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Old 06-05-2006, 03:42 PM   #1
x99percent
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Default Hydra: What are you using to measure your boost level?

Since day one, I've noticed a discrepancy between the Hydra's boost reading and my three other boost-reading devices (gauge, EBC, and turbo timer). For example, during a pull, my boost level will hold at ~22psi as indicated by my other gauges, but the Hydra logs will only show ~19psi.

My real question is this: When people are tuning a Hydra-equipped car to "22psi", are they reading that "22psi" from a gauge or from the Hydra logs?
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Old 06-05-2006, 04:06 PM   #2
jblaine
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I've heard Phil mention before that the Hydra reads low.

Mine, for whatever reason, seems to pretty accurately represent what I see on my mechanical Omori boost gauge. It's tapped off the vac line at the front of the intake manifold behind and to the right of the PS pump.
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Old 06-05-2006, 05:19 PM   #3
Element Tuning
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Quote:
Originally Posted by jblaine
I've heard Phil mention before that the Hydra reads low.

Mine, for whatever reason, seems to pretty accurately represent what I see on my mechanical Omori boost gauge. It's tapped off the vac line at the front of the intake manifold behind and to the right of the PS pump.
Correct. The Hydra reads in "absolute" and will differ in readings taken from devices that read in "gauge" mode. It's typical to see about a 2 psi difference. My E-Boost reads very close to my Hydra but my Defi gauge is 2 psi higher. Changing the MAP sensitivity in the Hydra will also have an impact but setting it too sensitive will result in larger variations of the readings due to valve opening. You want to make sure itís a stable read as it impacts what load cells are utilized.

Thanks,
Phil
http://www.elementtuning.com
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Old 06-09-2008, 10:24 AM   #4
vids
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I also have about the same question. I actually have 3psi higher reading on my boost-gauge than in my GEMS ecu. The thing I wonder about is which one should I trust when mapping? The gems value is on the safe side of boost-pressure, but the gauge-value is a bit more brave.

I like to get the most out of the engine but still live a little space for errors and hot days. Those 3 psi actually represents some of that space that I may or may not have
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Old 06-09-2008, 09:05 PM   #5
bannerd
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I did a T from the intake manifold to my guage sensor. I think that is the most accurate results you will get. The AP also has a boost reader which is pretty accurate. I'm running DEFI guages which is crazy setup as it logs the highest recordings.
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Old 06-09-2008, 11:39 PM   #6
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I find the Hydra boost reading is similar to a AEM or other true MAP sensor absolute boost reading. I would rely on the Hydra over the typical boost gauge.

Many boost gauges read on the high side or at least that is what I have observed.

Try to look at your Hydra with the car off and compare to your barometric readings from NOAA.
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Old 06-10-2008, 08:07 AM   #7
vids
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Thanks! The barometric readings seem ok, so I guess I should trust the absolute map-boost readings. I have a 3 bar map-sensor, so I guess it would be quite accurate up til 2 bars or something like that?
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