Secondary Air Injection on late production 2006 L61's
11-16-2006, 02:47 PM
#1
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Secondary Air Injection on late production 2006 L61's
Certain late production model 2006 and on Cobalts with L61 (2.2L) engines had an optional emmisions system called Secondary Air Injection (SAI) added to it. This is a control system that added fresh air to the exhaust manifold to help burn off unused gases from the engine prior to entering the catalytic converter. It was required for California emmisions and I think some New York stuff too. The issue caused problems for people wanting to use aftermarket intakes and manifolds due to the lack of provisions for the system. At present, K&N is the only aftermarket intake system that provides for SAI. There are no aftermarket headers at this time, and probably never will be.
SAI is not Exhaust Gas Recirculation (EGR). It is actually the exact opposite. SAI adds fresh air to the exhaust. EGR routes exhaust gas back into the induction. While the Ecotec originally had a casting provision in the cylinder head for EGR, it was never used on any known models. The provision was deleted in the 2005 model year, however certain parts of the orginal casting still remain evident on the current production head.
Here are older threads on the topic:
2.2 Header
LSJ Header
Air pump line
Header for 2.2
EGR Bypass
Intake installation
EGR installation
Header installation
Header installation
If you have the system, your exhaust manifold will have a mounting provision right on top center for the air valve.
And you will have an extra line coming off of your air box.
The system can be best explained with some pictures. Heres the Patriot Performance cylinder head with some highlighting:
You can see on top the old casting for EGR. It was never used. On the Cobalt, and all 2005 and later Ecotecs, this was removed. However, the entry passages are still there in the manifold flanges. They don't go anywhere, they are dead end holes. They probably left them there so they wouldn't have to change the manifold flange designs.
Air is circulated through the actual flange of the exhaust manifold. Here's what it looks like:
It gets around the exhaust ports via the cross over passages in the head, and is then directed at the back of the exhaust valves via the passages in the head.
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I would like to qoute a post that is later in the thread:
This technique has been verified as a legitimate method of deleting SAI from your car in a completely legal way, as long as you don't live in California (sorry West coasters!). You would require either an aftermarket intake and exhaust manifold, or a way to block off the plumbing on the stock parts, but it does work.
SAI is not Exhaust Gas Recirculation (EGR). It is actually the exact opposite. SAI adds fresh air to the exhaust. EGR routes exhaust gas back into the induction. While the Ecotec originally had a casting provision in the cylinder head for EGR, it was never used on any known models. The provision was deleted in the 2005 model year, however certain parts of the orginal casting still remain evident on the current production head.
Here are older threads on the topic:
2.2 Header
LSJ Header
Air pump line
Header for 2.2
EGR Bypass
Intake installation
EGR installation
Header installation
Header installation
If you have the system, your exhaust manifold will have a mounting provision right on top center for the air valve.
And you will have an extra line coming off of your air box.
The system can be best explained with some pictures. Heres the Patriot Performance cylinder head with some highlighting:
You can see on top the old casting for EGR. It was never used. On the Cobalt, and all 2005 and later Ecotecs, this was removed. However, the entry passages are still there in the manifold flanges. They don't go anywhere, they are dead end holes. They probably left them there so they wouldn't have to change the manifold flange designs.
Air is circulated through the actual flange of the exhaust manifold. Here's what it looks like:
It gets around the exhaust ports via the cross over passages in the head, and is then directed at the back of the exhaust valves via the passages in the head.
---------------------------------------------------------------------------------------
I would like to qoute a post that is later in the thread:
if your vehicle has SAI then the rpo code is NU3-emissions system california,connect the tech2 w/the candi module to your delta using the sps system request info from your vehicle,verify the vin matches and then connect to your dealerworld sps site. go through the procedure like normal,at the end you will be askedfor your tire size,transmission type,and emissions rpo.choose the rpo that is not NU3 then you will be able to eliminate the SAI pump and hardware. if u just get rid of the system you will need a plate to cover the diverter inlet on topof the manifold
Last edited by Halfcent; 12-28-2007 at 11:17 AM.
11-17-2006, 02:05 AM
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we are still looking for some one to send us in their set up , so we can fit it for our header
i work at pacesetter for those that dont know , and our offer for you buying a painted header and lending us your stock parts so that we can update a header for you guys with these , and getting a coated header in return , is still open
i work at pacesetter for those that dont know , and our offer for you buying a painted header and lending us your stock parts so that we can update a header for you guys with these , and getting a coated header in return , is still open
11-18-2006, 09:24 PM
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Originally Posted by D4u2s0t
ok, i have the SAI, and i changed my downpipe today... i had 2 Cats!! that's right, 2 of them...
11-18-2006, 10:24 PM
#9
Originally Posted by Halfcent
Resonator, not 2 cats
11-18-2006, 11:17 PM
#10
now that i think of it, i don't think that ANY model cobalt has a resinator on the downpipe... so what makes you think that this one is not a cat, and in fact is a resinator?
11-18-2006, 11:28 PM
#12
Originally Posted by Witt
The cat is on the b pipe between the two oxygen sensors, the resonator is the long straight through muffler forward of the rear axle assembly.
i know what a cat is, and i know what a resinator is... i'm saying that i have 2 cats... on the downpipe, there are 2 cats... it's definately, 100% NOT a resinator...
11-19-2006, 12:26 AM
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look at your emissions lable , it will mention having 2 cats , main and a pre
if both what you can cats are on the down pipe , then its possible there is 2
if its after the flange then its a resonator
get pics
if both what you can cats are on the down pipe , then its possible there is 2
if its after the flange then its a resonator
get pics
11-19-2006, 05:18 AM
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Originally Posted by Red06LS
So back to my orginal question, is this good or bad that we have this?
I'll look at the plumbing diagrams in the morning and provide a better explanation.
11-19-2006, 08:21 AM
#17
Originally Posted by Witt
I just peered under my buddy's 2.2 that has secondary air injection, and there is only one cat. If there were two, one would be mounted on the manifold, which would be good for emissions, but bad for HP and flow. having 2 cats reduces cold start emissions, because the warm up time (cat light off) is reduced.
I'll look at the plumbing diagrams in the morning and provide a better explanation.
I'll look at the plumbing diagrams in the morning and provide a better explanation.
hmm...maybe i have a freak of nature... pics will be up around lunch time
11-19-2006, 01:45 PM
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Looking at exhaust plumbing diagrams from service manuals there are definetly pictures of 2 cats on the pipe, with the 2nd O2 sensor between them. Doesn't mention anything about it, but its in the pics. I would have looked at the manual last night, but my intoxication prohibited it. 
11-21-2006, 10:23 AM
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What would happen if I rendered my SAI system mute by deleting it on both the exhaust and intake. Say I purchased a GMPP intake (which i don't believe has a port for SAI) and an LSJ header. The SAI system would essentialy be gone, however would any issues arise from not having the SAI?
11-22-2006, 12:21 AM
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the cobalts that have air injection do have two cats(as you can see from his pics). the one is an oxidizing and the other is reducing. the other cobalts that do not have the sai have only one cat. and oxidizing/reducing cat. (three way cat)
11-22-2006, 10:14 AM
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Originally Posted by tonio5555
What would happen if I rendered my SAI system mute by deleting it on both the exhaust and intake. Say I purchased a GMPP intake (which i don't believe has a port for SAI) and an LSJ header. The SAI system would essentialy be gone, however would any issues arise from not having the SAI?
