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).
Comparison of Peregrine and Alfa Romeo engine power outputs, including details on blower performance and component failures.
| Identifier | ExFiles\Box 1\8\ B001_X100 Engine Chassis-page206 | |
| Date | 19th July 1932 | |
| R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Rs.{Sir Henry Royce's Secretary} c. Sg.{Arthur F. Sidgreaves - MD} WDr. c. K.{Mr Kilner} Da.{Bernard Day - Chassis Design} c. HY.{Tom Haldenby - Plant Engineer} X407-7a Hs{Lord Ernest Hives - Chair}/Rs.{Sir Henry Royce's Secretary}2/MA.19.7.32. x4482. PEREGRINE AND ALFA ROMEO. ======================== We have drawn a curve Rs.{Sir Henry Royce's Secretary}Fr.20 comparing the Peregrine and Alfa Romeo power outputs. Actually Peregrine is running with a slightly higher compression ratio and boost pressure but the Alfa Romeo has a 20% larger inlet valve/litre, 13 more degrees of inlet valve opening and a 25°C lower boost temp so that roughly the advantages cancel out. It will be observed that we actually get about 4% more power per cc displacement with Our push rod valve engine than the Alfa does with its over-head camshaft unit even though we have done no development on the best timing for supercharged work etc. We have not got reliable figures for boost temperatures yet but it seems that with the blower we are using (1850 cc) these will exceed 80°C. The Blower is designed to boost at 10 lbs/sq.in. - 15 lbs/sq.in. rather than at the 7½ lbs we are using and is therefore probably 5- 10% less efficient than the Roots under the same conditions, i.e. the Power Plus compresses the mixture to say 12 lbs/sq.in. internally and then lets it down to 7½ lbs/sq.in. into the induction pipe which is ineff-icient. Even so it would seem that with the blower close the induction pipe we may want some sort of inter-cooler, especially with the larger blower we are going to fit. We have burnt through two more gaskets, one steel asbestos and one copper asbestos which indicates that a solid metal gasket will probably be necessary for these boosts. We have been running 14 M.M. plugs at the 147 M.E.P's obtained and they have shewn no signs of pre-ignition. | ||