I believe I have solved the problem with the "griddata"-command.
Below follows an example of the code.
A = load('rpmNmmpTtemp.asc');
B = A(:,1);
C = A(:,2);
D = A(:,5);
rpm = 500:10:2400;
torque = 0:10:2500;
[xi,yi] = meshgrid(rpm,torque);
[zi] = griddata(B,C,D,xi,yi);
axis([0 max(rpm) 0 max(torque)])
xlabel('Engine RPM'), ylabel('Engine torque')
I know this is not a dedicated matlab forum but I figured I'd try anyway.