madmikeismad
So mad
- Joined
- Dec 19, 2009
- Messages
- 14,347
At what point does it matter? How does it actually effect anything? I can't find anything good on it.
Hopefully Weston will chime in. He has some back to back comparisons on an engine dyno that were rather interesting.
It does have an effect on total airflow. Smaller a/r can and will choke the compressor if driven hard enough. It becomes more critical in the larger comp wheel offerings for a given frame size. Example: S400 with an 80mm or larger wheel tend to like the JD race cover or the even larger cat cover. Its application specific,what works on one engine combo may not necessarily yield the same results on another.
I get that, but when would you ever need a smaller a/r? Why not just always run bigger? Unless of course you're using smaller tubing.
Why not just always run bigger?
Bringing this back. I forgot to touch on your tubing size comment. In most applications I have seen other than some of the larger frame/comp wheel combos, the compressor outlet is smaller than the three inch charge pipes you speak. I have found that the cylinder head and how well it flows is usually the restriction in the system. Changing a/r may make a small difference in overall performance but nothing drastic.That would be awesome. I'm just not capable of imagining how different a/r would effect anything. Except maybe a tighter a/r slowing down spool and making the charger work harder. Velocity? But that goes out the window as soon as the air reaches the 3" (for us) tubing.