Brandon@Forged

Yeah we already figured out my math is bad.

zxsaint

Seems on par with most E46 M3's (330 fly) that dyno at around 270-280 whp.

TwiZted

iTrader: (1)

figure 15% loss on 287 = (287fwhp x .85 = 244rwhp) STOCK

take 280 whp/85 x 100 = 329hp

about 330

Taking a 230rwhp avg on stock Z's, about 20% loss, the actual fwhp of 280 rwhp that would be about 350fwhp

These are all estimates and all cars are different, there is only one way to get actual #'s, do a dyno at the wheels, and pull the motor and dyno it seperatly

arizzee

iTrader: (28)

Wow, what a lesson in math!

I have one question about the % of drivetrain loss. Can someone explain why as you increase power, your drivetrain loss is proportional? I mean isn't drivetrain loss due to energy loss through inertia and friction (heat loss). I guess I don't understand how making more power increases the drivetrains inertia or friction.

So based on the above assumptions (drivetrain loss is close to constant), my theory is that the correct formula for bhp is: BHP = WHP + (287 x %DTL) where %DTL ( percent drivetrain loss) is a guesstimate based on the fact that 287 bhp is Nissan's rating and dynos show 230-240 whp.

Brandon@Forged

The only way to reduce drivetrain loss is to reduce the weight within the powertrain/drivetrain that the motor has to turn, less weight = less power to turn, i.e.: lighter crank pulley, flywheel, etc.

arizzee

iTrader: (28)

But what I mean is that if you haven't added weight to the drivetrain, how does making more power also increase the drivetrain loss?

Brandon@Forged

It shouldn't.

arizzee

iTrader: (28)

So for example, I dyno my stock Z and get 235 whp. This equals a 52 hp or 18% drivetrain loss.


So I then add an APS TT and dyno 400 whp. Using the % drivetrain loss method, my bhp is 400whp + (400 x .18) = 472bhp.

So using that calculation method somehow means adding a TT adds 20 hp to the drivetrain loss. My common sense says that is not what has happened, but indeed my drive train loss is about the same (hard to factor heat loss).

I think it's more accurate to assume the same drivetrain loss (a supercharger is another story), so I'd figure bhp as 400whp + 52 hp = 452 bhp

But I know very little about internal combustion engines so I'm probably missing it.

omarv6

guys correct me if am wrong !!i read this in a car mag once !
if you devide the cars Hp by 1.15 you will get the wheels HP ...
and if you maltiply any car clame whp by 1.15 you will get the fly wheel hp !

Brandon@Forged

Car company's don't claim WHP, they claim flywheel hp since it is higher.

omarv6

ya i i know but i wrote it wrong !!
fly wheel / 1.15 = whp
and
whp X 1.15 = Flywheel hp .

could this be correct !

Brandon@Forged

It's close, not close enough, it's a general equation.

TwiZted

iTrader: (1)

If your car is losing 18% then 82% of the power your making is at the wheels.

Take whatever rwhp you have divided by 82 x 100 and you'll get your approximate fwhp.

This is just an example if it was 15% loss you would divide by 85

of course this is assuming that the 287fwhp Nissan gives is infact correct

Thats why horsepower is just a figure it doesnt determine speed, torque is a much better guage of how fast/powerful a car is as it is an actual measure