# Torque and volumetric efficiency relationship

1. Jul 14, 2014

### rambharath94

Hello Guys,

From the torque curves of most of the ic engines it can be seen that torque is maximum at a particular rpm range then it starts dropping. It is said that the torque is maximum when the volumetric efficiency is maximum , i just can't understand the relationship between the both these quantities.

2. Jul 15, 2014

### jack action

Better volumetric effficiency means more air; more air means more fuel can be burned; more fuel burned means bigger explosion; bigger explosion means more torque.

Volumetric efficiency depends on intake & exhaust design and valve overture. Unless there is a variable design (variable valve timing for example), the system is usually tuned for a certain rpm range, hence the peak torque at a certain rpm.

As rpm increases, the intake and/or exhaust system can choked, not being able to fill completely the cylinder, hence a drop in volumetric efficiency.

3. Apr 18, 2016

### zanick

That is not exactly true. volumetric efficency is the ratio of engergy consumed vs energy generated. i belive this to be at max torque, but it doesnt mean its at the point where the most amount of air and fuel is burned. that will happen at max HP. Hp-seconds is the unit measure of work. the most energy will be used at max hp because that is the engines greatest capacity for work, so most amount of fuel will be used at ths point in the curve. Max torque of the engine is only about the angles and sizes of pistons and cranks... the torque you are really concerned about, is that at the rear wheels, through the gear box. The greatest acceleration forces will happen at max HP, NOT a max torque for any given vehicle speed.

4. Apr 18, 2016

### xxChrisxx

Zanick write equation down for volumetric efficiency.

Check your work with the oracles of google if you like.

By the way, you've totally missed the point of the OP's question, and have subsequently made a total mess of trying to contradict jacks answer.

Last edited: Apr 18, 2016
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