23-03-2024, 03:24 PM
Hi
I recently had cause to help out a friend troubleshoot the weakener system on his 1970's Rolls Royce. For those unfamiliar, this setup slightly leans off the mixture supplied by the two large SU carbs when cruising, by applying a small negative pressure to the top of the float chambers. It lowers emissions and improves the fuel economy, probably from 10 MPG to 10.5 MPG.
The total setup devised by RR for this one small function comprises a dedicated air filter, an air bleed needle valve, a cutoff solenoid with thermostatic switch, a "fuel receiver" device, a one way drain valve and no less than 11 rubber hoses.
I got the feeling that the RR designers got into a bit of a hole with this design, but kept on digging....
We did find the fault in the end, someone had inadverently swapped over two same-size hoses under the car. All good fun, and satisfying once you have worked out how it's supposed to function. Unlike the earlier cars, the RR workshop manuals assume you already know how the various bits work so it was quite a head scratcher.
I recently had cause to help out a friend troubleshoot the weakener system on his 1970's Rolls Royce. For those unfamiliar, this setup slightly leans off the mixture supplied by the two large SU carbs when cruising, by applying a small negative pressure to the top of the float chambers. It lowers emissions and improves the fuel economy, probably from 10 MPG to 10.5 MPG.
The total setup devised by RR for this one small function comprises a dedicated air filter, an air bleed needle valve, a cutoff solenoid with thermostatic switch, a "fuel receiver" device, a one way drain valve and no less than 11 rubber hoses.
I got the feeling that the RR designers got into a bit of a hole with this design, but kept on digging....
We did find the fault in the end, someone had inadverently swapped over two same-size hoses under the car. All good fun, and satisfying once you have worked out how it's supposed to function. Unlike the earlier cars, the RR workshop manuals assume you already know how the various bits work so it was quite a head scratcher.