Why you shouldn't always trust aftermarket gauges.
02-13-2006, 12:29 PM
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Why you shouldn't always trust aftermarket gauges. IN the past few months, I've been noticing that my autometer gauge oil pressure gauge doesn't read very high. Oil of choice is Mobil 1 0w40. On cold startup (ie under 30 degrees) oil pressure was shown at around 37psi. Driving while under 150 degree oil temps the oil prssure would usually climb normally up to 50-60psi accelerating moderately.
However once the car got warmed up where the oil temps are in the 180-240 range (put 180 T-stat back in, remember I don't have an oil cooler) Idle oil temps (700-800rpm) where displayed as around 6psi (or half way between the 0 and 12.5psi mark on the gauge), and under WOT it never got above 37.5 PSI.
This kinda worried me. I started to disagree with the accuracy of the autometer gauge (electric not mechanical) I thought maybe dropping the sending unit had something to do with it. Although with the previous sending unit (got a new one when the old one was replaced due to fading words) it read the same. I also began to wonder if it was the gauge being how when 12V was applied the needle never zeroed out and always sat below the 0 Mark. I prolly could have gotten the Ohm meter out and tested read the resistance at different rpms, but the instructions don't tell you what resistance = what pressure.
So as many recommend to use a Mechanical Gauge to verify the pressure, that's what I did. So I asked my dad to make one up. Isn't she a beauty..
Gauge is a Wika Industrial Pressure Gauge. 0-100 psi in 2 psi incriments. 1.50% span accuracy, Glycerine filled.
So today I went ahead and unscrewed the autometer pressure sending unit from the back of the intake, and installed the "tester" guage my dad made.
It turned out to be a big surprise. With the oil temps slightly over 180* (just got back from driving) I had 16 psi @ Idle (800rpm) and on a rev to 4000rpm I had 46-48psi.
So just a reminder for everyone to always double check the accuracy of your gauges when in doubt
However once the car got warmed up where the oil temps are in the 180-240 range (put 180 T-stat back in, remember I don't have an oil cooler) Idle oil temps (700-800rpm) where displayed as around 6psi (or half way between the 0 and 12.5psi mark on the gauge), and under WOT it never got above 37.5 PSI.
This kinda worried me. I started to disagree with the accuracy of the autometer gauge (electric not mechanical) I thought maybe dropping the sending unit had something to do with it. Although with the previous sending unit (got a new one when the old one was replaced due to fading words) it read the same. I also began to wonder if it was the gauge being how when 12V was applied the needle never zeroed out and always sat below the 0 Mark. I prolly could have gotten the Ohm meter out and tested read the resistance at different rpms, but the instructions don't tell you what resistance = what pressure.
So as many recommend to use a Mechanical Gauge to verify the pressure, that's what I did. So I asked my dad to make one up. Isn't she a beauty..
Gauge is a Wika Industrial Pressure Gauge. 0-100 psi in 2 psi incriments. 1.50% span accuracy, Glycerine filled.
So today I went ahead and unscrewed the autometer pressure sending unit from the back of the intake, and installed the "tester" guage my dad made.
It turned out to be a big surprise. With the oil temps slightly over 180* (just got back from driving) I had 16 psi @ Idle (800rpm) and on a rev to 4000rpm I had 46-48psi.
So just a reminder for everyone to always double check the accuracy of your gauges when in doubt
