EGR valve pinouts (egr cheater thread)

vocky

that's plan E :lol:

but I have discovered something during plan D, so have something else to try first :shock:

h3ppy

i done a bit a of digging today and i believe a capacitor would not work. a capacitor simply evens out voltage (creates a smooth wave by storing the electricity) so i dont think it will work as a gradual switch over although it could help???

wat you need is somehting to act like a dimmer switch to gradually bring the voltage up to 5 volts. but i aint sure on anything you can get to do that automatically???

also, someone i work with said to try put a resistor between the connections of the relay?? he said it might not work as he does not no alot about car electrics and how these things work. but it might be worth a try???

just some ideas for you 😃

rabidh

You'd probably want an FET instead of a relay. I believe they have fairly linear resistance change depending on the voltage going into them. You'd then have a capacitor driving it, charged by a resistor and with a resistor gradually discharging it.

I'm not really confident enough to get all the correct values and stuff but I know someone who is if you decide to do it that way 🙂

h3ppy

done a bit more digging!!!!

a relay is an automatic switch over and will not do it gradually. you need an operational amplifier 8) .

apparantly that should switch it over gradually??!!??

rabidh

Op-amps produce a voltage as an output rather than a resistance, so whether you can use one really depends how the ECU is wired up.

Although if the ECU just puts 0v and 12v across the potentiometer and reads the voltage back you're sorted. I could definitely come up with a circuit that would do what you're after.

h3ppy

i am a bit out off my depth here now :?

i dont no much about electronics, a friend of a friend said to use an operational amplifier! now i am a bit confused :lol:

i think it does just put out 0 to 12v.

we will figure it out eventually :roll:

Steve_Crisp

The fact that it's a potentiometer would indicate that it's expecting more than an "open" reading and a "shut" reading. It would seem to be a feedback potentiometer to tell the ECU how much the valve is open.

Steve

vocky

My aim is to produce a dirt cheap way of removing the costly egr valve, so owners can save some dosh for tuning instead 😃

So a relay [which isn't ideal] was my first thought :roll:

I have already tried to mimic the pot by fitting a 2k resistor between both contacts on the relay and the common.

I have also added a resisitor to the common and this appears to lengthen the time it takes for the eml to appear :?

ps: The closest electronics I've found so far is a voltage divider [0-12v to 0-5v] - this will be plan F :lol:

pps: any electrical diagrams are welcome, but try to keep component costs low 🙂

Steve_Crisp

Looking at the work done so far, I'd say that the potentiometer is offering a voltage to the ECU rather than a resistance - a high-impedance transition from 0v to 5v.

Using Ohms Law, the potentiometer needs to be capable of handling 5/2000 amps, equals 2.5 mA and be rated at about 15mW - I'd imagine that the potentiometer is a 2.2k.

Can you tell me about the actual valve, Vocky? Is it a motorised valve, or a simple solenoid? If it's a solenoid, then is it that applying the 12 volts takes it fully one way, and removing the 12 volts lets it return to rest via this spring?

Steve

vocky

the ecu appears to be looking for a voltage range from 0v to 5v.

the pot is a slider type and simply moves with the solenoid plunger.

It's a basic solenoid valve, with a return spring, 12v causes the plunger to open and thus moves the slider (B) from C to D

I have just doubled checked the potentiometer, it is 3.4k ohms between C - D without the slider fitted [it fell off, it's a very cheap pot :lol: ]

from a good valve I got;

resisitance with 0v at solenoid :
B - C was 1.5 K ohms
B - D was 3.5 K ohms

resistance with 12v at solenoid :
B - D was 1.5 K ohms
B - C was 3.5 K ohms

Steve_Crisp

My best guess is that this'll work with minor tweeking of some of the values: -

Steve

Steve_Crisp

Attachment this time (I hope)!

Steve

Steve_Crisp

You can use a high-impedance volt-meter to tweak the values or the resistors. The diodes are essential to prevent the 5v and 12v rails from interfering with each other.

With no volts applied to the solenoid, the signal-pin is 1k5 to ground, and 3k5 to the 5v rail, which gives a voltage back to the ECU of around 1.5 volts on pin B.

With volts applied to the solenoid, the signal-pin is 3k5 to ground, and 1k5 to the 5v rail, which gives a voltage back to the ECU of around 3.5 volts on pin B.

The circuit required will put a high-impedance voltage of around 1.5 volts onto pin B when pin E is not powered, which rises to 3.5 volts when it is powered.

If they use a power-transistor to drive the valve-solenoid then we might need to load up the 12v rail a bit - in which case we can redesign using your relay...

Steve

vocky

what is the best wattage for the resistors notsure.gif

(I should know this stuff really, but it's 20 years since college :oops: )

ps: you are a genius :lol:

Steve_Crisp

Quarter-watt'll be fine.

I'm the same - it's been a few decades since I was doing electrical stuff!!

Save the compliments until it's working!!! 😃

Steve

vocky

it's just replace the faulty part these days, no component level stuff 🙁

but this is a bit of fun and I've a shopping list for maplins now 😃

Steve_Crisp

Not a bad idea to add a 4v7 zenner diode to stop the signal line ever going over 5 volts. I think something quite small will do...

Steve

vocky

good idea 😃

Steve_Crisp

By the way, if anyone wants to improve on the design then please do so. I'm no longer an electronics engineer - that was a long time ago...

Steve

vocky

the theory is fine, 5v reduced to 1.5 on closed, then valve open signal arrives the voltage rises and is limited by the 4.7v zenner, so the ecu sees a 1.5 - 4.7 voltage signal 🙂

should do the job nicely 😃

plus it only cost £1.03 for the bits, so meets the criteria perfectly :lol:

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