A VACUUM SILENCER.

New Zealand Herald, Volume LX, Issue 18577, 8 December 1923, Page 12 (Supplement)

A VACUUM SILENCER.

The test of a new vacuum silencer is described by a writer in an exchange. It was made on al2 h.p. car. "The exhaust gases leave the engine by a straight pipe to the exhaust box, where they are split up along two ways, and the two streams are brought together again in such a manner" as to set up a vacuum. This vacuum draw?, off the exploded mixture from the cylinder heads, relieving the engine of the task of evacuating them, and the theory is that the power hitherto absorbed by this work now goes into the transmission The device gives an increased mileage, th-»re is much more power, and there is quicker acceleration. The petrol consumption has not been taken with mathematical accuracy, but the average increase will be some five or six miles a gallon. The increase in power is marked; there is better hill climbing and more top gear work, whether the cylinders are cleaner because of better scavenging I do not know as I have not taken down the engine, and in any case a much longer mileage will have to be done before that point could be tested. These are positive gains. On the other hand the exhaust is a little louder, the gases being expelled with a sharp, crisp but riot noisy crackle. At easy touring speedsbetween twentyfive and thirty miles an hour—the engine is felt arid heard more, but the vibrations are not crankshaft vibrations. At higher speeds the machine runs very quiotlv: during one sharp burst at forty-five miles an hour it was apparently silent, so far as one could hear from the driver's seal, save for the purring of the tyres on the IS The device ' 8 certainly a success, that, factor of the better scavenging of the cylinders bring left undetermined."