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Voltage too high from VR
Posted: Thu Feb 26, 2009 12:37 pm
by shynsy
Just fitted a ford VR sensor to my lotus twincam.
Can't get a signal on my MSII..
Checked the wiring, fine..
Checked the AC voltage from the sensor when running:
3.5v @ 600 rpm
is this too high?
Could this be why I don't get a signal on my MSII..?
If not, what could it be?
Cable is shielded...
Should I adjust the pots R56 &R52?
Tim
Re: Voltage too high from VR
Posted: Thu Feb 26, 2009 12:41 pm
by Matt Cramer
It needs to go a lot higher before you lose the signal. Are you using a two tooth crank trigger or a missing tooth wheel? If it's a missing tooth wheel, how is it set up?
Re: Voltage too high from VR
Posted: Thu Feb 26, 2009 1:31 pm
by shynsy
Its a 36-1 missing tooth.
The teeth are cut into the crank pulley and the sensor is held using a commercial bracket.
I have routed the cable to keep away from the coil and dizzy on the existing ignition (although it is within 10-15 cm at one point)
Is this what you mean?
Tim
Re: Voltage too high from VR
Posted: Fri Feb 27, 2009 5:53 am
by Matt Cramer
Yes, that is precisely what I was wondering about. I presume you are using a distributor and not EDIS. At this point I would check three things.
1. The polarity on the VR sensor. If you get it backwards, the MS may see two "one and a half tooth" gaps instead of one double-tooth gap.
2. The wheel decoder settings in MegaTune. If you need help with these, please post your MSQ.
3. The VR trim pot adjustment.
Re: Voltage too high from VR
Posted: Fri Feb 27, 2009 11:29 pm
by john.p.clegg
Tim
When you say "Could this be why I don't get a signal on my MSII..?" what/where are you measuring, are you not getting the 3.5v? at the Ms
John
Re: Voltage too high from VR
Posted: Sat Feb 28, 2009 1:41 pm
by shynsy
Aha... may have sorted it..
I was trying to look at the output from the VR sensor using the MS while the engine was running on a distributor based ignition.
(this doesn't seem to work, perhaps because of electrical noise?)
however I noticed that if I started the engine, the MS picked up the RPM before the engine fired..
Just been out to check the car again. this time cranking without the old ignition connected.
voila! get a signal from the Ms (see below)
cranking RPM.jpg
How does this look?
I have also recorded the signal from the sensor directly with the scope.
I recorded the signal from each wire from the sensor (see below)
VR signal.jpg
How do these look?
thanks for any help
Cheers
tim
Re: Voltage too high from VR
Posted: Tue Mar 03, 2009 12:43 pm
by shynsy
Wahey!!!!
Sucess..
tried starting the car using MS for ignition..
first turn of the key she fired!
then 30 mins of firing, running roughly for 30 secs then dieing..
then switch the VR leads and voila! steady idle..
Had to leave it at that as it is blowing a gale so cannot work with garage doors open, hence risk CO poisoning if I try to tune!
Cheers
Tim (v. V. happy)