Or, "Reading through the turbo FAQs and got a cold chill"

I was finally able to really "test drive" the '95-944T I posted about earlier. I picked it up from the dealer tonight to deliver it to an independent Volvo (and others) mechanic, a 20 mile drive, for a pre-purchase inspection. (It could be a no-purchase inspection and the best $100 I ever spent.) Handled very well, tighter than my 945 na. 99k and clean looking through the oil filler cap. Engine was cleaned and polished. All I remember is that the turbo air hose (with the double clamps on the end) looked new. Now everything looks new. There are a few minor things that I'm not concerned with right now, missing and broken clamps over the air filter cover, loose trim in and out.

With the hood open, there was a lot of engine noise, a lot more than my na. Valve adjustment and worn pads maybe? I couldn't hear the slower "knocking" any more

When accelerating medium to hard, there seamed to be a little too much gray-black smoke, right after the down shift. Noticed it while driving tonight with my wife's headlights right behind me. Oil leak in the turbo? FAQ mentioned a rich mixture caused by the AMM.

In the driveway, I increased the RPM to about 3500 and let it come back to idle. I noticed a few muffled backfires. Running to rich? AMM again?

Turbo specific, winding up the turbo a little or a lot while driving then letting off the gas there were an iron lung type, 1-2 second "exhale" noise. New to me.

I'll see what the inspection report says and post the results.
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Tom F

those exhale noises are your blow off valve

Thanks. I think I see. This is controlled by the actuator that opens the wastegate, bypassing the turbo, allowing the turbo to slow.
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Tom F

You are sort of right.

The noises when you get on the gas, then shut the throttle plate is the Compressor By Pass Valve or CBV for short

This is a valve, that when the throttle plate is closed, the air gets vented back to pre-turbo piping (so before turbo, but after AMM).

Think of this.

You are producing full boost. Now you slam your throttle shut, where is this boosted air in the IC piping supposed to go? It sends a shock wave backwards, which hits the compressor wheel of the turbo, slowing the turbo down. In worst case senario's you can actaully break the turbo main shaft that conects the compressor side with the exhuast side. I've never seen this, I've only heard of it from reliable sources. I run a blow off valve from a Mitsu Eclipse on my car. And run up-wards of 20psi.

The sound you are hearing is A-OK.

Turbo cars do make more noises. I've just put on in my 1979 242GT. Its taking some getting used to all the noises.

Hopfully everything checks out. Turbo's are lots of fun. And a 940 with a turbo is VERY nice.

Jordan

Thanks, Jordan G.
I hit "HowStuffWorks.com" to catch up on turbo basics. Cool site. RPI grad, ex. NC State Prof liked to research, learn, and write about it, (kind of like some of us Brick Heads), posted it on the web, then turned it into a small business. Adds about 4 new "Stuffs" per week with his staff.

The Brick Head mechanic gave the car an over all "clean" bill health, per my wife. Alot of minor stuff, normal wear type, small rear seal leak, oil melted lower rad hose, needs exhaust work. He noticed that it was a nothern car but no rust except that it's harder to remove stuff like bolts. (A VA car, not quite the north, but subject to snow and sodium chlloride.) It needs all the no history catch up work. Now with two 940's in the family, I have a great excuse to invest in some of the "greeen manuals", a crank pully removal tool... The mech said it was an odd mix of options. Turbo, winter package, remote entry (not working), cloth seats, no moon roof, no power seats, steel wheels.

I'll pick it up tomorrow, get some first hand info, go to the dealer and hope a bag of cash falls out of the sky on the way there.
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Tom F