Mods and emissions
Thread Starter
Pro
Joined: Oct 2014
Posts: 616
Likes: 193
From: Gilbert AZ
Mods and emissions
Here in Maricopa county Arizona, cars older than five years old need to get emissions tested every two years. Cars 1996 and up are tested via the OBD link.
I see a lot of parts for sale that are not CARB certified or are for "off road" use only. Yet apparently cars equipped with some of these parts are still passing emissions testing. I understand by stating that the parts do not comply, it removes some responsibility from the manufacturer, and may be stated just to "play it safe" with the environmental police.
So here is the question. If I modified my C6 with parts that state they are not legal for sale on emissions controlled vehicles.... Parts such as long tube headers, high flow cats, cold air intake, a mild cam, and got it tuned, what are the chances it will still pass the emissions test?
I'm sure there are a bunch of folks who have made these mods, how does the car do for emissions?
Thanks in advance,
Garry
I see a lot of parts for sale that are not CARB certified or are for "off road" use only. Yet apparently cars equipped with some of these parts are still passing emissions testing. I understand by stating that the parts do not comply, it removes some responsibility from the manufacturer, and may be stated just to "play it safe" with the environmental police.
So here is the question. If I modified my C6 with parts that state they are not legal for sale on emissions controlled vehicles.... Parts such as long tube headers, high flow cats, cold air intake, a mild cam, and got it tuned, what are the chances it will still pass the emissions test?
I'm sure there are a bunch of folks who have made these mods, how does the car do for emissions?
Thanks in advance,
Garry
Instructor
Joined: Jul 2010
Posts: 202
Likes: 3
From: Baltimore Maryland
Maryland tests emissions
Like that as well as long as you don't throw any codes you will pass if you have an O2 sensor burn out which you will if you do the previous mods listed just ask you tuner or the shop that does your mods tune out the O2 sensors like they never existed essentially how can the obd look for something that never existed in the first place
Like that as well as long as you don't throw any codes you will pass if you have an O2 sensor burn out which you will if you do the previous mods listed just ask you tuner or the shop that does your mods tune out the O2 sensors like they never existed essentially how can the obd look for something that never existed in the first place
Thread Starter
Pro
Joined: Oct 2014
Posts: 616
Likes: 193
From: Gilbert AZ
Thanks Stwigg5, what you said is what I'm finding elsewhere too.
From what I've been able to learn using the search function, the modifications I want to make should still pass an OBD type test as long as I have the rear O2 sensors "tuned out", and the car doesn't throw any codes. Is this correct? If so it seems like the tune is the critical component in getting the car to pass.
I'm not worried about visual inspections, the car will have good cats, and headers are legal here.
Another question... I prefer the low end torque and lumpy idle of a camshaft with moderately low LSA... in the 112-113 degree range. (I have an M6 car) This can cause increased valve timing overlap that would fail cars using a tailpipe sniffer, but should make no difference in an OBD type test. Is my logic correct here, or am I missing something?
And yet another question... What kind of data are the emissions guys looking at from the OBD port?
Thanks again,
Garry
From what I've been able to learn using the search function, the modifications I want to make should still pass an OBD type test as long as I have the rear O2 sensors "tuned out", and the car doesn't throw any codes. Is this correct? If so it seems like the tune is the critical component in getting the car to pass.
I'm not worried about visual inspections, the car will have good cats, and headers are legal here.
Another question... I prefer the low end torque and lumpy idle of a camshaft with moderately low LSA... in the 112-113 degree range. (I have an M6 car) This can cause increased valve timing overlap that would fail cars using a tailpipe sniffer, but should make no difference in an OBD type test. Is my logic correct here, or am I missing something?
And yet another question... What kind of data are the emissions guys looking at from the OBD port?
Thanks again,
Garry
Safety Car
Joined: Nov 2007
Posts: 4,537
Likes: 1,403
From: Bethesda MD
A mild cammed motor with hi flow cats can pass emissions tailpipe testing if properly tuned. The 112 LSA doesn't directly effect idle; it's primarily the amount of overlap which takes into account duration and overlap. Intake closing point can also effect idle as higher dynamic compression seems to help idle quality too. A lumpy idle is controllable based upon idle speed. Cut the idle speed on your car and it will become lumpy. On the flip side, temporarily raising the idle speed and other tricks can get a moderate cam to pass a tailpipe test.
