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Author
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Topic: Smog test... what does the "HC" stand for? NOW WITH NUMBERS
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94Blackout
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Member # 2541
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posted
 
 
I'm trying to get a car to pass smog, and the last test it failed, during the idle cycle the HC limit was 100 and the car hit 173. What does the HC stand for (my guess is hydro carbon? lol) and does anyone know what the causes of this level and how to fix?
[ January 22, 2005, 06:00 PM: Message edited by: 94Blackout ]
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87 5.0 LX: Exploded
94 Cobra: Totalled
94 GT Vert: Rear ended
98 Charged GT: Sold
65-67 2+2 Fastback: Someday...
Posts: 704 | From: San Jose, CA | Registered: Mar 2003
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jaybquick
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Member # 4286
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posted
HC stands for Hydro Carbons. It indicates a lean codition. What were your CO% CO2% NOX readings? Was this a dyno smog? What part of the test did it fail? What year mustang do you have, what mods, etc, or is it the one in your sig?
[ January 14, 2005, 08:59 AM: Message edited by: jaybquick ]
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91 Mustang GT ET: 11.92@115
66 Mustang ET: 11.43@119
01 Audi S4 ET: 10.8@131
05 Audi S4 ET: 11.9@116
08 Audi S5 ET: 11.9@118
Posts: 416 | From: Lathrop | Registered: Mar 2004
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94Blackout
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Member # 2541
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posted
Sorry, I need to edit my sig. These are the cars mods....
94 GT
Vortech S-trim supercharger, 8lbs
Trex fuel pump
30# injectors
Pro-M 80mm MAF
Race Systems custom Chip
255 Walbro Fuel pump
Car passed smog in 04 with the above mods, then these parts were added:
75mm TB + C&L intake plenum
Updated intake with aluminum crossover
Bassani Xpipe with cats
All the CO numbers passed with flying colors at idle rpms, and with the car at 2500 rpms it passed the HC and CO tests easily. It was just at 753 idle rpms that the car failed the HC.
The car was only warmed up for about 20 minutes before the smog. The smog tech even tried heating up the cats for a few minutes, although if you say it is a result of being too lean then I doubt that would make any difference.
You think if I removed the mods that were put on later it would pass, or do you think this is a result of the car beign out of tune?
[ January 14, 2005, 09:44 AM: Message edited by: 94Blackout ]
--------------------
87 5.0 LX: Exploded
94 Cobra: Totalled
94 GT Vert: Rear ended
98 Charged GT: Sold
65-67 2+2 Fastback: Someday...
Posts: 704 | From: San Jose, CA | Registered: Mar 2003
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jaybquick
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Member # 4286
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posted
quote:
Originally posted by 94Blackout:
Sorry, I need to edit my sig. These are the cars mods....
94 GT
Vortech S-trim supercharger, 8lbs
Trex fuel pump
30# injectors
Pro-M 80mm MAF
Race Systems custom Chip
255 Walbro Fuel pump
Car passed smog in 04 with the above mods, then these parts were added:
75mm TB + C&L intake plenum
Updated intake with aluminum crossover
Bassani Xpipe with cats
All the CO numbers passed with flying colors at idle rpms, and with the car at 2500 rpms it passed the HC and CO tests easily. It was just at 753 idle rpms that the car failed the HC.
The car was only warmed up for about 20 minutes before the smog. The smog tech even tried heating up the cats for a few minutes, although if you say it is a result of being too lean then I doubt that would make any difference.
You think if I removed the mods that were put on later it would pass, or do you think this is a result of the car beign out of tune?
I have made nastier pass when I was a smog tech for 5 years. It is because the cam you have high HC. Your air injection must no be injecting into the cats at idle. Verify its operation, you could have a solenoid problem. Or hokey it up so air always goes to the cats without the smog tech noticing it visually. Guaranteed you will pass
Oh yeah, those tests will allow an idle at like 1100 rpm, so raise your idle to about 1000, just make sure you keep the TPS voltage below 1 volt. .98 is best. Good Luck
[ January 14, 2005, 09:55 AM: Message edited by: jaybquick ]
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91 Mustang GT ET: 11.92@115
66 Mustang ET: 11.43@119
01 Audi S4 ET: 10.8@131
05 Audi S4 ET: 11.9@116
08 Audi S5 ET: 11.9@118
Posts: 416 | From: Lathrop | Registered: Mar 2004
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94Blackout
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Member # 2541
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posted
It is possibly a solenoid problem, when I drove the car yesterday the car wouldn't drop down to its normal idle, it would sit at about 2000 rpm... kind of like a sticky throttle. Shut the car off and turned it back on and the idle would be set.
I will try to set the idle higher, and how would I go about "hokeying" up so that the air was constantly going to the cat?
--------------------
87 5.0 LX: Exploded
94 Cobra: Totalled
94 GT Vert: Rear ended
98 Charged GT: Sold
65-67 2+2 Fastback: Someday...
Posts: 704 | From: San Jose, CA | Registered: Mar 2003
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TRIXSNK
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Member # 2844
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posted
quote:
Originally posted by jaybquick:
HC stands for Hydro Carbons. It indicates a lean codition. What were your CO% CO2% NOX readings? Was this a dyno smog? What part of the test did it fail? What year mustang do you have, what mods, etc, or is it the one in your sig?
J - ? for ya
I always thought HC's were they amount of unburned gas molecules that were being detected indicating a slightly rich mixture.
I'm probably wrong and i know that you were a smog tech. before so i thought i'd ask.
Isn't that why they are labelled as gross polluters?
![[Confused]](confused.gif)
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9 Sec EVO 9 is GONE!
New project in the works.......
