View Full Version : Alternator output to ecu

26-11-2013, 08:27
Hi Guys, just doing a V8 swap and need to sort out the instrument cluster, Paul has advised me to keep the communication between the old ecu and the instrument cluster, but due to everything now being Audi I just need to know what the original Toyota alternator outputs as a charging signal to the ecu so i don't blow anything. is it +5volts logic level or +12volts, I'm hoping it's a standard +12volt then switching off once the alternator makes voltage. My Audi alternator is a standard affair +12volts switching off once charging has commenced.

26-11-2013, 17:14
V8 swap?? Where have you been hiding??? I demand pics!!!

(Sorry I couldn't be more help)

26-11-2013, 23:11
it's on youtube under dna Ferrari replica mr2 mk3

27-11-2013, 00:02
Welcome Darren. That sounds just awesome.

Here's the vid folks:-


27-11-2013, 07:13
Dude seriously nice one!!!!

27-11-2013, 08:02
Although not part of the topic, I'm not happy with the exhaust note, so I've commisioned another bespoker muffler, it will arrive next Wednesday. I'm trying to achieve a sharper more 'Ferrari' type of sound.
Didin't think this was the sort of thing the MR2 owners club would be interested in. but if you are I'll do an official post in the V8 section

27-11-2013, 23:15
Do it. We love this stuff.

You must be mixing us up with some of them stuffy types.

Back on topic though - if you find a WSM for the Mk3 there should be sufficient information for you to trace what voltage runs into the ECU based on the pinouts and flow diagrams.

Not quite the absolute answer you need but its should be 'findable'. Annoyingly i have every WSM nearly apart from the Mk3!


28-11-2013, 08:13
The workshop manual only shows the wiring into the ecu, guess I'll opt for logic level first then +12v. I only need to get the Dash ecu to change over to operation mode, I'm modifying the instruments to mimic the f430 instrument cluster.
I'll start a build diary soon, although it's all available on the DNA Owners Club.

28-11-2013, 09:56
The alternator runs the same 3 wires, only the warning wire goes through the ecu for the dash can bus. it is grounded I believe when the charging light it on (12v). Alt Sensing and 12v IGN feed are 12v too.


29-11-2013, 20:14
I urge anyone who hasn't checked out the build thread yet to do so - only up to page 15 so far but what a mind-blowing read!

Keep up the good work and hope to see the finished article soon!


09-01-2014, 16:21
Had a bit of a blonde moment with the Alternator, I was thinking too much, 12v+ then internal rectifier switches to ground when the Alternator starts to charge. Same as toyota

Added Note

The original toyota ECU runs a canbus (TX/RX, toyota call it MPX1/MPX2) to the combination unit, this feeds ok commands back and forth, I've found that simple things like the handbrake light won't go off unless the engine ECU detects the alternator charge light function, Basically I need to have the Toyota ecu connected up, I've also checked signal calibrations for my VEMS tachometer output (12+ pulled to ground to give pulse). Now reading as desired, I'll calibrate the tacho via the VEMS when it's dyno'd.

I fabricated a fuel tank a while back using a vw passat fuel pump and sender unit, unfortunately an earlier toyota fuel sender test ended up in flames, so I didn't have a reference for the correct type of resistive signal back to the gauge (combination meter) I tried everything to get a reading and turn off the low level light, but to no avail.

A recent purchase from ebay for a toyota complete pump/sender unit has now enabled me to get the gauge working, I've got to encorporate the toyota fuel sender into the VW package, thankfully not too much hassle.
My original reason for the post was to ask about the slow movement of the gauge, I was checking out all voltages and ohm readings to and from the gauge, all parameters seemed to conform to the toyota specs but I couldn't get the gauge to move, I went into the house to look at another dial set and left the ignition on by mistake, 3/4hr later I came back into the workshop and the gauge was reading full! so it's fine

My Question is: Are these gauges dampened this much, I realise the integrated circuit controls the voltage to the gauge, just need to be sure they are really slow to move, I approximate about 20mins empty to full, I haven't checked if the combination meter speeds up it's rate of voltage change if the engine's running.

09-01-2014, 16:59
More Ferrari like exhaust note.....?

Please sir, can i offer the flat plane Vs cross plane explanation again?


21-01-2014, 15:36
Maybe I should have explained my ambition a little more- to produce a 'replica' that I'm realistically happy with. I'm aware of the flat/cross plane-firing order- head design obsticles for my build and therefore the type of pulse generated by the ferrari design. This topic was covered 4 years ago in my build, the object is to get as far away from the American v8 burble as possible, I may look into the Helmholtz theory and design a little further down the road.

21-01-2014, 19:43
Fair play. Should be interesting, and I think achievable with some creative exhaust manifold design...

14-06-2016, 20:50
Having a bit of fun around the track

14-06-2016, 22:04
Damn that sounds good!

Sent from my E5823 using Tapatalk

Paul Woods
15-06-2016, 07:57
Fantastic job, very well done.

08-10-2016, 10:58
Should post a little more often
Car at the dyno after having Gunni (vems ecu programmer guru) calibrate the ecu ready for mapping

An update of the car at home


Here's how she looks at the mo:
http://www.twobrutal.co.uk/forum/images/recovered/2016/10/45.jpg (http://s8.photobucket.com/user/dangerrous/media/FILE0004_zpsxfzmrzwq.jpg.html)