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Old 29-09-2013, 02:54   #1
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Diesel Exhaust Gas Temperature-Power Delivered

I have on my boat two Volvo D2-75.
Just for curiosity, I would like to know what is the relationship betwen exhaust gas temperature and power delivered by the engine.
What is a typical temperature just behind the turbo if runing full crankshaft power? Can we expect a linear relationship or does it inflects
very much before reaching full power.
Any references will be greatly appreciated.
Many thanks in advance.
François
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Old 29-09-2013, 04:45   #2
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Re: Diesel Exhaust Gas Temperature-Power Delivered

Greetings and welcome aboard the CF, Arion.

See ➥ Exhaust Gas Temperature Basics - Diesel Power Magazine

More ➥ https://www.google.ca/search?q=exhau...PKbN2QXF_oD4Ag
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Old 29-09-2013, 12:04   #3
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Re: Diesel Exhaust Gas Temperature-Power Delivered

I would not use truck motor parameters to judge marine diesel loading and EGT values. The load cycles on marine motors are very different than road units. The prop loading is a very significant factor and overloading leads to high EGT. This is the most prevalent situation with marine motors. Each motor comes from the factory with a set of specs. including max EGT values at WOT full load. This is the area you want to stay away from if you want long motor life. Most Gauges are not absolutely accurate but that is not usually a problem just as long as they are reproducible. The idea is to monitor the heat which is directly related to the load and keep it in a acceptable range. If your readings are going up at a given RPM than there is something wrong. It could be a dirty bottom a prop problem or a motor issue. Boats with variable pitch props use EGT to set pitch for a given RPM for best results.
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Old 29-09-2013, 18:09   #4
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Re: Diesel Exhaust Gas Temperature-Power Delivered

To add to the question, assuming a non turbo marine diesel, where would you put the EGT probe? Drill the manifold? Drill the exhaust elbow (before the water injection)? Would a probe in the elbow be subject to rust from the proximity of salt? I dont recall ever seeing an EGT in a small (under 100HP) diesel, but I think they are a very good idea for trouble shooting. If you install one in an already running boat, you can establish a base line for your normal running habits, and if at a later date the readings change, you can start looking for a problem before it becomes catastrophic. I have only used them in airplanes where they will give an indication of some change (probably valve leakage, or intake air leakage) much sooner than you can tell the difference by sound or feel of how the engine is running. The gauges sold for the experimental airplanes are not very expensive and dont require any power source, so you just run the wires from the probe to the meter. But again, I dont know if the aviation probes would work that near to salt? Has anyone done this on a small diesel? ____Grant.
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Old 06-10-2013, 10:36   #5
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Re: Diesel Exhaust Gas Temperature-Power Delivered

Many thanks for your valuable comments an references.
François
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Old 06-10-2013, 18:30   #6
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Re: Diesel Exhaust Gas Temperature-Power Delivered

I have installed them in several boats including my own. Normally they are put in the exhaust elbow removing the plug where you check the exhaust back pressure and replacing it with the probe.

This is either in a turbo or non- turbo set up.

I have seen turbo engines with them on the manifold side of the turbo and on the exhaust side of the turbo, showing the temp drop across the turbo.

I had a series of bad injectors in my engine and every time one started to fail, you would see the temp go up, long before any other problem showed itself.

They will also quickly show an overload issue.

I have seen larger engines with a probe on each cylinder.

They are well worth the money.
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Old 06-10-2013, 18:52   #7
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Re: Diesel Exhaust Gas Temperature-Power Delivered

the proper location of a EGT probe is on the manifold, no less then 1" from the head. this is the only way to see the true EGT.
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Old 06-10-2013, 19:27   #8
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Re: Diesel Exhaust Gas Temperature-Power Delivered

Quote:
Originally Posted by scoobert View Post
the proper location of a EGT probe is on the manifold, no less then 1" from the head. this is the only way to see the true EGT.

It depends on where the factory reads the temp. The specs on most turbo engines is after the turbo. Most non turbo engines I have seen are measured at the end of the manifold as it joins the exhaust elbow unless each cylinder has a probe, but I have only seen that on very large engines.
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