HORSEPOWER FROM OBD2 DATA

re all

I come back cause i have a little matter .
Speak with real value:

car definition :
Weight : 1300 kg
3rd gear ration : 4.48 : 1
Differential : 1 ( i guess )
tire dimension : 175/65 R14

and these 2 obd2 value : ( time;rpm)

0,682926833629608;2029
0,852926835417747;2076

so .. ( in a metric system )

/!\ 1 pouce = 25.4 millimetre
diameter wheel = (((width *0.Aspect_ratio)*2) +(jante_diameter
*25.4)
diameter = (175*0.65*2)+(14*25.4) = 583.1 mm = 0.5831 m
so circonference = PI * d = 1.831 m

after we compute the velocity !
at 1000 rpm, speed is :
1000(rpm) * ( 1 / Rv ) = Z tr/min
Z * 60 = Z tr/h
Z*circonference_of_wheel = V en m/h
V/1000 = V en Km/h
simplification :
((1000/Rv)*60 * Ct )/1000 = V soit (1/Rv) * 60 * Ct = V in hm/h @ 1000
rpm
for X rpm :
(X * (1/Rv) * 60 *Ct )/1000 = V en km/H @ X rpm
with Z,X=rpm, Rv = ( gear ratio * diff )
this formula is good, i check her with my technical book of my car , i
get the right speed at 1000 rpm !

so .. for our 2 obd2 value !! ( get in 3rd gear )

to translate km/h to m/S i use the formula : (Speed / 3600 ) * 1000

0,682926833629608;2029 --> (2029 * (1/4.48) * 60 *1.831) / 1000 =
49,75 km/h - > 13.819 m/s
0,852926835417747;2076 --> 50,90 km/h -> 14.138 m/s

now i use the acceleration formula : a = (v2-v1) / (t2 - t1) = 0.31 /
0.17 = 1.88 m/s²

we know that force = mass * acceleration : 1300 * 1.88 = 2444 newton

and work(nm) = force * displacement = 2444 * 0.31 = 757.64
newton.meter or 757.64/1.356 = 558.7 lb-ft

i know that i havent applie the wind drag factor yet, but this value
looks me too high .
Is my reasonement wrong ? or the wind factor very important to get
correct value

I know that my car cant have more than 185 nm of torque !

Thanks, and sorry for my poor english

florian wrote:
>
> re all
>
> I come back cause i have a little matter .
> Speak with real value:
>
> car definition :
> Weight : 1300 kg
> 3rd gear ration : 4.48 : 1
> Differential : 1 ( i guess )
> tire dimension : 175/65 R14
>
> and these 2 obd2 value : ( time;rpm)
>
> 0,682926833629608;2029
> 0,852926835417747;2076
>
> so .. ( in a metric system )
>
> /!\ 1 pouce = 25.4 millimetre
> diameter wheel = (((width *0.Aspect_ratio)*2) +(jante_diameter
> *25.4)
> diameter = (175*0.65*2)+(14*25.4) = 583.1 mm = 0.5831 m
> so circonference = PI * d = 1.831 m
>
> after we compute the velocity !
> at 1000 rpm, speed is :
> 1000(rpm) * ( 1 / Rv ) = Z tr/min
> Z * 60 = Z tr/h
> Z*circonference_of_wheel = V en m/h
> V/1000 = V en Km/h
> simplification :
> ((1000/Rv)*60 * Ct )/1000 = V soit (1/Rv) * 60 * Ct = V in hm/h @ 1000
> rpm
> for X rpm :
> (X * (1/Rv) * 60 *Ct )/1000 = V en km/H @ X rpm
> with Z,X=rpm, Rv = ( gear ratio * diff )
> this formula is good, i check her with my technical book of my car , i
> get the right speed at 1000 rpm !
>
> so .. for our 2 obd2 value !! ( get in 3rd gear )
>
> to translate km/h to m/S i use the formula : (Speed / 3600 ) * 1000
>
> 0,682926833629608;2029 --> (2029 * (1/4.48) * 60 *1.831) / 1000 =
> 49,75 km/h - > 13.819 m/s
> 0,852926835417747;2076 --> 50,90 km/h -> 14.138 m/s
>
> now i use the acceleration formula : a = (v2-v1) / (t2 - t1) = 0.31 /
> 0.17 = 1.88 m/s²
>
> we know that force = mass * acceleration : 1300 * 1.88 = 2444 newton
>
> and work(nm) = force * displacement = 2444 * 0.31 = 757.64
> newton.meter or 757.64/1.356 = 558.7 lb-ft
>
> i know that i havent applie the wind drag factor yet, but this value
> looks me too high .
> Is my reasonement wrong ? or the wind factor very important to get
> correct value
>
> I know that my car cant have more than 185 nm of torque !
>
> Thanks, and sorry for my poor english

