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Wiring a Link Monsoon G4x to a Cosworth YB engine - I've created a schematic but is it correct ?


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Hi Everyone , I'm very new to the world of engine management (being more used to contact breakers & condensers !) but am very enthusiastic ! .  I've been lurking for a while but this is my first ever post. I'm building a Cosworth YB Turbo powered Ford Escort Mk1 and have bought a new Link Monsoon G4x to take care of the engine management. I'm also using a boost control solenoid and a Wideband lambda controller. 

I'm going to be making my own wiring harness using a Link Loom A as the basis. I figured the best place to start would be to fill in the I/O table and use a schematic for myself to follow. i couldn't find anything that i could copy during a google search ( lots of mazda rotary stuff) but nothing for a typical 4 cyl turbo motor. I also looked in the PC Link help files , and whilst theres some great detail in there - its all split up into individual sections and i couldn't find a total 'system' wiring diagram . 

So , I've created my own - and here it is . However - this is my first ever go at doing something like this , and i'm bound to have made some schoolboy errors . Could i ask for the benefit of your experience , and ask you to take a careful look at my schematic and let me know if Ive got anything wrong please ?  

I've followed the wiring colours of the Loom A as best i can , and i'm sure that most of my component symbols are innacurate - but the important thing is are my ECU pins connected to the right places ? 

I'd really appreciate any guidance. 

Lee

Escort 001.jpg

Link Monsoon G4x ECU to Cosworth YB wiring             .jpg

Link Monsoon G4x ECU to Cosworth YB Wiring Schematic.pdf Link Monsoon G4x ECU to Cosworth YB wiring - header list.pdf

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Your oil temp sensor will need a pullup to work on AnVolt 4 (typically 1kohm with one side to the An Volt 4 wire and the other to 5V).
Typically you want both of your WCU Power Grounds (Pins 25 and 34) to go to the same point which would preferably be the engine block ground.
Depending on your tacho type you might need a converter or to do some modification to make it work with the ECU signal (Tachos that are intended to be fed by a coil negative typically need some modification or some form of booster to work from the ECU's Low side PWM drive).

Other than that it all looks good.

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Thanks Vaughan,  I really appreciate you taking a look at this for me . 

A couple of questions- The Link I/O table I downloaded tells me to put one earth to chassis and the other to the engine ?  What does WCU stand for ? 

Lee

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A couple of extra comments from me too.  Although yours is more drawn as a schematic than a wiring diagram, so your intent may be not be to wire as drawn - but if the coils a 3 wire only, then that single ground should be grounded to the cyl head - not back to the ecu.  

Also, the CAN lambda, since it is connected to a "noisy" power source, I would suggest adding the 22uf cap into its power supply/connector.  

For basic 4 cyl installs you can also get away with just a single power supply relay for everything, so you can do that if you want to simplify.  

I have attached a generic 4cyl drawing.

Monsoon-4-Cyl-Generic (2).pdf

As for the question about grounds, I would prefer both to the same point.  Can you show me this IO table that you downloaded - I cant see that comment in any of our current documentation.  

I think the "WCU" was meant to be "ECU".

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38 minutes ago, Adamw said:

I think the "WCU" was meant to be "ECU".

yup

 

38 minutes ago, Adamw said:

then that single ground should be grounded to the cyl head - not back to the ecu

I read that one as ground to cylinder head but yes the coil grounds should go to the cylinder head not to the ECU ground wire.

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12 minutes ago, Vaughan said:

I read that one as ground to cylinder head but yes the coil grounds should go to the cylinder head not to the ECU ground wire.

Yeah I agree, not great wording on my part.  What I was trying to cover is if those particular coils only have a single ground pin or multiple.  Probably K20 coils with 3 wires if I were to hazard a guess. 