Posts: 3740 | From: Bay Area | Registered: May 2003
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9lbpony
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Member # 3510
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posted
the trick is that you have to look at both HC and O2 to know what is going on. If the car is running rich you'd have excess HC but not excess O2. If the car is running lean (and thus misfiring slightly) you'd see HC and O2.
I'm convinced I could make a few $$$ selling an overdrive pulley for the smog pump. Swap it on before a test and inject 20-30% more air into the exhaust. Just the dilution alone would help...
That combo should be passable though - I've helped tune an S-Trim 347 with aftermarket heads/cam and 42# injectors to pass just fine. (same tune did wonders for the guys gas mileage)
Posts: 111 | Registered: Oct 2003
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94Blackout
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Member # 2541
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posted
There was no excess CO. I can't get the numbers, cause I have seemed to misplace the papers. So doesn't that mean I was running rich if there was too much HC and the CO was in line?
--------------------
87 5.0 LX: Exploded
94 Cobra: Totalled
94 GT Vert: Rear ended
98 Charged GT: Sold
65-67 2+2 Fastback: Someday...
Posts: 704 | From: San Jose, CA | Registered: Mar 2003
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jaybquick
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Member # 4286
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posted
quote:
Originally posted by TRIXSNK:
quote:
Originally posted by jaybquick:
HC stands for Hydro Carbons. It indicates a lean codition. What were your CO% CO2% NOX readings? Was this a dyno smog? What part of the test did it fail? What year mustang do you have, what mods, etc, or is it the one in your sig?
J - ? for ya
I always thought HC's were they amount of unburned gas molecules that were being detected indicating a slightly rich mixture.
I'm probably wrong and i know that you were a smog tech. before so i thought i'd ask.
Isn't that why they are labelled as gross polluters?
HC is completely unburned fuel. CO is partially burned fuel. CO is the first indicator of a rich mixture and once it is extremely rich the HC follows due to the miss. But a lean running car will have high HC and 02 however with our air injection systems it is hard to tell without actually disconnecting the air injection hose from the fitting to the cats to tell if it is injecting or not.
TO hokey it you have to remove or add vacuum to the valve by the header, that one selects between the head which is used for cold and the cats for when warm. The valve near the pump is for on/off. You may have to bypass both temporarily. However the raising idle thing may work, try to get the guy to throw his sniffer in the pipe for ya before ya start. You are pretty darn close. It would be great if you supplied us with all your readings.
[ January 14, 2005, 10:53 PM: Message edited by: jaybquick ]
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91 Mustang GT ET: 11.92@115
66 Mustang ET: 11.43@119
01 Audi S4 ET: 10.8@131
05 Audi S4 ET: 11.9@116
08 Audi S5 ET: 11.9@118
Posts: 416 | From: Lathrop | Registered: Mar 2004
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94Blackout
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Member # 2541
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posted
Ok, I will try to get the smog report numbers. However, I just realized that a wire from the EGR looked like it was unplugged. Could this have possibly been the culprit as well? The smog tech doesn't unhook that during the test, does he?
--------------------
87 5.0 LX: Exploded
94 Cobra: Totalled
94 GT Vert: Rear ended
98 Charged GT: Sold
65-67 2+2 Fastback: Someday...
Posts: 704 | From: San Jose, CA | Registered: Mar 2003
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jaybquick
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Member # 4286
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posted
The egr not working would not affect your idle emissions. He may have unhooked it to check the egr, but I don't see why. That is not the procedure I used to use.
--------------------
91 Mustang GT ET: 11.92@115
66 Mustang ET: 11.43@119
01 Audi S4 ET: 10.8@131
05 Audi S4 ET: 11.9@116
08 Audi S5 ET: 11.9@118
Posts: 416 | From: Lathrop | Registered: Mar 2004
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94Blackout
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Member # 2541
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posted
Here are the official numbers for idle:
796rpm
%CO2: 13.1
%02: 2.1
HC: Max-100 Ave-17 Measured-172!
CO%: Max-1.00 Ave. 0.00 Measured-.63
2470rpm
%CO2: 13.9
%02: 1.3
HC: Max-130 Ave-12 Measured-60
CO%: Max-1.00 Ave. 0.10 Measured-.51
Need help... grrrr ![[Mad]](mad.gif)
--------------------
87 5.0 LX: Exploded
94 Cobra: Totalled
94 GT Vert: Rear ended
98 Charged GT: Sold
65-67 2+2 Fastback: Someday...
Posts: 704 | From: San Jose, CA | Registered: Mar 2003
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jaybquick
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Member # 4286
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posted
you have when you need catalytic converters to work well, they need, O2, CO and HC. You have all 3 man. Thay are just up a little too. How old are the cats in your H-pipe. I bet they are going south. A new set will probably get the CO2% up over 14 which shows a good burn. My bet is weak cats unless they are new.
--------------------
91 Mustang GT ET: 11.92@115
66 Mustang ET: 11.43@119
01 Audi S4 ET: 10.8@131
05 Audi S4 ET: 11.9@116
08 Audi S5 ET: 11.9@118
Posts: 416 | From: Lathrop | Registered: Mar 2004
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94Blackout
¯
Member # 2541
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posted
quote:
Originally posted by jaybquick:
you have when you need catalytic converters to work well, they need, O2, CO and HC. You have all 3 man. Thay are just up a little too. How old are the cats in your H-pipe. I bet they are going south. A new set will probably get the CO2% up over 14 which shows a good burn. My bet is weak cats unless they are new.
I will check with the previous owner, he had the pipe put on. Thanks for all your help J.
--------------------
87 5.0 LX: Exploded
94 Cobra: Totalled
94 GT Vert: Rear ended
98 Charged GT: Sold
65-67 2+2 Fastback: Someday...
Posts: 704 | From: San Jose, CA | Registered: Mar 2003
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