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1.4 Defender Transfer box v 1.2 Discovery 1 Transfer box "Phenomen

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The higher BHP on autos may just be moving some power up the rev range, rather than actually doing anything radical - multiplying the same torque by a few hundred extra RPM will add BHP easily.

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The higher BHP on autos may just be moving some power up the rev range, rather than actually doing anything radical - multiplying the same torque by a few hundred extra RPM will add BHP easily.

I thought that the power figures were taken at the flywheel, and would therefore be independent of any gearbox/torque converter set-up.

Mike

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I thought that the power figures were taken at the flywheel, and would therefore be independent of any gearbox/torque converter set-up.

Mike

I suspect Fridge is referring to:

HP = torque x rpm /5252

This means you only need to make the same torque a few rpm higher to get more HP

and/or

Make more torque at the same rpm to get more HP

This is done on the EDC 300Tdi, probably be means of slightly higher boost and maybe slightly altered fuelling.

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Chicken drumstick

Be thankful, my 90 filled with tools and loaded To the roof typical on 255 85 16 tyres and a1:1.003 transfer box. Motorway are ok but it doesn't like long hills!

4th and 3rd get used a lot don't get into 5 th until 62mph sat nav cruised to the Nationals loaded up in 5th on slightly smaller 235 diamonds singing away about 75 all the way (except for hills)

I'll get around to fitting the 1.4 at some point so it can tow the trials motor

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I've got one an LT230 1.4 to refurbish and a Pto if it doesn't sell and I can get a clean route to the rear X member. (90)

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Thank you, CD. Again, it's a case of BS baffles brains, So, it is a case of higher boost and tweaking the fuelling to achieve higher bhp at the flywheel. Any talk of torque converters is part of the BS, and has nothing to do with power at the flywheel.

Mike

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Re the extra power in a TDI 'auto'. I persoanly suspect that the electronic control allows a more complex fuel map while still complying with the emissions regs. A mechanical injection pump can only have a simple fuel map by comparision, i.e. a certain rate of fuel increase per rev , etc. When this comes up from time to time I always end up wondering why electronic fuel pumps for TDI's are not sought after items as they will allow more flexibility for tuning as well I suspect.

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Re the extra power in a TDI 'auto'. I persoanly suspect that the electronic control allows a more complex fuel map while still complying with the emissions regs. A mechanical injection pump can only have a simple fuel map by comparision, i.e. a certain rate of fuel increase per rev , etc. When this comes up from time to time I always end up wondering why electronic fuel pumps for TDI's are not sought after items as they will allow more flexibility for tuning as well I suspect.

+1 to all of this.

A mechanical pump can not do much with it's fuel mapping and only make simple adjustments. Anything ECU controlled will be more dynamic. So I suspect it was easier to map the auto Tdi's to make a little more power (to gain performance as they are massively sluggish) but retain very similar emissions to the manual.

I can see the appeal of EDC units. Even more so as you can get them to produce more power easily these days (harder in times past). But I guess most people don't really care about emissions when modding. So it's not really needed. Although mpg might end up being better with one.

@Troll Hunter

Torque converters can act as torque multipliers. Essentially allowing the engine to spin at a higher rpm than the output shaft of the torque converter. This means you can get more Horse Power at the wheels for a given rpm. Although torque converters aren't as efficient, so the trade off isn't quite as clear cut vs a manual.

Drag racers use this effect very well, they might have a torque converter that allows them to rev the engine to 3500rpm while remaining stationary. This means when they leave the line, the engine will be at 3500rpm instead of tickover. So more power at the wheels. If that makes sense.

You can feel this sensation in an automatic car when you pull away, the first moment of movement is often quite sharp and the car can easily lurch forward. You can feel it when the transmission up shifts too. Just after the new gear is selected. It's only brief as standard torque convertors don't have a very high stall speed.

Engine power however from car makers is always rated at the crank/flywheel. So there will not be a torque convertor to contend with.

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The auto version of the tdi has a higher turbo pressure.

Daan

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Seen this topic and read it through with some interest.

Last June I manged to get a 300tdi conversion on my 86 110 CSW keeping the LT77 and 1:6 transfer box (at least that's what the sticker said) and running 265/75/16 tires. When on dual carriage ways or motor ways the engine feels it could be doing with a 6th gear or overdrive reving possibly a bit higher. Could this have any adverse effect on the engine or running gear ? Iv'e had it on the speedo at 75/80 not for long though. In town or B roads she is quite happy pulling 5th at low revs.

