Raster

Hi, over the next few weeks i'll be looking to replace my existing 2.5" d/pipe and centre sections with decatted 3" parts to compliment my BPM Twister b/box. Will anything else need to be altered/adjusted or is it a simple case of swapping old for new, leaving everything else as-is?. I'm pariticularly concerned about the lambda sensor, which i assume will be redundant after decatting, and the effect it may have.

I'd appreciate any comments, even if there's nothing to worry about - just to put my mind at rest.
Thanks.

UkLegacyT

hi mate, i have the legacy turbo running the same engine as yours. i have a 3" system and it works great.
as for which parts work with what....not sure.
but however, you mention the lambda sensor. this is used regardless of whether the car has a cat or not, as its nothing to do with it, despite what many people think. the sensor allows the engine to monitor the air/fuel mix. the cat just cleans the exhaust fumes lowering the carbon monoxide.
the new downpipe will come with a hole for the sensor, just rearwards of the turbo.

ian

ktm1974

the 93 wrx has a overheat sensor in the downpipe not the lamda,this is in the manifold. i beleve you dont need this with the decat. The overheat sensor has a connector on the drivers side of the engine bay just under the master cylinder.the hole in the new down pipe is for the later scoobs that have the lamda in the down pipe and is not used


paul

ps if this is incorrect could somebody please post because i am replacing my cat with a decat on monday when i replace the cluch

[Edited by ktm1974 - 3/30/2002 8:15:08 PM]

teknopete

Raster,

Decatting won`t cause any probs bud. The sensor u r refering to is indeed as ktm pointed out a "cat on fire" sensor which isn`t needed once decated.
Best plan of attack is completely unplug the sensor at the socket
As has also been pointed out irrespective of what DP u use the lambda sensor is essential to the correct running of the car (on the 93 it`s in the manifold and tends to overheat regular) best bet is fit another in the new downpipe and detach the old one or if u r running a link use both (1 for a feed to the ECU and one for the lambda link) thats the way mine is set up and no probs with it What it does do though is gives u a double check because when the manifold 1 overheats (usually under idle) u can refer to the 1 in the DP. U can even do this w/o the link ECU,
jus get a lambda link and new lambda sensor. That way u don`t have to plug the hole in the DP as the new sensor does it

Hope this helps
Pete

Cosie Convert

I can second Pete's comments.(apart from the Link bit cos he can afford these things )
You can get a lamda sensor for the downpipe from halfords for 49 pounds. Soon pays for itself in improved economy as your standatd one is probably u/s by now.

teknopete

Cheers CC,

But don`t u believe it u should see my credit card statement m8
Tell u what I did do though, my second lambda probe is actually a
bosch wide range probe and is lead tolerant, so it doesn`t mind octane booster n stuff bein added 2 the fuel. Sure it was about £115 or there abouts, but will balance out in the long run

Pete

Raster

Thanks all for the information, certainly cleared this issue up
I rekon i'll disconnect the old lambda sensor in the manifold and fit a Halfords jobbie in the new d/pipe, to avoid the overheating problem and hopefully get a few more mpg too.

Thanks again,
Geraint.

highlander

Interesting reading on this topic - I have a 93WRX which I have just had de-catted with a Mongoose Turbo back system and am suffering problems with poor running of the engine and power loss.
On inspection there is nothing on the downpipe which connects to any electrical wires. Does this mean that my Lamda sensor from the old DP has not been re-fitted to the new DP and am in fact running without one at all? What does the Lamda sensor look like and where are the wires it should connect to?

Markus

Power loss might, just might, be due to overboost. On the blackbeast (MY94 WRX Wagon) I've got a BPM Twindump downpipe mated to Apexi N1 center and backbox, thus it's 3" all the way, this does cause overboost, basically, it boost up to 0.9 bar, then immediatly drops to about 0.5 then back up to about 0.8, then down to 0.5 again, then back up, where it stays. Could this be the same for your powerloss?

highlander

My boost seems to have dropped to a max of .8 Bar as opposed to 1bar which it normally runs - just gonna do the Solenoid trick with the brake cleaner.

teknopete

Highlander,

On the YM93 the lambda sensor is in the manifold, not on the downpipe. The electrical connection / sensor on u r old downpipe was a teperature sensor for the cat, this is no longer required as the system u have fitted is cat-less As for the position of the lambda sensor if u jack the car up (or get it on a 4 poster)from underneath the lambda sensor is approx 12-18" back form the front of the car on the driver side. Can`t remember off the top of my head but i`m sure theres a white or grey connector with 3 or 4 wires connected to it. Thats the connector for the lambda probe

Pete

highlander

Thanks pete - will check it out

teknopete

Peebs,

Just uploaded some pix of the early WRX lambda sensors to my site
http://www.scoobymods.co.uk/lambda02.jpg and http://www.scoobymods.co.uk/lambda04.jpg for any1 that still can`t picture where they are The second pic shows the additional lambda sensor i fitted (wide range) for when mapping the link and a double check as mentioned earlier.
I know the pix r small but hey I got bandwidth 2 think about

L8r
Pete