200tdi defender engine turbo questions

[Aragorn]

jmattley: not really, fuel injected is proportional to throttle angle, and quite often engines are more efficient at higher RPM's so 3000rpm can actually use less fuel than 1500rpm.

You dont actually need gobs of torque to make your motor accellerate. Torque is simply an instantaneous force applied by the engine to the drivetrain. Power on the other hand is a measure of the total energy exerted (ie work done). You have more power at 3000rpm than you do at 1900rpm, so you will be able to do more work (ie more accellerating). Rate of accelleration follows the power graph on any vehicle, not the torque curve. People with turbodervs seem to obsess over their magical torque values but in reality it means nothing in the real world other than having slightly different gearing to a more powerful less torquey engine.

I dont mean cruising along at 3000rpm anyway, i just mean that when actually accellerating, giving it some revs is much kinder for the box then flooring it at 1700rpm, riding the torque peak until 2500 then shifting and repeating the whole process.

[LandyManLuke]

You dont actually need gobs of torque to make your motor accellerate.

You do need torque though. Angular acceleration is directly related to net torque.

Torque is simply an instantaneous force applied by the engine to the drivetrain. Power on the other hand is a measure of the total energy exerted (ie work done).

More accurately, Power is Torque x Angular velocity.

You have more power at 3000rpm than you do at 1900rpm,

This follows from my previous, above...

so you will be able to do more work (ie more accellerating). Rate of accelleration follows the power graph on any vehicle, not the torque curve.

Because you're able to generate more torque at the wheels.

Ultimately, to accelerate, you need to generate a positive net torque, at a speed. That requires power. how you generate the power doesn't matter a great deal, as long as the gearing makes it useable at the wheels.

[Aragorn]

Ye, thats a more thorough explanation, but my point holds, horsepower is what you want.

The torque spike in a TDi makes it FEEL like its accellerating faster around the spike, but thats because a spike of torque like that causes a increased rate of change of accelleration. The actual rate of accelleration at 3500rpm is still higher than it is at 2500rpm, regardless of how it feels!

Forget about the engines torque output, unless your worrying about breaking gearboxes!

[nige90]

horsepower is what you want.

!

Forget about the engines torque output, unless your worrying about breaking gearboxes!

Have to disagree. In a light vehicle or motorbike then yes, but a heavy Landy torque is far more

useful. Who wants to have to cog it down and boot it to get anywhere ? Nope, sheer grunt (aka torque)

for me anytime.

Take a truck for example, typically 400 horses, about the same as an Evo but 1000+ ft/lbs.

Vehicle weight plays a major part.

IMO people are obsessed with BHP because it's the most used figure to pitch an engine.

[Aragorn]

The reason a "torquey" engine seems more powerful is nothing to do with the weight. Its because if you have a huge torque spike at 1900rpm you have more POWER at 1900rpm than you would have without the torque spike.

A naturally aspirated engine be it a 1.2 3cyl or 4.6L V8 tends to have quite a linear power delivery, with the torque climbing up to a plateau, sitting there for a while then falling off again:

http://www.rri.se/spec/view/png/graph/STR-01030601-kW-Nm-C.png

TDi's on the other hand tend to rapidly climb to a torque peak very early on and then head downhill from there:

http://www.rri.se/spec/view/png/graph/STR-97070401-kW-Nm-C.png

End of the day its the area under the POWER graph that dictates your accelleration.

Your example of a truck is all well and good, but the fact of the matter is it needs 400hp to move, and because the engine doesnt rev, you need to be generating 1000lbft to actually make 400hp before you run out of revs.

Had you fitted it with an evo engine, producing the same power and a 3rd of the torque, but also spinning 3 times faster, and stuck a 3:1 gearbox between the engine and the transmission, you'd have EXACTLY the same performance as the slow revving truck engine.

[Mo Murphy]

Just to reiterate what others have posted above, running a Tdi without the turbo would seem to me to be a pointless exercise.

Mo

[discomikey]

the 300TDI manifold should fit, see no reason why because from what i understand, the defender and disco engines are exactly the same, just the defender one had a modified exhaust manifold to accomodate for the lower position in the chassis rails, hence the turbo on top not on the bottom. IIRC the block however is exactly the same.

dont kill me if im wrong

[ian_s]

over the years i've killed about 4 series gearboxes, mainly down to my driving (i'm not exactly a sedate driver...)

only one of these boxes died behind the tdi, the others were with the standard 2.25 diesel. i dont think the tdi had anything to do with breaking the box, as it had almost no oil in it when i drained it.....