Boost Gauge Question

matteo

Registered User
Why is the gauge in psi when boosting and mmHg in vac? The readings are both just relative to 1 atm, right? So why two scales?

Also, some of my friends say I can’t trust the boost gauge and that I should get and aftermarket gauge. How accurate are the stock gauges?
 
In short, vac is normally measured in mmHg. You can always convert it if you really need to.

And true, the boost guage isn't really all that accurate, but most people don't really need the accuracy unless you running some serious boost (nitrous?). Personally, I'd save my $$. Just my opinion.
 
96sport said:
14.7 psi = 1 atm, but 760mmHg = 1 atm

In case you want to convert.
That’s right, I didn't think about that. If both vac and boost were both in psi, the needle wouldn’t even move in the vac since 18mmHg is roughly .11 psi. Unless of course if the vac side of the gauge only went to .15psi, and that would just look stupid.
 
matteo said:
That’s right, I didn't think about that. If both vac and boost were both in psi, the needle wouldn’t even move in the vac since 18mmHg is roughly .11 psi. Unless of course if the vac side of the gauge only went to .15psi, and that would just look stupid.

I thought about posting that....but I know that tcshum is right...usually vac is stated in mmHg.

Russ
 
Actually the boost gage in the SC is calibrated to " of Hg (inches of mercury). A theoretical "perfect" Vac. would correspond to ~28" of HG. (1 atmoshere or a -14.7 PSI if such a thing existed) So your boost gage measures basically from a -1 atmosphere of pressure to a ~ 15 PSI or a positive 1 atmosphere of pressure. It is nothing but a diaphram type gage.
 
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