I don't know if this has been pointed out before, but I noticed that the production value of a great engineer when used to finish a building is 500 hammers + 20 hammers per population point.

Once you get through the early part of the tech tree where a great engineer finishes just about everything, then sometimes it only covers part of a building. That is determined by population.

So a size 5 city would get 600 hammers.
A size 10 city would get 700 hammers.
A size 15 city would get 800 hammers.
A size 20 city would get 900 hammers.

That's interesting. Do you also get the multipliers for leader traits, buildings, resources, etc.?

Doesn't look like it. I didn't test different game speeds (quick, epic, normal), so the above applies to normal, but resources or traits don't seem to have an effect.

I imagine things will be different with quick or epic speeds.

I presume these numbers are for a normal-speed game. Epic numbers would be higher.

I noticed you don't get the resource discount. So I try to build wonders that I have the resource for, and rush wonders that I don't.

excellent observation. i did notice that production given by engineer was going up, but i didnt know if it was era based or production cost based. thanks for clearing that one up.
and i can use this knowledge. :goodjob:

Thanks OP for this, much needed information.

Those value can be found in CIV4UnitInfos.xml for engineer:
<iBaseHurry>500</iBaseHurry>
<iHurryMultiplier>20</iHurryMultiplier>

While we're talking about great engineer, is there a limit on how much of it can be produced (either per city or per civ) ?

The number of Engineer GPP per city is limited because you don't get extra engineers from Caste System. But if you concentrate on getting only Great Engineers you can have 10+ in a game.

No real limit. Theoretically, you could have only a 10% chance of producing a Great Engineer and still get lucky and get him everytime. You can get as many Great Engineers as you have GPP for.