I was curious about purchasing a new intake/air filter assembly for the Jetta and I came across an interesting article regarding how the on board computer works in my car. Here is what I found.
The vehicle's engine management system takes two readings regarding airflow. The first is mass air flow which the EMS uses to calculate how much fuel it can give to the motor and not smoke (because I have a TDi). The second reading is boost pressure, the EMS uses this reading to regulate boost pressure for maintaining a specific mass air flow.
When one claims that a filter or intake helps to develop more power it can only mean one thing, some property of the filter or intake must have caused more airflow and thus, more fuel is being injected. Cramming more air into the intake must mean that you are creating more boost, however the EMS has a pre-programmed control system that regulates the engine between specified parameters. If the EMS can to maintain the specified level of mass air flow it doesn't matter how much or how little restriction there is before the turbo. The EMS will see that and use the variable nozzle (the gas throat section at the inlet) on the turbo to reduce the boost and put the airflow right back to where you were with the paper filter.
Unless you are unable to maintain the desired boost level with your current intake system a higher flow airfilter WILL NOT HELP YOU. Less restriction is less fuel, no more power at wheel but less fuel for same power.
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4 comments:
Right, but the EMS doesn't know how much force is exerted on the piston to draw the air into the cylinder in the first place.
So your gross combustion power in the cylinder (can that even be measured?) won't be affected since it's the same amount of fuel and air, but your net power (i.e., the power exerted through the crank...averaged across a revolution) will, because there won't be the additional drag on the pistons.
How much does this actually matter? Probably not at all. Driving around with your windows rolled down probably has a greater effect on your overall efficiency (i.e., ability to turn power into speed).
P.S. Bumpernuts
I 100% agree with the article - dan is confusing me tho. I remeber somehting about a boost pipe upgrade thing somewhere that's supposed to make a difference though. You know the one I'm talking about or need a link?
yup
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