Torque and SFC at a given RPM at different throttle openings

[Timmerman1998]

Hello everyone,

For a university assignment I need to calculate the total fuel consumption of a car travelling a given track at diffent speeds for each part of the track, using Matlab. The only thing I am stuck with right now is that I only have the torque-speed and SFC(Specific Fuel Consumption-speed characteristics given at full load (throttle valve fully open, for when the car is accelerating) and I also need to know how much these change when the engine runs at half-load(throttle valve half open for when the car is driving at constant speed) and when the engine runs at very low load (throttle valve almost completely closed for when the car is decelerating). So in short, I need to know how much the torque and SFC values at a given RPM change if the engine load (throttle valve opening) decreases. Can anyone help me?

In the attachment you can find the curves of torque-speed and the SFC-speed characteristics as well as all the exact values of the Torque in Nm, Specific Fuel consumption(sfc) in g/kWh and engine speed in RPM (w).

 

[Timmerman1998]

As it's only possible to upload only 1 file per post here are the curves

 

[Timmerman1998]

and the SFC speed curve

 

[BrianPetersen]

Couple different points of view here.

Option 1 is to do what you are planning, which requires the full BSFC map including the part load regime. You don't have the part-load information, and there is no simple way to infer it.

Option 2 is to think like a racing driver and look at what you are actually doing. Unless the vehicle is considerably overpowered for the track, you should either be accelerating or braking, and spend only short bits of time mid corner at neutral throttle. As soon as you can accelerate full throttle, you should. The upshot is that you should look at how much time you are spending at part throttle in your simulation and assessing whether the lack of accuracy in those conditions is meaningful.

My own roadracing motorcycle, which has EFI, has deceleration fuel cut. At or below 2% throttle above (if I remember right) 3500 rpm, the specified injection quantity is zero.

 

[GregLocock]

Here's a bsfc map, without the equivalent you are lost in the real world, racing is a different matter

Cheers

Greg Locock


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