JTD 16v, Not reaching boost like it used to. - Alfa Romeo Forum
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(Post Link) post #1 of 5 Old 23-05-18 Thread Starter
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JTD 16v, Not reaching boost like it used to.

Hey All,

I noticed about a year or so ago that my car started to feel slower, i had no job at the time so it wasnt priority. Now working again, i can investigate a bit and see what i can find out.

Car used to hit full boost reasonably early, but now it just about gets there by the redline. Fueling is fine, its more the boost/MAF stuff thats the issue it seems.

The list of things ive changed/done so far:
Fitted 4 new injectors
Fitted new genuine MAF
Fitted new genuine MAP
Fitted new genuine Boost Solenoid
All Vacuum hoses replaced.
EGR removed completely.
No Swirlflaps.
Turbo is fine, no damage to coldside either.
Actuator moves as it should do.
Intercooler pipework is 90% stainless, which ive had off and checked also.

If it helps aswell, car has following mods:
1756v Hybrid.
FMIC
Decatted
Straight through exhaust.

The injectors helped with coldstarts/stuttering and also mid-range, but its still not what it was before.

Any idea where i head next?

Ive attached a graph/xls from MES.

Cheers

Luke
Attached Files
File Type: xls Boost-Maf.csv.xls (21.5 KB, 9 views)
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You say the turbo is fine. Are you absolutely sure the VNT mechanism is not stuck due to carbon deposits insite the hot side of the turbo? It is very common that sticky carbon deposits and rust inside the VNT mechanism of the turbo causes power loss. Remove the actuator rod to feel if the VNT mechanism moves very easy.
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(Post Link) post #3 of 5 Old 28-05-18 Thread Starter
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I've just been out this morning and undone the actuator again, the mechanism is free as a bird.
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Maybe it's an idea to do a pressure leakage test on the intake?
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Quote:
Originally Posted by lungnut View Post
I've just been out this morning and undone the actuator again, the mechanism is free as a bird.
Too free? Here is a quick test that will give you some idea whether the vanes are moving when the VNT lever does.

Take the top boost hose off the manifold, make very sure that only air will get sucked into the engine and start it. Now disconnect/reconnect the boost control solenoid. Very considerably more air should come out of the boost hose when the solenoid is connected, especially if you rev the engine a little.
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