I have an acewell 7859 dash which I will be wiring in shortly. I have a focus st170 engine with oem ecu in my build. I'm wondering if there is any way to get a speed pickup from the engine/ecu or if I have to use the magnet speed sensor supplied with the dash?
All of the modern Acewells will work from pretty much any VSS. Unless you know the no. of pulses per mile it produces then a bit of guess work is involved & you'll need to set accurately using a GPS source to check. Set the P screen to around 40 - 50 & the C screen to the tyre circumference in mm, then play with figures to get accurate
St170 speedo is driven from ecu along the bus. It won't work with most aftermarket displays. Same with the tacho.
I planned on taking a splice off one of the coil switched earth for the tacho, if this is possible??
So in terms of taking a signal from the gearbox sensor, it won't work on the st170??
I have the same unit fitted and used the signal off of the ECU for the Tacho, i'll have a look through my notes and see which wire I used. As for
the speed sensor I gave up trying to use the ECU input and also an electronic sender on the gearbox as I just couldn't get them to work properly
and ended up just using the supplied input for the unit taking input from one of the driveshafts.
Okay, on mine which is a standard 20.ltr blacktop ECU it was Pin 48 from the ECU which is Black/White and this connected to the Yellow RPM input on
the Acewell dash plug b.
big_wasa should be able to tell you which wire it is on the ST170 ecu if it is different.
I think it was setup with 2 pulses per 1 revolution in the Acewell settings
[Edited on 17/2/19 by tims31]
Oli (Furore Products) does do a canbus converter that takes the canbus signal for speed & gives out a pulsed signal that will work with the Acewell, that might be an alternative?
Thanks for info. Just had a look on furore website (where I bought the acewell as it happens) for the can bus converter. Price was around £80 which I
think is money better spent elsewhere on my build at the moment.
Looks like the easiest and cheapest option is to just use the acewell sensor. I have a single magnet supplied with mine, is that all is required or are more magnets better?
Ref the tacho pick up, I couldn't see a specific wire on the st170 ecu that would do this. If this is the case then I can only think that running a splice of the coil wiring would be the best. But would I take it off the +12v feed of one of the two ecu switched earths?
That should do for speed sensor, just need to stick the magnet to the shaft... I'm thinking I'll remove a spot of paint and stick it on with
That should be fine for the speed sensor, just run 1 magnet, no need for more, remove paint & roughen surface slightly, roughen base of magnet too
then clean both with something like meths, not petrol/turps which are oily. JB weld is ideal, never had a magnet come off glued as described.
Re the coil wiring it's the switched side you want & any individual coil will do, the no. you select for pulses per rev will depend on whether it's wasted spark or 4 individual coils, usually 0.5 or 1
Great thanks. There are two switched earths for the 4 cylinders so would the acewell be set at 0.5?
you only connect to one of those; if there are 2 coils for the 4cyls then must be wasted spark, so I think that will be 1, 0.5 is used for a single coil on a 4 pot
Ok thanks, I'll set it at 1 and see how it goes.