Decat Exhaust?

[bigsteve200]

hi all

anybody on here got a decat? i have a stainless custom catback system and im very tempted to get a decat made and fitted by thesame company (exhaust uk sheffield) they have said they can make one no probs for a great price but it will throw up a warning on the dash which kind of new would happen from previous cars ive decatted, anyone got a decat on there IS200 and what differences has it made?

cheers

[noby76]

Hi bigsteve dont mean to bash IS200 but all IS's do come with a good tuned exhast system and by fitting a new exhaust and decating will not free a lot if any more horses out of the 200 as enough has already been squeezed out of it from factory. best solution for power increase is to either go forced air induction i.e Turbo or Supercharge the engine or the easy and simplest option is get you an IS300 and forget what people say about it being automatic they are a BLAST to drive . use to modify my previuse cars in the past but always wanted more after every bit added to it b but realised either going forced air or getting a bigger capacity solved this and as they always say "its easier to make more power from a bigger lump than a smaller one"

[steve2006]

Will decatting make a lot of difference to performance?

One thing to remember is that even if emissions are within specifications the car will now fail an MOT with no cat fitted when it should have one as OE which means refitting it for every MOT.

You are already aware of the EML coming on if it is removed again another MOT fail now.

[noby76]

as steve2006 pointed this will be quite a hassle every year jut to pass MOT then decat again then fit a cat again when it's due! IS300's are going for reasonable prices both on eBay and autorader! 210bhp with with almost 300NM of torque which comes to the back wheels early in rpm aswell...

[TigerFish]

No idea what a decat will do on the IS power wise, on my VW Corrado VR6, it frees up another 10bhp or there abouts so I'm told. I've never bothered to fit the decat myself (although I have one), but not that big a deal to swap around for the MOT. There are ways of fooling the O2 sensor at the cat and keep the EML out, a resistor to fake a good reading is one of them iirc.

[bigsteve200]

cheers guys. ive had a few decats fitted so i can live with warning lights on and also have to recat for mot, i gained about 14bhp out f decatting my Seat Leon Cupra but that was a turbo engine that was heavily modified, i love my IS200 so not looking to sell it, looked into forced induction but not had much joy with turbo/charged cars in the past, my car is more of looker just for cuising about in but i thought for £100 for a decat if it frees up 5 bhp plus id be happy, probably just leave it now,

thanks

[noby76]

If that will make you happy I’ll say go for it mate, all I was pointing out was you will not gain 20-50 bhp by having a decat maybe 5-10 bhp could be achieved. But for more power a turbo or bigger cubic capacity will be a way forward.

[north]

Get yourself a proper exhaust manifold... the OEM version has a pre-cat. And if you can get a company to make you a sports-cat you'll be fine ( 200 cells version will be the one you want) this should free up some BHP my estimate is something in the region of 10 to 15

[jeffrosie]

Something like this

http://www.ebay.co.uk/itm/LEXUS-IS200-1G-FE-2-0-98-05-EXHAUST-DECAT-MANIFOLD-MF6547-/110814501437?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item19cd0f1a3d

joined to

http://www.ebay.co.uk/itm/LEXUS-IS200-STAINELESS-STEEL-EXHAUST-DECAT-CAT-DOWNPIPE-DP7935-/200718980598?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2ebbc895f6

and ending in

http://www.ebay.co.uk/itm/LEXUS-IS200-CAT-BACK-EXHAUST-SYSTEM-STAINLESS-STEEL-2-0-1998-2005-XE10-/140685015392?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item20c17af960

I have the the centre decat and the system. It makes a huge difference to the way the engine feels and the way the car accelerates. Makes the engine come a live and it feels freer and livlier at higher RPM's. Lower rev range is improved no end too.

