Kriation

Folks,

I did a VAG run tonight with the stock program (51 degrees/dry) through 2nd and 3rd and came up with the following graph:

<img src="http://pictureposter.audiworld.com/22821/graph.jpg">
Solid blue = RPM
Maroon = Requested Boost (psi)
White = Actual Boost (psi)

It doesn't seem like the system is leaking... I'm thinking that either the N75 has lost it, or the MAF has. The reason I mention the latter is because on the run previous to the one that generated this graph, the highest g/s recorded was about 214. Requested boost in psi is about 10.5, and the actual was about 8.

I'm going to check the usual suspects (TBB, Forges) on Saturday, but I have a new N75 on order which should be in my hands by tomorrow that I might replace with the old one while I'm at it.

Any thoughts?

TIA!

bagodoosh

i'd be interested to know what the problem is.

<img src="http://bagodoosh.home.comcast.net/s4/oleg_115.gif">

VR_Life

Checked for Boost leaks ? TBB, Hoses ?

davenew

Unless you get very lucky you'll never find all boost leaks without doing a pressure test. I bought an air compessor just for pressure testing It's also nice to finally have one for air wrenches too.

You could try replacing much of the stock braided vacuum line, if it's original. The braiding hides the dryrotted rubber hose. WHen I bought my car the hoses going to the fuel pressure reg and bypass valves were leaking. Not to mention one of the small tees at the rear of the engine was cracked in half

VR_Life

2nd - Compared to VAG-COM : A decent size Compressor is cheaper, and same/better return on invest

daves4

When I had the TBB leak, I did get above 1350mbar

Kriation

So I replaced the N75 today, and relubed the Forges while checking for leaks. I had replaced all the braided hoses with silicone a while back.

I think the problem was the N75. The following graph, compared to the one that I posted on the 15th, is looking a lot better. The temperature during the run was about 74 degrees. Colors on the graph are identical to the original:

<img src="http://www.kriation.com/pics/graph_02.jpg">

I ordered the appropriate parts from McMaster for the pressure tester and will be doing the test next Saturday. I'll keep this thread updated.

Thanks!

Here's the link to my original thread: <a href="https://forums.audiworld.com/s4/msgs/1968811.phtml">Click</a>

VR_Life

Yep - not limp mode boost anymore ;-)

bagodoosh

did you get N75F? cost?

Kriation

The part number of the N75 that I bought from ECS was: 078906283B