Boost bleed/purge line

[westcoaST]

Actually these clamps are called Oetiker clamps. A special pair of oetiker pliers are used to crimp the clamps down or to cut the clamps off. I use them for vacuum or pressure lines in my mustang.

 

[hotrodst7]

so i looked into this with my ford resources and the tube assembly you are modifying is considered part of the evap system, but im having trouble finding a flow chat. if i find more info ill be sure to share it.

 

[razorlab]

It looks like that *could* be the Boost Solenoid bleed hose. Basically on a 3 port boost solenoid, like the Fiesta ST has, the 3rd port is used to bleed the air off the 3rd port of the solenoid while the solenoid is cycling. If that is it, I wouldn't cap it.

I believe the Fiesta ST uses the Pierburg boost solenoid. VW uses these as well, as does the Focus ST.

 

[hotrodst7]

ok i found a crude flow chart for 1.6 ecoboost. it appears that the tube you guys are modifying supplies the vaccum for the evap system. sorry to rain on your parade.

 

[hotrodst7]

ive also just discovered that that whole tube assembly is called the (Evaporative Emission Canister Purge Valve) the picture that shows the tubes in blue with the 2 arrows pointing at the evap purge valve is actually all one part. i'll try and get a part number monday.

 

[MOFiST]

I can see what your saying however when the manifold pressure is in vacuum then the evap system is still going to be able to vent through the throttle body charge pipe I would think. It's only when the system is in boost it will not be able to vent. Can anyone see this as a major issue? I can easily put mine back and may do.

 

[Sekred]

I did mention in my initial post that it is part of the Evap system but there are two separate sections to the system. I think they may combine if one of the check valves fails. So let me explain and look at the diagram to get a understanding of how I think the system works. Check valve one is connected to the intake manifold and only allows vacuum into the Evap line. I think check valve two is a fail safe. I pressurised and vacuum tested check valve two and found no leakage but I only checked one side of it, the purge/bleed side. What I think happens is that if check valve one fails and allows boost pressure to enter the Evap line, check valve two opens and allows boost pressure to vent into the intake tube or intercooler pipe. If boost pressure was allowed to pressurise the Evap line and then enter the fuel tank it would be a extremely serious problem.

What still makes no real sense to me is why boost pressure is allowed to constantly bleed back to the intake tube in a closed loop, this has nothing to do with the Evap system during normal operation.

One last thing (maybe). Anyone that has block off both ends of the purge/bleed line NEEDS (MUST DO THIS) to reconnect the intake tube end to allow boost pressure to escape from the Evap line if check valve one happens to fail.

 

[MOFiST]

I think from your explanation and the picture above I'd be better to cap the intercooler outlet pipe and leave the other parts connected. The vacuum of the intake would allow the system to vent. Like you have said why would you want boost pressure entering the evap system?

 

[Sekred]

I think from your explanation and the picture above I'd be better to cap the intercooler outlet pipe and leave the other parts connected. The vacuum of the intake would allow the system to vent. Why would you want boost pressure entering the evap system?

That should work ok, somewhere for boost to go if the Evap line became pressurised.

 

[hotrodst7]

I think from your explanation and the picture above I'd be better to cap the intercooler outlet pipe and leave the other parts connected. The vacuum of the intake would allow the system to vent. Like you have said why would you want boost pressure entering the evap system?

I agree that would prolly be the safest way to do it, that way you have a constant vacuum source for evap. why they even put a line to the charge pipe i dont know, but i can see why the used the intake to pull vacuum at low rpm and then pulling through the turbo inlet pipe at higher rpm, so you always have a good vacuum source.

 

[STooge]

Has anyone removed the line from the intercooler to the intake tube? Is there any chance there are check valves in the actual ends themselves? I noticed in your first post Sek, that the line ends have red/orange fittings on them, mine are green but look the same.

If you have removed them and there are NO check valves of any sort then I can see why this is a head scratcher for sure.

Is it possible that this is a way to combat the "shift point" I know on some older cars if the BOV vented to atmosphere the car would fall on its face, whereas with the BOV recirculated back in to the intake it would help fight that lack of air flow. I realize that this is not on the recirc valve but it would be some sort scavenging for this reason...maybe...maybe not...?

 

[MOFiST]

I have got a silicone cap on the bleed off nipple coming from the FMIC to TB tube. I have blocked off the connecting line to the EVAP with a metal plug. I then did a boost leak test to check it was tight. I've felt no ill effect in a few WOT runs I've done but cannot log as still waiting on an OBD2 dongle.

The reason for this line I was thinking it's like an Eddie to keep the boost curve smoother. Or it's emissions based crap to pass a test. One or the other. I may do some WOT logging with and without for fun to see if there is any differences in top end boost.

 

[Sekred]

Has anyone removed the line from the intercooler to the intake tube? Is there any chance there are check valves in the actual ends themselves? I noticed in your first post Sek, that the line ends have red/orange fittings on them, mine are green but look the same.

If you have removed them and there are NO check valves of any sort then I can see why this is a head scratcher for sure.

Is it possible that this is a way to combat the "shift point" I know on some older cars if the BOV vented to atmosphere the car would fall on its face, whereas with the BOV recirculated back in to the intake it would help fight that lack of air flow. I realize that this is not on the recirc valve but it would be some sort scavenging for this reason...maybe...maybe not...?

There are no check valves fitted at either end of the tube.

 

[Ryephile]

I know this is doing a necro-thread but this appears to be the most relevant thread I found. After reading through it, it appears you guys were really close to figuring it out, but didn't quite make it.