Some coils have more than a single ground wire - and when they do they are usually connected to circuits that are better to be kept as separate loops.   For instance the common IGN1a, they have 3 isolated grounds - secondary winding ground goes to cyl head, primary winding ground goes to batt neg, logic ground goes to ecu sensor ground.  They would usually work fine all connected to the same point, but will be more tolerant to noise and will be more resistant to false triggers if done separately.

In this case if they are 3 wire coils, I would typically run the ground wire from each coil separately to the ground point, but then all crimped into a single eyelet at the cyl head.

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12 hours ago, Adamw said:

A couple of extra comments from me too.  Although yours is more drawn as a schematic than a wiring diagram, so your intent may be not be to wire as drawn - but if the coils a 3 wire only, then that single ground should be grounded to the cyl head - not back to the ecu.  

Also, the CAN lambda, since it is connected to a "noisy" power source, I would suggest adding the 22uf cap into its power supply/connector.  

For basic 4 cyl installs you can also get away with just a single power supply relay for everything, so you can do that if you want to simplify.  

I have attached a generic 4cyl drawing.

Monsoon-4-Cyl-Generic (2).pdfUnavailable

As for the question about grounds, I would prefer both to the same point.  Can you show me this IO table that you downloaded - I cant see that comment in any of our current documentation.  

I think the "WCU" was meant to be "ECU".

It's in the Link Monsoon Quick start guide that i downloaded from here > http://linkecu.com/documentation/MonsoonQuickstartGuide.pdf 

It states " Ground + Ground (assuming 25 & 34 ?) Wire these seperately. Ground Typically one to engine, one to chassis" 

Lee

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Thanks for your help gents - its much appreciated .

My intention was to wire it up exactly according to me diagram (with the exception of some of the analogue sensors - but i'll come onto that later) . I intend to convert the Cosworth YB ignition from a Distributor based system to Coil on Plug - using 4 x  Honda K20 Denso stick coils. I'll still be using the phase sensor in the original YB distributor body.

 I've re-jigged my schematic to now ground pins 25 & 34 to a common point on the engine.

I've also re-jigged stick coils to have separate earths which will now crimp to a common ring terminal on the cylinder head.

Adam - what do you mean by a 'noisy' power source for my Link Can-Lambda controller ? - are there better options for the 12v feed ? direct from an ignition fed live on my fusebox maybe ? 

Vaughan - regarding my tacho signal . I'm using a set of gauges from Speedhut in the USA . Their tacho instructions are attached below and they give several options for connecting the single yellow signal wire from their tacho to the car , but in summary :

"Option 3 (coil on plug) - An individual coil is placed directly on top of each spark plug eliminating the spark plug wires.
The signal wire, when hooked up to any coil, will pick up only 1 pulse per 2 revolutions or 1/2 pulse per 1 revolution
(see fig 3). For this ignition the yellow wire from the tachometer will connect to the trigger wire on one of the coils
Typically there will be 3 or 4 colored wires coming off of each coil. The trigger wire will be the wire that changes
color from one coil to the next.
Option 4 (tach output from ECU) - Some vehicles will have a tachometer output wire coming from the ECU. The
yellow wire from our tachometer can receive signal from the ECU by following the diagram in fig 4. (4.7K resistor
and shrink tubing are included with the gauge.) Note: Aftermarket ECU's will NOT need to follow fig 4. Simply
connect the signal wire to the ECU output wire and set the pulse per rev accordingly."

I took it from this , that i can connect it directly to Pin 21 on my Monsoon ECU as per option 4 ? Or would i be better off using their option 3 and splicing in to one of the coil signal wires (Pins 1 ,2,3 or 4) ?

Lee

Link Monsoon G4x  ECU to Cosworth YB Wiring  Schematic v2.jpg

338_tachometer_instructions2021.pdf

12 minutes ago, Adamw said:

Ok, that looks like an old one.  Here is the current:  http://linkecu.com/documentation/MonsoonXQuickstartGuide.pdf

Ok thank you , i just googled monsoon quick start guide and thats the first result that came up. 

