2000 S40 1.9 L whiney turbo?

[keithatcpt]

How loud is too loud? I've got a 2000 S40 with 148k on the odometer and the turbo (and 124k on the motor). The original motor broke the timing belt, and I just changed out the motor. The car runs like a champ, but on acceleration, the turbo whines a bit. As I watched my wife drive away, I thought my neighbor had started a table saw. From inside the car, if you turn the radio up a bit, it covers the sound. Should I be looking at rebuilding the spare turbo that I have asap, or is a little whine normal?

- Keith
2000 S40 turbo 148k
Previously had a 94 850 non-turbo

[keithatcpt]

Ok, possibly a more intelligent perspective now that I've researched the problem a little. After talking to someone who owned a 740 turbo for about 15 years (one owner, 215k miles), he said that I shouldn't hear the turbo "until I actually use it." I think what he meant is that the turbo shouldn't kick in until the higher RPM's and that at low RPM's the turbo isn't used. I've noticed that on my S40, the waste gate actuator looks like it's closed at idle. I'm pretty sure it's still closed at low speeds, but I'm not sure because I can't run that fast. lol. I checked the vacuum valve that looks like it's supposed to open the waste gate, and it's connected where it's supposed to be.

So, modifying my question a little, should the waste gate be open at low rpm's and close as the RPM's increase? Any other ideas?

Anybody?

- Keith

[billofdurham]

The wastegate should open at higher RPM to prevent the turbine spinning too fast.

This is an extract from HowStuffWorks:

Most automotive turbochargers have a wastegate, which allows the use of a smaller turbocharger to reduce lag while preventing it from spinning too quickly at high engine speeds. The wastegate is a valve that allows the exhaust to bypass the turbine blades. The wastegate senses the boost pressure. If the pressure gets too high, it could be an indicator that the turbine is spinning too quickly, so the wastegate bypasses some of the exhaust around the turbine blades, allowing the blades to slow down.

You can see the full article at: http://auto.howstuffworks.com/turbo.htm

You will also find links to other articles on turbos.

Bill.