| From | Message |
EBL
Dodge Dakota
JOIN HERE
4/09/2004
11:15:48
|
 Subject: HELP! Failed low speed emissions test
IP: Logged
Message:
Today I brought my truck in for the new county emissions test. The test is divided into two parts, a high speed at 25mph and a low speed at 15mph. I passed the high speed but the low speed didn't go so well. I have a theory that the tester had a little too much fun with the truck before the test and heated up the motor a bit before the low speed test. When I got the truck back the truck was running warm.
Here are my results:
High Speed Results (25mph) RPM 1780
Pollutant----standard--------Reading------------
HC(PPM)------115-------------82---------Pass
CO(%)--------1.26------------.27--------Pass
CO2(%)-----------------------15.0--------------
02 (%)-----------------------.2----------------
NOx (PPM)-----706------------499--------Pass
Dilution------>6-------------15.3-------------
Low Speed Results (15mph) RPM 1391
Pollutant standard Reading
HC(PPM)------118-------------218--------Fail
CO (%)-------.99-------------.52--------Pass
CO2(%)-----------------------14.4----------
02 (%)------------------------.6-----------
NOx (PPM)-----771------------1473-------Fail
Dilution------>6-------------14.9-----------
I must admit that I didn't do a tuneup before the emissions test. I wanted to see exactly what was tested and what the standards were.
I will do a tuneup later today. Is there anything specifically that I should look at to improve low speed emissions? What would cause one to fail at low speed and pass at high speed where the engine would have less time to burn the combustion mixture?
It looks like all O2 is being burnt. I will clean the K&N to help a little more air into the combustion chaimber. One can't burn gas without air. The strange thing is, if I was not getting enough air, I wouldn't be able to pass the high speed test where the engine requires more air... Unless the higher engine temps were lowering the density of the air...
Any ideas?
|
opie
Dodge Dakota
JOIN HERE
4/09/2004
15:31:52
| RE: HELP! Failed low speed emissions test
IP: Logged
Message:
1. What mods do you have? If you have moved your IAT, bigger Throt. body, aftermarket exhaust, Autolite Plugs, removed 3rd cat, these may contribute to the failure.
2. what year / engine / mileage Dak. do you have?
3. Make sure the analysis was set up correctly too... did the guy have the fan running into your intake, etc.
4. A hotter spark could solve your problems. It would initiate a more complete combustion, and all it costs is $2 a plug.
|
ticats
Dodge Dakota
JOIN HERE
4/09/2004
19:40:23
| RE: HELP! Failed low speed emissions test
IP: Logged
Message:
Without information that opie asked, it's hard to make any specific suggestions. In general, to keep HC low, you need to make sure that all components of the ignition system (coil/plugs/dist. cap/rotor/plug wires) are in good operating order. Also include the pre-cat O2 sensor(s), clean air filter, clean injectors, working pcv valve. From personal experience, the following contribute to higher HC readings: none oem tbs, air intakes, tstats, cams and used oil and used oil filter. All should be put back to stock if possible.
To put odds in favour of passing, arrive as close to appointment time after a 45 minute or so drive at highway speeds, have gas tank at about 1/2 of a tank.
ticats, ontario, canada.
97 Dak CC Sport, 5.2L, 44RE, 4.56SG, race weight 4120 lb, 13.98 @ 99.85
|
uh
Dodge Dakota
JOIN HERE
4/09/2004
21:32:30
| RE: HELP! Failed low speed emissions test
IP: Logged
Message:
that hi NOX reading indicates your cat aint workin well. and the hi hydrocarbon also seams to indicate that the cat is a bit on the inefficiant side at low speed.
ticats, what the heck diff does the amount of gas in the tank mean to tialpipe readings?????? last I heard, none.
opie, due to the fact that you get the hottest spark at low speed due to the time that the coil has for saturation, I fail to see what your comments about "4. A hotter spark could solve your problems. It would initiate a more complete combustion," means. you get a cooler spark at hi rpm due to lack of time for the coil to develop energy saturation, not at low rpm.
|
Bowtie-ZL1
Dodge Dakota
JOIN HERE
4/09/2004
22:32:14
| RE: HELP! Failed low speed emissions test
IP: Logged
Message:
To me his readings indicate a lean burn condition.
the high NOx is dervied from to high a combustion temperature.
and the high Hc is casued by not enough fuel to propagate a stable flame front.
