I'm pretty sure that my fuel pressure was too low. I put it down to 25psi this time. When I passed before, everything else was the same, but fuel pressure was at 27psi. So I'm thinking that I'm going to drop my timing to 14-ish, (it's @ 16 now), & put the fuel pressure to 26-27psi. Can anyone assure me that I'm on the right track?

 

i dont know what your stock timing is but if its 12 then 14 sounds good. also i dont know what the other gasses read on the run, but if you have high nox then your probably runin lean. so with out seeing the other gasses i will say yea bump up the fuel.

 

Okay, so I must have been wrong. I bumped the fuel pressure up to 30psi & my NoX went up - WTF? My CO & HC are low as **** between .02-.05, & 029-048, respectively. I didn't change the timing because I wanted to see if I was right about the fuel pressure. I can drop my fuel pressure lower, but I'd like to get a solid second opinion on whether or not that will help. Any input is appreciated.

 

Up.

 

im getting high nox in my b16 crx. it was 3.1 with my spoon ecu, and i got it to 2.54 (max is 2.5 here). Im gonna try to run colder plugs and soak my injectors in injector cleaner. ill let u know how it turns out tomorrow.

 

Update:
I put my IAB valve body back in my IM & tested it today with the fuel pressure @ 32psi. This time it was much closer, (only about 100 over the limit), but I still failed. I'm going to up the fuel pressure some more for my next retest, but what other adjustments can I make to help? I have all stock internals except for a CTR intake cam. My timing is @ 16°, & my cam gears are straight up.
Would it help to;
Retard my exhaust cam?
Run colder plugs?
Adjust ignition timing - if so, which way?

 

I had a whole emissions fiasco a very short while back - just couldn't pass. Here's what I did to finally get through...

1) replaced the catalytic converter
2) Went to gas station after driving a little bit aggressively on the way out (not hard, just a little aggressive)
3) Put about 500mL of Methyl Hydrate in the tank (40L tank)
4) Tuned fuel pressure, with the car not running, by repeatedly priming the pump and resetting the pressure, to ~33psi on the B&M at the regulator (5psi under stock)
5) Pulled out the maximum amount of ignition timing - roughly 8 degrees total timing BTDC (before top dead center) at idle. Just retarded it as far as it would go!
6) Filled up on Chevron 92 octane
7) Revved the car for about a minute to about 4k rpm
8) Put front tires to 46 psi (35psi max pressure )
9) Revved in the waiting line again for about 2 mins
10) Drove in, passed with flying colours (some emissions are even under the average)

This is after failing with the new catalytic converter prior. So I put in the new cat, failed, then did the above and passed.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94gsr &raquo;</TD></TR><TR><TD CLASS="quote">
Adjust ignition timing - if so, which way?</TD></TR></TABLE>
Try retarding the timing. What year and model is it? Does the EGR system work properly? (If it has it.)

 

i just ran into the same problem, i retarded my timing and dropped the fuel pressure a little bit and ran a stock ls ecu, passed with ease, if you're not running your stock ecu then that will play a huge part but if you are then just try what i did and hopefully you'll have the same results

 

Im unfamiliar with Georgia's emissions laws...what kind of emissions test did you have to do??...Idle test??....2500 rpm test??...or a spin on the dyno test??...an unmodified car that has high NOX is usually related to the EGR system...its used to reduce NOX....however at idle the valve isnt suppose to open..get back to me and I might be able to throw in some more info for ya

 

retard the timing as much as you can before it starts to run like real crap.......say about 10-12deg BTDC and have it re-tested. it should pass then.

as for the fuel pressure leave it at the stock spec.

 

Before you test, run your car between 40mph-80mph for 80 seconds. Get your 02 sensor functioning.


With that CTR cam I'd use NGK's with a heat range of 7. (new ones!) Play with your exhaust cam some too like you said..

I bet you'll get there soon enough. Set fuel pressure to stock, which I believe is around 34-39 psi? (clueless on that one)... but keep it stock.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">what kind of emissions test did you have to do??...Idle test??....2500 rpm test??...or a spin on the dyno test??...an unmodified car that has high NOX is usually related to the EGR system</TD></TR></TABLE>
They do all three here & I don't have an EGR system.

