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The resonator and lower air box losses are about the same and one should expect these 'dynamic' losses to be about the same. The resonator can be removed some how, but this really suggests that the 3" duct mod would be good. It reduces two dynamic losses to one and the larger flow cross section means less velocity and then less dynamic losses. So these losses might be reduced by perhaps 4:1. With that reduction, the reduction of air filter losses then are more significant.
I think that the K&N filters and other such would show an advantage VS paper after the paper started to accumulate dirt and well before the exhaustion of the paper element service life.
The orientation of the 'pressure' ports in the air boxes can have a significant effect. IE one can get incorrect readings, but these would be incorrect in a similar fashion for each. "The pressure port (actually a vacuum port due to pressure loss) was attached to airbox just above the air filter." If the port opening was facing the filter, it would measure dynamic+static pressure, not static pressure.
We do not know if the air filter tests
(Bob's)actually measured the pressure drops at the same air flow. We only know what the engine RPMs were. The only way to do that would be to put two air boxes in series and use a blower. The air mass flow through each would then be the same. In your tests, you do know that the air flow through the MAF and filter were the same.
With the small air boxes in the NG900's and OG 9-3's, with the air flows in these turbo engines, the filters may simply be too small. And with increased HP mods, low restriction air filters may be all the more beneficial. With the T5's there were no MAFs. So a T5 with a duct mod would be a lot less restrictive than any T7+MAF could ever be. So the effects for the T5's may be in a different class.
So perhaps the issue is air boxs and MAFs that create pressure drops. I think that too many folks have had good results with K&N type filters to throw all of that away based on Bob's figures. I do think that we need to address the big picture and tackle the big problem, dynamic flow losses.
Dynamic losses occur when flow speed change and the kinetic flow energy is lost, then the flow needs to speed up again, as in the turbo inlet pipe. The shape of the end of the intake snorkle is also critical and a bad design creates a pressure drop VS one that that attempts to reduce such entrance losses.
There is a pressure drop from the air box (after filter) to the exit duct, created by the pressure drop needed to accelerate the air from the air box large x-section to the x-section of the duct. I think that your MAF figure probably lumps two pressure drop sources together.
How did you implement pressure ports and how did you orient them VS the flow directions?
You have done some very intersting work that quantifies something that has had lots of discussion, but no hard data.
And a note that the 9-5 T7 intakes that I have seen do not have a resonator. I do not know if early production did or not.
The screens on MAFs are not to keep junk out, but the screen serves as a flow straightener and it cuts up large scale turbulance. This allows the velocitys seen in the center of the MAF to be extrapolated to an overall flow measurement. Some folks have removed the screens on MAFs and then created some serious problems. Not something that one can do, but there may be some MAFs designed for performance applications where the screen losses are reduced. Flow screens are used this way on the intakes to wind tunnels as well. These are in large cross sections and cut the flow disturbances into small ones, then as the flow cross section reduces going towards the test section, the small vortex structures are elongated and and these disipate rapidly.
, Sat, 24 Sep 2005 18:11:59, Sat, 24 Sep 2005 18:02:13
, Sat, 24 Sep 2005 17:32:01
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