On a carb I would say to give the mixture screws a half a turn each to fatten it up and you would pass, but I have no idea on these computerized engines.
|
ticats
Dodge Dakota
JOIN HERE
4/09/2004
23:08:38
| RE: HELP! Failed low speed emissions test
IP: Logged
Message:
uh ... 1/2 tank is a tip that's given up in my neck of the woods ... lessens gas vapour pressure on the EVAP system (?) ... when clean air test started up here in 98, lot of the failures were due to leaky or not properly tighten gas caps ... when you're on the bubble, every little thing helps :-) ... btw, there's a very good product by CRC called Guaranteed To Pass which does amazing job lowering NOX readings (no one knows the exact reasons but it works) ... don't know if it's available in the States ... I used it once and got a 0 NOX reading :-)
ticats
|
uh
Dodge Dakota
JOIN HERE
4/11/2004
08:03:36
| RE: HELP! Failed low speed emissions test
IP: Logged
Message:
with a half tank you have a half tank of vapor, on a full one a lt less, so explain it to me. a leaky gas cap throws a code and that would have to fixed before the test right? as they check for the light? if that hi NOX is caused by a lean burn then runnin rich would make it so we would not need cats. the cats were added primarily, way back when first came out with them, to reduce NOX and SO2.
|
ticats
Dodge Dakota
JOIN HERE
4/11/2004
10:08:58
| RE: HELP! Failed low speed emissions test
IP: Logged
Message:
uh,
I can't speak for what each State looks for but I know that, in Indiana as well as in Ontario, all vehicles are required to have a properly sealed gas cap because, if not properly sealed, fuel vapour leaks from the fuel tank. In Ontario, they not only put a sniffer in the tail pipe but also have a portable HC sniffer (similar to ones used to sniff out naturaly gas or freon leaks) that they use around the filler cap and also under the hood. A small leak may not be sufficient to trigger a MIL but a sniffer will pick up fuel vapour going into the air from an improperly sealed gas cap which can result in the release of 30 gallons of fuel per year into the atmosphere. As for the half a tank, the likelihood of fuel vapour leakage is result of fuel pressure buildup in the tank not the volume. The smaller the empty gas tank volume, the greater the fuel vapour pressure and the greater the chance of fuel vapour being forced out an improperly sealed gas cap.
|
Bowtie-ZL1
Dodge Dakota
JOIN HERE
4/11/2004
11:17:39
| RE: HELP! Failed low speed emissions test
IP: Logged
Message:
uh said, "if that hi NOX is caused by a lean burn then runnin rich would make it so we would not need cats. the cats were added primarily, way back when first came out with them, to reduce NOX and SO2."
NOx is caused by high combustion temperature, the higher the temps, the easier it is for Nitrogen to bond with oxygen, thereby creating Oxides of Nitrogen (NOx).
A rich mixture will have a lower combustion temperature. Thereby limiting the creation of NOx. But creating more HC.
A lean mixture will have higher temperatures. There by creating more NOx. On a lean running engine you can burn pistons, valves, rings, and you can see the header pipes turn cherry red.
If a mixture is extremly lean, there is not enough fuel to propagate the flame front. There by creating hot spots in the combustion chamber. NOx is created in these hot spots. but because the flame can not travel through the chamber to burn everything, it results in higher HC due to incomplete combustion.
In the early seventies to combat the NOx issue the engineers resorted to the EGR valve to dilute the incoming charge with inert gases. This served to cool the comustion chamber during peak temperature without adversly effecting the flame front.
So to paraphrase---A normal Lean condition results in higher NOx.
A normal rich condition results in higher HC.
An extremly lean condition results in higher NOx and higher HC.
|
EBL
Dodge Dakota
JOIN HERE
4/11/2004
16:23:26
| RE: HELP! Failed low speed emissions test
IP: Logged
Message:
The truck is a 92, so it's OBD1 and only has 1 O2 sensor tht was replaced last year. It now has 152,800 miles on the 318. There are no mods to speak of. Just cat back and k&n. I opened up the intake a bit more by removing the restriction, so I have "ram air" of sorts. My gas cap passed inspection.
I went for a long (about 400 miles) drive this weekend to help clean out my injectors and combustion chambers. During much of my drive I was going through a heavy rain so the chambers are probably steam cleaned as well. Do you know of any other way to clean out the chambers of deposits? Higher octane gas perhaps?
I just ran my codes... I used the ignition system check and only received the 55 end of codes. I am going to assume that the EGR is functioning properly.
Any additional input? I appreciate all of your replies.
|
slow2dak
Dodge Dakota
JOIN HERE
4/11/2004
23:28:23
|  RE: HELP! Failed low speed emissions test
IP: Logged
Message:
just by looking at your specs from your inspection, it looks like your cat is not as efficient as it should be and possibly your EGR system is not functioning properly. ive been a state inspector for a while and the majority of the time its either the cat or the EGR that causes you to fail. i see it all the time.
Mike
02 4.7/45RFE RC Sport
3.55's and a SURE-GRIP
2 1/4" True Duals, Flowmaster Mufflers, no tailpipes or dumps
tps .701
relocated IAT
Adjustable ECT sensor
K & N drop in
Removed rubber flap
Adjustable LPS
Unplugged ABS Sensor (no speed limiter)
Interuppted TRD Link from PCM to TCM
All on street tires
Best 1/4: 15.20 @ 89.52 with single 3" flowmaster
No runs yet with new exhaust set-up
|
| | P 1 |
|
Post a reply to this message:
Username Registration: Optional
All visitors are allowed to post messages
|
