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Old 02-02-2007, 08:09 PM   #2
👏 Big Ron 👏
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Any gauge dangers? Under no circumstances should you use a mechanical gauge inside your passenger compartment that measures flammable fluids such as oil or fuel. Boost is 100% fine, but anything with fluids just doesn’t make sense.

Where do I mount my gauges? That depends on you. There are many solutions for the different size and type gauges, some out in the open, some stealthier than others. The popular mounting solutions are A pillar mount, steering column mount, speedometer bezel mount, clock mount, left hand driver’s A/C duct mount, glove box mount, vent mount, and of course, custom mounting. Most mounting options require some arts and crafts skills to get to fit right though. This means that you may need to perform some sanding, double sided taping, dremeling, or other slight handyman actions in order to achieve a perfect fit.

This is an example of excessive, compulsive gauge madness. The good thing about it, is that it shows every major gauge mounting area except for the single steering column mount, the glove box mount below, and the vent mount below that.

How do I convert BAR or PSI to whatever? Unit measurement is very important and should be given due consideration when gauge shopping. While having a quality JDM gauge may make you the cool kid on the block, the BAR to PSI conversion can drive you nuts. Hence the popularity of people switching from the perfectly good stock Lamco boost gauge that reads in mPa to an aftermarket PSI reading unit. The easiest way to convert these figures is to (for example) type 14.7 PSI into BAR in and let it do the conversion for you with its built in conversion ability.

What about making my gauges dimmable? The links of interest below has some tips. It is also worth mentioning that the Subaru dimming circuit is non-standard since it is fixed positive/variable negative. Most electrical gauges are wired for the opposite, fixed negative/variable positive. This can cause problems if they are connected to the car's dimming circuit. Such gauges that share a ground for measurement and lighting must NOT be connected to the variable illumination wiring. To install such gauges so that they dim, an additional circuit is needed to "flip" the polarity of the illumination to the gauge.

What gauges match my OEM color scheme? Several manufacturers make gauges to mimic the WRX or STI color scheme, you'll have to search which manufacturers make gauges that match your interior. As well, some offer end user color adjustability that are worthy of looking into. There are ways to modify gauges to color match via new bulb condoms or by using a colored marker as well, though that takes some modification and research and is not everyone's idea of the correct way to get the gauges to look right. For really color particular people, this thread shows you how to mod your existing OEM components for a 100% identical color match.

What about senders? A sender is the term for the device that actually measures the output you are looking to monitor and sends the information to the gauge face. Not all senders are created equal. Top grade senders are sometimes referred to as "VDO style" and have 2 terminals on the top for a separate and true ground. The insides are also constructed different with higher quality material and tighter tolerances. Most senders are matched to the gauge. So XXX gauges should use XXX senders. You can use a sender from a different manufacturer and it will work, but the chances that the resistance curve is the exact same is slim, in this case, the gauge will be off by varying degrees.

BSP, NPT….what does all this crap mean? British Standard Pipe Thread and National Pipe Thread. BSP is the European standard, while American stuff runs on NPT. These are terms for pipe thread types and pitch. They can be complicated, especially since they are close in sizing so that you can easily confuse a tight fitting thread with the wrong pitch thread. If you need adapters of any kind, McMaster-Carr is considered the source.

What about the famous gallery plug? It is located on the aft portion of your motor, towards the passenger side, under the intercooler. It is a half dollar sized round plug with a 5/16" female hex head. The thread size once your remove the gallery plug is 1/8 BSP. This is a common location for oil pressure or oil temperature senders.

What the heck is a sandwich adapter? It is a machined aluminum piece that goes in between your block and oil filter. It is pre-tapped to allow you to run oil pressure and oil temperature senders into it.

Which is better for my sender, gallery plug or sandwich adapter? Either works fine, though in the end the sandwich adapter is generally easier.

When I start using senders, adapters, etc., what do I use to seal it up? Three Bond 1215 or similar silicone based gasket maker, though some have used teflon tape or anti-sieze compound as substitutes.

Can I replace my OEM boost gauge but keep its look/location? Yes. Due to the unusual mPa reading of the Lamco gauge, it is a quite popular swapout. In order to do so, many will replace it with a slightly larger unit and use the same housing. Grease for lubricant and a hair dryer to soften the housing are all that are required to install an aftermarket unit as they are usually just 3mm larger than the stock gauge. It take some work to get the new unit in there correctly, but it can be done.

What are the normal gauge readings? The below listed readings are for a stock vehicle. Built motors, tuning through engine management, etc. can change these readings. As well, your gauge manufacturer, sender manufacturer, sender location, etc. can affect these readings. The best advice if your readings vary from the “norms” listed is to track your readings to find out your specific readings and record them to show cold, normal, regular, hot, high, etc. Once you have plotted your specific norms, then you can rely on them to spot problems.

Boost: 15.9 PSI max 2015+ WRX, 13.3 PSI max 2009-2014 WRX, 11.9 PSI max 2008 WRX, 11.6 PSI max 2006/2007 WRX, 13.5 PSI max 2001-2005 WRX, 14.5 PSI max STi.
Oil Pressure: 100 PSI cold, 20-40 PSI normal.
Oil Temperature: Cold = outside temperature, 220 to 260 F normal
Coolant Temperature: Cold = outside temperature, 170-200 F normal.
Fuel Pressure: 30-48 PSI normal.
EGT: 1400 F normal cruising, 1600 F during spirited runs

What about odd-ball gauge like devices? Those are entering the market at an astonishing rate these days. The main ones to come on the scene are the OBDII based units, the most famous of which being the PSI3 unit. Other units, though too numerous to mention, include the COBB AccessPORT ver. 2 with its gauge feature, TurboXS DTEC system, the Defi HUD unit, and the HKS CAMP system. We can also lump one-off units like Knock lights, the Scanmaster 4 channel EGT set-up, etc. into this category. While many of these units are worthy of consideration, this FAQ does not detail every single unique “gauge-like product” on the market though the more popular ones are listed via this question.

Links of interest:

Pics thread for gauge installs
Boost gauge install
Boost gauge install
Boost & A/F install
Oil pressure gallery plug
Oil pressure
Oil pressure sender
Oil pressure
oil pressure
Oil temp
sandwich adapter
OEM 3 gauge pod
EGT probe install
Dimming gauges
Dimming gauges
Misc gauge installation help
Gauge wiring, coloring, dimming

Editors Note

My thanks to Glenn from, Rich from, and Dan from for their input that provided a lot of the information contained within this FAQ.

This post was created because I wasn't able to find a good gauge FAQ. I came up with the text based on LOTS of searching here. Upon reading this you should have an idea of which gauges best suit your needs or not. The manufacturer is up to you.

If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, "I have XXX's gauge and it's great!" or "XXX's gauge broke after 1 month" are not appreciated here, that is what the Car Parts Review Forum is for.
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Last edited by Unabomber; 04-19-2015 at 01:58 PM.
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