A 'boost' gauge is a pressure gauge that measures pressure (and, usually, vacuum) at the intake manifold. Ordinary vehicles only ever have vacuum at this location, as the engine attempts to suck in air. Turbocharged and supercharged vehicles pressurize the intake manifold by pushing in extra air. The intake pressure is referred to as 'boost'.

It is essential to have a boost gauge prior to modifying the turbocharger system on a turbo DSM. If the turbo is not set up correctly, it will push in more air than the engine can handle. This usually leads to a 'lean' condition - too much air, not enough fuel - which directly results in excessively high combustion temperatures and severe engine damage. For this reason, a boost gauge is always at the top of any DSM modifications list.

Non-turbo DSMs, having no turbo, have no need for a boost gauge. However, it is essential if the car is retrofitted with a turbo or supercharger system.

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How do I install a boost gauge in my [DSM]?

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You would already know this (hint, hint) if you had checked the FAQ Locator, since Brad Bauer and Todd Honea have graciously written up the process. You can also check the archives.

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An air/fuel ratio (or A/F) gauge is a voltmeter attached to the oxygen sensor signal wire. The oxygen sensor reacts to the amount of air present in the exhaust stream, and provides an approximate indication of the relative amounts of air and fuel in the combustion mixture. It is a useful tuning tool, although limited somewhat by the characteristics of the oxygen sensor it is attached to.

There are many A/F gauges on the market. Those for DSMs usually read from 0-1V, although newer models may measure a restricted range similar to 700-1000 mV.

Because the A/F gauge is merely a voltmeter, many people have adapted existing equipment or built their own, rather than pay retail prices. One such design is provided free of charge by Brad Bauer, and is based (as most are) on the National Semiconductor LM3914 bargraph display driver IC.

Some DSMers have also offered their homebuilt units to other club members at lower prices. These offers are usually temporary.

For technical information on some of the drawbacks and limitations of DSM oxygen sensors, see this post by Dave Mertz; be sure to read the reply at the bottom from Todd Day. Also check out the oxygen sensor questions in this FAQ.

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What is an A/F meter? Has anybody ever installed an A/F meter on a [DSM]? How do I install an A/F meter on a [DSM]? I can't find the O2 sensor wire! Where is it?

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An A/F meter is simply a voltmeter, hooked up to the oxygen sensor. Most A/F meters are simple bar-graph displays, although some have LCD displays. Since the

Installing an A/F meter is as simple as connecting the meter to power, ground and the oxygen sensor signal. Owners of precise meters will want to be certain to get a good ground, since ground offsets may affect the A/F meter readings.

1Gs have a test connector, located in the passenger side of the dash, that is useful for A/F meter connections. This wire can be located by following the directions on Brad Bauer's O2 sensor wire VFAQ.

2G owners need to connect to the ECU wiring in order to monitor A/F ratios. You can find the correct wire by reading the hawaii.dsm.org 2G A/F install How-To.

The Last Word: A/F gauges are pretty, and pretty useless. Get a real way to measure your engine.

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An EGT gauge measures (ahem) exhaust gas temperature. This reading is directly related to the internal combustion temperature of the engine, and indirectly related to the quality of the air/fuel mixture entering the engine.

The principle is obvious: if the engine gets too hot inside, parts melt. While other gauges can give an indirect indication, only an EGT can give a direct indication that the engine is operating correctly.

EGT gauges consist of a high-temperature thermocouple (usually K-type) attached to a analog or digital readout. A hole is drilled into the chosen measurement location - exhaust manifold, oxygen sensor housing, or downpipe. The thermocouple is placed inside the using air-tight compression fittings. Simple bandclamps can also be used, but only on downpipe installations - they are not air-tight and will allow exhaust to escape.

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You would already know this (hint, hint) if you had checked the FAQ Locator, since Tom Stangl and Brad Bauer have both written up procedures.

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Where should I tap/install my EGT probe?

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There are several places to install the EGT probe. However, EGT readings will vary depending on where the EGT probe is mounted, as pre-turbo EGTs are always higher than post-turbo EGTs.

