DHSE Chip vs Gearbox

jerrytlr said:

I love the door analogy - it's great! But torque is not a measure of how much something will turn with a given force.... torque is in fact just a rotational measure of force. If there is no movement, then you can have huge torque with no power. Power is required to move the object (accelerate it or overcome some resistance to movement, or usually both), torque cannot move anything without power (=energy over time).


HTH ;-)

Cheers

Jerry

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There can be no torque in an engine unless it's turning. You can have very powerful short stroke engines with little torque and quite small long stroke engines with lots of torque. Torque is the twisting force applied to the crankshaft by the conrod as the piston is forced down.

wammers said:

There can be no torque in an engine unless it's turning. You can have very powerful short stroke engines with little torque and quite small long stroke engines with lots of torque. Torque is the twisting force applied to the crankshaft by the conrod as the piston is forced down.

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Not STRICLY true Wammers - what you say holds up for a reciprocating internal combustion engine, but only because of the way it is designed to work.

Consider an electric motor - you can apply a current, and hold it static with an equal force. There would be no net movement, therefore no 'power' is being produced... But it WOULD be producing a hell of alot of torque!

Clarky130 said:

Not STRICLY true Wammers - what you say holds up for a reciprocating internal combustion engine, but only because of the way it is designed to work.

Consider an electric motor - you can apply a current, and hold it static with an equal force. There would be no net movement, therefore no 'power' is being produced... But it WOULD be producing a hell of alot of torque!

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But we are not talking electric motors Clarky we are talking suck, compress, bang motors. Unless the engine is running (power being applied) there can be no torque. Same with the leccy motor actually, switch off the power no torque. Bit of a silly arguement actually.

jerrytlr said:

I love the door analogy - it's great! But torque is not a measure of how much something will turn with a given force.... torque is in fact just a rotational measure of force. If there is no movement, then you can have huge torque with no power. Power is required to move the object (accelerate it or overcome some resistance to movement, or usually both), torque cannot move anything without power (=energy over time).


HTH ;-)

Cheers

Jerry

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you cant have torque without power .power is the engine output, torque and speed (rotationally )vary

Clarky130 said:

Not STRICLY true Wammers - what you say holds up for a reciprocating internal combustion engine, but only because of the way it is designed to work.

Consider an electric motor - you can apply a current, and hold it static with an equal force. There would be no net movement, therefore no 'power' is being produced... But it WOULD be producing a hell of alot of torque!

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It won't be producing any torque as it is not moving, it does have the potential to produce torque once it is allowed to rotate.

The amount of torque would then be proportional to the amount of power supplied and the number of case or field windings (depending on type).

Torque is a measure of force produced through an angular rotation, no rotation= no force= no Torque

TCubed said:

The thing I still don't quite understand is how the increased torque from the engine maps to the various gears. As in, 4th high will have very little torque while 1st low's will be colossal. Is it therefore just the lower gears (and low range) which are at risk, and if so, are they only so if forced to undergo harsh acceleration?
(I'm a chemist, not a physicist!)

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He he! This thread is getting complicated and I'm just going to add a little bit more to the confusion!

The Hi-lo box is irrelavant to the torque the gearbox 'feels', it's downstream of the gearbox. The driveshafts and wheels will get a whole heap of extra torque in low range but not the gearbox. The gearbox 'feels' the torque from the engine crankshaft. This will actually be the same regardless of what gear the gearbox is in. The input shaft is fed from the crankshaft through the torque convertor. So the input shaft 'feels' the same torque everytime you accelerate. What changes is the resistance on the output shaft. In this sense is a kickdown at motorway speed (sustained maximum torque) more onerous than a blast from the lights (peak torque as the lights change and at each gearchange but reduction in torque as the revs rise)?

Datatek has long warned of the torque limitations of the HP22 gearbox but I'm not aware of what actually fails.

My own thoughts are mixed on this. I've run my DSE with a chip in it for the last 75,000 miles (145,000 total) without problem but I don't cane it often. I would have thought that the torque convertor would buffer a lot of the 'over torque' that the chip gives the engine. What is significant though is the way the turbo diesel torque is delivered, it comes in with a bang in a way that a normally aspirated petrol doesn't. I could easily see how the extra torque could do in a convertor but I don't think this is what we are talking about in terms of gearbox failure so without seeing what fails in the gearbox I'm not fully convinced that it is going to be terminal in every instance.