[bigsteve200]

Something like this

http://www.ebay.co.u...=item19cd0f1a3d

joined to

http://www.ebay.co.u...=item2ebbc895f6

and ending in

http://www.ebay.co.u...=item20c17af960

I have the the centre decat and the system. It makes a huge difference to the way the engine feels and the way the car accelerates. Makes the engine come a live and it feels freer and livlier at higher RPM's. Lower rev range is improved no end too.

hows fuel consumption with the full system including de-cat? also has it caused the warning light to come on the dash?

[noby76]

cant have a bit more power without sacrifising fuel mate. my guess will be you might loose maybe 2-3 miles to every gallon. but will also depend on your right foot..

[jeffrosie]

To be honest, not noticed any difference. Engine feels more torquey from lower revs, so need less right pedal for same engine responce ;)

Also as all sensors are fitted into system, no flashing lights on the dash.

But its a lil bit loud for a 'luxery car' but not too intrusive if you know what I mean.

[fil4362]

eml being on for an mot test isnt a fail. A missing cat is. should the tester spot it

[mack5029]

the mot tester cant take anything apart on the car and you cant see the guts of a cat from the out side. i hav heard of people taking the cat apart and removing the internals putting back together and it working fine

[fil4362]

the mot tester cant take anything apart on the car and you cant see the guts of a cat from the out side. i hav heard of people taking the cat apart and removing the internals putting back together and it working fine

Correct. This does happen. A weld on a cat doesnt mean its been hollowed out. The only problem with this is, if the car fails the emmisions test you can only remove the cat cut it open again cross your fingers that when you put the internals back in and weld it back up that it all works.

[fjcfarrar]

If the decat could provide 10 - 15 BHP more you would scarcely notice it anyway; but it will not and could even reduce power slightly. It will make the car a bit louder so provide a couple of completely imaginary extra BHP.

The only route to extra power on the IS200 is by forced induction ie a charger. Nothing you do to inlet-pipes, filters or exhaust-sytems will make the slightest difference because the OEM items can already provide more than enough gas-flow anyway. A better solution is the IS300 which is also better equipped - even though it is Auto only.

Later this year or early next year warning lights that do not come on during the start-up sequence or remain permanently lit are set to become MOT failures as in most of the EU, but testers are hard-pressed by all the many regulatory requirements so perhaps may not notice.

[north]

I do not agree with the above statement of not making a difference as I had mine with it and went original... The diference is there, You have to get the car up to 3000 rpm to start pulling properly as before that it would start pulling at 2500 rpm that makes a huge difference it might be around 5nm torque difference which you'd expect to feel in the mid range... but you feel it way earlier (doing the math this equates to around 7 to 10BHP depending on the state of the engine) also the OEM exhaust manifold has a pre-cat. And a cat is nothing more than a filter slowing down the exhaust gasses.

To make a long story short... IF someone changed the complete exhaust from the manifold al the way to the back-box one might have a power gain of about 5NM without a remap. Do a remap and you'll find the car running smoother and faster maybe with a little more gain might be 9NM or more.

[mikey's IS]

Not in the IS fjcfarrrar speaks the truth.

A free flowing exhaust is only good for forced induction aplication as you need back presure running a normaly aspirated aplication or you will lose torque FACT.

Also price comes in to the equation £189 manifold - £149 decat - £259 rear section = £597 for something that dosnt make a difference in power

then adding this setup to an piggyback ecu to remap and get the potential out of it waste of dollars if you ask me.

[north]

I already gave the bhp change that you'll get and have to admit it isn't worth the money on the IS but I never said to go full on cat-less as the is200 needs some back pressure in the exhaust.

Just said this is the gain you'll get and this is how it responds to it... I went back to OEM for different reasons as I can't stand having a car that is tuned by someone else without me knowing exactly what it does (he didn't have prove) But i noticed a difference in the torque and when the car started pulling...

And honestly it doesn't matter as the car is now more fuel efficient ( especially with our economy right now this was one of the best changes I made to the car)

[fjcfarrar]

I do not agree with the above statement of not making a difference as I had mine with it and went original... The diference is there, You have to get the car up to 3000 rpm to start pulling properly as before that it would start pulling at 2500 rpm that makes a huge difference it might be around 5nm torque difference which you'd expect to feel in the mid range... but you feel it way earlier (doing the math this equates to around 7 to 10BHP depending on the state of the engine) also the OEM exhaust manifold has a pre-cat. And a cat is nothing more than a filter slowing down the exhaust gasses.

