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Why is There a 1600 Airbox on This Engine?
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This page uses drawings and photos from various Alfa Romeo documents (and other sources) to describe the benefits of using the air plenum from the 1600cc engine (instead of the stock 1300cc). |
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• Kinks in the System
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A photo of the ram air filtration system for the 1300cc engine is shown at right.
(disregard the arrows)
Airflow is from the right (tube from ram air intake in front grille)
to left (down through the aluminum plenum and into the intakes of the dual Weber carburettors).
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The drawing on the left shows the airflow through the system (red line, flowing right to left).
Obviously, there is a sharp kink in the flow within the air filter (canister at top-left).
This kink causes turbulence, reducing the air pressure delivered to the carburettors.
This design also uses a relatively small area of the total surface of the air cleaner.
There is NOT a lot of room in this engine compartment, and this was a pretty good solution at the time.
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The drawing on the right shows the airflow of the 1600cc ram air intake system.
There is still a kink in the system through the air filter, but it is more gradual (less turbulent), there are no bends across the top of the engine, and a greater portion of the air filter surface area is used.
Alfa Romeo used the increased room in the engine compartment to "straighten out" the system.
Much better.
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• Better Access
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The bottom half of the 1300cc air plenum is shown at left.
It tapers sharply to almost a V-shape at the bottom. This makes it extremely difficult to get a carburettor synchronizer snugged-up to any of the four intake ports. |
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The 1600cc air plenum is shown at right.
It is easy to see that the bottom of the plenum bowl is more U-shaped than on the 1300, and it is also wider (from left to right in the figure).
This extra space makes it a LOT easier to synchronize the carburettors. |
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• A New Air Filter System
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I have been using the air plenum from the 1600cc engine for several years.
I manufactured my own in-line filter (the filter worked well, but wasn't pretty).
Annoyingly, the top half of the plenum was stolen this year (!!!). However, this bit of bad luck provided me with the opportunity to re-investigate the system.
After spending some weeks finding a replacement plenum (thank you, Alfa Parts Exchange), I discovered a new air filter was available that was PERFECT for this application.
In 2010, K&N released the "Apollo Cold Air Intake System" (circled in the photo at left).
Its small size and excellent performance features enabled me to take out all the kinks that CAN be taken out of this system.
and performance features made an off-the-shelf, high quality filter system
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The K&N Apollo. System information.
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The K&N Apollo air filter. |
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