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Discussion Starter · #1 ·
Hi, I have a BNR tune with nearly 23psi which starts dropping at 4000rpm and ends up at about 15psi. The stock wastegate actuator is on it's way out as it used to only drop to 17psi. My question is: Does the boost drop in high RPM only because of the weak stock actuator or is it because it's a small turbo? Or is it a combination of both? When is the bigger turbo needed?
Thanks in advance,
Muz

Here is the power curve (not all data is accurate to unit readout i.e. max boost is 23psi. Graph is accurate though)
Orange = RPM
Blue = Boost
Green = Torque

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Not sure if this happens on our Cruzes, but I know when my other turbo car sees detonation, Knock retard, it pulls timing out & then the boost drops down also.
What octane fuel are you using?
 

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Discussion Starter · #4 ·
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Thanks for the replies :)

I added knock retard (purple top graph)
and retard due to knock (purple bottom graph)

Knock retard is about 2 degrees

I'm running 98 octane (BP Ultimate)
The spark gap is 18.5
 

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Probably because it's a small turbo. Note that the stock 1.4 has the same horsepower rating as the 1.8. I've heard before that the turbo runs out of breath at higher RPM. The advantage of the small turbo is that it spins up faster, making the engine more responsive. That would be more important to most people than the amount of power available at WOT.
 
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