I was just wondering how you work out the bhp of a turbo car. As the turbo does not kick in till about 3000 rpm how can this be a fixed figure? Surely the bhp changes as the turbo kicks in.

This would mean that off boost you would have a different bhp to when you were on full boost. Am I missing something here?

I think the quoted figure for a standard UK classic is about the 215bhp mark but is this at full boost or off boost?

I am very confused. onder2: Can someone please explain?

Thank you in advance!

 

PEAK power figure.....

 

HP is measured and described as *PEAK* HP. Thus 1 car may develop all it's ponies at 5000 RPM describing a peak HP of say 200hp, and an other at 7000 RPM with the same HP. Both would have the same peak HP, but both would drive very differently.

Turbos work with exhaust gasses, obviously if the engine is running and the waste-gate isn't dumping the spent gasses, then the turbo will be spooling. A turbo isn't a binary device it doesn't just switch ON or OFF. It produces boost in a linear fashion in-line with how much load is on the engine. (A certain turbo model has a certain margin of efficiency and is chosen to match the desired characteristics of the engine. )

Thus, to produce a peak HP figure, the engine will be under load, the turbo will be helping to compress air and get as many oxygen molecules as possible into the chamber so that the car's fuel mapping can make use of all that air to produce the max amount of power it's rated to make safely.

Thus yes, the turbo would be spinning to produce peak HP.

 

OK, I understand now. It is amazing how you can drive a car for an extended period of time and still not know how it works!

Was pondering the question on the way into work this morning and knew someone could clear it up.

I know it is better to have more torque as I am guessing your peak power is produced at lower revs. As you have said a turbo delivers power in a linear fashion but due to the lag you get and the turbo normally reaches full capacity reasonably quickly what is the best way to deliver more torque (and then as a result bhp)?

Thanks guys.

 

The easiest way to produce more torque is to increase the capacity of an engine.

Hence the old American saying: "There aint no replacement for displacement!"

The alternative methods involve forced induction (i.e. turbo or supercharging an engine).

Or you could convert to diesel!

NS04