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I will populated with stuff from my site soon, but if anyone would like to contribute send me a mail or a PM Pictures / diagrams / text anything you like.
But small question: what gauges do you have that read out the wrong rpm?
In one of the FAQ at the end you wrote:
"After much head scratching we purchased a Gunstone gastester with build in RPM read out. Low and behold it turns out the engine is idling around 750RPM which is pretty much spot on. Its the gauge that has the wrong read out. It over reads near the bottom of the scale, sits about right at 2000RPM and above it under reads. "
I need to buy mine, so want to be sure to have proper ones.
Richard spoke to Simon at Marlin today. It turns out the gauge needs calibrating to the BMW ECU signal so we need to send it to the manufacturer with the variation we've read of the gastester and they will tune it for us.
Richard spoke to Simon at Marlin today. It turns out the gauge needs calibrating to the BMW ECU signal so we need to send it to the manufacturer with the variation we've read of the gastester and they will tune it for us.
I thought that rev counters normally had a switch to select 4, 6 or 8 cylinder operation to take care of how many sparks you are getting per revolution ( 2 for a 4cyl, 3 for a 6cyl and 4 for an 8cyl). What make is the Marlin supplied tacho? If it were me I would check with the manufactures first before sending it back....
Funny you should say that, Richard spoke to them today. They suggest BMW ECU's may only send 2 signals per spark and we should try the 4 cylinder setting. I'm sure he'll let me know if he gets around to try it today
EDIT the setting for 4 cylinder didnt work, 8 cylinder seems to be closer. Richard's dug out a very accurate RPM gauge to make sure its not the gas tester that is showing wrong! More to follow...
EDIT the setting for 4 cylinder didnt work, 8 cylinder seems to be closer. Richard's dug out a very accurate RPM gauge to make sure its not the gas tester that is showing wrong! More to follow...
It should be simple to check. If your tacho is set up for 4cyl it should just read 50% high (3 sparks for every 2). So 1000 rpm would read as 1500 rpm etc. If it's doing anything else I guess there is a problem somewhere - either wiring or perhaps compatibility with the ECU (signal level wrong perhaps). Or perhaps the tacho is duff even.
The tacho's supplied by Green Gauges have several options for the signal type - I don't know about the Marlin supplied one....
Pictures / diagrams / text anything you like.