Engine Results after RVS treatment

After the RVS-Tech petrol engine G6 treatment the lowest cylinder Compression Ratio (CR) increased from 8.5kg to 9.6kg with the highest at 10.65kg, before 10.3kg. With the engine CR norm 9.25:1 this seems impressive. Not only the CR went up also the hydraulic valve lifters was much more quiet.

Without doing any adjustment of the two SU HIF Carburetors during the RVS treatment, the spark plugs went blacker and the AFR meter indicated a more rich mixture, down to 12.2. This could be explained by the cylinders are sucking more air and fuel with the same cab setting.

After the second part of the RVS treatment the carburetors was adjusted to run the engine as lean as possible.


This came out to be approx AFR 15.3:1 for good drivability. With the new setting the picture shows all spark plug color.  They are now reasonable the same color and all are light grey. The picture shows right and left side of the engine block with the right from front is no 1. Numbers are ignition timing.

The fuel consumption after this lean setting came out increasing from approx 6-7km/l up to 8.8km/l  (24.8mpg – uk) on a long trip, also very impressive.

Adjusting the SU HIF6 Carburetors

The SU HIF6 Variable Venturi carburetors only have one adjustment screw, see picture. This takes from idle and gives the mixture over the full load and RPM range.

To adjust two carburetors with only one wide-band lambda probe, one is set lean (screw out) until the engine runs unstable. Not the setting and set more rich (crew in). Do the same with the other cab and note the setting.  Then set both to this point and give ½ turn more rich (in) and check the AFR Meter. If too lean give both ½ turn more rich (screw in). Do so until the idle is approx 14:1 and check during drive condition that this doesn’t get leaner than 15.5:1. If so readjust both equal to more rich.