heat insulation and reflection

[RoadRacer]

I've read a bunch of threads here about what to do about heat and I wanted to write my thoughts down and get some opinions.

With the exhaust running a few inches under our 33 floor (which is just a single sheet of aluminum) I figure we have a problem by default.

I've read about wrapping headers on here - but everything I read off-forum says this is a really bad idea. It'll just corrode the headers. Similar to wrapping the muffler.

But wrapping anything doesn't make sense to me anyway, because we need to get the heat out into the air, right? We can't just let things get hotter internally and hope it goes somewhere else. Doesn't sound right to me. Instead we need to dissipate and deflect the heat and specifically keep it out of the car interior.

This seems to be an opinion held by a few others, here's one (talking about a roadster):



A spaced heat shield works by having a reflective surface on both sides of the shield and a air space between it and the protected area. The shinny back side prevents re-radiation of the shields temperature into the protected area and allows an air path to cool the shield and surface being protected. Putting insulation behind the shield defeats some of the advantages the shield offers. The air gap doesn't have to be very wide but sufficient for some air circulation behind it. Because our cars have lots of air circulation around the foot boxes, the gap can be as small as .25".

As edwardb says, a good insulation on the inside of the footbox and a layer of carpet keeps most of the exhaust heat out of the interior. If you have dark color sheet metal around the exhaust pipes, a heat shield will do a lot of good. I added polished shields on the outside of my foot boxes because I like the bling and was unsure of the need.

So rather than wrapping anything, I'm thinking of insulating my floor more, perhaps double layer it, or if there's room have a heat shield above the exhaust with a gap to the floor. I don't have my exhaust yet so I'm not sure what's possible. What should I put underfloor? Something shiny and reflective, or something insulating? Wouldn't it be cool to be rich enough to use the mclaren F1 idea of covering everything in gold leaf to reflect heat? :D

Thanks for your input.

[FF33rod]

First off, let's clarify that we're talking about Gen 1 here. Gen 2 has a different floor construction and has less of an issue.
There is very little room between the standard FFR muffler and the floor. So little that I decided that there was high risk of rattles if I tried to put a heat shield in there. It probably can be done but I didn't want to spend the time on it (and likely redoing it). That lack of space and a likely lack of air flow really has me doubting the effectiveness of a shield.

So, what I've done is wrap the muffler in the pipe tape and then wrapped again in the DEI heat shield stuff. In the cockpit I used both the Heat and Sound Lizard skin products and then I've put the FFR heat and sound insulation package on top of that... The car isn't on the road yet but in the 20 minute stints that I've run it, the floor not surprisingly gets noticeably warm.

Steve

[JohnK]

But wrapping anything doesn't make sense to me anyway, because we need to get the heat out into the air, right? We can't just let things get hotter internally and hope it goes somewhere else. Doesn't sound right to me. Instead we need to dissipate and deflect the heat and specifically keep it out of the car interior.



My comment isn't specific to the 33 but rather to heat control in general. When you say that you want to get the heat out into the air rather than getting hotter internally and hoping it goes somewhere else, what that means in practice is that you're not controlling where the heat goes. If you let heat dissipate over the entire length of the exhaust, it will go exactly where you don't want it to go - into the engine compartment, foot boxes, floor boards, etc. The point of insulating the exhaust, whether it's via wrapping it or ceramic coating it, is to contain the heat in the exhaust. This does two things: 1) a hotter exhaust will have a higher exhaust gas velocity, which has performance benefits, and 2) a hotter exhaust means that heat didn't end up in the passenger compartment where you don't want it. I'm not a fan of wrapping because of corrosion concerns, but ceramic coating exhaust, IMO, is one of the most effective ways to keep the heat where you want it - in the exhaust gas. That way there's no hoping where it goes. It'll go out the tailpipe, which is where you want the heat to go.

[RoadRacer]

Great, thanks Steve and John, this is a big help. The obvious part I was missing (without stage 2) is that there isn't enough room for anything else. Perhaps zoomie exhausts (j/k) ;)

A little worrying Steve that your 3-4 layers still let heat in! Of course without it doesn't bear thinking about.

Ok, I'll rethink the wrapping with something. Thanks again.

[MonstaS4]

Like Steve, I'm trying a few different approaches. I've wrapped the pipes from the firewall to just in front of the diff. I've also ditched the FFR mufflers and cat converters are in their place (Flowmaster mufflers installed under the trunk). I've used an embossed alumininium shield over top of the cat converters which is mounted with stand-offs that keep the shield about 12mm above the cat. Theres then about 10mm clearance to the floor.

129457

I've also sprayed the underside of the floor with Bully rubber liner and the inside will have the FFR heat and insulation package.

