Are all pressure gauges the same?

mistareno

mistareno

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As the title suggests, would a fuel pressure gauge register air pressure accurately?

I notice most industrial type gauges state that they will work with oil/air/any fluid that will not corrode the device?

I just need a simple small pressure gauge for boost (it doesn't need to be hyper accurate as it's not for setting boost, just for secondary indicator).

There are several 1 1/2 fuel pressure gauges and industrial pressure gauges around but no 1-1/2 inch boost gauges...
 
Pressure Gauge

Hi Mistareno

Yes it should work o.k.
You will probably need a gauge with a range of 0 to 20 PSI (0 to 140 KPa)
 
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Yes all are the same. They work by means of a Bourdon Tube. It is an oval tube bent in a halfmoon shape. With pressure inside they try to go straight, almost like these blow whistles kids have at parties where you blow into it and it rolls out.
On the end of the tube is a linkage mechanism that activates a little rack and the needle have a pinion that deflects and give you the press. All pressures (water or air) deflect the same amount for the same pressure.
Frans
 
G'day Richard,

agree with the others, except that in our plastics age you may find active elements that are of the space age wonder material :)

Arrange your feed tube so that it naturally drains away from the gauge to get rid of any condensates that may cause you grief. Sometimes gauge feeds are arranged with a syphon in the tube with a "friendly" fluid in the syphon but you shouldn't need to go to that extent.

cheers,
Bob
 
COL said:
Hi mistareno

Yes it should work o.k.
You will probably need a gauge with a range of 0 to 20 PSI (0 to 140 KPa)
Click to expand...

Thanks for that, I had almost convinced myself that it would be okay, so thanks for the confirmation.

I can get one gauge that is 0-15psi or another that is 0-30psi - I think the Fuego would have a meltdown if I tried putting anywhere near 30psi through it so I should be safe with the 15psi version :D

This is the 30psi gauge -
%21Blo8jHwBWk%7E$%28KGrHqYH-D%21EtFg13Q-GBLcdhVEyd%21%7E%7E_12.JPG
 
Richard

At one stage I was offered half a trailer load of aircraft boost gauges to sell on behalf of Hughes Trading that was then located in Sydney Road. I took some of them to Bendigo swap meet to try and sell, but found no interest at all from buyers, so returned them to Hughes trading. Bill Hughes relocated to the Kyneton area and for a while operated a disposal place in one of the main streets.

I have the feeling that Bill may have passed on, as a few years later a lot of his old aircraft and motor vehicle stock was being sold at Bendigo swap meet.

As you know the Kyneton area well, you may be able to locate the family, they had a property near Kyneton with a large shed and relocated a lot of stock there as the Coburg business was wound down, they may still have lots of unusual items including some of the boost gauges etc.

Ken:)
 
Kenfuego said:
Richard

At one stage I was offered half a trailer load of aircraft boost gauges to sell on behalf of Hughes Trading that was then located in Sydney Road. I took some of them to Bendigo swap meet to try and sell, but found no interest at all from buyers, so returned them to Hughes trading. Bill Hughes relocated to the Kyneton area and for a while operated a disposal place in one of the main streets.

I have the feeling that Bill may have passed on, as a few years later a lot of his old aircraft and motor vehicle stock was being sold at Bendigo swap meet.

As you know the Kyneton area well, you may be able to locate the family, they had a property near Kyneton with a large shed and relocated a lot of stock there as the Coburg business was wound down, they may still have lots of unusual items including some of the boost gauges etc.

Ken:)
Click to expand...

Thanks Ken, that might come in handy.

I'm using the smaller 40mm gauges so I can hopefully fit 2 gauges a shift light and a couple of warning LED's all on a pod attached to the top of the steering column.

With 40mm gauges (1-1/2") I will still get a good view of everything on the dash except the oil level gauge (that I don't really use anyway) and all the info will be in close clear view which should make up for the fact that the gauges are small.
 
Pressure Gauge

Hi Mistareno

If you are only running low boost like 7 PSI a 0 to 15 PSI gauge would be fine
 
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COL said:
Hi mistareno

If you are only running low boost like 7 PSI a 0 to 15 PSI guage would be fine
Click to expand...

Yeah, 15 psi would be the absolute outer limits of boost for what I have planned.

At least with the 15psi gauge, it will probably be using a fair portion of the gauge sweep which should make it a bit more accurate / easier to read at a glance.
 
Pressure Gauge

mistareno said:
Yeah, 15 psi would be the absolute outer limits of boost for what I have planned.

At least with the 15psi gauge, it will probably be using a fair portion of the gauge sweep which should make it a bit more accurate / easier to read at a glance.
Click to expand...

Yep that is correct
 
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mistareno,

One issue to keep in mind when using gauges sourced from wherever is that gauges are calibrated in two standards - Gauge or Absolute pressures.

Gauge calibration starts from zero (at mean sea level), but Absolute starts from 14.7 PSI. If you select an instrument from any source you may pick up either of the two. If the latter it will read nearly 15 PSI with no input at sea level, but it may also be far more accurate than the alternative over its range. Any attempt to reset the pointer to zero will stuff up the accuracy of the instrument.

Regards,

fento
 
fento said:
mistareno,

One issue to keep in mind when using gauges sourced from wherever is that gauges are calibrated in two standards - Gauge or Absolute pressures.

Gauge calibration starts from zero (at mean sea level), but Absolute starts from 14.7 PSI. If you select an instrument from any source you may pick up either of the two. If the latter it will read nearly 15 PSI with no input at sea level, but it may also be far more accurate than the alternative over its range. Any attempt to reset the pointer to zero will stuff up the accuracy of the instrument.

Regards,

fento
Click to expand...

The gauges I have been looking at have a needle pointing at zero, so I assume they would be the simple gauge calibration type.
 
