guys during my major, one of my cats was found to have had a "large" hole burnt through. a decision was made to replace the cats with "test pipes". i can confirm that (with the central muffler still in place) that the car goes significantly better. sounds better too at idle, but it is still too quiet. no issues with alarms.
If you remove that center muffler which is much bigger on the 456 than the one on the 550/575 you will get a much higher sound at high revs than with. At idle is about the same just slightly more. After spending about 10.000 usd on 456 exhaust I suggest you run components from the same company all the way from the engine and back because everything have to be made in harmony to each other to get a good end result for all running conditions.
Hi guys, This is an old thread I know, but surprisingly I could not find much about this subject with any searches. I have a problem. There may be different solutions to it, so I am trying to figure out which one would be best in the long run. 1) The cats have been removed form my car in the past. I have no idea when, perhaps already in Japan, or in Poland before/after the car had been first time registered in the EU about 2011. In 2013 the car was successfully registered in Germany (and thus had passed a TÜV inspection) and I had it serviced (belts etc.) at the official dealer in Frankfurt, Germany in 2015 and they had it again inspected by TÜV for me, no problems reported (well except the RHD headlamps, which they replaced with new LHD headlamps (about €1600,- eur) and the front suspension joints, which were also replaced with original parts. In 2018 I had it again serviced, this time at a (fchat) recommended independent service in Frankfurt. Great service IMO, and this time the manager of that company informed me that my car does not have cats anymore, although it clearly had had them from the factory. I asked if that was a problem and he said, not really, just a surprise and something I should know. I thanked him and they had the car pass again the German TÜV. The car runs great, but especially after a cold start the exhaust does smell fuel and has also an odd smell. (NOt sure what it is) Once warmed up it's fine, or so I thought. Mileage is great and it does not seem to have any cooling issues even in hot weather in Southern France or in the thin air and high elevations in Switzerland. 2) Finally after owning the car for almost six years and enjoying it very much I declared and had it taxed in Finland, with all the paperwork I went to get it inspected and registered in Finland and everything else went well, all the little problems had been fixed during the years and most recently the rear suspension had all the bushes replaced, the front frame was straightened (jacking abuse) and all wheel angles were adjusted and the car drives great, BUT it failed the emission test. All other values were fine and the fact it does not have cats would have been ok as well, due to age etc BUT the carbon monoxide values were too high! Over here the highest values accepted are 0.5 CO at idle and 0.3 at higher revs. now the car, after several attempts showed at best 0.76-0.78 CO at idle and 0.56-0.64 at higher revs. :-o The amount of HC and also CO2 and NOX was all fine and relatively low, oh well the CO2 is obviously high, but not a problem, only the CO value was above the allowed limits. So should I now: a) buy some second hand used cats and have them refurbished? (someone who knows how to weld this stuff replace the original cat with a high flow replacement cat at €200,- euro each?) Doesn't look like this would a problem, I guess so many 456's and 550's have had their cats removed so there are plenty of these for sale. Or would that just bring me new problems, like the cats overheating, getting all kinds of CEL's etc? b) have someone "tune" the car so I could pass the test and then just put everything back? Is that even possible with the two Bosch Motronic 2.7's? I can see form the spare parts book that there were two different cats for ROW and USA/CND/AUS/CH. RH side part nr. 161396 and part nr. 154355 (R.H. CATALYST USA, CDN, CH, AUS) and LH side part nr. 161397 and part nr. 154360 (USA, CDN, AUS, CH). Were the Motronic 2.7's the same and it would just adjust according what happened to the exhaust after the exhaust headers? Or are the Motronic 2.7's set differently already form the factory depending if they had the regular cat, an USA/CND/AUS(CH cat or no cat at all? So I am wondering if there is a permanent solution without buying new cats (about $3000 / €2400 each) or second hand (€300-€600,- eur plus cost of refurbishing them with Turbotech or some other 3rd party cats) or should I just accept that the engine needs to be retuned (detuned?) for an emission test and then returned to "normal"? I think I remember some friends in California needing to tune and adjust their timing and carbs for an emission test, and once passed they usually retune for a slightly richer mixture (to avoid risks of overheating and burning pistons) on their "smog" era E-types. Over here I would need to have the emisssions test every year until the car is 30 years old (five years from now) when it could be registered as a historic vehicle and inspection would be only every fourth year, but if anyone has been down this same road, I would appreciate some hints on what would be easiest for now. I will keep my eyes open for cheap second hand cats for sure, as I know they can be refurbished so they work and possibly also flow better than the original ones. There's a friend with an RHD->LHD converted Nissan GTR (R32 with an R34 engine) with seriously upgraded turbo and street legal with a custom exhaust and a modern high flow cat, so I will be asking him also about the CO emissions and what could be done to the exhaust to fix the issue. I think I can manage everything but buying the original spare parts cats. Cheers!