My question is would I notice a big difference if I went to a 1:4 transfer box, it's a suggestion that some of my mates have made and I know where I can buy one. The fuel consumption does not seem too bad and a vast improvement from the old 2.5na.

Could someone throw me out some figures if it's not too much trouble.

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I do know that a 300Tdi with EDC set up properly runs very well - much better than a standard manual 300Tdi.

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Seen this topic and read it through with some interest.

Last June I manged to get a 300tdi conversion on my 86 110 CSW keeping the LT77 and 1:6 transfer box (at least that's what the sticker said) and running 265/75/16 tires. When on dual carriage ways or motor ways the engine feels it could be doing with a 6th gear or overdrive reving possibly a bit higher. Could this have any adverse effect on the engine or running gear ? Iv'e had it on the speedo at 75/80 not for long though. In town or B roads she is quite happy pulling 5th at low revs.

My question is would I notice a big difference if I went to a 1:4 transfer box, it's a suggestion that some of my mates have made and I know where I can buy one. The fuel consumption does not seem too bad and a vast improvement from the old 2.5na.

Could someone throw me out some figures if it's not too much trouble.

My brother runs a similar setup in his 90. High speed cruising is not so advised as you will be running the engine at high rpm for long periods. However short bursts will be no problem. 60-65mph is more the cruising speed. 65mph being the higher. I'll check rpms for you later on.

The 1.6 will make it very peppy. And very tractable in all gears. And be good for towing, hence why the Army used the 1.6:1 transfer box.

A 1.4 will give it longer legs and it'll be perfectly good for all things. But you will feel like it's lost it's peppyness by comparison.

If you want a stop gap between a 1.4 or an over drive, try some 255/85R16 tyres.

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The army mainly used the 1.6 to make up for the asthmatic 2.5 NAD!

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My 300tdi 90 has 1.2 transfer case (fitted by a previous owner). I have owned hte vehicle for 13 years and got used to it but I cannot say that I like it. The gearing is a bit too tall. It's fine when I travel overland but I find that it won't hold 5th gear for long on even the slightest incline. The biggest gripe I have is that I cannot fit larger tyres and am stuck to 265/75 (31") while everyone else is fitting the beautiful 285/75 (33"). What baffles me is the fact that I think a defender running on a 1.4:1 transfer case but with 35" tyres should have more or less the same final ratio as the 1.2:1 but fitted with 33", yet all my friends who have 35" tyres never complained that the gearing is too tall.

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My 300tdi 90 has 1.2 transfer case (fitted by a previous owner). I have owned hte vehicle for 13 years and got used to it but I cannot say that I like it. The gearing is a bit too tall. It's fine when I travel overland but I find that it won't hold 5th gear for long on even the slightest incline. The biggest gripe I have is that I cannot fit larger tyres and am stuck to 265/75 (31") while everyone else is fitting the beautiful 285/75 (33"). What baffles me is the fact that I think a defender running on a 1.4:1 transfer case but with 35" tyres should have more or less the same final ratio as the 1.2:1 but fitted with 33", yet all my friends who have 35" tyres never complained that the gearing is too tall.

I think some people just don't understand gearing and therefore don't notice it. Like the number of people that fit bigger tyres and then a lower ratio transferbox..... forgetting that it doesn't drop the low range back down.

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It's also possible your 300TDI just isn't running properly, or your friends vehicles are tweaked, which means no down-change for hills.

I know a V8 will pull a 1.2 on those tyres no problem ;)

Changing a transfer box is not a really big job, if it hurts you that much and want 33s then go and do it! Props off, hand brake off, support gearbox, undo transfer box mounts, and unbolt from gearbox, slide off. Refit is the opposite. Can EASILY be done in a day, even on a driveway.

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My 300tdi 90 has 1.2 transfer case (fitted by a previous owner). I have owned hte vehicle for 13 years and got used to it but I cannot say that I like it. The gearing is a bit too tall. It's fine when I travel overland but I find that it won't hold 5th gear for long on even the slightest incline. The biggest gripe I have is that I cannot fit larger tyres and am stuck to 265/75 (31") while everyone else is fitting the beautiful 285/75 (33"). What baffles me is the fact that I think a defender running on a 1.4:1 transfer case but with 35" tyres should have more or less the same final ratio as the 1.2:1 but fitted with 33", yet all my friends who have 35" tyres never complained that the gearing is too tall.

