Hi guys,

I need some advice on the VSS input to my car.

I have recently fitted a zetec turbo to my cougar and removed the OEM ECU totally. I have a problem now though that I have no speedo. RPM input was easy as I am running EDIS so fed the clocks the tach signal from that.

However I need a digital signal from the ECU to run the speedo and I'm not getting that anymore!

When I had the OEM ECU piggybacked the speedo wasn't working either. I presume because the ECU didn't see the crank sensor anymore it didn't think the engine was running.

Is there anyway around this?? Is there a A/d converter on the market or are there any model of ford clocks that take an analog signal straight from the VSS?

Its an MS1 extra by the way.

Thanks.

 

a quick google of "megasquirt speedo output" shows that they do indeed have an output specifically for this. so just do some googling, hook it up, and switch it on!

thats assuming the clocks are still analog and not CAN or something

 

http://www.msextra.com/doc/ms3/speedgear.html

 

thanks for the reply. That link is handy but its for the ms3 as mentioned I have the ms1 on a v3 board.

 

So exactly where does the VSS come from originally ?

Gearbox sensor, wheel speed sensor, or from the engine ecu via the ABS unit or something ?

You need to establish what sort of signal the speedo needs before you can go anywhere.

 

VSS came from the gearbox. Its an MTX75 box with the 3 wire magnetic sensor.

From there it went into the ECU and is then fed onto the Dash. It would appear the ECU converted the signal from the VSS into Digital for the dash clocks.

When the system was piggybacked I had no speedo either. I think its because the ECu wasn't getting a crank sensor input anymore so didn't think the engine was running..

If I was to put the ECU back in is it possible to use the crank sensor for both an ECU input and also to the EDIS for the megasquirt??

 

3 wire sensors are normally hall. ie digital. Not magnetic.

So you need to check wiring diagrams, and see if the ecu sends out a specific signal to the dash for only the speedo
Or does it send it via some sort of datastream like CAN. If it does, it will be harder to resolve.

Assuming of course you are 100% sure the sender on the gearbox does not operate the speedo ?

 

Just as a follow up I've ordered one of these after doing some research.

http://www.bikersdiscountstore.co.uk...r-v4-pd-18.php

I will let you know how i get on

 

Any reason why you've done that ?

It simply alters the number of pulses to correct the speedo reading. This does too and is a lot cheaper. Although it may also change the signal output if required.
Doesnt sound like that is your problem in the first place though

http://www.jaycar.co.uk/productView....r&form=KEYWORD

 

Have you not just tried to wire the gearbox sensor directly to the dash?

3 wires on the sensor 12v+ earth and signal

 

Yeah I've tried the wire straight to the dash clocks but get nothing. I think its either seeing the wrong voltage or the wrong waveform. I dont have a scope though so can't tell

 

You dont need either until you've answered my questions.

Is there a specific wire from the ecu to speedo that is only for the speedo ?

Until you can say a definite yes to that, you're wasting your time as the info could be transmitted via a datastream and not a raw voltage signal.

 

Yes there is a single wire from the ECU to the dash clock for speed. Another single wire for RPM which is fine since I tied it into the EDIS output.

 

here you go.

My setup is the one on the right.

 

Maybe I'm missing it. But where is the single wire specifically only for speed pulses from the ecu to instrument cluster ?

Or is the drawing weird because it's trying to show 3 different engine setups on a single page ?

If there is a single wire from the ecu, then it will either be a pulsed 0/5/0/5v etc etc, or a PWM signal

A multimeter may give an indication of this if you're lucky. It would certainly be able to give you a dwell or duty cycle reading if it's a PWM signal. And if it's a 0/5/0/5 etc when moving slowly a voltmeter should offer you some into.

You really need a scope though. And again if the drawing looks right, your VSS is already a 3 wire hall effect which will give a digital output and most likely 0/5/0/5 etc

 

Yes the drawing is a bit weird. It shows the 3 engine types for the cougar. Mine is the right hand one.

From researching and speaking to a friend in the states who works in fords design labs he tells me that Fords standard into components like speedos and radio speed sense etc is PWM. Also from what I can gather the VSS outputs a 5v to 0v square wave. So isn't that a form of PWM?

 

You need to be careful to not confuse terms and types of communication.

PWM is often referred to as Pulse Width Modulation.

Fords Standard Corporate Protocol (SCP) databus uses PWM methods to send data on the SCP databus.

however, looking at the cougar dash wiring, there is not an SCP databus connection.

The only databus connection line present is the K-line which connects to pin 7 of the obd connector.

You need to find out where else the k-line connects to and find out if its for fault finding only. The only info i can find is that the K-line in fords is used for diagnostics. In earlier vehicles it needed the L-line so that tools could send a "wake up" signal. However later cars do not (such as most 1998 on fords.).

There is nothing i could find that would suggest the dash on cougars use a databus for speed signal.

On the later cars such as focus etc. it clearly is controlled by a databus and you have the databus + and - line for communication.

