Engine performance data gurus...help!

[S2 PTH]

Right, I'm doing a piece of coursework here, and I need some ideas to help me make comments/ assumptions on my graphs. The experiment was: 1.4 Rover engine on a dyno. The load was adjusted at WOT and the rpm was set to 2500rpm. Then we changed the throttle position to 3/4 open and altered the ignition timing untill the engine ran unsatisfactorily. We then increased the ignition timing by 5degrees crank, and then in incriments of 3degrees crank until we got to 23 degrees (ie, 5degrees advance, 8, 11, 14, 17, 20, 23degrees advance) At 23 degrees advance the engine was running unsatisfactorily again, therefore the best region was somewhere in the middle (14 degrees advance).

We got values for: Load, AFR, Fuel flow (of 25ml of fuel), channel time (which was basically a time elapse reading, in nano seconds) and finally we had a read out of the pressure for each of these time incriments (which was given to us in micro volts, because of the way the sensor readings were recorded).

We then did all this for 1/2 and 1/4 throttle measurements respectively, doing all the same calculations.


Calculations for Brake power, Brake mean effective pressure, brake specific fuel consumption, and thermal efficiency were calulated also, and these graphs are all below.

Right, here are my graphs, what can I say/extrapolate from them?!?

In Cyl Pressure Vs Swept Volume




Bmep Vs IG




BP Vs IG




BSFC VS IG



Thermal Eff Vs IG

[Dpicariello]

I'm no Guru but I did Mech Eng and did something similar.
There's a lot you can say but it depends on what the aim of the exercise was.

BMEP is very important and is the basis for horsepower and torque.
You can identify the optimum ignition timing for this from your graph. You can also see how the max BMEP provides the max specific output.

The swept volume doesn't really tell you much apart from the obvious.

Fuel consumption will go down as you approach stoichiometric A/F ratio.

So basically you're looking at about 16deg that's optimum. Could you hook up the lambda probe? That would be quite useful.

Tell me if I'm being way too obvious here..

If you need more help then PM me and I'll try to remember some more.

[S2 PTH]

No mate, that was helpfull and clear, even though obvious now that I look back. But cheers!