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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).
Performance of standard car sparking plugs and the testing of potential replacements.

Identifier  ExFiles\Box 178\4\  img045
Date  26th April 1932
  
R.{Sir Henry Royce} From TS/lid.{A. J. Lidsey}
c. to SH.
c. to DT.
c. to W H.{Arthur M. Hanbury - Head Complaints}
c. to DA.{Bernard Day - Chassis Design}
c. to V.{VIENNA}

SPARKING PLUGS, CARS.
----------------------

Our present standard plugs for cars are :-

Full Lodge 'C.3' Type (Mica and Porcelain).

B/2S HP. K.L.G. K.1. Type. (Mica Insulation.)

The Lodge 'C.3.' plug replaced the previous 'P' type which was of all porcelain insulated three point type because it is better at high speeds. The 'P' type plug preignites badly after about three minutes full throttle running at high speeds; the C.3 type plug in fact has this disadvantage that it misfires badly on (magneto) only pick up at speeds up to 30 M.P.H. in the full engine. When pre-ignition is used, or on battery ignition only this fault cannot be detected. Recent tests also show that the K.L.G. 'K.1' plug misfires equally as badly on magneto ignition on P.II. as the Lodge 'C.3.' plug.

We have communicated with the plug manufacturers and are continually trying out new type plugs in order to improve our standard. A.C.IV was tried out for this reason with Lodge type C.3 plugs. These however have proved unreliable, 'cuts' on this car and on other tests. When K.L.G. 'F.V.' returns we propose to test out on a set of Lodge 'V' type plugs, which are good on P.II for misfires at low speeds, we rather doubt however whether they will be sufficiently good at high speeds, we expect them to preignite.

The present standard K.L.G. 'K.1' plug is very good for high speed work, but in view of the recent tests on the P.II car it may be found better to cure some of the prevalent low speed misfires on the B/2S HP car, this point will be investigated.

HS{Lord Ernest Hives - Chair}/A.J. Lidsey.
  
  


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