rob-2 Posted August 23, 2013 Share Posted August 23, 2013 My gauge appears to be off at my altitude of 4500 feet. It's reporting, when motor off a negative 3-4psi. This results in my stated boost being off. While it appears to be consistent I'd rather it properly stated my boost. Does anyone know how to fix this? See pic. Link to comment Share on other sites More sharing options...
zanzabar Posted August 23, 2013 Share Posted August 23, 2013 your gauge reads 1 atmosphere or 14.5psi, so if you are pulling vacuum your guage is supposed to read bellow 0. when the car is idle it should be around -4 so it is right where it is supposed to be. when at full boost you should be at +14 +-.25, but it may read lower with your high altitude. Link to comment Share on other sites More sharing options...
1055 Posted August 23, 2013 Share Posted August 23, 2013 .. wat. A gasoline engine pulling 4inch of vacuum at idle would barely run. GOOD vacuum spec for most subaru motors at idle is 18-20inhg depending on the motor etc. I think its because there is no barometric adjustment for your gauge. Higher altitude = less than 1 atmos = readings like such with the vehicle off. Is the gauge mechanical or digital? If digital, there is no calibration? I'm not really sure that your gauge would be off under load. Probably only with KOEO. Boost pressure would remain constant regardless of where the gauge rests at barometric levels. I'm not sure how to put it into words.. At idle, what does it pull for vacuum? Note; below zero is inches of mercury, not PSI. Link to comment Share on other sites More sharing options...
rob-2 Posted August 23, 2013 Author Share Posted August 23, 2013 The motor isn't on here this is just power not idle. I have confirmed against ecu that the gauge is in fact off by 3-4 psi. When idle its reporting greater vacuum then shown. Can snap a pic in the am. Link to comment Share on other sites More sharing options...
1055 Posted August 23, 2013 Share Posted August 23, 2013 The motor isn't on here this is just power not idle. I have confirmed against ecu that the gauge is in fact off by 3-4 psi. When idle its reporting greater vacuum then shown. Can snap a pic in the am. So again.. is the gauge mechanical or digital? If its mechanical, its simply a diaphram operated gauge and your screwed. If its digital there's a good chance of there being a way of calibrating it. Also, are you sure its off by 3-4 psi? And the ecu isn't just correcting boost value based on baro pressure? Link to comment Share on other sites More sharing options...
JermTheElf Posted August 23, 2013 Share Posted August 23, 2013 Could be your sender. I would contact Defi. Link to comment Share on other sites More sharing options...
yardie Posted August 23, 2013 Share Posted August 23, 2013 Looks like an STRI gauge...? Link to comment Share on other sites More sharing options...
rob-2 Posted August 23, 2013 Author Share Posted August 23, 2013 Looks like an STRI gauge...? My mistake, you're right they are STRI gauges. So again.. is the gauge mechanical or digital? If its mechanical, its simply a diaphram operated gauge and your screwed. If its digital there's a good chance of there being a way of calibrating it. Also, are you sure its off by 3-4 psi? And the ecu isn't just correcting boost value based on baro pressure? It's electric, and according to what I read they re-calibrate every time they start up. Pictures below of the difference stages. So how does one calibrate it? Link to comment Share on other sites More sharing options...
rob-2 Posted August 23, 2013 Author Share Posted August 23, 2013 At idle Link to comment Share on other sites More sharing options...
rob-2 Posted August 23, 2013 Author Share Posted August 23, 2013 Motor off Link to comment Share on other sites More sharing options...
Mega Users LieutenantDan Posted August 23, 2013 Mega Users Share Posted August 23, 2013 I just got a new 60mm Performance Prosport boost gauge. I'm in Denver and mine reads just about exactly the same with the motor off. It won't read my tuned boost of 15psi. It only reaches about 12psi so I'm not sure if vacuum leak or altitude error. Mine is not adjustable. I've been doing lots of research and it seems like a common thing. If there is an adjuster that will work but some people report that their scaling is off afterwards. Link to comment Share on other sites More sharing options...
