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Old 05-04-2009, 10:43 AM   #9 (permalink)
EcoModding Lurker
Join Date: Mar 2009
Location: Tamarindo, Costa Rica
Posts: 19

80 - '91 Toyota Land Cruiser
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EGT (exhaust gas temp) gauge will tell you the most about your motor. When Exhaust temps are high, it is usually because you have inefficient burn and some of the fuel is finishing combustion after the power stroke.

If you plan to tune the motor, one of the first 'tricks' is to turn the fuel up or down (up=more power, down=more economy... to a point!). If you do that, you'll need an EGT and pyrometer (the pyrometer is what reads the temp, the gauge displays the results, EGT is what is being read).

If you are really worried about the turbo being damaged by the pyro, then install it after the turbo. It won't be as accurate, and will certainly read much lower than before turbo, but it will still give you an idea as to the relative changes in fuel load.

It will also allow you to fiddle with your boost settings, which can yield a big increase in power or economy. Basically: as your motor gets more load, boost should go up to a given point. I don't know your motor so I won't suggest maximum boost settings as too much boost will pooch the motor for sure. For a large 6cyl Toyota diesel (4.2liter) "normal" boost is up to about 13psi. Some folks run 16 w/o issue. For a large cummins motor, I've heard of people running into the 30's without issue.

As boost goes up, EGT's are likely to spike (compressing air heats it). You want boost, you don't want high exhaust temps as you can easily reach temperatures in which you start to run the risk of damaging internal parts.

Short answer: I'd add EGT and Boost to any diesel. Period. Beyond that.... Oil pressure doesn't tell you much besides "time to rebuild". Several gauge companies make combined gauges for stuff that doesn't need high resolution- like oil px or voltmeter.
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