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Old 04 September 2011, 02:59 PM   #1
Micheru
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Default Do I need a remap to decat?

Hey guys,

I'm a bit worried as I've got a decat system for my car, but unsure whether it'll need a remap. Everything on the car is unmodified, will I need to fit a new sensor on the downpipe? Are there any other recommended mods I should do together with the exhaust system?

I don't want to damage something else by not doing it right first time.

Any help greatly appreciated!
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Old 04 September 2011, 03:16 PM   #2
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really it is wise to have a map with it and then you will get the benefit of fitting it
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Old 04 September 2011, 03:29 PM   #3
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what car do you have? is it mappable? if so then yes you should get it mapped stage 1 exhaust panel fiter and maybe fuel pump
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Old 04 September 2011, 03:30 PM   #4
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Is your ECU mappable? I'm assuming your car is a 95MY
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Old 04 September 2011, 03:30 PM   #5
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should be fine without, i had a full decat and no remap on mine for 8 years with no probs at all.
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Old 04 September 2011, 03:36 PM   #6
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Yeah it's the same car as in my profile. MY95 import sti wagon.

I figured performance wise a remap is in order, however the cost is the problem as I'd assume I'd need a new ECU for a MY95 import, as I've heard they aren't mappable though I'm not sure. I will probably not be able to afford it for a month or two if I'm looking at 600+ for that.

I've seen some threads on other forums and opinion appears to be split about running the car decat. I've read about detonation, but what should I listen out for exactly?
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Old 04 September 2011, 04:12 PM   #7
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as already said alot of owners have fitted de-cats ect to there cars and not had them mapped with no problems,but ive been through 3 engine so id say best to be safe than sorry and if its going to cost you 600 for an ecu?? plus the map 500+ it would just be cheaper to get a simtek fitted o and as for what you should listen out for,id start listening for engine failure sounds like an aerosol can
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Old 05 September 2011, 05:10 PM   #8
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cant you get a daughter board fitted and map for around 500-600 quid i think jolley green monster does these for that sort of money
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Old 05 September 2011, 06:43 PM   #9
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the pre 96 classics can cope without a remap but you do need a remap to make the most out em.
i fitted a decat to my 93wrx and the power gain was marginal using a z4 ecu.
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Old 05 September 2011, 07:11 PM   #10
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As dj says, you will be fine without a map to start with, but if you can stretch to a map then that will get the best out of it, you could go for an esl, apexi or similar, for not much more than around 400 quid.

I would imagine your car will be the same as mine with regards to sensors etc, you should have a cat on fire sensor in your current downpipe, which you just disconnect and blank off with a blanking plug in your decat downpipe, your lambda sensor should be in the headers.
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Old 05 September 2011, 11:43 PM   #11
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why not flog the exhaust an spend on the map instead my st5 wagons on a stock system and made 319bhp mapped to v power.
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Old 06 September 2011, 02:53 PM   #12
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alot of people will say u NEED a map....thats what they told me but im running a full stainless decat with no probs without a map
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Old 06 September 2011, 03:22 PM   #13
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Cheers for the replies guys, I can rest easy knowing I won't do any serious damage in the short term. As I said it wasn't so much about power at first that I changed, more about the standard sti exhaust system falling to bits and needing a replacement.

Quote:
Originally Posted by wrxsti280 View Post
As dj says, you will be fine without a map to start with, but if you can stretch to a map then that will get the best out of it, you could go for an esl, apexi or similar, for not much more than around 400 quid.

I would imagine your car will be the same as mine with regards to sensors etc, you should have a cat on fire sensor in your current downpipe, which you just disconnect and blank off with a blanking plug in your decat downpipe, your lambda sensor should be in the headers.
Yeah it's fitted now and I have to admit took a little while to get used to the loudness of a Kakimoto decat but I'm loving it. It had the cat on fire in my original downpipe. The new decat downpipe is heatwrapped so hopefully that'll be okay.

Quote:
Originally Posted by housty-wrx View Post
alot of people will say u NEED a map....thats what they told me but im running a full stainless decat with no probs without a map
I'm not feeling an increase in performance really, so I guess I'll get a simtek ecu for the dual maps in the next few months.

Mapping for v-power gives better performance/economy? Something I've noticed is that it smells like I'm running rich and there's a fair amount of popping on the overrun, is that normal for decat or just due to the map not being setup for decat?
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Old 06 September 2011, 03:31 PM   #14
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Quote:
Originally Posted by ginger321 View Post
why not flog the exhaust an spend on the map instead my st5 wagons on a stock system and made 319bhp mapped to v power.
Not really the same comparison given your starting point is near enough 300 anyway with way better i/c, injectors to name but a few things.