Thank you for the updated link

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1 minute ago, UK Lee said:

what do you mean by a 'noisy' power source for my Link Can-Lambda controller ?

It is connected to the same power supply as coils and injectors and idle valve, these are all inductive devices so every time they turn off they send a high voltage spike back down the wire, sometimes as high as a couple of hundred volts.  The CAN lambdas are particularly sensitive to these inductive spikes.  

The CAN lambda quick start guide shows 2 alternative diagrams.  The first one uses its own relay connected directly to the battery (the battery will filter out a lot of these spikes).  The alternative diagram shows it powered from the ECU relay like you have here so it uses a 22uF capacitor added acroos the power wires (this filters the spikes).  Pic below.

Since you have an aftermarket tacho it will be fine connected direct to the ECU.  Escorts originally have a "High voltage" tacho that would not work connected direct to the ecu which is what Vaughan was informing.

R1lkBbE.png

For your oil temp sensor connected to AN V4, you will need to add an external pull-up resistor to 5V like below.

E6oL0fU.png

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Thanks Adam - this is brilliant info ! - the support from this forum is amazing :D I did see the alternate wiring diagrams included in my box when I bought the wideband controller - but had no idea about potential voltage spikes etc :unsure: . My apologies if my questions / assumptions seem a bit naive. :unsure:

Ok , so - onto v3 of my schematic , the earths are now configured properly and I've switched the 12v +ve feeds around so that one relay powers the boost solenoid, IACV, coils & Injectors , and the other relay powers the ecu and the can lambda controller only. Will this negate the need for a capacitor ? 

Now , questions regarding my sensor wiring . All of the engine management related circuits on the '89 Sierra Cosworth engine that I'm using are independent of the main chassis harness and go directly to the original Weber ECU on its own sub-loom (which makes the engine conversion reasonably simple) . Stuff like the Cam / Crank / AIT / TPS & Water Temp sensors are for the dedicated use of ECU only.  My Monsoon X has built a built in MAP sensor , so I think I'm right in saying that these inputs are the minimum I need for my Link ECU to work correctly. 

However - I've installed a bunch of gauges in the cockpit of my '74 Mk1 Escort to display additional info . The Gauges are again from Speedhut , and are digital stepper motor driven analogue dials. They each come with their own calibrated (analogue ?) sensors which I've installed at the appropriate points.  Specifically regarding 'additional' inputs to my new Link Monsoon - I now have access to Fuel Pressure , Oil Pressure and Oil Temperature . At the sensor end of the gauge harness -  the pressure sensors have a 5v +ve supply from the gauge , a Ground back to the gauge & a Signal wire back to the gauge . The temp sensors have 12v +ve from the gauge and a Ground back to the gauge. 

  • Can i simply 'spur' off the signal wires from each sensor - and 'share' that sensors signal between the gauge and the AN Input pins of the ECU ? is it likely to do anything weird ?
  • Do i need to also spur the gauge / sensor ground wires and feed them back to Pin 24 of the ECU ?
  • I've added these ECU spurs to my existing Gauge / Engine schematic (I'm having to rewire the whole car from scratch) - as far as the ECU circuits are concerned , does this look OK or have it got it completely wrong ? 
  • Why do i need to add the 1k Ohm resistor to the oil temp circuit when i dont need one on the water temp circuit ? they're both 2 pin thermistor type sensors - is it because my oil temp gauge is fed by a 12v supply from the gauge and my water temp is supplied by a 5v feed from the ECU ?
  • Is it worth the effort to get Fuel Pressure , Oil Pressure and Oil Temperature info to the link ECU ? Will it make significant use of this data ?

Thanks again for all your advice - i find this stuff fascinating :)

 

 

Link Monsoon G4x  ECU to Cosworth YB Wiring  Schematic v3.jpg

Escort loom Engine & Gauges.jpg

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3 wire pressure sensors you can usually share the signal - so for instance the one oil pressure sensor could be connected to both the gauge and the ecu.  You will potentially lose a little accuracy as the sensor is not referencing the ECU 5V or sensor ground but for oil pressure high accuracy is not usually critical.  It is useful to have both fuel and oil pressure in the ecu as you can use them for engine protection strategies as well as fuel pressure compensation in the tune.