I have not had time to go through your math. This is what I get. I
changed the space to - to keep it lined up but it also makes it a little
harder to read.
Stan

---------------------------Rear------Aero-----Rolling------------Rear-W---Accele
--RPM------MPH---Velocity--Wheel----dynamic---Resist.--Elapsed----Horse---ration
------------------ft/sec--Torque---Drag---HP----HP------Time------Power---in-G's

-2029.0--30.944---45.384-1277.15-----1.561----3.547-----.6829----493.40---2.0655
-2076.0--31.661---46.436--131.03-----1.672----3.630-----.8529-----51.79----.1922

On 21 mai, 16:18, Stan Weiss > wrote:
> florian wrote:
>
> > re all
>
> > I come back cause i have a little matter .
> > Speak with real value:
>
> > car definition :
> > Weight : 1300 kg
> > 3rd gear ration : 4.48 : 1
> > Differential : 1 ( i guess )
> > tire dimension : 175/65 R14
>
> > and these 2 obd2 value : ( time;rpm)
>
> > 0,682926833629608;2029
> > 0,852926835417747;2076
>
> > so .. ( in a metric system )
>
> > /!\ 1 pouce = 25.4 millimetre
> > diameter wheel = (((width *0.Aspect_ratio)*2) +(jante_diameter
> > *25.4)
> > diameter = (175*0.65*2)+(14*25.4) = 583.1 mm = 0.5831 m
> > so circonference = PI * d = 1.831 m
>
> > after we compute the velocity !
> > at 1000 rpm, speed is :
> > 1000(rpm) * ( 1 / Rv ) = Z tr/min
> > Z * 60 = Z tr/h
> > Z*circonference_of_wheel = V en m/h
> > V/1000 = V en Km/h
> > simplification :
> > ((1000/Rv)*60 * Ct )/1000 = V soit (1/Rv) * 60 * Ct = V in hm/h @ 1000
> > rpm
> > for X rpm :
> > (X * (1/Rv) * 60 *Ct )/1000 = V en km/H @ X rpm
> > with Z,X=rpm, Rv = ( gear ratio * diff )
> > this formula is good, i check her with my technical book of my car , i
> > get the right speed at 1000 rpm !
>
> > so .. for our 2 obd2 value !! ( get in 3rd gear )
>
> > to translate km/h to m/S i use the formula : (Speed / 3600 ) * 1000
>
> > 0,682926833629608;2029 --> (2029 * (1/4.48) * 60 *1.831) / 1000 =
> > 49,75 km/h - > 13.819 m/s
> > 0,852926835417747;2076 --> 50,90 km/h -> 14.138 m/s
>
> > now i use the acceleration formula : a = (v2-v1) / (t2 - t1) = 0.31 /
> > 0.17 = 1.88 m/s²
>
> > we know that force = mass * acceleration : 1300 * 1.88 = 2444 newton
>
> > and work(nm) = force * displacement = 2444 * 0.31 = 757.64
> > newton.meter or 757.64/1.356 = 558.7 lb-ft
>
> > i know that i havent applie the wind drag factor yet, but this value
> > looks me too high .
> > Is my reasonement wrong ? or the wind factor very important to get
> > correct value
>
> > I know that my car cant have more than 185 nm of torque !
>
> > Thanks, and sorry for my poor english
>
> I have not had time to go through your math. This is what I get. I
> changed the space to - to keep it lined up but it also makes it a little
> harder to read.
> Stan
>
> ---------------------------Rear------Aero-----Rolling------------Rear-W---A*ccele
> --RPM------MPH---Velocity--Wheel----dynamic---Resist.--Elapsed----Horse---r*ation
> ------------------ft/sec--Torque---Drag---HP----HP------Time------Power---i*n-G's
>
> -2029.0--30.944---45.384-1277.15-----1.561----3.547-----.6829----493.40---2*.0655
> -2076.0--31.661---46.436--131.03-----1.672----3.630-----.8529-----51.79----*.1922- Masquer le texte des messages précédents -
>
> - Afficher le texte des messages précédents -

