2002 1.8T Quattro 5-spd 58K miles.

There is a noticeable hissing sound that comes from the passenger side of the engine upon acceleration, no matter how hard or easy driven.I'm assuming it's the BPV releasing boost into the airbox.I replaced the plugs thinking the ECU was dumping the boost to avoid engine damage from detonation since they were pretty old, but it stilldoes it. Is this a normal sound for an Audi (since I'm more familiar to Saab's), or is something not right?

 

I haven't heard anyone ever talking about a hissing sound except when there's a problem. The OEM turbo is really small and I doubt you're hearing spool-up on it. Do you think the car is running somewhat slow, or otherwise abnormally, that might indicate a boost leak? That's what it sounds like you're describing. You could start by inspecting your lines and fittings around the turbo and airbox area and make sure you don't have a cracked line or disconnected fitting.

 

or maybe his tubing might have a sall crack and it hisses under pressure. that happened with mine...

 

Yep - in any event, first step is to inspect all the lines and connections down there. Chances are there'll be some visible evidence. Maybe someone can rev the engine while you're looking and listening. It could help you nail down the area that has the leak.

 

the turbo doesnt boost when not under load... and i doubt hed hear anything whith the motor in his ear...

 

Very true, and I realize that load is required for the turbo to actually pressurize, but there's still a chance he may hear something this way. Since he said it doesn't matter how hard or gently the car is driven, it's possible that the leak is something other than turbo-related, if it's happening before boost is being built up. In any event, it can't hurt to try

 

absolutely wont hurt to try... i was just trying to help him out so he doesnt get his hopes up

Edit: i also think it would be easiest to diagnose when at idle, theres a good amount of vac and little engine noise.

 

Agreed on both counts. Chances are it's a cracked or broken part somewhere, and it may even be visible with a little time looking around. And the DV idea isn't a bad idea at all - given that the OEM DV is considered to be weak (and it's plastic if I remember right), it's a good candidate for the problem.

 

Thanks for the tips.

As I said, I'm most familiar with turbo-Saab's. Have worked on them for years.

When I heard the hissing noise, I immediately thought that the ECU was sending the signal to have the DV/BPV open and release all of the boost into the air delivery system. That's how it works on Saab's when the ECU senses any malfunction and tries to avoid engine damage.

I thought that maybe it was due to the plugs having 58K miles on them. They were the oem PFR6Q's. I put in the BPR6E's (I like copper for turbo's), gapped to 0.030", and the hissing noise is still there. I had a friend drive while I hung outside the passenger window and could hear it loud and clear from that side, which is where the airbox is.

The sound is only heard when the turbo is boosting, no matter how much. I wanted to know if this was a normal sound for Audi's when under boost, as in the turbo spinning or the boost as it'sbeing forced into the intake system.

On a side note, what is up with everyclamp being the crimped-on style on Audi's? Does this mean I have to cut the clamps and re-usehose clamps when working on any of them?