low power !

[42tt]

Hi Grizz

Pardon my ignorance but the 453bhp figure you quoted when you replaced the MAF's was that at the wheels or an estimated Engine HP figure?

Also can you post the dyno plot aswell and what gear was the car dynoed in?

Thanks
42tt

[grizz]

hi 42tt , the 453 was at the estimated crank hp . I did see a dyno plot for a b5 rs4 that had 360 whp but had 440 crank . mine was 362whp.
I'm getting it back on the r/road tomorrow.

[42tt]

Grizz - from what i can tell you my RS6 made 340whp in totally standard form on a average day. What gear was your car in?

[grizz]

3rd gear .

[skiwi]

as power = work done, i've often wondered why a simple 0-100 exercise isn't sufficient for understanding actual hp? moving an object of known weight to a certain speed in a certain time will give an acceleration figure and hence a hp....

or is my school physics not up to it....

[Rupert]

E = energy
P = Power
P = energy / time
E = 1/2 m v ^2
v = velocity
m = mass
So the kinetic energy of a car car of mass 1860KG moving at 100kph (27.78 metres per second) is:
0.5 * 1860 * 27.78 * 27.78 = 717.6k joules.
If this takes 4.7 seconds the power input is 717.6k/4.7 = 152kW = 204BHP.

Which makes perfect sense.

[Fen]

That's how devices like my G-Tech work BUT you need a perfectly flat road, you need to attain perfect traction, you need to accurately know the weight of the car, it needs not to be windy (or you need to average passes in the opposite direction). All in all it's easier to use a dyno IMO.

Also it's a total work done - you don't get any data on the changes through the rev range.

[skiwi]

E = energy
P = Power
P = energy / time
E = 1/2 m v ^2
v = velocity
m = mass
So the kinetic energy of a car car of mass 1860KG moving at 100kph (27.78 metres per second) is:
0.5 * 1860 * 27.78 * 27.78 = 717.6k joules.
If this takes 4.7 seconds the power input is 717.6k/4.7 = 152kW = 204BHP.

Which makes perfect sense.

correct for steady state, not acceleration....

we need the work done to get the 1850kg missle to 100kph in 4.7 seconds...

[Rupert]

I'll let you do the integration then!

[42tt]

Grizz,

My car was also dynoed in 3rd gear on a Dyno Dynamics Dyno. As i am unsure of your modifications i cannot comment on your power output, having said that the only true test is if the dyno is in "Shoot Out Mode" which corrects HP for temp etc and that your car was dynoed on the same dyno for a base line HP figure before modifications.

My dyno specs are:

Ambient Temp 26 Celcius
Intake Temp 28 Celcius
Gear 3rd
343.2 WHP

A better measure of HP is at the 1/4mile where you can see from your trap speed my car has run a best ET of 13.07@106MPH on a not so cold night.

Regards,
42tt

[grizz]

Well it's a bit better , it made 390 whp , i'll look at the temps later . it was in "shoot out mode"

[skiwi]

you could just tell them to change a few of the parameters to ensure the final numbers were over 400?

[skiwi]

I'll let you do the integration then!

mate, i left that stuff behind so long ago, i hardly remember what it means.

interestig to me though that physics whould indicate quire precisely what bhp and torque are required...

[Fen]

you could just tell them to change a few of the parameters to ensure the final numbers were over 400?

Actually part of the idea of Dyno Dynamics shoot-out mode is that you can't play with the settings to inflate the readings, the other being that it adjusts for ambient conditions to try to make readings on different days comparable.

[skiwi]

on the surface you would think that there would be nothing more simple than a rolling road to determine whp, but the more i read on them the more flawed they seem...