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Discussion Starter #1
what air/fuel ratio do these cars run as stock .? id hazard a guess at lambda 1 (14.7-1) off boost and id say 12 ish -1 on boost. the only mod ive made is a y pipe but my car gets so much soot from unburned fuel on the back end it wont even wash off , ive been around tuned turbo,d cars for a long time and ive never seen anything like this . even my diesel daily doesn't suffer from this and that chucks a fair bit of smoke out when you boot it. id put money on the afr being down in single figures buy the economy im getting and amount of crap coming out of the back. then theres the power that's being thrown away. will a remap lean the afr out and get rid of this problem ?

I know waxing and ceramic coating will help keep the car clean but that's not getting to the root of the problem.
 

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I have the exact same problem, you don’t own a white car do you? I struggle like mad to get the back of it clean!

Be interested to hear whether a map or leaning out will help with this...


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Discussion Starter #3
yeah its white.... ill get to the bottom of this even if I have to take my wideband lambda kit off another car I have. I just thought one of the tuners might be able to add 2 pence.
 

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Please let me know when you find out. I’ve got an Octavia diesel that runs cleaner than my GTR currently


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My hunch is over fuelling but at the same time I’m not a tuner.

I have an ecutek Bluetooth module and I’ve gone through the settings on there and can’t see anything that stick out from the diagnostic either


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yeah its white.... ill get to the bottom of this even if I have to take my wideband lambda kit off another car I have. I just thought one of the tuners might be able to add 2 pence.


Did u ever find out what caused this?


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The AFR the car professes to control to is leaner than actual. So yeah, they run rich enough to soot up the arse. Nothing to worry about, as long as you wash her bum. A lot. :chuckle:
 

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They all run rich even at stock. And if you remove one set of cats that are in the y-pipe then there***8217;s one less ***8220;filter.***8221;

Go bigger turbos and injectors and fully decatted. Then you***8217;ll really see plumes of the black stuff that***8217;s for sure.

After having mine ceramic coated it***8217;s much easier to keep clean
 

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Discussion Starter #9
a bit of research tells me that the afr on the gtr is in the 11,s where as a n\a car will run lambda 1 14.7-1 . a tuner will usually map a turbo,d car to run around 12.5-1 which is a little richer than lambda 1 to keep combustion chamber and egt temps a bit cooler with the extra fuel. any richer than this causes poor fuel ecomomy, black smoke and even bore wear from all the extra fuel . I don't understand why Nissan didn't fit egt sensors in the exhaust manifold just before the turbo to allow you to see whats going on and lean the mixture out whilst still keeping the engine safe.
 
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