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Discussion Starter #1
Hey guys,

I have some questions regarding the secondary air flow system. I will break them down, but basically if your guys answers confirm my thoughts, i think i may be able to devise a fix to this issue, but first i must learn some vital information about the secondary air flow injection(SAI). As you know, the SAI are quite common, but most vehicles inject the air into the exhaust manifolds. This piece being removable, it much easier to clean or replace rather then pulling the heads and etc. Anyways, what i plan on doing is routing the secondary air flow lines into a port before the pre-cat o2 sensors.

Question 1: How does the DME monitor the SAI system? As far as i know, it detects inadequate flow by the A/F ratio during start up. I presume if its not quite lean enough it detects its not pumping enough air in resulting in a "Low/Incorrect flow" code. Is this correct?

Question 2: Where exactly is the secondary air pump? I havent really looked for the pump personally, mostly due to a lack of time lately trying to figure out the software fix issue which i will not disclose at this time.

Question 3: Has anyone tried this before?

Basically what i am going to do is re-route the line going into the head. I will use a stainless steel braided line with a -4an fitting and drill/tap into the exhaust downpipe lets say 2ft or so before the precat o2 sensors. Essentially what im hoping is, the ECU will see that the A/F ratios are lean, in the way they should be if the SAI system was working correctly at the correct flow rate.

Im hoping this is as simple as i think it may be. If it is, i will give it a shot, and if it works, i will post a DIY on how to do it and what parts will be needed. Myself i am a 2nd year apprentice, and at my disposal i have 7 other Nissan master technicians one of which is a Ferrari/Maserati qualified technician.

Any help would be greatly appreciated. Yes i have searched, and it is very possible ive missed things if its been posted already.

Thanks
Chris
 

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Hey guys,

I have some questions regarding the secondary air flow system. I will break them down, but basically if your guys answers confirm my thoughts, i think i may be able to devise a fix to this issue, but first i must learn some vital information about the secondary air flow injection(SAI). As you know, the SAI are quite common, but most vehicles inject the air into the exhaust manifolds. This piece being removable, it much easier to clean or replace rather then pulling the heads and etc. Anyways, what i plan on doing is routing the secondary air flow lines into a port before the pre-cat o2 sensors.
There isn't much room right there. You would have to vent a very heat resistant line fairly early in the exhaust system. This would be a bypass as the current set up runs through the block for some stupid reason.

Question 1: How does the DME monitor the SAI system? As far as i know, it detects inadequate flow by the A/F ratio during start up. I presume if its not quite lean enough it detects its not pumping enough air in resulting in a "Low/Incorrect flow" code. Is this correct?
I'm not exactly certain.

Question 2: Where exactly is the secondary air pump? I havent really looked for the pump personally, mostly due to a lack of time lately trying to figure out the software fix issue which i will not disclose at this time.
In the front bumper, on the right (passenger side with left-hand drive) side. There is a software "fix" per se through powerchip that lowers the threshold of acceptable ratings of the precat o2 sensors during cold startup.

Question 3: Has anyone tried this before?
See Q2 on the "fix". I suggested a bypass once, and although it may work, doing this would be costly, dangerous, and the result would be unknown. BMW has a "fix" that involves drilling through the carbon build up with an auger. I believe the cost is a small amount ($8,000 USD) and no guarantee the previous condition will not return.

The theory behind the secondary air injection system is to blow fresh air into cold exhaust, allowing the catalytic converters to heat up much quicker, thus reducing noxious emissions the converter was designed to reduce. As soon as the converters are at temperature, the air pump ceases to pump air in the system. However, in the S62 engine, the air ducts run through the engine block and there is no check valve (or a good check valve), allowing for exhaust gasses to deposit carbon in these ducts.
 

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Discussion Starter #3
Yeah. Basically i had an issue with the software fix. I will not discuss it over the board though. Anyways, yeah, i understand about the heat issue what i may end up doing is welding on a 6" section of small tubing to that the line is not directly in the exhaust so the heat would have to travel up the pipe. Obviously it will not stop it from getting hot, but it should help it quite a bit. That would be the reason for the stainless steel braided lines, i figure if they can hold up to the constant heat from a turbocharger, it should be able to handle exhaust heat, for atleast long enough til i can smog the car!

I will take a look at the air pump either tonight or tomorrow and see what i can devise. As it stands right now, i have nothing to loose, because its either try this, start pulling the heads, or pay the dealer to do it.

I think the worst thing about this car is the amount of special tools required to do any internal work to this vehicle. It sucks, i guess its a price to pay to drive an M5.
 

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The vehicle measures the SAI using the pre-cat and post-cat O2 sensors. This allows it to determine both a/f mix as well as efficiency of cat's so it knows when to shut the SAI pump off.

d-
 

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Wow someone has the exact idea I was about to do to my car. I just haven't had time to do it. To bad your up there in Canada, I would say come on down and we'll try to it together.
 

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Shoot me an e-mail if you want to try to work together on this, I have access to pretty much everything you could need here and I'm a master tech. I have spoken with several other masters I work with about performing this modification to the secondary air pump piping. So my Idea was to run piping for down to the the front part of the exhuast. Another tech said I should just make a longer nipple to help cool the heat and put high temp hoses to the secondary air pump vacuum switch.
 

