Thread: 700Nm puma ???

Originally Posted by c.h.i.e.f

I doubt there will be any arguments now after that

Only because we have no idea what it means. Pat

Originally Posted by Bush65

Given 140kW and 700Nm, but not knowing at what rpm. It does look like 700Nm is an error (as discussed in some posts above).

Power is force x velocity (linear motion) or when converted to circular motion terms and SI units, Power (watts) = 2 x pi x Torque (Nm) x revs per second. If power is in kW then use torque in kNm.

If the peak power is developed at say 3000 rpm, i.e. 50 rev per sec, then:
Torque (kNm) = 140 (kW) / [2 x 3.14 x 50 rev/s] = 446 Nm

That torque value is most likely on the high side for a Puma engine as the peak power is most likely achieved at higher rpm.

Now if the peak torque is developed at 2000 rpm, i.e. 33.3 rev per sec, then:
Power (kW) = 2 x 3.14 x 0.7 kNm x 33.3 rev/s = 146.6 kW

Once again that power is most likely too high at those rpm for a Puma engine.

The conventional engineering measure for comparing performance of different engines, of the same type but different displacement, is BMEP (brake mean effective pressure).

BMEP is the equivalent average pressure acting on a piston over the thermodynamic cycle (2 revs for a 4 stroke engine) and is calculated from the torque measured on a dynamometer (dynos were commonly called brakes because a method of braking is used to apply a load on the engine), divided by the engine displacement.

Pressure is produced by heating the air in the combustion chamber from burning fuel (more pressure requires more fuel to be burnt) and by basing it on the torque from a dyno, BMEP takes all engine losses, friction, etc. into account.

BMEP (Pa) = 2 x pi x Torque (Nm) x rev per cycle / displacement (cubic metre)

For a 4 stroke engine and converting displacement to litres this can be simplified to:
BMEP (Pa) = 12566 x Torque (Nm) / displacement (litre)

Now for a 2.4 litre Puma, to produce a torque of 700 Nm then:

BMEP = 12566 x 700 (Nm) / 2.4 (litre) = 3665 kPa or 36.65 bar



A quick search of the internet produced typical figures of :

• 7 to 9 bar for a NA diesel
• 14 to 18 bar for a turbo diesel
• 14.6 bar for a 755 HP, 2.4 litre, V8 race car engine
• 80 to 100 for top fuel dragsters

It would be interesting to see some figures for a range of modern common rail diesels.

So 36.6 bar from a Puma is not too scruffy. IMHO it ain't going to happen because peak cylinder pressures and temperatures will be far too high for the piston material to withstand.

isnt there also something about the piston count, cycles, bore,stroke and crank throw that comes into it for working out the cylinder pressure...

it comes into it when you go the other way working out the theoretical power output from an engine

Originally Posted by Blknight.aus

isnt there also something about the piston count, cycles, bore,stroke and crank throw that comes into it for working out the cylinder pressure...

it comes into it when you go the other way working out the theoretical power output from an engine

I'm taking no sides as pat said cannot understand all of what was said but I'm guessing it will be calculated via the capacity,cylinders and the "supposed" output figure that was claimed...the part we do not have is the rpm to work with so it's a bit annoying in opinion...
As you said previously blknight even if it could get those figures I doubt it will hold up....

I think I'll stick to the tried and tested "It didn't happen without pictures". If only the magazine had printed the dyno output..........

Originally Posted by TimNZ

I think I'll stick to the tried and tested "It didn't happen without pictures". If only the magazine had printed the dyno output..........

Proves nothing - as mentioned (by dougal?), if you put the wrong gear ratio into the dyno you can get whatever torque numbers you want...

I agree with John's calcs.

I know how he did it....

700Nm...

he didnt say 700Nm @ X rpm for 140KW...

so hes got a puma engine that can make 140 KW I can buy that....

how much powers in a startermotor? how much reductions on the ring gear? whats the ring gear radius?

ok so if a ****y tdix00 startermotor can undo a bolt thats been done up to 400Nm AND locktited given that it takes more torque to break out a bolt than to do it up... The Puma must have a better startermotor (puma drivers tend to claim that everything about the puma is better than everything else out there, why shouldnt it apply to the starter motor) its got near enough the same sized flywheel....

I bet he just started it in gear and the dyno was reading the applied torque of the starter motor on the flywheel as measured at the center of the flywheel...

see you can get 700Nm off of the flywheel of a puma...

Hey heres a thought....

what happens if you put too much resistance onto a puma on a dyno...

Originally Posted by Blknight.aus

isnt there also something about the piston count, cycles, bore,stroke and crank throw that comes into it for working out the cylinder pressure...

it comes into it when you go the other way working out the theoretical power output from an engine

BMEP is basically output relating to engine displacement. Piston count, bore/stroke etc are used in the displacement part but that's it.

Originally Posted by Blknight.aus

I know how he did it....

700Nm...

he didnt say 700Nm @ X rpm for 140KW...

so hes got a puma engine that can make 140 KW I can buy that....

how much powers in a startermotor? how much reductions on the ring gear? whats the ring gear radius?

ok so if a ****y tdix00 startermotor can undo a bolt thats been done up to 400Nm AND locktited given that it takes more torque to break out a bolt than to do it up... The Puma must have a better startermotor (puma drivers tend to claim that everything about the puma is better than everything else out there, why shouldnt it apply to the starter motor) its got near enough the same sized flywheel....

I bet he just started it in gear and the dyno was reading the applied torque of the starter motor on the flywheel as measured at the center of the flywheel...

see you can get 700Nm off of the flywheel of a puma...

Hey heres a thought....

what happens if you put too much resistance onto a puma on a dyno...

Yes at like 30,000rpm the torque may be 700nm lol