The Welshman

Hey folks..
I was going to fit a 3" turbo back system to do away with the cats completely, probably HKS... But i have been reading some other threads and on there there are all sorts of warnings about it being a risky thing to do...Do I have to get a remap if i fit a turbo back system?, and if not what can i do about the warning light that it seems will come on?
Lastly is it better to lag the downpipe? and if so, why please?
thanks ,
Keith

RICH WILD

You only need worry about CELs if the car is an 01- model.

What model is the car.

Most cars don't NEED a remap with a full decat but it would obviously maximise the benefits of the decat in doing so. If you are planning no further mods it, then you would be best to reamp after the exhaust. if you plan to do more to the car, I'd leave it until later.

Lagging the downpipe serves 2 purposes. 1. keeps underbonnet temps down (more important if you have an induction kit instead of the standard airbox) 2. Keeps heat in the exhaust. The hotter gases are, the more kinetic energy they have, so the faster they move. This improves their flow out of the exhaust and helps to improve power.

The Welshman

Hi M8, thanks for the reply... unfortunately the car is a 2001 wrx uk spec wagon...What will I need to do, or get done?
Thanks
Keith

IanK Spec C

Hi Keith,

You can fit just the downpipe.

Occasionally the ECU performs a Cat efficiency check(usually when in steady state running). Clearly with the decat it will fail this check. The car will then display a CEL, which doesn't affect performance. The light goes out after 5 engine starts. Some people just ignore this. You can fit a device to fool the ecu to think the CAT is healthy to prevent this problem.

You have PM.

Regards,

Ian

stevenuk300 still

iTrader: (1)

Sorry to highjack this thread, but I'm also looking to replace the up pipe and down pipe on my UK300. However have also heard about problems, but spending £700 on a Tek3 will sort out, for e.g. boost spikes. I would love it fully decatted, but it looks like it's going to cost near to £2000 to do it. How common are these problems? If I can I want to do it without the remap, otherwise I'll have to re think.

Daz WRX

The remap is there to make the most out of decatting, and using software to remove the CEL error, alternatively as mentioned above a device can be wired in to stop the CEL comming on. I have one of these you can have for £40 if you like its the fix for the downpipe decat.

Cheers
Daz

Mev443443

Is there need to remaping or using any other CEL fix if i de-cat just middle pipe?

Thx

hades

No offense to Daz trying to sell his bits, but there is also a CEL fix you can do for 22p if you can use a soldering iron - do a search, I posted the instructions a year or two back. Has worked perfectly for me for about 30k miles now . . . .

Shouldn't need the CEL fix for removing the cat in the centre section.

Quite a few people have decatted up and down-pipes of WRX's without having a remap, doesn't seem to have caused major problems. I ran my 02WRX with decat uppipe/sports cat downpipe for a short while before the remap was fitted, seemed happy enough. However, it did go better after the remap.

Decating the downpipe in the STi7 (no up-pipe cat it an STi) does seem to cause major boost spikes, so not recommended without a re-map.

All IMHO, of course

The Welshman

Thank you for all the help folks... but being somewhat of a technical genuis??? there is still something that I am not sure about...If the warning light goes out after 5 starts, why bother having it fixed to go out, if it does so anyway?
Finally I have decided to go with a Janspeed 3" downpipe, and a hks hyper system with bung, ( old-ish neighbours) 3" all the way and no cats ... bought them today, and will get them fitted next week...Cant afford a remap at the moment, and someone told me that the managment system will compensate ok for the better flowing exhaust? what do you think?
This place is great,,, where else can you get this quality of help for free!!
Thank you
Keith

hades

I expect you'll find the engine will run a bit rough the first time you put your foot down after fitting the exhaust, and you'll wonder whether you've done the right thing. After a few miles, it will begin to "learn" the benefit of the exhaust, and things will be a lot better. 100 miles and a couple of starts later, the ECU will have learned all about it, and it will be a big improvement - a bit more power, and the turbo will come in at lower revs, and the power will stay on to higher revs. Don't just take my word for it, though, you'll find out next week.

If you have fitted a downpipe and an HKS hyper system to a WRX, you still have one catalyst left - in the up-pipe (before the turbo). Worth taking that one out too, gives a bit more improvement still, and allows you to run higher turbo boost (e.g. if/when you get a remap) more safely.

You'll find that whilst the ECU will learn its way round exhaust modifications, and you will get more power etc, it will go faster, smoother and generally better again if/when you get it remapped. Doesn't need doing straightaway, in your position I'd recommend up-pipe as the next modification, and then a remap after that, do it all when funds allow.

When I had the cat inneficiency CEL, it never went out (unless I reset the ECU), so I have my doubts about this "5 starts" idea. My view - apart from it being irritating to have it on, how will you know if there are other problems if it is stuck on permanently? Thats why I did the 22p fix.

The Welshman

Thanks for the help..it is very much appreciated.. Have a load to learn here, and this really helps...
I will follow your advice M8, get the uppipe done at the same time as the rest of the system is fitted. If I have a problem with the cel light I will attempt to do that fix myself, if I can find the part that needs doing ok!!
Looks like I need save for a remap eh?, before I do is there anything else that you would recommend as a fairly simple or inexpensive way of gaining some more performance?, Acceleration is what is important to me...not top speed. Thanks again.
Keith

hades

With full decat and remap, you'll probably get somewhere around 280bhp, and >260lbft torque (at least on PE's rollers). You might get nearly 300bhp and 300lbft, by changing the headers and putting an uprated intercooler on, and re-mapping to suit and that would be the limit without changing the turbo. Both mods would cost £100s.

Cheap things that will help a bit? Samco hoses to the intercooler (<£100), maybe a second hand STi intercooler (£200+), uprated inlet hose (£200), ported headers (cheap if you can do it yourself), removing the inlet resonator. Maybe some form of induction kit or uprated panel filter. However, even adding all of these together, the difference would be relatively subtle.

If you change the turbo, a lot more power is available (I've been in an 01 WRX with >380bhp, for example). However, the clutch and gearbox will probably struggle if you go much over 300lbft, and that's where it starts to get expensive.

Personally, I'd recommend living with the existing turbo - if you want BIG power, you'd be better starting with an STi. If you want to spend more money, I'd look at sorting out the suspension and brakes.

Do a search on the mods I listed above if you want to find out more. . . .

TONY F

hi all, fitted a decat down pipe today. couldn,t belive it was the same car picks up really well

ps only took 3 hours (how many bolts on the heat sheild)

tony