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Hybrid_From_Hell

Land Rover Gearing Calculator - Free to LR4x4.com

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Hi All,

Much has been written around "Gearing" and the mixing of CW&P Ratios, Transfer Box Ratios, Gearbox Differences, and tyre sizes etc, but when I 1st did my 90 I used what little info I could find, bought and fitted a set of CW&Ps and found I hadn't got it quite right - an expensive error.

As such, and since then I as many know have started Megasquirt V8 Ltd, and since then have played around with my own programme, which I decided would be good to share with others, so that they can find a almost (hopefully) definitive central point to play about with all of the above, and compare what they could acheive with changes - and hopefully - unlike me - get the right changes 1st time around.

Since I wrote this program I have re entered all my info for the V8, and yes it came up with the RIGHT answer of what I have now, vs what my 1st best guess was,so I am fairly confident that the numbers when run work

So, what is this all about

1st a screen Shot :

post-22-0-32778100-1383826471_thumb.jpg


Print this off, and then follow the instructions below as to how it works.

The file attached to the end of this Thread is the actual programme itself, you may need Excel 2003 for it to run, unsure if it will work correctly in older versions, perhaps someone can try and see and advise !

One thing I found was the amount of hunting around I had to do when I did this moons ago manually, so the 2nd half of the program has a listing of :

  • All the Various Transfer Box Ratios, and what Land Rovers they are fitted to - either identify what you have or look at effect options have
  • All the Various CW&Ps combinations avaiable to chose from, and who makes / sells them
  • All the various Gearboxes and Variants, and what they are fitted into
  • A Tyre Size convertor, either add in the size via 265 85 16 or as a overall Height say 35 inches etc, the calculator then converts this to the Circumference and self populates under the box on the top in RED re tyre size

The program runs automatically, .....as you enter data it does the calculations accordingly

The fist step is to compare what you have NOW with a "Factory fresh Unmodified Land Rover"....


You need to enter a range of information as follows in the boxes under the RED Bands - 1 x at the top and tyre size at the bottom

  • Identify the Engine you have and add in either the MAXIMUM RPM (ie flat out) or maybe a chosen RPM this then changes the bottom RPM Line
  • Enter the Transfer Box Ratio
  • Enter the Gearbox Ratios for your gearbox 1st 2nd 3rd 4th and 5th if it has one
  • Check the CW&P is set to 3.54 and if not change it ....as this is the Standard factory unit Ratio
  • Enter the Standard Tyre size.

The program will then produce a set of results for both High & Low Range and speed per gear in 1000 RPM increments Per Gear and also the speed flat out or at your chosen RPM. Note that if you change the transfer Box ratios then this ONLY effects the High Gear speed, Low box IS THE SAME ON ALL Tboxes at 3.321:1.

Print this off and put to one side...

Now, using the same sheet where you left off change the item or items on your truck which now have been modified and are not as factory standard, most likley this will be tyre size, maybe transfer box ratio etc etc, when you have finished the changes are automatically calculated.

Now print off this sheet.

To see what is going on start by comparing the Factory "Top Speed" with your top speed......the likleyhood is you are "Over geared"

1st lets look at "Undergeared" not often the case, BUT, if you go too far with changes you go from too leggy in every gear to being undergeared, 0-60is "Impressive", er but again in real terms you find the engine is screaming its naggers off, and you only doing 40 !.....

Over gearing is where your Top Speed is' vast', mine as a V8 90 with a LT85 and having a 90 V8 Tbox my top speed was a stunning !!...202 MPH :rofl:
In reality it was so over geared that 5th was usless 4th not much better and it was like a dead dog on a stick performance wise... factory top speed was around 90 mph !! 'technically' but that doesn't really account for wind resistance which is around 0.7 and also power wise power required rises as the cube of speed.
ie a 10% increase in road speed say 90 up to 99 mph will require 33% extra power, so in reality it may never absolutely get there !
By keeping everything the same, but upping the CW&Ps to 4.75s even with 35" tyres the top speed was then pulled down to 98 MPH

Now, interestingly this is still a tad "Overgeared" not because its 8 mph over, but more however think of this.....

You have your car, its nice and drives fine, - now put 5 people in it and a bootfull of luggage, its "Not quite the same" is it ?

Actaully this is what we do with Land Rovers, cages, spares, lights, sill bars, roof racks, heavier tyres, heavier diffs recovery equipement etc etc so I would advise that you aim for say between 5-10% Top speed below Target vs Factory standard, and towards the higher end percentage the heavier your truckin essence mine is +10% over standard at the top end, but I do have 342 BHP....but...I have seriously considered lowering gearing a bit more yet :D

Lastly, Gearing is Exponential in is effects. Lets say your gearing is high by 20%. At at 10 MPH your only doing 12 MPH, .....and at 30 MPH 20% your doing 36 MPH...
....but say 70 MPH and your trying to do 84 MPH, ie the more the revs the WORSE it feels......hence why you need to look at target cruising speeds and weight of your truck etc !!