The cougar should in design terms be in line with early ford digital dashes that used no databus and just converted the electrical direct connections into the output on the dash. The later generation stuff is all databus.

looking at your wiring diagram for the cougar you will see the system code on the wires is "PC" which is the same system code on fiestas, pumas etc with a digidash for speed sensor (as well as other engine sensors and control outputs). You will also note the number 8 at the start which shows it as a sensor signal.

According to that you should have a sensor signal running up that wire to the dash.

I cant find the cougar wiring diagrams for the ECU but i do know that on other similar era cars the datalink pin 7 k-line does not connect to the ECU so if your diagram shows the same then you can rule out databus communication between the ECU and dash.

In that case your wire between ecu and dash should be sending a digital speedo signal for the dash to use.

If you look at the duratec V6 cars you see a direct connection between VSS and the dashboard. As far as i know from looking at dash units from the different cars, they are the same part.

It looks to me that you should be able to send a digital speed signal to the dash and it should work.

The only thing that could fuck it up is if the pulses per mile calculation is for some reason different on the dash compared to the output on the speedo sensor. Ford speedo sensors of the era are 8000 pulses per mile.

 

Thankyou for that, the v6 is different. The VSS is a gear driven one and I know from other people that have fitted v6 clocks into a zetec that they dont work. The speedo is way out. Think I need to get a scope and see whats what!

 

if you cant bowl it out, then fit v6 clocks and use a cheaper version of the speedohealer thingy to turn down the pulses to give an accurate speedo based on say GPS. worth doing if youre not on standard wheels anyway.

Clocks are usually only Ł20-30 on egay or less at breakers.

 

ok thanks. I will do

 

i dont know why you bought the speedohealer. They all seem to be for bikes. Or do they do a ford version thats not listed??

If youre using a speedo pulse adjuster and a programmable RPM from your ECU then you can fit the ST170 guage faces if you want a change.

The white plastic casing the focus and cougar dash electrics fit in is from the same tooling. Only the black front lens piece is different.

You would need to swap around a few of the warning lamps as there are slight differences on the dial face printing, and youd need to either wire up a spare warning lamp as a fuel low light or cut a hole in the face to show through. Also need to cut a hole for the cougars LCD screen on the rev counter that the ST170 doesnt have. also need a 12v EL AC module to run the glowing dial faces.

The RPM scale is slightly out but on an adjustable ECU, easily fixable. use the speedo pulse adjuster to give you an accurate 160mph speedo. Also as youre using an aftermarket ECU you should loose the fuel computer functions as the dash doesnt have the fuel flow information from the ECU.

Im fitting a cougar dash with St170 faces to my puma once ive done some testing and built a loom for it.

 

after talking to the tech department the speedo healer will work on anything. Its marketed for bikes but kit car builders and engine transplants have used them with success. My only problem is my RPM signal isnt adjustable. Its fed from the EDIS module so I cant do anything with it. I guess I was lucky that the RPM guage was spot on with the megasquirt reading.

 

The difference between st170 and cougar rpm scales is only slight TBH. St170 goes upto 7.5k where as cougar goes to 8k.

 

The Jaycar unit can adjust any pulsed signal so may work with the rev counter as a last resort.

But if it's a normal volt based swing needle they are easy adjusted anyway ( at least downwards )
You can stick an adjustable pot on the needle actuator, but many rev counters will have a trimming pot on the circuit board anyway, so often there is some adjustment.
If it's a stepper motor then you're screwed, you need the signal adjusted.

As for the speedo, the Jaycar will adjust +/- 100% on the pulses and even an idiot can build it ( I managed it in around an hour, so it must be easy lol )

Setting it up in my case was easy too, the default settings for pulse in/out worked ok, and I just needed to trim my speedo after that.

 

Couldnt see any pots on the circuit board when i had a look.

I like that jaycar site. Seem to have decent kits to build. A bit like a version of maplins that wasnt full of crap tat.

Similarity between focus and cougar dash shape:


could use a focus RS dial face too i guess.

 

Maybe it's mostly older stuff that have them. It could be hidden in behind the face itself. My granada clocks had a pot ( not all ages did though ), and my old Volvo clocks had one too.

But if there are only two wires going to the coil of the swing gauge, it's easy to trim them down to read lower using an adjustable pot.
I guess with more electronics skill than I have ( almost none ) you could configure them to read higher too.

 

Thats surprising how similar they are. Well the healer will go on ebay and I get one of those Jaycar Kits. I have also ordered a handheld scope from maplins as they had one on offer.

Thanks for all your help on this guys. You have really been a godsend. I will let you know how things go on!

Warren If you need any cougar parts let me know. I am the owner of the national uk owners club and have a friend who breaks cougars 20 mins up the road!

 

TBH, as much as I'd like a handheld scope myself, one of the USB based laptop scopes will be more useful.
Can just be bulky to use though.

What sort of money is the Maplins one ? Does it have a decent screen ? can it record ?

 

I would buy a cougar as a daily however with no NCB to use on the policy i end up paying silly amounts at my postcode. ie double what i pay on the puma cossie!!! Id probably have a v6 and LPG it for daily use. Would be quite cheap to drive compared to the cossie yet still fun.