Here's a formula that's been around for awhile that'll give you a good idea of how much HP your car really has. Based on the trap speeds I've seen posted and the G35's weight, Infiniti may be exaggerating the G35's HP a tad.

http://www.torinocobra.com/horsepower.htm

 

garbage.....what about gearing....and traction??....the 3.9 fd ....tires that grip....what about a lightened flywheel....all of these mods will improve trap speed....does that mean your hp has increased??.....mustang mag compared 5 mustangs...the mustang with the least hp(stock) was the second fastest???

 

oh and if you must use the calc......you must add your weight to the vehicle...when you do that it seems like infiniti underestimted hp in the g35

 

There are lots of influencing factors, but this is just an estimate and if it estimates RWHP instead of brake HP, it could be a real close estimate. The factories of course list brake HP in their publications.

 

Consider how a chassis dyno measures rear wheel power, by measuring the time it takes for the drum speed to increase [how much] in 1/1000 or 1/100 of a second increments.

Magazines are pretty good about showing accelerations in 10 mph increments and the test weight.......obviously 10 times better than using just a single trap speed but 1,000-10,000 times less accurate than a chassis dyno.

Reverse Correlating flywheel to rear wheel is always full of errors.

Not unusal to have a 3% variations {+- 10 HP} best to worst on assembled engines at different stages of their life [mileage] depending on ring breakin and oil type......not to mention local gasoline formulation. The variation between conventional and ethanolized is 3% alone [minimum] due to lower BTU of ethanol.
Altitude causes a 1% variation per 333 feet above sealevel and temperature a 1% variation for every 11F. Humidity is less troublesome except fog and rain.

All the above are additive.........why engines alone are tested in controlled condition labs where published power numbers are derived from averaging 5-10 hand selected [expert built] units during development phase............a production numbers ramp up assembly variations add up........good one, average one, or the worst case one cycle thru on a daily basis.

If you study FSM you with see all the possible bearing/ring gap sizes, pistons, bucket lifter shims, etc, etc.........how the technican assembles lose or tight from his choices.

Makes the power variations at any point on the mileage curve.

 

That formula has no clue about area under the curve. Plug in the numbers for a stock 3rd gen RX7 and that calc says that car should run 12.95. LOL, never happen, stock 3rd gens can dip to the mid 13's, but into 12's? hasn't happened. Problem is that basic formula cannot take into account all the variableslike area under the curve, launch, etc.