nicksmelly Posted May 11, 2011 Share Posted May 11, 2011 Got engine in and running great on Megasquirt. But we have a problem with the rev counter in the racer. We are using the instruments from a V8 discovery and have the tacho wire from the instruments on the W terminal of the alternator, but the rev counter is reading double what it should. Not sure how to correct that, so was thinking about running the rev counter from an output from the MS. Is this possible? Quote Link to comment Share on other sites More sharing options...
nicksmelly Posted May 12, 2011 Author Share Posted May 12, 2011 Got engine in and running great on Megasquirt. But we have a problem with the rev counter in the racer. We are using the instruments from a V8 discovery and have the tacho wire from the instruments on the W terminal of the alternator, but the rev counter is reading double what it should. Not sure how to correct that, so was thinking about running the rev counter from an output from the MS. Is this possible? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 12, 2011 Share Posted May 12, 2011 Yes, you need to add a couple of bits inside the ECU to do it, or you *may* be able to use the IDM pin from the EDIS (although it may give out a reading when the engine is stopped & bignition on). Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted May 13, 2011 Share Posted May 13, 2011 I've successfully used the IDM pin from EDIS to drive a tacho before. It was as easy as plugging it in. It won't work in every case though... Quote Link to comment Share on other sites More sharing options...
youngy Posted November 29, 2013 Share Posted November 29, 2013 Hi there new here just having a look as to whats what got no rev counter to The IDM you say is that the one witch was a spear .I did try the w on the alternator but like you say it reads double CHEERS Quote Link to comment Share on other sites More sharing options...
zardos Posted December 2, 2013 Share Posted December 2, 2013 Pin 2 off the EDIS 8My digidash works great off the IDM and does not pick up the heartbeat signal when powered up but not running. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted December 2, 2013 Share Posted December 2, 2013 Which rev counter? You may be able to switch it to a different mode with dip-switches on the back of the gauge. Quote Link to comment Share on other sites More sharing options...
stuck Posted January 3, 2015 Share Posted January 3, 2015 Sorry to drag up this old thread but can anyone recommend a rev counter that will definitely work with the IDM pin of the EDIS? Cheers, Mick. Quote Link to comment Share on other sites More sharing options...
elbekko Posted January 3, 2015 Share Posted January 3, 2015 Has anyone tapped into the PIP for the rev counter? It's also a 4 pulse/rev signal, but without the heartbeat and with longer pulses. So any speedo should work with it. Quote Link to comment Share on other sites More sharing options...
zardos Posted January 3, 2015 Share Posted January 3, 2015 (edited) Not a standalone rev counter but the rev counter in a Digidash works with the IDM http://www.etbinstruments.com/DD2_lite.htm this is what I run. Edit they also do normal gauges and say they can usually match to the ECU/Ignition system, so try giving them a call with the specs of the IDM signal (512us 12v pulse for for ignition fire and to ignore a 64us pulse for key off signal when ignition is on but engine not running - from http://www.dainst.com/info/edis/edis.html ) Edited January 3, 2015 by zardos Quote Link to comment Share on other sites More sharing options...
stuck Posted January 7, 2015 Share Posted January 7, 2015 Bump, No one running a rev counter from the IDM? Quote Link to comment Share on other sites More sharing options...
stuck Posted January 13, 2015 Share Posted January 13, 2015 If anyone is reading this looking for an answer I can confirm that a cheapo 8 cylinder 52mm digital tacho from Fleabay works with the IDM signal. Only down side is that it reads 58 RPM with the ignition on when the engine isn't running. It's not perfect but for £12 & a bit of wiring I now have a working rev counter when I don't have a laptop in the truck Quote Link to comment Share on other sites More sharing options...
zardos Posted January 13, 2015 Share Posted January 13, 2015 May be add a simple high pass filter that would cut the short pulses off e.g. a resister and capacitor (http://en.wikipedia.org/wiki/High-pass_filter) Quote Link to comment Share on other sites More sharing options...
stuck Posted January 13, 2015 Share Posted January 13, 2015 Cheers Zardos, It isn't bothering me sufficiently at the moment to worry about it but thanks any way. Quote Link to comment Share on other sites More sharing options...
zardos Posted January 13, 2015 Share Posted January 13, 2015 Yeah just think of it as an EDIS is good pointer. Quote Link to comment Share on other sites More sharing options...
rutthenut Posted February 25, 2015 Share Posted February 25, 2015 I've fitted the Megasquirt-V8 kit from Nigel and also got a TachFix from him to get my tacho to work (this is on a rally Manta, running a Rover 3.5 V8). Can anyone please tell me where the 'ecu' feed for the TachFix should be connected to the MS loom, on which pin? I had tried running my crappy TIM rev-counter from the IDM signal but it didn't seem to want to work for me, hence getting the tacho-fix box Quote Link to comment Share on other sites More sharing options...
rutthenut Posted September 6, 2016 Share Posted September 6, 2016 Ended up taking advice earlier in this thread - got a cheap tacho from fleabay and connected it to the EDIS IDM output, which worked. Seems the tacho-fudge box requires that the ecu has a tacho output mod, which isn't something Nigel does/did. I haven't tried connecting the tacho-fix to EDIS output to see if that would drive my old TIM tacho but might give that a try one day. I would like to fit a decent tacho some time but won't buy one if it isn't certain to work in this installation. With a 5200rpm rev limit, the tacho is mostly there for scrutes to do noise tests at 4500rpm. I really should adjust that to a better (6-cyl?) config... Quote Link to comment Share on other sites More sharing options...
=jon= Posted September 7, 2016 Share Posted September 7, 2016 Which pin on the EDIS is IDM? I have a VDO tacho in mine but haven't got round to connecting it up yet - the MS doesn't appear to have a tacho output and the alternator doesn't have a W terminal! Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 8, 2016 Share Posted September 8, 2016 IDM is Pin 2 if my info is right. As described above, any MS could have a tach output if you add it / request it at build time. Every alternator has a W somewhere, it's a tap off one of the Windings. Rog (istruggle2gate11) did a thread on it yonks ago. Quote Link to comment Share on other sites More sharing options...
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