My own gut feeling is that gearbox failure will be as a result of a combination of factors. I think the removal of the dipstick on post 99 models was suicidal. I'd wager that failure is more common in late models than early ones and has as much to do with quality/level of oil as it is to do with over torquing the box.

With overtorquing you would expect to see twisted input/output shafts and mis-shapen gear teeth. Until I see that, I'm going to keep blaming maintenance more than design.

Usually the one way clutches that fail over time.

Saint.V8 said:

It won't be producing any torque as it is not moving, it does have the potential to produce torque once it is allowed to rotate.

The amount of torque would then be proportional to the amount of power supplied and the number of case or field windings (depending on type).

Torque is a measure of force produced through an angular rotation, no rotation= no force= no Torque

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Again, not strictly true. Consider an electric motor, with a bar on the output shaft at right angles, and sitting at 90 deg to straight down, with a weight on the end of it. Apply power to the motor, equivalent to the force gravity imparts on the weight. The weight will not move, but the motor is still producing a rotational force (torque).

If that bar was 1 ft long and the weight was 1 lb, it would be producing 1 ft lb of torque.

Wammers is correct as applied to combustion engines, because they need to be turning before they can generate ANY force - but the same isn't true of electric motors - they produce their full torque capacity from ZERO rpm.

Yes, I know, it's a daft argument... I just can't help being a pedant!

Clarky130 said:

Again, not strictly true. Consider an electric motor, with a bar on the output shaft at right angles, and sitting at 90 deg to straight down, with a weight on the end of it. Apply power to the motor, equivalent to the force gravity imparts on the weight. The weight will not move, but the motor is still producing a rotational force (torque).

If that bar was 1 ft long and the weight was 1 lb, it would be producing 1 ft lb of torque.

Wammers is correct as applied to combustion engines, because they need to be turning before they can generate ANY force - but the same isn't true of electric motors - they produce their full torque capacity from ZERO rpm.

Yes, I know, it's a daft argument... I just can't help being a pedant!

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That is refered to as the Torque Moment, not strictly what is refered to as Torque...

I (Shamefully) quote from the Evil Wiki, as I am not eloquent enough to be able to type it and explain myself:

For example, a rotational force applied to a shaft causing acceleration, such as a drill bit accelerating from rest, the resulting moment is called a torque. By contrast, a lateral force on a beam produces a moment (called a bending moment), but since the angular momentum of the beam is not changing, this bending moment is not called a torque. Similarly with any force couple on an object that has no change to its angular momentum, such moment is also not called a torque.

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Think we all know what we are torquing about. But it's no good torquing about what is not applicable.

wammers said:

Usually the one way clutches that fail over time.

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Thanks Wammers,

Are the one way clutches one of the parts that are different between the HP22 and HP24?

free wheel clutch in clutch pack C is stronger as is the clutch pack itself and clutch pack A is beefed up too

jamesmartin said:

free wheel clutch in clutch pack C is stronger as is the clutch pack itself and clutch pack A is beefed up too

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Well folks, I think there is our answer.

The parts that are failing in the HP22 are beefed up in a HP24.

James, as a gearbox builder, do you think the clutch packs are failing through poor maintenance, accelerated wear or from excessive torque?

oil changes are important ,(issues can occur with putting fresh in after leaving old in far too long as is highly detergent) harshness of the diesel torque on those boxes ,rarely to you get a phone call on a petrol ,when setting off and during gear change etc

Clarky130 said:

Again, not strictly true. Consider an electric motor, with a bar on the output shaft at right angles, and sitting at 90 deg to straight down, with a weight on the end of it. Apply power to the motor, equivalent to the force gravity imparts on the weight. The weight will not move, but the motor is still producing a rotational force (torque).

If that bar was 1 ft long and the weight was 1 lb, it would be producing 1 ft lb of torque.

