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TECH ARTICLE: Using the '82 fresh air chamber exclusively and how to tune it with EBL

KANE

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Corvette
Dark Blue 1982 Trans Am(s): Polo Green 1995 MN6
If you plan to keep the crossfire looking stock and upping the performance, you've likely decided on porting the OE manifold or obtaining an X-ram or Renegade intake. You've probably also thought about a different ECM, injectors and throttle bodies too. Basically, you're thinking about how to pull in more air if you are going to use it with better heads, cam, etc.

You can use the existing fresh air chamber with the OE air box housing on the '82 Vettes.

EBL stands for Electronic Block Lockers and is a modified ECM from Dynamic EFI that is flash programmable and offers many upgrades over GM TBI ECMs on the market. Yes- you can also use any other ECM too. Megasquirt is another example. However, for this tech overview, I am using EBL as the example although a lot of this translates well to any ECM that offers an ambient air temperature sensor.

The provision on the top of the '82 air cleaner assembly is pretty large. It should be able to pull in a decent amount of air and the fresh air chamber in the hood is large too.

So, you can remove the solenoid and fresh air trap door to pull air from the fresh air chamber all the time.

This air will run cooler at higher RPMs and under greater demand as you drive. That needs to be accounted for in the tune. A good place to mount an air temperature sensor is below the headlight actuators in the stream of the air that comes up from the valance.

You don't need to suck in hot air, so you can close off the snorkel. On a modified motor, the snorkel would be a restriction anyway.

TBI systems are largely speed density- so getting close is really important in terms of calculating air mass for metering the fuel.

Attached are some images...

IAT/CTS Bias: This should be adjusted so the ECM reads the air correctly as it comes in. At lower engine demand, I am pointing more towards the CTS (ex.- idle and light cruise) and then towards the IAT at WOT. At idle, the car sits and the air can slightly warm up as it comes in through the hood and over the engine. But as demand increases, the air temperature gets closer to ambient as it rushes through faster with less time to get warmed up by the engine and hood. The table here indicates the values I have found that work for me- YOURS MAY BE DIFFERENT.

For comparison, included in this image is the setting for a TBI equipped Chevy Caprice. Here, you can see how the bias would look for a different car that uses a different set up to pull air in. Basically, using the fresh air chamber makes a big difference in the bias requirements.

Factory air cleaner: In this image of the engine from above, you can see how large the opening is! Pulling air through here full-time is the way to go if you plan to retain the OE air cleaner.

Removed trap door:
As stated above, you can remove this and pull air from just forward of the radiator as it comes up from the front spoiler.

Mounting location for the IAT:
I had mine affixed to the sway bar when I was tuning it and setting the bias. You can easily fab up a bracket to mount it anywhere in this area,

Sealed off snorkel: Cut a thin piece of aluminum and push it into place. This will keep hot air from the engine compartment out of the air box assembly.
 

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