Forced Induction Bypass valve reference

JD1964 · Jun 1, 2025

On my 302 with Vortech V3, im cleaning up and replacing some of the vacuum lines.

Im still running the complete EVAP system and its fully functional as far as I can tell. I want to keep the system functional because I like walking into my garage and not smelling gas fumes.

As for the vacuum/boost reference line to my bypass valve in the intake tube, is it ok to T that into the vacuum line that runs down to the charcoal canister? The benefit for using that particular line is that it already passes in close proximity to the bypass valve. I just want to make sure there wont be any conflict in proper operation of the two systems.

Thanks, John

nicholase · Jun 1, 2025

Don't use that one. That's the canister purge pathway. While it does have vacuum on it (at most times) it's a switched source. Meaning when the can-p solenoid opens fuel vapors pass through that line as it pulls them into the intake. During that process that line loses vacuum because it's flowing fuel vapors.

Just run all your boost stuff to the open port on the firewall vacuum tree. T your guage and any other boost related functions to that.

JD1964 · Jun 1, 2025

Im curious here because for one, the purge valve would be downstream of my bypass T. So, vacuum or boost reference will always be available to the bypass valve regardless of the purge valve being opened or closed. Also generally, when the purge valve opens to pull vapors back into the intake, doesnt that essentially create a vacuum leak (small somewhat) that the entire plenum is subjected to? Meaning that, all lines connected to the plenum (which includes the vacuum T on the firewall) will recognize the same change that the vapor line sees. Correct or not?

nicholase · Jun 1, 2025

I'm not sure i follow your question. It's bad practice to combine multiple vacuum systems. Here's a video that helps explain some of it. Start at the 17:37 mark. There's good info there.

Noobz347 · Jun 1, 2025

JD1964 said:
Also generally, when the purge valve opens to pull vapors back into the intake, doesnt that essentially create a vacuum leak (small somewhat) that the entire plenum is subjected to? Meaning that, all lines connected to the plenum (which includes the vacuum T on the firewall) will recognize the same change that the vapor line sees. Correct or not?

You are neglecting the relationship between pressure and volume.

It's easy to tap into a line and destroy normal airflow by "relieving" pressure through an alternate path that was [not] intended to carry more volume than necessary for [a] particular device to operate.

Your question about going back to the intake:

Look at [all] of the available air volume in the intake versus the volume available in an enclosed 1/4" vacuum line that is X number of inches away from the vacuum source.

The mass of air in the intake ensure that there is enough volume for each vacuum accessory plus a few more.

JD1964 · Jun 1, 2025

Ok, my brain (oldish) gets it now. Thanks people

Forced Induction Bypass valve reference

JD1964

there is enough sticking out to grab on to

nicholase

I lubed and pushed, until it was all the way in

JD1964

there is enough sticking out to grab on to

nicholase

I lubed and pushed, until it was all the way in

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

JD1964

there is enough sticking out to grab on to

Similar threads

Forced Induction Bypass valve reference

JD1964

there is enough sticking out to grab on to

nicholase

I lubed and pushed, until it was all the way in

JD1964

there is enough sticking out to grab on to

nicholase

I lubed and pushed, until it was all the way in

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

JD1964

there is enough sticking out to grab on to

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