Pressure Testing my 1.8t?

[CuseBora]

well heres the deal, ive noticed that for some reason in 4th and 5th gear i seem to have some sort of surging going on. I called AWE tuning to see what they thought and according to them i could have a small boost leak that only has an effect at higher rpm's, but im stumped. The dude suggested pressure testing the system, so does anyone here have the means of doing that??

[boostin20v]

you need to plug the system and add pressure to it. McShane's got a cool tool he made from a PVC tubing end and a air compressor nipple, stick it into a IC tube and turn the compressor on and it will allow you to find any leaks.

[BUNNYLOVE]

I didn't make mine from PVC, but you can. Mine is just steel plumbing fittings from the hardware store. I used steel because it use a regular quick release air chuck and fitting on mine and it just threaded on.
If you don't have an air compressor you can use a bike pump and a valve stem with a PVC pipe cap. You should use some sort of gauge too if you don't have a boost gauge.

You basically measure your connector at the TB wich should be 2.75" ID on a 1.8T and find a fitting that fits snugly inside. I use and adapter fitting which is 2" pipe (way bigger OD) to 1/2 NPT pipe thread IIRC. Then you get a 1/2 to 1/4 reducer fitting and screw in the compressor quick realease fitting.
OR get a PVC end cap and drill for a valve stem and expoxy it in. This would would with a bike pump or compressor. Then you just hose clamp it on, pressurize 10psi or so and spray every connection down with soapy water. Wherever there is a leak it bubbles.

[CuseBora]

thanks guys, ill see what i can do and report findings.

[RichB]

Some folks make these pressue testers as well if you are not handy at genning one up yourself. Here is one by Modshack: http://www.modshack.info/Pressure.htm

[customfabvw]

what kind of bov are you using or are you using the stock dv? if your using the stock one you prolly have a small rip in the diaphram which is causing the leak!

[CuseBora]

im using a Baileys DV which holds up to 60 PSI so i know it isnt that, ive experienced surging from a leaking stock DV on my last 1.8t, and the way its "surging" or fluttering i should say isnt the same, so i guess it calls for a pressure test...

[customfabvw]

your n75 valve could be taking a dump!

[CuseBora]

really?

[boostin20v]

yes, N75 controls the wastegate which could be causing the surge.

[CuseBora]

hmm, well is there any way to check the n75 without replacing it and seeing if the problem is solved? also it only surges in 4th and 5th gear, whereas in my old jetta it would do it through every gear, i dont know if that makes a difference on what the problem could be, or...?

[RichB]

yes, N75 controls the wastegate which could be causing the surge.

True... is the surging at part throttle or full throttle? I Have some N75s (stock F and the ECS race.. which is the H vlave I think) you can borrow to see if that helps any. I'm using the J on my GTI right now.

[CuseBora]

well it flutters at full throttle but only in 4th and 5th gears, which is the part that confuses the hell out of me. As for the n75, is there any kind of performance difference to be noticed with an aftermarket one or?? also what would the difference be between the H? and the one your running right now?

[RichB]

They basically vary in thier reaction time which impacts how the car repsonds to requested boost and how well they damp surging (which I guess can be viewed as a kind of oscillation in the controll loop that attempts to regulate boost level)

The stock valve is farily quick (though older 1.8Ts may not have the F valve). On some chipped cars this N75 will give surging (all cars recact differently).

The N75J is generally known for being the smoothest... its fast and tends to allow somewhat higher peak boost (spikes) ... often the valve that solves full throttle surging on a fair number of cars.

The ECS race (i.e the N75H if I recall correctly) is very agressive... can run some cars into limp mode becaase it will allow too much boost. For me this valave is a bit surgy in character those other have reported it helped smooth things out.