Signs of a split boost pipe? - Alfa Romeo Forum
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(Post Link) post #1 of 6 Old 05-03-11 Thread Starter
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Signs of a split boost pipe?

Afternoon people,

Car in question is a 156 1.9JTDm 16V. And now for the issue. I've noticed over the past week or so I can hear the turbo alot more. The sound is akin to police sirens in the distance. In higher gears at speed the car does seem to have less grunt as well. Could this be symptomatic of a split boost pipe?

The upper pipe from what I can see is fine, however it is my understanding that to get to the lower pipe, I'll need to jack up the car and get the undertray off first. Is this correct?

To avoid doing this, I figured that if there was a split in the pipe, I'd be loosing boost. So I've just taken the car for a quick spin with FiatECUScan running, monitoring engine RPM, throttle position, desired boost pressure, and finally actual boost pressure. Would this be an accurate method of diagnosis? Looking at the results there are points where actual boost pressure is 200millibar below desired pressure - is that enough to notice lack of power?

I've attached a CSV of what was recorded if you want to take a look.

So could this be a split boost pipe, or am I looking at something more sinister to do with the turbo itself?

Any responses/tips appreciated.

Stu
Attached Files
File Type: xls Boost test.xls (43.5 KB, 26 views)
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Often with split boost pipes on Turbo cars the boost will come in further up the rev range.

Plus you get a whistling or whooshing noise as the air leaks out of the hole.
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It could be that the leak is before the turbo if your not getting black smoke.
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Quote:
Originally Posted by nick9one1 View Post
It could be that the leak is before the turbo if your not getting black smoke.
On the pipe coming up out of the air box there's a sort of chamber type thing connected to the pipe after the U bend. This does have a hole in it where the conduit of one of the harnesses rubs against it. Its been like that for a while and I just cover it with duct tape. Seems to work fine, and that was present before the noise started.

How much work is it to remove the undertray? I don't have ramps or anything, but would i have enough room to remove it if i used the jack in the boot?

Cheers
Stu
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Yes, but don't get under it without axle stands in place will you?!

going from front to back:

5 x torx at the front (3 across the front, 1 each side in front of the wheelarch)

2 x 5mm allen key (1 each side, bottom of inner wing)

2 x 10mm bolt (1 each side, into the subframe)

quite easy to remove but awkward to get back in by yourself copper grease the threads before refitting the bolts - they corrode!

And on the main subject: I think I may have a boost pipe leak too. Getting a black smoke "haze" under hard acceleration, middle to upper rev range? Or is it going to be a dirty air filter perhaps?
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Even if the hole in the plastic U bend isnt causing the current problem it will be having an effect on running.
The MAF sensor (measures how much air is entering the engine) is located before that hole, therefore the engine is getting more fuel than it thinks.
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