VelociRedBeast

Can someone explain to me how to read a boost gauge please?

zoomzoom_8

If your gauge measures like this .5 , 1.0, 1.5 then it means 5 psi of boost, 10 psi of boost and 15 psi of boost, make sense?

Richard Paul

iTrader: (5)

I don't think so. If it reads like that then it is in "Bars", each bar is aprox 14.5 psi.
So again rounding it off .5 is 7psi and 1.0 is 14.5 and so on..............

If it is in other sorts of mesures it could be inches of mercury which is aprox 2 in hg for one psi.
Normally a manifold gauge for aircraft read in in hg but they start at abs zero so at sea level the read 29.92 in hg. in hot rod speak thatt would be zero boost engine off. then thereafter you can use the two inches per pound after taking away the 30 inches you started with.

Example: reading=45 in hg. minus the 30 divide by two =7.5psi

Fanman

Exactly what Richard Paul said. BAR is the metric measurement & is 1 standard "atmosphere" of 14.7 psi. So, .5 bar is approximately = 7.35 psi. I have just swapped out my Greddy boost gauge (BAR) for new Autometer gauges that come in "American" measurements (lbs./psi of boost) on my car.

army_rx8

hehe so you didn't like "Raising the BAR"? hehe sorry i couldn't help it :p

zoomzoom_8

okay, so i was really wrong up above, now that i have the turbo finally install I am trying to learn this stuff right So on the gauge attached, if the needle is at the third little line, then that is roughly 4.41 psi of boost? Is that right? Thanks for the help.

Fanman

Correct. .3 Bar = 4.41 psi/lbs. of boost.

Lschiavo

LOL,just try .7 or .8 "psi" of boost in your gauge and I will be laughing with the smoke cloud around your hood... :D
At least it was clarified for you before you set it to .8 bar thinking it was PSI LOL

zoomzoom_8

yea, glad I did not have turbo then and now I finally understand and trying to get my turbo leaks all fixed.

SAFD1450

I always wondered what a bar was. Great info. Once again this site has made me glad I paid my subscription fees!

Richard Paul

iTrader: (5)

For starters your gauge will be at 0 when not in use. assuming your at sea level. You will see a lower reading as you drive up the mountain. That is if this is an absolute gauge, which I assume it is. Otherwise it is always referenced back to the ambiant pressure or gauge pressure.

Next, one bar is not 14.7 psi. It is 14.5 psi. In fact it is the equivalent of 100 KPA. (Kilopascals) Using the metric system. Sorry Fanman, you must have read my post too fast. But what you say is the most popular explaination, yet it is still a little off as it was not taken from a mesuremant of the atmosphere it is just the equal of 100 kpa. The fact that it is close was just luck. However it is a more realistic number to correct to since one is rarely at sea level and 60f.

You may then break it down into tenths if you like and call each .1= 1.45psi
So then three little lines will be approx 4.2psi, Not 4.4.
Spliting hairs, but then that is what you asked. Besides if I was a spec off someone out there would fry me for it.

One other thing, you will mostly drive in the negative area. If before you put the turbo on it read a negative number of X when you drive down the road at a steady 60mph then that is what it will still read. Thus showing that the same power is being used.

You will only go positive when more power is being produced. Note though that you never got to 0 even at full throttle prior to the turbo. A very slight vacuume was present, therefore the boost you are getting should be read from that number for your total.

Fanman

14.5 psi vs. 14.7 psi = semantics. I guess you want to be completely accurate. Thanks for the explanation though.