Exhaust wrap?

[PobodY]

The date is quickly approaching for my new exhaust to be built and installed, so I was thinking about what I could do to get the most out of it.

I like the idea of wrapping it, but some google research has left me uncertain as to whether this is smart on 304 grade pipework... so obviously I'll take the advice of people I trust rather than random knobs on other forums.

(I like the idea of ceramic coating even more before anyone suggests it, but after paying for the exhaust I'm not sure my budget would stretch to ceramic coatings... and I've already got some wrap.)

There seems to be two schools of thought:

1. Wrapping stainless (or mild steel; people are a little inconsistent about which one you can and can't) causes it to get too hot and degrade. - I guess the logic is that you get a phase change in the steel and without quenching it you lose the morphology and it becomes brittle?
   This seems to be the main reason people claim their new (cheap?) stainless manifold cracked.
2. Wrapping stainless is a good thing because it takes the under bonnet heat away and keeps all the gases moving fast (and thereby improving throttle and turbo response).

Some people say that the wrap causes the exhaust to corrode more quickly. - I personally don't believe any of the theories about wet wrap causing rust since it will dry pretty quickly once the exhaust gets to temperature... but I could believe that the higher pipe temperatures lead to more oxidation of the metal.
Also if you've got chloride present, there is something like accelerated pitting attack in steels at temperature which might result in premature failure (probably more around welds than anything else).

I had the mild steel front pipe wrapped on the old exhaust (although it never lasts that long) and I initially thought that was what had caused it to rust through at the hanger. However I noticed the back box was more rusted and the centre pipe was just starting to leak where the hangers are welded to that too. - My conclusion is that wrapping the exhaust didn't make the system rust quicker, but maybe I don't run the car hot and hard enough for it to make any difference.

So is there any quantifiable science here or is it just hearsay and conjecture? - If there's no real benefit I'll save myself the effort, and if it does more harm than good I'll definitely avoid it.

One last thing. - I noticed that on some of the forums I looked at people suggested wrapping mufflers; not to keep the heat down under their boot, but to reduce the noise.
That might be a top tip for people who want to keep their bore, but take some of the noise out?

 

[Fast Guy]

Mild steel rusts end of. My CES dump pipe has fallen to bits lol and it wasn't wrapped.
I wrapped the cast iron manifold on my old montego and it didn't fall to bits.

What exhaust have you got now? Is it just the manifold you're looking at doing?

 

[fubar andy]

I've had my cast manifold and 3" downpipe wrapped for the last 5 years.

So far so good

Not noticed any gains, but under bonnet temps are lower

 

[PobodY]

I'm not looking to wrap the manifold unless there's a reason to take it off; it's just the downpipe and/or anywhere that might benefit from some sound deadening at this stage.

The current system is 2.5" mild steel from the elbow-back with a twin-exit back box. - I bought it of Channy, but I think it was Jim's originally; it's probably done about 5 years on my car now and served me reasonably well over that time... but it needed some fire gum to get it through the last MOT and when the car was up on the ramps to get the alignment adjusted I could see that the centre section had stated to blow where the hangers are welded on.

Rather than arse about trying to fix all the holes and the back box which has come away from the pipe at the welds, I've convinced my wife it would be more cost effective to have a new stainless system built. - If I'm honest, I'm a little unsure what I'm getting; I told him that I would like a better flowing exhaust, but reasonably quiet so that my wife doesn't complain (and the constabulary take no interest in me). I've talked about a 3" system from the turbo back and said that I want rid of the elbow... and I hope that's what I'll be getting.
The guy is a Powerflow dealer, and whilst reviews on the internet are hit and miss for Powerflow he personally seems to get a good review. - The problem is that he's hard to get hold of; doesn't respond to emails (or not a particularly verbose response) and calls tend to go to voice mail. I figure that means he's flat-out building exhausts and if he's got that much business his work must be good.

Back on the original topic; I'm really just trying to work out if I'd get more out of my exhaust by wrapping it or if it's just a wasted effort on my car. - Maybe I should ask the builder; I don't want to do something stupid like void my lifetime warranty.

 

[Fast Guy]

The idea of wrapping the manifold is to keep the heat in the exhaust until it reaches the turbo to make the turbo more efficient. I'm not sure if there's much point wrapping the downpipe although I guess it might keep a little heat out of the oil as it goes under the sump and possibly keep a bit of heat away from the alternator. Whether you gain any power or not by just doing the downpipe I'm not convinced. There's an argument that it keeps the gases hotter and therefore they flow faster and helps with exhaust scavenging but the turbo in theory should take most of the energy out of the gases so there not much to play with.

 

[PobodY]

That's actually the reason I wrapped the downpipe before; to keep heat away from the oil pan etc. - I think I'll hold-off since I probably don't want to pull the new exhaust apart to wrap it just after it has been installed.

I suspect that it works in theory, and there may technically be a benefit... but it's not actually big enough to notice in reality.

I was interesting in dispelling some of the myths about wrapping exhausts; we've got some pretty clued-up members.

 

[campbellju]

I've had my cast manifold and 3" downpipe wrapped for the last 5 years.

So far so good

Not noticed any gains, but under bonnet temps are lower

Same install and results as Andy. It's a bit of a mess around but on balance a good thing to keep the engine bay cooler

 

[PobodY]

I'll probably wrap the new exhaust, but maybe not straight away.

What products/tips do people recommend to keep the wrap effective and in place?

The stuff I've used previously (and still have) might not actually be for car exhausts. - It's flexible and seems like an insulator, but maybe it's meant for pipe lagging and chimneys rather than car exhausts. The chances are good that I bought whatever was the best value at the time rather than the best quality.

I've seen some people say you should spray it once it's applied?

 

[fubar andy]

All I did was buy 1000oC wrap from eBay (decent supplier) bought some separate metal clips/tie from a motorsport supplier (eBay clips are crap quality)

I dunked the (unraveled) wrap in water, carefully wrapped the lagging tightly around the pipe and overlapping each turn.

Clamped the ends with the metal ties and left to dry.

24hrs later I turned the car on, the wrap smoked a little and then it was fine!

 

[warpspeed]

I wrap my exhaust wrap with metal foil tape, holds it in place, stops it getting wet again and holding moisture and also even more insulation properties, smokes for a wee bit when it's new though..

 

[PobodY]

That's a good idea; I guess it doesn't need to be the whole length, but it would give protection to the wrap and hold it place.