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Drop in VE between 3000 and 4000 RPM

Practical Dyno Tuning

Discussion and questions related to the course Practical Dyno Tuning


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Mates,

is it normal to see a slight drop in VE between 3000 and 4000 RMP ? as the Motec M1 worked example is showing ?

Regards,

What is the engine, vehicle, and modifications? On a naturally aspirated engine for example it is possible that the manifold tuning could lead to a dip in VE.

Hi @arghx7 and thanks for your input.

I am asking about the particular car found in the module of the Motec M1 worked example. It was N/A and the car was a GT86.

Regards,

As I have said before, I have a real issue with the use of "VE" in software maps.

However, as Ray said, it is possible that the intake, exhaust and cam' timing characteristics compromise the engine's cylinder filling efficiency at that part of the rpm range. While most engines will have a smooth climb and fall off in torque over their operating range, you willhave noticed that some will have one, or more, dips and crests in the curve - these represent drops in the "VE" as the "VE" and torque are very closely related.

Those subaru motors are known to have a torque dip in that range. Most conventional production motors, especially with vvt won't exibit as much as that even if there are some poor harmonics as they sweep through their torque band.

The toyota 86 has a weird dip in torque around this rpm. It's assumed it's in relation to a design element of the intake. Essentially your VE numbers should follow the shape of the torque curve. If there's a large discrepancy then there is a problem potentially.

Many thanks guys !

There's another way of thinking about a torque dip on an N/A engine like the infamous BRZ dip (it's not exclusive to that engine by any means). Don't think of it as a dip, think of it as having a "bump" below the "dip" range. Often the manifold tuning (variable intake runner for example) or variable valve timing effects increase the torque in a specific rpm range, and then as rpm increases that scavenging effect ends, and you get the perceived dip.

Thanks @Argh7, sorry i was absent long time !