One of the biggest advancements in turbo design since we first started applying them to diesel engines over 70 years ago has been the invention of Variable Geometry Turbos. These turbos utilize a set of movable vanes on the inside of the exhaust housing that allows the actuator to vary the area in which exhaust gasses can pass through them. This allows the exhaust side of the turbo to increase or restrict the flow of exhaust hitting the turbine wheel. In some designs it also changes the flow direction of gasses hitting the exhaust turbine as you can see illustrated below.
When restricted, the velocity of the exhaust gasses increases which helps spin the turbine faster than a fixed geometry turbo would. This gives the turbo the ability to spool the turbine and compressor wheel up much better than it normally would even with a low volume of exhaust pressure traveling through the system. This helps to spool the turbo at lower RPMs to create boost where it would normally be lacking. This is why variable geometry turbos (VGTs) are such an advancement. They have the ability to significantly reduce turbo lag and provide much better response and turbo efficiency across a range of RPMs.
LML SPADE & Smart EGT Control:
Exhaust Gas Temperatures (EGTs) give you an insight as to how much stress you are putting your engine under. It is the most accurate way to monitor if your current activity is safe for the engine.
In a factory tuned truck high EGTs would most commonly be a sign of a physical problem like a boost leak. However, a tuner added to an aggressive driver could result in EGTs beyond the desired limit.
Most examples of this also include a mismatch of your tune level and truck operation. Such as the guy towing in his race tune.
The LML SPADE by DuramaxTuner.com now includes a Smart EGT Control feature.
How Tractors Measure Exhaust Gas Temperatures
Have you ever noticed that some OEM's do not install an EGT (exhaust gas temperature) probe on the manifold? Any performance diesel gear head will tell you it's the best place to measure EGT's giving you the most accurate insight to any immediate stress on the motor.
Spiking EGT's in the manifold could be a symptom of many different problems including low boost, failing injectors, airflow restriction, EGR failure, etc. All of these failures signify a lit fuse that ultimately ends in engine failure if left unchecked. Clearly it's important to monitor EGT's, right!?
The problem with installing a probe from the manufacturer stand point is the life expectancy of the probe. Seeing extreme temperatures and still measuring accurately for the life of the service life requires high quality probes (read: expensive).
Never fear, manufacturers have come a long way in measuring temperatures (and cutting costs). In fact many feel no real need for a probe favoring a dynamic EGT model instead.
