Failed Emissions with the RB26.....

[Ramius83]

Ok, here's the dealio. I have an 94' R32 RB26DETT motor in my 1995 240sx. Stock engine/turbos. Using the carbon canister that many people eliminate. And using a 2001 Maxima catalytic converter (bolts up as it is the same bolt/flange pattern as the 240sx).

Went on Friday to get my emissions done in Georgia. I usually use a test-pipe all the time. I haven't run with that cat on there before. I installed it on that Friday morning and ran on it for a few hours before I tested. I went to test the sucker and I failed.

Test.................Reading..............AllowedHC ppm................11......................132CO %..................0.02....................0.73NOx ppm.............1337...................945RPM....................2866................3000 maxCO+CO2 %.........14.9..................6.0 min

I guess my questions for you all are:1) If the car is "somewhat" tuned correctly (ie timing, fuel, no boost/vacuum/exhaust leaks, good plugs, 93 oct. gas, etc), what can be causing the NOx to be off?2) Do you think that the "low" mileage Maxima cat is too blame and I should get a "decent" cat?3) Any tricks, while using the Maxima cat, I can do to pass with the 240sx in its current state?

I have already paid the $25 to go the first time, and since I failed, the next re-test is free. But if I fail again, I will have to pay another $25 for another test/re-test, which I am trying to prevent of-course.

As always, thanks guys......

[Joe]

its not the cat. the cat isnt a blame all for emissions failures. if you heated it up WELL its definatley not your problem as your other numbers are all fine.

NOX is your kicker. NOX is pretty much a measure of cylinder tempratures.

check your timing. check your spark plugs (gap, heat range, etc). your HC and CO numbers are wicked low so if i was in your shoes i would retard the timing a couple degrees and go back.

[rbsileighty]

Yeah... high temp combustion and high pressure => high Nox... since you're probably not boosting in the test and running a stock head gasket (ie not running a higher CR)... I'd agree with Kamin for the fix

For more advice you need a post dedicated to your current setup with a lot of pics

[Ramius83]

Ok, I know that the timing is at 20 degrees. So I'll turn it down a few degrees, maybe to 15 JUST to make sure lol. I'll do the re-test tomorrow after work. I checked the plugs, all are completely normal, BKR6E-11s, ie NGK Copper series. Anyways, thanks all for your help. I feel a little better that this may be a "cheap" fix versus having to order a cat, wait, flange it, etc.....

[Joe]

dont overadjust. you can swing the other way. i would go down to 17.

[sean8564]

I can help your emmissions hit me up .

[Ramius83]

Ok, I adjusted it to around 17ish. I will go tomorrow as soon as I get off of school. Something a little weird, the timing, before I adjusted it, was at 21ish degrees. I don't know how it slightly moved up on me as the CAS is TIGHT on there, and I routinely check it. Oh well, no problems with it at 21 degrees.

Sean: If I don't pass this re-test, I'll hit you up definitely.

[sean8564]

No problem

[Ramius83]

No problem

What exactly do you do Sean?

[Ramius83]

Ok, so there are two parts to the test, a 25mph test and a 15mph test. This time around, I retarded the timing back to 17ish degrees, and added a pound or two of fuel pressure. The car passes the 25mph test, but fails the 15mph test.

The gentleman at the emission station did not complete the test, so I wouldn't loose my $25. But, I don't get a printout of my results. So, I am shooting blind right now.

By just retarding the timing and adding a pound or two of fuel, I passed the 25mph test. So, what more can be done here? I have a set of NGK coppers in there, gapped to .8mm. So I am gonna pick up a new set, gap them to 1.1mm, and do an oil change and coolant flush just for the hay of it. Does this sound like it "may" persuade the car to pass this damn test? Let me know what you all think. Thanks again.

[sean8564]

Send me and email and i will tell you off board

[Joe]

guys lets keep the discussion on the board!what if someone else is having emissions problems. having an open forum to troubleshoot is the best idea possible. please.

and why did you add fuel pressure! you may have gone too far in the other direction like i warned you not to do haha.

[Ramius83]

Kamin: Talked to the head of the Nissan ProCap system here at my college (been a Nissan tech for over 18 years). He suggested adding a pound of fuel at idle to help bring down the cylinder temps a tad. Also, with that being said and adding in the effect of the decreased timing, "should" have passed me. But anyways, something is still not right here.

Any ideas at this point? Does it sound "good" that I should drop in fresh plugs gapped at 1.1mm, instead of my 0.8 gapped plugs? And maybe doing an oil change on her? I am getting a little depressed here lol, with not being able to figure this crap out. Getting desperate.

[krayton]

when your ready for drastic measures let me know. but keep trying until you run out of ways.

then i can tell you the easy pass. but it would be better if you could manage. just dont worry cause theres a way

[rbsileighty]

Depends on if you failed due to Nox or if your hydrocarbon count went up... higher hydrocarbon would make adding fuel a bad idea for obvious reasons. I think the larger gap plug will give you a more complete combustion at low engine speeds, so yes I do think it's a good idea.

What are your operating conditions at these 2 load levels (RPM, boost etc). If you are boosting that would hurt your Nox due to added pressure... consider diconnecting your actuator from the flapper valve so that the wastegates are always open => no boost.

Your temps couldn't be to bad at 15mph... i'd pull the added fuel back out, but that's just me.

Since your HC's weren't bad before... this probably isn't to big of a factor... but how fresh is your O2 sensor?

Your best bet for lowering the Nox would be if you could temp install some form of EGR on the car... then you'd probably be set...
Modified by rbsileighty at 5:12 PM 11/16/2005

[Ramius83]

Depends on if you failed due to Nox or if your hydrocarbon count went up... higher hydrocarbon would make adding fuel a bad idea for obvious reasons. I think the larger gap plug will give you a more complete combustion at low engine speeds, so yes I do think it's a good idea.