For your oil temp sensor it could possibly be shared but you will have to do a bench test to confirm the pull up voltage that the gauge uses.  So power the Oil temp gauge up on the bench, (no sensor pluged in) measure the voltage accross the temp temp sensor wires.  If it is 5V you can share the signal with the ecu (direct to AN Volt, no pull-up needed), if it is 12V you cant use it. 

As for the question about why the pull-up is needed for the oil temp sensor:  There are two types of analog inputs - Temp inputs and Voltage inputs.  The temp inputs are designed to be connected to a resistance type sensor so they have a 5V 1kohm pull-up connected inside the ecu.  The volt inputs are designed to be connected to a sensor that is powered and outputs its own voltage so these inputs dont have a pull-up.  But your drawing didint originally show the oil temp sensor was also going to be connected to a gauge (which would have a pull-up built in) so if the oil temp is connected to both ecu and a gauge then the external pull-up in the ecu wiring would not be needed.

 

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6 hours ago, UK Lee said:

Can i simply 'spur' off the signal wires from each sensor - and 'share' that sensors signal between the gauge and the AN Input pins of the ECU ? is it likely to do anything weird ?

You can with some conditions:

  • You might run into ground offset issues (slight voltage differences between the sensor ground and the ECU).
  • You might need to make custom calibrations in the Link software for the sensors as they might not be one we have built in calibrations for. (Custom calibrations can also be used to counter consistent ground offsets but this isn't good practice).
6 hours ago, UK Lee said:

Do i need to also spur the gauge / sensor ground wires and feed them back to Pin 24 of the ECU ?

This can result in ground loops but not doing it can result in ground offsets, difficult question to answer.

6 hours ago, UK Lee said:

Why do i need to add the 1k Ohm resistor to the oil temp circuit when i dont need one on the water temp circuit ? they're both 2 pin thermistor type sensors - is it because my oil temp gauge is fed by a 12v supply from the gauge and my water temp is supplied by a 5v feed from the ECU ?

My comment on this wasn't taking into account that the sensor was being shared, temperature sensors typically need a 5V pullup on the signal side as the sensor is just a resistor between the signal wire and ground, the AN Temp pins have built in pullup resistors where the An Volt channels do not.

This means that the Oil Temp sensor will be fine as the gauge will provide the pullup but if the water temp sensor has a pullup in both the gauge and the ECU it will not work properly.

6 hours ago, UK Lee said:

Is it worth the effort to get Fuel Pressure , Oil Pressure and Oil Temperature info to the link ECU ? Will it make significant use of this data ?

Fuel pressure can be used for fuel corrections, oil pressure and temp are nice to have for logging and engine protection features. In my own vehicles I just have the ECU control an oil pressure light because I don't want to do pressure/rpm maths everytime I look at the gauge and a light immediately shows something is wrong.

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Thanks for the explanations chaps - its really helpful .

The link i/o table specifically mentions that pins 15 & 16 are temp inputs for use with NTC Thermistor sensors and AN1-4 are Voltage - i didn't consider this before asking my question on the need for a resistor , again - thank you for the guidance.

Oil Temp

i bench tested the Oil temp gauge as per Adams instructions and I'm reading 12v with my multimeter at the sensor terminal . I feel that it seems to be more aggro than its worth. I'm going to dismiss the Oil temp feed to the ECU. 

Oil & Fuel pressure

Oil & Fuel pressure inputs sound very much like they are worth having , so i want to pursue this. Both are 3 wire sensors (Black - ground / Red - 5v / White - Signal) . Duplicate sensors aren't practical in my installation so i'm going to leave the 5v feed to the sensors as coming from the gauges and spur off the white signal wire and connect these spurs to AN Volt 1 (p17) & AN Volt 2 (p22) . 

