I saw this post linked to in my BMW motorcycle forum and thought you all might find it of interest.

 

yea, but they sound fast

I run stock filter Nice write up though

 

Nothing about HP gains or losses, huh?

I guess I'd better change my oil, oil filter and clean my intake more often.

 

Is this really a surprise?

 

Cory,

Have you got that engine put back together yet?

 

No sir your Honor. Life changes are holding me back right now. 2010 or bust!!!

 

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.

 

What would you rather have? 2hp (even if possible) with dirt getting into the motor or 2hp less with almost dustless air injestion.

Hmmm....

 

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.