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).
Comparing the Packard straight-eight engine to another manufacturer's engine, discussing smoothness, carburation, and engine balance.
| Identifier | ExFiles\Box 127\1\ scan0131 | |
| Date | 11th November 1926 | |
| -2- 5. At low engine speeds full throttle the Packard engine is certainly smoother than ours, possibly because of the better overlap of the strokes. But this is not necessarily the reason, because - (a) The car is lower geared, (b) The carburetion on the Packard and other American cars at low speeds seems to be more regular than ours. The Packard in this respect is scarcely as good as the Jordan or Hup. eights etc. which use carburetters without an extra air valve (such as the latest Stromberg) and give a beautifully regular and dependable low speed performance (probably at the expense of very rich mixture). Possibly the size (etc.) of the manifold is responsible. 6. There is a theoretical out of balance in the straight eight which is nearly 100 times as large as the six. At 2000 revs. and with proportions of the Silver Ghost engine, the out of balance of an eight reaches 31 lbs. maximum at a frequency of 4 times engine speed, whereas the six reaches .36 lbs. maximum at 6 times engine speed. Since one ounce error in a piston will give about 21 lbs. max. unbalance force at the same speed, the straight eight error does not seem to be of any importance. But it occurs at firing frequency, and might cause humming and buzzing in the car which would be attributed to exhaust noise. The latest Packard eight is a very excellent car in many ways. Why do you not get one at Derby and give it a good trial? Mr. Beaver tells me that we have several opportunities every year to sell you a very good used Packard 8 of recent model at a price of about $2500. Yours very truly, Maurice Olly MO/E | ||