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I would think that it is a bad idea to use rubber hose instead of the hard plastic hose that comes with the guage. The rubber hose may be prone to expansion under pressure which would screw with its accuracy. Also check to make sure that the guage is zeroing out when the car is off. I have heard of people having problems with the needle on autometer guages not returning to zero, though I have never had this problem with my autometer guages.

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1995 Talon TSI fwd
 

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I recently replaced my -30 to 30 SPI boost gauge (b/c gauge was sticking) with an Autometer -30 to 30.

Where the SPI used to read 17psi, the autometer reads 22+. Can there be such a big difference among boost gauges?

I doubt this had anything to do with it, but rather than use the nylon tubing to connect the autometer gauge, I used rubber hose and fanegled it to connect it to the gauge nice & tight. The autometer responds very quickly & seems accurate.

Anyone have similar experiences with boost gauges or have any comments?
Thanks
Nick, NYC DSM
 

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another thing to consider is that your first gauge did fail. Would you really trust the readings from it? I'd say turn the boost down. Try and run the new hose and see if it changes anything. If anything i would think the harder hose would read even higher.
 

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the hose would not make a difference in the reading of the gauge... it just takes more air in the hose to reach the gauge as the hose expands. the harder hose will expand less and thus the pressure in the hose will equalize with the pressure in the throttle body faster.. to better explain.. try blowing in a balloon.. it takes more air for the balloon to exert back the air pressure you put into it (i.e. if you could blow exactly 2 atm's the balloon would expand a bit before exerting back 2atms worth of air pressure) were as if you blew into a glass with exactly 2 atms the pressure in the glass would almost immediatly reach 2atms with no expansion.. <------ what i learned in physics 201 but anyways, if your first gauge was already screwing up, you're gonna have to throw its reading out the window because it is already "tainted".

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J. Hunter Allred

'95 GS-T free mods, K&N, 3" HKS Superdragger, ACT2600, lightened flywheel, and otherthings that escape me at the moment. T-25 handicapped though. As you can see its a work in progress. Figure if i buy it i should buy it once :)
 

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Don't want to insult anybody here but don't overanalyze things. from the word of experience nylon hose sucks. It gets brittle and breaks over time. Even 30psi won't hurt a rubber hose. Expansion (if there is any) won't affect readings either nor response. Think about the volume inside even a 20ft piece of vac hose that small..it's insignificant. If anybody mentions pressure drop that only applies to air FLOW which a boost gauge does not do. If you guys really want to test a gauge out for accuracy hook it up to something accurate for testing...like a manometer. Doesn't get any better than that.
 
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