Subaru WRX Forum banner

Cat-less Downpipe and turbo back with no EM

11K views 19 replies 7 participants last post by  RogueMantis 
#1 ·
So I have barely had my car as I bought it on Christmas Eve. After driving around for awhile I've decided I need some type of Engine Management to help my car out. It is a 2002 Wrx Wagon with a Catless everything, Uppipe, downpipe, and turbo back. It runs and sounds nice when not at idle. At idle the exhaust is a little distorted and gives an in and out sound if that makes any sense. It will sound better for a couple seconds then go back to muffled, then to clear. I'm pretty sure I'm getting CELs from the O2 sensor but I still need to get those checked. And I think the rough idle is caused by my unhappy CPU. Right now I'm assuming its only the O2 sensor because everything else it doing pretty well. I don't believe I have anymore vacuum leaks because I'm hitting full boost and holding a better idle pressure. I'm looking at getting an Accessport v3 for my car and use a stage 2 tune. If I go this route I'll probably upgrade my air filter, change spark plugs(going to do anyway). I've also been looking at Open Source tuning and it is almost looking like a better option for my car, I have a laptop and I am really good with technology.... Just not sure what to try and do at this point. Should I save up for the AP or go with OpenSource tuning. And just some FYIs, I don't want to make a ton of power, I just want the car to run a little better because I feel like the mods are throwing the ECU off, the car has a little over 202,000 miles, Transmission was a needle in a haystack, but I found a really good one. Just don't want to push the engine at this high of miles. I would be ok with the Stage 2 boost levels though. Just don't want to do something I'll regret.
 
See less See more
#2 ·
Please dont run your ECU based car on CATless anything without proper management. Your ECU is expecting specific values from those sensors and if you are allowing more flow than the ECU is expecting it will try to tune out your components to return you to "stock" levels. If you end up with an accessport it will give you the ability to add your own tunes to the car or you can take the car to any reliable shop with a dyno and have it tuned. The accessport will not come with any maps that work for catless anything so catless should really be handled by an E tuner or a professional tuner. I personally had great luck with Eric fro Torqued Performance. His E tunes are pretty solid and very affordable.

In any case get all your parts installed (including new plugs if its time ) before you get tuned because making changes means re-tuning, at least for big changes.

//hippy rant// you will make very little extra power by removing CATs entirely. the benifit of CATs is there for everyone so we dont have to breath harmful chemicals and high flow honeycomb CATs cause so little flow interference it is negligable until you are well beyond simple "staged power" levels. Be kind to your fellow man and kind to the enviornment and throw a CAT in the line somewhere //end hippy rant//
 
#4 ·
Please dont run your ECU based car on CATless anything without proper management. Your ECU is expecting specific values from those sensors and if you are allowing more flow than the ECU is expecting it will try to tune out your components to return you to "stock" levels.
For the 02-03 this is FALSE!!! And I have proved it! It is still true for all others.
 
#3 ·
Well first off read this http://www.wrxtuners.com/forums/f52/my-evil-plan-build-thread-50946/ (You too arcticscythe) Skip to page 4 post #60 of that thread. You don't need an access port with a 02-03 bugeye. They have a different ECU than the others. It has a much more forgiving ECU. You can "bolt-on" to your hearts content. This makes it better to build over time. When you are done bolting on, get a tune.

As for your specific problem check or do this...2.2K Ohm Resistor Mod It should look like this. http://i15.photobucket.com/albums/a360/kurleedaddee/Resistormod.jpg And this...O2 Simulator, Angled O2 Simulator clears p0420 / p0430 check engine light mine looks like this...http://i1371.photobucket.com/albums/ag309/fidrat24/IMG_2395_zps909ed6bd.jpg
Don't forget to reset your ECU or the CEL won't go away right away.(disconnect the battery and step on the brake for a min or 2 then reconnect the battery,heck, you might wanna' try this first) I hope this helps. Good luck.:)
 
#5 ·
Does it handle out of range values differently on the 02? any car with a computer and o2 sensor Ive ever worked on has always attempted to correct for out of range values. It may not be as harmful as it is on say a 2008 but the ECU is still trying to make corrections for those values otherwise it wouldnt be pitching a CEL.
@jake, go with fidrat he runs one day to day but i still say bolt your stuff up and get a tune proper, even if the car doesnt care at all you will see better power and reliability with a proper tune.
 
