hi everyone @ HT,
ok here goes, im working on my friends 95 del sol, it had a D15b7 non vtec motor and he swaped it out with a ZC motor, motor runs great, idels great, zippy.
but when i took it in for smog it failed for high nox, so i replace cap, rotor,plugs, wires,fuel filter, new cat, and new o2 sensor.
but its still failing NOX by 500 ppm's.
so im wondering what's the fuel pressure suppose to be on a ZC compare to the D15b7??
i've never had this problem b4.
im only asking this cuz since i've replace everything already besides a new motor.
would the fuel pressure regulator be low for the ZC to where its cauzing a lean mixture to cause the nox????
i dont have to smog printout with me atm, its at my friends house.
*but will edit it once it get it.*
so its the fuel pressure regulator or alot of carbon build up im thinking is the cause of the nox.
i've never install a zc for a 1.5l b4, i've put zc's in place of the d16's and pass with no problems with my other honda's.
so im thinking the fuel pressure regulator is not the correct pressure.
*still have the 1.5l FPR in the del sol atm*
could this be my problem for nox???
HELP PLEASE........

 

nox are basically having cylinder temps that are to hot try running a higher octane fuel...maybe carbon builup.....what are the other readings???

 

if you have some type of air leak it will raise your nox levels. check your exhaust befor the cat for any cracks.

 

carbon CANT build up in the cylinders.
thats why the pistons have rings. to scrape all that carbon off. the only carbon that there is in a cylinder is that the VERY top of it. but thats not enough to do anything

 

ummm yes carbon can build up on top of the pistons and cause hot spots..but it would probably cause detonation and misfires....which would end up lowering tepms....smoke to many trees when i wrote that

 

i understand that but it idle's very smooth with no fluteration. sorry spelling sucks lol.
so i cant see it being a leak of n e kind.

yup had him run his tank almost dry and had him put 91 in it but its still failing but 500 ppm.

yes carbon can build up on the valves and top of the piston's to where it soaks up the fuel to cause a lean mixture. buts its a used attarco zc so carbon shouldnt be a problem.

i still think its in the fuel somewhere, any one know the fuel pressure specs for the D15b7 and the ZC. please post here :D.
thanks for the response HT

 

he said cylinder not piston
every one knows the carbon builds up on tops of pistons, valves, and in the chambers,

put good gas in it take it on the high way and beat the **** out of it.
always worked for me when clearing carbon, if its bad youll see it coming out of the exhust.
getting on your car every once in awhile is good for your car.

 

Best advice yet.. Check the exhaust manifold between the runners. If you get any exhaust dilution before the O2 sensor it is bad. The O2 sensor will be giving the wrong readings to the ecu. Before the cat is also bad as the cat will not be getting the proper oxygen to use.

Let's change the wording to combustion chamber. Carbon build-up can raise the Nox two ways. One is the build-up itself increasing the compression thus raising the burn temps.

And #2 is the carbon can ignite the mixture prematurely if there is a red hot carbon chunk in the chamber.

FYI, Nox is created from combustion temps above 2500 degrees.

I believe the fuel pressure is close to the same, so I am leaning toward timing, or exhaust leak. Where do you have the timing set on the ZC? Any one know what the timing spec on the ZC is? I know the a6 is 18 btdc and I am not sure if it is the same. I suggest checking this too. Advanced timing will raise Nox too.

 

my timing is at 16 btdc so its good
i really dont think its in timing due to the fact that it idle's great and response to throttle is great.

only thing i can say is it's still in the fuel somewhere.
fuel filter's been replace, so i'll look up the specs now.
thanks all for the response.

 

you can buy this stuff called sea foam and out it into your intake through a vacuume source. if there are any leaks in your exhaust a thick white smoke will come out of the leaking spot. if there is a leak before your catalytic converter it wont reduce nox like it should.

 

even better, run some water/alcohol through it. should knock any carbon off and help to lower the nox.

i thought all ZC's were 1.6s. maybe a difference in injector sizing?

 

thanks, i'll try the water trick and get back to all.

yes ZC are 1.6s, thats y i was asking about the fuel pressure regulator or injector size. cuz original motor was a D15b7.

FPR are the same pressure at:
Pressure should be: 280 - 330 kPa (2.8 - 3.3 kg/cm2, 40 - 47 psi)
*alldata* source of the spec.

 

same here, my nox where high when i smoged my 1.6 vtec with a dx ecu. solution was running a gs-r chipped ecu with not knock sensor more gas less temp.