The question remains regarding what i do about the ground side for these 2 sensors ? I've never heard of Ground Offsets or Ground Looping - so would appreciate your help with this. Leaving the ground wire going to straight to the gauge would be the most simple option - especially if i don't need to spur off this and connect to Ground out on the ECU (pin 24) . Do you think this will be OK ? 

My intention is to keep the ECU harness completely separate from the main body harness , with just a single plug close to the ECU under my dash for any wires that need connecting from 'the outside'. The Oil & Fuel pressure sensor wires to their gauges will be in the body loom , but will pass very close to the Engine Ground point that i'll be using for the Link ECU . I could easily spur off the ground wire between sensor and gauge at this point and connect it to the same  Engine Ground point - would this help negate the potential  effects of  Ground Offsets or Ground Looping ?

Low Oil Pressure / Check Engine Warning

Picking up on Kris's point regarding Oil warning lights. Currently my body loom diagrams use the std.  Ford low oil pressure switch (single terminal pressure switch that goes to ground at around 3-5 psi) The warning lamp is fed by an ignition switched , fused , 12v supply.  At such low pressure - it's not much of a warning , and by the time it lights up at just 5psi any engine damage is typically done. 

Can i use ECU pin 26 Aux Out (not currently assigned) to ground my low oil pressure warning light - using a programmable value in the ECU (say 20psi) instead of the factory 5 psi switch ? Will the existing 12v supply to the warning lamp be a problem ? 

Going a stage further - is there a way to combine both the low oil pressure and check engine warnings using the same lamp ? I'm thinking that the light could be permanently on for low oil pressure and flash on & off for a check engine warning ? To achieve this, would i connect both Pin 27 (check engine) and Pin 26 (low oil pressure) to the same warning lamp - or could the ECU be programmed to output a continuous ground for my pre programmed low oil pressure value and an intermittent ground in the case of a check engine warning via the same auxiliary output pin ? 

Again , many thanks for your help - its much appreciated

 

Lee

 

 

 

 

 

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9 hours ago, UK Lee said:

The question remains regarding what i do about the ground side for these 2 sensors ?

Dont attach any ground will be the safest.  It will find its way though chassis and back to the ecu.

 

9 hours ago, UK Lee said:

Can i use ECU pin 26 Aux Out (not currently assigned) to ground my low oil pressure warning light - using a programmable value in the ECU (say 20psi) instead of the factory 5 psi switch ? Will the existing 12v supply to the warning lamp be a problem ? 

Yes, that is perfect.  

 

9 hours ago, UK Lee said:

Going a stage further - is there a way to combine both the low oil pressure and check engine warnings using the same lamp ? I'm thinking that the light could be permanently on for low oil pressure and flash on & off for a check engine warning ? To achieve this, would i connect both Pin 27 (check engine) and Pin 26 (low oil pressure) to the same warning lamp - or could the ECU be programmed to output a continuous ground for my pre programmed low oil pressure value and an intermittent ground in the case of a check engine warning via the same auxiliary output pin ? 

The flash/solid for two warnings can be done in the software, only connect lamp to one aux.  

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On 2/26/2021 at 2:55 AM, UK Lee said:

Going a stage further - is there a way to combine both the low oil pressure and check engine warnings using the same lamp ? I'm thinking that the light could be permanently on for low oil pressure and flash on & off for a check engine warning ? To achieve this, would i connect both Pin 27 (check engine) and Pin 26 (low oil pressure) to the same warning lamp - or could the ECU be programmed to output a continuous ground for my pre programmed low oil pressure value and an intermittent ground in the case of a check engine warning via the same auxiliary output pin ? 

You would set up your output to be a GP output triggered by a virtual aux for the CE light, or by oil pressure conditions.  
For Example:
image.png.eb7237ca398cba82c2050fc226e028e3.png

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