Tacho Not Playing Ball

[tricstar]

hi guys, as the topic says,

tacho seems to work fine until I put my foot down and as soon as it hits boost and the revs go nuts, the tacho needle just flaps around, doesn't follow the engine revs??

was working fine before, but just picked it up today after a tune ( now 710 awhp ,, comes on really hard ) is there any reason why the tacho might not keep up with engine revs?

I can sit there and rev in neutral and is fine needle behaves normal it only happens under boost...

car runs a motec pigggy back and a Blitz standard Gtr computer .

its a pain not knowing where the red line is..

any ideas guys ??

[GTScotT]

I would say dry connection in the cluster itself or bad earth. Try smack the top of the dash as your cruising and see if it jumps?

If so that would mean its got the problem I said above. Otherwise try to narrow down what comes between the dash and the signal source.

[DVS JEZ]

dyno sheet?

710hp is awesome especially with just a piggy back, who tuned it?

[paulr33]

do you have an apexi rsm by any chance

[tricstar]

the sheet is up in the dyno results, posted it yesterday..

and I just looked its a Blitz Access Controler, looks like the standard ecu but badged with that..

the Motec M800 just does injectors, timing etc basically all the engine management and the Blitz there for Attessa etc I think..

just checked the tacho wire at the Blitz, it looks ok but has another wire taped into it ?? I'm assuming that goes to the motec for something, and maybe getting some interference from there ??

tacho only goes on the blink under boost

thoughts.....

[tricstar]

problem fixed

the motec doesn't need a separate tacho feed and was disabled in the motec so cut the wire that was tapped into the tacho wire and all is good..don't know it just started playing up now as nowthing had changed there, but anyway fixed

[paulr33]

for any others wondering why i asked about the RSM i have this issue in my ECR33

powerfc with Apexi RSM. when i go past 5000rpm the RPM needle goes spastic, HICAS flashes and car continues to run fine

under 5000rpm is OK and no issues, go over 5000rpm it goes spazzo. the RSM has a RevO setting and a RevW which is rev output and rev warning

the rev output is used to flick a relay, ie a shift light. but its not wired up in my car, but the feature is always on.

for some reason on my car when RevO is reached the needle and HICAS goes spazzo

the fix for my car was to set the RevO to 10,000rpm so i never reach it. very odd bug and dont know why it occurs