Nissan Navara STX550 blowing black smoke

[spiezzy]

hi to all have been with this site for a while now just reading and getting some tips from you guys this is my first post .
about 5 months ago I purchased a second hand 2011 Nissan Navara STX550 V6 Turbo Diesel it has been a great vehicle tonnes of grunt and very comfortable it has 168.000 KLM on the clock but runs very smooth and its always blown a bit of black smoke when floored under load .
I took it to the Dyno tune place to put it on the dyno the report came back with it being normal in power and toque but he said it was blowing black smoke when they revved it up on the machine and was not quite sure what the problem would be as if it was injectors it would show as a lose of power ,
the car is fitted with a forefront industries intercooler and hard pipe conversion on the hot side of turbo (if that makes sense ) I noticed a little oil coming from both fittings with have the ring style push on fittings one at the turbo end and one on the intercooler end both have a leak .
there are no indications of warning lights coming on or anything like that as I mentioned the car runs great it uses a little oil around 100 - 150 mm every couple of thousand KLM and the oil does not look in bad condition have been doing oil changes every 5000klm the other thing I forgot to mention it does have a bit of blow by it had a catch can fitted by the previous owner but just want to get to the bottom of the black smoke bit oh and fuel consumption is between 9.8 to 10,2 per 100klm any advice would be greatly appreciated thanks in advance
cheers Pete

 

[bods]

Black smoke means excess fuel for the amount of air present (also called "running rich"). I have heard different rumours including the quality of the fuel in Australia leading to black smoke in diesels.

If it isn't producing smoke while you are driving, I wouldn't be too concerned. If it gives a big puff when you stand on it but goes away when at cruising speed I wouldn't be worried about it.

 

[spiezzy]

Thanks Bods for the reply yep whilst driving under normal conditions it does not do it just when you are going up a hill and you put your foot down it hesitates for a spit second and drops down a gear (I would say its in 6th or 7th )it lets out a puff for a couple of seconds and once up to speed it stops I was a little worried it might be injector issues $$$$$$$$$ but there seems to be no loss of power and when it drops down gear it takes off like a rocket
cheers Pete

 

[Old.Tony]

As above.

If there's any oil seeping from any join or component between the turbocharger and the intake manifold the boost pressure is being lost. The MAFS (which sits before the turbocharger) is measuring an airflow that SHOULD be reaching the cylinders and adjusts the fuel level appropriately. Boost leak means the measured air is going elsewhere which means not as much air in the cylinder hence too rich and you get the black smoke as bods says.

Power may actually be marginally affected. If you dyno test it again after repairing the leaks (under the same atmospheric conditions - temp, humidity and barometric pressure) you should get a slightly better result (but it may only be slight).

 

[spiezzy]

Thank you Old Tony your words of wisdom are very much appreciated I will get onto those seals on that hard pipe and check the cool side of the intercooler as well looking at it there is not a lot of room down there very tight on the cold side but the seals on the hot side where the Forefront Industries hard pipe conversion is much easier to get to and re new the seals where there is noticeably oil leaking out many thanks again guys
cheers Pete

 

[spiezzy]

Hi everyone well installed the new seals in the intercooler Forefront Industries hard pipe conversion today and found in the connection down near the intercooler someone had put a heap of silicone in the joint instead of changing the seal O rings so I cleaned it all off and put the new sales on both ends (they were totally flat on one side ) and cleaned the air filter box and cleaned the oil up and put it all back together fired her up and it even sounded different went for a drive and there was a noticeable difference in power and the turbo spooled up better drove it for a while when i got back home i checked the joints and no oil still nice and clean (yahoo).
I noticed much less smoke puffing out the back when floored maybe 70% less I am just wondering where the silicone was there was a mess there and maybe some has made it down to the intercooler when they did it could this cause a blockage ? in the intercooler and that it why I am still seeing a little smoke still ?
many thanks for your help guys big improvement
cheers Pete

 

[Old.Tony]

If you suspect the intercooler has a blockage it'll probably just sit in the 'hot' (inlet) side at the bottom of the tank. You ought to be able to pick it out with long tweezers if it sticks to the cores. It's unlikely that a chunk of silicone will disintegrate so that's where it should be - if it's there.

 

[spiezzy]

Thanks Old Tony I checked it out and there was no blockage the Intercooler side of things is good now but today I noticed smoke still puffing a bit it is very black I had my wife follow me and she said when I hit a hill she noticed black smoke coming out the power is there but it seems to be before it drops down a gear it labours a little the she said thats when the smoke puffs out until the down gear engages when it is at say 100klm and just putting along there is no smoke .
what are the symptoms of crook injectors ? as I mentioned when I had dyno test done the graph looked good up around 170KW and about 545nm
any suggestions on what to check next
thank you so much for putting up with this would be great to solve it
cheers Pete

 

[Old.Tony]

It really sounds like it's performing normally. I don't think your car has a DPF, so a bit of black smoke (as in, only blows black smoke for a short period then it's clear again) is quite normal. The big test will be in the fuel economy.

How's yours? You should be getting under 10LPHK. One member here reported getting just 12LPHK towing a 2T van across part of the top of Australia. I could only wish for economy like that!

If you haven't been measuring economy, here's how I do mine. I fill my tank to a point where I can just see the fuel in the tube and stop. After paying for it, I write the odometer and tripmeter on the receipt, I reset the tripmeter and drive off.

The tripmeter and litres shown on the receipt are all I need. Simple math involved - divide the tripmeter by 100 before you start (or in your head, so 534.7km becomes 5.347). Divide the litres by this number to get the number of litres per hundred km.

I think the 550 works this out for you, but I also think it's inaccurate. The best way to tell is to measure it yourself.

The calculation only works on standard tyres.

 

[spiezzy]

Thanks again Old Tony for that information yeh the fuel Econ in the car reads around 10.8 to 11,0 driving around here and only short trips for work and is quite hilly I have a alloy bull bar roof cage and canopy and draws in the back and is always loaded with tools and materials for work (builder) but if I go for a run up to gosford or longer I get it down to 9.6 but as you mentioned the accuracy of that gauge is questionable .
I have a 140ltr long range tank installed I filled it up and did a trip to Goodooga North west NSW approx 880klm I have driven up there on a full tank with plenty to spare I will try your method of calculating the fuel econ and yes I don't have a DPF on this model .
I have noticed that I use a little oil in between oil changes appox 250 to 300ml and when the engine is running and i remove the catch can lid there is a bit of fuming happening is this normal ?vehicle is heading towards 170.000 Klm
many thanks again for your help
cheers pete

 

[Old.Tony]

The catch can catches oil in the blow-by, a little fuming there is fine. Don't sweat on that.

Economy figures (for a loaded 550) sound just slightly on the high side of perfect.

Oil consumption between changes - no drama there, diesels lose it - and you catch it in the catch can (if it doesn't get all the way through and be combusted where you won't ever know about it).