cool GIDS You inspired me you write a essay for my personal record in regards to this issue and many possable solutions takin as advice .
You will hear the best solution thats been kept secret here but only this once! By this I mean I won't repeat the theory only publish the result at a later date. I will prove to any doubters what is truly needed to beat the long turn blues.
T.A 's ESSAY!
I actually have heard reliable good honest civ4 players say they have gone on huge with more civs then GIBS and have about the same turn time. I believe em .
Thing is There was only 3 of em. THink how many complaints we have heard compared to great stories like yours. How many havn't we heard yet? atleast another 26 to 43 indiividual suffering souls agreed? lol
But 1st hey GIBS, are you using a standard huge map cuz those fit a lot less citys then a standard civ3 map, not so 'huge' a feat is my point!.
You can make your huge map bigger to hold more real sized nations with only a few hundred less then civ3's max of 512. See how those turns run late game with 16-18 civs and share with us if you could. Your word is good here no vid is required. SOme are Your real smooth at rig setup

THe guys are rare but will raise the # of no problem civ4 civving.
Civ3 runs 24 civs on 40% extended default huge maps with about 2 minutes a turn. See when you get top evolution Mono play, Time only depends on how many thousands of troops are dyin on the feild on that given day - nothin else.
It takes each of the 24 AI's a few seconds to kill-be killed/trade/build/ change Gov , whatever. Basicly do what a human takes ten minutes to do late game huge map. The AI does this in about .01 of your time, still thats 24 civs down the list plua you calculations. This can add up to a minute or even two!!

If 400 turns of built up units are being sacrificed by any or all nations, like a World war bloodbath, somewhere off the screen, then more minutes should be acceptable as towns take a second to flip same with pillages

If there are no wars, it wips through a 24 civ deck instantanously. Done. Your up
One day civ4 will do this. Most likly durin CIv5's 1st Xpak
When lookin at turn times I have no doubt civ3 sucked before civ4 came out (still atleast response was good) It wasn't till rigs with large L2 caches arrived (processsor mem) that civ3 steamed along.
THe cedermill was the pinnicle of development in this area, combining record L2 cache with record ghz, enhanced 1st time with overclock ease for a mono (up to 8 ghz! .)
Both games are mono ONLY utilized and these L2 supplys and ghz are what makes turns fly .
THe ghz myth does not apply to turn based games on mono core. Why? Well when 2 gigs of ram are met, the G card with 512ram aswell, all thats left is how fast the AI can think through the weighted down graphics burden! .
With your 2gigs of Ram holding back weighty 3D graphics, 2 things make the AI run its tasks the fastest, that is L2 Cache and ghz clock speed.
Industry still uses monocore application everywhere where large stacks of simple calculation are spun in blinding speed and power output is not a bother
Any dualcore that first arrived setback develpment on the
civ turncruching front. With a mono You could always manually drop the usless "processes" for civving to take out any adv a dual has
STill Intell had no choice. they had reached a pinnacle for processors and those who got there hands on one of these lucked out on civ type applications. period.
Intel knew it cost to much to run its pumped up processors .
They did one attempt to save face, THe ceder was the only pent4 that used the smaller 65 nm core, making heat less a prob when coupled with joint promoted MSI's
CORECELL reveloutionary software to prevent overheating on fast ghz output.
THis tech that made the greatest P4 and civ machine in general, could have kept up the pace for faster models with even higher L2 levels but was it forgotten to go down to smaller dualcores to continue their build up to new model every 6 monthes patten again. A smart biznaz move that sent civ4 players back down the performance ladder lured by fancy add gimmicks and accepeted old knowledge 'newer is better' Well it wasn't for the unique turn based interturn process civ used. I will prove this , but anyway there you have it.
Those know-it-alls said Coreduo was better or egg fryin is all ya can do with late P4's. They were obliviosly not aware of the P4 mono-COREDUO intigration used to build the civving masterpeice Pent 4Cedermill, which ran at speeds of 8ghz without breaking a sweat and which meant more with it new precendent levels of high L2 cache avoiding the long inefficient pipe structure scorned by amd fans with all pent 4's
THink of the rare cedermill like the fastest racecar that now dosn't ever need to stop for gas(virtual mem call up,) when before its team gas attendent was blind and quadriplegic! . THis was the ultimate civving variables Finnaly!
Nobody can find this rig anymore. So its a pity they feel 4 engines will do the same job as one going the speed of a diablo with Record speed processor (4-8ghz).
THis rig is the fastest civ machine ever assembled. . I was obsessed with breakin speed records and it cost me some mean cash. The power output made those Drug choppers flyby with their grow op detecters

Civ, any civ, at top speed is a luxery and a dream , made me the passioante guy on civ3 it seams . SAdly this rig used is a rare commodity. but its the best solution
Essay out xcuse the lil grams errors