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cai and short ram intakes bad. but why??


bdickey058

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Has anyone actually blew up there car or did messed it up by having one? I mean all these people talk trash about it but i have not seen proof. I guess i just dont understand. Our cars should adjust to more or less air. Hell the compute rknows when we are at different altitudes
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Has anyone actually blew up there car or did messed it up by having one? I mean all these people talk trash about it but i have not seen proof. I guess i just dont understand. Our cars should adjust to more or less air. Hell the compute rknows when we are at different altitudes

 

The problem isn't that the ECU can't adjust for the intake, but that the amount of air going into the engine can be different from how much the ECU thinks is there. An intake can end up placing the MAF sensor in a different place in the air stream than the stock location and can cause more turbulence as well making the MAF readings even more inaccurate. If the MAF isn't rescaled manually then the ECU still thinks everything is stock and adjusts things like fuel and timing according to how much air it thinks it's seeing. So basically, you end up with more air than the ECU thinks and that can result in a lean condition which can cause damage due to knock over time.

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Hey i wrote this in another thread.

 

All your sensors work off of 5.0volts max. Each 0.1 volt equals an amount of airflow. so say your stock airbox is at 4.4 volts at WOT. Np at all. Now when you put on a bigger intake with cobb ots maps or even a stock map and start taken in more air you face the chance of maxing out that 5.0 volt range. Example you could be bringin in 5.3 volts with a bigger intake but the maf cant read that. So it will only give you the fuel for 4.9 volts. Causeing a lean condition. Which in the worst case scenario could casue engine damage. When you get a map for your intake they change the values of each 0.1V so you wont max it out. Hope that helps/makes sence...

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Hey i wrote this in another thread.

 

All your sensors work off of 5.0volts max. Each 0.1 volt equals an amount of airflow. so say your stock airbox is at 4.4 volts at WOT. Np at all. Now when you put on a bigger intake with cobb ots maps or even a stock map and start taken in more air you face the chance of maxing out that 5.0 volt range. Example you could be bringin in 5.3 volts with a bigger intake but the maf cant read that. So it will only give you the fuel for 4.9 volts. Causeing a lean condition. Which in the worst case scenario could casue engine damage. When you get a map for your intake they change the values of each 0.1V so you wont max it out. Hope that helps/makes sence...

 

That's not what happens :) (well that is what happens if you install the sensor in a larger diameter housing.

 

The MAF sensor works by exposing a heated wire to the air stream and using the amount that the wire cools to calculate the amount of air (actually the mass of the air ;) ) that is passing over the wire. The issue is that the Legacy's MAF (and most MAFs) only measure the airflow over a very small portion of the intake tube. When you change the rest of the intake the airflow pattern in the tube can change, throwing off the sample that the MAF sees. It is usually worse at low flow rates, since there is more variability in how air flows through the tube when there is less of it then when you are running WOT at full load.

 

The result of all of this is that when you change things, the MAF sends a signal to the ECU that the mass of air is one amount when in fact it is another. This is pretty easy to fix when you are setting up the tune.

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This applies to all intakes, at least until you log it to see if it doesn't ;)

 

The COBB Street tuner instructions explain it very well. It is not that hard and takes only a few minutes.

 

http://www.cobbforums.com/forums/showthread.php?t=31091

 

You folks shouldn't be messing with any of this until you have read and understand their stuff - and it is all free :)

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That's not what happens :) (well that is what happens if you install the sensor in a larger diameter housing.

 

Isnt that what your doing when you put on a bigger intake?

 

pretty sure the K&N doesnt affect anything on a stock car stock tune. Feel free to correct me though.

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first off i didnt post in the other thread b/c noone really said anything in it, and this one seems to be getting a lot of replys. But i'm very interested in this stuff. eventhough i'm new to cars and dont understand a lot. But i'm willing to learn!
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How would one go about rescaling the MAF sensor? Does this apply to the AEM CAI as well? Thanks.

You can use romraider if you open source tune. You could copy your rom with ECUfash then use romraider to scale maf and update rom. Then flash the update.

Racer X FMIC for '05-'09 LGTs, '08+ WRX and '10+ LGT,'14+ FXT, and '15+ WRX TMIC Racerxengineering.com
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I have an AP protune so I assume this is something my tuner has already adjusted and/or rescaled. Thanks for the info though. :)

Did you read my signature. Log your car and you will know for sure.

Racer X FMIC for '05-'09 LGTs, '08+ WRX and '10+ LGT,'14+ FXT, and '15+ WRX TMIC Racerxengineering.com
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