Home Rover SD1 Twin Plenum Vitesse Julian Rogers Home

The trigger wheel sensor (above) needs to be adjusted round the circumference of the wheel so that the Megajolt knows where top dead centre on cylinder 1 is.  It also needs to move in and out so that it can be the correct distance away from the teeth. Too far and some teeth will be missed, too near and the sensor may hit the teeth.

Water pump

The controller for the Davies-Craig electric water pump is fitted to a chassis made from sheet aluminium and Tufnol. These components are fitted inside the driver’s side glove box out of sight.

The controller is connected to a temperature sensor which is fitted into the radiator top hose adapter on the inlet manifold. The thermostat is removed. The controller pulses the pump or runs it continuously at an adjustable speed as the computer in the controller judges is required by the engine.

The pump itself is fitted in the bottom radiator hose under the alternator where it can’t easily be seen from above.

The old mechanical pump is retained with the viscous coupled cooling fan. However, I have removed the impeller as shown on the right to allow the flow of coolant to be controlled by the electric pump.

Electrical connections

I like to power new components via a fuse unit fed with a heavy cable direct from the battery. That way I don’t run the risk of overloading existing circuits or pick up voltage drops from dodgy existing connections. Also I can fit fuses to suit the new circuits and give them better protection. A car is a pretty electrically noisy environment and supplying direct from the battery minimises noise which might affect electronics. It is just as important to provide low resistance earth points. These should be bolts to the car’s metal work sized to suit the current to be passed. Clean off the paint to the metal and protect with Vasaline or similar.

Take heavy loads direct to earth. Don’t tap into this earth lead in order to earth other circuits or daisy chain earth connections. Take each earth connection separately to an earth point to avoid interference between circuits which could upset electronics.

This provides provides for always on circuits. For circuits which need to be on with ignition, I provide a relay activated by any handy existing ignition circuit.

Engine mods

Davies-Craig pump controller

Megajolt unit

Coil packs

EDIS 8 unit


Electric water pump, fan belt tensioner & Megajolt ignition

Megajolt ignition

More on the Megajolt system here

More Twin Plenum here

Gallery of Rover SD1 Vitesse Twin Plenum Pictures

Fan belt tensioner

For some time now I have been having trouble getting the fan belt tight enough to prevent it slipping and screeching when the alternator is heavily charging. (Perhaps I am really getting weak with age!) Once the belt has slipped for a bit it quickly overheats and hardens and that makes things worse and so on until it has no grip at all. One helpful thing is to make sure there is no rust on the pulley surfaces but other than that it is a question of getting the belt tight enough. With the Megajolt coil packs fitted to the alternator support re-tightening the belt is not possible without removing the packs which is a pain

I was having a clear out in the workshop and found an unused cam belt tensioner from, I think, a Hyundai Getz which we used to own and this looked like it could be fitted with a bit of jiggery pokery.


Tensioner mounting plate


Original coilpack bracket

Assembled unit

As fitted