FMIC 2" Piping and BOV

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2003.5 MazdaSpeed Protege
So I'm interested in installing an ebay FMIC, specifically a CXRacing kit and am thinking about the 28"x5.5"x2.5" core (2" in/outlet) with 2" piping. I've read all about ideal setups using the 2.5" piping and even 2" hot pipe and 2.5" cold. However, I don't see the reasoning of changing the size for the cold pipe; if, by chance, there was a noticeable amount of change in volume for cold air considering it's denser, wouldn't it have less volume? It's becoming more compact. I'm imagining a 2" setup would not only work with the T25 2" compressor outlet, but be more efficient since there would be more pressure in the pipes compared to 2.5" allowing for quicker spool/peppier throttle response. My only question is the effect it would have, if any, on joining the pipes with the 2.75" MAF with that drastic of a silicone reducer. I think any flow impact would be negligible. Lastly, is there a reason there seem to be no universal 2" pipes with a BOV flange, SSQV or type S? Is it not safe to weld a flange on this size of pipe? The smallest I've seen is 2.25" from CXRacing.
 
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2003.5 MazdaSpeed Protege, 2002 Protege 5, 2003 Protege ESGT
Im sureany change in size is to allow better fitment but it kind of makes sense to have a fatter hot pipe vs cold pipe due to the difference in air temperature and density. As for the maf, having run vta for some years with a blow through maf with the diameter change your concerned about, its not really a difference in pressure/velocity you will feel.
Still id consider making a custom piping setup using cx generic pipe kits to allow you to run recirculated with an aftermarket valve oike greddy, but keep the maf in stock location pre turbo inlet. Its more efficient and the bov sound kinda gets old after some years ha
 

505zoom

Breathe
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2003 MSP #119
There will be absolutely zero noticeable difference in lag/response by going from 2.5" piping to 2".

Ideally you should match the endtanks and both sets of piping to the TB... 2.5".
 
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2003.5 MazdaSpeed Protege
Hmm this makes me wonder what the average temperature the air from the compressor outlet is and what it is after the intercooler. I hear the goal is ambient, but I'd like to hear some personal results. Zoom, any particular reason why matching the TB diameter is ideal? I can't imagine you'd get any more air if the compressor outlet can't produce enough air to use the extra space in the 2.5" piping. Maybe all the tiny differences don't amount to much performance impact.
 

thepope540

Follower, Father, Hus***d
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2003.5 Yellow Speed - Sold, Spicy - Sold, #639 Black Mica
My setups run a relocated MAF so all the piping and intercooler end tanks are 2.75". This avoids extra transitions in and out of the sensor.