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View Full Version : How much will decat wreck your mpg ?


skitts
5th October 2011, 11:01
I have recently replaced my manifold, so now it's decatted. My fuel gauge is broken so i can't tell how much fuel i have :(.
How many miles should i be getting from £20 at about 132 a litre ?

Gandi699
5th October 2011, 11:12
Depends how you drive it

skitts
5th October 2011, 11:14
hardly ever goes over 3k tbh

Gandi699
5th October 2011, 11:32
I'd estimate 30-35mpg if its in good health, maybe a bit more

Proffitt
5th October 2011, 11:32
With a decat, it'll sound different (nice) and you'll drive so you can hear it.

So it will reduce your MPG.

No one can give you an exact figure.

skitts
5th October 2011, 11:35
Well i suppose so tbh it would be better if my fuel gauge worked :/ I will have to get it sorted then it should be fine!

rick_VTR
5th October 2011, 11:50
I fill up when the fuel warning light comes on.
I drive a 2002 VTR.

Approx £52.
The garage i use is 134.9 a litre.

Before decatting i was doing approx 350 - 450 to a full tank depending how i drove.

I decated the other week and filled her up when the light came on, next time the light come on i had done 375 miles, and i had obviously tested how much difference the decat had made so i thought it would have sapped the fuel but stayed roughly the same tbh.

So your answer is you wont notice much/if any of a difference from decatting :y:

devilsadvocate
5th October 2011, 11:55
Depends on your driving style

It wont make much difference in my opinion.

Maybe a few mpg less than you got before.

Liam_
5th October 2011, 12:32
You shouldn't notice any difference in MPG imo.

skitts
5th October 2011, 12:35
Ok well thanks for the help

saxova
5th October 2011, 12:36
Did you put the right lamba sensor in the manifold? and sleeved the other one to read clean air?

I didn't and it's defiantly overfueling, so loss in MPG.

Stuart85VTR
5th October 2011, 12:37
I had mine decatted for a while and didn't notice a difference on mpg so you should be good to go :)

Saxotim
5th October 2011, 13:09
my mpg improved with decat......

LSOfreak
5th October 2011, 17:07
my mpg didnt change noticabley with a decat
no one can tell you mate, becuase we dont know how you drive, if you do town driving, motorways, back roads??

skitts
5th October 2011, 17:12
Mostly town driving. I followed the guide on here for the manifold fitting. I have put one in the manifold but one is just sitting in my engine bay. I have not sleeved it yet.

LSOfreak
5th October 2011, 18:47
I fill up when the fuel warning light comes on.
I drive a 2002 VTR.

Approx £52.
The garage i use is 134.9 a litre.

Before decatting i was doing approx 350 - 450 to a full tank depending how i drove.

I decated the other week and filled her up when the light came on, next time the light come on i had done 375 miles, and i had obviously tested how much difference the decat had made so i thought it would have sapped the fuel but stayed roughly the same tbh.

So your answer is you wont notice much/if any of a difference from decatting :y:

thats really good mpg

i struggle to get 250 miles out of a tank with mine aroiund town :(

rick_VTR
5th October 2011, 18:52
thats really good mpg

i struggle to get 250 miles out of a tank with mine aroiund town :(



i dont really do much town driving tbh.

i travel approx 50 miles home on a friday night, bit of town driving maybe a trip off somewhere on the weekend with the mrs.

then drive 50 miles back to the barracks on a sunday.

the car doesnt move much in the week unless i go into town for a takeaway or pick up stuff for the sax in the evenings.

for an engine thats done 114k miles i think its doing bloody well haha.
but then i do look after it, service regular etc so.

Slugshead
5th October 2011, 19:57
No difference in MPG

saxova
6th October 2011, 09:12
Just got 90 mile's from 10 litres of fuel in my de-catted R.. Actually drove sensibly for a full 10 litres lol.