To make a long story short... IF someone changed the complete exhaust from the manifold al the way to the back-box one might have a power gain of about 5NM without a remap. Do a remap and you'll find the car running smoother and faster maybe with a little more gain might be 9NM or more.

Just to clarify. Torque is just the twisting force from the engine output shaft which is needed to overcome the initial inertia of the car at the lowest revs in each gear. At anywhere far from the lowest revs, Torque mathematically equates to Power as effectively the RATE at which Torque is applied and converted to increasing speed. In simple terms Torque provides only low-rev acceleration and is largely down to engine capacity - above that Power predominates and is more or less proportional to revs.

At low revs where Torque is demanded, gas flow is at its lowest so that is the last place that any change in exhaust system will have any effect - except that the engine design may require slight back-pressure achieved through resonances to optimise Torque. It is only at Max- Power near max revs - hence maximum gas-flow - that a more free-flowing exhaust could have any effect, and only if the unmodified system imposed any significant restriction. A "better" system can't help if there aint no more gas available to flow.

[north]

I had it did you?

My answers are based on actual experience... I didn't tell him to go bigger in exhaust diameter or anything like that (as that does change the exhaust flow). I didn't tell him to remove the complete cat, I told him to get rid of the exhaust manifold as that one has a restricting pre cat. To make up for that difference you have to put in a 200 cells sport cat.

And tada you'll have my old exhaust line that actually moves the torque curve to lower revs... this does equate to 5 to 10 NM difference. And if the car isn't chip tuned the car will pull all the way to the rev limiter at the same pace but it starts about 500 rpm lower. In BHP that would be 10 to 15 extra BHP my friend.

[DaveyCH]

Lol i have just bought all 3 of those exhaust parts for 230 off eBay, i bought a decat manifold, a 300 cell high flow sports cat downpipe and the catback exhaust. The buy it bow price on all 3 combined is 660 i got it all for 230 on auction.

[DaveyCH]

Because i am removing the standarm manifold with the pre cats, will this fail the mot even though i am using a 300 cell cat in the downpipe? was it a silly idea to buy a decat manifold to use with a sports cat downpipe?

[fjcfarrar]

Because i am removing the standarm manifold with the pre cats, will this fail the mot even though i am using a 300 cell cat in the downpipe? was it a silly idea to buy a decat manifold to use with a sports cat downpipe?

Probably not if it passes emission tests. There are all sorts of upcoming regulations about modifications, but if everything looks more or less normal; trouble is less likely.

As to the sense in doing it. Replacing a system that will handle at least twice the available gas-flow with one that could handle three times the available gas-flow just isn't going to do much. The only way to get more power that you will really notice is a charger. Even a piggy-back for the ECU can only move the shape of the power curve to gain here, lose there without compromising emissions - like moving lumps in a pillow. The (probably cheaper) alternative is to sell your IS200, get an IS300 which gets you 212BHP over 153 BHP with better low-end grunt and keeping bullet-proof reliability - less power than a charged IS200 but better mpg, lower insurance & more toys. Don't be put off by the IS300 only being available with an Auto gearbox; nobody who has gone that route is disappointed.

[DaveyCH]

to be honest it was a bit of an impulse buy, im not really bothered about performance increases it was more the fact that my standard exhaust is 11 years old, and even though its stainless and tuned as standard its starting to show its age and looking a bit tired. iv got the downpipe im waiting on the manifold and the mid section and backbox to arrive, when it does il upload some pics guys of the sections before they are installed to see what you think, wether iv got £600 quids worth of system for £230 or wether iv just bought a load of scrap steel :/ if its the latter it will be going staight back on eBay!! iv heard ppl have had problems with the sensor loacations on these eBay systems?