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A1337STI · 2006-03-01, 06:53 PM

(again an old thread but it raised a question for me)

i have an air intake kit. (K&N short ram air like on my sig) . and yes the MAF sensor is now on a K&N tube which is slightly larger then then the stock tubing. (i also reset the cpu of the car by disconnecting the battery during the install) .
Now if the air intake kit allows more air , but it 'tricks' the MAF sensor into thikning that slightly less air is going by, then ecu then uses slightly less fuel then it really should,
now i'm no rocket scientists but i took some chem and physics. if you fool the ecu into using less fuel then it should, (known as running lean) all the fuel burns, and there is left over O2 . If this is the same amount of fuel that is burned before, and 1 piston firing should produce (picking a number for examples) 100 nuetons of force.
the new configuration should also produce 100 nuetons of force, IF the same amount of fuel gets burned.
If less fuel gets burned , it should produce < 100 nuetons of force. OKay it clear to see why that would produce LESS power. how on earth is producing LESS power going to cuase harm, (or addtional wear and tear ) on the engine?

i could see an increased risk of engine knock if the pressure in the cylinder was increased from the previous pressure (more air molecures, under the same compression ratio = more pressure, once compressed) and if that pressure exceded the limit for your air Temp + octane combo, you get engine knock. is it really let THAT much more air in? (and its na until you are in the turbo) once i'm into the turbo boost i'm limited in how much air it can Stuff into the engine by the max air flow rate of that turbo, minus air resitance of the entire air-intake flow.

did subaru dial that exact post turbo air flow rate in so closely that any increase (cuased by reducing resitance) will cuase it to over boost and destroy?

i've actually increased my gas milage since i put the kit on. which tells me the car is producing more power, per gallon of gas, then before. (as the resistance for distance traveled hasn't changed any)

??? either i'm missing something, or an air intake kit really won't cuase damage to your motor. if the air intake kit fools your MAF sensor too much, it should decrease your gas milage. ?? no ?
something must be wrong with my logic here, or i'm ignorant to some Key fact that ties it all together.

please help me out

thanks

on my WRX changing from the paper filter to a K&N replacement filter raise me 3.5 mpg (no ski rack) (i record all milage and all Fuel ups changes to tires, ski rack on / off, etc) my STI has the short ram air, and i only am doing 1 mpg better. (ski rack on) the % changes are a lil closer. the wrx went from 20 to 23.5 my STI went from 17.8 to 18.8 . the wrx paper filter was dirty at the time of upgrade (that's sure to skew results)

2006-03-01, 06:53 PM	#23
A1337STI EJ205 Join Date: Jan 2006 Location: Reno, NV Posts: 1,840 Car: Impreza and an Impreza Class: AS / CRS PerfStock "pedal on the right"	(again an old thread but it raised a question for me) i have an air intake kit. (K&N short ram air like on my sig) . and yes the MAF sensor is now on a K&N tube which is slightly larger then then the stock tubing. (i also reset the cpu of the car by disconnecting the battery during the install) . Now if the air intake kit allows more air , but it 'tricks' the MAF sensor into thikning that slightly less air is going by, then ecu then uses slightly less fuel then it really should, now i'm no rocket scientists but i took some chem and physics. if you fool the ecu into using less fuel then it should, (known as running lean) all the fuel burns, and there is left over O2 . If this is the same amount of fuel that is burned before, and 1 piston firing should produce (picking a number for examples) 100 nuetons of force. the new configuration should also produce 100 nuetons of force, IF the same amount of fuel gets burned. If less fuel gets burned , it should produce < 100 nuetons of force. OKay it clear to see why that would produce LESS power. how on earth is producing LESS power going to cuase harm, (or addtional wear and tear ) on the engine? i could see an increased risk of engine knock if the pressure in the cylinder was increased from the previous pressure (more air molecures, under the same compression ratio = more pressure, once compressed) and if that pressure exceded the limit for your air Temp + octane combo, you get engine knock. is it really let THAT much more air in? (and its na until you are in the turbo) once i'm into the turbo boost i'm limited in how much air it can Stuff into the engine by the max air flow rate of that turbo, minus air resitance of the entire air-intake flow. did subaru dial that exact post turbo air flow rate in so closely that any increase (cuased by reducing resitance) will cuase it to over boost and destroy? i've actually increased my gas milage since i put the kit on. which tells me the car is producing more power, per gallon of gas, then before. (as the resistance for distance traveled hasn't changed any) ??? either i'm missing something, or an air intake kit really won't cuase damage to your motor. if the air intake kit fools your MAF sensor too much, it should decrease your gas milage. ?? no ? something must be wrong with my logic here, or i'm ignorant to some Key fact that ties it all together. please help me out thanks on my WRX changing from the paper filter to a K&N replacement filter raise me 3.5 mpg (no ski rack) (i record all milage and all Fuel ups changes to tires, ski rack on / off, etc) my STI has the short ram air, and i only am doing 1 mpg better. (ski rack on) the % changes are a lil closer. the wrx went from 20 to 23.5 my STI went from 17.8 to 18.8 . the wrx paper filter was dirty at the time of upgrade (that's sure to skew results) Last edited by A1337STI; 2006-03-01 at 06:56 PM.