MY95 is 260, will never make 320 on the current exhaust/I/C/Injector set up.

Yes get it mapped, you can do lots of things in life and get away with it, or you could be unlucky and kill it very quickly

FWIW mine is decatted on a Polar chip but this is how I bought it and far from ideal for mechanical longevity. I have bought an APexi PFC which with other mods will be far better than a cheap bhp from decatting alone
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Old 06 September 2011, 03:46 PM   #15
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Quote:
Originally Posted by 53WRX View Post
Not really the same comparison given your starting point is near enough 300 anyway with way better i/c, injectors to name but a few things.

MY95 is 260, will never make 320 on the current exhaust/I/C/Injector set up.

Yes get it mapped, you can do lots of things in life and get away with it, or you could be unlucky and kill it very quickly

FWIW mine is decatted on a Polar chip but this is how I bought it and far from ideal for mechanical longevity. I have bought an APexi PFC which with other mods will be far better than a cheap bhp from decatting alone
Thank you for the advice sir. I had a quick look at the APEXI and it looks amazing. As I'm a keen admirer of your Wagon I may have to PM you in the coming months as I delve into a few mods

I guess I'm looking at the right thing here? Though I'd want the commander as well as the unit.
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Old 06 September 2011, 03:50 PM   #16
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It depends on the car and the fuel you use most of the time (ie a new age STI MUST be remapped or it WILL det), but the one thing you need to fit if you do decat is a boost gauge and a knocklink/ks3 minimum to monitor what is going on under your bonnet.

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Old 06 September 2011, 03:56 PM   #17
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Quote:
Originally Posted by TonyBurns View Post
It depends on the car and the fuel you use most of the time (ie a new age STI MUST be remapped or it WILL det), but the one thing you need to fit if you do decat is a boost gauge and a knocklink/ks3 minimum to monitor what is going on under your bonnet.

Tony
My old man only ran it on v-power as do I, dabbled with tesco99 in an emergency the other month.

I'll look into fitting gauges then, could be a bit beyond my skill level currently though. Though I'm willing to learn. Just don't want any potentially expensive mistakes, I've seen some guides on here though that look pretty detailed.
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Old 06 September 2011, 03:57 PM   #18
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I was talking about my new classic The wagon overboosted once the decat was on, this was fine as the next day it was being mapped with simtek. You never know what det is occurring when you start to guesstimate in AFR modifications. Failure can happen over time hence the 'my car never went wrong in the x amount of years I had it'. Trouble is the next person to drive the car may well stretch it's legs further up the rev range and booom !

Yep that's the APexi I picked mine up for 300 on ebay with commander

On your current I/C and injectors don't get greedy. Stick to 270/80 genuine horses and you'll be fine till you can afford FMIC, injectors etc. On the standard slanty I/C you will see death inducing charge temps if you push the map too far Even more concern if you run an induction kit.

On the new classic I am trying an ARC TMIC and flow modified injectors to see if a safe 300 is achievable. Ultimately FMIC is the goal but it's good to test new things
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Old 06 September 2011, 03:59 PM   #19
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As for gauges, you can install a mechanical gauge easily and cheaply T-piece, tube, gauge, holder, booooost
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Old 09 September 2011, 12:48 PM   #20
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Had my first backfire today, pulling away in first, at about 3k revs, lost power, big bang then it was normal. Car was warmed up and about 2 minutes after I'd come off the dual carriageway, wasn't driving aggressively at all so temps shouldn't have been higher than normal.

I'm guessing this is a sign to get the ecu sorted asap?
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Old 09 September 2011, 01:03 PM   #21
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Yes, could have been leaning out
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Old 09 September 2011, 01:34 PM   #22
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I think you're also in Essex? Could you recommend mappers in reasonable driving distance? Looks like I'll be poor next month! My insurance company will be less than happy too
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Old 10 September 2011, 06:35 PM   #23
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Speak to Rich at FB Tuning, or Simon Jolly Green Monster They're both traders on here
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Old 10 September 2011, 10:42 PM   #24
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you might get some pops and bangs out of a full decat, id say nothing to worry about after runnning mine for 8 years with d-valve and i=kit and no probs, but some wil say remap or it will die.
if youve been through 3 engine rebuilds snake1906 id say your doing something wrong... like screwing it too much !)
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Old 10 September 2011, 10:42 PM
 
 
 
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cat, change, chip, classic, de, decat, deffiatly, downpipe, impreza, lambda, my03, newage, remap, scooby, sensor, sti, subaru


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