Trex87

First of all, I know the stock box is the best intake for the 8. I've read a lot about all intakes but I wanted to understand more on how the injen intake supposedly loses power when it sucks in air from the stock tubing not the engine bay and it's designed similarly to the stock box? I keep reading that it sucks hot air from the engine bay but it actually has an opening in front for the stock tube behind the bumper. I was always curious, anyone with something to share about it?

04Green

iTrader: (1)

is all about the air flow, look at the horn inside the stock air box.

I have a stock box I wrapped in insulating foam and a racing beat duct. I like it. It works, and gets in cool air.

9krpmrx8

iTrader: (46)

Similar is not identical and that is critical in MAF calibration.

Steve Dallas

It's all about MAF accuracy and laminar airflow in the intake in this car. Taking air from the same location does not mean the MAF is receiving straight air at the right angles to allow it to work in a calibrated fashion.

Trex87

Ok you guys cleared it up more. What's interesting is that injen uses the stock box mesh filter where it meets the tubing by looking at its website manual. Well either way I'll just stick to my stock box, I was considering aem but didn't like the idea of its filter injecting water and the piping heat soaking. Disabling vfad did smooth out my idle and driving

Steve Dallas

There is a lot of misconception around the VFAD, and whether it affects idle or throttle response. Consider these things:

1. At idle, at ~800 RPM, the air pump (your engine) wants to draw in a fixed volume of air at a fixed velocity.
2. As long as the intake can supply that amount of air without restriction, increasing the amount of available air has no effect, because it is not demanded by the air pump.
3. Even with the VFAD closed, the amount of air available to the air pump is far greater than what it is drawing.

That means modding the VFAD to hold it open cannot reasonably be expected to improve idle performance.

Also consider these things:

1. Mazda engineers calculated that the VFAD becomes a restriction at something greater than 5500 RPM, which is why it opens at 5500 RPM.
2. Ninety percent of the average driver's time is spent below 5500 RPM, so the VFAD should mathematically be out of the way almost all the time.
3. Somewhere above 5500 RPM, the air pump demands more air than the VFAD can supply, and opening the VFAD allows the air pump to make the power it wants to make, without being starved of oxygen.

For these reasons, I am always skeptical, when I read that modding the VFAD improves throttle response. It could hurt throttle response above 5500 RPM, should it be stuck closed, however.

There is nothing wrong with modding or removing the VFAD. Hell, mine is held open. But, it probably contributes nothing beyond being a cool noisemaker.

You are right to just keep the stock airbox. It flows much more air than a normally aspirated Renesis can demand from it, and it is already a CAI, so there is no benefit to replacing it.

Trex87

Oh ok makes sense, maybe I had a tiny vacuum leak in the vfad that made it feel more responsive? Idk but I'm still chasing a vacuum leak because my maf is way too low at idle 4.3 - 4.6.

Trex87

Btw 9krpmrx8 I did the halogen headlight housing with aftermarket 5000k xenons like you. Your thread helped a lot

Reoze

I never really even noticed a difference in the noise department, never mind throttle response. I mostly ripped mine out so it would stop getting caught when I took the airbox out. Now that was worth it.

Steve Dallas

I remember reading the same thing. It is there to keep the intake quiet, until more air is demanded by the engine.