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View Full Version : Why does the Brake Booster Line have a nipple/cap on it? (AEB)



b5a4erik
03-16-2016, 05:49 PM
Title asks it all.

Wrath And Tears
03-16-2016, 05:53 PM
I assume you are asking about the check valve with the nipple and cap? It is for your boost gauge. But for reals I don't actually know why it's a special check valve.

b5a4erik
03-16-2016, 05:59 PM
I assume you are asking about the check valve with the nipple and cap? It is for your boost gauge. But for reals I don't actually know why it's a special check valve.

Whoa, never even thought of hooking my gauge up to that. Word, thanks man.

walky_talky20
03-16-2016, 05:59 PM
You question the brilliant, faultless mid 90's Audi engineers!?

How dare you, sir. How DARE you.

Wrath And Tears
03-16-2016, 06:03 PM
I have often wondered if you could replace the special valve with a normal check valve. I would assume so but like walky said, people in white coats got paid a lot of money to design our cars.

b5a4erik
03-16-2016, 06:05 PM
Haha I know, I know!

Without questions, there are no answers...

Which leads me to another question ha: Brake booster line better than DV line (for a boost gauge)?

BB is closer which means I could shorten the line which means better response?

b5a4erik
03-16-2016, 06:08 PM
I have often wondered if you could replace the special valve with a normal check valve. I would assume so but like walky said, people in white coats got paid a lot of money to design our cars.

True. I've been questioning (hopefully rightfully / respectfully so) a lot of the stuff in my engine bay lately... throttle body orientation, throttle body hose design, and now this seemingly strange check valve... all so complex, interesting and quite curious.

b5a4erik
03-16-2016, 06:09 PM
and hey, it's atleast good to know that I've got 2 guys, one mechanic and one who's not a mechanic, both of which I should not listen to, responding to this thread ;)

Turbo_B5
03-16-2016, 06:10 PM
I have mine at the FPR. less room to travel=a faster response perhaps?

b5a4erik
03-16-2016, 06:12 PM
I have mine at the FPR. less room to travel=a faster response perhaps?

I was thinking the same thing King, and also, sweet new Prof. Pic. [:D]

walky_talky20
03-16-2016, 06:22 PM
people in white coats got paid a lot of money to design our cars.

And here we come and just rip all that crap out. All their hard work!

Wrath And Tears
03-16-2016, 06:28 PM
And here we come and just rip all that crap out. All their hard work!

Yup, I've been thinking about ripping some of that stuff out.

As far as boost gauge response goes, I have use the following:
1. DV line
2. FPR line
3. Brake check valve nipple
I really didn't notice any difference in response time for the boost gauge. I also have a fuel filter from a 1970 Bug tied into my boost gauge to help with buzzing in the gauge. I didn't notice a difference in response before or after adding the filter.

b5a4erik
03-16-2016, 06:54 PM
And here we come and just rip all that crap out. All their hard work!


Yup, I've been thinking about ripping some of that stuff out.

As far as boost gauge response goes, I have use the following:
1. DV line
2. FPR line
3. Brake check valve nipple
I really didn't notice any difference in response time for the boost gauge. I also have a fuel filter from a 1970 Bug tied into my boost gauge to help with buzzing in the gauge. I didn't notice a difference in response before or after adding the filter.

Evolution, my friends.

Word to the Boost Guage response time. Thinking of moving my line to the BB for the sake of cleanliness.

Now my gauge was reading around -16 on startup at the DV, and now it reads -18 at startup at the BB... what might this mean?

MetalMan
03-16-2016, 09:02 PM
On my AEB, that cap on the check valve broke... so I removed the tee at the FPR, put a straight hose between FPR and IM, and hooked the boost gauge line to the nipple. It's like it was meant to be.

b5a4erik
03-16-2016, 09:21 PM
On my AEB, that cap on the check valve broke... so I removed the tee at the FPR, put a straight hose between FPR and IM, and hooked the boost gauge line to the nipple. It's like it was meant to be.

Same thing happened to me man, cap broke, and now this new knowledge of running the boost guage line to the BB, it's a bit strange... but I give it a [up].

- - - Updated - - -

The prime orientation of it that is.

mysman
03-18-2016, 06:41 AM
http://www.audizine.com/forum/showthread.php/621714-Brake-Booster-Check-Valve

Davdraco1
03-18-2016, 07:20 AM
I'm awm and run mine off FPR line

b5a4erik
03-19-2016, 08:14 PM
Word. Thanks for the replies guys.

tar
03-19-2016, 08:52 PM
Yup, I've been thinking about ripping some of that stuff out.

As far as boost gauge response goes, I have use the following:
1. DV line
2. FPR line
3. Brake check valve nipple
I really didn't notice any difference in response time for the boost gauge. I also have a fuel filter from a 1970 Bug tied into my boost gauge to help with buzzing in the gauge. I didn't notice a difference in response before or after adding the filter.

Fun fact we use those "bug" filters at work to aspirate bugs to use in science experiments. Same part number always thought it was weird.

A1 A2 German
03-19-2016, 10:12 PM
Here's the conversion:

Take the entire oem assembly and trash it, and:

http://i41.photobucket.com/albums/e259/Blakelikesfood333/Audi%20Final%20Chapter%20Build/AudiTurboBuild014_zps5334ba4e.jpg (http://s41.photobucket.com/user/Blakelikesfood333/media/Audi%20Final%20Chapter%20Build/AudiTurboBuild014_zps5334ba4e.jpg.html)


The left of this picture is for the intake manifold, the large grommet right of center is through the false tray, to a double nippled GM check valve, directly to to brake booster to left.

