What is the benefit of decat? - LotusTalk - The Lotus Cars Community

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post #1 of 40 (permalink) Old 02-08-2012, 08:21 AM Thread Starter
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What is the benefit of decat?

what is the benefit of decat the exige s240?
does the car get more hp, faster or just sound louder?
before decat,the car can feel the pull stronger and hit 220+km,after decat the car feel lighter, less pull but only do 200+km :-(....
should i just put back the catalytic....?????
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post #2 of 40 (permalink) Old 02-08-2012, 07:13 PM
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+: more power, lower heat retention, lighter weight

-: louder, emissions

when you removed the cat, the A/F ratio was changed causing you to lose power (most likely). It's possible it became more rich, happened when I installed mine. You need to tune for it, otherwise put the cat back on.

** save ~10 lbs gain 1 hp ** EQ: Y=(190*X) / (1984-X) where Y is (HP) and X is (lbs)

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post #3 of 40 (permalink) Old 02-08-2012, 07:20 PM
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It keeps your cat like new.

Last edited by Harix; 02-09-2012 at 12:51 PM.
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post #4 of 40 (permalink) Old 02-08-2012, 11:31 PM
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post #5 of 40 (permalink) Old 02-08-2012, 11:35 PM
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post #6 of 40 (permalink) Old 02-09-2012, 04:40 AM
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post #7 of 40 (permalink) Old 02-09-2012, 05:17 AM
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Its the same as dedog.

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post #8 of 40 (permalink) Old 02-09-2012, 12:19 PM
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Its the same as dedog.
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post #9 of 40 (permalink) Old 02-09-2012, 01:04 PM
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Quote:
Originally Posted by shay2nak View Post
+: more power, lower heat retention, lighter weight

-: louder, emissions

when you removed the cat, the A/F ratio was changed causing you to lose power (most likely). It's possible it became more rich, happened when I installed mine. You need to tune for it, otherwise put the cat back on.
+: louder
-: can smell sometimes

You won't blow out your cat packing with a decat

My tune also went rich
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post #10 of 40 (permalink) Old 05-09-2012, 05:44 PM Thread Starter
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+: louder
-: can smell sometimes

You won't blow out your cat packing with a decat

My tune also went rich
after one month i did the decat and now i put it back in.
it feel much more power and with better pull.
give higher top speed.....
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post #11 of 40 (permalink) Old 05-10-2012, 03:43 PM
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My thought behind decat was that the cup cars have it. Back then the dyno results I saw were about 10+HP peak. True, low end might have been lower due to decat.

My car is tracked often so for me it is worth eliminating the heat and it is common for the cats to crack as well.


Exige-S stock exhaust decat dyno runs


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post #12 of 40 (permalink) Old 05-10-2012, 04:33 PM
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decat also makes your car not street legal anymore (in CA at least)
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post #13 of 40 (permalink) Old 05-10-2012, 07:52 PM
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It makes it not street legal anywhere in the US, just some places don't check and don't care. Shay2nak was spot on in his assesment, I will add one caveat, all the things he says is true with the correct tune. With a bad tune, well, you may lose HP.

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post #14 of 40 (permalink) Old 05-10-2012, 10:08 PM
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Quote:
Originally Posted by EricH View Post
My thought behind decat was that the cup cars have it. Back then the dyno results I saw were about 10+HP peak. True, low end might have been lower due to decat.

My car is tracked often so for me it is worth eliminating the heat and it is common for the cats to crack as well.


Exige-S stock exhaust decat dyno runs
you gain about 10wtq downlow also.

** save ~10 lbs gain 1 hp ** EQ: Y=(190*X) / (1984-X) where Y is (HP) and X is (lbs)

'07 Lotus Exige S310


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post #15 of 40 (permalink) Old 05-11-2012, 12:25 AM
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When you remove your cat do you always put it back on for the MOT test?
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post #16 of 40 (permalink) Old 05-11-2012, 01:30 AM
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Yes if you want to pass. In California, a smog test pass is required after the first 5 years of a car's lifespan. It isn't comprehensive, so the car can be a piece of crap about to fall apart, with no hood or roof or doors, or even wheels for that matter and would still pass as long as its within established emissions standards (so long as you can get the car to the smog test shop).
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post #17 of 40 (permalink) Old 05-15-2012, 10:35 AM
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Originally Posted by addertooth View Post
It makes it not street legal anywhere in the US, just some places don't check and don't care.
Ditto. For those in the US, the US Clean Air Act was amended in 1990 to make it illegal for anyone to "remove, bypass, defeat, disconnect, damage or in any way render ineffective any emission control device or element of design that has been installed on any motor vehicle..." Individual owners are subject to a $2,500 fine, and any dealers or mechanics that do it for others are subject to a $25,000 fine. That amendment still stands, and there was a recent - within the last 2 or 3 years - crackdown on several auto tuning shops across the country that were doing that.

Of course, I live in Florida, where you could drive down the street in a home made smog machine and no one would bat an eyelid. But I would still be breaking the law if I disconnected any emission control piece that came with the car.
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post #18 of 40 (permalink) Old 05-15-2012, 06:11 PM
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Originally Posted by GronkDaSlayer View Post
decat also makes your car not street legal anymore (in CA at least)
The fines can be pretty high.
Is the 2500 Fed added to state fines?
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post #19 of 40 (permalink) Old 05-15-2012, 06:43 PM
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The sound is absolutely fanmotastic!

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post #20 of 40 (permalink) Old 10-31-2012, 03:05 AM
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Oh ok, in London where I live, most just remove the cat after the MOT has passed :P which I now know is an equivalent of a smog test in the USA. Do all states over there require a smog test? I heard there are different rules between each state?

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