Posted by Alex J [162.158.79.56] on Monday, October 17, 2016 at 08:17:43 :
Okay, so going to do some thinking out-loud here since you guys seem to like discussing technical stuff.
A few things in regards to air filters, diesel engines, and all that nonsense.
Look past the disdain for K&N air filters as they are the dimensional basis for this math as they provide a plethora of design information and I've not had a problem from them in the 300k+ miles on vehicles using them.
My 24V Cummins 5.9 in my '06 2500 uses a filter that specs out to 6.25" dia x 9" long cylindrical. The total surface area is 177 in^2... the filter I am comparing for trying to stuff under the hood of my Carryall is roughly 5" dia x 7", but the end also has a filter on it making it a total of 130 in^2... The difference here is about 27%... the difference in engine displacement is (1)-(3.9/5.9)x100% yielding or (1)-(4 cyl/6cyl) which is obviously around 33%... so I should be good in the sake of volumetric flow... Since the formula for CFM consumption is based on quite a few constant values, and the only thing I am changing is my engine displacement by a constant value of 33% my air consumption should reduce by 33%... Right?
So second part of the question is the effects of under hood air temperatures and the effect on engine performance. Obviously cold air is more dense, and therefore compressed dense air contains more oxygen, and thus a more efficient burn. Now, getting into the world of a stock tuned, electronic controlled, high pressure common rail engine, the difference in ambient air temperature, compared to ~140 ~180 degree max underhood temperature (I am thinking summer pulling grade with the exhaust near the air filter)... how much am I hurting the engine, and am I creating a hateful cycle of elevated EGT?
My plan is to put my air filter along the inside of the passengers side of the hood near the firewall and create a heat shield over the exhaust... I also thought about wrapping the exhaust system around the manifold, and all the way down past the floor... hindrances there? End of the filter would be below the AC bulkhead there and close against the side of the hood. This is a WC53 for those not following what I am building.
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