Half-baked ideas, fully tested-ish.
This started as a simple upgrade.
Replace the stock upper intake with an aftermarket unit and call it a day.
Then I noticed something that didn’t sit right.
The aftermarket intake necks down to 3 inches.
The stock system coming out of the airbox is 4 inches.
So now the question becomes: why would I reduce airflow right before it matters?
The factory setup isn’t perfect, but it’s consistent. It keeps airflow larger for longer before transitioning.
The aftermarket piece looks better, but that 3-inch restriction stands out.
At lower RPM, it probably doesn’t matter much. The engine isn’t demanding enough air to make it an issue.
But at higher RPM or under load, airflow becomes the limiting factor.
Reducing diameter from 4 inches to 3 inches cuts cross-sectional area significantly. That’s not a small difference.
That means higher velocity, more restriction, and potentially less available air at the intake.
On a naturally aspirated 6.5, airflow is already not exactly abundant.
So intentionally choking it down feels backwards.
The current debate is whether to modify the aftermarket intake to accept a full 4-inch connection.
Options are:
The third option is the most work, but it also makes the most sense from a flow perspective.
The downside is complexity and the risk of making something worse if it’s done poorly.
The upside is keeping airflow consistent all the way through the system.
Right now, this falls into the category of “probably worth doing, but not urgent.”
It will likely run fine either way.
The question is whether “fine” is good enough.
This one’s still being tested.
Got a thought, correction, or better way to do this?
Email: thepracticaltangent [at] gmail [dot] com