This is a great write-up, very thorough, thanks for taking the time. I have the Mountune air box which came with the MP215 kit. My understanding is that this is identical to the ST200 box, except that it's made out of metal instead of plastic. I believe that Ron had confirmed that somewhere in this or another thread.
Just for clarification, since your pictures show that you designed an ST200-type box, would all the good news that you are reporting for intake temperatures and therefore performance apply to the factory ST200 box and therefore to the functionally identical MP215 box? That seems to be what you're saying, but I just thought I'd be sure.
Thanks again for your time doing this.
Short answer: Yes.
Some detail and feedback.
I just took a look at the Mountune, and have just done some further reading through some other ST200 box chatter (I'm new to the forum). Someone posted that Ford & Mountune worked together on this box, that seems very plausible, and makes sense. I wouldn't debate that they look the same, they do.
From the photos, the only difference I see between the ST200 and Mountune is the material used for the lower box. They both utilize the OEM upper cover with a drop in, and the stock upper cover has a bell mouth entrance, that's critical to entrance loss, same reason all jet engines have a bell mouth entrance, what racers call a "velocity stack." There will be some very small difference in heat transfer into the air due to the bottom of the box being different materials, they have different heat transfer coefficients (like drag coefficient). I know Ron has called the Mountune an oven. However, I'd be willing to bet you wouldn't see the difference in the Temp rise in a back-to-back test. The intake air flow rate is dominant, as you can see Temps drop as RPM increases, or with time increase at low speed. I expect the difference would be within run to run variability. Especially steady-state or soaked/cruising, maybe a small difference transiently. And like I mentioned, when cruising at lower speed, the Temp rise is really low, typically within 5F, unless it's really hot and the road is hot, etc., even then still within 7-8F. I was stoked when I first got the secondary circuit plumbed to the fog light bell mouth, took a spin and watched Intake temp on the AP3!
I would be very happy with the ST200 or Mountune. I'm not fully aware of what's out there, but these designs are going after exactly what they should be, and is why with my background I got there in a matter of minutes after taking my lower box out and seeing the min area feeding the box!!! Great idea to draw ambient air, but too restrictive.
I got lucky... I got the Cobb last Nov. I understand stock class concerns, and stealth, but that's in my past. The Cobb is a great design on the upper half, has a bigger filter with a bigger bell mouth entrance, so velocity is down a bit, lowering loss. It also has a single piece induction and crossover all 3". With the lower box mod, or the ST200 lower, I'd bet it's the best. However, I wouldn't be surprised if the loss is only marginally better than a ST200 or Mountune. That's the pressure piece. Temperature-wise I expect them to all be a wash.
I do recommend plumbing to the fog light, with a bell mouth entrance. It provides some Ram, and sucks 100% ambient air. The fender well is not a bad option (I'd still do a bell mouth in there on the end of the hose), but no Ram and it will see some temp soak above ambient. I wouldn't go without a hose, I showed those results. Even the type of hose will make a small difference. I used some plastic 2.5" vacuum hose as I was mocking up the config. Good for testing, but not a great final choice, terrible flow path. The silicone brake duct is the best I found, and cheap on ebay.
I think there may be similar configs out there that are similar performers, but I honestly don't think you can do better than these. I'm done with my intake, I think it's fully optimized.
![[:(]](/images/smilies/frown.png "Frown [:(]")
When I looked under this area the other day, it does look pretty tight with the windshield washer tank (so I worried about hose kinking/tight bends), your approach seems to solve that nicely.
