air horn mod...

The last dyno test showed the engine running lean, so I decided to try a little physical tuning on it.





I cut off a stock 61mm air horn and shaved it down to fit into the 74mm inside diameter intake tube.







Then simply slid the air horn into the intake tube. That small hole was a bump that I sliced off so that it would be uniform in diameter enough to fit. I'm going to fill it in with some black silicone.











So now the entrance to the intake is exactly the same diameter as the throttle body.





I know it seems counterintuitive to restrict the opening, but since it's exactly the same diameter as the throttle body bore, it actually isn't. And anyways everything I try is for low end torque and not top end power.


Can't tell much difference because it's such a subtle change, and the gas mileage has too many running variables. Some days, all I'm doing is crawling up and down steep canyon roads in first gear. And the truck rarely sees the freeway. Throw in winter blend gasoline and things really get complicated because there's a lack of apples to apples comparisons.


I'm going to keep driving it around long enough to get a good gas mileage profile, and will log the results here.




Greg