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overfueling?

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i have a sneaky suspicion my car is over fueling or something else is a miss but how can i accurately tell?

I have a serious amount of black soot/**** on my rear bumper to the point that I'm having to polish it every 100 or so miles of driving. It was bad when I had the CAT but now its a lot worse.
car drives fine and has plenty of power, doesn't miss fire and only pops on up shifts when warm.

current mods: full 3" turbo back with decat, FMIC, EBC set to 0.7 bar, HKS air filter

I don't know this cars history in japan so something could have been changed map wise and then bits taken off before auction i don't know. Car has never failed an MOT so emissions have been sound. I think i have stock injectors but again haven't looked.

There is no smoke under acceleration (blue or white) and its not burning any oil. any help would be appreciated
 
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got any pics of the soot after lets say 100 miles?
it's normal that it turns black, they run rich (what isn't a bad thing)
i recon you have a white S15? hite some how attracts filth
it sounds pretty normal to me, had it on all my turbo cars

easiest way to make sure is just buy a AEM wideband, is around 140 pounds on ebay and one of the best thing you can buy IMO
great for really knowing what your car does fuel wise and if it is safe/something is going wrong
 
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whats the difference between a wide band setup to a normal air/fuel ratio gauge? as a gauge is about £60 but the AEm wide band is £140 ish
 
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A normal (narrow) band sensor is in every modern car and tells the car lean or rich, hi or low (bellow 14.7 and above 14.7)
The ecu uses this for stationary situation and cruising
This is good for emissions and fuel consumption
Once you ask the engine for power it discards any input from this sensor
A gauge as you describe is something complete useless IMO, let's you monitor this sensor

A wide band tells you exactly what you mixture does
So if you go wot and see a mixture of around 14 you know your fueling is off and you are better of checken it
If it goes to let say 10.5 you now you provably have a boost leak or something

Expensive standalone ecu's can be programed to use a wideband, normal ecu's don't cause that is to expensive :'(
 
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That does look like a bit much
Maybe vault in fuel pressure/vacuum hose?
Best way IMO is to get a wideband and know
 
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Yeah will invest in one next month, could a boost or exhaust leak cause this? It spools to 0.7 by about 5500 which should be normal I think
 
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Oh really!? Must admit it's started since I put the frount mount on. Will have to check with a smoke thingy now :( joy
 
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Ah yeah seen that vid on mcm, will get a couple of bungs turned up at work. Just hope I've not damaged the turbo. Done about 750 miles since the overhaul
 
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