Abnormally high RPM with jabiru 3300

[jaba-who]

Ran my jabiru 3300 engine for the first time on the weekend. The RPM sensor is picked off from the wire coming off the alternator as per manual.

The RPM readings were all over the place but the general trend was:
at true low enginerevs the dynon reading was reading very high - 4000+ but was, to my ears probably about 800-900 (at idle with the throttle)
As wound throttle up the RPM reading went down. Somewhere in mid 2000s. I guess the real RPM was in the 3000s.

With sudden changes in throttle the whole screen did a jump downwards and blinked and came back up to normal position.

Any hints as to what might be going on. I have rechecked the wiring and the grounds - as this seems to be noted as a cause of all sorts of spurious readings but that seems all right.

(Don't know if its significant but the contact switches have reversed themselves too - see my other posting)

Jaba-who

 

[dynonsupport]

It's definitely not related to the backwards contact names - that's something we've confirmed really exists.

We really haven't seen this behavior before on the Jabiru engines. Check your pulses/rev setting. Per the US Jabiru site (http://www.usjabiru.com/Tech%20Tips.htm#Tachometer%20Installation), your pulses/rev should end up being

2200A engines = 5 3300 engines w/ three phase = 4 3300 engines with single phase = 6

...though, admittedly, this number being wrong shouldn't cause the seemingly reversed readings you're seeing.

Can you describe your tach connection exactly?

 

[jaba-who]

Sorry about the delay in replying. The engine (carby) has been dismantled due to problems of corrosion in the float bowl and jets. It was a brand new carby with float bowl full of corrosion induced aluminium oxide powder - causing engine to run really rough, stopping starting etc.

After re-installing carby, engine now runs smooth. Did nothing else except clean spark plaugs and re-check and confirm all the earths were functioning. Adjusted the pulses-per-rev on dynon. Both dynon and standard dial RPM gauge run in the right direction and rpms match.

Have no idea what was going on and problem seems to be fixed. I'm beginning to doubt my recollections as nothing seems to make sense.

jaba-who

 

[dynonsupport]

That is bizarre indeed, but we're glad to hear that you're up and running!