Boost bleed/purge line

[Sekred]

I have had the bleed line block with a check valve for nearly 2 years now with no problems. I am not really sure there is much to gain simply because the volume of boost bleed off is so small.
Thanks for telling us how the system actually works Ryephile, I would have never guessed the Tee acted like a venturi.

 

[jayrod1980]

How do you know there's a boost leak?


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[MOFiST]

If you put a boost gauge on the output of the IC cold pipe EVAP return nipple you will only see boost.
I was going to use the location for my boost gauge but there must be a check valve there because no vacuum was seen.

 

[jayrod1980]

Now that I have my Cobb ATR software, I can see this ECU doesn't even have an active P0441 code, so there isn't any risk of posting a CEL.

[MENTION=2065]jayrod1980[/MENTION], here's your fix for going to an aftermarket intake, just plug the boost leak line and retain the actual Evap purge line going to the intake tube.

The issue isn't that there's two lines, but rather you go into limp mode with aftermarket intakes because a Check valve is necessary. I have a MAP intake I've been wanting to use, but the 2016 owners that just capped off the "boost bleed" line eventually threw a code and limp mode because there is no check valve on the aftermarket intakes. MAP finally rigged a set of replacement vacuum lines with a t fitting and check valve to use with their intake, as well as Mishimoto.

What I would like to know is how blocking the line without the valve, the line going to the charge pipe, effects throttle response. I also have the Tune+ spec Turbosmart wastegate actuator which prevents surging, however I feel partial throttle is a pain at times... It's typically power on, or vacuum and not the greatest control or modulation at partial throttle.

For example, with partial throttle, the turbo will often quickly spool to 14-22psi but briefly, like a rubber band effect. When I give it WOT I get full boost, 22-25psi all the way until I shift. Does that make sense?

 

[Ryephile]

The issue isn't that there's two lines, but rather you go into limp mode with aftermarket intakes because a Check valve is necessary. I have a MAP intake I've been wanting to use, but the 2016 owners that just capped off the "boost bleed" line eventually threw a code and limp mode because there is no check valve on the aftermarket intakes. MAP finally rigged a set of replacement vacuum lines with a t fitting and check valve to use with their intake, as well as Mishimoto.

What I would like to know is how blocking the line without the valve, the line going to the charge pipe, effects throttle response. I also have the Tune+ spec Turbosmart wastegate actuator which prevents surging, however I feel partial throttle is a pain at times... It's typically power on, or vacuum and not the greatest control or modulation at partial throttle.

For example, with partial throttle, the turbo will often quickly spool to 14-22psi but briefly, like a rubber band effect. When I give it WOT I get full boost, 22-25psi all the way until I shift. Does that make sense?

The item molded into the 2016 intake tube is not just a check valve, it's also a Venturi-T. It works the same way an aerosol can does; blow boost pressure across the evap line and it sucks out the vapors. The irrational part is the vapors are already under pressure (1.5 PSI or thereabouts), so they don't need to be sucked out. On top of that there's a slight vacuum in the compressor inlet tube, further increasing the pressure delta with the evap vapors. The Venturi-T is simply redundant on the rarely used redundant side of the evap lines.

If you're removing or adding check valves then you're doing it wrong and you'll either cause an intake leak or an emissions plug. If you're affecting engine performance negatively then the evap lines have been modified incorrectly, full stop. There are two ways Evap vapors are purged; the normally used path via the throttle body tube, and via the turbo compressor inlet tube. The rationale for this is so the purge solenoid can actuate and allow vapor purging during both vacuum and boost engine operations.

If you're confused, go look at the evap lines on a Focus ST; they're quite different in philosophy, and IMO much more rational. I also suggest going back a few pages to look very closely at my write-up. I have a 2016 and when correctly done, there are no negative consequences.

 

[jayrod1980]

I'm sorry but you aren't correct. Take the "Venturi" part and blow into it. There's a check valve in that fitting. People have actually removed it and epoxied it to their Cobb etc intakes to get rid of that code. It may function as you say but the problem is the check valve. Capping it off at the check valve will throw a code. Capping the other hose will not affect anything. That's why I asked about the benefit of only using the line with the valve.


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[Ryephile]

Easy there on the accusations; you wouldn't be saying that if you read my write-up and took the time to understand what's being shown in the pictures. I'm trying to help you understand the system.

What P-numbers are these codes being posted? I don't see a mention of anything specific in the 2016 intake thread, just some broad misunderstanding of how the evap system works.

