[Adam C.]

OK, back for more. Now we are going to look at the induction side. I thought about starting a new thread for induction, but we might as well keep it all together, I've already thoroughly hijacked this thread with my ramblings anyway.

So we will start just as we did for the exhaust side. The engine is our 5.0L numerical test mule. The exhaust is the original 36"long primary, 36" long secondary 180 degree system we started with in the exhaust study. Now we are going to only manipulate things that are related to the intake side.

The explorer EFI manifold on our mule has runners that are 19.5" long, from plenum to valve stem. This is the entire primary runner, including the upper and lower manifold, and head port. Although the runner diameter varies somewhat along it's length, it is nearly constant at 1.68" in the upper manifold where we will be playing.

First is primary runner length. Because I am all about making horsepower, we are going to make the primaries progressively shorter in 2" increments.

Not too suprisingly, as we shorten the runners, the botom end suffers while top end power increases. There is a limit in how much we can increase the top end. We are seeing diminishing returns at around 15.5 to 13.5". Going any shorter will only kill the low end, with no real benifit up top. We can see that if we wanted to go higher in the rev range, we would need to rethink our cam, heads, and exhaust system.