View Full Version : Unlimited boost

03-29-2008, 01:23 PM
So my rebuild is finally finished, i got word that the car runs great, they found some problems along the way that needed fixing (8year old car so figures). But, if you step on it, they say it goes into unlimited boost, the needle on the boost gauge goes well past the 25psi mark. This wasnt happening before when the car was working right, i had at most 25 psi. So im not sure whats the deal, could it be wastgate? n75?

03-29-2008, 01:52 PM
Doesn't sound like a problem to me, I'd like to have unlimited boost [:)]

If your wastegate wasn't functioning properly, your car would sound very very different, and as for the n75, are you getting a CEL? I'm not quite sure what it could be if it's not those two, perhaps someone else can post something more knowledgeable

03-29-2008, 02:09 PM
Whats up leifer, lol from audiforums! I got tired of that place to be honest.

Problem, im in Tallahassee and my car is in Tampa where im from. My dad has been hands on with the car recently, he says its 100% better then before, it runs great, nothing about a cell, no noises. I was doing some reading that if the line from the wastegate to the compressor side of the turbo then it will do just that, run unlimited boost. Now the shop isnt audi specific, but i have the upmost confidence in them as techs, and friends of the family. My reasoning is they didnt hook up the n75 properly, and dont know it, since the vac line from the wastegate goes to the n75 and into the TIP.

Any ideas? Leifer, i think Brian (chaos) from audiforums did this and blew off his some hoses. I just cant find his post.

03-29-2008, 02:11 PM
"Inside the wastegate is a diaphragm which creates a seal, and a spring which holds the wastegate closed. Spring rates vary depending on the amount of boost you want to run, typically they are given in a "bar" value for example 1 bar would be 14.7psi. This would mean that in order to open the wastegate you would need to excerpt a greater pressure than the 14.7psi spring holding the wastegate closed. In order for the wastegate to work you must have the compressor reference port hooked up to the compressor side of the turbo, if you don't have this vacuum line attached than the boost pressure will not be limited to the set spring pressure; it will build unlimited boost pressure until your engine is destroyed."

Explanation i found... somethign i already knew, anyone deal with this before?