What are your operating conditions at these 2 load levels (RPM, boost etc). If you are boosting that would hurt your Nox due to added pressure... consider diconnecting your actuator from the flapper valve so that the wastegates are always open => no boost.

Your temps couldn't be to bad at 15mph... i'd pull the added fuel back out, but that's just me.

Since your HC's weren't bad before... this probably isn't to big of a factor... but how fresh is your O2 sensor?

Your best bet for lowering the Nox would be if you could temp install some form of EGR on the car... then you'd probably be set...

Modified by rbsileighty at 5:12 PM 11/16/2005

Ok, did some things, got the re-test done.

First, I retarded the timing back to 17ish degree, coming from 21 degrees.

Second, I changed out the 6-heat range NGK coppers to a 7-heat range NGK copper plug. Did an oil change, flushed coolant, and made sure the fuel was dead on.

Third, I added a pound of fuel from stock at idle. This was done to richen out the motor, so there is no detonation, which would result in higher cylinder temps.

I failed the 25mph test by reading a 947 for NOx. Allowed is 945. So I failed by 2 ppm. WOW.

But on the 15mph test, I failed with a 1518 for NOx, allowed is 1045 ppm. So I don't know what to do now.

The RB26 has no EGR stuff for the motor, it is "EGRless" from the factory. So yeah, don't know what to do there. There was 0 boost being created during the test to the best of my knowledge. So I don't think the boost is a factor here.

Well, I think I am gonna give up and "pay" my way for emissions. Sorry I can't go into more detail lol.......

Unless anyone else has an idea here, then I am done lol......

[Joe]

welp a gentle nudge didnt help

its time for drastic measures

open the gap a little more (.2mm). add a little more fuel (id do +2psi at idle). remove more timing. add a bottle of denatured alcohol to your tank.

its very hard to adjust emissions settings without a 3/5 gas analyzer. a shop could have this thing adjusted out in litteratlly minutes.

[Ramius83]

welp a gentle nudge didnt help

its time for drastic measures

open the gap a little more (.2mm). add a little more fuel (id do +2psi at idle). remove more timing. add a bottle of denatured alcohol to your tank.

its very hard to adjust emissions settings without a 3/5 gas analyzer. a shop could have this thing adjusted out in litteratlly minutes.

Regarding the gap of the plugs. The NGK 7-heat range plugs I threw in there are already at 1.1mm gap. You are saying that I should open them up a little more?

How much more timing do you recommend I remove? I am at high 16-low 17ish degrees of timing. Should I kick her back to around 14 maybe?

And the fuel pressure, I will add a little more, maybe another pound to a pound and a half.

And where abouts do I get a bottle of denaturated alcohol? And how much gas should I already have in the tank?

On the way to the emissions place, the car would not boost over 5 psi at its current setup. With doing what you are saying, will I even be able to drive the sucker with no probs lol ? Anyways, thanks again Kamin for your advice. I will try Friday morning before I return her to normal and go to the track Friday night (now 45ish degrees outside) versus 80 degrees during the summer when I ran my 12.06....

[Joe]

you know what i think it might just be time to try kraytons method.

ill let his stupid *** explain it to you. love ya bro.

[krayton]

you know what i think it might just be time to try kraytons method.

ill let his stupid *** explain it to you. love ya bro.

mmmhhhmmm, thank you.

step 1, pull over down street from testing zone.

step 2, pull injectors 1 and 6 off.

step 3, baby it to testing zone making sure to turn car off when not using

step 4, pass with 0s across the boards (manager has to come over and swipe his card cause the machine doesnt think your car is on)

step 5, pull into parking lot with employees looking at you funny

step 6, put injectors back on

step 7, drive home with a few WOT pulls to clean off those spark plugs

[rbsileighty]

Yeah... I knew it doesn't have EGR... which is why I said to add it... if you could add it that's a sure way to lower your NOX... maybe pull it from another car? Dunno... just a thought... would you really be detonating (sure way of adding NOX) at 15 and not 25?

Ehh... or you try Krayton's way

[Ramius83]

mmmhhhmmm, thank you.

step 1, pull over down street from testing zone.

step 2, pull injectors 1 and 6 off.

step 3, baby it to testing zone making sure to turn car off when not using

step 4, pass with 0s across the boards (manager has to come over and swipe his card cause the machine doesnt think your car is on)

step 5, pull into parking lot with employees looking at you funny

step 6, put injectors back on

step 7, drive home with a few WOT pulls to clean off those spark plugs

Love it man. I'll try it later next week. How bad does the engine run? Should I re-advance my timing back to stock and put the stock plugs in, or keep it retarded and keep the 7 heat range plugs in? Thanks for that, very humorous, but may possibly work. Thanks.

[krayton]

put it all back to stock settings. i did mine at stock.

oh yes, it will work

[Ramius83]

put it all back to stock settings. i did mine at stock.

oh yes, it will work

Does it run bad enough that they may know it while testing? Or does it run fine, just minus 2 cylinders and a little rough during idle? And skipping, backfiring, etc issues? Thanks again.

[krayton]

just runs rough is all. no backfires.

being that you got a 6 cylinder with 2 turbos in there, i dont think theyll care about you running rough.

try it out before u go. i gently let it come down with gas control after rolling and going to the idle test to make sure it didnt die. but your engine will figure it out and start compensating with more fuel.

[Dano]

Haha, Krayton that's awesome, ahahahaha, I can even picture doing all of that... now i'm set whenever KS decides to adopt emissions testing.

-Dan