Installing the EGT in the exhaust manifold is the preferred method. It is also one of the easier methods, since the manifold is easily accessible.

Although the 'traditional' manifold mounting point has been cylinder #1, recent information from Team Rip Engineering shows that the #2 cylinder is the hottest of the four. Recommendations for the distance between the probe and cylinder head range from 1 to 6 inches.

Another possibility is to install the probe in the manifold 'collector' - the place where all the runners converge. The idea here is to get an average reading of how all four cylinders are running, rather than a specific reading on one cylinder. Some people believe this is safer since you can monitor the entire engine. There is a good write-up on the difference between runner and collector placements here, courtesy of Steve Wells, that can help you decide between the two.

Other possibilities include the oxygen sensor housing and the downpipe. Diamond-Star Specialities doesn't recommend the oxygen sensor housing because the temperature drop between the manifold and the housing varies from car to car. Read about this here.

For downpipe installations you don't need a compression fitting, since a small exhaust leak at that location really doesn't matter. Also, if you accidentally drill a hole in the wrong location, it is more easily repaired. Unfortunately, the downpipe is fairly far removed from the engine, and only readily accessible from underneath the car. One solution is to have the probe pre-installed when upgrading or replacing the downpipe.

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Many of the older pages referring to the poorly-named 'knock LED' modification are now gone. Any new ones will be found at faqs.dsm.org.

If you can't find any instructions on how to do this mod, don't worry too much. The 'knock LED' does not really measure knock. The author of these pages would like to think that the knock LED FAQs faded away because DSMers in general realized just how awesomely useless and misleading this modification really is.

For more information on what the knock LED will (not) do for you, please see "What is a knock LED?" in this FAQ. If you really feel you need one, use the results of this search to help find some current pages.

The Last Word: Don't waste your time.

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No, it will not work.

First of all, the knock sensor for a DSM engine is nothing more than a microphone. It picks up engine noise - all of it. There is no signal processing or filtering. The output signal is difficult to interpret, to say the least. It is not possible to hook up an LED, DMM, digital display or any other form of indicator directly to this signal.

The ECU is responsible for processing this signal and getting useful information from it. The results do not exist outside the ECU memory. So, to measure knock as the ECU does it would be necessary to duplicate the ECU's signal processing algorithms.

To make things more interesting, the ECU only 'listens' for knock in certain portions of the engine cycle. So timing would have to be known as well. A short, comprehensive explanation of some of the difficulties can be found in this post by John Hopkins.

It is far easier for most people to simply purchase a datalogger or Pocketlogger. These instruments will read the correct knock sums directly from the ECUs memory.

The Last Word: Ages ago, there was a way to hook up an LED to the knock sensor "microphone" using a threshold detector. The LED would light up - sort of - when the signal from the microphone got "loud" enough, which supposedly indicated knock. Cute, but not necessarily a good idea.

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TMO gauges are a feature of the Technomotive ECU upgrade for DSMs. The upgrade reprograms the useless stock boost gauge on turbo models to display any of five different measurements, such as timing advance and injector duty cycle.

The Last Word: TMO stopped selling chips a long time ago. Anyone who claims to be selling their stuff under license is a big fat liar.

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You would already know this (hint, hint) if you had checked the FAQ Locator. The process is the same for colored, indiglo and reverse indiglo gauges.

Those interested can also check out the install instructions from Black Cat Custom, a manufacturer of custom gauge faces for DSMs in both Canadian and American versions.

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Many people have done this. It is not difficult to do. The process is essentially the same as installing white faces, described above.

Converting the stock needles to a different color simply involves scraping the orange paint off of the bottom of the needles. They can then be repainted in any color. The backlighting color may also be changed. There is a VFAQ on the process here; also try the results of this Google search.

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Maintained by Sean Costall. Changes and suggestions are welcomed!  If you have any information on the answers to any of these questions or wish additional questions, please mail me.

This page is an extension of Club DSM .