on the Forum. This article indicates a capacity of 100 nF. "Mr Maplin" suggested a number of options so I chose one with a generous maximum voltage rating of more than 300 V. This was still small enough to tuck in away neatly beside the coil. The other thing which I forgot to say earlier is that the Aldon box is installed on the rear side of the firewall so that the bonnet and firewall form a very nearly complete Faraday cage further protecting the box from engine sourced RF interference. This position also allows a very short earth lead (1" - 2") which Aldon told me was a good precaution to stop the earth lead to the box acting as an aerial picking up interference.
More technical ramblings from
Andrew Smith MMM571
PB Abergavenny |
|
|
|
Gordon
United Kingdom
691 Posts |
Posted - 04/04/2016 : 17:19:50
|
Hi Andrew,
Thanks for the information. Maplin here I come! I have my box mounted in is own small box and that box is mounted within a steel earthed and fully enclosed steel tool box for the reasons you state. I also run a short earth!
I note the recommendation of fitting the capacitor next to the coil. Do you see any reason why I shouldn't fit the bypass capacitor at the other end of the positive feed to the coil?
Gordon
ex owner of PB 0331, MG4473
Derby |
|
|
|
Topic |
|
Forum Locked
Topic Locked
