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).
Tests on power loss caused by various components of the exhaust system.
| Identifier | WestWitteringFiles\O\2April1926-June1926\ Scan080 | |
| Date | 1st May 1926 guessed | |
| contd :- -4- POWER LOSS DUE TO VARIOUS PARTS OF THE EXHAUST SYSTEM. A series of tests were undertaken to determine the power absorbed by the various components of the exhaust system and to see if there was any possibility of lessening these without loss of silence. The tests shew us that the part taking the most power is the exhaust manifold itself which accounts for a max. of seven horse power out of the total loss of twelve at 2750 r.p.m. At 3000 r.p.m. it would be even greater but we have not taken the complete silencer curve to this speed. We determined the loss due to the hot spot but this was not appreciable amounting to about one horse power. The high manifold loss seems quite unnecessary and it would appear to be more efficient to absorb this power in the exhaust box if found to be necessary from the point of view of silence because here a greater pressure drop could be obtained without such a degree of back pressure. An experimental manifold was constructed and tried (see print) and the resulting power loss due to this part relative to free exhaust was only about 2 HP. See curves. This manifold was arranged so that the pipes from each port had a better lead in to the down pipe than obtained with standard. The final down pipe was 2" dia. The reason we think why the std. manifold gives greater loss than the experimental one is due to the opposing flow of gas from the two end ports of the engine. The dia. of the horizontal branches being small the gases would contd :- | ||