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gauge usage/reading/warnings faq?


jholder

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Since you guys were super helpful on my last post....

 

Is there a gauge FAQ?

 

For instance, I just installed a boost gauge. My understanding is that it measures the pressure inside the intake manifold, the pressure being generated by the turbo forcing air in.

 

What I'm looking for is a list of various gauges (types not brands).

What they do

Warning signs

Proper readings

 

 

For instance, oil pressure gauge (i think this is how it performs).

Measures the pressure in the engine oiling system.

It should normally read XX lbs/sq. in.

If higher then blah blah

if lower then blah blah

Normal causes for low readings are blah blah

Normal causes for high readings blah blah.

 

 

 

I was thinking some of the most common gauges. I think most people get the boost/oil pressure/EGT combo.

 

 

Thanks in advance.

 

 

--james

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Hmm, I'll take a shot at this, and hopefully someone better qualified than I can come in and fill in the rest. These aren't really in a particular order right now, just as I thought of them

 

 

 

Boost/vacuum Gauge

 

Purpose:

 

(taken from http://www.jumptronix.com/2g_go_faster/Stages/details/BoostGauge.htm )

"Well pretty simply a boost gauge displays the pressure in psi or bar (kg/cm2) at the intake manifold. Some read absolute pressure (relative to a perfect vacuum) and others read gauge pressure (relative to ambient atmospheric pressure). There are tons of arguments on which is the better to use to monitor your charge air system. The reality of the situation is that in this authors opinion the arguments just don't matter. The differences touted by both sides of the argument are minor enough, other variables extensive enough, and our tuning rough enough that it just doesn't matter. More so most boost gauges (all mechanical I know of and most electronic) all operate off gauge pressure anyway."

Someone may want to come in and correct me if I make a mistake with this next bit. Without the turbo running boost into the intake manifold (and by extension the cylinders themselves) the engine must rely on the vacuum created in the cylinders after detonation to to pull the air/fuel mixture into the cylinder from the manifold. So under normal circumstances, their should be a vaccum in the system, to pull the a/f mixture in to the cylinder. As the turbo begins to spool (and under load I might add) it starts to force air into the manifold, at some point (reference anyone?), the pressure the turbo creates overtakes the suction from the cylinder, and the pressure in the intake manifold shifts from a vacuum to a positive pressure (lovingly known as boost).

 

What the boost gauge (mechanical or electrical with a sending unit placed in the intake system) gives us is a view into this system. The OBDII port should list the manifold pressure, but from what I understand it uses an average based off of the MAF sensor, not from a true boost sensor. With the turbo not engaged, we should see vacuum, when the turbo kicks in, we should see boost. (on a side note, from my personal experience i see vacuum-vacuum-vacuum-vacuum-BOOST!!!... literally, I watched it today, under normal acceleration its stays in vacuum, then all of a sudden, the needle shoots over to boost.. actually its kind of neat :D )

 

 

Better info from an LGT'er

 

http://www.legacygt.com/forums/showthread.php?t=16620

 

 

What do these readings mean/Why are they important:

 

again taken from http://www.jumptronix.com/2g_go_faster/Stages/details/BoostGauge.htm)

"There is a very good reason to need to know the boost level going into your motor. Most importantly if you try to run too much boost into the motor for a given fuel octane and given compression ratio you will at best suffer from bad timing and at worst damage your motor. The details of all this will eventually be discussed in a section dedicated to engine management and tuning, but for now you just need to know that too much boost is bad and too little it slow. Having a gauge allows you to set and then monitor the boost level. Monitoring is needed, rather than a set and forget method, because shit happens, and as you start to push the car closer to the edge and negate/reduce the effectiveness of stock fail safes you have to keep a closer eye on the operation of your engine.The result of over boosting will be detonation and eventually catastrophic damage."

 

 

 

From my standpoint, as a pontential modder, I like the idea of keeping tabs on my boost. I'd like to know how its behaving, and if a map change is working and making as much boost as I think it should. Since I personally want to tackle the suspension before going to the engine, honestly, its just bling. But I'm ok with that. :)

 

From a stocker stand point... I'd be willing to say this is almost always bling in a stock vehicle, but there is something about nailing it, and watching that needle shoot up... heh

 

 

When to worry:

 

If the gauge is in working order, your car is stock, and you're seeing 13.5 ( i don't know, anyone care to hazard a guess.. 13.5 is supposed to be the max stock boost.) pounds of boost. I'd not be worried because of the amount of pressure, but because you shouldn't have more than that with a stock map.

 

 

You're in gear AND moving (ie. engine under load), lets say you're at 4000 rpm and you're still showing vacuum (and of course there is no power increase).

 

 

 

Legacy Specific Reference

 

Normal Readings:

 

(For Factory ECU Map) MAX: 13.4 psi

Max In 1st Gear =

Max In 2nd Gear =

Max in 3rd Gear =

Max in 4th Gear =

Max in 5th Gear =

Max in 6th (Spec. B) =

 

Cobb Stage 1

Max In 1st Gear =

Max In 2nd Gear =

Max in 3rd Gear =

Max in 4th Gear =

Max in 5th Gear =

Max in 6th (Spec. B) =

 

 

Cobb Stage 2

Max In 1st Gear =

Max In 2nd Gear =

Max in 3rd Gear =

Max in 4th Gear =

Max in 5th Gear =

Max in 6th (Spec. B) =

 

 

 

TDC

Max In 1st Gear =

Max In 2nd Gear =

Max in 3rd Gear =

Max in 4th Gear =

Max in 5th Gear =

Max in 6th (Spec. B) =

 

DIY Install Instructions:

 

 

 

 

2) Oil Pressure Gauge

Purpose:

 

What do these readings mean/Why are they important:

 

When to worry:

 

Legacy Specific Reference:

 

3) Oil Temp Gauge

Purpose:

 

What do these readings mean/Why are they important:

 

When to worry:

 

Legacy Specific Reference:

 

4) Water Temp Gauge

Purpose:

 

What do these readings mean/Why are they important:

 

When to worry:

 

Legacy Specific Reference:

 

5) Exhaust Gas Temperature Gauge

Purpose:

 

What do these readings mean/Why are they important:

 

When to worry:

 

Legacy Specific Reference:

 

 

6) Air/Fuel Ratio Gauge

Purpose:

 

What do these readings mean/Why are they important:

 

When to worry:

 

Legacy Specific Reference:

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