Just finished doing the stock airbox mod with a radiator shield. Completetly happy with it as I am saving $300 or so. However, I would like some analysis on intake surface area. I know some of you in school or in engineering can quickly help answer my question....

Question 1)

What is the maximum amt of air that the stock inlet on the turbos can support? If that is not available, how about the stock intake hose. Granted it is a function of intake pressure and temp, but I think it is important to support my second question.

Question 2)

What is the intake surface area of the K&N drop in vs. the dual apexi cone filters.


With that said the "hard" limitation is the opening in the turbos (possibly the throttle body) but we won't go into that. Stock intake tubes provide turbulance, but that is hard to measure. So perfect world which "architecture" is better?

BTW, FWIW the two supra TT drop ins seem to be about the same size as the rx7.


Keep in mind, I'm not interested in the possible limitation of the box of the stock intake as I feel I've alleviated the bottleneck.

 

How much air can the intake inlet handle? That question doesn't make a whole lot of sense. It can support any amount of air throughput. It just depends how much force there is pushing air through it. I think what you want to ask is what the pressure drop across the intake is. But its probably neglibible compared to the rest of the intake system. Just make it large and smooth as possible to support maximum air flow.

I don't know the answer to your second question, but I would bet the dual cones have more surface area.

Huh? I don't understand the question.

 

I think that the best way to look at this is to look for the smallest cross sectional area the air has to move through on its way to the turbos. As you mention, post turbo flow is all screwy to calculate cause of the boost, air density, temperature, IC bends, so forth.

You've made cut outs on the bottom of the box, right? So as you say, this is the first area you can get some help. Next miiiight be smoothing the transition the air must make as it flows into the intake hoses. For the primary especially, the air is making a tight 90 degree turn JUST after having the air filter screw with the "solid" (i.e. non-turbulated)(WTF??) air. Then it makes another bend down to the inlet elbow, then ANOTHER into the turbo. I bet anything that reduced or eliminates these bends allows the turbo to spool sooner and quicker, and flows better. Looking for straight pipe for this (instead of that ribbed stock stuff) really ought to help here too.

Secondary turbo has straighter shot, but still an abrupt transition into the hose, ribbed hose, etc reducing air that has no turbulence (read that as energy = heat = less dense = less O2 for the turbos to squeeze.)

Those are my two brain cells worth. Not much upon reading through it...