dragracer1 0 Posted May 11, 2011 Report Share Posted May 11, 2011 i have just made a decat pipe to fit from my performance manifold and need to know if i should have the sensor in it still, as there is no cat there anymore! will this cause problems with the ecu? what does everyone else have in there decat pipe? thanks mike Link to post Share on other sites
VR6_Absy 0 Posted May 11, 2011 Report Share Posted May 11, 2011 Yes ur car needs it Link to post Share on other sites
VR6Pete 1,455 Posted May 11, 2011 Report Share Posted May 11, 2011 yep, as above.. you will need it.. Link to post Share on other sites
dragracer1 0 Posted May 11, 2011 Author Report Share Posted May 11, 2011 my golf has two sensors one before and one after the cat. will it effect it having one after the cat still in the system without the cat being in there or is that how they all come? Link to post Share on other sites
craggsy 91 Posted May 11, 2011 Report Share Posted May 11, 2011 my golf has two sensors one before and one after the cat. will it effect it having one after the cat still in the system without the cat being in there or is that how they all come?You will need to keep them both in place I do beleive. As your canadain then you have the mk4 chassis and it will need them Link to post Share on other sites
VR6Pete 1,455 Posted May 11, 2011 Report Share Posted May 11, 2011 My punto had a broken downstream lambda and it failed it's MOT. so i'd have thought you'd need it. Link to post Share on other sites
bungy 2 Posted May 11, 2011 Report Share Posted May 11, 2011 You'll need to re-map the car for a de-cat as it will throw a fault to the ECU. Their will be no differentiation of reading between the 2. Link to post Share on other sites
dragracer1 0 Posted May 11, 2011 Author Report Share Posted May 11, 2011 ok thanks ill try it with both in and if it does not work ill have to think of a way round the problem. what is the second sensor in there for? if it is after the cat then surely not doing much> wierd Link to post Share on other sites
dragracer1 0 Posted May 11, 2011 Author Report Share Posted May 11, 2011 ok so how do i get around it without remapping it? Link to post Share on other sites
UnitedMotorsport 55 Posted May 11, 2011 Report Share Posted May 11, 2011 What car/ECU is this?How many lambda probes are there in total?My guess is you have an OBD2 VR6 with PRE and POST lambda sensors. If this is the case Bungy is correct. Link to post Share on other sites
dragracer1 0 Posted May 11, 2011 Author Report Share Posted May 11, 2011 it is a 1997 mk3 vr6. there are two sensors one before and one after the cat, there must be a way around getting it remapped. i wont be able to get it done for a while as im going away! Link to post Share on other sites
dragracer1 0 Posted May 11, 2011 Author Report Share Posted May 11, 2011 what if i was to weld a small threaded box on to the outside of the pipe where the sensor would normally go in to the exhaust. and put the sensor in it? it would get hot and have clean air being in a sealed box that is not in the exhaust system! does anyone think this would work i dont see why not! Link to post Share on other sites
UnitedMotorsport 55 Posted May 11, 2011 Report Share Posted May 11, 2011 That wont work, as the ECU is expecting to see a certain lambda figure from that probe. When the ECU doesn't get what it expects it will log a 'CAT outside of efficiently) and turn on the CEL.Clean air has a VERY high lambda figure, correct exhaust lambda is 1.00 Link to post Share on other sites
dragracer1 0 Posted May 12, 2011 Author Report Share Posted May 12, 2011 ok so it is expecting to see a certain resistance coming back from the sensor!, can you buy a plug to plug in to the sensor conector or make one with a resistor in it to show it what it wants to see? Link to post Share on other sites
UnitedMotorsport 55 Posted May 12, 2011 Report Share Posted May 12, 2011 Lambda sensors do not work on resistance.The ECU is also clever enough to run a self test, buy altering the calibration of fuel, and checking for it with the lambda sensors. When it sees a static figure, it will throw an error code and bring on the CEL. Link to post Share on other sites
dragracer1 0 Posted May 12, 2011 Author Report Share Posted May 12, 2011 ok well it works so far so good ill let you know if it keeps working without the light coming on! Link to post Share on other sites
dragracer1 0 Posted May 13, 2011 Author Report Share Posted May 13, 2011 well i welded a small box with a nut going in to it on the side of the decat pipe which the sensor screws in to. it is running fine and no light on either. so fingers crossed untill i can get it all remapped. i want to get cams in it before i get it remapped because ill have to take it off the island over to vancouver so its alot of hastle! thanks for your help Link to post Share on other sites
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