speed signal

[bigbloodyturbo]

Bit of a long shot here but do any of you techies know what kind of signal the speed signal coming out of the odo is. I want to replicate it on a function generator on the bench and I can be ar5ed hooking a scope up to it and driving along trying to look at it.

[JustGav]

It isn't voltage based but rather pulse based, as to how it is laid out within the PWM could be interesting.

[SimonB]

Square wave, 4 pulses per mph/kph IIRC.

[bondango]

IIRC its 4 pulses per revolution Square wave, AC

 

EDIT:

The No. 1 vehicle speed sensor outputs a 4–pulse signal for every revolution of the rotor shaft, which is rotated by the transmission output shaft via the driven gear. After this signal is converted into a more precise rectangular waveform by the waveform shaping circuit inside the combination meter, it is then transmitted to the engine control module. The ECM determines the vehicle speed based on the frequency of these pulse signals.

Edited April 8, 2009 by bondango (see edit history)

[SimonB]

I think it goes in as a sine wave and the odo buffers it and turns it into a square wave. Could be wrong though!

[bondango]

Goes to Dash in Sine, Speedo converts to Square then to ECU. The ECU divides by 4 or 8 before sending to Cruise/trac etc etc

[bigbloodyturbo]

so the active spoiler ECU will see a square wave in four pulses per rev of the output shaft. Is that a +v pulse, does anyone know the amplitude? +5v?

[bondango]

2 V/div needs to be grounded with E2 on ECU. Cant remember if active spoiler ECU is fed speed signal from ecu which would mean its 1/8th (iirc) original speedo signal

[bigbloodyturbo]

2 V/div needs to be grounded with E2 on ECU. Cant remember if active spoiler ECU is fed speed signal from ecu which would mean its 1/8th (iirc) original speedo signal

 

I think i'll have to put the scope on the speed signal when I get a chance, that way i'll know for sure as I don't want any blue smoke:) If i figure it out i'll post it and update the thread for future reference/searches.

[Tricky-Ricky]

Was going to ask something similar, so here is just the place, how/could i configure a logger that can just read a 0-5v signal?

[bigbloodyturbo]

Was going to ask something similar, so here is just the place, how/could i configure a logger that can just read a 0-5v signal?

 

not sure what you mean?

[bondango]

if you can Log Frequency then yes you can log the signal. LM1 Auxbox Channel 2 IIRC will do it

[bigbloodyturbo]

Don't know if its a wideband you want to log or not but if you just want to monitor/log a 5v signal you could try some of the oscilloscope/spectrum analyser type software packages available on the net, some are free and they're not to bad.

[Tricky-Ricky]

if you can Log Frequency then yes you can log the signal. LM1 Auxbox Channel 2 IIRC will do it

 

Ahh yes forgot about that, its LMA-3 and is preconfigured for frequency, but 100mph limit

[bondango]

Ahh yes forgot about that, its LMA-3 and is preconfigured for frequency, but 100mph limit

 

yeah thats the jobbie, i call it my lm1's auxbox handy bit of kit indeed

I remember now that logworks sets the 5v limit to 100mph, but had thought of using a small feq divider circuit on that input which could theroetically give a top speed of 200mph

 

I did build the opto circuit to try and log actual ignition timing but it was useless

[Tricky-Ricky]

I have never had any success with trying to log timing,

I'm presuming that i can splice into the speed wire into the ECU?

I currently log AFR, TPS, RPM, Greddy pressure sensor for EMU, std MAP and knock from my Phormula KS-4.

I use the Logworks software to make graphs that mimic the EMU maps, works very well:)

[bondango]

I have never had any success with trying to log timing,

I'm presuming that i can splice into the speed wire into the ECU?

I currently log AFR, TPS, RPM, Greddy pressure sensor for EMU, std MAP and knock from my Phormula KS-4.

I use the Logworks software to make graphs that mimic the EMU maps, works very well:)

 

Did Phormula get round to getting a 5v out on there stuff!!! I have the ks3 and analyser pro, great we bit of kit.

 

Yep, should be able to tie into speed signal 1, though the EMU will log speed just as good. Section 9 in the LMA3 manual goes into it in a bit of depth, and also injector duty

 

The Timing setup was a bit of a nightmare, i got a freind to build the opto circuit, which had to be placed ablove the crank, which inturn had to be mark with releflective paint - could never get any worthwhile readings..look at section 8.2 in the LMA-3 manual explains how to set it up, and miminc the custom crank trigger from pulley.

[Tricky-Ricky]

Did Phormula get round to getting a 5v out on there stuff!!! I have the ks3 and analyser pro, great we bit of kit.

 

Yep, should be able to tie into speed signal 1, though the EMU will log speed just as good. Section 9 in the LMA3 manual goes into it in a bit of depth, and also injector duty

 

The Timing setup was a bit of a nightmare, i got a freind to build the opto circuit, which had to be placed ablove the crank, which inturn had to be mark with releflective paint - could never get any worthwhile readings..look at section 8.2 in the LMA-3 manual explains how to set it up, and miminc the custom crank trigger from pulley.

 

Yes, i did some of the initial testing of the logable 5v output, its now fully Incorporated into the unit.

I did try piggybacking off the CPS but no joy.

[ADL Mark]

Just resurrect this quickly, I'm trying to get my LMA-3 to log speed from the car.

 

I've got it wired in to SP1 from the main ECM loom but getting differing results, none of which are correct. I think I've messed up the settings on the channel, but not sure. Is there anything else I need to check or change to make it read correctly?

 

Cheers

[mike_mcevoy]

I had a similar issue when hooking up my Defi VSD I could get the revs by taking the feed of the ECU but when I tried that with the Speed Signal it just gave nothing. I ended up taking the signal from the wire coming directly off the Speedo feed from the dash and worked a treat. Not sure if that will help you any?

 

Mike

[ADL Mark]

Thanks Mike, it may well do.

 

If I don't get anywhere with the ECU speed signal then I'll try this, but I've got a fields harness which is nice, easy and clean to tap in to rather than taking the dash off and splicing in across there.

 

I wonder if I've taken the signal from the wrong place as the guys earlier in this thread mentioned that at some point the signal gets changed from one type to another.

[mike_mcevoy]

I know its a pain, I have alone too for that purpose and it bloody didn't work so apart from the Tacho and earth it was pointless me getting one

[ADL Mark]

That's a shame. Luckily mine is well used or various outputs, so it would be nice to have this coming out too.

[Tricky-Ricky]

Thanks Mike, it may well do.

 

If I don't get anywhere with the ECU speed signal then I'll try this, but I've got a fields harness which is nice, easy and clean to tap in to rather than taking the dash off and splicing in across there.

 

I wonder if I've taken the signal from the wrong place as the guys earlier in this thread mentioned that at some point the signal gets changed from one type to another.

 

Thats just jogged my memory Mark (takes a bit these days)

IRC you do need to take the speed signal from after the speedo as its this that converts it for the ECU.

[ADL Mark]

 

Which wire would that be though? I tought the SP1 that I had tapped in to was from going in to the ECU? Is there another that I should have tapped in to?