What the FiST uses is a dual circuit Evaporative Emission purge setup, designed to A) either purge charcoal canister vapor pressures during intake manifold vacuum operation, or B) use turbo boost pressure into a venturi tee fitting to allow evap purge during positive intake manifold pressure scenarios. For those of you that dabble in other brands, this is identical to the problematic evap system on the 2012-2014 Fiat 500 Abarth engines. Me and a few other guys in the Abarth community developed a DIY fix that prioritizes engine drivability and peak power over flawless evap purging, but not compromising the evap system in a manner that causes charcoal canister problems with undue high vapor pressure. There is also a vendor that developed a much more complicated (read: $$$) setup that closes the boost leak line above a pre-set boost pressure; this prioritizes peak power with little risk of a CEL, but doesn't improve the part-throttle drivability that plagues the Abarth.

Just for perspective, in the Abarth setup, it was found with several different dynos that plugging the boost leak and re-routing the convoluted evap lines gained a consistent 5wHP due to the improved turbo compressor pressure ratio while maintaining rational evap line pressures, usually under 1.5 psi. It did occasionally cause a P0441 code over time, but not in all cars, likely due to individual locations, weather, and fuel type in the tank. The boost leak plug also improved part throttle boost response, conducted as back-to-back blind test drives where people weren't told what was different.


Now, I have yet to do any comparable measurements on the FiST engine, but the theory and execution is identical. This is just for your amusement; I'm not advocating a solid "fix" at this time. Here are some pictures of my initial mock-up I whipped up today. Keep in mind I have a 2016 model, and the evap lines are slightly different. The venturi tee is now in the turbo inlet tube instead of within the maze of EPDM lines.

Obligatory engine bay shot for 2016:

IMG_7918.jpg by Ryephile, on Flickr

The new airbox exit / turbo compressor inlet tube:

IMG_7971.jpg by Ryephile, on Flickr

Gory details: Left unclipped [green tab] connector is the boost leak line. In the middle is the actual evap purge line. To the right you can see the evap purge solenoid.

IMG_7972.jpg by Ryephile, on Flickr


Removed boost leak line, put a vacuum cap on the appropriate nipple of the venturi tee on the intake tube, and also showing the cap and clamp I put on the cold-side charge pipe

IMG_7973.jpg by Ryephile, on Flickr

Picture of the cold side charge pipe with cap and clamp installed where the boost leak line was

IMG_7976.jpg by Ryephile, on Flickr


If anyone else wants to try this, keep in mind you *may* trip a P0441 code, I haven't been able to do any datalogging yet. If you do any datalogging, log the evap vapor pressure and commanded purge along with fuel level. Bonus points to anyone that does a dyno or virtual dyno back-to-back!

Cheers,
Ryan

 

[Ryephile]

Does anyone have any questions on this? I thought more people would jump at this.

FWIW, I've put about 200 miles on the car with the boost leak capped and no CEL.


The secondary benefit is it means it might be feasible to retrofit 2014-2015 intake tubes onto 2016's.

 

[MOFiST]

Does anyone have any questions on this? I thought more people would jump at this.

FWIW, I've put about 200 miles on the car with the boost leak capped and no CEL.


The secondary benefit is it means it might be feasible to retrofit 2014-2015 intake tubes onto 2016's.

I've put my EVAP setup back to stock.
I wanted a stock setup before I tuned the car and never returned it.
I'd interested to try this again as now I have a boost gauge, mechanical BOV and tune fitted and I'm familiar with how the car performs.
The 2016 inlet makes it easier to block the return venturi boost line but I'm gonna stick with my silicon intake tube.
The other thing is the EVAP tube pipe maze is likely specific for the 2016 I'd has it a guess.
Any logs or notice any performance bump?

 

[RAAMaudio]

Watching to see if any more mods than what has been done on the 2014 and 2015, hope so, I always like to do mods to make things better

 

[Ryephile]

...Just for perspective, in the Abarth setup, it was found with several different dynos that plugging the boost leak and re-routing the convoluted evap lines gained a consistent 5wHP due to the improved turbo compressor pressure ratio while maintaining rational evap line pressures, usually under 1.5 psi. It did occasionally cause a P0441 code over time, but not in all cars, likely due to individual locations, weather, and fuel type in the tank. The boost leak plug also improved part throttle boost response, conducted as back-to-back blind test drives where people weren't told what was different....

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.

 

[Bluedrank]

So is this a problem that only affects 2016 models or is it platform wide? Has anyone else done this and datalogged the results and what are your impressions?

What is the drawback / long term consequences by doing something like this? I'm always concerned when removing something that the engineers designed to function a specific way from the factory.

 

[Ryephile]

Platform wide. They decided to integrate the venturi-T in the 2016's intake tube instead of a rats-nest of tubing the 2014-15's have. They all have the boost leak though. This is why I'm so surprised almost nobody seems to care.

The only drawback is if the Evap vapor pressure suddenly rises during continuous sustained boost (that means no gear changes), it will take slightly longer to purge the vapors. The only way for this to realistically happen would be to refuel the car in-motion during the middle of a 6th-gear-only Texas-Mile run on the hottest day of the year. The instant you lift the throttle the vapors would purge at the normal rate versus the slightly less than normal rate. Since nobody is refuelling while they're driving, this isn't a realistic scenario, but it is one that Ford chose to be concerned with. Fiat did the same shenanigans for the 2012-2014 500 Abarth, but then dropped it for the 2015+ by going to a more conventional turbo engine evap purge line solution and OBDII monitoring.

Blocking the boost leak doesn't block the evap purge, it eliminates the venturi-T from accelerating the evap purging during on-boost operation. On top of Ford OBDII monitoring not even watching this, it's not a realistic concern.