Consquences of the air filter fitted in the wrong direction
09-26-2012 | 01:40 PM
#32
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Joined: Feb 2003
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From: saratoga, ca
If it's the O2 sensor, then why have a MAF at all?
You're missing the point that the air filter is affecting the _pattern_ of the flow through the MAF. Some of the cross-section is getting more flow and some is getting less. If proportionately more goes over the sensor itself the the mixture will be richer.
You're missing the point that the air filter is affecting the _pattern_ of the flow through the MAF. Some of the cross-section is getting more flow and some is getting less. If proportionately more goes over the sensor itself the the mixture will be richer.
do the test again, keep the engine running, and change the filter while the engine is running. upside down vs right side up will not change anything. if it does, it would be very slight. they just dont provide any restriction and all will straighten flow to the bell mouth inlet to the MAF on the filter box . flow /pressure drop is so low, its off the chart.
09-26-2012 | 01:52 PM
#33
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From: saratoga, ca
In this instance the 02 sensor is disconnected and if you go for a drive and do some logging you can see the car is rich through out due to the air filter being the wrong way.
Now with the 02 connected yes it does compensate and try to bring the A/F back to Stoich.
However, the issue comes when the car is hot and switches over from open loop to closed loop, the difference between what the actual A/F is in open loop (very rich) and what the map and 02 sensor think what the A/F ought to be is massive and the car throws a hissy fit.
When the air filter is fitted correctly none of the above occurs. However, i will try to do a log between air filter the wrong way on stock maps ( i have one from my intial tuning last month) and air filter the correct way on stock maps and report back, both will be done with the 02 sensor disconnected and nothing else changed.
I suspect what John alluded to earlier in the thread when he said he has seen at idle an incorrectly fitted stock air filter being pulled down across the MAF mouth at idle by the intake is why the problem is so noticable at idle.
None of this this has effected the performance however, the car pulls like a train up to above 150.
Now with the 02 connected yes it does compensate and try to bring the A/F back to Stoich.
However, the issue comes when the car is hot and switches over from open loop to closed loop, the difference between what the actual A/F is in open loop (very rich) and what the map and 02 sensor think what the A/F ought to be is massive and the car throws a hissy fit.
When the air filter is fitted correctly none of the above occurs. However, i will try to do a log between air filter the wrong way on stock maps ( i have one from my intial tuning last month) and air filter the correct way on stock maps and report back, both will be done with the 02 sensor disconnected and nothing else changed.
I suspect what John alluded to earlier in the thread when he said he has seen at idle an incorrectly fitted stock air filter being pulled down across the MAF mouth at idle by the intake is why the problem is so noticable at idle.
None of this this has effected the performance however, the car pulls like a train up to above 150.
if you do some of these tests, keeping the engine running, and flip over the filter, you shouldnt see any diff. again,the air flow is just so slight, already straight, and the filter element is far enough from the hot wire as to not effect flow. keep in mind , the majority of the flow is just head on . keeping the flow straight with a filter is important. as you go WOT, the air really comes in around the belmouth inlet area. the flow dynamics gets really interesting under high flow 500cfm , WOT, high rpm. at the idle rpm, the flow is very slight, and the ECU is taking inputs in from all sorts of little sensors, including the O2
09-27-2013 | 06:10 AM
#34
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Joined: Sep 2010
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From: Fresno, CA (summer in Calgary)
Resurrecting this old air filter thread,
I found that my sloppy mechanics stuffed the air filter into the box so when it shut the rubber gasket did not make any seal. It was lying the right way but no seal, the lid was partly open, air could just kind of come in anywhere. Don't ask me why the shop would put it back together like that, must have been like "let the kid do it" or something.
I fixed it and now it *seems* like I am observing improved mixture. I have a little better mileage and little more power. Or so I think. I'll have to run it a couple hundred more miles to be sure.
-Sean
I found that my sloppy mechanics stuffed the air filter into the box so when it shut the rubber gasket did not make any seal. It was lying the right way but no seal, the lid was partly open, air could just kind of come in anywhere. Don't ask me why the shop would put it back together like that, must have been like "let the kid do it" or something.
I fixed it and now it *seems* like I am observing improved mixture. I have a little better mileage and little more power. Or so I think. I'll have to run it a couple hundred more miles to be sure.
-Sean
09-27-2013 | 07:05 AM
#35
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Joined: Feb 2002
Posts: 7,056
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From: Cambridge England
Porsche carefully tuned the system to take account of the airflow patterns into the venturi of the MAF. Anything that changes the pattern of the airflow into the MAF will change the fuelling.
