Iv found that in a-spec one make races as long as you run the car identically to the AI they can give you a run for your money.........identically means, zero tuning, zero upgardes and same tyre.
Did this in a 10 lap race round tskuba in a 908, spent most of the race in second behind a very quick AI car, could probably have kamikazied him on the inside but i always try to race fairly and doing that i could not get by him. eventually on lap 8 he got a bit sideways and past i went. I then went for glory and tried to set a fastest lap. won by 7th tenths in the end
On checking the live timing i noted his best laptime to be only 2 tenths slower that my best and the rest of the field werent far behind. Iv been doing quite alot of experimenting with the AI in a-spec, arcade and b -spec and came up with some interesting results. I intend putting my findings up in a thread soon, but generally in conclusion iv found that the AI certainly have the programming to go very quick, certainly quick enough to give a human opponent a fright in a similar car but its is only activated on very rare occasions.
More will be revealed soon
This sounds very interesting and I am eager to read your report as soon as you public your findings.
The main thing here is how tuned are the AI cars and how hard are the AI driving, it would be so ideal to be able to set up the AI strength, but not in order to get more powerful cars showing up but and most important to set the AI ability/aggressiveness within the same car.
On the other hand I still see the tire choice as the deciding factor to get close races. Try SuperGT with a Lexus SC with Sport medium against a Nissan GT-R with Racing Hards for example and the race will be more or less evenly matched as you have to be as careful as the AI to drive around the corners without having to lose speed on the straights.
Anyway I have read some interesting and different ideas on how to approach this, some will choose worse tires, others less powerful cars or ballast, etc...
Also I forgot about the GT5 matchmaking spreadsheet which is a superb job and a very helpful tool, but as soon as I have the chance to play this game I rather experiment by myself.
One thing is clear, the AI have and must be harder to beat with same tires choice and similar cars, but as long as we do not have any AI strength set up (a % slide bar) neither a PP/tires set up then for those who like to enjoy match races we have to find our own way to get it right and when this is done correctly it becomes a piece of art.
As others said it is much better to finish in second place by less than a second than win with a big advantage, which in the end it is just no more than time trials.