Fenderwell CAI changes AFR - Ford Mustang Forum
 
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post #1 of 8 (permalink) Old 01-15-2011 Thread Starter
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Fenderwell CAI changes AFR

FYI to you guys, if you use a CAI which leaves the MAF in the engine bay, but puts the filter in the fender, you are changing the reading your MAF will see. This is FACT. You are changing the velocity of the air as it passes by the meter.

Look at C&L's page here with airflow vs voltage tests with different filter setups:
How a Mass Air Flow Sensor Works

It shows that on foxbodies, the factory panel filter airbox is equivalent to a fenderwell CAI. Then it shows that putting a cone filter directly on the MAF will lean out the AFR by 10% to 15%. So it our case, we already have factory cone filter on the MAF. If we move the filter away from the MAF (fenderwell), we would be doing the inverse of the above example, and richening the car.

Maybe for some people this may add some power, maybe some subtract. Maybe stay the same. Might be a slight mileage decrease with being richer. Every car with different mods would be different. Maybe you like the look and you don't car if you loose a few horse.

Just food for thought. That is all.

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post #2 of 8 (permalink) Old 01-15-2011
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do you think maybe the slightly denser air from outside the engine bay offsets the slightly richer fuel pulse?
also kind of makes me wonder how big(if any) of a difference in density there is on a warm engine bay and the outside air..


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post #3 of 8 (permalink) Old 01-15-2011 Thread Starter
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Quote:
Originally Posted by Markstang690 View Post
do you think maybe the slightly denser air from outside the engine bay offsets the slightly richer fuel pulse?
also kind of makes me wonder how big(if any) of a difference in density there is on a warm engine bay and the outside air..
Factory setup with silencer is already cold air from outside the engine bay.
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post #4 of 8 (permalink) Old 01-16-2011
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This is why I attest to the fact that CAIs in most cases are just for looks.
Having said that, 05+ with a tune are a different.
post #5 of 8 (permalink) Old 01-16-2011
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Lucky for us this isn't the fox body section of the forum...

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post #6 of 8 (permalink) Old 01-16-2011
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Quote:
Originally Posted by metalman302 View Post
FYI to you guys, if you use a CAI which leaves the MAF in the engine bay, but puts the filter in the fender, you are changing the reading your MAF will see. This is FACT. You are changing the velocity of the air as it passes by the meter.

Look at C&L's page here with airflow vs voltage tests with different filter setups:
How a Mass Air Flow Sensor Works

It shows that on foxbodies, the factory panel filter airbox is equivalent to a fenderwell CAI. Then it shows that putting a cone filter directly on the MAF will lean out the AFR by 10% to 15%. So it our case, we already have factory cone filter on the MAF. If we move the filter away from the MAF (fenderwell), we would be doing the inverse of the above example, and richening the car.

Maybe for some people this may add some power, maybe some subtract. Maybe stay the same. Might be a slight mileage decrease with being richer. Every car with different mods would be different. Maybe you like the look and you don't car if you loose a few horse.

Just food for thought. That is all.
That is correct. However, our vehicles also have the capability to adjust A/F by monitoring the O2 sensors. This is not the old Foxbody technology. That's why we tell everyone to disconnect the battery when first installing a CAI unit. It will be different, but still within the parameters of the computer to adjust A/F........

It is a good article, and good reading for anyone who seeks more knowledge......

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post #7 of 8 (permalink) Old 01-16-2011
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a good point the article makes is the piping immediately before the sensor should be straight for like 6-8 inches, otherwise it doesnt have a steady density across the diameter of the pipe.. but even so, it'd still work fine i bet..

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Best 1/4 time: 15.036 @90.92mph, 2.148 60'
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post #8 of 8 (permalink) Old 01-17-2011 Thread Starter
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Quote:
Originally Posted by ESG-642T View Post
Lucky for us this isn't the fox body section of the forum...
Did you even read it? Airflow is airflow. If SN's had a tongue style sensing element (like the LMAF) that was not affected by velocity then you would have a valid point. But SN's use the same sensing element as foxes. Therefore the same principles apply.

Quote:
Originally Posted by shinerstang View Post
That is correct. However, our vehicles also have the capability to adjust A/F by monitoring the O2 sensors. This is not the old Foxbody technology. That's why we tell everyone to disconnect the battery when first installing a CAI unit. It will be different, but still within the parameters of the computer to adjust A/F........

It is a good article, and good reading for anyone who seeks more knowledge......
Good point, that would probably negate any potential mileage effect. Foxes do that too btw. BUT it will only correct it in closed loop. At WOT open loop it will not be looking at the O2s anyways and will use baseline tables. Right? I don't think that the OBDII tuning is THAT different than the old stuff... they did add engine Load calculations that were not there before.
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