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Old 28 May 2012, 02:53 PM   #1 (permalink)
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De-cats

Hello all,

Ive just bought the down pipe, cat pipe and centre pipe all without cats from scoobyworld.

Has anybody else had these fitted? will look to get them on this week, also bought the lowering springs and quick shift kit.

Next month will be the sc36 turbo and then a remap!!! do you think i should buy a walbro fuel pump as well? also thinking about the pink injectors...

Should get around 320-330bhp

Regards

Lee
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Old 30 May 2012, 11:33 AM   #2 (permalink)
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Re: De-cats

wait till you get it in for map before fitting all the decat parts. on a new age removing all the cats results in boost control issues 95% of the time.

for new turbo you will need fuel pump and prob injectors, uk300 runs wrx injectors so only 440's.
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Old 30 May 2012, 04:05 PM   #3 (permalink)
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Re: De-cats

Hi Tidgy, the downpipe, decat and centre section pipe arrived today. Spoke to power engineering and they advised to get a up pipe as well and then a re-map.

Just ordered the up pipe and will try and get it booked in next week. Be interesting to see what bhp i will get out of it. i got 225bhp on a power run test when i bought the car to see if had been pro drived as it had pro drive mud flaps!!

im hoping for around 260bhp. Next month will get the fuel pump, pink injectors and sc36 turbo and been told can be anywhere from 315bhp to 330bhp

Should of just bought an STI!!!!
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Old 31 May 2012, 10:55 AM   #4 (permalink)
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Re: De-cats

hehe, alot of folks say, should have got an sti, just depends on your eventual goals.

no point in spending 10% more for what you replace anyway

you should see 260ish, you will be limited by your turbo
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Old 23 Jun 2012, 12:05 AM   #5 (permalink)
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Re: De-cats

tidgy, just going down the same route, i have a replacement conical filter in place, and a full turbo-back decat system on its way....next up is a mild remap to add about 40 bhp, giving me approx 265 (hope) on my 2004 wrx, otherwise standard set-up....
i just wanted to clarify your advice above about getting a remap before fitting the decat? maybe i've totally misunderstood you, i thought it would be the thing to do to get all the mods fitted first, then the remap, so the ecu knows what components/systems are doing?
forgive me if i've taken you up wrong....
cheers
billy
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Old 23 Jun 2012, 12:08 AM   #6 (permalink)
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Re: De-cats

ps..lee sorry for the hijack!
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Old 23 Jun 2012, 03:34 AM   #7 (permalink)
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Re: De-cats

The maps don according to you engine mods lol

I think what Tidgy meant was take it to the mappers and then get the decat fitted and remapped

As the o2 sensors will monitor the air and fueling before and after differently as a part knows whether the CAT is working correctly, by removing the CAT, the lambda readings will be 'incorrect' and the ECU will assume the CAT isn't working and adjust the workings of the engine accordingly. It may retard the igniton, fueling etc and with a new turbo it will run ruff and it might just end up triggering you CEL on.



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Last edited by ccsworks; 23 Jun 2012 at 03:47 AM.
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Old 23 Jun 2012, 05:03 AM   #8 (permalink)
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Re: De-cats

ah nice 1 , thanks m8!
yeah i had a full decat for a year after buying the car but removed it when i took a notion to sell (don't ask! lol) the CEL light was on the entire time that it was fitted, but after getting it checked i was told that the exhaust was the reason and not affecting the performance so i never worried about it...is this wrong then? does the CEL light being activated by bad lambda readings cause the engine to rub at lower levels? i've since decided to keep and upgrade her so want to make sure i'm not wasting my time,
thanks again!
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Old 24 Jun 2012, 12:53 AM   #9 (permalink)
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Re: De-cats

if some back street garage has told you the CEL doesn't effect the performance there wrong the CEL does affect the performance in a big way.

basically you wont get the best performance results or fuel mileage out of the car because the engine is showing a fault with the CEL on.

your fuel levels change according to your rpm any how you got to much air and less fuel on high rpm you will end up detonating the engine.

when the decat triggers a lambda fault you will feel this on the lower levels because your air and fueling is not right It’s important for the air and fuel to burn right to get good results and for that you will need a remap so they can alter the igniton timing fuel and air etc according to your mods.

you not really gaining any large amount of BHP you have only released around 12 psi pressure which the cat hold its probably dropped down between 3 to 6 psi with the decat and took the load off the engine with a better flow.

because your fuel and air is not right you just losing out on large amount of un burnt fuel which might couse detonation once in a while.

you still have stock map on the ecu which thinks the cat is still there it dosnt have that much ability to self learn and make that kind of adjustments the ecu self learning part ends on little leaks on the exhaust which it might be able to alter.

I would get it mapped according to your mods to get the best mileage out of fuel and and good results in performance. you will save money on long run and wont be disappointed on the performance. i have had mine done and it feels like a feather weight.

