the material won't corrode the pipe, but the water it traps and holds against the pipe can tend to do this more than the pipe would if it were unwrapped. It's a tradeoff.

Also be advised that cloth type heat wraps will soak up any leaking/spilled oil and can lead to larger fires rather than burning off the oil quickly as it might on a bare pipe.

 

I wrapped my Invidia DP a long time ago (like over 30,000 miles ago- over a year and 1/2) and it still looks to be in good shape. It's not the wrap, itself, that causes the corrosion. Rather, the wrap will hold moisture in between the metal and wrap, creating a nice environment for rusting. However, if you drive the car everyday, the heat will quickly evaporate whatever water is under the wrap. Rust shouldn't be much of a concern in a daily driven car. The cars that are stored for winter (why anyone would store their AWD STi in winter is beyond me, but it happens) would probably be the ones to have problems.

Another thing is that most quality aftermarket DPs are made of 304 or 321 stainless, which has a MUCH lower propensity to rust than regular exhaust pipe steel.

The only other thing to consider is heat related fatigue. When you wrap the DP (or headers), the heat is essentially 'trapped' in the metal. This will shorten its life and eventually cause cracks. How this translates to real world life-span is a guess (as I stated above, mine looks fine).

Wrapping the downpipe (along with the StaticX turbo wrap kit and modified stock heatshield) has DRAMATICALLY cut down on underhood temps and subsequent intercooler heatsoak.

Just be aware that you will eventually have to rewrap the DP, as the heat wrap will degrade/rot after a period of time and use. It took me over a year before my wrap disintegrated.

Bryan

EDIT: Xman: that flash vid was great! I agree, I think every new forum member should be REQUIRED to watch that before posting.

 

Ok. Makes more sense now about moisture being the main cause for corrosion. It does sound like no matter how you slice it there will be either eventual heat stress on the metal and or detioration of the wrap itself which lends itself to re-wrapping. I guess now I gotta decide if cooler underhood temps is worth the extra trouble. Also the chance for an underhood fire does bother me a bit.

 

I recently wrapped my Cobb DP and added the Cusco heatshield. It definitely made a difference in underhood temperatures. Once you wrap the pipe you should coat it with the high temp silicone spray. This is suppose to keep water and such out of the wrap and help keep the pipe from corroding.

 

I, personally, think it's worth it. It's cheap and effective. As for the oil and fire issue, the only way oil's going to get onto your DP is if you pour it on there or the turbo oil feed line goes bye-bye. Neither are likely. Wrapping your exhaust manifold is a different story, though (as added oil can drip down the block, and there are numberous potential places where oil can leak from and drip onto your manifold). You can get 50ft of wrap for 30$ on ebay, which is enough to do probably 10 downpipes.

 

good info, anyone one have gone through several winter with their DP heat wrap?