Skyline’s charcoal canister !

[silviaz]

On 9/24/2022 at 7:36 AM, GTSBoy said:

And, just in case this is a Neo - there is an ECU controlled purge solenoid to determined when vacuum is allowed to be passed to the canister, so it won't purge at times when the ECU doesn't want it to.

Does this apply if you use an aftermarket ecu as it probably doesn't have that functionality built it? (Assuming it doesn't, in my case, apexi)

Edited April 9 by silviaz

[GTSBoy]

37 minutes ago, silviaz said:

Does this apply if you use an aftermarket ecu as it probably doesn't have that functionality built it? (Assuming it doesn't, in my case, apexi)

Well, a proper aftermarket ECU** SHOULD be set up to run the purge solenoid, same as the factory ECU would, so that the tank breather system continues to operate the way it is supposed to.

I have no knowledge of whether the PFC (which is what I assume you mean when you say Apexi) has an output (and internal logic) to run the purge solenoid. If it does not, then given the product design intent for the PFC, which is to be a plug in replacement for the stock ECU, I would consider that a massive failing on Apexi's behalf and would be another reason to think that they were a half-arsed solution to the problem if programmable management on RBs. I would suggest that since Nistune came to market (which is a LOOOOONG time ago now) there has been no valid argument for choosing a PFC, especially if the PFC can't do things like this.

 

**ie, Haltach, Link, Motec, etc

[silviaz]

16 minutes ago, GTSBoy said:

Well, a proper aftermarket ECU** SHOULD be set up to run the purge solenoid, same as the factory ECU would, so that the tank breather system continues to operate the way it is supposed to.

I have no knowledge of whether the PFC (which is what I assume you mean when you say Apexi) has an output (and internal logic) to run the purge solenoid. If it does not, then given the product design intent for the PFC, which is to be a plug in replacement for the stock ECU, I would consider that a massive failing on Apexi's behalf and would be another reason to think that they were a half-arsed solution to the problem if programmable management on RBs. I would suggest that since Nistune came to market (which is a LOOOOONG time ago now) there has been no valid argument for choosing a PFC, especially if the PFC can't do things like this.

 

**ie, Haltach, Link, Motec, etc

Yeah. If I plug the connector in and connect the vacuum lines, I assume worse case scenario is that it simply doesn't work? Yep PFC.

Edited April 9 by silviaz

[GTSBoy]

1 hour ago, silviaz said:

If I plug the connector in and connect the vacuum lines, I assume worse case scenario is that it simply doesn't work?

Yes.

[joshuaho96]

On 12/22/2022 at 12:22 AM, soviet_merlin said:

How does temperature affect the vacuum in the fuel tank? I'm curious now. Because normally leaving the car in the sun is what makes it happen even when not driving the car and using fuel.

But heat expands substances so shouldn't it be the opposite?

https://sci-hub.se/https://doi.org/10.4271/2005-01-3825

Heat causes positive pressure in the tank, a slight vacuum in the tank is normally caused by evap purge during normal driving. If the tank is cooled it can also cause a vacuum that pulls air into the system. The linked paper is quite interesting to learn the state of the art for evap fuel control, modern systems the tank is 100% sealed and the tank is reinforced to handle higher than normal pressure/vacuum. It only opens the vent/charcoal canister when you press the button to open the refuel door or when the engine is running.

After some reading of systems like the W220 S-Class there's a check valve on the tank vent, but the primary reason it's there is because otherwise the intake manifold would be pulling vacuum on the tank: https://w220.wiki/EVAP_system
 

There might be limited vacuum relief via the charcoal canister, but I don't know how sensitive the check valve is.