onesillyracer Posted October 8, 2006 Share Posted October 8, 2006 Im in the market for a boost guage, but can someone enlighten me on whats the difference between the mechanical and electrical boost guages and what seems to be the better one to go with? Im completely clueless with this. Thanks! Link to comment Share on other sites More sharing options...
leggtnut Posted October 8, 2006 Share Posted October 8, 2006 clueless on which is better, but i had a mechanical one in the Baja T and have an electric one in the LGT. The differance is the mechaical has a vacume tube that goes from the engine to the guage and the electrical has a wire going from a sending unit in the engine to the guage. Ben (2014 Outback SAP w/ eyesite, 2014 Tribeca Limited, 2006 LGT limited sedan) Subaru Ambassador PNW Link to comment Share on other sites More sharing options...
zmarko Posted October 8, 2006 Share Posted October 8, 2006 I prefer mechanical, as (if I remember correctly) the electrical one relies on what your ECU sees as boost. The mechanical one uses a boost source (in my case I T'd off the CBV line). If I'm incorrect, please feel free to correct me. But this is what I remember from 7 or 8 years ago when I first researched boost gauges. Link to comment Share on other sites More sharing options...
biz77 Posted October 8, 2006 Share Posted October 8, 2006 Aftermarket electrical boost gauges still rely on a reading from a vacum line, but they use a sending unit (box installed in engine compartment) that accepts a vacum line from the engine and sends an electrical signal out to the guage which then interprets that signal into a meaningful pressure reading. Electrical gauges eliminate the need to run a long vacum line inside the car. Some mechanical boost gauges are also noisy, as they have pressure and vacum running into them to give a reading. Link to comment Share on other sites More sharing options...
Magic Posted October 8, 2006 Share Posted October 8, 2006 I prefer mechanical, as (if I remember correctly) the electrical one relies on what your ECU sees as boost. The mechanical one uses a boost source (in my case I T'd off the CBV line). If I'm incorrect, please feel free to correct me. But this is what I remember from 7 or 8 years ago when I first researched boost gauges. you are incorrect on the electrical. on an electrical, you tee off the engine a vacuum line. this vacuum line is then attached to a electrical sending unit. This sending unit the electrically, via a wire, sends an electrica lsignal to the gauge inside the car. Electrical is not sensing the ECU signal. Click Here everyday:redface: Link to comment Share on other sites More sharing options...
jim1969 Posted October 8, 2006 Share Posted October 8, 2006 electrical gauges tend to have alarms and peak holds whereas mechanical don't. Link to comment Share on other sites More sharing options...
mwiener2 Posted October 9, 2006 Share Posted October 9, 2006 you guys are missing the biggest difference... Mechanical $45-150 Electrical $125-300 or more My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
jazzymt Posted October 9, 2006 Share Posted October 9, 2006 I can tell you from extensive professional experience with pressure and vacuum gauges (not for automotive market), in general, mechanical guages can be very innacurate...even when specifically rated for a certain accuracy, i've found several of them don't meet their rating and some of them are nowhere near it. Conversely, except for very expensive mechanical instrumentation, electrical pressure transducers are much more sensitive, repeatable and accurate. Wiener hit the nail on the head though, they are also much more expensive on average... [CENTER][URL="http://legacygt.com/forums/showthread.php?t=18504"]Subaru Plug & Play Aux-in Mod[/URL][/CENTER] [CENTER][URL="http://www.jazzyengineering.com"]www.jazzyengineering.com[/URL][/CENTER] Link to comment Share on other sites More sharing options...
SSpeed Posted December 31, 2007 Share Posted December 31, 2007 For the price, I'll do mechanical from now on... I trust a needle way more than I trust electronics. Plus, being in Denver, I haven't found an electrical gauge yet that isn't way off... A mechanical boost gauge will calibrate at zero in reference to your local atmospheric pressure. Therefore, at sealevel you will make and show 15psi and at the top of Mount Evans you will show and make 15psi. 15psi won't be the same absolute pressure between the two locations, but it's the same relative pressure. An electrical gauge may or may not zero itself to the local atmospheric pressure, most I have tried don't... So sitting there with the key on and engine off, they'll read 5 inHg where I'm at... vacuum will be way off, peak boost will be way off... I still see faster needle readings and response time on the mechanical as well, even with the longer hosing required. If I'm going to have a boost gauge, I want it to be accurate. I don't want it to show as much as 4psi peak boost differences between places I am driving to... I don't know why I deviated from the tried and true mechanical boost gauge I've always used and spent bigger money to try an electrical one... maybe it was the fancy opening ceremony, but lessons learned, use mechanical... Link to comment Share on other sites More sharing options...
Underdog Posted December 31, 2007 Share Posted December 31, 2007 For the price, I'll do mechanical from now on... I trust a needle way more than I trust electronics. Even digital circuits are made from analog parts. There is nothing magical about a pressure transducer. The Crimson Dynamo Link to comment Share on other sites More sharing options...
J-Cobb Posted January 7, 2008 Share Posted January 7, 2008 A boost gauge is a pressure gauge that indicates manifold air pressure or turbocharger or supercharger boost pressure in an internal combustion engine. They are commonly mounted on the dashboard, on the driver's side pillar, or in a radio slot. Turbochargers and superchargers are both engine driven air compressors (exhaust driven or mechanically driven, respectively) and provide varying levels of boost according to engine rpm, load etc. Quite often there is a power band within a given range of available boost pressure and it is an aid to performance driving to be aware of when that power band is being approached, in the same way a driver wants to be aware of engine rpm. A boost gauge is mandatory when boost pressure is being modified to levels higher than OEM standard on a production turbocharged car. Simple methods can be employed to increase factory boost levels, such as bleeding air off the wastegate diaphragm to 'fool' it into staying open longer, or installing a boost controller. To avoid excessive leaning out of the engine (caused by increasing the boost beyond the fuel systems capacity) care must be taken to monitor boost pressure levels, along with oxygen levels in the exhaust gas, using an oxygen sensor. A boost gauge will measure pressure in either psi or bar and many also measure manifold vacuum pressure also in inches of mercury (in. Hg). Can also be displayed as mm of mercury (mm Hg). Link to comment Share on other sites More sharing options...
SSpeed Posted January 7, 2008 Share Posted January 7, 2008 Unless the electrical gauge zeros to atmospheric pressure on power up (engine off), and the two I've tried don't, your readings will be all over the place and never consistent. You'll be reading a pressure number calibrated from absolute pressure at sealevel during ideal conditions. Buy mechanical... Link to comment Share on other sites More sharing options...
Spec B Posted January 7, 2008 Share Posted January 7, 2008 IMO, the biggest advantage to electronic boost gauge over a mechanical one is the ease of install. It is alot easier to route cables into the dash than it is to route a vacuum hose. Any crink in the vacuum hose (behind the dash) and the mechanical boost gauge will not display boost accurately or worse yet it may even leak boost (it happened to me). Also, some electronic gauges also gives you the startup sweep and peak boost recall/warning... Link to comment Share on other sites More sharing options...
g2redgsr Posted May 9, 2008 Share Posted May 9, 2008 my friends got a mechanical auto-meter or auto-gage form autozone for 40 bucks, any good? thinking about picking that up, you think it will be accurate? 40 bucks is 40 bucks Link to comment Share on other sites More sharing options...
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