1055 Posted August 23, 2013 Share Posted August 23, 2013 Motor off Here's a good question.. where are you pulling your reading from? And that seems like a low vacuum idle.. is your car manual or automatic? I think you may have a bum sending unit.. Link to comment Share on other sites More sharing options...
rob-2 Posted August 23, 2013 Author Share Posted August 23, 2013 Here's a good question.. where are you pulling your reading from? And that seems like a low vacuum idle.. is your car manual or automatic? I think you may have a bum sending unit.. Pulling from a t connection off the BOV. automatic. From what I'm reading online this a common problem about 3000 feet Link to comment Share on other sites More sharing options...
yardie Posted August 23, 2013 Share Posted August 23, 2013 This [ame=http://www.youtube.com/watch?v=6D8AVr5Yz8A]Defi[/ame] boost gauge shows 0 boost at acc on, also on this set of [ame=http://www.youtube.com/watch?v=hAV-fML1XrI]Stri[/ame], could yours be trying to compensate for the difference in altitude after it does its sweep? Sorry for the huge youtube links i'm a newb at posting Link to comment Share on other sites More sharing options...
Mega Users LieutenantDan Posted August 23, 2013 Mega Users Share Posted August 23, 2013 And that seems like a low vacuum idle.. is your car manual or automatic? I think you may have a bum sending unit.. He said the motor was off... It's the gauge not compensating for altitude. It's calibrated at close to sea level so when the gauge is on and the motor is off it's indicating what it thinks is atmospheric pressure but the higher elevation causes it to read lower due to the lower pressure atmosphere. Link to comment Share on other sites More sharing options...
iNVAR Posted August 23, 2013 Share Posted August 23, 2013 His gauge is messed up, that's the only explanation. It's supposed to zero itself when he starts it, regardless of elevation. I too have read this is a common problem. Link to comment Share on other sites More sharing options...
rob-2 Posted August 23, 2013 Author Share Posted August 23, 2013 I've contacted my shop and the distributor to see about getting this fixed. Link to comment Share on other sites More sharing options...
Mega Users LieutenantDan Posted August 23, 2013 Mega Users Share Posted August 23, 2013 If the gauge zeros properly when no power is running to it (which mine does) indicates that it is operating correctly. If the gauge doesn't return to zero upon powering down then it is probably broken. Once the gauge is powered, regardless of whether the engine is running or not, should still read zero because it is now reading atmospheric pressure. So in regards to the elevation it was calibrated at, it is reading properly compared to its own zero value. It has nothing to do whether its operating properly or not, its the scaled zero value in the gauge itself. Although one thing I can't account for is that on my previous Prosport Premium mechanical boost gauge, it always read true zero. It read zero in VA and zero in CO. I did drive the car from VA to CO so maybe it scaled itself along the way. Where all the mile high gauges be at? Link to comment Share on other sites More sharing options...
iNVAR Posted August 23, 2013 Share Posted August 23, 2013 If the engine is running and it's powered, it should read vacuum. If the engine is NOT running and it's powered, it should read 0. It's not "operating" properly because it's not working the way it should. But this is just me arguing about the semantics/meaning of "operating". It's been suggested that the gauge itself isn't the problem but rather the sensor which sends the gauge data. Mechanical gauges don't have this problem because they simply measure pressure differential, and no electronics or calculations are involved. In theory, an electronic one that properly zeros itself to the ambient pressure shouldn't have this problem either. Link to comment Share on other sites More sharing options...
1055 Posted August 23, 2013 Share Posted August 23, 2013 At idle And that seems like a low vacuum idle.. is your car manual or automatic? I think you may have a bum sending unit.. He said the motor was off... Reading > you. Link to comment Share on other sites More sharing options...
RabidWombat Posted August 25, 2013 Share Posted August 25, 2013 Gauge is broken. According to this the nominal difference between sea level and 4500 ft is ~2.2psi. http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html Your gauge is reading low by like 5 psi. Its not an elevation thing. Link to comment Share on other sites More sharing options...
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