instantaneous hp

[49078]

I'm looking to get some opinions on a home project idea. We are wondering if it is possibile to measure instantaneous hp on a car.

Our current thoughts include using the drag force, mass, and friction to determine the total resistive force on the car. Then using the speed and engine revs calculating hp.

I have done a bit of research online and have not found much so I'm wondering if anyone has done this before. Any thoughts on our current idea?

We could get a dyno reading, have a computer find the engine speed and look up the hp from a programmed curve (found using a dyno) probably. Of course, we don't have a dyno so we're looking for our ways.

Cheers

 

[GregLocock]

That's a good idea. Not very sensitive except in first gear.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[RobWard]

Doesn't the new Veyron display instantaneous HP?
Any ideas how they do it?
(Not cheaply I'd imagine....)

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[GregLocock]

Probably back calculated from TPS and rpm and MAP

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[promp3]

if I understand correctly, you are wanting instant hp ie the power an engine is puting out at any time such as driving at a constant speed wile adjusting for diffrent grades in the road, wind ect.? the only big problem I can see is that it takes so little energy to keep a vehicle moving at a constant speed. we are talking like 10 hp to keep a full sized car going 65 mph
you would have to have a very sensitive and accurate instrement. there is a engine load percentage that is calculated by the ecu and can be read using a obd2 scan tool (at least on my car which was obd2).

if you are talking about geting an on-the-road acceleration number than I cant think of a better way than an accelarometer.(or using that math junk)

I am by no means an expert, I could be totally wrong and usually am.

 

[BobM3]

Engine mount compression would not give you a good dynamic indication of the driveshaft torque. The rotational inertia of the engine would have to be added. Plus you would have to take into account all the stuff hanging off the engine. Exhaust pipes in particular significantly restrain the engine rotation.