The OBDII test is for anything the engine has flagged as not working that is emissions related. They will also tell you the test is incomplete if the engine has not run certain tests at the time they test the car. You come back after a few engine cycles on/off and retest.
Also keep in mind visual inspection. Some states do just a quick look and headers with cats pass because the inspector sees cats. Other states are much tighter about looking for a stock exhaust manifold and cats in the stock location. If you're state is a stickler on inspection a cam can still help if you stick with the stock manifolds; just spec it for a stock exhaust.
The OBDII test is for anything the engine has flagged as not working that is emissions related. They will also tell you the test is incomplete if the engine has not run certain tests at the time they test the car. You come back after a few engine cycles on/off and retest.
Also keep in mind visual inspection. Some states do just a quick look and headers with cats pass because the inspector sees cats. Other states are much tighter about looking for a stock exhaust manifold and cats in the stock location. If you're state is a stickler on inspection a cam can still help if you stick with the stock manifolds; just spec it for a stock exhaust.
Last edited by Ragtop 99; Nov 14, 2014 at 04:45 PM.
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,629
See what your emissions test consist of in your area.
In CA, any aftermarket parts has to have a CARB number to pass the visual test. Next they have the sniff test, and them even the OBDII test.
In other areas, they only do a sniff test, and you can get the car to run clean enough with headers, high flow cats, and even a cam to pass the sniff test instead.
In CA, any aftermarket parts has to have a CARB number to pass the visual test. Next they have the sniff test, and them even the OBDII test.
In other areas, they only do a sniff test, and you can get the car to run clean enough with headers, high flow cats, and even a cam to pass the sniff test instead.
Race Director
Joined: Sep 2007
Posts: 16,557
Likes: 2,106
From: Peoria/Phoenix AZ
C6 of Year Finalist (performance mods) 2019
Test in AZ is plug in the OBDII and if no codes are present and your gas cap passes the seal test, then you're good to go.
I'm CAI, tuned, catless headers, and if the kid who does the check is too busy to chat, the whole thing is under 5 minutes.
I'm CAI, tuned, catless headers, and if the kid who does the check is too busy to chat, the whole thing is under 5 minutes.
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Safety Car
Joined: Aug 2005
Posts: 4,279
Likes: 82
From: North Strand, NMB, SC; Retired x 2 (US Army: 70-90 AD) (US Army: 91-16 DAC); yea, I'm old.
I opted to stay with OEM parts (full Z06 exhaust from manifolds to muffler tips) since I wanted a fighting chance for whenever my county goes to an annual sniff test and I can honestly say that the entire engine/drive train/exhaust from front to rear is OEM.
Some counties in VA also do a visual test in addition to the sniff and I have heard of cars being failed just for having non-OEM parts before even having the sniff test completed...
Some counties in VA also do a visual test in addition to the sniff and I have heard of cars being failed just for having non-OEM parts before even having the sniff test completed...
Melting Slicks
Joined: Sep 2008
Posts: 2,360
Likes: 59
From: San Jose California
I have a question, if you tune out the rear O2 sensors, does it affect the readiness tests?
Last edited by djbrun; Nov 16, 2014 at 06:39 AM.
Race Director
Joined: Aug 2005
Posts: 13,592
Likes: 187
From: Hudson WI
NCM Sinkhole Donor
We have obdII testing in 8 or so counties in WI and the last time I had my car checked, they told me that visual inspection is coming and like you say, if you move or change anything that is not approved, you are in violation of federal law.
Race Director
Joined: Oct 2005
Posts: 14,999
Likes: 200
From: Bay Area Ca.
True- Way back on the east coast in the late 80s early 90s we checked during the safety inspection. ( Just CO % spec) Subject up to 5K per cat for this violation.(Federal ) I can not imagine this has changed.
I have a question, if you tune out the rear O2 sensors, does it affect the readiness tests?
I have a question, if you tune out the rear O2 sensors, does it affect the readiness tests?
I would double check this though I have been known to get confused!!
Safety Car
Joined: Nov 2007
Posts: 4,537
Likes: 1,403
From: Bethesda MD
I did mine years ago, so I could be off base. IIRC, the sensor are not disabled or made inactive. There are choices for each error code from illuminate the MIL upon failure, to report nothing. The computer is told not to report the error.
