Defender Upgearing: College project help

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What Method would you use for uprating the comfortable cruising on a defender?

  • fit an overdrive

    Votes: 7 53.8%

  • Fit a 2nd hand transfer box with lower ratio (i.e 1.222 instead of 1.41)

    Votes: 4 30.8%

  • fit new transfer box gears (this allows more custom tuning of gears)

    Votes: 2 15.4%

  • Other

    Votes: 0 0.0%
  • Total voters
    13
Thor1950 said:
well with 35 inch they suggest 4:12 for 75mph giving max torque and hp on the power curve, through all 5 gears. Think I would and will listen to Ashcroft before any one else so far. Haven't seen anyone on here that would be more of a expert than them
Click to expand...


that may well be the maximum torque output (of the engine they tested on i should point out) for that tyre size on that gearing, but the actual torque at the wheel is reduced.

There is a given amount of energy, (i.e what the engine will produce), this energy is given in the form of work done. - movement

By changing the gearing to mean few rpms for the same rotational speed at the axle, and increasing the moment arm (tyre size) the amount of effort required to maintain that will be increased.

Laws of physics.

Otherwise we would all be running around in cars that produce more energy than they use :)

So given that the amount of torque required will be increased to maintain the movement of the body (vehicle) through the fluid (air) this means that you need to increase the actual torque output of the engine (by putting your foot down a bit more - using more fuel etc).

The change of torque available at the wheel will also mean that you might lose the ability to go up a given gradient of slope in top gear etc.

Which leads you to engine upgrades in order to increase the amount of work the engine is capable of - (more torque i.e bigger hammer!)

So -

Im sure ashcroft are telling the truth in saying that the engine they tested was geared to do 75mph at maximum torque.

BUT

it would not accelerate as fast as a standard defender, and wouldnt have the capability to go up slopes , tow etc . Without engine modifications.

And remember that, ashcroft have supplied that power curve for THEIR engine, not everyones is the same, bit of wear on an injector, wound up turbo etc etc.. all changes things. So optimally, it would be most relevant to get a dyno run on THE engine that the modifications were to be done too.
 
hence why over drive unit is the best upgraded .it gives higher gearing for crusing if needed but is optional ,plus gives extra ratios to deal with more circumstances more efficiently
 
true... and tis an extra button in the landy to play with :)

but there are pros and cons to that also

cons being - cost! something else to break, its another gearbox (so more frictional losses)... talking about it from an engineering point of view, adding ANOTHER gearbox to something that already has loads.....

DISCUSS :p
 
Simplyoliy said:
Hi Guys, hope you all can help.

I'm studying engineering systems at college, we've been asked to do a report into an engineering topic of our choice, so what better than a land rover :D

I've made a poll, its basically looking at the options for reducing the engine load (rpm) for the same speed. from a defender -assuming a good working 200tdi- (options are overdrive, buy a transfer box, new transfer box gears fitted, or other), and favoured method for this. Taking cost into consideration, and maybe mention what you would do if you didn't have to consider costs (as i can't seem to put up 2 poll's!)

Any answers and help would be greatly appreciated.
Click to expand...
bigger engine, higher gears.

what given speed are you looking at, and for what amount of engine rpm?
40 mph in 3rd gear at 3000rpm, 40mph in 4th gear at 2000rpm does what your asking in my disco.

what is required of the "report"?
your asking for alterations or recomendations to an existing, already designed, product.
 
vilguy said:
that may well be the maximum torque output (of the engine they tested on i should point out) for that tyre size on that gearing, but the actual torque at the wheel is reduced.

There is a given amount of energy, (i.e what the engine will produce), this energy is given in the form of work done. - movement

By changing the gearing to mean few rpms for the same rotational speed at the axle, and increasing the moment arm (tyre size) the amount of effort required to maintain that will be increased.

Laws of physics.

Otherwise we would all be running around in cars that produce more energy than they use :)

So given that the amount of torque required will be increased to maintain the movement of the body (vehicle) through the fluid (air) this means that you need to increase the actual torque output of the engine (by putting your foot down a bit more - using more fuel etc).

The change of torque available at the wheel will also mean that you might lose the ability to go up a given gradient of slope in top gear etc.

Which leads you to engine upgrades in order to increase the amount of work the engine is capable of - (more torque i.e bigger hammer!)

So -

Im sure ashcroft are telling the truth in saying that the engine they tested was geared to do 75mph at maximum torque.

BUT

it would not accelerate as fast as a standard defender, and wouldnt have the capability to go up slopes , tow etc . Without engine modifications.

And remember that, ashcroft have supplied that power curve for THEIR engine, not everyones is the same, bit of wear on an injector, wound up turbo etc etc.. all changes things. So optimally, it would be most relevant to get a dyno run on THE engine that the modifications were to be done too.
Click to expand...

takes more power to get thing moving than to maintain the movement, so more torque need at lower speed than at 75-80 mph
 
vilguy said:
that may well be the maximum torque output (of the engine they tested on i should point out) for that tyre size on that gearing, but the actual torque at the wheel is reduced.

