# AEB Vacuum/PCV System Diagram



## T_Dub (Nov 9, 2006)

This is something I have been unable to find. I am trying to figure out what to buy, since I am starting out from a bare block/head. I plan to fab a water pipe, and I think I have the water system figured out. But I really can't figure out for sure what I need to get to make the vacuum/PCV system work.

For background I'm going to build the engine as barebones as possible but still streetable with a Frankenturbo F21. Going in my MK1 GTI.


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## Chickenman35 (Jul 28, 2006)

The AEB has a pretty simple PCV system and it's much more effective and reliable than later systems. Here's the PCV routing.

Note: Hockey Puck attaches at #14. #10 goes back to Intake manifold. Note that AEB does not use the troublesome " Suction Jet Y-Pipe " as later models do. Early AEB's also do not have a hose attached to the Valve Cover. Not needed.



















Vacuum lines to follow.


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## Chickenman35 (Jul 28, 2006)

AEB also has a pretty simple Vacuum hose system. Uses 1 way check valves only. Edit: Parts #25, #26 and #27 are connections to Brake Booster. #26 is just a plastic coupling. May not be needed for your conversion.

#1 through #20 are all part of Charcoal Canister Purge System. Don't have one? You can eliminate a lot of hoses. #21 goes to Cruise Control Diaphragm and Vacuum Reservoir ( Ball ) for vacuum operated devices such as Climate Control Vacuum motors. Don't have those? More hoses to eliminate. Just cap off the fittings or use for Boost gauge connection. . 

As bare bones, you should have one small vacuum line at front of Intake manifold that goes direct to DV. ( No N249 valve on AEB's ) and one small nipple at the rear topside of Intake Manifold for the FPR ( Not shown ). Pretty simple.

Click on link for zoomable Image with Part numbers. Edit: Jim Ellis Audi/VW has a full online parts catalog with all Part numbers. Very handy and arguably easier to use than Ekta....

http://www.jimellisaudiparts.com/showAssembly.aspx?ukey_assembly=752193


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## T_Dub (Nov 9, 2006)

Thanks a lot! So I would assume I need a check valve in the brake booster line to avoid getting boost pressure in there? And then just the line to the DV and FPR? And I guess those two wouldn't have check valves. There isn't a line to the intake pipe at all?

Is there no N75 valve on an AEB or is that in a different hose?

Two questions on the PCV system. The hockey puck is what exactly? The PCV valve? Forgive me but I've heard it referenced a lot but I'm not 100% sure. And what's #6? Just a reducer?


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## Chickenman35 (Jul 28, 2006)

T_Dub said:


> Thanks a lot! So I would assume I need a check valve in the brake booster line to avoid getting boost pressure in there? And then just the line to the DV and FPR? And I guess those two wouldn't have check valves. There isn't a line to the intake pipe at all?
> 
> Is there no N75 valve on an AEB or is that in a different hose?
> 
> Two questions on the PCV system. The hockey puck is what exactly? The PCV valve? Forgive me but I've heard it referenced a lot but I'm not 100% sure. And what's #6? Just a reducer?


Yes, the brake booster needs a check valve. Use the correct VW/Audi 1.8T Brake Booster check valve. It's different from a normally aspirated check valve.

DV and FPR do not have check valves. Not sure what you mean by " There isn't a line to the Intake pipe at all " ???

Yes the AEB has an N75 valve just like every other 1.8T. Not in those pictures cause it's in a different parts illustration section. 

The Hockey puck is a kind of one way flow valve that allows venting of the crank case under boost, It uses a Venturi effect that pulls fumes through the TIP. The PCV valve is closed under boost and only sucks fumes when engine is under vacuum. The AEB has a decent PCV system and I would advise running in stock form. You can run a catch can, just place i in between the PCV valve and Hockey Puck and make sure it is a " closed " or " recirculating " style. IE. Do not use a catch can with a vented inlet filter. Not needed and can cause issues if you use a MAF.

#6 is your N80 valve or Vacuum Canister Purge valve. It's a pulse valve controlled by ECU to purge Fuel Tank Vapors. If you don't have a Charcoal Canister system, you don't need the associated hoses etc. Note: The N80 valve must be plugged in electrically or resistored for Fuel Trims to work. If you just unplug it, ECU will not adjust Fuel Trims. Of course if you're using a stand alone ECU, that doesn't matter.


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## T_Dub (Nov 9, 2006)

Sorry I meant number 6 in the breather diagram. I guess thats the PCV? So the #10 hose is how the intake sucks through the PCV, then when the intake is under boost PCV closes and the hockey puck pulls crankcase fumes instead? Makes sense.

I think I figured out the N75 stuff after, pretty straight forward, just a boost control valve.


