9.2 AFR @ 9psi - Turbo sounds like something wrong

[Schmieder]

UPDATE: Two of Five bolts were busted bolting the downpipe to the Turbo. The gasket was blown out and there was about 1/4" gap at the worst side. The downpipe flange was warped, the turbo not warped. I welded the flanges together and inserted a V-Clamp type mating to the downpipe. It is a knock-off turbo anyways so the welding was acceptable. I couldn't do that to an authentic turbo built strong.

Idles quiet again. I did not test drive yet.
End Update

I'm not sure how the AFR's got so low. I was tuning the MAF a little bit though I only made microscopic changes.

Anyways, here is whats wrong. Hopefully you guys can figure out the damage did to the turbo.

I boosted up to 9 psi at 100% TPS. Just as I release the throttle (when my wideband hit the 10 afr warning) the turbo made a loud whine while spooling down. Two small backfires also occured.

I drove home on a very easy throttle staying out of PE. But there was a hill I had to climb and boosted 2-3 psi, nothing max. The turbo spools up normal and the engine acts fine during light boost. But still a strange, loud whine at spool down.

Full boost has a multiple frequency sound, like 3 or 4 turbines wandering near each others rpm. And releasing the throttle, during spool down there is atleast 1 backfire sound, 3-4 tops. The backfires are more frequent with more/longer boost.

The exhaust note is a little louder (sure I cracked a manifold or exhaust pipe). I hope I didn't crack the turbos turbine housing.

The engine operates perfect at idle and any kind of load that is not boost.

With the engine freshly shut off, the wideband stoich readings go to 20+ in a minute or two.



With everything said, it is obvious I have a cracked mani or pipe somewhere in the engine bay (haven't disassembled yet). I just hope my turbo is ok.

Is it normal to hear the turbine whine much louder if the pipe was split near by the turbine?

I'm surprised this happened at 9.2 AFR. Normally boost is 11.5-11.2

Oh well, any and all opinions welcome. Thanks

[Azrael]

Running that rich the backfires might be afterburn from unburned fuel combusting when it hits the hot exhaust parts.

[Schmieder]

Running that rich the backfires might be afterburn from unburned fuel combusting when it hits the hot exhaust parts.

The rich condition has been corrected. What ever it was, I reverted back one tune file. I save every change so I can retrace my tuning steps if I must.

What bothers me now is the 'awkward' whine coming from the turbo at 5psi + and the loud spool-down whine.

I thought a turbo was supposed to be able to handle brief rich conditions. Nothing long term of course.

I guess my real question is...Can serious damage occur to the turbo running pig rich at boost. Even if it was only a few seconds at most? Or is this loud whine typical of a blown open exhaust downpipe or cracked manifold?

I'm going to find out soon enough when I get in there to investigate. But that won't be for a few days yet. sigh.....I might have to buy a new turbo soon!

[Joseph Upson]

Do you have a blow off valve? if not some of the noise is from back pressure on the compressor wheel when the throttle shuts and that will damage the turbo with time. If bad enough it can bend the blades. You need to check your plumbing to the turbo also to make sure there is no leak under pressure.

[Schmieder]

Do you have a blow off valve? if not some of the noise is from back pressure on the compressor wheel when the throttle shuts and that will damage the turbo with time. If bad enough it can bend the blades. You need to check your plumbing to the turbo also to make sure there is no leak under pressure.

BOV, yes and it was/is tuned well. Flutters at idle, closes tight at the slightest throttle and blows off all pressure, no back pressure issues.

I do believe I open the exhaust somewhere as the exhaust note is louder in the bay, slight smell and wideband goes lean fast when shut off (fresh air leak).

But the turbo sound is definately unique now. Far too loud and sounds like a jet airliner turbine. My first guess is the bearings just went south. But from a brief rich condition.....perplexing.