Thanks a lot stan, but im unable to read your post, desciption is up
side down .
I "ve find a mistake in my reasonement, work = force * displacement,
and i get the difference of velocity instead of real displacement . I
see you find the right torque and correct horspower, how do you get
the displacement ??
For displacement, i have this formula, but result seem's to be
unreal !
distance for 1 RPM : d = Circonference / (Gearr * differential) = 40.8
cm , we have 47 rpm, it do 19.2m in 0.17 sec .. my car is a fly

florian wrote:
>
> On 21 mai, 16:18, Stan Weiss > wrote:
> > florian wrote:
> >
> > > re all
> >
> > > I come back cause i have a little matter .
> > > Speak with real value:
> >
> > > car definition :
> > > Weight : 1300 kg
> > > 3rd gear ration : 4.48 : 1
> > > Differential : 1 ( i guess )
> > > tire dimension : 175/65 R14
> >
> > > and these 2 obd2 value : ( time;rpm)
> >
> > > 0,682926833629608;2029
> > > 0,852926835417747;2076
> >
> > > so .. ( in a metric system )
> >
> > > /!\ 1 pouce = 25.4 millimetre
> > > diameter wheel = (((width *0.Aspect_ratio)*2) +(jante_diameter
> > > *25.4)
> > > diameter = (175*0.65*2)+(14*25.4) = 583.1 mm = 0.5831 m
> > > so circonference = PI * d = 1.831 m
> >
> > > after we compute the velocity !
> > > at 1000 rpm, speed is :
> > > 1000(rpm) * ( 1 / Rv ) = Z tr/min
> > > Z * 60 = Z tr/h
> > > Z*circonference_of_wheel = V en m/h
> > > V/1000 = V en Km/h
> > > simplification :
> > > ((1000/Rv)*60 * Ct )/1000 = V soit (1/Rv) * 60 * Ct = V in hm/h @ 1000
> > > rpm
> > > for X rpm :
> > > (X * (1/Rv) * 60 *Ct )/1000 = V en km/H @ X rpm
> > > with Z,X=rpm, Rv = ( gear ratio * diff )
> > > this formula is good, i check her with my technical book of my car , i
> > > get the right speed at 1000 rpm !
> >
> > > so .. for our 2 obd2 value !! ( get in 3rd gear )
> >
> > > to translate km/h to m/S i use the formula : (Speed / 3600 ) * 1000
> >
> > > 0,682926833629608;2029 --> (2029 * (1/4.48) * 60 *1.831) / 1000 =
> > > 49,75 km/h - > 13.819 m/s
> > > 0,852926835417747;2076 --> 50,90 km/h -> 14.138 m/s
> >
> > > now i use the acceleration formula : a = (v2-v1) / (t2 - t1) = 0.31 /
> > > 0.17 = 1.88 m/s²
> >
> > > we know that force = mass * acceleration : 1300 * 1.88 = 2444 newton
> >
> > > and work(nm) = force * displacement = 2444 * 0.31 = 757.64
> > > newton.meter or 757.64/1.356 = 558.7 lb-ft
> >
> > > i know that i havent applie the wind drag factor yet, but this value
> > > looks me too high .
> > > Is my reasonement wrong ? or the wind factor very important to get
> > > correct value
> >
> > > I know that my car cant have more than 185 nm of torque !
> >
> > > Thanks, and sorry for my poor english
> >
> > I have not had time to go through your math. This is what I get. I
> > changed the space to - to keep it lined up but it also makes it a little
> > harder to read.
> > Stan
> >
> > ---------------------------Rear------Aero-----Rolling------------Rear-W---A*ccele
> > --RPM------MPH---Velocity--Wheel----dynamic---Resist.--Elapsed----Horse---r*ation
> > ------------------ft/sec--Torque---Drag---HP----HP------Time------Power---i*n-G's
> >
> > -2029.0--30.944---45.384-1277.15-----1.561----3.547-----.6829----493.40---2*.0655
> > -2076.0--31.661---46.436--131.03-----1.672----3.630-----.8529-----51.79----*.1922- Masquer le texte des messages précédents -
> >
> > - Afficher le texte des messages précédents -
>
> Thanks a lot stan, but im unable to read your post, desciption is up
> side down .
> I "ve find a mistake in my reasonement, work = force * displacement,
> and i get the difference of velocity instead of real displacement . I
> see you find the right torque and correct horspower, how do you get
> the displacement ??
> For displacement, i have this formula, but result seem's to be
> unreal !
> distance for 1 RPM : d = Circonference / (Gearr * differential) = 40.8
> cm , we have 47 rpm, it do 19.2m in 0.17 sec .. my car is a fly