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## Chickenman35 (Jul 28, 2006)

T_Dub said:


> Sorry I meant number 6 in the breather diagram. I guess thats the PCV? So the #10 hose is how the intake sucks through the PCV, then when the intake is under boost PCV closes and the hockey puck pulls crankcase fumes instead? Makes sense.
> 
> I think I figured out the N75 stuff after, pretty straight forward, just a boost control valve.


Yes, #6 in breather diaphragm is PCV valve.

#10 hose connects to Intake and operates as you surmised.


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## T_Dub (Nov 9, 2006)

Thanks a lot. Now I have everything I need.


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## 1.8t G (Oct 28, 2014)

Wouldn't this system not work with pressurized intake Cuz once it's under boost the Pcv will close creating pressure in the crankase and it won't have a Pcv valve to create suction? 
Just trying to understand I seem to keep getting more and more confused. I'm redoing my Pcv system


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## groggory (Apr 21, 2003)

1.8t G said:


> Wouldn't this system not work with pressurized intake Cuz once it's under boost the Pcv will close creating pressure in the crankase and it won't have a Pcv valve to create suction?
> Just trying to understand I seem to keep getting more and more confused. I'm redoing my Pcv system


Under boost, the crankcase pressure will flow from #2 to #14.


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## Chickenman35 (Jul 28, 2006)

1.8t G said:


> Wouldn't this system not work with pressurized intake Cuz once it's under boost the Pcv will close creating pressure in the crankase and it won't have a Pcv valve to create suction?
> Just trying to understand I seem to keep getting more and more confused. I'm redoing my Pcv system


Ahh...so you found my AEB diagrams. I knew I had been experiencing Deja-Vu recently LOL. 

As explained by Groggery.

1: Under Boost conditions: The Hockey Puck provides suction via a *Venturi effect*. Under boost the PCV Valve closes shut and crankcase venting airflow goes from #1 ( block breather/ oil separator ), Plastic " Hose " #2, through Tee #5, through Metal Pipe #9 and Hose #14 and then through the Hockey Puck wich connects to hose #14 on one end and the Turbo Inlet Pipe on the other. Unfortunately the first diagram does not show the Hockey Puck nor the TIP, but they connect directly through joining hose #14


2: Under non-boost driving, crankcase venting is through breather#1, Plastic " Hose " #2, Tee #5 and then through the OPEN PCV valve #6 and finally into the Intake manifold ( not shown ) by connecting hose #10. There is no backwards airflow from the Hockey puck, as it is also a 1 way check valve and closes shut under non-boost Mode.

You don't need to use the OEM Audi made Plastic " Hose " #2 nor the Metal Pipe #9. Obviously you can just use regular emissions hosing for this. Somewhere along the routing of Pipe/Hose #9, install your Catch can. It must be a CLOSED Catch Can with no VTA breather attached to it. A Breather attached to the Catch Can would render the whole PCV system useless. 

There you go. A simple, effective PCV system that will work properly, cheap to build and won't break all the time. The weakest point in the AEB system is that stoopid Plastic Hose #2 . That of corse can be replaced by a simple section of hose off of yor breather block.


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## Chickenman35 (Jul 28, 2006)

This should be in the FAQ :thumbup:


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## ExtremeVR6 (Sep 6, 2001)

This here is amazing information! Thanks for that!


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## ExtremeVR6 (Sep 6, 2001)

What is the valve at the end of the crankcase vent piping... The one that connects into the turbo intake pipe?


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## groggory (Apr 21, 2003)

Created a new category 'Vacuum system' to the FAQ and added this thread to that.


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## Chickenman35 (Jul 28, 2006)

ExtremeVR6 said:


> What is the valve at the end of the crankcase vent piping... The one that connects into the turbo intake pipe?


It's a another type of " PCV valve " as explained above, commonly referred to as the " Hockey Puck". It vents the crankcase when under Boost conditions as explained in previous posts.


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## zapmeister (Aug 13, 2011)

Hi. I dont mean to jack thread. My 98 aeb euro a4 has line #27 connected to line #21. Just wanna make sure that thats how its suppose to be. If not where do they lead to? I biught this car from someone else and just wanna make sure everything in the right place. 




Chickenman35 said:


> AEB also has a pretty simple Vacuum hose system. Uses 1 way check valves only. Edit: Parts #25, #26 and #27 are connections to Brake Booster. #26 is just a plastic coupling. May not be needed for your conversion.
> 
> #1 through #20 are all part of Charcoal Canister Purge System. Don't have one? You can eliminate a lot of hoses. #21 goes to Cruise Control Diaphragm and Vacuum Reservoir ( Ball ) for vacuum operated devices such as Climate Control Vacuum motors. Don't have those? More hoses to eliminate. Just cap off the fittings or use for Boost gauge connection. .
> 
> ...


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