123 ignition - is there a rev limiter?

kpytoi1 · Post by **kpytoi1** » Fri Dec 21, 2012 5:30 pm

Has anyone ever experienced what feels like a rev-limiter on a 123 ignition distributor? The unit when installed functions as it should, until the car approaches 3900-4000 rpm, when it starts to buckle and stutter, and feels very much like there's a rev limiter kicking in. The issue is not progressive, as in, it does not get worse as the tachometer climbs, but activates rather abruptly right around 4k rpm. It does this while in park, revving the engine and equally so when under load. Everything else checks out fine, and was confirmed so by a mechanic who insisted that the distributor is to blame. Nothing in the included paperwork for the 123Ignition mentions a rev limiter, and I have never read/heard of this on this and other forums - its a JAG specific model, currently set on curve 0, on 4.2 '68.
Thank you for any advise and suggestions.

Post by **Heuer** » Fri Dec 21, 2012 6:05 pm

No rev limiter on the 123 as far as I know. Sounds like an ignition timing problem so try a different curve or replace the 123 with a standard dizzy to see if it clears.

PeterCrespin · Post by **PeterCrespin** » Sat Dec 22, 2012 1:25 am

Agree. The engine is hitting a timing wall and refusing to rev out. The 123 curves are fairly aggressive IMHO so you need to strobe time at full advance, because you can damage the engine bumping into excess advance.

kpytoi1 · Post by **kpytoi1** » Mon Dec 24, 2012 3:08 am

Thank you for all the advice, here's what happened to anyone interested or anyone who may experience this in the future: As suggested, I replaced the 123 with the old mechanical distributor, and although it did not run as well, it did rev past 4000. That cleared up some other potential culprits, and I re-installed the 123ignition on a different curve. Instead of the default curve 0 I selected curve 4. I idled seemingly better, and revved to 5000 while in park as well as on the road.

Vegard · Post by **Vegard** » Fri Sep 06, 2013 9:31 am

I'm experiencing this stutter and coughing as well.
Now I cannot remember the suggested setting on this car. (Twin stromberg, low comp), but I'll check out setting 4.

Also, I know the car is a bit rich in the lower rev range, possibly middle..

AussieEtype · Post by **AussieEtype** » Sat Sep 07, 2013 10:35 am

I have a 2 cylinder Haflinger with the 123 ignition and it suffers the same issue. The Haflinger has a governor that kicks in at 4800 rpm - my car does not have the governor but with the 123 revs die at 4500rpm where it feels strangled.

The 123 ignition is a great system with its 14 maps but it is a shame that one of those positions is not reserved for the user to develop their own map.

Garry

Pim · Post by **Pim** » Sat Sep 07, 2013 10:48 am

The 123/tune is programmable.

GSR 54D · Post by **GSR 54D** » Sat Sep 07, 2013 10:59 am

Hi Pim

The programmable 123's have only been around a few years the older ones (which are still available new) have set curves to choose from, unless you know a way to reprogram them??

John H.

Pim · Post by **Pim** » Sat Sep 07, 2013 11:17 am

I have the GB6 version, which has generic curves for 6 cylinder engines, not even the Jaguar version. I think it must be possible to reprogram the memory, but don't know how.

AussieEtype · Post by **AussieEtype** » Sun Sep 08, 2013 3:09 am

Pim wrote:The 123/tune is programmable.

Not mine - all preprogrammed

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123 ignition - is there a rev limiter?

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