WHP vs HP

[n0va91TSI]

I just read somewhere that a WRX STi has 220whp and 300hp at the flywheel.

I have a Talon TSi with 190hp...

Is that rated at the wheel or flywheel?

 

[Lordpaxin]

IMportant question,.


What steps can be taken to REDUCE HP loss on an AWD?

 

[igs]

Originally posted by Groomz
So I was wrong on a few parts. My question is why? Can someone explain why it is a percentage loss versus a specific amount to turn the transmission? It doesn't make sense to me that a transmission could take more power away as the power level increases, as a percentage loss would do. Someone correct me. Being wrong sucks.

because friction is a coefficient

 

[Defiant]

Originally posted by Lordpaxin
IMportant question,.


What steps can be taken to REDUCE HP loss on an AWD?

Make more. Just feed the knuckle-dragging beast.

 

[Groomz]

Can anyone go more indepth about why. I thought ( after being pointed out that I was wrong ) that friction would be the cause. To me there are two things that cause the loss: Mechanical loss and friction loss. I can understand how the friction coefficient would be a percentage, but what about the mechanical loss?

Obviously I am not sure about this. Someone care to help?

 

[SoSprayMe]

Well you know engine horsepower (Gross Horsepower) is measured directly from its source, the flywheel. The flywheel alone puts no load on the engine. And as a result of the engine having no load on it all of the energy it produces is used for making horsepower. Wheel Horsepower (Net Horsepower) on the other hand is measured at the wheels, obviously. The frictional loss between the engine and front and rear wheels will always cause the engine HP to be higher then Wheel HP. There are many factors that affect the whp such as the weight of the car, the transmission, the driveshaft, rear-differential, and four axle shafts. And one other really important factor, probably the most important, the only real reason for a manufacturer to post the HP ratings is for their benefit not yours.

Other then that I really don't know what else to tell you that would help you understand it. .

Regards,

 

[Hooptytalon]

Originally posted by Groomz
Thanks!

Can anyone go more indepth about why. I thought ( after being pointed out that I was wrong ) that friction would be the cause. To me there are two things that cause the loss: Mechanical loss and friction loss. I can understand how the friction coefficient would be a percentage, but what about the mechanical loss?

Obviously I am not sure about this. Someone care to help?

...........the purpose of your engine and drivetrain is to perform "work" (the movement of an object through a distance), there are various ways of getting work done such as your engine converting potential energy into kinetic mechanical energy, to get this kinetic mechanical energy, "torque" to move your wheels you need to be able to control and direct the power flow or torque, which you know is done so thru your flywheel's friction surface to the clutch ....etc etc till it gets to your wheel hubs and rubber to the pavement....this is a system, no system is 100% efficient because there is resistance, mainly resistance in the forms of friction-always present between contacting surfaces of at least 2 objects as they are meshing or moving across one another and inertia-the reluctance of a body to change in its motion. Resistance converts your mechanical energy into heat; when the clutch disc is pressed into the flywheel facing there will be heat from friction and inertia, when a gear is engaged in your transmission you'll have heat from friction between the gears, inertia from the weight of the gears moving the vehicle's weight, and heat from the viscosity(internal friction) of the gear lube. These are a few examples of the inefficiencies in our cars.

 

[ckozlgod]

...........the purpose of your engine and drivetrain is to perform "work" (the movement of an object through a distance), there are various ways of getting work done such as your engine converting potential energy into kinetic mechanical energy, to get this kinetic mechanical energy, "torque" to move your wheels you need to be able to control and direct the power flow or torque, which you know is done so thru your flywheel's friction surface to the clutch ....etc etc till it gets to your wheel hubs and rubber to the pavement....this is a system, no system is 100% efficient because there is resistance, mainly resistance in the forms of friction-always present between contacting surfaces of at least 2 objects as they are meshing or moving across one another and inertia-the reluctance of a body to change in its motion. Resistance converts your mechanical energy into heat; when the clutch disc is pressed into the flywheel facing there will be heat from friction and inertia, when a gear is engaged in your transmission you'll have heat from friction between the gears, inertia from the weight of the gears moving the vehicle's weight, and heat from the viscosity(internal friction) of the gear lube. These are a few examples of the inefficiencies in our cars.

That's a mouth full...you better hope he took physics 101 .

 

[n0va91TSI]

does that mean buying better gear oil can make your car faster? Less energy lost as heat from gear friction. More WHP?

 

[Hooptytalon]

Originally posted by n0va91TSI
does that mean buying better gear oil can make your car faster? Less energy lost as heat from gear friction. More WHP?

My "thought" is it would just balance out; you could pose the exact opposite question...."does buying lower viscosity (SUS) gear lube allow you to put more power to the ground because of less viscosity friction?"
It's really just a trade off, IMO.

 

[ColonelOdem]

OK, so, from what I have gathered and read, the best way to go to 300 with the stage one mods is to do: 2100^ clutch, lightweight flywheel, carbon fiber driveshafts, better driveaxles, aftermarket lsd's, 18x5" aluminum wheels with good tires...Right? that is pretty much lightening up the load as much as possible...

 

[Groomz]

Originally posted by Hooptytalon
...........the purpose of your engine and drivetrain is to perform "work" (the movement of an object through a distance), there are various ways of getting work done such as your engine converting potential energy into kinetic mechanical energy, to get this kinetic mechanical energy, "torque" to move your wheels you need to be able to control and direct the power flow or torque, which you know is done so thru your flywheel's friction surface to the clutch ....etc etc till it gets to your wheel hubs and rubber to the pavement....this is a system, no system is 100% efficient because there is resistance, mainly resistance in the forms of friction-always present between contacting surfaces of at least 2 objects as they are meshing or moving across one another and inertia-the reluctance of a body to change in its motion. Resistance converts your mechanical energy into heat; when the clutch disc is pressed into the flywheel facing there will be heat from friction and inertia, when a gear is engaged in your transmission you'll have heat from friction between the gears, inertia from the weight of the gears moving the vehicle's weight, and heat from the viscosity(internal friction) of the gear lube. These are a few examples of the inefficiencies in our cars.

Thanks for the info. Thanks to SoSprayMe also. Basically it is the friction that is consuming that percentage, either through mechanical action or bearing contacts or anything else that causes friction between the wheels the the flywheel.

 

[SoSprayMe]

Originally posted by Groomz
Thanks for the info. Thanks to SoSprayMe also. Basically it is the friction that is consuming that percentage, either through mechanical action or bearing contacts or anything else that causes friction between the wheels the the flywheel.

Well said Hooptytalon, you elaborated a lot on what I was trying to say. Good thread Groomz.

Much respect,