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Question for the mappers, mapped for decats running cats


Arran

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Evening all

 

Basically I'm going to be travelling through various different countries in Europe next month and am thinking of putting my cats back in, incase we get pulled over.

 

Question is mine is mapped for decats so if I was to put them back on without readjusting the map how will the car run, maybe over fuel or run lean?

 

Anybody know

 

Cheers

 

Arran

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Don't think anything will happen as your car registered in UK and its only should meet UK standards(MOT)...if you were going to live abroad then may be yes, but just travelling I don't see any problems! I'm pretty sure, but might be wrong!

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Don't think anything will happen as your car registered in UK and its only should meet UK standards(MOT)...if you were going to live abroad then may be yes, but just travelling I don't see any problems! I'm pretty sure, but might be wrong!

 

and UK MOT regs say if the car came fitted with cats from the factory it still needs to have them.

 

fine to swap to race cats etc, but decats are no longer road legal.

 

the old test used to just have to pass on emmissions, so some test centres used to stick the probe in a car sat next to a vehicle with decats. and use that reading. but now its a visual inspection as well as emmissions.

 

not only that if your found to have decats they ask to see your MOT and trace the test centre as well. they are cracking down on it alot more. and if your loud you'll draw attention to it.

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Yea, I know that it is requirement in UK to have cats...I meant if he already has MOT certificate he would've been fine, as he can just wave mot paper in front of them lol ...but I did say I might be wrong, as after reading above I now know they can to check it visually! I got pulled over couple of times since I had decats, and police officer always mentioned that car is a bit loud and I always reply "well, it passed MOT so it's fine" and they agree! :)

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Having the car mapped to run with out CATS will make use of the extra flow you get from the free flowing exhaust.

 

Thus, getting the exhuast gases out quicker.

 

If you can get the gases out quicker, you can more fule/air in quicker and make more power.

 

Very basic way of describing it.

 

So, your map currently allows for a more freer flowing system, so it add's more fuel to the mix, increases the fueling.

 

Putting the CATS back in will reduce the flow, not by a great deal mind you and will reduce the power made at the higher end by a touch.

 

As someone else said, you will just run a little rich, which is much better than lean, so you have nothing to worry about really it just wont be making ideal power for teh mods you have mapped your engine too.

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Thats cool then, as long as its not detrimental to the cars health then for a week it will be fine. Contemplating just taking the cats with me and if i need to swap them over when im out there then i will

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Im not sure if turbo cars are different though

 

Hell yeah, turbo cars will feel it a lot more.

 

The turbo will be set up to run on a less restrictive exhaust system without CATs, so the turbo will spool a different way, normally quicker, putting CATs back in will change the way the gases exit and therefor the way the turbo spools.

 

The fueling will still be set to max but it won't be building up the PSI it's expecting so it will run worse.

 

Again that's a very general way of describing it and there are different turbo systems but that is the basic idea.

 

NA won't feel the drop in power as much :) .

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that's a fair point suits, like you said the ecu is expecting lots of air forced in by the turbo so gives loads of fuel so would run really rich until the turbo hits full boost

 

Yeah, I'm pretty sure that's the basic idea of Turbo's Chubb, I've got more first hand experience with NA engines though :) .

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A car with the cats removed will have more ignition added if the car has been mapped, refitting the cats will cause a restriction so it is possible young start to see detonation as the restriction will cause back pressure so slowing the flame path.

 

Going the other way is never an issue with ignition timing will normally cause a motor to run leaner but as these cars are NA they are normally pushed towards the leaner area without being dangerous.

Edited by Mark@Abbey m/s
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