My cats were removed and I have had problems with flashing CEL and SDL signals ever since. New O2 sensors, thermocouples, marketed "bypassing" parts and many prayers have yet to eliminate the warning lights. The car runs perfectly so I have reluctantly accepted the dash annoyance as being the result of a hard, permanent ECU set. I have wondered, as you questioned, if the O2 sensors in non-cat Canadian cars would be accepted by the Motronic 2.7 settings in my U.S. car? Good luck with your situation.
Hi Pekka. sorry to read your frustration. to change the cats is quite a few houres of work and to take them on and off every time you have your annual inspection does not make sence. When I bought my 456M in 2009, it did not have cats, and the SLOW DOWN was more or less always on if I ran under 200 kph.!! It had the original mufflers and also the original center muffler. After lots of experimentation and testdriving a 1995 456 (non-M), I decided to copy his set-up as the sound in his car was much better. That was original catalyzers, Stebro «X-pipe» (actually an oval 20 cm long mid pipe where the exhaust meet for 20 cms. and no mufflers at all at the rear. I got the Y-tips from Stebro also. That car had a glorious sound in all conditions! No drone either. So just two original catalyzers and no mufflers at all! And the slow down also dissappeared! I have some videos of that 1995 456 somewhere. The strange thing is that that car had a slightly better sounding exhaust than mine with the same set-up and I think it has to do with the different firing order of mye newer M engine!
Hi Erik, No problem, I am happy otherwise, it's just that currently the weather isn't very supportive for driving the car anywhere, like a workshop or the inspection. I was thinking of getting those non-cat O2 sensors (lambdas) anyways, as the ones I found don't cost much. But then I don't have much more to analyze it than my nose. But if I can, I will try to get some tests done and report back, of course. I have pretty much the opposite, all original mufflers and pipes but no cats, just straight pipes with the O2 and heat sensors. Happy with the sound etc but I did have a gut feeling that maybe the rear silencers shouldn't get that hot (and heat the trunk like they do) so there may have been ECU issues regarding that normally the cats should get quite hot quickly after a cold start in order for them to work correctly and as my car had no cats, the heat went elsewhere. I'll most likely also buy the cheapest used old cats I can find so I can have someone replace the inside with some moderns high flow cat. If that works it would be a long term solution, but now I would very much to able to modify the setup so I just could pass the emission test at least once, so I could get normal plates on the car. Oh well, it's just a hobby. Cheers!
Ok. I would never try to open the cats to change the inside. Too much risk for not getting it back together. The body of the cat is made to fit the car, but a universal cat will be very difficult to fit ito that original cat! The slightest imperfection in alignment will make serious trouble when you install the rest of the system. In eBay.de there is a guy advertizing 550 sports cats at a more reasonable price. He might have 456 sport cats aswell. Or the 550 might fit too? Hard to test without having it under the car. I want to the off the cats on my 550. Nothing like an old school V12 Ferrari sound!
Hi Erik, Thanks, I didn’t mean “myself”, I meant by someone who knows this stuff. It’s been a problem also on the 1993-1997 Jaguar and Daimler V12’s. One needs to contruct a jig and welding and the heatshields need to be perfect as otherwise it would start a fire. If I find another solution I will post here. i’ll see first if there’s any chance to pass the emission test by tuning and changing the lambdas. Probably not, but if I put some cats back I’m going to have to unmount and remount the O2 and heat sensors anyways. Thanks for the support! Cheers!
Image Unavailable, Please Login Hi all, Ok, I have the downpipes without cats out. It says “TUBI” on the flanges. I am now waiting for aftermarket cats and new seals etc. I think I will do a lock and swap for the timing belts while I wait. Cheers!
Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Hi all, Some progress, I would have a lot of pics and stuff to tell, but for now only the good news. I bought two new repro cats (BM) from UK via ebay, got them on Tuesday and today, Thursday I passed the emission test and was able to get the car (finally) registered over here in Finland. Cheers! Ps. I did a belt and tensioner renewal, timing check etc service and hope the next 5 years will be smooth, 106.000kms now on the odometer.
Hi, Thanks. Sound? Well it was a bit quieter than with the Tubi straight pipes, sans cats. Obviously. Powerwise hard to say, it was -6C so I wasn’t pushing and the instructions for the cats said at least 9 miles of constant driving or running at high idle to get them going. I think they work ok as emissions was good, CO at idle was down to 0.32 from 0.78-0.82 and down to 0.21 at higher revs from ca 0.58-0.62. I think the basic idle exhaust sound is now softer but has a nice rumble. Cheers! (from Zermatt)
