Anyone able to help with this in an R33 GTR?

[judasentinel]

My car came with this unit installed (attached pic). I have been trying to understand how it works and what it does, but there is no info available online at all.

Can someone please help or point me in the right direction?

A brief description of the unit. Its called VACS (Variable Airflow Control System), so I am assuming it controls airflow, but dont know how. Does it alter the TPS voltage, the MAF voltage, or both, or does it change injector flow? I havent really looked into where it connects. It has two knobs on it - control point and main volume. Not sure what control point does and where it needs to be set for the R33 GTR. The main volume knob does affect the idle speed, but it is likely it does that by altering the airflow signal, thereby causing the fuel flow to change. If the revs go higher, does it signify a leaner mixture as I have come to know?

The main point of concern for me is the setting of the control point knob, so that I don't blow up the motor or cause catastrophic damage to it.

I also have the old school Apexi AVCR installed, which was set at 0.65 bar. However, even at that level, it would actually allow the car to boost at around 0.75 bar. And when I changed it to 0.85 bar, I made over 1 bar of boost. Is that safe, assuming the car has stock turbos? Can they be run at 1 bar all day or am I looking at turbo failure soon?

And one final question - without exposing the turbos (which is a pain on these cars), can one tell if a turbo fails - loss of boost, smoke, etc..?

Thank you guys.

[Skym]

Airflow = Airflow meter / Mass Air Flow that it's called in US, etc.

I believe it's the same as the HKS EIDS (look at the HKS EIDS manual, as has the same 2x adjustment knobs).

From memory one knob is for where it selects the cells on fuel (rich or lean), ignition map to match and the other knob is for how long it stays there (usually in seconds). It's designed to stablise the airflow signal from MAF's when have atmosphere vented BOV's.

The atmosphere BOV's cause the turbo's to slow down. The turbo's slowing down create reversion problems (air reversing direction and heading towards the MAF's which upsets the voltage signal from MAF's and engine can run too rich, stall).

Wailing (compressor wheel touching compressor housing due out of balance shaft. This can be due to bearing failure that relates back to oil breaking down or oil seal failure), loss of boost (won't boost past 0 on boost gauge if loses ceramic exhaust wheel) are the common signs of turbo failure. Also white exhaust fumes if oil seal fails on exhaust side of turbo.

It should be ok at 1bar for short burst's on the street. Constantly on racetrack is where the problems would occur due to high oil temps, etc.

Usually when turbo's age the shaft's go out of balance due to worn bearings and the higher the boost level you run (turbo runs at higher rpm to achieve the higher boost level), the more out of balance the shaft gets. If the out of balance shaft gets bad enough, the exhaust wheel or compressor wheel can hit the housing, shatter (ceramic exhaust wheel shatters) or make wailing noises (compressor wheel touching compressor housing).