Both nipples are now located inside the tray, 1 for your boost controller, 1 for boost gauge, now you've also hidden everything under the raintray and prevented more hoses from going in the engine bay.

The GM check valve part # shouldn't be hard to find online (it's originally black and bright yellow) or find my brake booster line conversion thread. The hose is ~1' of ~8AN nylon braided hose found at BAP (now Advanced Autoparts).

b5a4erik
03-21-2016, 06:55 PM
^ Cool. Much cleaner. Performance better as well? The BB hose is another one of those confusingly shaped hoses, while this one seems fairly straight.

A1 A2 German
03-21-2016, 07:16 PM
It's the same.

I believe the oem line as is passes through the false tray is down to the left. You could uses a slightly longer hose and bend it towards the oem grommet and have it bend back up towards the bb. I left the oem grommet in place (so no bare hole in the tray). Then simply drilled a dead center hole (cleanly) and inserted the large grommet (as seen in my picture) then slide the hose through. This was done as the bb barb and intake manifold barb basically line up 100% perfect, however there's no hole otherwise unless you drill or go through the oem grommet with is far off center. I don't even use hose clamps or zipties, it's all press barb (have a press barb on my IE Intake Msnifold) fits tight and secure. If using the oem manifold which has a simple barb, you may want to secure it (hoseclamp or other) so doesn't blow off. It otherwise is very clean and looks oem+.

vwblackb5
03-21-2016, 07:31 PM
I tee'd off the IM for my Adjustable FPR and Boost Gauge for my AEB.

http://i95.photobucket.com/albums/l132/vwblackb5/IMG00075-20110403-1349_zps641ef779.jpg

b5a4erik
03-22-2016, 07:48 PM
A1 A2 German: good reply man thanks for the extensive info.

vwblackb5: Cool man, so the FPR regulates fuel pressure based off air pressure? And also is that gauge in your pic measuring fuel pressure or air pressure?

vwblackb5
03-23-2016, 06:32 PM
vwblackb5: Cool man, so the FPR regulates fuel pressure based off air pressure? And also is that gauge in your pic measuring fuel pressure or air pressure?

Quick explanation. Fuel comes from the fuel pump in the tank. It goes into the metal rail that feeds the injectors. At the end of the rail is the FPR. The FPR creates a restriction so that all the fuel in front of it builds up pressure. From the FPR the fuel flows back to the tank. Fuel is always flowing in a loop from the pump, to the rail, through the restriction (FPR), then back to the tank. The more restriction in the FPR, the higher the rail pressure will be.

The gauge you see is a fuel pressure gauge and gets installed in the line leading into the rail. The fuel in this line is before the restriction (FPR) so it is at the same pressure as the fuel in the rail (what the injectors are getting).

The FPR is manifold-pressure controlled. That's what the little vacuum line from the intake manifold to the FPR is for. When the intake manifold is at high vacuum (closed throttle), the FPR reduces fuel pressure. When the intake manifold is under boost, the FPR increases fuel pressure. To properly set an Adjustable FPR, you need to disconnect the little vacuum line that goes to the FPR. With this line disconnected, the FPR is neutral and not being influenced by the intake manifold pressure.

TL;DR the gauge is a fuel pressure gauge, helps me adjust my adjustable FPR based on my tune. GIAC PC16 for my K04 ran best between 2.7-2.8 Bar.

maxiz1
03-23-2016, 08:10 PM
I'm clueless about which check valve you guys are talking. Care to post a picture?

b5a4erik
03-23-2016, 08:46 PM
Quick explanation. Fuel comes from the fuel pump in the tank. It goes into the metal rail that feeds the injectors. At the end of the rail is the FPR. The FPR creates a restriction so that all the fuel in front of it builds up pressure. From the FPR the fuel flows back to the tank. Fuel is always flowing in a loop from the pump, to the rail, through the restriction (FPR), then back to the tank. The more restriction in the FPR, the higher the rail pressure will be.

The gauge you see is a fuel pressure gauge and gets installed in the line leading into the rail. The fuel in this line is before the restriction (FPR) so it is at the same pressure as the fuel in the rail (what the injectors are getting).

The FPR is manifold-pressure controlled. That's what the little vacuum line from the intake manifold to the FPR is for. When the intake manifold is at high vacuum (closed throttle), the FPR reduces fuel pressure. When the intake manifold is under boost, the FPR increases fuel pressure. To properly set an Adjustable FPR, you need to disconnect the little vacuum line that goes to the FPR. With this line disconnected, the FPR is neutral and not being influenced by the intake manifold pressure.

TL;DR the gauge is a fuel pressure gauge, helps me adjust my adjustable FPR based on my tune. GIAC PC16 for my K04 ran best between 2.7-2.8 Bar.

Great explanation man, much appreciated.


I'm clueless about which check valve you guys are talking. Care to post a picture?

Sure man, I'll post a picture when I'm back working on the engine bay (will be till Saturday).

pbcrazy
03-24-2016, 06:09 AM
Maybe I'm just under thinking this, but its probably just a generic check valve they fitted and they didn't need to use the nipple. Not every part for every car is unique

b5a4erik
03-24-2016, 11:21 PM
Maybe I'm just under thinking this, but its probably just a generic check valve they fitted and they didn't need to use the nipple. Not every part for every car is unique

That just might just pbcrazy enough to be right.

maxiz1: http://i.imgur.com/wxMWoQl.jpg?1 circled in red. The line coming from the top of it is connected to where the nipple/cap would've been, I've since applied it for use as my boost gauge line source, as recommended by previous users' posts.

haha and the reason my coolant res. cap is off is because I was doing a coolant flush.