Been doing a little work on my S4/Sprint and took it out for an ‘Italian tune-up’. As I’m generally a fairly sedate driver these days this was the first time that I’ve given it really serious welly in second and third, keeping a close eye on the tacho all the while, ready to change up at the red line.
No chance! Each time the needle got to 5600/5700 revs a terminal misfire ensued and acceleration ceased - just like running up against a rev-limiter in fact, hence my question.
It runs fine all the way from tickover to 5600/5700 and does so again when I drop below those numbers. What’s going on chaps? My initial thought was points bounce (I’ve fitted a Sparkrite electronic ignition which, you may recall, retains the points for spark timing but only passes a small current through them) but, overall, I think that’s unlikely at such a relatively low engine speed. All thoughts, suggestions, remedies eagerly awaited.
They are fairly crude, consisting of a sprung cut-out on the rotor arm of the distributor, which cuts the ignition as centrifugal force acts against the tension of the spring as revs increase.
It should be fairly obvious if your Elan is fitted with one, simply by removing the distributor cap and examining the rotor arm.
If you prefer not to have the rev limiter (or is it is acting too early due to a slightly weak spring, as sounds like might be the case for your car), then simply replace the rotor arm with a non-limiter version, or fix the centrifugal weight on the rotor arm with a dab of epoxy adhesive.
Obviously, the above applies to standard ignition systems. I don’t doubt that there are many cars out there with aftermarket electonic rev. limiters, working in conjunction with electronic ignition systems (eg. Lumenition).
Thanks for such a quick and considered response Martin. Well, well, well - so primitive rev-limiters were fitted, were they? That would certainly tie in with the symptoms that I encountered. I checked with the manual but there’s no indication there of a rev-limiter, which was why I assumed that there must be an electrical malfunction - I’m not really on nodding terms with the Elan dizzy, secreted, as it is, in the bowels of the engine compartment - which was the main reason for fitting the Sparkrite as soon as I bought the car (it was a brand new unit that I’d had sitting in my garage for 20 odd years, having run one on a Rover P6 for 25 years with 100% success and satisfaction - literally ‘fit-and-forget’).
I’ll haul the rotor arm out tomorrow and have a butchers - replacement with a non-limited version being my chosen course if your theory proves correct.
As for the original limiter, they are easy to adjust by carefully bending out the tab a touch, then going for a drive, adjusting out or in depending on cut out RPM? worked for me. Then you still have a limiter to 6500-7000…?
Thanks, Alasdair - I’m now attempting the adjustment you suggest. Er, what tab are we talking about here? I have the rotor arm in front of me and I’ve identified the sprung semi-circular gizmo that, apparently, breaks contact with the brass pick-up lobe when centrifugal force gets to a certain point but can’t see anything that suggests adjustability.
Opposite the pick-up lobe is a fairly hefty brass ‘hoop’ with a central tab or arm sticking up; I guess this lump of metal is a sort of counterbalance to the brass pick-up gubbins on the other side - is that right? Is the sticking up tab a stop for the flung-out sprung gizmo and if so, why is it needed as, presumably the springs stop the thing from moving too far anyway?
Sorry to appear so dense but there’s a reason for that - I am!
Good point, steveb 1. However, I’m reasonably confident that the tacho’s reading about right, judging against the relative positions of the speedo and tacho needles in top gear driving, where the tacho needle sits marginally lower on its dial than the speedo one does on its dial (if you see what I mean). Does that sound about right?
It has been a while since I looked at or even did this, but the tab you describe is the one that I carefully bend, making the spring work harder before contact.