 

The only way to accurately test for NOX is "loaded mode" testing which means a dyno. NOX is created in the combustion chamber when combustion chamber temperatures exceed 2500 degrees F. Advanced timing, lean mixture,high compression, and poor cooling system performance can all lead to high NOX emissions. For the average Joe, retarding the timing and richening the mixture can get the NOX to acceptable levels. Just don't go too rich, or the CO will start to exceed the limit. The fuel pressure should be at least 45 PSI with no vacuum to the regulator.

 

Now I'm getting pissed. I upped the fuel pressure by 7psi to the lowest stock point of 39 & dropped the timing to about 12°. My CO & HC went up, which was to be expected, but so did my NoX, by about 400 - DAMMIT! I guess it's time to see if my brand new O2 sensor has somehow gone bad...

 

Dude, try the things in my list... we do full load-testing for emissions also, steady-state driving on a 40km/h dyno. That's how I passed. I tried 8 times before passing.

 

Your cat may not be performing as it should. There is a reduction bed in the cat, and if it's not working, it will be tough to get the NOX below the limits.

 

Failed again. I put some Chevron additive in with new plugs, (with a slightly smaller gap than before), & kept the timing at about 12°. Everything went up again.

This all leads me to a few more questions;

What octane fuel would typically result in lower cylinder temps? With my timing so low, I can run 87 if it would help. It seems to me that 87 would lead to more of a temp spike than say, 92, but 92 would burn slower, possibly meaning higher temps when the exhaust valves open. Which way do I go?

Am I correct in thinking that tightening the LCA of my cams would help? It seems to me that dialing in a bunch of overlap would introduce some cooler, intake air into the exhaust stream. Any thoughts?

Would colder plugs help at all? Provided that they're not so cold as to foul, of course. It makes sense to me that a colder plug could help lower cylinder temps.

I passed last year with this CAT & I've only put about 200 miles on it since then. I'm determined to pass without buying a new one, especially since I'm only failing NoX.

Any help would be appreciated.



Modified by 94gsr at 11:46 AM 5/3/2003

 

Up.

 

High Nox almost definitely poinst at your egr system. I passed my test with 14btdc timing 89 octane. My nox was .20 for a max allowable of 2.50 every thing else was very low also. While I was testing I spoted an old friend of mine working at the emissions place and I talked to him about my bros car which was having nox problems. He said that most likely its the EGR system, dirty or blocked or something. That same day I compared my bros B16 to another one and noticed that my bros B16 didn't have an EGR system, someone took it of the intake and pluged the holes. True story, happened this week.

 

My car doesn't have an EGR system.

A secondary thought on my cam gear settings. If I were to widen the LCA, as opposed to tightening it as I was originally thinking, then advance both cams, there would be a good possiblity that the cylinders would retain some of the exhaust gasses from the previous combustion event, helping to cool things down on the next combustion event. Thoughts?

Anyone with feedback on the fuel octane, or any other opinions on spark plug choice?


Modified by 94gsr at 6:02 AM 5/4/2003

 

Are you sure your cat is good?

Sonny

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sonny &raquo;</TD></TR><TR><TD CLASS="quote">Are you sure your cat is good?
</TD></TR></TABLE>
Yep. I just put it on a couple weeks ago. It wasn't clogged at all & nothing rattled.

 

How old is it? Just because you can't see any visible defects doesn't mean that it is not past its prime. You probably don't wanna buy another one, but it is basically the last thing that you haven't touched.

Sonny

 

Well, if a CAT's not clogged & nothing's loose or broken inside, it does what it's designed to do. Given the fact that my CO & HC are damn-near nothing, it's obviously working. If those were a bit higher, then I'd see the CAT as a possibility. Either way, a CAT is not going to change the temperature inside my cylinders. A new one may better reduce NOx emissions, but I'm still going to have a temperature problem. So I'm looking to fix the problem as opposed to covering it up.

I widened the LCA by 4°, then advanced both cams by 2°. I also let the PCV valve vent to the atmosphere & plugged the hose that usually connects it to the IM. This all netted me my highest NOx reading yet - 28XX, putting me at more than 1700 over the limit. A new record for failure - hooray!

It would be great to hear some technical insight on how to lower in-cylinder temps... if anyone's out there.