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2016 Mazda 6 Touring AT
369 Posts
First, I want to commend @Zeffer for a nice write up and a cool way to mitigate some of the drawbacks of an SRI (get cooler air). It's actually got me thinking about how to route more cool air to my intake.

I also commend Mazda for how well the stock setup works, truly it is well engineered and staying within there parameters (quietness & budget) it cannot be beat.
All due respect @tickerguy, and I do respect/appreciate all the data you bring into the discussion, rightly pointing out that the stock setup is quite impressive, but your arguments are only capturing a part of what is happening and thus leading to only partially correct conclusions.

The problem is quantifying performance of an air intake purely based on peak flow is not measuring lots of other mechanisms that are at play. In any engine, and especially the Skyactiv 'Miller cycle', there are pulses from the valves opening/closing and there is turbulence. One of the reasons for a cone shaped filter is the effect it can have on shaping air flow and affecting flow dynamics. One reason for SRIs not helping in the low end is because the Miller cycle generates stronger pulses (from the intake valve staying open during compression) and if there is not as much air mass coming into the engine (short tube, smooth tube) then the pulses can momentarily stall the incoming air charge, creating worse turbulence at lower RPM. So, if the SRI has better flow characteristics (and you mitigate the heat issue) then at lower RPM it's net gain or loss of nothing, but at higher RPM where the pulses from the intake valve are shorter then the SRI is no longer at any disadvantage and flexes it's flow.

In my case, I went with the Injen CAI (with Hydrosock) and love the gain in power & responsiveness across all RPMs. In fact a few weeks ago I put the stock intake back on to see how it felt, but took it off the next day because I missed the low end power and reduced throttle latency from better flow characteristics.

About the ECU, this Skyactiv ECU is awesome IMO, and if you change anything about your engine I highly recommend resetting the computer in some way (clear DTCs, disconnect battery for a while, etc.) to get it to re-learn how it's operating. This ECU has a hard-coded base RANGE of operation (known as the "tune"), then it has the adaptive part that essentially runs in RAM which adjusts to how the system is operating (obviously there is a limit to how much the ECU will adapt, but I've experienced this engine running worse after changing something, until I disconnected the battery for a while).

Intake does not happen in a void: In my experience airflow related improvements tend to compound each other. If you do nothing else to your car but put a better flowing intake the difference will be very minor, and if you do nothing but put a better flowing muffler the difference will be very minor, but both together will have a little extra effect because having air flow out more easily will help more flow in. Also getting a tune that is more aggressive means you generating more power, and leveraging the small flow gains even more.

About Dynos, the reality is I'm likely never going to waste the money on a Dyno as that same money could pay for two days of Autocross!!!.
I also don't think a Dyno is a good way to measure the overall impact of good changes to Intake/Exhaust. A better way to quantify it would be to do a series of timed runs on a track with each set up (it would have to be a lot of runs, where you through out high and low times, then average the rest), because in my experience the difference in 0-60 WOT is not nearly as big compared to the difference in throttle responsiveness in the real world and the effect on lap times!
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