[4ePikanini]

i'm not too sure

diesel burns slower and you can run it rich or lean without detrimental effects like petrol engines.
diesel engines are always wide open throttle and the amount of diesel added gets changed (and timing thereof) effectively pumping more air in and out - i think this is the reason
diesel has chemically more power per liter than petrol
diesels usually have longer strokes as well. long stroke = slower = torque. short stroke = high rpm = lower torque but more KW at very high revs.

[Mcnoogle]

The question is also why would two basically same engines produce different KW: examples -GTO 3.0 V6 24V with +-165 kW against 3.5 V6 24V with +- 153kW (figures approx)
Hbannik's 6G72 import against local Samcor 6G72 (no figures) or basically how do the one produce more or less kW than the other?

Hi Cobvs,

Once again, don't quote me on this, as I am still learning all this myself, but looking at the GTO motor vs the 3.5 V6,
keeping in mind what Colin, Henk and a few others have mentioned, you have to look at the overall setup, do they have the same chip, is the engine mapping the same on both, do either or both have a free flow / enhanced system regarding exhaust removal, what size are the cams on both, how are the MAF sensors calibrated (there's so much more to it than just the engine block) so unfortunately, I don't think any one can answer that question with a straight forward answer.
Furthermore, the GTO is a 3.0l V6, whereas the 2nd is a 3.5l V6, so not quite the same, you will probably find, that my
3.5 V6 gives 153Kw @ 3500rpm (example only, as I really don't know), whereas the 3L could give 165Kw @ say 5000rpm, showing a completely different power curve (is that right) which means that the mapping, chip, etc would definitely be different, so although you think they're basically the same, they are in fact inherently different, and cannot be compared.
a better question would be why does a pajero2 3.5l V6, 24 Valve DOHC give 153Kw
yet a Toyota Highlander with basically the same 3.5l V6, 24 Valve DOHC give 200Kw, as these look basically the same but even then are still not, I see the Toyota engine is also a VVT-i (whatever that is)
Even with Henks import, you'll probably find the engine mapping slightly different, as is probably set up for a different quality / octane fuel (being imported from Japan) but as I said, please don't quote me, as I honestly know NOTHING about cars, this is as much a learning curve for me as it is for you, if not more.
Hope this helps

[4ePajero]

Lets re-cap.

Diesel engines produce more torque because of

• higher compression ratios
• slower burning fuel
• longer stroke means larger crank throw, which means longer lever arm, which means more torque.

Torque is a measure of a force, measured in Nm. 1 Nm is the force exerted if a mass of ±0.1kg (thanks for the correction, Gerrit) is hung on a 1m lever. Time is not part of torque, in other words, even if the weight hangs there statically, it exerts a force of 1Nm (torque).

kW is a measure of work. Time comes into play. 1 kW is the work done at a rate of 1 joule per second.
If that weight now moves through 1m in 1 second, 1 watt of work has been done.

An example:

See the hand pump (used to pump water from a well or bore hole

It consists of

• a handle / lever
• a sleeve
• a rod with a piston on the end, which fits into the sleeve and has a one-way valve in it (water can only flow upwards through it)
• another (static) one-way valve, at the bottom of the sleeve

To pump water from the well, the water is lifted by the piston and will flow out through the spout.

The flow of water pumped per (say) a minute, (the output) can be seen as work (kW). The flow is dictated by two things:

• the flow per stroke
• the number of strokes per minute

The flow per stroke is determined by

• the diameter of the sleeve
• the length of the stroke

Now lets look at ways of improving the output

• 1. Increase the diameter of the sleeve
• 2. Increase the length of the stroke
• 3. Increase the number of strokes per minute

1. Increase the diameter of the sleeve.

This will work but let's say we increase the diameter to 6meters!
This will surely increase the output, but a very large force (Nm) will be required to lift the now massive column of water.
This can be achieved by using a stronger operator eg King Kong. A child will not be able to use the pump
..... except if we increase the length of the lever. This will multiply the child's effort and is equivalent to adding a transmission / gearbox (torque multiplier). The length of the lever will however limit the speed at which the piston will move

2. Increase the length of the stroke

This will increase the volume per stroke but decrease the number of strokes possible in the minute.

3. Increase the number of strokes per minute

This will obviously work, but the number of strokes per minute is surely determined by the force necessary to move the column of water and the length of the rod.


Conclusion:
For the same output, we can thus use either of

• King Kong with a large diameter piston, at a leisurely pace
• a child, with a small diameter piston, but at a frantic pace

Put differently, for an engine to output the same kW, you can use either of

• diesel (King Kong). Lots of torque, but at low rpm
• petrol (child). Less power, but at higher rpm

If your requirement is to have lots of water per stroke, you can either use more volume per stroke (high torque) or more strokes per minute (high rpm).

[Gerrit Loubser]

Good analogy, Mr. 4E

1 Nm is the force exerted if a mass of 1kg is hung on a 1m lever.

Just one comment. 1 Nm is actually the torque exerted by about 0.1 kg hanging at the end of a 1m lever on earth.

0.1 kg x 9.81 m/s/s = 0.981 N

[4ePajero]

Good analogy, Mr. 4E

1 Nm is the force exerted if a mass of 1kg is hung on a 1m lever.

Just one comment. 1 Nm is actually the torque exerted by about 0.1 kg hanging at the end of a 1m lever on earth.

0.1 kg x 9.81 m/s/s = 0.981 N

As usual, I am corrected by Mr Loubser!
Of course you are correct, and I bow to your technical review!
(Original post fixed)

[4ePajero]

Good reading (with pictures! ) can be found here

Follow the links at the bottom of the last page.

[Cobvs]

Comparing two 6G72 3.0 V6 engines should be mostly the same. The block, crank, piston size and stroke of the pistons should be the same, right, that's what 6G72 mean to me. If it changes any of these then it becomes 6G74 3.5 V6 for example. You can fit a 12V SOHC or a 24V DOHC head on this block and obviously have different output but if you have two 24V DOHC heads and you have a 30kW odd difference then there must be some components that are different in the two heads? If not then we go to EMS and mapping which will mean that one should be able to get engine with lower kW up to same output as higher kW engine by mapping, right?

4eP snr - nice to explain a more complicated concept

VVTi is for variable valve timing and i for injection I think

[Gerrit Loubser]

It's not all about the electronics. The character of the engine (e.g. bias towards more torque at lower engine speeds vs. bias towards more power at higher engine speeds) is determined in a big way by the profiles of the cams and they may differ greatly in different versions of the same engine intended for different applications. The flywheels may also differ.

[Cobvs]

Thanx Gerrit that make sense yes. It's in the heads then as well as EMS, like in most cases and as most said on this thread a combination of factors. Changing heads from a higher kW engine to lower on same block will then also need changing EMS with it I suppose. Just another question in the learning curve but what physical components make up the EMS?