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  #1  
Old 04-16-2008, 02:28 AM
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Default MAP & Boost ???

I picked up a scanGuage at AMVIV and have since been playing around w/ it. One of the readings that it spits out is the MAP sensor reading. All the manual says is that for turbo or supercharged cars this reading may be higher. Is the MAP reading in anyway related to boost? I have yet to get a boost gauge .... so I have nothing to compare.

Nik
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Old 04-16-2008, 02:50 AM
tlmcs05 tlmcs05 is offline
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Anything above 14.7 is boost. so if it reads 25 you are pushing about 10lbs of boost. There is a couple of threads floating about that have a formula that you can program in so it only shows above ambient airpressure but I was too lazy to mess with it on mine I can do the math pretty quick! LOL
I really like mine more than I thought I would. Waylon loaned it to me to keep an eye on some issues we were resolving, knowing full well I would have to buy it rather than give it back!

Tim
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Old 04-16-2008, 03:03 AM
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Thanks! I'll do some searches and see what I can come up w/.

Way tried that w/ me too!

Nik
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Old 04-16-2008, 08:14 PM
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MAP stands for Manifold atmospheric Pressure so yes if you boost this will be higher!!
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Old 04-16-2008, 08:22 PM
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I thought with MAP you subtract your atmospheric pressure (your current pressure above sea level) from the MAP #.

So for instance when I turn the key to accessory the ScanGuage turns on, and it'll read my Atmospheric pressure, we'll say 6.7. so, any thing over 6.7 is boost. So if I'm WOT and MAP reads 21.0 I'm doing 14.3lbs of boost.

or am I wrong? Which I tend to be.
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Old 04-16-2008, 08:33 PM
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yes and yes

I think what you said was right think as if you wee the guage your sitting after the boosting item at the manifold all you know is what pressure your reading at that current time... now lest think of how it got to you the guage. normal Atmo. presure as we know it is in Inches of Mg right somthing like 29.92 in well that obviously corosponds to PSI that gets sucked into your intake and then compressed and shot at your manifold where your sensor is. following that train of thought I waould say that your safe in your conclusion.



Some one please correct me if I'm wrong.
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Old 04-16-2008, 11:09 PM
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From the research I did since starting this thread, that sounds pretty close to correct. If you read the map pressure before the car is turned on (key turned, but not started) that is the atmospheric pressure, so then you should be able to subtract that # and get boost. You can actually program the scangauge to do the math for you. It will be just an esimate because if you change elevation the atmospheric pressure will change too. A real boost gauge would be better, but for rough boost its not bad.

Kinda fun though.

Nik
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Old 04-16-2008, 11:16 PM
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even "real" boost gauges are only reference. it will be with in a lb ussually
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Old 04-18-2008, 02:36 AM
tlmcs05 tlmcs05 is offline
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Unless your ears were bleeding, kinda doubt actual air pressure is 6.7
Engines suck, that is whay it is lower than ambient, ie vacume. It will often remember the last reading that was there at the time you cut it off (usually idle) . Try cranking the car (mine went to 6.7 at idle) then turn the switch off just enough to stop the engine but not the input from the circuits. (Watched mine climb to 14.4) The scanguage has no probes/inputs other than the cars existing system. Under engine braking in the NC mtns last week watched it drop to 2.3. Just more bits of useless info to clutter our brains! LOL
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Old 04-18-2008, 01:33 PM
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Quote:
Originally Posted by tlmcs05 View Post
Unless your ears were bleeding, kinda doubt actual air pressure is 6.7
LOL. I know I was just using it as an example. I think I am actually at 14.8.
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Old 04-21-2008, 03:21 PM
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neat. I learned something new.
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