Correlation between predicted and real-world fe?

[TheEnemy]

What are you using as a base load? Even the value I had posted on my Jeep is probably way too low and should be closer to 5,000.

A rough guestimate for just the internal friction overhead would be 1000 for a 4 cyl, 1500 for a 6, and 2000 for an 8.

Some more guestimates
When the fan is on that adds 100-150w
Ignition/engine management 20-150w
Lights 200w

[MetroMPG]

Originally Posted by roflwaffle

Sure it does. Engine efficiency = BSFC.

I should have said it doesn't take into account varying efficiency. It spits out the entire speed vs. MPG table at one efficiency point.

[RobertSmalls]

@TheEnemy: engine friction is already taken into account in BSFC. You only need to add electrical loads.

Keep in mind, most alternators are about 50% efficient, so 200W of electrical loads adds 400W to the parasitic loads field.

[roflwaffle]

Originally Posted by MetroMPG

I should have said it doesn't take into account varying efficiency. It spits out the entire speed vs. MPG table at one efficiency point.

Fer sure. But like Robert pointed out, we can't really do much more than that unless we had something that was using the actual speed/grade and comparing that to a calculated BSFC map.

[TheEnemy]

Originally Posted by RobertSmalls

@TheEnemy: engine friction is already taken into account in BSFC. You only need to add electrical loads.

Keep in mind, most alternators are about 50% efficient, so 200W of electrical loads adds 400W to the parasitic loads field.

I'm not entirely sure about that, but at least for now I'll take your word for it.

The question still remains as to whether or not he is accounting for all of his loads or not.

As good as the tool is, it isn't taking into account all of the factors that would affect FE, but having it account for all factors would be impractical for the vast majority of people.