Vapor canister fixed orifice necessity for EFI

[FABombjoy]

Just rounding 3rd base on my EFI conversion and looking for some details that I can't find much about. K-jet has fixed orifice restrictors on both PCV and the Vapor Canister inlets to the cold start tube.

-For PCV I think this is so the system can maintain CO without considering any dynamic changes a true PCV valve would present.
-For the vapor canister, this looks like it was for the same reason AND to limit the total amount of vapor purge.

I'm wondering if others have maintained the fixed orifice for the vapor canister or not. I've shortened the cold start tube and installed a 3/8" ID fitting, so the same port can act as both PCV and vapor purge to distribute fumes evenly across the engine. I have PCV squared away but don't want to plumb vapor recovery in a way that's detrimental to the fuel system. Unfortunately vapor recovery best practices seem to be strongly in the OEM domain and most enthusiast forums talk mainly of VC deletion.

[Delorean Industries]

We do not. Especially on boosted applications. This is solenoid controlled via the ecu depending on RPM/map/tps configurations.

[FABombjoy]

Haha, I was afraid that would be an answer.

Might temporary move the purge line pre-turbo (like wayyy pre turbo - just by the air filter) and check valve the purge control hose from the throttle for now. Hoping to be ready for the MI fall drive at the end of the month and I ain't got time for no fancypants solenoids!

Edit: On second thought, might keep it as-is with dual check valves to keep fuel vapor out of the intercooler. It's probably not a problem... but...

[Delorean Industries]

Very simple to set up if you can control inputs/outputs with your ecu. Valve will set you back 25 bucks along with a 50 dollar new or .30 set junk yard connector.

[FABombjoy]

I'm just fighting time at the moment. I do have lots of provisions for I/O ready to plug in. Could be an October addition though!

[opethmike]

Oh Luke, always with the orifices.

[FABombjoy]

Hmm... yes... quite gaseous they are

[FABombjoy]

Testing results

The vapor canister purge SIGNAL line - the one that connects to the throttle edge tap - seems to have a check valve in it already. It held pressure to at least 10psi which is good enough for me.

The actual purge line is not boost safe. It will leak down under any pressure. Increasing pressure on the signal line does not help the purge valve hold.

This means is that the vapor canister is a (controlled) boost leak source for BAE/Island cars.