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I'm being asked this by a customer with an 05. He wants to put a pair of DirtyDeedsIndustries.com headers on his truck. He doesn't have to worry about smog so he doesn't care about the air injection tubes or the cats. His main concern is where does the air injection come from? Can you bypass the pump?
 

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Got this from a 5 yr old thread asking about "new" 2005 Tundra headers. It was buried deeeeeep...

...a system of an air pump and tubing to each manifold/header pipe to inject air (oxygen) just downstream of the exhaust valves. It's done (usually on engines with lots of valve overlap) to minimize the amount of unburned fuel that goes down the exhaust pipe. That unburned fuel plays havoc with the emissions numbers and can cause overheating of the catalytic converters. Injecting air into the manifold where the gasses are still very hot burns the extra fuel there.

Apparently the '05s variable valve timing has enough overlap at high RPM that air injection became necessary to meet emissions requirements. And because the '05 engine does have air injection, I'm really really doubtful that any header for the '04 and earlier engine is going to work on the new engine. Be very suspicious of any retailer who lists the same header part number/SKU for '05s that they list for '04s and earlier.

Also, I read this from another popular Tundra website, this should help your customer...
Air injection is used to improve cold-start emissions, a federally-mandated emissions requirement. By injecting fresh air into the exhaust stream, the catalytic converters will heat up more quickly and therefore become more effective at scrubbing exhuast gases. Once the catalytics are warmed up, the air injection system is no longer needed.

On the 2007+ Tundra, the air injection system turns on at cold start and runs for 1-2 minutes until the engine computer determines the exhaust system is sufficiently warm. The injection system is purely needed to improve emissions – it has absolutely no impact on the core function of the engine. In fact, your truck would run better, cost less, and be more reliable if it didn’t have this system…but it wouldn’t be as “clean” environmentally, so it’s required by federal law.
 

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The pump is under the intake manifold, along with a pressure sensor, and a primary valve. I think the biggest issue to removing it will be pissing off the ecu, since It monitors the pressure. I relocated mine for a supercharger install, when I start the truck with the hood open I can hear the pump running for a few seconds. I haven't tried running it without to see if I get any CELs yet.
 

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"That unburned fuel plays havoc with the emissions numbers and can cause overheating of the catalytic converters. "

"By injecting fresh air into the exhaust stream, the catalytic converters will heat up more quickly and therefore become more effective at scrubbing exhuast gases. Once the catalytics are warmed up, the air injection system is no longer needed."

Unless I misread them, the 2 statements quoted earlier contradict each other. I wonder which is correct.:confused:
 

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Discussion Starter #5
"That unburned fuel plays havoc with the emissions numbers and can cause overheating of the catalytic converters. "

"By injecting fresh air into the exhaust stream, the catalytic converters will heat up more quickly and therefore become more effective at scrubbing exhuast gases. Once the catalytics are warmed up, the air injection system is no longer needed."

Unless I misread them, the 2 statements quoted earlier contradict each other. I wonder which is correct.:confused:
no kidding they do contradict each other. I would almost tend to think they're both true to an extent.

Well I looked real close at the air injection tubes on an 05. I would think that you could simply cut off the individual air lines until the main line. Then tap that main line into the header collector just before the cat, the fresh air is what the cat needs to work. I dunno, but I would think that it doesn't matter where the air is injected as long as it's injected before the cats.

5.0 Mustangs inject with a single line as I described above. My buddy's 75 Nova injects individual runners so go figure?
 

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2004 has no air injection but the 2005 and 2006 does. This makes finding headers for the 2004 really tough because most of the headers out there are made for the air injection trucks.

My understanding of the air injection system is that it only runs when the truck starts up until the cats are at optimum operating temperature and then they shut off. I could be wrong but my two coppers for what they are worth.
 

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...My understanding of the air injection system is that it only runs when the truck starts up until the cats are at optimum operating temperature and then they shut off. I could be wrong but my two coppers for what they are worth.
You are correct.

Upon cold startup, an engine is running rich with cold catalytic converters. The air injection system simply adds fresh air to the exhaust stream prior to the cats to 1). get the exhaust gas closer to stoichiometric balance, which will 2). support more efficient catalyst function, which will 3) assist the catalyst reach operating temperature quicker.

The PITA part of the air pump system, at least in the Gen-2 engines, is that failure of the system in any way causes the ECU to go into 'limp mode'. That is a disgrace -- and dangerous. An emissions mandate is now affecting actual vehicle driveability. In my mind, that is just plain wrong.

Not only that, but the design of the intake tubes and location of the pumps is fostering pump corrosion and failure in short order -- to the tune of $1200 at the dealer. What a joke.

If I had one of these air pump systems, the first thing I'd do is install an electronic ECU bypass and disconnect the damn things.
 
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