129458

Heatshield is sold by a company here in Aus, but surely something similar is available in the US? https://www.carbuilders.com.au/aluminium-embossed-heat-shield. It's super easy to work with.
I'm still a few months away from go carting so unsure how effective all this will be.

Brad

[progmgr1]

Just curious, but were you required to add the catalytic converter due to local regulations or was it a personal choice? Due to the way they operate, cats run a lot hotter than glass packs or resonators - so your problem with heat gets a lot worse. Keith

[Kamp]

I did some tests on my Gen 1 using a temperature gun, I first wrapped a section of pipe under the floor and then measured the floor but found no difference! Next without wrapping I started to add layers of reflective foil and found that for each layer the floor temp was reduced about 6 degrees. What I used for foil is the stuff they use in retrofitting attics. The stuff I had was foil on one side and mat like material on the other. (no holes) I ended up with a layer of the attic foil and a double foil sided insulation. The floor still gets warm but at least it doesn't melt my sneakers!

I fabbed my own exhaust system and incorporated heat shields above the mufflers, I'm not sure it was worth the effort but I didn't do a measurement before and after either.

At some point I am going to refab the system using oval pipe and having them thermal coated both inside and out. This method worked well on a 32 I had.

[MonstaS4]

Just curious, but were you required to add the catalytic converter due to local regulations or was it a personal choice? Due to the way they operate, cats run a lot hotter than glass packs or resonators - so your problem with heat gets a lot worse. Keith

Our regs here in Australia stipulate manditory use of cat convertors. If it gets too hot, i may have to sneak another layer of heatshield between the cat & floor.

[JimLev]

My pipes from the header collectors were wrapped and I had the gold reflective film on the bottom of the floor (Gen1), it did little to reduce the heat on the inside just above the mufflers.
I couldn't touch the floor above the mufflers.
I then wrapped the mufflers with 2 layers of insulation. The floor just gets warm if the car has been idling for 20+ minutes.
The mufflers and pipes are all stainless so they won't rust out.

129503

First layer, same as I used on the pipes.
129505

Second layer.
129507

[Ducky2009]

I don't have a 33 but thought heat shields would help on my MK4. Some people disagree but I felt it would help. I spaced them 1/2" of the footboxes.

[RoadRacer]

My pipes from the header collectors were wrapped and I had the gold reflective film on the bottom of the floor (Gen1), it did little to reduce the heat on the inside just above the mufflers.
I couldn't touch the floor above the mufflers.
I then wrapped the mufflers with 2 layers of insulation. The floor just gets warm if the car has been idling for 20+ minutes.
The mufflers and pipes are all stainless so they won't rust out.

129503

First layer, same as I used on the pipes.
129505

Second layer.
129507

Jim, in your original post the link is broken.. https://www.amazon.com/gp/product/B00SCWJDKG/ref=od_aui_detailpages01?ie=UTF8&psc=1 - do you remember what the aluminum wrap was called? I'll keep searching.

Prhaps this one? https://www.amazon.com/Design-Engineering-050506-Non-Adhesive-Insulation/dp/B00YJERW40/ref=sr_1_20?dchild=1&keywords=DEI+muffler+insulation&qid=1591316323&sr=8-20

[JimLev]

RoadRacer, that's the one.

[Grusks]

Our regs here in Australia stipulate manditory use of cat convertors. If it gets too hot, i may have to sneak another layer of heatshield between the cat & floor.

we also need them here in the UK, looking at some heat reflective panels to fix to the floor between the aluminium sheet and exhausts components and well as wrapping the it all

https://funkmotorsport.com/product/thick-aluminium-barrier-heat-shield-0-5mm-thick-sheeting/?utm_term=&utm_source=google&utm_medium=cpc&gclid=Cj0KCQjwoPL2BRDxARIsAEMm9y-oaryMcrG3xh3uk0Hyq1O8A5u1GUjn_38O2mBQb_SMHJvQ-l1BHNUaAtzeEALw_wcB

[RoadRacer]

How much of the wrap did you guys need to wrap exhaust from firewall back, incl mufflers? I just bought 2 x 50ft rolls, but doesn't look much now it's here.

[JOP33]

How much of the wrap did you guys need to wrap exhaust from firewall back, incl mufflers? I just bought 2 x 50ft rolls, but doesn't look much now it's here.

It is really dependant upon how much (of the entire pipes) you are able to access. On mine, there were chassis tubes so tight that I had to cut, clamp and re-start on the other side of the tube, which would use more material. I didn't cover the entire system..only back to the rear end rise, and I used 2-50' rolls with excess left.