#6 ·
Does it handle out of range values differently on the 02? any car with a computer and o2 sensor Ive ever worked on has always attempted to correct for out of range values.
This is true for 04 WRX and up AND without the mods I suggested. And this is true too. "Even if the car doesn't care at all you will see better power and reliability with a proper tune."

Does it handle out of range values differently on the 02? Yes, it does. It's the open loop VS the closed loop ECU that is confusing you
 
#7 ·
I ran catless everything on my 05 with a Stage 2 OTS Map from Cobb. So if you get a Cobb AP then you will be fine even though the map states with a CAT.

But Fidrat is correct you don't really need it persay. But a tune either OTS or Pro will unlock some good power from those Mods.
 
#8 ·
If you get a Cobb AP then you will be fine even though the map states with a CAT.
I don't think this will work if you run 91 octane. Unless something has changed since the last time I looked. I also want to add you have a different engine and ECU. 2.5L VS 2.0L
 
#9 ·
The 05 has the 2.0

I had no issues at any point with the Stage 2 OTS Map when fully catless. The 1 thing was boost spikes but that was only if I downshifted fast an went WOT instantly.
 
#11 ·
Yeah the ECU is different. I run/ran 93 in it, when I was "Stage 2" and now with 409whp.

But either way I just wanted to state that in my experience the Stage 2 OTS provide by Cobb worked perfect for me when I fully catless. I had no other Mods at that time other than the EBay special exhaust system.
 
#12 ·
I think I might try something with the O2 sensor ,so it'll stop throwing codes, until I'm able to have my car ready for a good tune. Air filter, plugs, fluid changes(I haven't done them all yet), I'm thinking about going back to a stock intercooler because I have some yellow one where the bolt holes don't line up right so its just the connections keeping it in place, I'm just not sure about it staying in place all the time. I can use my friends he'll give me for $20. Also probably going to take the car in today and get my codes read to make sure there is nothing unexpected, and it has been a few days sense I reset the ECU.

And just so everyone knows I bought the car with a cat less system because I thought it would be better. Which I'm not complaining about. I would be more worried about catalytic converters with 201,000 miles on them. I've just fixed vacuum leaks and few other things so far.

So just curious about the whole tuning thing...
So I mod my car for a good tune for now. I communicate with someone mentioned above, or anyone is local about what mods I have and what kind of tune I need. So does someone just make a tune for my car and I can use my computer and the required equipment to flash my ecu with the tune that was made? Of course saving my stock tune to a couple locations before I flash it. This is kinda what I'm looking for. I don't want to shell out a ton of money for dyno runs or have people tune my car on the streets but it doesn't seem that I'll have to if I'm correct. Just some clarification on that would be helpful.

I'm also planning Coilovers soon because I'm not to keen on lowering springs, not bad just want something better. Would that effect my tune at all? I don't think it would but I don't think it hurts to ask.

BTW finally getting to play around in the snow!!! Subaru for life haha
 
#16 · (Edited)
OK, I'll try to answer all this as best I can. Just so you know I have never tuned a car in the modern sense of the word. (with a computer) The last time I tuned a car was with a SUN machine and a strobe light.:eek: When it came time to tune my car I took it to a well known tuner ,a 2 hour drive!(P&L Motorsports open source pro-tune from Junior Barrios on a Dyno-jet)

Don't spend a lot of money getting your codes read. Autozone will do it for next to nothing. If not nothing.

{Q}Does someone just make a tune for my car and I can use my computer and the required equipment to flash my ecu with the tune that was made? {A} Rom Raider...This is best left to trained and experienced people. If you are one of these people than you wouldn't have to ask.