Maybe a bit "over the top" but I would not recommend using a mechanical boost gauge located in the cabin of the car. If you do, use quality hose and fittings to avoid leaks or hose blowing off, due to the possibility of injecting flammable air mixture into the car.

An alternative, and I think used on production vehicles, is an electrical gauge operated by a sensor in the manifold, which avoids any physical possibilty of gas in the cab.

Just a thought.
 
mistareno said:
Yeah, 15 psi would be the absolute outer limits of boost for what I have planned.

At least with the 15psi gauge, it will probably be using a fair portion of the gauge sweep which should make it a bit more accurate / easier to read at a glance.
Click to expand...

In that case you will need one with a bigger scale. A Bourdon tube gauge should only be operated to ideally 2/3 of its scale and worst case 3/4. Otherwise the tube becomes stretched or distorted and you lose accuracy and the needle may end up not returning to zero. If you need greater reading accuracy, you choose a larger dial face.

If due to boost control valves, waste-gates, etc. you ever see sudden changes in pressure then you need to fit a snubber to the gauge. This is a fitting that screws onto the inlet nipple of the gauge and contains a scintered filter or tiny orifice. These restrict gas flow and slow down the response of the needle. Without a snubber, sudden pressure changes can damage the Bourdon tube or cause the needle pinion gear to jump some teeth on the rack. This then throws the calibration out and the needle doesn't return to zero. Industrial gauges sometimes go one step further and the body of the gauge is sealed and filled with clear oil to cushion internal movement.

If the turbo is pushing through the fuel injection body or carby and you tap your pressure before fuel is admitted, there is obviously no need to worry about petrol vapour being blown into the cabin if the hose leaks or comes off. But if it taps in after fuel is admitted, then it's a real hazard as Fordman has described. But this can also be overcome using another common industrial component. A fitting containing a diaphragm is installed at or near the tapping point and the tube between it and the gauge is filled with a light oil - often silicone oil. The air pressure moves the diaphragm and the pressure is transferred to the incompressible oil which operates the pressure gauge.
 
Hi to anyone who can help!

Just resurrecting this old thread to ask the same question again - would a pressure gauge setup designed for recharging car airconditioning units (freon or R32 gas) be able to be adapted to test the pressure of Castrol Transmax F fluid (auto transmission fluid) in our Citroen GS? It has a torque converter that should run between 95 and 145 PSI and there is a removable bolt (metric of course) that allows you to check the pressure of the torque converter pump (at 5000 rpm and at idle).

I imagine I can rig up a metric male hollow "plug" to 1/4 inch female tube via some hose "somehow" (no lathe etc skills here).

I can see quite cheap gauges on Amazon/ebay e.g.:

457DF87B-A1F4-40EE-8689-1444502B964F.jpg



Comments welcome! Are there other kits not costing hundred of $$$$ that may give me a metric pressure gauge off a metric male threaded connector? It would be between 8mm and 11 mm thread.

thanks and best wishes for Merry Christmas to all froggers!
regards Leconte
 
Leconte said:
Hi to anyone who can help!

Just resurrecting this old thread to ask the same question again - would a pressure gauge setup designed for recharging car airconditioning units (freon or R32 gas) be able to be adapted to test the pressure of Castrol Transmax F fluid (auto transmission fluid) in our Citroen GS? It has a torque converter that should run between 95 and 145 PSI and there is a removable bolt (metric of course) that allows you to check the pressure of the torque converter pump (at 5000 rpm and at idle).

I imagine I can rig up a metric male hollow "plug" to 1/4 inch female tube via some hose "somehow" (no lathe etc skills here).

I can see quite cheap gauges on Amazon/ebay e.g.:

View attachment 128782


Comments welcome! Are there other kits not costing hundred of $$$$ that may give me a metric pressure gauge off a metric male threaded connector? It would be between 8mm and 11 mm thread.

thanks and best wishes for Merry Christmas to all froggers!
regards Leconte
Click to expand...

Why not buy this gauge?

https://www.ebay.com.au/itm/Pressur...655439?hash=item48dbb40d0f:g:T58AAOSw7t9eDd6Y

Its cheaper and comes with 1/4 BSP fitting and there is an option of 4 pressure ranges. You could use either 0 to 145 PSI or 0 to 230 PSI.
I think it would be far better suited to your application.
 
You have not said where the gauge needs to be sighted from....the engine bay or the drivers seat.
If it is a simple engine bay job, It is fairly easy to grab a bolt that will match, drill it with a hand held drill, and tap a thread and screw a gauge in.
Shops like pirtec have a dizzying array of adaptors and converters also.

Jo
 
Hi Leconti :)
That gauge Col referenced would be good in what ever range you need. Leave a bit extra in case !!
The easiest way to do the hose required to reach from the tapped 'hole' to putting the gauge where you can see it, would be a bit of air hose. That will be OK at that pressure for testing. You can get fittings that have a thread on one end and a barb on the other to suit inside a hose. Available in a large range of thread and barb combinations. Go to a hydraulic hose shop or an air conditioning trade supplier. They both have a range of fittings( the a/c shop will be cheaper !). Use some air hose and some small hose clamps. Plumbing shops are unlikely to have 'odd' fittings.
Find out the metric plug/bolt size and thread pitch first or take it in. If you use a gauge with a 1/4" male thread then you will need a 1/4" socket to fit that and fit a threaded barb. Easy to get the bits if you are in the right shop.
Jaahn
Here is the type of barbs you need (in whatever sizes you need).
1608843641232.png
 
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G'day,
I thought that metric pipe threads are BSP - the US have their own NPT... :)
The Aldi metric tap & die set comes with a couple of small BSP taps.
cheers,
Bob
 
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