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YOUR RESEARCH"Freer flowing" air filters debunked?!
Leading reported evidence
Run stock filter
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Leading evidence: 'Run stock filter' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Clean intake more often' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
I guess I'd better change my oil, oil filter and clean my intake more often.
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Suggestion
I guess I'd better change my oil, oil filter and clean my intake more often.
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Suggestion
The same reason shortening the length of the intake will change power.
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Suggestion
Running without an air filter dramatically changes the velocity of the air to the intake and will actually reduce the Volumetric efficiency and reduce pwoer.
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Suggestion
Running without an air filter dramatically changes the velocity of the air to the intake and will actually reduce the Volumetric efficiency and reduce pwoer.
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Suggestion
I still stand by the Bruce Anderson Dyno test presented at Tech tactics which showed that on a 993 3.6 engine, there was no HP gain with NO airfilter installed.
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If Porsche could pick up extra power with a different air filter they would. fact is the OEM filter flows more air than the engine can breathe at max revs even whewn fairly dirty.
Bruce Andreson did a test with a 993 some years ago. Ran a dyno test, with the OEM filter, a K and N and then with no filter at all. No difference in power anywhere across the power band.
Installing a freer flowing air filter is a compromise between more air and less filtering or less air and better filtering. Installing a freer flowing air filter will produce more power as long as the computer has the ability to increase fueling. The velocity of the air with a new filter will also have an effect on power.
I beg to differ, a free-flow filter will increase power if the ecu can provide more fuel but more importantly, the engine needs to be able to use the added air. A 3.6 liter engine turning 6,000 RPM pumps 21,600 liters of air per minute. If the OEM filter can provide three times that amount, a less restrictive filter or no filter at all will do nothing.
More interesting than the flow of air by the filter was the difference in the measure of dirt particles between the OEM filter and the 'freer flowing' filters. It really does get you thinking about impact on the life of the engine for a daily driver.
Actually, if you want to get technical about it, a freer flowing filter, regardless of whether the engine can breath in the added air, will decrease the intake air temperature due to less friction. Addiionally, the change in the velocity and resonance of the air will effect power. The same reason shortening the length of the intake will change power.
Your engine is not 100% efficient and can ingest more air if it is available. Proof is the increase in current to the MAF when you install a freer flowing fliter.
Bob, I agree 100% with that statement. If the additional HP was there to be had by using a different air filter design, the Porsche engineers would have already done that.
I've been chanting this for years. Only 1/3 of the panel really sees any airflow. If anyone doenst believe it, take out the stock one and look on the underside.
I still stand by the Bruce Anderson Dyno test presented at Tech tactics which showed that on a 993 3.6 engine, there was no HP gain with NO airfilter installed. Note that they also saw 5-7 HP gains by drilling holes in the airbox cover. Porsche had to compromise on intake noiose to meet Swiss Drive-By noise regs. That being done, they tested a K and N versus stock versus no filter and saw no increase. On some cars (Hondas) come to mind, a cold air induction system does produce meaningful gains but a helluva a lot of noise too. Honda may have compromised a bit to silence intake noise it seems.
The facts as I explained above are very easy to prove. Installing a freer flowing air filter will increase the MAF signal which measures the volume of air passing by it. The air can only go into the engine and nowhere else. Since your scanner will also prove that the amount of fuel injected increases as the air flow does....guess what? Unless your Volumetric efficiency falls,you have a bonafide increase in the a/f mixture.
So, like I said, and the laws of physics back me up, you WILL increase power when you increase the a/f ratio in the cylinders.
The ONLY reason your intake will not ingest more air is do to a restriction in the exhaust.
Running without an air filter dramatically changes the velocity of the air to the intake and will actually reduce the Volumetric efficiency and reduce pwoer. This reduction in power is partially offset with an decrease in air temperatures making what air does get to the cylinders more dense.
Do you know where and how big they drilled the holes? yes, I would do it!
BTW, Since the air is drawn in pulses, you are changing the characteristic resonance frequency and magnitude by the shape of and restrictions in the housing. Its kind of like a little wave engine.
Agreed. And also, as I pointed out in the thread about the holes drilled in the 996 airbox, people always complain about the amount of dirt that free flowing filters let in. However, I still assert that this difference is academic at best since I have never read about an engine failure positively attributed to damage caused by dirt ingestion.
"..I have never read.."
And you likely NEVER will, as we're talking about your new Porsche engine lasting only 100,000 miles vs 250,000 miles with OEM air filters.
No in fact they don't. With the factory motorsound option, the air box cover has about 75 small holes drilled in a circular (think speaker grill) pattern. This simply lets more air get to the filter, it does not bypass the filter.
Folks here have 250k on their 996 odo's or is this a guess/hope/dream? I had 165k on my previous car using a Jim Wolf Technology cone filter(basically a K&N type).
I can agree with the test stating more debri enters the intake than stock especially since one can clearly see the holes are larger in a cotton filter. I'd now like to see a test of how much life the debri takes off the engine and how much is burned away (including the debri that passes through an oem paper intake). I think proving the debri that passes through a K&N intake robs the engine of the power it gains from more airflow would be quite interesting.
Bob, wouldn't that be warm engine air? From what I've read about all these CAI, they seem to highlight the advantages of a cold air intake. Can you elaborate so I can understand why poking holes in the airbox is beneficial? As I'm a bit ignorant on the subject, I'm curious if the airbox is only there to minimize noise? Does it offer an improvement in wind dynamics or back-pressure?
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