The cost of a pro-tune is no more than you would pay for an AP and if they screw it up the shop should cover it, Cobb will not!.
Junior Barrios is a well known tuner that pimps himself out to shops all over the east coast. The farthest west he goes is Chicago. Check him out at JR Tuned. I know JR. Is probably too far away for you but he is a good example of what you should be looking for in a tuner. Don't just let Joe blow tune it.
 
#13 ·
@GSMNZ Drat! I had a glimmer of hope that I could use an Accessport v3. Damn crappy gas! I think my ECU could have handled it. And you say the AP can handle the catless thing. The only other thing that is holding me back is the fact that I have the O2 sensor fooled and I have a resister telling my ECU everything is OK coming from my uppipe. Anyway,this is all moot if I cant get the good gas I would be dancing close to a knock situation. Bad ju'ju' for the Subaru:crying:

I just had a thought.. @arcticscythe why would my ECU try to correct for out of range values if I have the O2 sensor fooled by the O2 Simulator Angled Cel Fix and the resister mod is telling the ECU everything is OK coming from my uppipe?
@Jake Vanderlinden I highly recommend you look into the mods I recommended. If they are already on your car they may be failing.
 
#14 ·
Drat! I had a glimmer of hope that I could use an Accessport v3. Damn crappy gas! I think my ECU could have handled it. And you say the AP can handle the catless thing. The only other thing that is holding me back is the fact that I have the O2 sensor fooled and I have a resister telling my ECU everything is OK coming from my uppipe. Anyway,this is all moot if I cant get the good gas I would be dancing close to a knock situation. Bad ju'ju' for the Subaru:crying:

I just had a thought.. @arcticscythe why would my ECU try to correct for out of range values if I have the O2 sensor fooled by the O2 Simulator Angled Cel Fix and the resister mod is telling the ECU everything is OK coming from my uppipe?
Are you saying that with good gas plus fooling the ecu can create a knocking situation in the engine? And what is good gas? I've been running 91 octane from Shell. Best I can get here besides e85 but I'm not anywhere close to needing that. I'm just worried about creating an engine issue by fixing this one issue.
 
#18 ·
read this if you havent already.

RomRaider ? View topic - How-To: Bad Noodle's Beginner's Tuning Guide

then after read this if you havent already.

RomRaider - Open Source ECU Tools | Documentation / RomRaider FAQ

then sign up for HP academy's *FREE* introduction to tuning lessons (you can sign up for more like i did. but at bare minimum watch the free tuning lessons)

https://www.hpacademy.com/

then go grab your base map form romraider and start tuning.

RomRaider ? View forum - Base Maps

its all completely free. all you have to do is read and learn! tuning is not magic. its a science, and you can learn it.

enjoy :)
 
  • Like
Reactions: Fidrat
#19 ·
Update

I did a spark plug change to NKGs Iridium (NOT one step colder) and my check engine light stayed off for the longest time before coming back on again. I guess I could say everything is a little better though. The idle is a lot smoother and not as cranky and the response and boost levels are more consistent. My friend helped me out on the change and we found that whoever had the car before the people I bought it from tried to do a exhaust sensor mod. Not O2 sensor, it was the temp sensor. He had a resister going into that sensor port. I almost think whoever did this thought it was the O2 sensor they modded. I'm not really sure why he would do this otherwise. Sometime soon I'm going to make my way to a Subaru dealer and get my codes read. The car is running fine and is getting me back and forth to work for now so I'm not super worried about it right now. Just hoping its only the codes I'm expecting. Once I have that squared away I'll probably put the O2 sensor mod on the car to see if that helps. In the meantime I'm going to learn all I can about tuning before I actually try it. Suffering from Asperger Syndrome makes stuff like this fun though haha. I'm pretty sure I can learn to be a pretty good tuner,at least for my needs. But if anyone has anymore recommendations on learning how to tune I'm open to all suggestions.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top