Discussion
Emmyrajah said:
How do i verify and check whether the bhp and torque figures given by the manufacturer are true without using any machinery
You don't.Even if you put the car onto a rolling road dyno, there's going to be some frig factor to turn the "at-wheel" figures into "at-flywheel". To properly measure at-flywheel figures, you need to take the engine out and put it into a proper test-bed.
Go on, why do you want to...?
daddy cool said:
Emmyrajah said:
How do i verify and check whether the bhp and torque figures given by the manufacturer are true without using any machinery
Find another car with a quoted bhp/torque slightly less than yours. Race them at the traffic lights. If you win, sleep easy.Emmyrajah said:
How do i verify and check whether the bhp and torque figures given by the manufacturer are true without using any machinery
The manufacturers are required to certify the power produced by there vehicles to a hugely complex and tightly controlled series of regulations, using multimillion pound facilities designed to measure those parameters.You, at best, can run your car on a set of chassis rollers, which will have little traceability or correlation to anything, and measure power at the wheels, and have a result that has a huge number of interrelated factors that all affect the value recorded.
So, if say Ford says "your car makes 150 bhp" then i'd just take that as gospel!
(and as mentioned, who cares? the only reason you need to know a power figure is for pub ammo, in the real world it's irrelevant.......)
But without machinery, then vlog equipment, time 0-60
Calculate using simple physics the force required to accelerate known mass and the known rate.
Work out axel torque from force and wheel size, then calculate via gearing the torque at the crank and from revs the bhp.
Then add all the nesessary frog factors to compensate for 101 things such as bearing losses, wind resistance, tyre deflection passenger weight, electrical load
Then you will have a reading which may or may not match
Wrote an excel spreadsheet once that modelled the acceleration of a car from first principles, in increments of 0.1s. It was surprisingly accurate in its way, but nowhere accurate enough to really tell anything useful, just fun to do.
Calculate using simple physics the force required to accelerate known mass and the known rate.
Work out axel torque from force and wheel size, then calculate via gearing the torque at the crank and from revs the bhp.
Then add all the nesessary frog factors to compensate for 101 things such as bearing losses, wind resistance, tyre deflection passenger weight, electrical load
Then you will have a reading which may or may not match
Wrote an excel spreadsheet once that modelled the acceleration of a car from first principles, in increments of 0.1s. It was surprisingly accurate in its way, but nowhere accurate enough to really tell anything useful, just fun to do.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff