Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: hotel21 on 15 November 2009, 23:12:22

Title: Why....
Post by: hotel21 on 15 November 2009, 23:12:22
.... would one exhaust pipe in the backbox be a nice grey colour and the other somewhat blacker, when the engine has new air/oil filters, plugs, fresh oil, new fuel filter etc....

Lambda?
Title: Re: Why....
Post by: CaptainZok on 15 November 2009, 23:15:53
Plug your box of tricks in and see what the live data says.
Title: Re: Why....
Post by: dbug on 15 November 2009, 23:16:00
Could be.

Also check state of spark plugs - could be ignition related!
Title: Re: Why....
Post by: hotel21 on 15 November 2009, 23:16:50
Quote
Plug your box of tricks in and see what the live data says.
Pretty well balanced, to be honest.  Nothing really out the ordinary.

Oh - and belt/tensioners replaced at York meet recently so all timed up nicely...
Title: Re: Why....
Post by: CaptainZok on 15 November 2009, 23:30:01
Quote
Quote
Plug your box of tricks in and see what the live data says.
Pretty well balanced, to be honest.  Nothing really out the ordinary.

Oh - and belt/tensioners replaced at York meet recently so all timed up nicely...

I would have thought if one bank was running richer the fuel trims would have been out of balance.
Stick a data snapshot up see if the clever ones can spot anything.
Title: Re: Why....
Post by: Andy H on 15 November 2009, 23:30:05
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.... would one exhaust pipe in the backbox be a nice grey colour and the other somewhat blacker, when the engine has new air/oil filters, plugs, fresh oil, new fuel filter etc....

Lambda?
Do you mean before the back box or do you mean the twin tailpipes out of the backbox?

Maybe very little exhaust gases actually pass through the clean tailpipe? (My thinking is that the exhaust gas from both banks gets mixed in the back box before reaching the tail pipes because if they were kept separate you would have two rasping 3 cylinder exhaust systems rather than one silky smooth 6 cylinder system)
Title: Re: Why....
Post by: ENFIELD_MV6 on 15 November 2009, 23:31:35
allways noticed it on cars with twin pipes out of the back, more so on bmw`s ????? dont know why
Title: Re: Why....
Post by: hotel21 on 15 November 2009, 23:36:17
Its the two pipes as the stick out the rear of the car.  **

One is distinctly darker inside than the other and has been since I got the car.  Was thinking timing initially, but no change since belt etc done.  Then thinking plugs but replaced all 6 a few weeks ago and no change after a couple of thou' miles.

Will revisit the car with a T2 sometime this week and recheck the values.

** edit to add, rear box and both centre pipes are new VX in my ownership as well...
Title: Re: Why....
Post by: ENFIELD_MV6 on 15 November 2009, 23:41:17
could it be one pipe is more central to the back box and the other pipe takes longer for the gasses to come through, notice mine on cold mornings that one smokes/condensations more than the other so could be with to do how the back box is made
Title: Re: Why....
Post by: CaptainZok on 15 November 2009, 23:43:06
Quote
Its the two pipes as the stick out the rear of the car.  **

One is distinctly darker inside than the other and has been since I got the car.  Was thinking timing initially, but no change since belt etc done.  Then thinking plugs but replaced all 6 a few weeks ago and no change after a couple of thou' miles.

Will revisit the car with a T2 sometime this week and recheck the values.

** edit to add, rear box and both centre pipes are new VX in my ownership as well...
One of the cats a bit more efficient than the other maybe?
Title: Re: Why....
Post by: Kevin Wood on 16 November 2009, 09:39:56
Not using any oil, I take it?

Was thinking it could be one bank burning a little?

Otherwise, as suggested, compare the fuel trims for the two banks.

Kevin
Title: Re: Why....
Post by: Elite Pete on 16 November 2009, 09:57:28
That thrashing you gave it trying to keep up with my little MX5 probably hasn't done it any good broocie  ;) ;D
Title: Re: Why....
Post by: Andy H on 16 November 2009, 10:39:12
Quote
Its the two pipes as the stick out the rear of the car.  **

One is distinctly darker inside than the other and has been since I got the car.  Was thinking timing initially, but no change since belt etc done.  Then thinking plugs but replaced all 6 a few weeks ago and no change after a couple of thou' miles.

Will revisit the car with a T2 sometime this week and recheck the values.

** edit to add, rear box and both centre pipes are new VX in my ownership as well...
If you press a rag up against one tailpipe does the pressure build up or does all the gas come out of the other pipe?

I think you are trying to fix a fault that doesn't exist......
Title: Re: Why....
Post by: Kevin Wood on 16 November 2009, 10:47:27
The back box has a pair of perforated pipes running straight through from front to back with wadding material surrounding them. Whilst gases from the two banks can mix in the back box, the majority will go straight through in the absence of any restriction IMHO.

Kevin
Title: Re: Why....
Post by: Andy H on 16 November 2009, 10:54:31
Quote
The back box has a pair of perforated pipes running straight through from front to back with wadding material surrounding them. Whilst gases from the two banks can mix in the back box, the majority will go straight through in the absence of any restriction IMHO.

Kevin
Good point, well made.

I only have a single tail pipe on mine so was trying to establish how much mixing was occurring between the twin tail pipes.
Title: Re: Why....
Post by: Big_Roger on 18 November 2009, 01:32:53
Hi,
Could you perhaps get a friendly MOT test garage to give you a readout on exhaust from each tail pipe for comparison ??

This then begs the question, does the MOT exhaust emmissions check expect a reading from both cylinder banks on "V" engined cars with twin exhaust systems, or come to that, any car with a split exhaust system.

Roger
Title: Re: Why....
Post by: davethediver on 18 November 2009, 01:39:44
Would think not as my A6 V6 failed on the emmissions on the left pipe but passed when tester shoved it up the other nostril!! Having said that they wern't that strict in all honesty so not sure on the Official line on emmisions :-X :-X
Title: Re: Why....
Post by: Kevin Wood on 18 November 2009, 09:23:21
MOT testers are supposed to take a reading from each exhaust and average them IIRC.

Kevin