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VE stopped increasing with load adter 0,5bar of boost

Road Tuning

Discussion and questions related to the course Road Tuning


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Hello,

I'm trying to tune VE table for 3S-GTE gen3. I've found that VE stopped increasing with load(MAP) after some MAP value(0.5 bar of boost). In wide RPM range. (Please check attached pic, area above 200kpa isn't tuned yet). But from course I understand that VE should increase with load.

What could be the reasons? Low-flow exhaust? Turbocharger? Cams? Or something else?

Thanks, Alexander.

Attached Files

It's important to understand that VE and air density are not the same thing. What we're defining with VE is the ability of the engine to fill its cylinder with air which is all about restrictions to airflow into and out of the engine. What the turbocharger does is also increase the density of that air so for a given volume of air we can increase the air density which means we have more oxygen available and can therefore make more power. So in short we don't necessarily expect to see the VE increase in line with boost. in most cases we will initially see the VE increase but then the VE will plateau and if we continue increasing the boost we can likely see the VE start to drop away again. This is typical with a small turbo where the exhaust back pressure starts to increase dramatically restricting airflow and hence reducing the VE.

Thank you, Andre. I'm very appreciate such understandable answers.