hiya all,
Just building the loom for my vems ecu to run a rover v8 4.6 engine.
As its all electronic with coil packs, and that i no longer have a coil to take the engine rpm from.
Where can i now get a rpm input for my vdo rev counter.
Can i configure the ecu to supply the rpm reading somehow?
cheers
scott
There are a few options - using the Stepper to send a +12v signal to the gauge, or to use a pull-up resistor (about 500ohms) between 12v and the tacho line (tacho to a spare driver).
Then use the Extras->Tachometer Output Settings to control the line
rob,
wow you got me there, please allow for the fact i am a very newbie in this area.
Where do i take the wire (output) from the ecu from???
I know there are some spare channels, but i dont know what i can do with these or how to use them...yet
I could looking at the vdo info, use the W pulse from the alternator, but i dont know how accurate this could be.
As i dont really know how my ecu is configured, as dnb supplied it, but i havent powered anything yet.
thanks again
scott
You can select one of the relay channels. Which is a P259 channel.
When you have done that the ecu is giving out a square wave that is the tacho signal. This is a grounding signal.
So you´ll need a pullup for it to register with the tacho.
You do that by connecting from a 12V wire to the tacho signal through a resistor, something like 2000ohm´s works fine.
Similar to this.
(http://lt1swap.com/pictures/tach_circuit_fix.jpg)
The tacho should be configured as P259 output 4 (EC36 pin 3)
You can change this to any output you have spare, but you're a bit limited on spare output because it's a v8 with a stepper motor... ;)
If your tacho is expecting a signal from a coil, it is unlikely VEMS (or any aftermarket ECU) can drive it without a tacho converter box unless the tacho itself can be configured to accept low voltage inputs. The converter box is a simple thing containing an inductor, resistor and diode, so it's possible to make one.
And as you say, there's always the W pin on the alternator. But like you I am unsure how good this is. It does work for diesel Land Rovers I suppose...
i have an autometer tacho in my v8
will i have to do the same above too?
Just read up on VDO tachos. It looks like they accept a signal from the ECU without extra bits :)
Not sure on the Autometer yet Tony, but I expect it'll work.
cheers mate,
i have the divider set to 8 thats right isnt it?
i know its an eight cylinder but any thing is possible with the ecu settings lol.
the autometer tach dont work,
the tach is set to 8cyl
and the vems set to divider 8
tried every thing from 4 to 32 in the divider with not even a twitch,
looks like im going to need the above box etc to get it working,
searching autometers web site,
they list this:
http://www.autometer.com/productPDF/0561B.pdf
fitted the resistor as above today and no tach,
am i missing something?
Now you need an oscilloscope on the wire or a light bulb to see if there is anything on the wire
so instead of going to the tach, if i run the tach wire to a bulb, and the other side of bulb to 12v yeah?
it should flicker on and off at idle yeah?
or have i got that wrong?
Tach is the 12v, other side to ground.
It should flicker in relation to the rpm´s , the more rpm´s the faster it will blink and brigther
cheers mate, will give that a go this week,
p259 ch0 has pull up resistors on most board. So you can use p259 ch0 without adding resistor.
not sure regarding my board,
wonder if Rob or Dave would know,
how can i tell if ones fitted?
CH0 thats pin4 on the ec36 yeah?
as used by the cooling fan if used,
im not using the fan on mine so can use this instead of CH1 what the tacho is on now,
you can measurement voltage on that pin. 12V when is disable, 0V enabled.
cheers mate will do that tomorrow,
i gather thats with tach output enabled and disabled on ch0?
if i get the readings you posted does that mean i have the pull up resistor fitted?
Quote from: Tony C on November 02, 2009, 05:01:25 AM
cheers mate will do that tomorrow,
i gather thats with tach output enabled and disabled on ch0?
if i get the readings you posted does that mean i have the pull up resistor fitted?
for test you can use water pump output. Put 100C and if you have 12V then you have pullup resistor.
set waterpump channel like this?,
(http://www.capriracing.co.uk/vems/ecusetts.gif)
You'll probably need to use a LED. Bulbs require more than the maximum 350mA from a P259 output to light...
ah not got any leds at the mo,
will try the water pump channel first to see if i gets 12v, if so will try the rev counter on that pin.
They all worked when the ECU was here. I got the test box LEDs to flash using each P259 output as the tacho output in turn.
strange,
wonder why the rev counter wont work then,
any ideas?
Is it wired up right and known to work?
What you could do is wire the tacho up, the signal line should trigger of a injector pulse.
yup wired correctly
and was working fine last year when i was running a coil and dizzy.
