Turbo boost surge - graph attached - Alfa Romeo Forum
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Brera 2.4

Turbo boost surge - graph attached

Hi all,

I have had a surge in power at around 2000-2500 rpm in my 2.4jtdm Brera for the last couple of years and just lived with it. The other day I connected it up to MES and took it for a quick drive with the turbo boost being logged. Attached are the results.

As you can see, when I gradually accelerate at around 150 seconds, the actual boost massively spikes before dropping rapidly back down to normal - this is the surge.

At around 170 seconds, I floored it and as you can see, there was no boost surge.

I read this post (Hello, and oh dear -- boost pressure.) on the 2.4 in the 156 and I thought that I had the answer to the problem - replace the VNT solenoid. That was until I discovered that the newer 2.4 in the Brera doesn't have this!

Can anyone help with any advice on what the attached log could mean? Is it likely to be a problem with the turbo itself and is there anything I can do to help it?

Many thanks all!
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File Type: jpg boost-pressure.jpg (54.4 KB, 26 views)
sammyblackbaron is offline  
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Sorry I cannot help, but I have the same problem, mine is an 57 reg, so an early one I guess. May try your solution if I have said solenoid.
Philjay50 is offline  
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sticky vnt most likely, due soot and rust.

make a log of the vnt solenoid PWM aswell, so you can see if the ecu is actually trying to reduce the boost level or not. Looks like it is from the underboosting shortly after the overboost.
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