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Originally Posted by Slippi84
First off I can't weld at all so i'm fucked. Second I hate to break it to you, as I have heard this argument before, If the intake got as hot as it would need to for this thick pvc pipe to slowly melt to where it's britle enoght to break off or pinch the airway opening then the coupler that comes stock with out cars along with the cheap ass ruber stock intake not to mention all the other stuff in the egine bay that's not metal would melt to. The only place in the engine bay where you wouldn't want to put something like a pvc intake is right underneath a o2 dump or wastegate dump tube or flush up against something seeing boost or extended heat like your uicp or your exhaust.
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WRONG.
First, PVC does not have to "melt" or "break" to be dangerous to your car.
Second, the rubber "accordion tube" is not raw rubber - it's a compound designed to be stable in a hot engine bay when soaked in hydrocarbons and caustic residues. The same for the plastic "snorkel tube" on the recirculation fitting. Comparing either of these to PVC is incredibly ignorant.
Do some homework - this is not a "new" idea, it's been around a very long time, and the old dsm.org even had the ABS pipe intake for the 1G as a "cheap or free" upgrade faq. Including the part numbers from Home Depot if I remember right. The thing is, you should use black ABS pipe with a high temperature rating (for hot water) or metal pipes - NOT PVC.
PVC is exactly unsuited to this application for a lot of reasons. I wont bore you with too much chemistry, but "getting brittle" and "breaking off" are realistic expectations over time. PVC and heat don't mix. This is all available in the archives, but I'll touch a few points.
The main reason not to use PVC for this stuff is it's chemistry. PVC is polyvinylchloride. That's polyesther, vinyl, and chlorine in a mixture that's designed to be stable, flexible, cheap, and lightweight. PVC reacts to heat 3 ways, and in stages. First, the compound gets soft and starts releasing chlorine gas. That's when it starts to shrink and turn either yellow or brownish, depending on the schedule and quality of the pipe. That's the part we need to worry about.
Chlorine gas attacks organic rubber, and silicone, and makes acids out of hydrocarbons (like the oil residue in your intake path). All of this is bad news. It won't usually shatter or crack until enough of the chorine has outgassed to make it brittle - and it will have discolored and shrunk noticably first. And anyone who thinks a turbo's intake housing or an engine block doesn't get hot enough to be a problem is either stupid, or just not thinking.
Radiant temps under the hood of the car will easily reach 300 degrees near the exhaust manifold or turbine housing - and any intake you build will have to be close enough to mount to the turbo so you can bet it'll be an issue.
For that matter, I've known more than one guy who replaced his "snorkel tube" with a short fitting made from PVC pipe. Bearing in mind that this is a short (3 inch) piece of pipe waaaay up by the air filter, and the only hot air it gets exposed to is the BOV aircharge, it should be fine right? WRONG. Every time, the fitting "shrunk" enough to blow out in less than a year.
Now, you may be asking why a little shrinking is a huge deal? Well, then ocnsider that chlorine is one of the most dangerous gasses on the planet, not far behind oxygen. Not just because it's poisonous, but because it attacks EVERYTHING. It will degrade any natural rubber or silicone rubber parts (like vacuum lines, couplers, and gaskets) that it's exposed to, and will bond with hydrocarbons (such as, for instance, gasoline and most of the components of motor oil), making acids which over time can attack aluminum. And the amount that the PVC shrinks is the volume of pure chlorine released into your engine.
There are high temperature PVC formulas - read the labels on the PVC, the schedule number tells you what temperature it's expected to handle before it starts to offgas chlorine. But even the best of it probably won't be available in the sizes you are talking about for an intake. Switch to metal pipe or ABS plastic if you need to do the Home Depot Racing thing. ABS has better heat resistance than PVC, and when it does degrade it does so by going hard and brittle inside itself, so melting/shattering/breaking is the only way it's dangerous when it fatigues. No toxic gas to attack your other parts.
