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Acewell dash speed input
FamilyGuy - 17/2/19 at 09:59 AM

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?

russbost - 17/2/19 at 10:33 AM

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

big_wasa - 17/2/19 at 10:51 AM

St170 speedo is driven from ecu along the bus. It won't work with most aftermarket displays. Same with the tacho.

FamilyGuy - 17/2/19 at 11:35 AM

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??

tims31 - 17/2/19 at 11:50 AM

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.

details here

tims31 - 17/2/19 at 11:57 AM

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]

russbost - 17/2/19 at 04:01 PM

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?

FamilyGuy - 17/2/19 at 04:50 PM

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?

FamilyGuy - 17/2/19 at 07:10 PM

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 jb weld.

russbost - 18/2/19 at 08:13 AM

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

FamilyGuy - 18/2/19 at 09:43 AM

Great thanks. There are two switched earths for the 4 cylinders so would the acewell be set at 0.5?

russbost - 18/2/19 at 09:48 AM

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

FamilyGuy - 18/2/19 at 11:52 AM

Ok thanks, I'll set it at 1 and see how it goes.