I wrapped my "Y" pipe with fiberglass tape. It helps keep exhaust gases hot which gives throttle a smoother feel, But I learned. If you go road rallying up some canyon @ 4000 rpm for an hour or so you can melt your pipe.So I'm not recommending this mod anymore.

did you have the factory y-pipe with cat converter? I wonder if you had a custom pipe with no converter if it the y pipe would get as hot.

 

 

Bill

If you're running that hot in the pipe I bet your running very rich and have a lot of fuel burning past the exhaust valve.

 

Carb or FI? It might just be the insulating tape, but there could be more to it.

 

Gary

Ya that was my set up. I have almost all the part to make my custom "Y" pipe. Stainless steel with no cat. I just need a collector to convert 2, 1 3/4'' pipe into 1, 2'' pipe.I'm still not sure what muffler I want to use because I want to put on a spark arrester.

 

I don't think no cat would have prevented this.Because when you look into the inside of the pipe at the same place where the tape starts on the outside.The metal is white and cracked it got so hot. But as soon as the tape stops the pipe is black on the inside.I think the solution would be a thicker pipe material or something with a higher melting point.I think one of the contributing factors of the failure is.I was driving the car hard for a long time which got the pipe really hot and the I ran into some rain and I was going throught some puddles.I think the water cooled off the hot pipes too quickly causing them to crack. That's my theory.

 

I'm FI. I bet your right about the running rich.I don't think my valves are very efficient. If I gas it hard and then turn of my car I can smell unused fuel from the exhaust. I think thats where the smell is coming from.And bad gas mileage when I get on it. Might this have something to do with a bad EGR silonoid.I have never messed with my fuel mixture.How would you lean it out?

First off, running rich will cause an engine to run cooler, not hotter. Reason for this is a more controlled burn. Lean= detination=bad for exhaust temps and engine. Second, Unless your running a turbo system on an inline engine, exhaust wrap will hurt your car because the pipes hang down under your car and can absorb water and promote rusting of your pipes. In Corky Bell's Maximum Boost, he says that ceramic coating is a much better/durable solution to exhuast wrap.

Not to be argumentative but…

 

 

Glowing exhaust manifold/pipes near the head are a sure sign of an overly rich mixture. While its true that a rich mixture will provide more cooling to the cylinder wall and combustion chamber and the engine will run cooler in most cases. When the unburnt fuel is expelled from the cylinder it burns in the port/manifold and releases far more heat energy than a leaner mixture which is already starting to cool at this point. The surface area of the pipe can’t dissipate the heat quick enough and builds up heat. In fact you could have a situation with a lean burn and very high exhaust gas temps that will show much less pipe heating than the “cooler” rich mixture, because of the total energy released in the manifold. A free flowing exhaust system will show less heating because the gasses/burn are moved along quicker through the pipe and dissipate over a larger surface area. This condition is very common in turbo engines that use rich mixtures at high boost to alleviate detonation, how may pictures of red hot glowing turbos and up pipes have you seen? The heating is only really an issue if the components downstream of the exhaust valve are not designed to deal with it, or there ability to dissipate the heat is hampered, like wrapping them with insulating tape. I suspect that if the mixture were corrected that wrapping a Subie Y-pipe would do little harm, except promoting rust if left wet (as carfreak85 said), but would also yield little (if any) performance gain. Turbo cars insulate the up pipe to conserve energy/flow to the turbine, its also used to reduce under hood temps on many cars. Since the Subarus low mounted Y-pipe I don’t contribute much to the under hood heat, I really don’t see any need to insulate them unless you have an issue with them running to close to a heat sensitive component.

Gary

As Homer would say...

 

 

 

DOH!

Carfreak is, indeed, correct. Rich = cooler, Lean = hotter. If you are reading an EGT gauge and it runs hotter than it should be you are either running too lean or have large amounts of timing retard (which causes hotter than normal exhaust temperatures).

 

Also, while I could picture the exhaust manifold being easily hot enough to ignite the unburnt fuel from running overly rich, you still need air to complete the combustion process and if there were excess air onhand, you would be running "lean" and thus the unburnt fuel wouldn't be there in the first place...

damn:lol: