Whats in the rev limiter? How does it limit revs?

[amarshall]

Maybe the OE limiter wasn't allowing a full spark?

AFAIK that's certainly possible. As components age and corrosion builds up you can get weird effects which result in odd paths to earth - or maybe just disturbing the contacts on the coils has reduced some resistance there.

[KevW]

During winter my car developed an intermittent misfire at around 2000rpm under acceleration. To cut a long story short the misfire became more frequent and I was able to trace it to the Omex rev limiter. When I disconnected it the misfire went away and when I connected it back up the misfire immediately returned.

Thinking there must be a fault with the unit I contacted the manufacturer by email. The reply I received was;

"The limiter works by counting spark events to calculate engine speed. A common problem is a failing ignition lead which has a break, the high voltage will jump this break and create another spark (it is small enough to not cause a misfire in normal cases). The limiter will pick up on this extra spark, momentarily calculating a higher engine speed and cut the spark.

Before we have it back here for testing I recommend you check the leads/plugs/coil etc"

My HT leads were several years old so today I fitted a new OE set supplied by SJ Sportscars and, lo and behold!, the rev limiter is working properly again. I thought this was worth mentioning in case anyone else has a problem with their Omex limiter.

I incorporated my test run into the run out for the weekly shop and was again reminded what great cars to drive Excels are. OK, on a sunny spring afternoon most classic cars feel good but I'm always struck how an Excel seems to appreciate being given some welly on the open road.

[AndyC]

That's a good one to know, and hopefully means you can carry on using it at the moment for the essential travel (essential doesn't have to be mundane vehicle).

[Johnwindwood]

Following advice from here, we disconnected our limiter two years ago and fitted an Omex. It lasted six months before making the car misfire. In our case all ignition parts were new so we knew it wasn't the car at fault. We sent it back under warranty and they refunded as it tested faulty. We now run without a limiter. Carefully.

[KevW]

Well I admit I was sceptical when I received the e mail suggesting the fault my not be with the Omex rev limiter but I didn't mind replacing the HT leads as they were the ones that came with my car when I bought it. I was pleased and surprised when that did the trick.

As I have commuting insurance I'm going to use the Excel for my 6 mile trip to work which means it will be getting tested.

It's sod's law - if I'd not bothered replacing the original limiter which, when I reconnected it, still appears to be working properly I would never have had any hassle. I'm reminded of the words of our US chums "If it ain't broke, don't fix it".

Update 1st December, engine still running well with the Omex fitted.