Morris Minor Owners Club

Im thinking of fitting a rev limiter, and I was thinking that a basic one cannot be that complicated, does anyone have a circuit diagram of one that just cuts the ignition coil power supply until the revs fall back below the limit (maybe set by an adjustable resistor?) I have the knowledge to make one from a circuit diagram but not quite sure of the circuit myself...

Picky

Something like this helpful Picky?



It's from an EFI engine but easily modified. I'll try and find the simpler one on my discs in the morning,

i suppose that would work but how would I obtain an "engine governor assembly?" I am sure that one could work by listening to the voltage fluctuations at the ignition coil in the same way the electronic rev counters work. i will look at the diagram again tomorrow with a little more enthusiasm!

Picky

Just found [url=http://cp_www.tripod.com/rotary/pg13.htm]this[/url] on google if it's of any help. I'll have a proper dig through my bike discs tomorrow as I know I have a simple circuit for use on fireblades somewhere.

thanks lee, that looks like it is a well thought out circuit.

I'm fairy new in the Morris world, but why do you want a rev limiter on a Morris ? Or do you have a big engine in it ?

Supercharger ;)

good question.

most engines are self limiting, in that at high rpm they get into breathing difficulties and the revs dont increase. I am building a supercharged engine and with a supercharger or turbo the engine will spin faster and faster until something breaks, which is a scenario I want to avoid!!

Ok, well that's a good reason
Do you supercharge an A-engine ??

The whole point of a supercharger is to have excellent torque throughout the low and medium rev range - you don't want to be revving it !! Early rev limiters (fitted to Lotus Cortina etc) were simply a sliding contact on a special rotor arm which pulled the arm tip backwards as the revs increased until the thing started to misfire thus limiting the revs. Cheap and simple. They could be fitted to Mini dizzy - I'm sure they must still be around !

i am fitting an mg midget 1275cc A series engine, which is basically a morris minor engine but a slightly larger capacity, and the engine bearings etc are slightly bigger so the engine can cope with more power. I am using the eaton m45 supercharger from the new bmw minis, i am going to upload a few photos of my progress at some point.

bmc the supercharger is easily damaged if it is over revved, hence the rev limiter to prevent revving it to high if i miss a gear or something.[/url]

I doubt it's that easily damaged - great bit of kit the Eaton s/charger.

well i want the peace of mind if a rev limiter. I have seen the clever rotor arms on a vw distributor, but I dont think they would be adjustable? my main problem at the moment is trying to attach a manifold to the inlet of the supercharger, it is a really stupid shape

Yes - that's why the likes of V-Max Scart charge so much for the kit! The rotor arm could be adjusted by 'stretching' the spring slightly. But from memory they tripped at 6000 anyway - which should be ok for you.

picky wrote:bmc the supercharger is easily damaged if it is over revved, hence the rev limiter to prevent revving it to high if i miss a gear or something.

A mechanical or electronic limiter won't stop an over rev from sticking it in the wrong gear, and both will prevent an over rev from flooring the loud pedal out of gear.