Exhaust manifold wrapping

[poohbah]

So I was watching the episode of the French series of Wheeler Dealers the other day where they do a light restoration on a 2.0L 116 GTV, and they wrapped the exhaust manifold with that woven exhaust tape.

I kind of liked the way it looked, and its obviously a pretty cheap and easy thing to do, but my question - is it worth doing? Or is it purely a cosmetic mod?

[Citroënbender]

I'd suggest it was done for looks, unless there was a big effort to milk every last kW on a dyno.

[poohbah]

Yeah, I am sceptical of there being much discernible benefit. I removed the ugly DIY aluminium heat shield a prior owner fitted over the manifold a while ago with no ill effects (it was always in the way whenever I had to do anything). So I agree its probably just a bit of engine dressing. The Froggy WDs really only went for tweaks and tidyups under the bonnet - replace the standard airbox with horns, clean everything up and usual replacement of plugs/leads etc. Most of work was on suspension and brakes.

[Duk]

Probably the first time I've ever heard anyone say that fibreglass tape was good looking............ 

Ceramic coatings are quite reasonably priced now a days and from all accounts quite effective. The good suppliers coat inside and outside, too.
Fibreglass tape will get grotty pretty quickly. But you can paint it with a high temperature exhaust paint to help seal the fibres and make the tape less prone to hanging onto oil and dirt. Obviously if you spill oil or brake fluid onto fibreglass insulation it's going to stink untill its all cooked away. Trouble is, there could well be a lot of it because it won't really drain away and you can't wipe away the excess. And if things got hot enough and there was enough spilt oil/brake fluid, you could have yourself a little flaming Alfa Romeo.............. 

[poohbah]

Cheers guys for the input, you've answered my questions about whether its worthwhile. One for the circular filing cabinet...

[Duk]

Those same fibres trap water from condensation or splashing and will rust your headers. And is why manufacturers wont payout a warranty if your headers rust out

I'll never understand why people wouldn't first paint the extractors/exhaust with high temperature paint before wrapping it. 
Or have the extractors/exhaust made from stainless steel, which is a poorer conductor of heat than mild steel is and then wrap it.

[Colin Edwards]

I've wrapped the rear half of my 75's exhaust with the same material in an effort to reduce heating of the RR brake caliper.  Diffcult to determine if its been effective, however it has stopped the rubber brake bleeder cap from melting!

The wrap is meant to reduce radiation / convection from the header heating up the engine bay environment.  A header with a large surface area will give up a lot of heat into the engine bay with serious long term impact on plastics and rubbers. 

If the engine bay doesnt feature a cold air inlet for the airbox, the lower temps / more dense air may improve power a tad.  Although the hotter exhaust gas will be a bit more viscous and maybe reduce power!

[Duk]

The wrap is meant to reduce radiation / convection from the header heating up the engine bay environment.  A header with a large surface area will give up a lot of heat into the engine bay with serious long term impact on plastics and rubbers. 

Yep, that's why manufacturers use heat shields to deflect the heat away from vulnerable parts and areas in the engine bay.
It's pretty stupid when people take heat shields off of their engine or out of the engine bay and claim that they're not needed.

If the engine bay doesnt feature a cold air inlet for the airbox, the lower temps / more dense air may improve power a tad.  Although the hotter exhaust gas will be a bit more viscous and maybe reduce power!

Any engine should always get its induction air from cold, higher pressure (when the car is moving) area. Always!

And an interesting point about exhaust gas temperature and gas viscosity.
In theory different temperature will change the accousitic tuning behavior of a manifold/secondary pipes or extractors and also volume and tone of the exhaust. How much you'd notice is anyones guess.
People often say that stainless steel exhaust systems sound different to mild steel exhaust. That could be because stainless doesn't conduct heat as well as mild steel, but also because stainless steels are stiffer (bend/distort less for a given force), or maybe a combination of the 2.
If you had a set of extractors and exhaust system all in mild steel and un-insulated, it would definitely sound and perform differently to the exact same (same diameter and length pipes and mufflers) stainless system that was both internally and externally ceramic coated for the entire system and then fully wrapped in insulation tape. I'd guess that the completely insulated stainless system would sound a lot 'sharper' than the mild steel system. What difference there'd be in engine performance would be hard the guess at, tho.

[poohbah]

Duk - the heat shield I removed was not a factory item, but a half-arsed DIY sheet of aluminium bolted to the battery bracket and the left inner wheel arch that sort of sat over the exhaust manifold. The only thing it appeared to be shielding from the manifold heat was the brake master reservoir, which I instead wrapped with exhaust tape. And since I've removed the shield (which also rattled like crap), I have not identified any discernible issue .

And as best I can tell, the 2.0L GTV never had a factory fitted heat shield where this one was located. In fact I have not seen a single pic anywhere of a GTV with a heat shield of this type mounted in this spot. I suspect it was fitted because the prior owner had some other problem that he thought would be fixed by it. (Perhaps he should have instead just replaced the manifold that I discovered had a massive crack in it when I bought the car.)   So it was a piece of crap and has't been missed.

[Duk]

Haha!
Poohbs, I wasn't having a dig at you, most people know the 116 cars didn't have heat shiels on their exhaust manifolds.
I was digging at people in general who do it and on any make.

[poohbah]

No problems mate, and no offence taken. I always appreciate your no-bull advice. Just wish I had your mechanical ability. 

Attached a pic of what I removed - looks better in pic than in real life. In the end I think it just directed the heat to the back and directly over the servo.

[bteoh]

There is indeed a factory heat shield on my 1986 Alfetta GTV 2.0. It was bolted onto the screw holes on the exhaust manifold and also had a factory snorkle that went from the heat shield location across the cam covers and connected to the factory airbox. Most owners may have removed it at some stage and hence might not be obvious?

[poohbah]

Cheers BT. I'd be interested to see what that looks like if you have a pic anywhere, purely out of curiosity.

[bteoh]

Hi Poohbah,
I shall do so when I get a chance. I have also removed mine as there was a slight crack in the heatshield which made a slight vibration and also the snorkle, which was made up of metal and possibly asbestos did not fit too well at the ends (Might have been some slight shrinkage). Will take a pic of those parts when I can find them in my storage bin.
Cheers

[poohbah]

cheers mate, no hurry. Sounds like it was a lot more complex than the basic one on mine.