Unreliable RPM Reading on K series

[DougieB]

Hi, I'm hoping that someone can provide some insight into why I would be getting unreliable RPM readings. The needle seems to be slow in responding to engine revs and sometimes will not move at all. The result of this is that the rev limiter keeps on kicking in when I do not expect it. Has anyone else come across this ?

 

The car is less than 6 months old and a K series.

 

 

[robmar]

They all do that sir, well on the latest version of the caterham K series engines called EU3, if it has a black plastic cam cover then you have one.

 

Caterham have been working ona fix for some time, call them and ask to be put on the waitinglist for when they get it fixed. It is something to do with the fact that the ECU is sending the rev counter feed and somewhere along the line there is a distortion which means that the rev counter is not reading all the pulses.

 

I have fixed mine when a electronics friend helped me fit an aftermarket shift light system

 

"we put a resistor was 1K, 1/4 Watt, and it went between the +v (red of the ecu light system) and the revcounter_out (from the ECU) which was green- The problem was that both your rev counter and the shift light had pull-down resistors on their inputs, and the output stage of the ECU was open-collector, with what appeared to be a 4K7 or so pull-up. This pullup was being overwhelmed by the pulldowns on the counter & shift light, and no-one ever saw a 'proper' pulse. With the extra pull-up, the ECU 'won', and was able to put out a good pulse train that both the counter and shift light were happy with. It's not clear why the ECU was so gutless - although I guess they were never expecting to have to drive anything other than the standard Rover rev-counter (which may have had a pull-up internally, I guess). ANyway, the extra pullup is unlikely to ever cause a problem - the current is still pretty tiny.

 

Rob

 

 

 

 

Edited by - robmar on 5 Nov 2001 15:23:19

[JP]

I had the same on mine (99 1.6KSS) - fault was with the rev counter (Caterham gauges) - problem sorted by replacing with a newer dial.

James.

[Ian B]

Have a similar problem on my 4 month old K-series.

 

The rev counter sits at 2000 all the time, until you rev above that, when the needle goes backwards and drops to zero!

 

It was fine until it went back for its 500 mile service, however Caterham say they are aware, and are "working on it".

 

 

MI 5EVN