From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Causes and potential remedies for ignition missing fire at slow speed.
| Identifier | ExFiles\Box 37\1\ scan 206 | |
| Date | 16th April 1932 | |
| HS{Lord Ernest Hives - Chair}/WST. E.{Mr Elliott - Chief Engineer}) FROM R.{Sir Henry Royce} X3199 BY.{R.W. Bailey - Chief Engineer} DA.{Bernard Day - Chassis Design}} (At Le CanadelHenry Royce's French residence.) C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} PN.{Mr Northey} R1/W4.4.32. 2 Sent from WW. 16.4.32 X.3199 CAR BATTERY IGNITION. The missing fire at slow speed must be cured, by firstly finding the cause, when we can generally find a remedy. I have repeatedly pointed out that it occurs only at slow speed on opening the throttle more or less fully. (1) I am told that it is no over richness by the autovac Is this so? It could be proved by use of air pump or petrol pump - i.e. it ought not to be on P. 2., which may have this fault if we do not use the magneto. (2) I have thought that it was wide gaps - i.e. over .025" (which I consider too great for the higher compressions we now use), plus the unavoidable oxidisation raising the required potential above the sparking distance over the insulation, or from the HT. rotor tail to the cylinder that it should have passed. (3) I now add another suggestion with the hope of finding the real cause. This is: When the coil gets hot does it give the same length of spark, because we know that the bakelite case is imperfect when hot, and for some time we used "Stabilite". To test if this is so we can try a coil with a Stabilite case, and also one of the new coils with the primary outsid We must not leave this job until a satisfactory explanation and cure is found. (a) I object to your extra turns without a reason. (b) I never expected my shorter gap to explain the cause or to be a cure, and am well aware of the less perfect idling with .020", than with EP{G. Eric Platford - Chief Quality Engineer}'s old distance of .030", but I consider that for reliable running we cannot at present go over the .020", so long recommended by Bosch. Our new distributor is far better insulated for surface distance than any of our competitors I believe. We cannot believe it is our low tension contact maker: I have seen this, and think it in perfect condition. R.{Sir Henry Royce} | ||