removing cats from standard exhaust
Discussion
Blue smoke is turbo oil seals, i can't see how removing the cats which are downstream from the turbo could have any affect on the seals.
Granted the pressure drop across the turbo will be slightly higher when decatted, so the turbos will run more boost effectively, but i'd have expected that to be a negligable difference.
Matt
Granted the pressure drop across the turbo will be slightly higher when decatted, so the turbos will run more boost effectively, but i'd have expected that to be a negligable difference.
Matt
StreetDragster said:
Blue smoke is turbo oil seals, i can't see how removing the cats which are downstream from the turbo could have any affect on the seals.
Granted the pressure drop across the turbo will be slightly higher when decatted, so the turbos will run more boost effectively, but i'd have expected that to be a negligable difference.
Matt
I'm pretty sure turbo oil seal failure will produce White smoke, Blue smoke could be pretty much anything except that.Granted the pressure drop across the turbo will be slightly higher when decatted, so the turbos will run more boost effectively, but i'd have expected that to be a negligable difference.
Matt
I'm very interested in this post also as I'm experience ing a grumbling rattle in the exhaust but everything is secure.
Recently had rear turbo failure but turbo, actuator & hoses all good. Turbo Randomly started working again.
I wondered if the cat was breaking down & efectivy blocking the exhaust.
Thinking also remove cats or is it more cost effective to replace exhaust system.
Mt
Recently had rear turbo failure but turbo, actuator & hoses all good. Turbo Randomly started working again.
I wondered if the cat was breaking down & efectivy blocking the exhaust.
Thinking also remove cats or is it more cost effective to replace exhaust system.
Mt
StreetDragster said:
Adrian W said:
I'm pretty sure turbo oil seal failure will produce White smoke, Blue smoke could be pretty much anything except that.
Not much experiance, any time i've had 'oil seals' fail in the turbo it has produced blue smoke.Matt
the posters that are thinking of removing the cats, putting them back on for the MOT is a pain
verba1 said:
i was informed that reducing the back pressure ie cats out could cause the oil seals to leak and present this problem but was checking to see if anyone has had this
Skip at Bespoke said the same thing when a couple of us were enquiring about the possibility of having the Roush exhaust recently.Adrian W said:
What colour do you call this?
Wow thats quite a failure! All the oil seal failures i have had have been highlighted by a puff of smoke on start up, and a small puff of smoke when coming off boost, both clearly blue.Your photo does look blue in the smoke that has subsided a bit, but the stuff near the car is white, no idea.
Matt
I believe that you are both right.
Proper turbo oil seal failure dumps oil into the red hot exhaust and vaporises giving white smoke.
And yes, there is an oil seal - just not the kind of "seal" you normally think of, but more like a piston ring in a groove.
Back pressure in the exhaust helps it to seal, so when it starts to wear a low back pressure system will allow it to leak more easily.
When they do start to leak, you get a little bit of oil dripping out when cold which quickly burns off as the exhaust heats up from cold - giving a bit of blue smoke that fairly quickly clears. As the wear gets worse it then starts to also occur at idle (when back pressure it at it's lowest.
My understanding anyway
Proper turbo oil seal failure dumps oil into the red hot exhaust and vaporises giving white smoke.
And yes, there is an oil seal - just not the kind of "seal" you normally think of, but more like a piston ring in a groove.
Back pressure in the exhaust helps it to seal, so when it starts to wear a low back pressure system will allow it to leak more easily.
When they do start to leak, you get a little bit of oil dripping out when cold which quickly burns off as the exhaust heats up from cold - giving a bit of blue smoke that fairly quickly clears. As the wear gets worse it then starts to also occur at idle (when back pressure it at it's lowest.
My understanding anyway
StreetDragster said:
Wow thats quite a failure! All the oil seal failures i have had have been highlighted by a puff of smoke on start up, and a small puff of smoke when coming off boost, both clearly blue.
Your photo does look blue in the smoke that has subsided a bit, but the stuff near the car is white, no idea.
Matt
They way my engine is set up makes the turbos a bit of a consumable.Your photo does look blue in the smoke that has subsided a bit, but the stuff near the car is white, no idea.
Matt
Bart 124 said:
Mine is running without CATs but not a standard exhaust.
The previous owner simply advised to 'get her hot' before the MOT. Not sure that's the best tactic but short of buying a new system then that's what i'll be doing.
Doesn't matter how hot you get it. If there are no cats then that's an automatic MOT fail no matter what the emmissions readings are, unless you have a friendly tester! The previous owner simply advised to 'get her hot' before the MOT. Not sure that's the best tactic but short of buying a new system then that's what i'll be doing.
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