I installed this boost guage yesterday that was previously installed in my R33, 8 months ago. It was working fine in Skyline upto 1 bar and was accurate.



Now in FD it shows some confusing readings i-e as follow

Idle 900 rpm reading- 500 mm/Hg
7000 rpm reading in Parked car- 0 bar
Full boost while running- 1 Bar (the most confusing)

My car is bone stock, and its running fine. Never messed with stupid tweaking or anything else. I guess there is something wrong with this boost guage, since i temporarily installed the same guage that was new a month back and it showed almost 9 psi.

Is there a way to fix it, or shall i trash it?

 

None of those readings seem confusing to me.

• 900 RPM idle, 500 mm is about 19 in Hg, which is a good vacuum, but not too much for that idle RPM
• 0 at 7000 w/ no load may be about right with intake and exhaust restrictions
• 1 bar full boost may also be correct if it was a cool day when you did it. What conditions, what gear was this? The stock boost "control" system does not compensate well for cool conditions.

I would, though, calibrate the gauge against a known accurate one.

 

Isn't 1 bar like 14.7 psi? That's almost 5 psi over stock. I guess I never realized the stock boost control system was that poor...

 

It is 14.5 psi. And, yes, the stock system can allow (at least close to) that much boost under the right (wrong?) conditions. It just tries to match the pill orifices against the "orifices" created by the pulse-modulated boost and precontrol solenoids, using a fixed map. The stock setup does not use boost feedback to control boost. And if any critical vacuum hoses split or come loose, who knows how high boost will go. That is one of the main reasons to have a boost gauge so you can know whats going on.

Dave

 

If your car was imported it's possible it's not exactly stock. Do you have the OEM downpipe, muffler, main cat, and intake?

If so, then there is something wrong with the boost control setup. Make sure there are no leaks in the lines branching out from the wastegate actuator.

Dave