There could be several things going on here.

1. They just are noticing it, or don't want to say they are.

2. Engine specs might be different. And not all Tdi's are equal. You get some that run very well and some that don't. And the ones that don't will never make the same power, no matter what you do to them.

3. Most 35" tyres we get in the UK are actually more like 33" or just under if you measure them.

4. 5th gear ratio has changed over the years, so may have some impact.

5. All up weight and gear, if you have a roof rack, water tank and loads of other stuff, it'll impact performance and aerodynamics.

6. Are you sure they are all running stock diffs?

7. Why do you think you need 35" or 285/75 tyres anyway?

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By way of comparison for those who have inherited higher ratio set ups and are not familiar with standard set ups, I have an untweaked 200tdi running a 1.4 transfer box and on 31" 235.85r16 tyres. I have never had to change down on even the steepest motorway hills. It happily cruises at 65mph and has plenty spare at that speed to overtake if I need to.

I do think that Land Rover knew what they were doing when they calculated the original gear ratios.

HTH

Mo

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Thanks Chicken Drumstick.

It's exactly as you say very peppy and I have got very used to it, I wouldn't dream of thrashing the 300tdi (it needs to do me along time) usually 50/55 does me and now I know I can overtake a tractor if I come up on one.

Great info on the tires helping gearing, I like a wide and tall tyre as I do a bit of offroading correct me if i'm wrong would a 285/85/16 give similar gearing as your 255/85/16 suggestion?

Get the hammer the " piggy bank needs opened".

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It's also possible your 300TDI just isn't running properly, or your friends vehicles are tweaked, which means no down-change for hills.

I know a V8 will pull a 1.2 on those tyres no problem ;)

Changing a transfer box is not a really big job, if it hurts you that much and want 33s then go and do it! Props off, hand brake off, support gearbox, undo transfer box mounts, and unbolt from gearbox, slide off. Refit is the opposite. Can EASILY be done in a day, even on a driveway.

I know it's not a big job. I just cannot justify the cost. The Landy is getting long in the tooth and will get replaced sooner rather than later so I just don't want to throw any more money at it.

7. Why do you think you need 35" or 285/75 tyres anyway?

Because they look absolutely gorgeous :)

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By way of comparison for those who have inherited higher ratio set ups and are not familiar with standard set ups, I have an untweaked 200tdi running a 1.4 transfer box and on 31" 235.85r16 tyres. I have never had to change down on even the steepest motorway hills. It happily cruises at 65mph and has plenty spare at that speed to overtake if I need to.

I do think that Land Rover knew what they were doing when they calculated the original gear ratios.

HTH

Mo

I agree Mo.I'd also say that on my old 255/85R16 the ratios were pretty nice too.

I think LR got it right with the standard ratios and why I've got my gearing as close as possible to it. 37" rubber, 1.2 transferbox and 4.75 diffs. Couple that with the 5 speed auto having almost identical ratios to my old LT77. :)

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I'd echo Mo here - my Disco is untweaked apart from head work (which according to one of the engineering genii on here doesn't make any difference to a Tdi)

I run almost 31" tyres and a 1.22 box. I don't change down for hills and on a private road she will happily cruise at over the legal limit. She will also tow all up weight without any issue

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There could be several things going on here.

1. They just are noticing it, or don't want to say they are.

2. Engine specs might be different. And not all Tdi's are equal. You get some that run very well and some that don't. And the ones that don't will never make the same power, no matter what you do to them.

3. Most 35" tyres we get in the UK are actually more like 33" or just under if you measure them.

4. 5th gear ratio has changed over the years, so may have some impact.

5. All up weight and gear, if you have a roof rack, water tank and loads of other stuff, it'll impact performance and aerodynamics.

6. Are you sure they are all running stock diffs?

7. Why do you think you need 35" or 285/75 tyres anyway?

All valid points except number 2 - while you're quite right in saying not all engines of any given type are equal, as long as you identify the cause or causes for an under performing engine, you will be able to rectify it; they're not organic and they're not mystical. Tdi's are particularly simple - as long as the compression is OK, then any issues can only be down to timing, turbo or fuel delivery, all of which can be tightly scrutinised.

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