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Megasquirt question!


Grant.
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Hi all,

Got a 4 litre v8 that im looking to megasquirt, however my throttle position sensor has 4 wires coming off of it, and i can only find/ have only seen wiring diagrams with 3 wires on them, can anyone tell me what the 4 wires are for? or which one isnt needed (if that is doeable :) )

Thanks :D (Sorry Mods if this is in the wrong area!)

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If you find the answer to this i'd be interested as i'd like my 4.6 plenum back! I have been forced to use a 3.9 plenum on my gems engine :angry: due to megas$&te needing the three wire sensor AND the valve effort thingy on the back of the plenum for the PWM valve. (the 3.9 plenum has these and is a straight swap - just looks cack!)

Steve

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Nothing wrong with the 3.9 plenum, it's how I run my 4.0....

You want pin numbers 1,2,3.

Pin1: +ve, Red

Pin2: signal, Yellow/Green

Pin3: GND, Red/Brown

*edit* Included the wire colours.

TBH, why you need wire colours when you have pin numbers printed on the connectors I dunno.

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What colour wires does it have going into it, any chance of a picture of it ?

I can't think of any TPS that has 4 wires although on some models a feed is taken off for the evaporative control which can make it appear as if there are 4 wires (in which case you'll have 2 red wires).

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No great difference from 3.9 to 4.6 other than appearance, both have the same inlet diameter etc. so you're not losing anything other than bling factor:

Plenums.jpg

^^^

And theres the problem Mr F :rofl: and its also doesn't have the rear stepper motor unit for PWM take off ..../

but

Can't go having a unnamed 3.5 flapper plenum on our shiney 4.0 / 4.6 can we now chap :lol:

(said the Mod with a JED 4.5 cast special Plenum :blink: )

:rofl:

Useful tho to know, what does wire 4 do then ?

Nige

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Cheers mods for moving the post,

will wonder down to the workshop right now and take a photo,

The wires coming off the TPS ( or so i thought) were:

1x red and orange

1x red and green

1x green and white

1x blue and white

Will go take a photo of the plenum and the gubbins now, so an adult can tell me which is which :)

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Just been reading more and more about good old megasquirt :ph34r: ( should really sleep! )

If the sensors are set up as described, can the plenum and the fitted sensors still be used? or are they not compatible with megasquirt? If thats answerable....

Right, time for sleep!! :)

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Just been reading more and more about good old megasquirt :ph34r: ( should really sleep! )

If the sensors are set up as described, can the plenum and the fitted sensors still be used? or are they not compatible with megasquirt? If thats answerable....

Right, time for sleep!! :)

The 4 wire extra air valve can't be driven directly from the old Megasquirt 1 although Megasquirt 2 and 3 will drive it quite happily. I don't think it's particularly easy to bypass the stepper on that plenum although you could plumb one in using one of the spare ports on the back of the plenum. The extra air valve isn't a necessity but it does make life more convenient, particularly for cold starts, it's been over a year since I had a working one on mine, like your 4.0 mine has a 4-wire stepper and I'm currently running MS1 with it, I was using an additional board to allow the MS1 to control the stepper valve but the controller chip on the board went west and I've still not got around to repairing it. A PWM controlled valve like the Volvo one is far simpler to get working with MS1. The stepper air valve you have, unlike the earlier type, can be adjusted by hand so it's a trivial task to either block the air coming through it to use an external PWM valve or to set it to an optimum warm idle position and do without an extra air valve.

The stepper on that plenum is, BTW, a far more reliable design than the earlier one. It's extremely rare for it to miss steps in my experience whereas the older style was notoriously unpredictable and unreliable. It's the same stepper that my engine uses and prior to the driver chip on my expansion board blowing up it worked perfectly for over a year in closed loop idle mode, compensating for engine load and ticking over and starting from cold at any temperature without having to touch the throttle.

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