I would chose the fuel you would use and stick to the same fuel after the map.
Tidgy can give you more info on why this is importend



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Last edited by ccsworks; 24 Jun 2012 at 01:02 AM.
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Old 24 Jun 2012, 09:03 AM   #10 (permalink)
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Re: De-cats

many thanks again m8 for a very informative answer, much appreciated!
the car had its full decat system removed 3 years ago and the cel light read, checked and cleared by a reputable local garage, who said that it had been on the entire time due to the decat, the fault code stating exhaust emission issues.......fair enough i thought. during this time i def noticed a slight performance improvement, no fuel consumption and no running issues at low or high speeds...the mechanic has been a subaru specialist for 20 years and his dad before him, he has done loads of work for me and would have a good reputation in the area. he told me that it might take a couple of times for the cel light to go out completely with the std set-up back on (just an aftermarket back-box) and this was true; i have had it reset twice and it has currently been back on for a month, the funnny thing is, again i notice no running issues at all

in run the car on 'super' (97) but havent always done that;
with me having to take the decat exhaust off once a year for MOT, will i have to then have it remapped again after every removal/refitting? that would make the MOT a bit more expensive lol!!
anyway, just to confirm then, better to have the exhaust fiited then take her for remap and hopefully they will sort the cel issues as well as upgrade her?
cheers m8 for all your help, and Lee i hope this hijack is maybe beneficial to both of us....
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Old 25 Jun 2012, 01:57 AM   #11 (permalink)
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Re: De-cats

no problem m8 if you do get it mapped you wont need to take the decat off for mot, i have had my bugeye mapped and goes through fine every time. am paying 118 on the road tax for 6 month. And mileage to fuel is excellent a long with the performance.

on the other hand i had a 1.6 sports impreza wagon which i use for running around from the garage and i was paying 148 on 6 months tax totally standard no mods.

one of the lads who work for me just had his don on a after market down pipe and the rear box the CEL came on but after the map it was all good.

good luck



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Old 25 Jun 2012, 08:42 AM   #12 (permalink)
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Re: De-cats

cheers again m8!
i don't know if the MOT rules are different here in NI from mainland UK, as i was told i would have to refit original cats, but she's not up til feb so that can wait i suppose lol!!
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Old 26 Jun 2012, 07:40 PM   #13 (permalink)
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Re: De-cats

Evening all,

Need some help. As above I have a full exhaust decat system ready to be installed when I get the wrx chipped, however my friends dad has booked a track day for me as a favour for doing some work for him, going to Oulton park on the 31st July, so far there is a Austin Healy, 911 turbo and a 599 and a gtr going.
I have seen a vf34 turbo and injectors for 500 from jap performance so buying them, question is will I need to upgrade the inter cooler to an sti one? I have a sti scoop getting painted at the moment so that should get more air to the inter cooler, I'm looking hopefully to get around 320bhp. Will the standard inter cooler be alright for the v34 turbo?

Many thanks

Lee
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Old 27 Jun 2012, 01:37 AM   #14 (permalink)
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Re: De-cats

what year is your car lee are you getting your ECU chipped or remapped ?

the sti inter cooler is better then the standard wrx one as long as your putting a bigger scoop for better air flow.

bear in mind the STI inter cooler is bigger in size as well so don't forget to put the sti under tray under the bonnet otherwise you will be worse off than standard WRX inter cooler.

are you all so upgrading the fuel pump as well ? it wont really change the fuel pressure unless you upgrade the fuel pressure regulator but then you got to watch where your bhp is going as well been a wrx i wouldn't hit over 330 max to be on the safe side.

a lot of people change the fuel pump simply depending on the age of there car mostly on classics just to be on the safe side in case it get knackered but as i said it will run on the same pressure unless you put a fuel pressure regulator.

I would recommend changing the fuel rail as well when you doing the injectors.

and i would put a oil pressure kit and oil temperature sensor over number 3 as that's the common cylinder that frictions out and gets the hottest and the one which always detonates.

and if the oil does get hot over the limit i would recommend an oil cooler so the engine internals can stand high boost.

its all about making the engine last at the end of the day and having good results in performance. Theses little things will help.



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Last edited by ccsworks; 27 Jun 2012 at 01:40 AM.
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Old 27 Jun 2012, 10:34 AM   #15 (permalink)
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Re: De-cats

Thanks for your post ccsworks, i have a 2004 wrx and will be upgrading the fuel pump as well as its only 70 so its not going to break the bank and every post ive read about tuning they all recommend to do so.
I would like to hit 330bhp but would be happy with anything over 300, i had a bugeye sti which was running at 341bhp so just looking somewhere roughly around the same.
Just spoke to Power Engineering and they recommend an STI intercooler so will make sure i get the under tray. Just need to call Jap performance to see if they can do a deal on injectors,turbo and intercooler....
I will monitor the oil situation... do you know roughly the costs of getting that done?
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