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Old 01-12-2008, 03:13 AM   #1 (permalink)
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Fix Me - '71 Datsun 240Z

BlueStreak - '02 Bianchi Bianchi Eros
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OEM Air Injection, Yay or nay?

My Datsun 240Z has an air injection system, and I have been thinking about removing it. For those unfamiliar with air injection, its 1970's emissions technology. Basically, the engine turns an air pump, which is connected to tubes in the exhaust manifold that inject air to oxidize CO and HC' make CO2 instead.

This is definitely a good thing, I mean we're all trying to reduce CO2 emissions, but CO2 is nowhere near as bad as CO. However:

-The exhaust manifold tubes increase exhaust flow restriction

-The air pump increases engine drag

-The whole system adds weight to the car

Basically, the exhaust itself is cleaner in the sense that there is less CO and HC's, but it reduces gas mileage so there is more exhaust. It becomes a compromise between a smaller volume of dirty exhaust, or a greater volume of cleaner exhaust. Heres how I think I can improve FE and emissions by removing the system:

-Engines produce most CO and HC's at idle and other closed throttle conditions, so the air injection system is most beneficial during idle and engine braking (carbureted engines at least). However, I always turn off my engine at stoplights and have begun using EOC while driving.

-In its place I can install headers and a free flowing exhaust system that will increase MPG.

-If I want to further reduce CO and HC's, I can install a high flow catalytic converter.

-My car is registered under "classic car" status...I'm only required by law to get an emissions test every 5 years. This is important because I can avoid the visual inspection of not having the OEM air injection...and I can throw it back on there for an inspection if I have to.

-I can always lean out my carbs more to reduce CO and HC's.

Basically, I just think its an ancient band-aid fix to poor carburetor tuning...and that I could improve the FE and emissions using more modern methods and driving techniques.

So what do you think, remove the air injection or leave it in place?

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