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K&N filters

This is one of the most debated topics on all car forums. It has been going on since at least the 60s. I can remember people drawing air to carbs from headlight buckets, cowl induction, the popup intakes on some mopars, and similar intakes on Torinos and Mustangs. The goal has always been to draw air from outside the engine compartment. Allmost all race cars also draw air from outside the engine compartment. It seems senseless to draw air from the engine compartment for any reason other than some change in sound. People used to turn the top of the old style air cleaner cover upside down mostly for the sound and some idea that they might also get more air to flow. To some degree this post does reveal something about my age but should be ignored.
I don't think a dyno result gives a real world long time realistic result as they are essentially a static test. Generally there is no way to account for airflow with the hood closed and the car moving through the air.
 
Big Jim said:
Drawing hot air cuts the power way back. Probably in the neighborhood of 205 to 30%. An open element intake drawing underhood air often suffers greatly in hot weather.
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I'm going to assume you meant "25 to 30%". That implies ambient-to-intake air temperature deltas of 275ºF to 330ºF. Allow me to explain.

Mean Best Torque -vs- air temperature is easily related back to how torque changes with air density; because temperature's main effect on air is changing its density. In general, torque production (or Horsepower) will change 1% for every 11ºF change in intake air temperature, because air density changes 1% for every 11ºF change in temperature.

The difference between 70ºF ambient air and 200ºF underhood air would be (200 - 70) / 11 = 11.8% less torque. I'd call that a real worst case scenario.

Now, I know a lot of people with data acquisition systems on their track and street cars (yours truly included...), and I've seen datalogs of IAT (Intake Air Temp) and underhood temps, and you might be surprised at how close to ambient temp the underhood environment is in a typical moving vehicle. Sitting on a chassis dyno just isn't the same; no quantity of dyno fans can fully replicate the environment of moving a vehicle through the air at speed.

p.s. I'm an old fart too, possibly right up there with oberthecat (one post up), and I've also seen an awful lot of this debate for a very long time. The recent availability of inexpensive and accurate data acquisition is often mushroom stamping a great many things that have long been accepted as "fact".
 
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I'll not get into the age thing except to say that most people think I'm about 10 or 12 years younger than I am. I also remember all those old things about "cold air induction" as well as attempting to obtain some "ram air induction".

I'll still stand behind my comment about 25% to 30% reduction in power. I don't doubt your calculations, rather I think there may be more involved. The power loss is very significant.
 
gmorrell said:
Now, I know a lot of people with data acquisition systems on their track and street cars (yours truly included...), and I've seen datalogs of IAT (Intake Air Temp) and underhood temps, and you might be surprised at how close to ambient temp the underhood environment is in a typical moving vehicle. Sitting on a chassis dyno just isn't the same; no quantity of dyno fans can fully replicate the environment of moving a vehicle through the air at speed.
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This seems to me to be the best way to answer these questions. It would be interesting to see the effect on measured real world performance on this question. It seems to me that turbulence generated by the filter element is alterd down stream by other parts of the intake system to include the uim/lim and the amount of stuff built up on the valves. Some turbulence in the combustion chamber seems to be necessary for complete combustion. I believe a clean filter is probably more important than its type for most of us most of the time.
All this has not prevented me spending money to change my intake system from the cylinder heads to the fenderwell with SVT parts. I really don't think I will get that much benifit I do however want to do it. At first my intent was to get the intake system cleaned up and have in part justified this spending by rationalizing I have no way to responsibly dispose of the used chemicals. It makes me happy and that is what counts most.
 
If the factory didn't have to worry about drivability issues, they'd install open element systems at the factory, wouldn't they? With less parts to the intake, they'd save money too.
Karl
 
98SVTC said:
If the factory didn't have to worry about drivability issues, they'd install open element systems at the factory, wouldn't they? With less parts to the intake, they'd save money too.
Karl
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no they wouldn't. your forgetting about NVH,noise vibration harshness.
 
Big Jim said:
Sure, just as soon as I can figure out how to collect data from the butt dyno.
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Spend more money on go-fast parts - I have found a direct correlation between wallet thinness and butt-dyno accuracy and resolution.

Can't help with the data collection part; probably involves an anal probe or something, let's not go there... :ponder:
 
a K&N filter shouldnt really make any difference if you are using the regular replacement for your stock filter. Put your filter box on a flow bench, you can see there isnt any difference in flow. Thats because the airbox is actually a bigger flow restriction than the filter itself. Yeah those displays in the parts store are kinda misleading. The filter element flows better, but it doesnt make a difference unless you are using a short ram or better still cold air intake. Or unless you fab a different air box.
Different dyno numbers are usually also misleading. Most guys when they dyno something they will dyno it first with the factory part, then add the performance part. The ambient temperature in the room may have changed since then. A running engine will effect humidity. And warming up the engine from the first dyno pull will warm the oil making it flow easier. Less resistance, therefore it takes less horsepower to circulate oil. Also as the engine is warmed up the parts have expanded to operating specs, and therefore moving parts fit better. Engines are designed to perform best at operating temperatures.
Lastly dyno pulls are generally worthless when it comes to intake hardware, since you are sitting still and air is not moving over the vehicle. its easier to pull air through a K&N or similar filter than through a paper filter. however while the vehicle is in motion you will have higher air pressure in your air dam and it the engine wont have to work as hard to pull the air through to what the air box is designed to flow.
 
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