So do you guys think it actually hurts airflow if the intake ports were widened at the intake manifold mating surface? I did that to mine, but mostly so there wouldn't be a ledge from my stock ported champion intake to the heads.
I think you did the right thing and your 9 second time slip agrees
Was not saying that porting the intake port opening past the valley pan gasket size to eliminate the pushrod bulge is wrong or detrimental.....
It just does not give you any gains or very little at best due to the real restriction being the intake valve/throat area.
On the champion or ta heads with there bigger intake valve that is less restrictive having the port bigger all the way back to the gasket area will show improvements.
Current trends in cylinder head porting try to limit the air speed in the intake port speed to .5-.55 mach or slightly under which is 563 feet per second.We are talking flow bench numbers here.
This is important because as the air speed goes up the air can no longer follow the turns in the port near the valve and the air goes turbulent
causing the max flow capability to drop. [ Thanks for the link jerryl ]
Smaller valves/ Higher rpms/Bigger cylinder size cause the air flow speed to go up and once the port is maxed out the HP the engine is making starts to drop due to the port/valve size not being able to keep up and fill the cylinder efficiently.
And as far the air crashing into the piston and cylinder wall you have to look at like this....the air that is stacked up in the port is at a higher pressure than the cylinder that has the piston going down and the intake lobe opening.....the air flows into this low pressure area and as the pressure drop from the intake port air going into the cylinder happens the air starts to decompress and expands filling the cylinder and with our turbo boost at some point the air in the cylinder will begin to pressurize again if the valve is open long enough....
Engines work on pressure Differentials...higher pressure air flows into a lower pressure area both on the intake and the exhaust side.
And absolutely the combustion chamber or cylinder wall or anything else that can impede the air flow will lesson the cylinder fill but it is what it is.
There are certain obstacles that can not be totally overcome.
Now picture all of this going on at 6000 rpm which means 3000 intake port/cylinder fills per minute or 50 times per second.
That means less then .02 seconds [2 milliseconds] to fill the cylinder. And less than this if you factor in camshaft duration=valve open time.
What we are ultimately trying to do is have the port flow enough air to fill the cylinder at max air velocity....if the port is too small velocity goes up air is turbulent and the port struggles to fill. If the port is to big for the engine the velocity slows and does not fill the cylinder as well as a higher velocity proper sized port will. Bigger is not better and smaller is not better...but get it right and it is payday. Our ability to turn the boost up makes
these things not as apparent as it would be on N/A engine.
*Side note:This also shows why a little detonation is a big deal....if you hear the rattle and it takes you 2 seconds to lift your foot of the gas..
well that cylinder just took 100 hits. Picture a champion boxer hitting someone 100 times in 2 seconds.
Here is a good picture of the port and its terminology.
Lots going on in a intake port in less than 2 millisecond.