I have a program that I wrote and what I posted is it's output. I did
post this earlier to you.

> average acceleration = (v2-v1) / (t2-t1)
> force = mass * average acceleration
> hp = ((((force * trie_radius) / total torque mult. [gear ratios]) * RPM) / 5252)

In your case v2 = 46.436 and v1 = 45.384, t2 = .8529 and t1 = .6829
Stan

Ok, thank you very much stan, your post was very helpfull i' have
find my mistake in the displacement, results are now correct
Hope this thread could help any people .
I can now work on the wind drag factor and the wheel adherence to
correct these value at any speed .

Hello guys

I come back cause i need your point of view for find the correct
environemental factor who influence the real horsepower.

the last formula give us the engine horsepower .

We can now substract :

- the rolling resistance ( force in newton )
- the wind resistance ( force in newton )
- transmission loss ( coeff of 0.85 on the torque i think ?? )
- moment of inertia ( wheel + transmission + engine ) convert to
energy ??

the last point is my probleme, i dont know if i must use the wheel
moment of inertia , just transmission + engine i guess ? but how find
them ??

Do you see another factor to substract ??

thanks

florian wrote:
>
> Hello guys
>
> I come back cause i need your point of view for find the correct
> environemental factor who influence the real horsepower.
>
> the last formula give us the engine horsepower .
>
> We can now substract :
>
> - the rolling resistance ( force in newton )
> - the wind resistance ( force in newton )
> - transmission loss ( coeff of 0.85 on the torque i think ?? )
> - moment of inertia ( wheel + transmission + engine ) convert to
> energy ??
>
> the last point is my probleme, i dont know if i must use the wheel
> moment of inertia , just transmission + engine i guess ? but how find
> them ??
>
> Do you see another factor to substract ??
>
> thanks


> the last formula give us the engine horsepower .

Wrong. You should have calculated the wheel thrust / torque which you
translated back to engine torque / hp minus all frictional (trans. /
rear) losses. To get engine HP look back at the coast down test that Don
S. talked about some time ago.
Stan

On 30 mai, 05:53, Stan Weiss > wrote:
> florian wrote:
>
> > Hello guys
>
> > I come back cause i need your point of view for find the correct
> > environemental factor who influence the real horsepower.
>
> > the last formula give us the engine horsepower .
>
> > We can now substract :
>
> > - the rolling resistance ( force in newton )
> > - the wind resistance ( force in newton )
> > - transmission loss ( coeff of 0.85 on the torque i think ?? )
> > - moment of inertia ( wheel + transmission + engine ) convert to
> > energy ??
>
> > the last point is my probleme, i dont know if i must use the wheel
> > moment of inertia , just transmission + engine i guess ? but how find
> > them ??
>
> > Do you see another factor to substract ??
>
> > thanks
> > the last formula give us the engine horsepower .
>
> Wrong. You should have calculated the wheel thrust / torque which you
> translated back to engine torque / hp minus all frictional (trans. /
> rear) losses. To get engine HP look back at the coast down test that Don
> S. talked about some time ago.
> Stan- Masquer le texte des messages précédents -
>
> - Afficher le texte des messages précédents -

Ok, you've right, this is wheel horsepower, engine horsepower will be
same with loss .
But for the coast down test, car would have an acceleration, and a
deceleration, its not very userfriendly for an embedded application,
im just trying to resume the coast down test factor without a
deceleration process