jeffbebe 1560 Report post Posted April 2, 2013 Seem to remember a post about this where somebody said that if you de-cat an E39 you have to remap ECU if it has pre and post cat sensors. Can't find the post and thinking of doing this. Assuming this is the case (it makes sense) can anyone tell me if a 1996 E39 528i has pre and post cat sensors. Not too sure how to check or find out? Thanks in advance. Quote Share this post Link to post Share on other sites
Michael. 2313 Report post Posted April 2, 2013 Aside from that, when you replace cats, sometimes its best to put in two resonators or small round mufflers, otherwise you can get a bit of a rattly sounding exhaust as the cats tend to suppress some unwanted sounds. Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 3, 2013 Aside from that, when you replace cats, sometimes its best to put in two resonators or small round mufflers, otherwise you can get a bit of a rattly sounding exhaust as the cats tend to suppress some unwanted sounds. Was planning to de-cat, remove the Y-resonator and replace the twin muffler setup with a single oval muffler with down tip but will only de-cat if ECU work is not required. Quote Share this post Link to post Share on other sites
camera doctor 25 Report post Posted April 3, 2013 Just push it off ..... Sorry ....... could not resist Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 3, 2013 Just push it off ..... Ha! So sick of cleaning my cat's grubby little paw prints off my car that I no longer park in our drive and leave the car in my office underground car park! Haven't found any conclusive evidence on Google that M52B28 has pre and post sensors but quite a few posts seem to allude to it having both so am assuming the de-cat procedure is more trouble than it's worth. Quote Share this post Link to post Share on other sites
*Glenn* 855 Report post Posted April 3, 2013 a '96 E39 may not have both pre cat & after cat What's your vin #- last 7 digits Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 3, 2013 a '96 E39 may not have both pre cat & after cat What's your vin #- last 7 digits Thanks Glenn. Vin # BV77217 Quote Share this post Link to post Share on other sites
*Glenn* 855 Report post Posted April 3, 2013 Your car has pre cat and after cat lambda probes Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 3, 2013 Your car has pre cat and after cat lambda probes Thanks Glenn. Makes my decision much easier then, far more trouble than it's worth, methinks. Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted April 3, 2013 (edited) you could have also stuck your head under the car julian. lol... i've read a few ppl having issues when they have deleted and had to revert back. the post cat sensors really just monitor emissions and the health of the cats. So technically who cares about them. However this will throw error codes. It's the pre cat sensors the car relies on to monitor the engine health and tune. Edited April 3, 2013 by M5V8 Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 3, 2013 you could have also stuck your head under the car julian. I did but don't have a decent jack and couldn't see a great deal... Doesn't help that I didn't really know what I was looking for! Quote Share this post Link to post Share on other sites
westy 614 Report post Posted April 4, 2013 I did but don't have a decent jack and couldn't see a great deal... Doesn't help that I didn't really know what I was looking for! Something screwed into the exhaust, after the cat, with a cable coming out of it ha. Had a '97 NZ 328 without and a 2000 SA 328 without. A bit hit an' miss. Is yours a Jap? Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 4, 2013 Something screwed into the exhaust, after the cat, with a cable coming out of it ha. Had a '97 NZ 328 without and a 2000 SA 328 without. A bit hit an' miss. Is yours a Jap? Singaporean originally, I believe. Given up on the de-cat. Seems a bit much fuss. Quote Share this post Link to post Share on other sites
M5V8 337 Report post Posted April 4, 2013 http://chrisparente.com/2011/09/12/replaci...s-on-an-e39-m5/ with pictures. I've been looking to change the front o2 sensors if my MAF replacement doesn't fix my problem... They literally should be plugged in before and after the cats. Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 4, 2013 http://chrisparente.com/2011/09/12/replaci...s-on-an-e39-m5/ with pictures. I've been looking to change the front o2 sensors if my MAF replacement doesn't fix my problem... They literally should be plugged in before and after the cats. Looks easy... I wonder if it's the same on my 528i. Will try and lift it up somewhere over the weekend and take a proper ganders. Quote Share this post Link to post Share on other sites
hybrid 1044 Report post Posted April 4, 2013 The DME needs to have the correct software loaded to run without cats. Mapping isn't going to solve it as the actual program needs input from the sensors to work properly. Otherwise it will just revert back to a fail safe map and your car will just run rich. A bodge way around it is tuning the fail safe map. However it doesnt account for pressure changes or temperature. Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 4, 2013 De catted my 96 528 and added headers and had no problems mine only had O2 sensors ahead of the cats Pays to check, early N Z new cars were cat Ready but not always Cat enabled despite having cats fitted Now you're confusing me! What do you mean by 'cat enabled'? Surely if they're fitted they just do what they're meant to. Do you mean that some early 528s had cats but no post sensors? If so, I think Glenn's already ruled that after checking my VIN. Quote Share this post Link to post Share on other sites
kiwi535 538 Report post Posted April 4, 2013 just you cant re install the "post cat" probes? Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 4, 2013 The DME needs to have the correct software loaded to run without cats. Mapping isn't going to solve it as the actual program needs input from the sensors to work properly. Otherwise it will just revert back to a fail safe map and your car will just run rich. A bodge way around it is tuning the fail safe map. However it doesnt account for pressure changes or temperature. Have seen some online threads talking about post O2 sensor sims but that also sounds like a lot of hassle (and cost) for relatively low reward (6-10hp). Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 12, 2013 New muffler and pipe work. Also discovered there are no post-cat sensors.... Goodbye cats hello a few extra horses! Quote Share this post Link to post Share on other sites
*Glenn* 855 Report post Posted April 12, 2013 I even checked with BMW and they confirmed pre & post cat sensors....just goes to show a visual check will tell all. Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 12, 2013 I even checked with BMW and they confirmed pre & post cat sensors....just goes to show a visual check will tell all. I know and I appreciate the help but you're right, didn't know for sure until the car was up on the hoist! Quote Share this post Link to post Share on other sites
jeffbebe 1560 Report post Posted April 13, 2013 Cats were clogged. Feels like a different car now. No idea if there's more power but definitely a lot more acceleration lower down the gears. Sounds pretty good too. A bit whiney at high RPMs but I've been assured that will disappear after a couple of hundred kms and a bit of carbon! Quote Share this post Link to post Share on other sites
Ahmedsinc 414 Report post Posted April 14, 2013 So did you replace the cats with resonators / cans or just go for straight pipe? Am thinking about doing this at the same time as the manual conversion is done. Looks like it's still got the original ones ex factory, and after 170,000 ks I reckon they're doing more harm than good Am a little concerned about excessive noise if I just use pipe Quote Share this post Link to post Share on other sites