Wammers is correct as applied to combustion engines, because they need to be turning before they can generate ANY force - but the same isn't true of electric motors - they produce their full torque capacity from ZERO rpm.

Yes, I know, it's a daft argument... I just can't help being a pedant!

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What he says

Another illustration - your trusty torque wrench can apply lots of torque to a bolt or nut without it actually moving at all. Remember when you retorqued your cylinder head bolts after replacing the head gasket? LOTS of torque but for those bolts already tight enough, NO movement at all!



Cheers,

Jerry

jerrytlr said:

What he says

Another illustration - your trusty torque wrench can apply lots of torque to a bolt or nut without it actually moving at all. Remember when you retorqued your cylinder head bolts after replacing the head gasket? LOTS of torque but for those bolts already tight enough, NO movement at all!



Cheers,

Jerry

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Not unless you pull on it (apply power) it can't.

jerrytlr said:

What he says

Another illustration - your trusty torque wrench can apply lots of torque to a bolt or nut without it actually moving at all. Remember when you retorqued your cylinder head bolts after replacing the head gasket? LOTS of torque but for those bolts already tight enough, NO movement at all!



Cheers,

Jerry

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Unfortunatly not, you were applying a Turning Moment through the wrench, that is designed to 'break' at a set Torque Moment, you are not using an angular force to accelerate an object, which is the Torque produced from a rotating object (the engine) rather you are providing a Turning Moment through the Torque Wrench to provide a Moment of Torque...

I think we are talking cross purposes....we are both right, I think it is just a confusion between the Torque Produced by and Engine and the Torque Applied throguh A Turning Moment...

They aren't interchangable, but in essence are the same measurement, but for different applications...one is a force applied and one is a force generated.

Saint.V8 said:

Unfortunatly not, you were applying a Turning Moment through the wrench, that is designed to 'break' at a set Torque Moment, you are not using an angular force to accelerate an object, which is the Torque produced from a rotating object (the engine) rather you are providing a Turning Moment through the Torque Wrench to provide a Moment of Torque...

I think we are talking cross purposes....we are both right, I think it is just a confusion between the Torque Produced by and Engine and the Torque Applied throguh A Turning Moment...

They aren't interchangable, but in essence are the same measurement, but for different applications...one is a force applied and one is a force generated.

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I think we might all be right here, depending on the situation you apply it to! In order to move an object, you have to apply force to it over time (power). The force is torque, the resultant motion of the object is due to power.

Anyways, I need to go and give my Panhard rod bolts a serious 'torqueing' to...

jerrytlr said:

What he says

Another illustration - your trusty torque wrench can apply lots of torque to a bolt or nut without it actually moving at all. Remember when you retorqued your cylinder head bolts after replacing the head gasket? LOTS of torque but for those bolts already tight enough, NO movement at all!



Cheers,

Jerry

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Nope, lots of force and bending moment, no torque. For it to be defined as torque it must achieve rotation. Torque is a force couple. Angular rotation is inherent in the definition.

Its a technicality, the SI unit for moment and torque is the same, N.m (or lb.ft). A static structure gets a bending moment which is measured around a reaction point but doesn't move per se (it deflects). Apply the same moment to a shaft and you get rotation. So while you were applying a force to the torque wrench through the lever arm of the handle its a torque as long as the bolt is turning. When it stops turning its resisted by the engine mountings and suspension until it ultimately is resisted by the ground. While the bolt was turning you were appying a torque, when it stopped moving you were applying a moment.

mcapinha said:

Correct me if I'm wrong, but isn't the ZF4HP22 rated up to 380Nm, the same as the R380 manual box ? I've done a quick search on the interwebs and there are some posts agreeing with this. I then took a look at a remapped 2.5 DSE max torque and it was around 340Nm...
http://www.tecnauto.com/images/testes/RangeRover25dse_chip.pdf

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The figure I got from the nice man at ZF in Germany was if I remember correctly around the 300Nm mark for the ZF4HP22 and 380Nm for the 24.
To survive the diesel torque, the auto ECU requests a power reduction before a gear shift takes place, when a power box is fitted this is to some extent negated as it is with a remap unless the remap is very clever and changes the power reduction map as well