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Talked to afew guys at my work one of them had a good suggestionhr said why don't you disconnect a vaccum line while the air pump is running causing it to run lean then after the pump turns off hook it back up. It's simple but I think it could work. Alternatively use the solenoid/relay that turns on the pump to activate a evap solenoid and cause a vacuum leak. That way it's timed
 

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Have you thought about modifying the intake system? Our simple mods shoot cool air into the stock intake systems, less work, but more affective.
 

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Talked to afew guys at my work one of them had a good suggestionhr said why don't you disconnect a vaccum line while the air pump is running causing it to run lean then after the pump turns off hook it back up. It's simple but I think it could work. Alternatively use the solenoid/relay that turns on the pump to activate a evap solenoid and cause a vacuum leak. That way it's timed
 

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Have you considered Direct Exhaust Injection (DEI)? It would seem that recirculating the exhaust should help warm the engine up faster while significantly reducing emissions. Google is an excellent resource...

d-
 

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well you could try to take the vacuum line off of the vacuum modulator for the secondary air pump...The valve that turns it on and off by engine vacuum...But I dont think that would be enough air passing the MAF into the intake manifold for the DME to be satisfied. But it wont hurt to try, and that line will shut off after the DME tells the vsv to shut down that secondary air pump valve. So I know that is timed. Very good idea but It would need more than that I would think.
 

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Well I would keep the secondary air pump running I was thinking about trying one of the oil seperator hoses. All I need to do is get it thru aircare then I'm fine!

I am going to have my ecu flashed back to stock by PC then I will let you guys know how it. Works!
 

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SUBSCRIBED. I always fall for these CBU posts.

On a lighter note, jt2ma71, I'll be in Richmond/Vancouver/Victoria/Whistler during the Olympics. Hoping to meet you and checkout your M5, if possible. :)
 

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Since I don't really care about my contribution to the environment, I won't make any changes as the trick of resetting the OBD2 prior to emissions checking seems to work for me. :)

The other way is to use a cat heater.
 

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The theory behind the secondary air injection system is to blow fresh air into cold exhaust, allowing the catalytic converters to heat up much quicker, thus reducing noxious emissions the converter was designed to reduce. As soon as the converters are at temperature, the air pump ceases to pump air in the system. However, in the S62 engine, the air ducts run through the engine block and there is no check valve (or a good check valve), allowing for exhaust gasses to deposit carbon in these ducts.
Ok, I have a few questions.

1. If I was to completely remove my Sec Air pump - what would happen, other then not being able to pass E-check.

2. You say in S62 engine air ducts run through the engine. So just to get this straight - the Sec air pump pushes air into the CAT then from the Sec air pump air is pushed into the engine cylinders? Does this happen together at the same time? Why would extra air be needed in the engine? Is the air intake system not enough?

3 How do exhaust gases deposit carbon into the engine and through what ducts?

Maybe , im not understanding this completely?....

Thanks in advance..
 

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Discussion Starter #16
Ok, I have a few questions.

1. If I was to completely remove my Sec Air pump - what would happen, other then not being able to pass E-check.

2. You say in S62 engine air ducts run through the engine. So just to get this straight - the Sec air pump pushes air into the CAT then from the Sec air pump air is pushed into the engine cylinders? Does this happen together at the same time? Why would extra air be needed in the engine? Is the air intake system not enough?

Maybe , im not understanding this completely?....

Thanks in advance..
1. if you remove your secondary air pump, you should block off the lines. As for side effects, your cat will take longer to heat up. So basically the environment will suffer slightly.

2. The secondary air pump pumps air into the heads. the heads have secondary air port passages, IIRC there is an inlet port on each head. From there on there are passages that exit right behind the exhaust valve. So the air pump, pumps air into the head thru the port on the exhaust valve, by doing so it creates an excessively lean mixture on a cold start in order to heat up the cat faster. This is an emissions thing.
 

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Thanks! That cleared up everything . One more thing though. I have a code for Sec Air pump currently and my SES light is on because of this. If I disregard this code and keep on driving will it harm anything other then the enviroment? Performance factor in at all?

Also how does carbon build up associated with the Sec air pump system?
 

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Thanks! That cleared up everything . One more thing though. I have a code for Sec Air pump currently and my SES light is on because of this. If I disregard this code and keep on driving will it harm anything other then the enviroment? Performance factor in at all?

Also how does carbon build up associated with the Sec air pump system?
No harm to your car, either in damage or performance. Correct.

I believe the issue is backflow of exhaust through the tubes in the engine block, depositing carbon. Someone else can correct me if I'm wrong.
 

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Thanks! That cleared up everything . One more thing though. I have a code for Sec Air pump currently and my SES light is on because of this. If I disregard this code and keep on driving will it harm anything other then the enviroment? Performance factor in at all?

Also how does carbon build up associated with the Sec air pump system?
No, but you won't know when you get ANOTHER fault (that might be serious) because the light is always on...
 

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I'm curious now. I don't have the CBU problem but the tech in me wants to know....

Do the heads actually have to come off the block to be "cleaned?" Maybe it's easier to drop out the engine completely so you have access to those ports.
 
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