So, here you all are - here's the program, I will be adding features to this later - Acceleration Graphs- with deafult standard factory settings already in there, and other thoughts of ideas, but better you all have this in the meantime, as an Admin I will just update the download file and post a replay on the thread of the additional features

There are some fearsome formulas and working in here - I am 99% sure the numbers are correct, but if in doubt just PM me and I'll do a double check !..... :ph34r:

:D

Enjoy, and hope this is of use to many future 'Gearers' :lol:

Megasquirt gear calculator nov 2013 v12.xls

Nige

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Update No 1

I have been chart tinkering

This is a Hypothetical Graph of "A Factory land Rover" and then overlaid on top of the factory Acel Curve is a pictorial line of what this land Rover is Actually doing speed / RPM wise vs factory, and shows the 5 gears, Speed - ie what it IS trying to do vs what it is actually doing

My thoughts are to pick a range of Factory land Rovers, ir say RR Classic 200/300/V8 Disco 200/300/V8 90 110 etc etc have a tab at the base that you click on for your "Standard Truck" and then once you have entered YOUR trucks data the graph will show YOUR factory model vs what you have now, both Low box and High box, as you make changes to the main screen inputs ie CWP tyres Tbox etc etc the graph updates automatically showing if its closer too far / not enough...

Here is a test graph showing the above JUST for High Box and also its just Hypothetical figures, but in this example it nicely shows that what it is TRYING to do speed wise in 3rd gear, it SHOULD be doing it in 4th gear !!

Wondering if this would be a usefull adition ?

Thoughts ?

post-22-0-98567500-1383906748_thumb.jpg

Nige

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Nige, first of all, thanks for posting this up and make the information available to the members of LR4x4. This is still the most informative forum I have come accross for landrover related tech.

One addition I can think of is the speedo correction; which gear do you need in the speedo drive to make your speedo read the right thing. I have been trawling the internet for this, and tried to order the 'correct' gear, but I do remember it being guesswork, and ultimately, they were on back order from the stealers, and I couldn't work out which car have which gear. I then went to the 'you know what' test, hoping that it wasn't testable. As my car was full time 4wd, it wasn't, but it still needs looking at.

Daan

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Update No 1

I have been chart tinkering

This is a Hypothetical Graph of "A Factory land Rover" and then overlaid on top of the factory Acel Curve is a pictorial line of what this land Rover is Actually doing speed / RPM wise vs factory, and shows the 5 gears, Speed - ie what it IS trying to do vs what it is actually doing

My thoughts are to pick a range of Factory land Rovers, ir say RR Classic 200/300/V8 Disco 200/300/V8 90 110 etc etc have a tab at the base that you click on for your "Standard Truck" and then once you have entered YOUR trucks data the graph will show YOUR factory model vs what you have now, both Low box and High box, as you make changes to the main screen inputs ie CWP tyres Tbox etc etc the graph updates automatically showing if its closer too far / not enough...

Here is a test graph showing the above JUST for High Box and also its just Hypothetical figures, but in this example it nicely shows that what it is TRYING to do speed wise in 3rd gear, it SHOULD be doing it in 4th gear !!

Wondering if this would be a usefull adition ?

Thoughts ?

attachicon.gifTest Graph V4 High range Factory vs a Overgearing test sample.JPG

Nige

If i am on the same wavelength as you Nige, i think it will.

Are you suggesting that tab at the bottom show the factory 90 v8 Defender , for example

Another for the 200tdi Defender etc.

and the one that is your current setup?

I think it is a good idea, as i no idea what mine was standard

Many other folk may not either

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Now if only I could get my 300 TDi to rev out to 7000 rpm :blink: (198 mph in a 110 would be fun)

You need TSD's coefficient of drag spreadsheet for that, I can't remember the numbers but I don't think even a 7000rpm TDi would pull it very far past 100.

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Apologies for dragging this back up, but just spotted a couple of typos.... 'Rim Hieght' and 'Overall Hieght -inches'

And the humongous number of decimal places in the tyre height and wheel circumference :P

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Ross, you are not-picking. This is nothing compared to some of Nige's posts :P

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TBF it has all the right letters just not in the right place, some of Niges red wine fueled iphone posts require a degree in cryptography to decipher ;)

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It's not Michael.... I'm only starting him off gently into the world of typing English rather than iNglish :P

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Just to confirm please before i think of going to the sweet shop

After it has re-opened for the holidays :hysterical:

Does this look/sound right

And according to the chart i need 4.75 R&P gear

4.6 v8

LT85

1.2 LT230

37'' Dia tyres (measured)

Thanks John

Megasquirt gear calculator nov 2013 v12 (2).xls

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^^

:rofl:

Yes, it sure does look right, its the 37"s which mean the need for 4.75s, you might even consider 1.4 TBOX as well !!

Nige

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Yes, it sure does look right, its the 37"s which mean the need for 4.75s, you might even consider 1.4 TBOX as well !!

Cheers Nige

I do have a 1.4 tbox and a 1.6 ex military, but thought the 1.2 would be better for cruising.

(not that you can in a challenge truck)

I'll give the sweet shop a ring next week

Ta

John

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