CDI3 EGR bypass mod

[Homebrewer]

CD 13 mod

Alex,
New here but would be very interested in getting this egr mod for my US spec CDI.

 

[Alex Crow]

Alex,
New here but would be very interested in getting this egr mod for my US spec CDI.

And I would be keen for you to try it, circuit diagram above - help yourself!

 

[television]

Excuse me from saying but 643Ω is a odd value and if it must be so then a 560Ω and a 82Ω will give you 642Ω in series

 

[Alex Crow]

Excuse me from saying but 643Ω is a odd value and if it must be so then a 560Ω and a 82Ω will give you 642Ω in series

Indeed it is malcolm, it just happened to be a value that worked.

I used 1k and 1.8k in parallel, will be nice to have a longer run of the test soon.

 

[television]

Indeed it is malcolm, it just happened to be a value that worked.

I used 1k and 1.8k in parallel, will be nice to have a longer run of the test soon.

When I get my diesel MB I will try it out with variable controls in the front with me

 

[S.Speed]

I recon Malcolm is a Cyborg sent from the future to save mankind..
He definitely has a positronic brain with not so fuzzy logic..

 

[Homebrewer]

Alex,
Help please. Ordered the bits and pieces to put this together. Unhooked the connector from my egr valve and there are three wires in the connector, a red, a brown, and a yellow and grey. Any idea as to which is the pwm and which is the maf? I would assume Ov in your diagram is ground? Thanks for any assistance you can provide.

 

[Alex Crow]

Red is +12v
Brown is 0v
Grey/yellow is PWM

 

[Homebrewer]

Thanks!!!

Alex,
Thanks! Will let you know how it goes once I get it together.

 

[Homebrewer]

maf connection

Alex,
Sorry to be a bother, but I can't tell from your photos where you are picking up the maf connection. Also is the connection in series or parallel? thanks.

steve

 

[Alex Crow]

The MAF sensor connection is just tagged into the MAF wire between the ECU and MAF sensor - do not disconnect the MAF sensor from the ECU!!!!!!

 

[Homebrewer]

Maf wiring

Alex,hate to continue to be a bother, but which wire from the maf to the ecu did you tap into? I have 5 wires: a blue, a brown, a red and blue, a violet, and a green. thanks.

steve

 

[Alex Crow]

So far as i can see, that will be pin 5 at the MAF sensor, red/black wire.

Depending on ECU version it may be pin 85 at the ECU engine harness connector.

When I did the trial I found it by testing with a voltmeter, hence a little vagueness.
According to DAS the signal wire from the MAF is pin 5.

 

[Homebrewer]

Alex,
Finally got everything together. Took a test drive and the car defaults to limp home mode. No codes set, just goes into limp home mode . Did you experience this during your trials? I think r3 value may need tweaking.

I have also attached a picture of the board I built and enclosed in an old drill case.

 

[Alex Crow]

No 'limp mode' for me, if I had had a problem with it I would not have declared it worked!
I did use the 647 engine for a testbed though.

Limp mode with no codes?
Are you sure about that?
What scanner are you using?

What do you mean by 'limp mode'?
This is an often used phrase, but can mean different things for different people, so please define.

I imagine that yes, R3 needs a tweak for yours - assuming you have assembled and connected it correctly of course!

That is, EGR valve unplugged, 3x connections to the 3x wires that should go to the EGR valve, and a T connection onto the MAF signal wire so that the MAF sensor and ECU remain connected as they were before.

 

[Homebrewer]

Alex,
Not questioning your design at all. I'm sure it works. I'm just looking for some guidance. My description of limp home is lack of power because the turbo is not engaging. I am using a Toptox tp-280 scanner. Granted it is not the most sophisticated scanner on the market, but I have used it in the past to retrieve and erase codes on this vehicle. I have triple checked the connections and the circuit board. I have a quick connector between the egr and the circuit board so that I can quickly alternate between the factory set up and this mod. My next step will be to get an adjustable resistor for r3. Didn't mean to ruffle your feathers, I really do appreciate the help you have provided. Will get back to you once I get it up and running.

steve

 

[Alex Crow]

No sweat Steve, but lack of boost would suggest a fault code being logged.

Does it reach full RPM as before?

Do get a variable resisitor, but in the meantime, check the MAF voltage (during EGR operation at idle) with and without the MOD to see how far out it is.

 

[Homebrewer]

Alex,
Finally was able to get back on this project today. Without the mod ,maf voltage is 1.8 volts. With the mod, voltage is 2.1 volts. Changing the value of r3, up or down 82 ohms seems to have no effect. I am now getting po401 code. (insufficient egr) I am certainly no electronics guru. Suggestions?

 

[Alex Crow]

Alex,
Finally was able to get back on this project today. Without the mod ,maf voltage is 1.8 volts. With the mod, voltage is 2.1 volts. Changing the value of r3, up or down 82 ohms seems to have no effect. I am now getting po401 code. (insufficient egr) I am certainly no electronics guru. Suggestions?

That is very telling, you may have got the diode the wrong way round?

What is the MAF sensor voltage with the EGR closed, eg after a prolonged period of idling?

Are you sure that R3 goes to a ground?

Are you sure the transistor is correct, and wired in correctly?

 

[Homebrewer]

Alex,
The diode is installed correctly, the maf voltage is approx. 1.7 v after prolonged idling, r3 goes to ground, and I changed the emitter and and cathode leads as these were installed incorrectly. When I remove the factory connection to the egr and mod is not installed, maf voltage goes to 2.1-same as if mod is installed. With mod installed with transistor wired correctly, I am still getting po401 code and limp home. Like I said earlier, I am not an electronics guru, so any help would be appreciated.
As an additional note, this is a US model, so maybe mod might not work?

steve