GolfGTIforum.co.uk
Model specific boards => Golf mk3 => Topic started by: bentert on 09 March 2009, 19:11
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Right, have been looking at getting a decat pipe for my mk3 16v.
What are the benefits of doing this?
What the are cons of doing this!?
Is it worth it, any increase in power??
Advice most appreicated.
Tony
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benefits: i heard about 5-10hp increase, more power through the rev range, more sound.
cons: will fail MOT, either you know the MOT inspector or chage it over for the cat for MOT time.
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more like 3-6 bhp tbh :undecided:
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Will gain you 3 to 5 bhp and you will need to refit the cat for the mot.
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yep 3-6bhp and mot failure..... oh and it will also change the power band slightly, so you'll need to rev that bit higher for peak power (same as different back box etc as you reduce back pressure)
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More hassle than its worth in other words!
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If you do it make sure decat pipe has fitting for lambda sensor!
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Are the lambdas in the cat on 16v's then? Mine is in my downpipe, although it is only a 1.4..
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Mine is in the pipe bit of the cat, front end.
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Well you learn something new every day :grin:
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Sure do! I know because had to renew the CAT and it was an absolute beggar to get the sensor out of the old one! nearly gave up on it!
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perhaps because I undid the CAT first and consequently couldnt get any leverage on the nut!
So meant I had to re-bolt up the CAT before I could undo the sensor!
Things like that stick in the mind! :angry:
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i fitted a de-cat to my 8 valve last year. seems to be a little more responsive and has a slightly deeper note to it! perhaps thats why i think its got more grunt! haha
lambda probe was pretty straight forward to remove but think it had been changed at some point! is alot easier to undo with the cat fitted.
had mot a month ago and flew straight through. either the guy was useless at MOTs or the fact i bought him a coffee and had a chat with him before telling him how many people had given his garage rave reviews and he was ace blah blah blah, sucking up in other words!
question tho? - do they fail a car without a cat because it wont pass the emissions? or do they just have a look and if it hasnt got one then fail?
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If the car should have a CAT as standard fitting then its an automatic fail without one!
You were lucky!
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If the car should have a CAT as standard fitting then its an automatic fail without one!
You were lucky!
i know it is a fail, but does it show up because the emissions will be higher or doesnt the CAT make any difference to the emissions?
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It should be very obvious to a trained mechanic (MOT Tester) that the CAT is missing!
They should do a very thorough check under the car!
Nothing at all to do with the emissions!
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If the car passes the emissions test without the cat fitted that is ok. It is only a fail if it fails the emmissions test. Emmissions tests after 1994 (I think) are based on cars with cats fitted as standard and are therefore much lower, so pretty near impossible to pass without the cat fitted.
The 16v cat doesnt look to be very restrictive, I have a de-cat fitted to my 16v and it does appear to make a differance to the pick up, and seems to rev a bit freer throughout the range.
Ess Three who posts on here did a comparison on the rolling road with his and didn't find a great deal of differance. He also did dyno tests on standard and after market exhausts like miltek with combinations of cat, de-cat, and race cell cat and he didn't find a great deal of differance in any of it, I seem to remember 2-3 hp max.
If you want to fit a decat the cheapest I found was the raceland one from Hottuning on ebay (put in a low offer), this comes with the lambda sensor hole. Or get a cheap secondhand cat and rod the core out of it. Having a second lambda sensor makes the swap easier at mot time if you can leave it in the cat / decat and just unplug it at the wiring end.
Paul
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It should be very obvious to a trained mechanic (MOT Tester) that the CAT is missing!
They should do a very thorough check under the car!
Nothing at all to do with the emissions!
Seems to be a dodgy area.
Spoke to a mate who does mots tonight. He says some mot testers will fail you for not having a cat fitted, but the guidelines say the exhaust system needs to be "in good condition" only, and passing the emissions test is a case of pass or fail. So as long as the exhaust is ok condition wise and the car passes the emissions test there is nothing specific in the guidelines to fail you on.
I know when I spoke to my mot place all he said was my car wouldn't pass the emissions test without the cat, so back on it went.
Paul
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Sounds like a collasal ball ache, I think I will invest my money somewhere better then.
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I have had problems in the past with other cars and I was told if its a standard fitting on the car it MUST be there and in working order!
I had a fail on my old Pug 405 because the abs wasnt working! Now that doesnt get activated during the MOT brake test so why should it be a fail? Because it was a standard fitting on that car and wasnt working!
Same principle applies here with CAT!
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I have had problems in the past with other cars and I was told if its a standard fitting on the car it MUST be there and in working order!
I had a fail on my old Pug 405 because the abs wasnt working! Now that doesnt get activated during the MOT brake test so why should it be a fail? Because it was a standard fitting on that car and wasnt working!
Same principle applies here with CAT!
Its ridiculous how the rules change from one MOT station to another. Obviously depends on how they interpret their rules and guidelines.
Air bags are standard fitment but they are not part of the MOT process so you will pass even with your airbag light lit.
My abs has never worked, and I don't want it to work, but it passes the MOT every year. I have removed the warning lights though so they don't know whether it works or not.
I wonder how many cars fail their mot for reasons that they shouldn't, a nice ruse by the garage to make some work for itself. (Cynical mode off now)
Paul
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The place I now use is where Billy's brother works. So get told the truth! :wink:
I mean they bend the rules a little as by rights with the blue lights I should have seperate reflectors!
So I guess it does come down to how a place interprets the rules.
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I have an email from another list which I belong to where a member has emailed both VOSA and the Dept Of Transport about CATS and MOT's and a brief summary of their answers are as follows.
1) MOT
There is no requirement for the cats to be present for the car to pass the MOT test.
If the car is on their database as being supplied new with cats then it will have to pass the emissions test under the (stricter) standards in place for a cat-equipped car.
As long as it passes the emissions test an MOT certificate can be issued.
2) Legality
There is no legal requirement for the car to have the cats fitted when it is used on public roads - even if it was supplied new with cats fitted.
As long as it has passed the MOT emissions test, and still passes the emissions test, it is not contravening any laws.
3) Insurance
(Caveat: Different insurance companies may take differing views on this. This is the government view)
The removal of the cats does not invalidate your insurance, unless it is considered as a notifiable modification or a notifiable "performance upgrade" and you have not notified them!
As long as you inform your insurance company/broker as to what changes have been made your insurance is valid.
If anyone wants a copy of the full email I can send it to them (too long to post on here)
Having said all that I doubt any Golf supplied new with a CAT will pass the stricter emmissions test without a CAT fitted.
Paul