Driftit 1964 Report post Posted January 29, 2010 I have a 1997 540. Just wondering if I am able to remove the cats but leave the rest of the exhaust system. Non Vanons M62B44. Quote Share this post Link to post Share on other sites
*Glenn* 854 Report post Posted January 29, 2010 Pre 1998 shouldn't be a problem. If it has pre cat & after cat oxygen sensors... you cant Quote Share this post Link to post Share on other sites
Driftit 1964 Report post Posted January 29, 2010 Ok will biff it up on the hoist and check the 02 sensors. Rays GT1 scan said the Cats and O2 sensors are ageing or something. I can't remember the exact message. Quote Share this post Link to post Share on other sites
Greg111 13 Report post Posted January 29, 2010 "Aging" is the typical message you would get. Quote Share this post Link to post Share on other sites
charles28 117 Report post Posted January 29, 2010 I have a 1997 540. Just wondering if I am able to remove the cats but leave the rest of the exhaust system. Non Vanons M62B44. I wouldn't do it if you have a light coloured car, as you end up with black crap from the exhaust all over the back of the car with no cats. Quote Share this post Link to post Share on other sites
*Glenn* 854 Report post Posted January 29, 2010 I wouldn't do it if you have a light coloured car, as you end up with black crap from the exhaust all over the back of the car with no cats. ??? Quote Share this post Link to post Share on other sites
hotwire 352 Report post Posted January 29, 2010 ?????? Ditto & look at Dan's profile - think I see Black 540 Quote Share this post Link to post Share on other sites
soarer260@hotmail.com 0 Report post Posted January 29, 2010 (edited) I would advise against this personally... If you do it, you would need some decent resonators in place after taking them out, otherwise it will sound somewhat trashy/tinny up top. Edited January 29, 2010 by Mike-E34 Quote Share this post Link to post Share on other sites
JFry 1 Report post Posted January 29, 2010 If you do it, you would need some decent resonators in place after taking them out, otherwise it will sound somewhat trashy/tinny up top.M60 V8s without cats sound awesome, main reason for owning a V8 would be to hear that noise.....They sound awesome at 6000rpm aswell. Quote Share this post Link to post Share on other sites
charles28 117 Report post Posted January 29, 2010 (edited) ??? LOL I failed to look at the profile. All i know is that every car i've had without cat converter has had an annoying amount of black crap end up all over the back bumper (noticable on Light Coloured cars), but in this case I don't think its going to be a problem. This happened on all the cars i've owned (without cats), including my current white E30 325i, which was factory non cat version. These were not all old cars like my E30 either, some were low km's year 2000 + models. My mechanic mate claims its due to NZ"s crap fuel.. I think he's right too, as when I had AVGAS in the car for one tank fill I had no black carbon crap on the back bumper . (I wash it off often, this picture depicts 1 weeks driving). Edited January 29, 2010 by Charles28 Quote Share this post Link to post Share on other sites
*Glenn* 854 Report post Posted January 29, 2010 LOL I failed to look at the profile. All i know is that every car i've had without cat converter has had an annoying amount of black crap end up all over the back bumper (noticable on Light Coloured cars), but in this case I don't think its going to be a problem. This happened on all the cars i've owned (without cats), including my current white E30 325i, which was factory non cat version. These were not all old cars like my E30 either, some were low km's year 2000 + models. My mechanic mate claims its due to NZ"s crap fuel.. I think he's right too, as when I had AVGAS in the car for one tank fill I had no black carbon crap on the back bumper . (I wash it off often, this picture depicts 1 weeks driving). That looks more like running too rich or the engine is burning oil Quote Share this post Link to post Share on other sites
Greg111 13 Report post Posted January 29, 2010 I know for a fact that mine runs way too rich, (due to blowing the odd flame) looks like that after a few days of spirited driving, doesn't use any oil. Quote Share this post Link to post Share on other sites
soarer260@hotmail.com 0 Report post Posted January 30, 2010 M60 V8s without cats sound awesome, main reason for owning a V8 would be to hear that noise..... They sound awesome at 6000rpm aswell. Not with the stock rear mufflers and no cats..... The entire system works as one to keep quiet. You need a full system if you take the cats out and dont put resonators back in. Otherwise bring on the Rattly rear muffler racket. Quote Share this post Link to post Share on other sites
JFry 1 Report post Posted January 30, 2010 Not with the stock rear mufflers and no cats..... The entire system works as one to keep quiet. You need a full system if you take the cats out and dont put resonators back in. Otherwise bring on the Rattly rear muffler racket. I'd have to disagree. Have been for a ride in two e39s (one 535, one 540) that had straight pipes instead of the cats and stock everything else, and they seemed to be fine? Quote Share this post Link to post Share on other sites
soarer260@hotmail.com 0 Report post Posted January 30, 2010 (edited) I'd have to disagree. Have been for a ride in two e39s (one 535, one 540) that had straight pipes instead of the cats and stock everything else, and they seemed to be fine? Interesting. Well on my E34 it ended up being the case, when I think about it, it was not bad, but at certain rev points the resonance would rattle the mufflers and create a bit of a nasty noise. Not to my liking! In saying that, I believe the later model E39 exhausts are much better than the older noiser E34 types so what you say is probably quite true. Edited January 30, 2010 by Mike-E34 Quote Share this post Link to post Share on other sites
andrewm 236 Report post Posted February 3, 2010 My jan build date e39 540i has been decat'd and had the airflow meter done at the same time, havent noticed any issues with the noise it makes but then i dont have anything to compare it to. Quote Share this post Link to post Share on other sites
hotwire 352 Report post Posted February 3, 2010 My jan build date e39 540i has been decat'd and had the airflow meter done at the same time, havent noticed any issues with the noise it makes but then i dont have anything to compare it to. From experience - they are noisier with straight pipe in place of cats. They tend to have a drone at certain revs too. As said in earlier post - entire system is designed accordingly. Cats, by nature of their makeup do act as a resonator. To remove cats & replace with fluted resonators virtually replicates the original noise level. Quote Share this post Link to post Share on other sites
