Anyone hack the N80 purge valve yet? Or, what ~signal is the ecu reading for evap?

[A1 A2 German]

N80 Purge Valve & Evap Recirculation Gas System.

Outside of software coding, anyone tangibly hack the evap? The N80 purge valve is thee only ecu ~input/output source I know, yet watching tutorials it appears to strictly act as a valve, when I previously thought it acted like a valve AND a meter. If it's acting simply as a valve...what's sending the fault code? We can dismiss the rear 02, as is spaced out and done testing before and after evap delete. That is...unless the rear 02 is so hyper sensitive it needs more then a ~2" spacer when it comes to evap removal.

If the N80 is ALSO a meter then we have a start...from there what parameters is it reading (ohms, resistance, voltage)?

[MetalMan]

N80 is just a dumb solenoid. I think the only code you'll get for it directly, is if the ECU detects a resistance which doesn't match its expectations. i.e. if the N80 is unplugged you'll get open circuit.

Don't quote me on this, but I believe all other EVAP related codes would be determined through the LDP.

[A1 A2 German]

O.k....now we're getting somewhere.

- To be clear I'm '97 A4 B5 1.8t
- I elected to post in S4 as you guys are doing all the neat tricks
- I've redone and swapped around my evap system passing emissions in the past..yet that I've never seen, and certainly wasn't ever located in my front wheel wells, per diagrams.

Curious if I have one... my rear liners are the only part of the car I've never removed.

[Mille Bornes]

Leak detection pump should be back by the tank. Purge valve is mounted in the engine bay. The purge valve is a simple on off duty cycle valve.

The purge valve just controls fuel vapor flow from the charcoal canister to the intake manifold. So normally your fuel tank vents, charcoal canister collects fuel vapor kinda like a catch can, and it's eventually sent into the intake manifold via the purge valve.

You'll get circuit codes if it's unplugged. You might also get purge flow codes if it's working incorrectly. It's also common for a purge valve to stick open and cause evap leak codes.

Occasionally the purge and fuel tank vent close to check the integrity of the fuel system. If the test doesn't pass you get an appropriate evap code.

As far as hacking it... I'm not sure what your looking for. I believe it should be possible to code it out but beyond that... Idk what you could do.

[A1 A2 German]

Thanks!

What I'm attempting to do, and why:

My ~standalone system will not force readiness nor code out evap. With that said, let's attempt hacking the input signal or unit, as too not recieve an error code to begin with. So I guess the next step is to see what the LDP is reading and/or what signal is it sending out to the ecu.

Aka, possibility of a resistor, maybe but ~2' of line that close loops the LDP onto itself...so sees ~vacuum pressure...or what ever it's looking for.

[Mille Bornes]

I think you'd have issues with the the ecm commanding purge flow and not seeing that reflected in afr.

Are you trying to pass an emissions test somewhere? It might be easiest to just swap in a factory ecu with everything coded out, readiness set.

[A1 A2 German]

What I was also getting at is I also don't want to drive around with a permanent "check engine dash light" as need that to pop up when truly needed.

It may not be possible for me to swap back..I'm going from narrow band metered air maf and dv to wideband map bov...there isn't an ecu I can even plug in if I wanted....I won't even have an ecu in the sense.

[bmwpower603]

I currently have a bad misfire under load due to a faulty N80.

Should I just have this thing coded out at EFI express? I’m having my differential replaced there on Thursday. It’s $80 for the solenoid, and probably the same to code the thing out.

[jibberjive]

Not sure I understand, your OEM ECU is what runs the LDP test routine and has the parameters/thresholds for the expected returned values. Are you saying that your standalone ECU is hardcoded with this same N80 test and uses the same values that the OEM ECU used?

[NOTORIOUS VR]

No commercially available stand alone has (or is allowed to have) any emissions related routines or PID's

I'm not exactly sure what the OP is attempting to achieve but the stock ECU's purge valve output is just that, and output that actuates a valve. It doesn't do any type of metering - the ECU does this by monitoring it's normal inputs for the required changes to determine if the EVAP cycle is running and if it completes correctly.

[A1 A2 German]

We've moved on from the N80 purge valve to LDP

"I'm not exactly sure what the OP is attempting to achieve"

A) To determine what type of signal/value the ecu is seeing from the LDP.
B) To duplicate that signal to keep the dash light off, and not to see codes.

Just as either the N80/112/249 valves at times can be defeated with nothing but a resistor...I'm look to start the steps to hack a LDP.


EDIT:

1) So what does emissions station see when they plug into my obd port (yet have a ~plug and play standalone)...just "no connection"?

If that's the case, I'll have to do a "swap back" to an oem ecu every two years and keep my oem harness provisions to run it...not the easiest on my setup as have to change hardware variables too. But....I still need to keep the dash light off driving around when on standalone.

[replica_rs4]

When you running standalone you should not have any emissions related check engine light, unless its a piggy back system on top of factory ecu. If you run standalone only , i dont think you will pass emissions system test thru obd.
Provide some more details on your set up. Ecu brand and so on

[NOTORIOUS VR]

When you running standalone you should not have any emissions related check engine light, unless its a piggy back system on top of factory ecu. If you run standalone only , i dont think you will pass emissions system test thru obd.
Provide some more details on your set up. Ecu brand and so on

This.

[A1 A2 German]

MaxxEcu:https://www.maxxecu.com/products/pluginecu/audi_a4

I was wondering that: Dash Cluster vs ECU
I've seen a dash cluster flag a warning as it doesn't see a value...however the majority of all times the dash cluster is nothing but a visual representation of an issue, and it's the ecu doing the actual reporting.

If I recieve no standalone dash light or codes, that atleast takes an issue off the table. Either way we should get down to "what signal" the LDP is reading/sending.

I may also be receiving a spare LDP, to pull apart and see what we're working with. Hell...maybe it'll be a mechanical hack, aka nothing but a brass contact completing a circuit each time readiness it produced via vacuum or...who knows.

[replica_rs4]

You will not have a check engine light for emissions as it gets triggered by factory engine ecu.