Originally Posted by RS38

ah, it's getting technical, that's fine!

you need to differ between the physical and SAE/ISO/DIN correction factor of temperature and the actual result that is due to ECUs interaction.

First of all the physical dense of air correlates nearly with Square root of the actual temp related to the absolute temp in terms of degrees kelvin (-> 90 degrees is not "twice as hot" as 45).

if you omit the air pressure the equation for the SAE/ISO correction factor/coefficient is equal to (actual temp in kelvin / 298)^0,6
If you set it into relation with the temp before in winter or summer you have the difference in %.
the 97,8% already mentioned are probably calculated in the same way.
this numers would be very true for an old school non aspirated engine with no electronic.

but these numbers lack alot of circumstances we also face!

We have turbines, aircooled I/C, knock sensors, different fuel and a ECU that trys to get our engine safe.

simply by generating boost to above 1 bar we increase the temperatur of the air a lot (>120 degree celsius) and try to get it cold again with the I/C, which has usually an effinciency of ~80%, which roughly means the intake temp at WOT is always many degrees above environmental air.
If you have an OBD2 monitor you can see that very nicely.

in summer conditions you reach a certain trigger temp of the (stock) ECU very fast. it then will go back with ignition and even boost later on. Also knocking probability increases and the ECU reacts with lowering power.

A stock ECU normaly trys to compensate air temp and pressure diffs, but only to a certain amount. I know many Turbo drivers who claim that their max boost went down and they were afraid it could be a failure, but it is the ECU that decides it wont need any more boost if the air is already dense enough.

Any of you having a good data logger can check it, if 60-130 times are really better than in summer. there is no big difference. If you drive in the desert of nevada you will always suffer from ECU safety mappings but if I compare with zero and 25 degrees celsius, I cannot see anything significant.