EVAP Delete, help needed

[Twilight_0524]

Good day guys.

I recently converted my n54 to Maxxecu, which replaced the stock MSD80 DME, as far as I know, we have a purge valve to let intake suck all the gas vapour in tank to equalise pressure difference due to gas evaporating, and DMTL pump or charcoal canister only in Euro versions to pump fresh air in to avoid vacuum. It was handled by DME, however now its no longer there, I wrote a logic in my new ECU to activate the purge valve if some conditions are met (MAP < -8 psi and pedal position < 1%), this will make sure the intake can suck excessive pressure in tank, however I have no idea where can I vent fresh air in, my thought is there might be a check valve or similar mechanism that either I can mount to esxiting ports for charcoal canister / DMTL system as I can remove them anyways, or if I can still utilise stock system (Hopefully).

I appreciate all your help, thanks guys.

 

[Twilight_0524]

Sounds like a neat project you have with the Maxxecu conversion! You're right that the factory DME controls the purge valve function and related activities, such as the evap system. With the logic already written to control the purge valve under specific circumstances, you're on the correct path.

As for venting fresh air into the system, you’re right that the DMTL pump or charcoal canister system in the Euro versions is designed to handle this, essentially pulling air into the system to avoid a vacuum in the tank. Since you’re considering removing those, you’ll want to look into a check valve or venting solution for the tank pressure equalization.

You might be able to reuse the ports that are already present for the DMTL system or charcoal canister, particularly if you're taking them out. Just be sure to ensure that there's a non-restrictive method of letting air into the system without affecting the overall function. A few people have replaced the original parts with a check valve or simple vent valve. If you want to maintain more of a stock feel, using the original system (if possible) is a decent alternative, but you'd need to ensure that the Maxxecu will integrate completely with the stock evap system or whether a workaround would be necessary.

I'd suggest double-checking to see if your ECU logic is programmed to deal with the pressure equalization within the tank as well as any evap-related trouble codes, as those systems sometimes throw codes if they're not dealt with properly.

Hope that's helpful! Let me know if you need more information or if you have further questions. Cheers!

At this point I was wondering if I can leave DMTL as is just like when someone code it out with stock DME, maybe it is passive so if it was left uncontrolled fresh air can still enter the tank?

 

[Jern54]

I went MaxxECU as well and I don't use evap on my EU E91 Car. It's not needed since the fuel cap has a vent hole acting both ways.

 

[Twilight_0524]

I went MaxxECU as well and I don't use evap on my EU E91 Car. It's not needed since the fuel cap has a vent hole acting both ways.

Thats great, I will hook up the purge valve to my ecu, good to know there will be a vent hole to allow air in. By the way may i ask how did you set up the fuel system? I am running 750cc injectors (1050cc @5Bar ), one thing bothers me is seems like map pressure will cause effective fuel pressure to drop.