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Why does my turbo charger glow red? Is my turbo getting too hot? Should my generators turbo glow red?

Should my generators turbo glow red?

A frequently asked question for diesel generators is about the turbo charger - should it glow red when the generator is under high load. The short answer is yes, probably. We go into it in a bit more detail below.


A turbo glowing red hot under high load.

Why does my turbo charger glow red?

Turbo chargers are made of iron. When iron gets hot, it glows red. This effect is called red heat - you can see the colours or iron and the effect of red here. Turbo chargers get hot because hot exhaust gases flow through the manifold then the turbo. So when the turbo is red hot, the manifold also glows with red heat.

The temperature of the exhaust gas in diesel engines varies by manufacturer. For Perkins engines, up to almost 600 degrees is very common, which will cause a black red to dark red glow. The temperature may vary a little across the manifold, causing a different colour.

How does load change the turbo colour?

As the engine load increases, the exhaust gas gets hotter and the turbo will also get hotter. You should pay careful attention to the generators rating - is it Prime Rated (PRP), Standby Rated (ESP), Continuous Rated (COP) or Limited Time Power Rated (LTP). You should always ensure you are running your generator within the limited of its rating. For example, if you have a Prime Rated (PRP) generator, you should be running it at an average of 70% load.

How do I check my turbo temperature is within the expected range?

You should refer to the engine specification sheet for your engine, which will state the maximum turbo temperature at the test conditions. This is often at NTP conditions - so sea level, 27 degrees and 50% humidity. Therefore if your actual ambient is different you might see hotter temperatures than the specification sheet displays.

To measure the temperature of the turbo you need a calibrated infrared thermometer capable of measuring the manifold temperatures.

Why would my turbo charger would become hotter than normal?

Many things can have an effect on an engine and its temperatures. Here are a few common reasons the turbo might get hotter than expected for a given load. If you think you have a problem, check these things.

Lack of cooling Air

Most engines need air to remove the heat - the engine manufacturer will have a minimum air flow requirement for an engine. If you have the engine in a room or canopy, you should ensure there is sufficient air flow to cool the engine and also that this air is at ambient temperature - for example, none of the hot air leaving the engine is being allowed to recirculate - its being diverted out the room away from the air intake, by means of a sealed duct.

Use of the correct engine oil

The engine oil should be the correct grade and be in good condition; engine oil is the lifeblood of the engine and should be maintained as a priority. Poor quality oil can cause additional friction in the engine and lead to higher engine temperatures and hence higher turbo temperature.

Use of the correct coolant

Again - key for keeping the engine performing well. The coolant helps keep the engine cool. If the coolant level is low, or of the wrong grade for your engine, you might experience poor cooling. Note: If you have previously used the wrong grade of coolant, you may have damaged the radiator or block internally and changing to the correct coolant may not be sufficient to correct the problem.

Exhaust Back Pressure too High

Every engine will have a maximum allowable back pressure. Check the back pressure on the exhaust system doesn't exceed this limit. The higher the back pressure, the higher the manifold / turbo temperature will be.

The load on the engine is too high

Check the engine loading. For generators, this load is usually measured with a current transformer being fed into a control module. CT's can be out by 1-5% (or more on a really cheap CT) and therefore the actual load may not match the displayed loading.

Equally if you are running the generator at a prime rating, ensure the load is an average of 70% to meet the requirements of prime power. In high altitudes and hot conditions the engine will probably require a de-rate - so the maximum rating at 2000m and 40 degrees may be significantly lower than the actual rating.

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