Joined: Fri Jun 20 2008, 10:37PM
Location: Sydney Australia
Posts: 221
Found this on the Areomotive FAQ page...should have gone there first I guess!!
5. My regulator doesn’t seem to keep consistent pressure, every time I look at the gauge it reads something different, it’s driving me crazy, what is the problem?
Chances are good you have a liquid filled fuel pressure gauge, infamous for changing its reading with temperature. Because a liquid filled gauge is sealed to keep the liquid inside, the pressure inside the gauge case may not be equal to atmospheric pressure. Once sealed shut, the liquid in the case expands and contracts as gauge temperature changes, making the internal pressure in the gauge vary up and down as it heats and cools. Case pressure can change as much as 7 psi up and down with heat, which affects the gauge mechanism and changes the gauge reading by the same amount! - See more at: http://aeromotiveinc.com/frequently-asked-questions/faq-carbureted-regulators/#sthash.GyMbCVZm.dpuf
Joined: Thu Mar 22 2007, 08:13AM
Location: In the workshop
Posts: 1063
I personally would disregard the information on the Aeromotive page. Liquid filled gauges (in industry) are used because of greater accuracy, plus reliability under adverse conditions. Back when I was using them - about 10 or so years ago - even the worst had an innacuracy of 5%. At a reading of 6psi, that would be about 0.3 psi incorrect.
Sounds to me as if Aeromotive are making excuses for poor quality gauges.
Joined: Sat Aug 19 2006, 05:03PM
Location: Ontario, Canada
Posts: 2919
That is the way my liquid-filled gauge behaves as well. As I said near the beginning of this thread, I have to "burp" the rubber plug on the back to ensure it is reading accurately.
If it is compared to the one in the photo in the quote, then the big difference appears to be the amount of liquid in the gauge. The pictured one is about half full, and the Wika has just a little bubble of air at the top. Thats the same as all the ones I have used, and suspect that the lack of fluid might be the cause of the innacuracy.
Of course, I can well think of other reasons as well...
Joined: Wed Nov 17 2010, 03:28PM
Location: florida
Posts: 1311
A return style regulator will help cool the fuel.the pressure should stay in the line for a bit then die off.the hard to start could be vapor lock as mentioned.does it start right up after a cool down , or still hard?
Joined: Wed Nov 17 2010, 03:28PM
Location: florida
Posts: 1311
if upon startup the gauge reads what you want it to then it should maintain it even though it may read differently once hot ,the oil will cause this.i have a non oil filled mounted on my regulator for this reason.not sure if heat will cause diaphram in your regulator to fluctuate too mucn.i have an aeromotive regulator mounted in back of my motor which one would think would be hot but i got no probs.i run 1/2 fuel line which provides more fuel in line which will stay cooler before the under hood temps effect it along with a return to keep pump cooler.an overworked pump will run hot and heat your fuel before it even makes it to the motor. .with that said, i mentioned earlier I've got a $500 pump with a $200 bypass regulator and $100 + worth of fuel line feeding a $300 carb.you mentioned a race carb but that regulator and pump may not be suitable to feed it.i have learned that its safer to over pump than over carb.i only need 800cfm to make 600hp but i need a pump to supply 300+ gph to make that happen.