Geting a stocker through Emissions

[Guest RON JONES]

I just failed Emissions.They have three diffrent tests.HC,NO,CO.The first two passed but the CO faied.Measued in %,my car has 5.22% CO and the limit is 3.27%.I'm going to give it a bacic Tune-up,Air filter,plugs maybe EGR valve,ect.Any tricks out there to help Me get it to Pass.I heard a couple of cans of dry gas helps,is this true?The car does smell like it is running a little rich.Its 77 280 FI.Any input would be greatly apreciated.

[Kevin Shasteen]

If the car hasnt had a tune up in awhile and is actually running "fair" then maybe the air filter, oil change w/filter, w/tune up (cap,rotor,plugs & plug wires) will be all that's needed; might as well rpl the fan belts while your at it...you never know(?).

 

Are you limited by how many test you can fail w/in a year or can you take as many as is needed to pass?

 

Also; check those vacuum lines (the large ones) all this aids to engine emis's. When I replaced all my vacuum lines I could tell the engine idled differently; so they do have an effect on the engine's efficiency.

 

Maybe a hotter spark (aftermarket coil) if nothing else works.

 

Kevin,

(Yea,Still an Inliner)

[Guest Anonymous]

Ron,

I had a 280-z that would not pass emissions at idle but if the rpms were raisd 2-300 rpms it would pass fine. I made some sort of adjustable stop (its been awhile) on the throttle linkage and would advance rpms for the inspection. It would idle at about 900rpms and pass with out problems. Good luck. Mark

 

[ May 05, 2001: Message edited by: Mark ]

[Guest RON JONES]

They did the test at rpm's.they put the car's rear tires on a set of rollers(kind of like a chassis dyno)and rev it up.Is there an o2 sensor,there must be,But I can't find it?thanks.

[John Scott]

Ron CO levels are almost exclusivly a function of the air/fuel ratio. The leaner you can run it the better for test purposes. If the fuel system is running too rich the timing will come into play, but only with minor changes. I always set my carb idle mixture just to where the idle starts to come down, then another 1/2 turn in. Also set timing down to a moderate point, 8-10 degrees. (NOx levels go up with timing). Way down from its usual 16-18BTDC. Runs like crap, but gets me through the test.

Greeley is starting its remote testing. They set up a van, similar to photo radar, and measure as you drive through. Claim to be as accurate as the dyno test. Two clean passes and they send you a wavier. I don't like it!!

JS

[SpeedRacer]

Interesting Ron - do you have the readings for all three?

 

HC - is unburned fuel (Hydrocarbon)

CO - is partially burned fuel (Carbon monoxide)

NOx - is caused by high combustion temp (Oxides of Nitrogen)

 

In general, high combustion temps tend to lower HC and CO2 but raise NOx. So a lean (but not to lean) mixture and advanced timing tend to lower HC and CO2 but raise NOx. Since and EGR valve allows up to 15% of the exhaust gas (considered to be inert) back into the intake mainfold it essentailly leans out the engine and reduces combustion temp thereby reducing NOx.

 

Sounds like you NOx number is OK so the EGR is probably working. I'd do the normal tuneup and filters, run the timing up and take it back through. BTW, replacing the O2 sensor wouldn't hurt anyway since the new ones (consider a Bosch) are much better that the original ones anyway.

 

Don't put gas in the car the day you are going to get it tested and make sure the Evaportive Canistor is purged. Run the car hard to make sure the Catalytic Converter is fully lit up just before you get it tested.

 

Good luck!

 

[ May 06, 2001: Message edited by: SpeedRacer ]

 

[ May 06, 2001: Message edited by: SpeedRacer ]

 

[ May 06, 2001: Message edited by: SpeedRacer ]

[Modern Motorsports Ltd]

Ron, your higher CO could be strictly due to needing a new air filter (or not just leaving your old one out for the test )if your other readings were good. Depending on your costs to test/number of tests allowed I might not do too much effort in tuning/parts. (I enjoy repeat test to see influences etc )

 

We set mine up on a scope in January and really tweaked it down....then I put my air filter back on to drive to the test station and forgot to remove it prior to testing and that one CO at idle almost failed me as a result....I had 3.81 and my limit was 3.90 I directly recall the CO/idle and that it can be directly related to your air intake/filter. Here's my other passing readings just for others info:

(Limit in brackets)

Driving:

HC ppm 4 (217)

CO % 0.47 (1.52)

NOx ppm 298 (2199)

 

Idle:

HC ppm 69 (342)

CO % 3.81 (3.90)

 

Anyone else needing to do emissions I kept all tuning/setup data (600 performer)for above 'pass' on my ZZ4 cammed 350 with no cats/evap cannister etc.

 

Idle was 1050, no vac. advance, 6 deg. total timing at this rpm (yes/tune was only for passing this test, at 750 that would actually be negative timing....).

[DavyZ]

Ron, a agree with Speedracer in getting the engine HOT before testing. A local shop where a friend of mine works says they can get most cars to pass, but they get the car engines HOT before they run it through. Also, there are chemicals from the autoparts stores that sell stuff that will help you pass--they guarantee it on the can. How do they back it up? Dunno. It think the brand is called "Outlaw" but I've never tested the stuff myself, so I'm not sure it works.

[Guest needwaymorespeed]

all the above posts are real good info ,if you want to make sure youll pass with a hign co or hc -run the gas tank down and dump a couple of bottle of water remover in youre tank-its alcahol-itll clean it right up!!

Works everytime-wont work on high nox though-make sure its the alcahol version-isopropylene alcahol if my memory serve right.

have puled 2 plug wires off of a v-8 before and it still passed-actually did this at the im certification center!! part of the training to be certified.

later

Curtis

[Guest RON JONES]

Thanks for the replys.The other Two numbers were real good.the HC reading was 122.1 and the limit is 453.0.And the NO reading was 200.7 with a limit of 2906.The car doesn't have a O2 sensor so I just Put a new air cleaner and plugs(both looked to be in need of replacement)NOW the timing,addvance or retard????I was told to retard the Timing at the track yesterday.But now I'm confused(whats new)and two difrent ways to go by the replys here?What do You guys think?

[Modern Motorsports Ltd]

Retarding your timing makes for a cleaner burn/less power but cleaner burn as emissions sniffers want. I've always had to drop my sbc back to near zero or even less initial timing. I'd suspect your OE Z would pass at stock setting (8 or 10 initial??) but 4 or 6 couldn't hurt your test at all IMO.

[Guest RON JONES]

I'm going to retard it for the test.I don't want to go back again.

[Guest needwaymorespeed]

yah get this

you retard youre timing-you burn less fuel in the combustion chamber-less power but youre emissions go down less hc at the tailpipe. why?

well because this allows youre engine to burn the fuel while its going out youre exhaust port and into youre exhaust manifolds and pipes then the good old cat burns the rest of it nuts huh!!

we only burn like 20-30 % of the fuel in the combustion chamber cant run the combustion temps higher cuzof nox and it would melt the engine down the japs are working on a ceramic engine to allow more efficient burning of fuel dont know what theyll do about nox though.

 

Curtis