 | Home > Maintenance & Modifications > Effect (if any) of de-cat on fuel consumption |
 
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| munch90 Member Since: 26 Oct 2013 Location: guildford Posts: 3558  
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if it goes better and you use the extra then maybe bit worse
if you drive the same as you do now , and it breathes a bit better then maybe a bit better personally I think your be hard pushed to notice much gain or loss I keep thinking about doing the same , but don't want any extra noise and be honest it does all I want it to with cat fitted |
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16th Jun 2015 4:42pm |
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| consumerize Member Since: 27 May 2014 Location: Berkshire Posts: 121  
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Mine is a TD5, but its still a diesel with a turbo, so the similarity is good enough for this hypothetical process...
Having re-mapped by those good guys at Alive made it far better to drive, faster to accelerate etc. No change in fuel economy. Removing the CAT, made it even better again. Turbo spins up quicker and acceleration again improved. almost as much again as the remap achieved id say. Once again, no change in fuel economy. This includes normal commute driving, and driving it like i stole it, which is done in equal measure.... It would of course fail the MOT if this was done, even at an imaginary MOT centre |
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16th Jun 2015 5:25pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17491 
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Gents, thank you. Your views echo the answer I would have given to the same question.
Here's the surprising thing that I can't really explain. I've owned my Defender since 2010 and do a fairly hefty mileage, typically 30k per year. My journeys are predictable and have been the same in this time, I fill up on the same fuel from the same garages, drive the same routes and speeds, with the same loads. Everything is consistent. I fill the tank to the second click every time, reset the trip when I fill, and I fill once the "low fuel" light comes on. For about 5 years the light has come on after 390 +/- 5 miles, without fail. Earlier this year I found that the flange had come off the cat/downpipe (as posted elsewhere on this forum) and being reluctant to blow a grand on a new one, I fitted - temporarily of course - an Alive decat pipe. Nothing else has changed. Now I am consistently getting 430 +/- miles before the light comes on! I can't explain it! It is an improvement of around 8%, and it doesn't seem possible that just decatting has had this effect! |
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16th Jun 2015 6:20pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8108  
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i tried a straight through pipe to replace the CAT and my immediate thought was it went better, puesdo effect i presumed. i am now 8mths in of use and when doing the normal routine dirving with no other changes to the vehicle mpg has improved alot. i had also put this down to being run in better? 52k on a 10MY 2.4 Cheers
James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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16th Jun 2015 6:53pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17491
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The engine definitely seems to run more freely, but I am astounded at the apparent improvement in fuel usage.
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16th Jun 2015 7:14pm |
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| mk1collector Member Since: 17 Sep 2009 Location: West Yorkshire Posts: 6769 
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The cat could have been clogged up maybe? Ray
My build thread http://www.defender2.net/forum/topic17615.html |
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16th Jun 2015 7:44pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17491
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Well it doesn't appear to be clogged (given that you can clearly see the matrix on a 2.4 cat) and my average mpg for the 150k miles up to removal was 28, which isn't bad for a 110 running at approx 2.5 tonnes, with a roofrack and 285 mud t/a BFGs.
Perhaps I've been "Caterhamed" and 500 from a tank is possible! Whatever the cause, I like it. 
Incidentally you can pass an MOT with no cat if the tester doesn't notice! 
(Hypothetically speaking, of course)! |
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16th Jun 2015 9:27pm |
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| Caterham Member Since: 06 Nov 2008 Location: Birmingham Posts: 6312 
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 - caterhamed!
good to hear the removal of an environmental addition it better for the environment 
....what do they say...if it ain't broke don't fix it  |
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16th Jun 2015 9:46pm |
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| Lorryman100 Member Since: 01 Oct 2010 Location: Here Posts: 2686 |
Don't know if this will help BW, but with the Alive stage 2 remap and decat pipe I fill up at a quarter tank with about 320 miles on the trip meter. Last time I worked it out it was giving a return of 28mpg, then again I tank the arse of mine more times than I doddle so I am probably of no help, sorry.
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16th Jun 2015 10:42pm |
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| munch90 Member Since: 26 Oct 2013 Location: guildford Posts: 3558
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do you notice any more noise while driving ? ( with de cat fitted ) |
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17th Jun 2015 6:01am |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610 
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Munch,
Yes but only at a certain throttle position and when the engine is under load....like a slight 'growl' not unpleasant or annoying. If you go through life with your head in the sand....all people will see is an ar5e!! Treat every day as if it is your last....one day you will be right!! |
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17th Jun 2015 8:23am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17491
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I am not really aware of any additional noise, but since I run mud tyres (which buzz nicely now they're a bit worn) I probably wouldn't notice anyway.
There is no doubt however that the engine runs better without the cat, it revs much more freely and is more responsive, and the turbo spools up quicker. I have been surprised at just how much difference it makes. There is also a very noticeable reduction in underbonnet temperaturs, and a noticeable reduction in cabin/footwell temps on the offside of the vehicle. Overall it is a great improvement in almost every respect. From a design point of view I have always felt that the engine suffered due to the cat being so close to the turbo. It is inevitable that the cat will restrict exhaust gas flow to some extent, and the closer that it is to the turbo the more noticeable will be the effect on the turbo. I wonder if there'd be any noticeable perfomance inprovement if a standard cat was moved further along the exhaust. In theory most of the benefits of a decat could be achieved with a free-flow cat mounted somewhere under the vehicle. |
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17th Jun 2015 9:53am |
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| Hufflepuff Member Since: 25 Oct 2014 Location: Hampshire Posts: 727 
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Does anyone know if there is a high-flow performance cat available for the Td5? They are fairly common for petrol cars, and are basically a lower cell count to allow the gas to move through more easily. I can't find anyone selling them for the Td5 (or any diesel for that matter).
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17th Jun 2015 12:39pm |
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| Supacat Member Since: 16 Oct 2012 Location: West Yorkshire Posts: 11018 
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Any changes to tyres over the extended period, and i wonder if tyre wear could account for some of the change?
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17th Jun 2015 1:37pm |
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