There is a given amount of energy, (i.e what the engine will produce), this energy is given in the form of work done. - movement

By changing the gearing to mean few rpms for the same rotational speed at the axle, and increasing the moment arm (tyre size) the amount of effort required to maintain that will be increased.

Laws of physics.

Otherwise we would all be running around in cars that produce more energy than they use :)

So given that the amount of torque required will be increased to maintain the movement of the body (vehicle) through the fluid (air) this means that you need to increase the actual torque output of the engine (by putting your foot down a bit more - using more fuel etc).

The change of torque available at the wheel will also mean that you might lose the ability to go up a given gradient of slope in top gear etc.

Which leads you to engine upgrades in order to increase the amount of work the engine is capable of - (more torque i.e bigger hammer!)

So -

Im sure ashcroft are telling the truth in saying that the engine they tested was geared to do 75mph at maximum torque.

BUT

it would not accelerate as fast as a standard defender, and wouldnt have the capability to go up slopes , tow etc . Without engine modifications.

And remember that, ashcroft have supplied that power curve for THEIR engine, not everyones is the same, bit of wear on an injector, wound up turbo etc etc.. all changes things. So optimally, it would be most relevant to get a dyno run on THE engine that the modifications were to be done too.
Click to expand...

Naaaaaaa, type in your defender engine,transmission,transfercase, size tyre,aand then the recommendations are given. so they are not tweaking anything on the motor.
 
vilguy said:
true... and tis an extra button in the landy to play with :)

but there are pros and cons to that also

cons being - cost! something else to break, its another gearbox (so more frictional losses)... talking about it from an engineering point of view, adding ANOTHER gearbox to something that already has loads.....

DISCUSS :p
Click to expand...

Remember you are in school trying to learn, from proven results. You think you know more than say land rover,or any of the multi billion quid company's like Eaton, spicer, when they product most of the gearing for most machinery that moves in the world?
 
it takes additional power to accelerate an object up to a given velocity, but as that velocity increases the power required to increase the velocity increases exponentially in order to overcome frictional losses - air, tyre to road surface drag etc etc.

So yes... to get an object up to speed does take less power than to maintain that speed once attained, but you need a correspondingly large increase in power.

From memory the rough guide is twice the speed for 4 times the power?
 
Thor1950 said:
Remember you are in school trying to learn, from proven results. You think you know more than say land rover,or any of the multi billion quid company's like Eaton, spicer, when they product most of the gearing for most machinery that moves in the world?
Click to expand...

no.. im not saying that... im saying a statement of fact. :rolleyes:

engineering is about compromises. You CANNOT have everything you want in a product, it is about balancing various attributes to achieve the clients requirement.

If the requirement is to have a higher road speed for the same rpm as the vehicle was originally specced for then other comprises have to be made.

The comprise in all of the methods discussed will be the requirement for additional power to be transmitted - so the cost will be in service life of various components and fuel.
 
vilguy said:
it takes additional power to accelerate an object up to a given velocity, but as that velocity increases the power required to increase the velocity increases exponentially in order to overcome frictional losses - air, tyre to road surface drag etc etc.

So yes... to get an object up to speed does take less power than to maintain that speed once attained, but you need a correspondingly large increase in power.

From memory the rough guide is twice the speed for 4 times the power?
Click to expand...

If I remember back in school 45+ years ago we were taught it takes more to move a stationer object than to keep it moving.

commercial jets use 90-100% power and take off,climb to cruising speed, height then throttle back to 35-40% power to maintain height and speed
 
Thor1950 said:
If I remember back in school 45+ years ago we were taught it takes more to move a stationer object than to keep it moving.

commercial jets use 90-100% power and take off,climb to cruising speed, height then throttle back to 35-40% power to maintain height and speed
Click to expand...

isnt that what i said?

to accelerate an object up to a given velocity takes more power than to maintain it?

also at a higher altitude the air is less dense and so it takes much less power to maintain speed. Drag is reduced see.
 
vilguy said:
isnt that what i said?

to accelerate an object up to a given velocity takes more power than to maintain it?

also at a higher altitude the air is less dense and so it takes much less power to maintain speed. Drag is reduced see.
Click to expand...
no, you said it the other way round!
i were tryin to think how to word it when thor bet me to it.

also to bear in mind, jet engines are direct on line, same as electric motor current draw, stick a gearbox on the end to increase velocity and the power draw will increase.
ive forgot what the original discussion is about now, need to go re read it all!
 
You could always "overgear" it to the extent that you use 4th as your towing gear and 5th as a overdrive cruising gear , I think i just about have this with my 90 with a 1.22 and 265/75 r16 tyres but its an auto so cant really be sure how it would work out with a 5 speed manual ?
 
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