garrycol Posted May 2, 2017 Share Posted May 2, 2017 I am slowly building my MS3X but going has been slow, partly because of my inexperience and partly because the build instructions are not the greatest. (they really need a professional technical publication editor to go over them). As a result I have have had to undo some of my work and as a consequence my confidence in the integrity of the circuit board is not great. However as I am about to start the testing phase I will soon find out. The engine is a 4.6 V8, currently with the intention of having a Thor inlet and plenum to provide induction. In putting some of the components on the MS3X circuit board I need to know what PWM I have - specifically the number of wires. It is a Bosch item and the connector does have 3 pins in it but I have learnt before that does not mean anything as one may just be a dead connector. So can any one with MS3X and Thor experience advise me on what pin configuration I use for the MS3X main board with the standard Thor PWM. Thanks Garry Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 2, 2017 Share Posted May 2, 2017 As I understand it, yes it is three pin, and it uses them all, supposed to give better control than the 2-pin type. If you stick the Bosch (?) part number in google you will probably find out a lot more. I can't tell you about the MS3 config though I'm afraid Quote Link to comment Share on other sites More sharing options...
Dave W Posted May 2, 2017 Share Posted May 2, 2017 The normal way to control these is to use it as if it were a 2 pin type although it's a bit of a quick and dirty workaround. It works though and that's normal all that matters, especially on such a none critical part of the system. The centre pin on the connector is connected to 12v (ignition switched) and then a power resistor is connected to one of the outside pins. The MS ECU is connected to the remaining pin. The idea is that the power resistor acts as a "spring" pulling the valve to one side by earthing the valve through the resistor. When the MS ECU applies an earth to the other side the valve swings the other way as the MS ECU earth is a lower resistance. By using a PWM sign at the MS ECU it can work against the "spring" and control how far the valve opens. You're best having it so that the "spring" closes the valve, easy to figure out which pin that is by trial and error. Ideally you would remove the "spring" resistor and use the valve as it was intended where it can be moved one way or another by a simple pulsed earth at the appropriate side but last time I looked there was no provision for that although it might be possible to use the four wire stepper control to do it with a bit of rewiring although how effective it would be is anyone's guess ! Quote Link to comment Share on other sites More sharing options...
garrycol Posted May 4, 2017 Author Share Posted May 4, 2017 Thanks for the information - so a 3 pin and I add components and wiring to the MS3 board in accordance with the build instructions. Dave, thanks for the information but I want MS3 to simply run the PWM - not sure I follow the modifications you suggest - maybe what you suggest should be included in the quite poor MS build instructions. Thanks Garry Quote Link to comment Share on other sites More sharing options...
Dave W Posted May 4, 2017 Share Posted May 4, 2017 There is more info on it available here... It's a simple mod that allows any MS ECU to control one of these valves and has been around since the early MS1-Extra days. A few people have documented it but MegaSquirt has become a bit fractured of late and lots of info has disappeared as commercial entities have replaced the hobbyists that created it and a lot of their work and contribution has been discarded. I suggested it because it's the simplest solution as you only have a single wire to the ECU. That said the MS3X (which I assume you have, rather than MS3) can control a 3 wire valve directly, controlling both sides of the valve. I've never tried it though so not sure how well it works. If you have an MS3 you will need to use the resistor mod as per previous MS versions. There are more details on the attached pdf that might help...idle_valves.pdf Quote Link to comment Share on other sites More sharing options...
garrycol Posted May 4, 2017 Author Share Posted May 4, 2017 Yes I have MS3X so now that I have confirmed it is 3 wire I will wire up the MS3 board according to the instructions - I just hope they are all in the one spot and not all over the place like other stuff in the instructions.. Cheers Quote Link to comment Share on other sites More sharing options...
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