 

[skidro87]

So modifying the older version does anything? Interested to try this on my 2015

 

[Ryephile]

So modifying the older version does anything? Interested to try this on my 2015

The systems appear to be schematically identical, however the shape of the lines and location of components is different. The gains are a possibly smoother part-throttle response and definitely a few CFM worth of improved turbo compressor pressure ratio. Whether any of that is measurable beyond noise is up for grabs.

 

[jayrod1980]

Ryephile, read some of the testimonies in the 2016 intake thread, there absolutely is a check valve in that T fitting. Whether there's a Venturi effect or not I'm not arguing. What I'm saying is that if you don't utilize a check valve you get a check engine light. The other line has been successfully capped off on 2016s already as you say.


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[Ryephile]

Ryephile, read some of the testimonies in the 2016 intake thread, there absolutely is a check valve in that T fitting. Whether there's a Venturi effect or not I'm not arguing. What I'm saying is that if you don't utilize a check valve you get a check engine light. The other line has been successfully capped off on 2016s already as you say.


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I think I see where the miscommunication is. You're focusing on the evap line, I'm focusing on the boost leak line. I'm not making any modification to the evap line. To extend, if you want to run a 2014-2015 intake tube on your car, you'll need to source another check valve to take the place of the one associated with the evap fitting in the 2016 intake tube.

Remember, I clearly stated that if you remove any of the stock check valves then you're doing it wrong. At no time did I recommend or advocate removing the evap check valves.

IMG_7973.jpg by Ryephile, on Flickr

IMG_7976.jpg by Ryephile, on Flickr

 

[Ryephile]

How do you know there's a boost leak?


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The line from the cold-side boost tube fitting to the venturi-T with the restrictor orifice is by definition a boost leak.

 

[skidro87]

So I will try this tomorrow, I have looked at your previous posts about the boost leak line and I believe it shouldn't be too hard to install

 

[OffTheWall503]

I think I see where the miscommunication is. You're focusing on the evap line, I'm focusing on the boost leak line. I'm not making any modification to the evap line. To extend, if you want to run a 2014-2015 intake tube on your car, you'll need to source another check valve to take the place of the one associated with the evap fitting in the 2016 intake tube.

Remember, I clearly stated that if you remove any of the stock check valves then you're doing it wrong. At no time did I recommend or advocate removing the evap check valves.

IMG_7973.jpg by Ryephile, on Flickr

IMG_7976.jpg by Ryephile, on Flickr

I want to try this on my 2016. Thanks for clarifying it.

 

[Ryephile]

[MENTION=4498]OffTheWall503[/MENTION] I hope you don't mind but I'm going to paste my reply to your PM right here in case others have the same question.

The question was what size caps did I use. Unfortunately I forgot to measure, I just grabbed whatever fit the nipples of the boost leak line from my vacuum cap kit. It's a Dorman 47388. Based on what's missing it's either a 5/16 or 3/8". FYI you only need a worm clamp for the boost tube side, the intake tube side is always under vacuum so a snug fitting cap is acceptable.

 

[skidro87]

In the middle of doing this now. The boost line and Evap line are routed together so that is maybe why the 2016 Intakes have 2 lines on the intake tube

 

[skidro87]

I am going to plug the cold side pipe and leave the rest of the lines there, and keep the hose connected into the intake

 

[Ryephile]

I am going to plug the cold side pipe and leave the rest of the lines there, and keep the hose connected into the intake

I don't recommend that. Please take a close look at my pictures. If you leave the boost leak line open like that you'll have an intake leak and also vent evap vapors to atmosphere.

This is a very simple change. Remove one line as shown above in the picture, and cap both nipples where that line was.

 

[skidro87]

There isn't a Venturi in the 2015 or I might be blind. They are all connected as one line with heat shrink hoses. All the lines also have check valves so I think it's fine

 

[Ryephile]

There isn't a Venturi in the 2015 or I might be blind. They are all connected as one line with heat shrink hoses. All the lines also have check valves so I think it's fine

Ok, didn't know you were doing it on a 2015. There's still a venturi, it's just not attached to the intake tube like the 2016. Someone with a '14 or '15 will have to post pictures of how it's done. If you can follow the lines it doesn't take too much effort to figure out what line goes where and which does what. From the evap solenoid, as long as you end up with a Y fitting and lines going to both the throttle body fitting and the intake tube fitting, both with correctly oriented check valves, you'll be good to go.