Insulating Downpipes

[bcmc33]

Has anyone wrapped the exhaust manifold to reduce underbonnet heat for the purpose of giving some protection to the engine mount and maybe the alternator/dynamo?

I?ve just taken the silencer off to get it rebuilt next week and the ?Y? piece to get a Lambda boss fitted in anticipation of going FI over the winter.

It was only when I fitted new engine mounts a couple of months ago did I realise just how close the downpipe is to the LH engine mount. Also one of the pipes is extremely close to the bodywork, and that?s when I thought that wrapping the downpipes might be a good idea.

I am aware of the theory behind insulating downpipes ? so that could be a bonus.

I will check with the silencer guy next week to find-out if hotter gases would compramise the silencer ? but still thought it may be a suitable discussion subject for the forum.

[miked]

Brian,

I did it to my standard S4 road Elan on Strombergs about 4 years ago. It made lot of difference to the under bonnet temperature. I was bothered about prox' to the glass. Also did the reflective stick on stuff. If the motor comes out again, I will do a proper plate like shown on here some year ago.

Just used Demon Tweaks stuff and painted it black.

No ill effect, to my knowledge.

Mike

[SADLOTUS]

Hi bcmc

Have you thought about cermachrome?

http://www.camcoat.com/4.Anti-Corrosion ... osion.html

Had mine done and although it is supposed to, I cant detect/notice/remember any temp difference, but the manifold will supposedly outlive the car - and me.

Also, had RSR build me a stainless silencer - lovely job.

[Jason1]

Frost sell a wrap if you are looking for a UK supplier?

Price inc vat: ?50.89


http://www.frost.co.uk/item_Detail.asp? ... at=Exhaust

If you are looking for a high temp paint:

Price inc vat: ?14.19


http://www.frost.co.uk/item_Detail.asp? ... t=Eastwood

[ppnelan]

I did it to my standard S4 road Elan on Strombergs about 4 years ago. It made lot of difference to the under bonnet temperature.

Mike, how far down did you wrap it? I have considered doing this, but I don't want to cook the slave cylinder (any further!) or set fire to the floor... Mind you, with current outdoor temperatures I'm at the other extreme with a bit of cardboard box blocking off the radiator...

Matthew

[rdssdi]

I purchased a reflective heat shield which was pressure sensitive "peel and stick" and applied in the footwell area. It was made for outside application and will withstand up to 1000 deg. or more. I cannot remember what it is called. I will have to look through my huge pile of receipts. The heat from the headers will destroy the fiberglass.

Bob

[memini55]

Sadlotus,

What is the strange motor mount in your picture???
Is that something used with the spider chasis as I have not seen that type of mounting before.

Sorry to change the subject.

Mark

[SADLOTUS]

Mark

Yes that's a Spyder engine mount.

Paul

[cabc26b]

Hello Brian -

I have used a number of steps for heat abatement.

I don't like the look of the wrap, so I ceramic coat or "jet" coat the header .

Depending on the header routing I have also wrapped the motor mount with insulation- either header wrap or the glass weave with reflective backing.

I insulate the foot box area.

On the stock clutch/slave cylinder - I make sure I am careful with the routing of the center pipe and the clutch hose ( use aeroquip along with fire-sleeve)

last two cars have had annular release and so less worry about cooking the parts. You also have better options on hose routing.

George

[miked]

Mathew,

I just wrapped from the back of the cyl' head flanges to where the pipes join each other (not on the common part). It was stinking hot at that side. I even did a bit of surgery on the glass bump in that area as (cut it off and re did) I only had about 8mm of clearance. This gave me more clearance and also allowed the wrapping. I was concerned about the fire hazard of the glass with the close prox'. This was at restoration, when I got it (sat for 13 yrs). The glass was well shot with years of heat abuse. It fell apart anyway.
I must admit I did not really think about more heat at the clutch slave cylinder. I just changed the rubber seal on this after 5 years of use. They had swelled a bit and there was drip. Still working fine. I dont know whether this was due to heat. Such is the closeness anyway, I think we are up against the odds when sat in traffic. I also put my fan on!

Re: Pipe undeneath, I never have any hot glass smell when stuck in traffic on extreme hot days. I used to from the engine bay before I wrapped it though.

As I understand the increase in temperature at this area allows (less dense) gasses to exit faster. Others on here will know far more than I do. All I know is that when I lift the bonnet it is no longer a fire risk. Perhaps my manifold is built a bit differently and gives less clearance.

Mike

[bcmc33]

It?s the side bump in the footwell that?s close to my downpipe and the glass in that area does not look too clever. I?ve already decided to remove the manifold and cut-out the bump and then put some Heatwrap in that area.
I shall also make a cover for the engine mount and cover that with Heatwrap.

I shall give some thought wrapping the downpipes before reassembly.

[msd1107]

Re: Temperature of exhaust gasses leading to better flow.

The place to start this is in the cylinder head. There are specialists who can supply thermal barrier coatings for the piston head (ceramic or nickle) and also the cylinder head and port. This cuts down the heat loss to the coolant, a boon to our marginal radiators. It also increases the temperature of the exhaust gasses since more heat is retained. If the temperature increases 40 C, this decreases the Mach value through the valves and ports by about 3%. On a modified engine with standard size exhaust pipes, this would provide a small but noticable increase power.

The hotter exhaust gasses need to be insulated once outside the cylinder head. Thermal wraps, thermal barrier paints or coatings would serve the purpose and would decrease the heat load underhood and next to fiberglass parts.

Then, in theory, the increased energy could be converted in the exhaust system to a greater negative scavenging pressure for more power, over at least part of the rev range.

Sounds like an interesting project for one with more dollars than sense! And it should be noted that different experts are divided in their assessment of the benefits of thermal barrier coatings on pistons

David
1968 36/7988

[jkolb]

On my Exige S I had the interior of the manifold coated with the same ceramic they use for piston tops and combustion chambers. The outside was then coated with the conventional aluminum look ceramic. The combination made a HUGE difference in temperature. The Exige has very little extra room in the engine bay and the same routing problem by an engine mount. Manifold is now cool enough to touch within minutes of shut down.
Cost was $100US and I will be doing the same to my Elan as soon as I choose a header.

Jerry

[steveww]

I have also removed the bump from the footwell near the exhaust manifold. I went for a belt and braces approach, using a thermal spray on coating and the insulating wrap see http://www.steveww.org/index.php?id=131 I also put some of that stick heat reflective sheet on fibreglass in the manifold area.

For the clutch slave cylinder I made a heat shield out some aluminium sheet.

[sinkyb17]

Insulating down pipes does work but you have to be very carefull of the amount of overlap you give the insulating material. If you overlap by more than 3/4 of the width of the tape you can end up with the same situation I had on my car where the wrapping becomes so efficient it traps too much heat in the exhaust which results in running on and more often than not a large backfire, (remember just because you have switched off the ignition does not mean the engine will automatically stop, if sufficient heat is present in the exhaust system or elsewhere it will ignite petrol still being drawn into the engine while it is turning after switching off) The correct amount of overlap I have subsequently used is only 1/4 of the width of the tape, and the problem disapeared.

Dave

1964 S2, Austin Healey 3000