Can you verify the input the tachometer likes to function
this im not sure of mate,
just found this on Autometers website,
our tach needs to see (12v square wave).
some more info on the autometer tach,
http://www.egauges.com/ATM_Tips.asp?TipPage=green_wire.htm
and autometers tach adaptor,
http://www.autometer.com/download_instruction/0561B.pdf
That really leaves you few options but to get an oscilloscope on the current tacho wire to make sure it´s actually working.
getting hold of an oscilloscope is the next problem,
the wiring has not changed from running the coil set up,
had a mallory cdi unit which had a tach output,
when this was removed the tach wire was moved from the cdi straight to the ec36 vems plug,
weird aint it,
i have a test meter with rpm on it,
if i connect this to the tach output wire from the vems would that give us an idea if its working?
Only if you have the 12v and resistor on the circuit.
Can you measure continuity from the vems tacho output to the tacho?
i'll do that after work tomorrow,
cheers guys.
My tach worked fine with the Mallory CDI box.
I then plugged it straight into points and it didn't work. It didn't work when i connected it the Vems either.
I have just sent it to Autometer and they said there was a resistor fault and it is fixed now. It cost 25 dollars plus shipping. I would have tried to fix it myself, but I couldn't work out how to remove the front rim without damaging it.
I wonder if the mallory CDI damaged both of our tachs?
let me know if it works when you plug it in this time mate,
i may have a go at taking mine apart,
in the long run i want to use the o/e capri/rover hybrid rev counter in the dash,
as it looks factory,
and use the shift light from my autometer rev counter and let vems control them both,
I wonder if there simply isn't enough drive current from the P259. 350mA isn't exactly a lot... You have 6 IGBT channels, so there are 2 spare after the coils. You could try a spare one of these - they can deliver a lot of current.
I wrote on the case the IGBT channels that aren't populated to give you a clue.
checked ch0 as requested, no 12V when its set too 100 and p259
checked contu from vems back to tacho and alls fine,
will give the resisitor another go the weekend,
whats should i be looking for on the divider?
Quote from: dnb on November 03, 2009, 06:15:06 AM
I wonder if there simply isn't enough drive current from the P259. 350mA isn't exactly a lot... You have 6 IGBT channels, so there are 2 spare after the coils. You could try a spare one of these - they can deliver a lot of current.
I wrote on the case the IGBT channels that aren't populated to give you a clue.
ah rite,
will have look when its light, maybe weekend now mate,
will i still need to use the pull up resisitor?
The ignition channels are called I259. They are selected in the same way as you would a p259 channel.
You will need a pullup resistor.
still no joy,
the car was at the alarm specialists today also,
it has a CAT1 clifford alarm fitted with intelli start,
this runs on ANY set up as it just needs to detect a varying voltage to arm the remote start,
even the clifford could not detect any rpm output from the ecu,
any ideas?
Has the ecu been tested by somebody else?
Dave (dnb) repaired the trigger prob for me,
not sure if he tested the tach output though,
Maybe Dave could reply, ;)
Quote from: Tony C on November 03, 2009, 05:21:09 AM
let me know if it works when you plug it in this time mate,
i may have a go at taking mine apart,
I got mine back today. I'd definately try and open it yourself, Autometer charged me 25$ for fixing and cleaning it but 75$ to post it back! It only cost £7.20 to send it there
Still it is cheaper than getting a new one.
I'll let you know if it works now! I fitted a pull up resistor inside my ECU, it didn't have one originally (although the pads are there)
have tested the tach output in doors tonight with my rpm test meter and with resistor fitted,
am getting a reading on both p259 and i259,
but only the i259 with give a sort of reading on the rev counter i have sat here,
is using the sound gen a good way of setting up the tach channel?
or should i wait until its all back in the car???
may remove the autometer rev counter tomorrow and see if that gives a reading sat here in doors.
have the autometer rev counter working on the pc in doors with the vems and signalgen and I259 ch1,
I also used a different pull up resisitor (have a pack of 100 here), looks like the one i was using may be faulty :-(
going to lay it all loose in the car, (in the footwell) and see if it works when back in the car wednesday night hopefully,.
Well done there Tony :) DO you mean an I259 channel was faulty or the pullup resistor was faulty? If the former, remember that you only have 6 populated IGBTs, not 8 so 2 channels shouldn't do anything.
nah the resisitor was faulty mate ::)
going to go round and try it out later,
may also try the o/e dash revcounter if that works will ditch the autometer one and use the shift light off of it and let vems control it,
yipeeeeeeeeeeee
have the in dash O/E rev counter working off the vems,
have run the wires for the shift light tonight also.
http://www.youtube.com/watch?v=97UaSxY3RgI