Is my 200tdi really a 2.5N/A?

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Got mine from Silverline in Warwick West Mids, they delivered 6 wheels and tyres and a set of new wheel nuts to me in France for £1000,00. I know some people have slated them on here but they were good to me.
 
What you describe, going up in 4th with good power and then starting to loose speed once in 5th, that's exactly what was happening on my Disco...

never figured out why was doing it though....
Even changed the tyres (265/75 R16 special tracks) for the ones that came with my defender, dont know the size, but they were MOD tyres...

didnt make a difference.

Trying to sort that issue I changed:
Filters
lift pump
accelarator cable
all the intercooler hoses
airbox to turbo hose

Didnt make a difference at all
 
There's only a bit over 3% difference in circumference between 235/85/16 and 285/75/16

Stock tyres on a 90 were:
205/80/16, circumference of about 90.5 inches.
235/85/16 is 99.6 inches
275/75/16 is 101.28 inches
285/75/16 is 103.4 inches

Note: These are the calculated figures, not 'real world' ones as they'll depend on pressure and weight of vehicle, sidewall strength and tread depth. But they'll do as a rough guide to how much they'll affect your gearing.

From the ones I've seen the stock speedo of the 90 on standard wheels and tyres is way out, it over reads by about 10% - so going from a defender transfer box to a disco one (approx a 10% overall gearing increase) pretty much puts your speedo cock on.

Going from standard wheel and tyre combination to 235/85/16 adds about another 10%, going to 275/75/16 would add about 11.5% and going to 285/75/16 would add about 13.5% over stock.

If you look at the overall diameters it's even easier to see where the big difference is:

205/80/16 = 28.9" - call it 29".
235/85/16 = 31.73" - call it a little 32" or about 3" over stock.
275/75/16 = 32.24" - call it a large 32" or about 3" over stock.
285/75/16 = 32.83" - call it 33" or about 4" over stock.

A 20% increase in gearing is a chunk for a 2.5 Tdi to cope with - you can tweak the boost and fueling so it doesn't appear to make as much difference, but you're going to wear stuff out faster and if you drive it at 70 to 80 mph you'll be able to watch your fuel gauge move courtesy of the "pair of mating housebricks" aerodynamics!

With a defender tbox and 235/85/16 MTs, driven at a GPS corrected 55 to 60mph I've had close to 40mpg out of my mildy tweaked 200.

Driven flat out (indicated 85, gps corrected 83) in the same config I've had 18mpg and spinal surgery :D

If you do tweak the boost and fueling but drive it sensibly at lower (actual NOT indicated) speeds you won't use any additional fuel over the standard tune - if you have excess fuel a diesel, that's not running flat out, will burn it and you'll accelerate.
 
Adz said:
There's only a bit over 3% difference in circumference between 235/85/16 and 285/75/16

Stock tyres on a 90 were:
205/80/16, circumference of about 90.5 inches.
235/85/16 is 99.6 inches
275/75/16 is 101.28 inches
285/75/16 is 103.4 inches

Note: These are the calculated figures, not 'real world' ones as they'll depend on pressure and weight of vehicle, sidewall strength and tread depth. But they'll do as a rough guide to how much they'll affect your gearing.

From the ones I've seen the stock speedo of the 90 on standard wheels and tyres is way out, it over reads by about 10% - so going from a defender transfer box to a disco one (approx a 10% overall gearing increase) pretty much puts your speedo cock on.

Going from standard wheel and tyre combination to 235/85/16 adds about another 10%, going to 275/75/16 would add about 11.5% and going to 285/75/16 would add about 13.5% over stock.

If you look at the overall diameters it's even easier to see where the big difference is:

205/80/16 = 28.9" - call it 29".
235/85/16 = 31.73" - call it a little 32" or about 3" over stock.
275/75/16 = 32.24" - call it a large 32" or about 3" over stock.
285/75/16 = 32.83" - call it 33" or about 4" over stock.

A 20% increase in gearing is a chunk for a 2.5 Tdi to cope with - you can tweak the boost and fueling so it doesn't appear to make as much difference, but you're going to wear stuff out faster and if you drive it at 70 to 80 mph you'll be able to watch your fuel gauge move courtesy of the "pair of mating housebricks" aerodynamics!

With a defender tbox and 235/85/16 MTs, driven at a GPS corrected 55 to 60mph I've had close to 40mpg out of my mildy tweaked 200.

Driven flat out (indicated 85, gps corrected 83) in the same config I've had 18mpg and spinal surgery :D

If you do tweak the boost and fueling but drive it sensibly at lower (actual NOT indicated) speeds you won't use any additional fuel over the standard tune - if you have excess fuel a diesel, that's not running flat out, will burn it and you'll accelerate.
Click to expand...

Thats some very interesting info Adz, cheers mate as you say a 20% increase certainly is a lot.
 
Last edited:
Been a bugger of a day..i thought as suns shining i'll do a few bits....replace headlight bulbs to more powerful ones...first one works a treat...started removing passenger side...ITS A SEALED UNIT !!!!!!
 
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