With obviously too much time on my hands, and having to remove the airbox to access the leaky thermostat , I decided to complete a mod I'd thought about for a while. As we all know, the Alta CAI makes great noises, but is made of metal which conducts the engine bay heat pretty well. Having used insulation I thought I'd go one up, and build a double-walled airbox. Here it is:



This is before I applied a layer of fiberglass insulation over the outside.
Q: any suggestions for a higher R-factor filler than air? The gap is 1/4" on the two surfaces.
Car isn't running so can't provide data, but that will be forthcoming with impressions.

 

How about insulation in between the two metal layers?

I see a hole cutout for the MCS battery plus terminal- a potential area for heat to leak in.

What about a cover for the top? Dual layered of course!

With the car after driving you can check the delta in temps from inside metal to outside layer metal.

 

Yeh, that was my question: I was thinking of that expanding foam that you get at Home Depot. Fiberglass would be too messy to install and wouldn't provide much R-factor at 1/4" The final product has Al-clad fiberglass sealing all the openings, just for the reason you mention--the R-factor disappears if the air in the gap gets under-bonnet ambient.

 

This is quite impressive, I cannot wait to see it finished! I would love to see DDM or others build this, but they would likely charge another $100+ to have this option.

 

Nice Phil. You're just passing the time until the header comes in? That's great because we get threads like this.

Anyway, go to http://www.mcmaster.com/ under "Raw Materials" there is thermal insulation. I'm sure there is something you can use there.

 

why not just get a bunch of M7 aerogel pads and stick in the gaps? (besides the fact it's expensive)

 

Hey nice mod! My two cents. Leave the air gap instead of filling it. If the goal is to reduce soak and or transfer, placing media in between might ruin some of the effect. Just like at heat shield has air between the heat source and the shield. The air acts as the insulate. I would be fearful of a solid insulate to then transfer the heat back. Or a very loosely packed media might work too.

Keep us posted!

 

One of the UK MINI aftermarket vendors (I can't find the link at the moment) sells a twin wall intake. There is no insulation between the walls, I think they actually force some air through that gap.

There are many options for heat relflective materials. One that I have seen used in a Honda application is from Design Engineering Services, http://www.designengineering.com/pro...sp?m=sp&pid=28. Its thin, self-adhesive and not expensive.

 

another option - Subaru puts a plastic honeycomb liner around the battery to insulate against engine heat. I think it would fit that gap perfectly and be a good insulator (and cheap!). Let me find a pic...

 

Absolutely awesome idea!! what would be an "ideal" solution would be to have that gap between the walls sealed airtight with nitrogen or something similar in that space like thermal insulated windows. The windows use 2 or 3 or more layers of glass with nitrogen between the layers. There's also other things to put in there that have almost zero heat transfer. Just dont see how to keep the "air" or whatever is in that space from eventually reaching ambient without some sort of circulation.

 

argon, not nitrogen

 

I was about to say, nitrogen wont do much for you as it diffuses (moves around) just as fast as air. Argon being far heavier is much better suited to the role of an insulator.

 

I agree that the R-factor of a sealed gas would be higher than non-sealed air, like in windows. The R-factor of air is about 1.7 (compared to 1" of that expanding foam at 5, and 4" of pink bats at 13-17)
That said, all my airbox temp measurements suggest that airbox air falls to ambient quickly once moving (especially with my FAD), but it rises quickly at rest/stop/idle. I was thinking of reducing heat soak over durations of 1 minute. However, eventually the air gap will reach engine bay ambient, and the effect is gone.
I have an Al-clad fiberglass insulation over the outer wall and air gap. I could use rubber to actually seal it then lay the insulation over that. All great ideas, thanks!!
Of course my new ceramic inside/outside header shouldn't produce as much heat as the old one but every little bit helps...

 

I knew it was one of those gasses and I had just read about nitrogen in yer tires (and knew someone would jump on it if wrong). Maybe if ya can't seal it with gas; what about some sort of foam(high/low density styrofoam)? it shouldnt conduct the heat very quickly at all, but no idea if that area gets hot enuff to melt it.

 

I would not expect any less from the PARTSMAN. Great site.

 

Another vote for aerogel - maybe not M7 pads - but some form of aerogel... one of the best insulators available (that doesn't require an air- or vacuum-tight seal).

 

Actually you could look at this from a physics standpoint...

Where the rate of energy transfer is given by...
P=kA[(Temp(outside)-Temp(Inside)/L]

We know...

k=16 for stainless steel while plastic is .103

Since Area, A, remains constant as would external temperatures, the only major differences would be the inside temperature and L, which is the thickness of insulation.

So lets assume some numbers to determine proportionality to see if further insulation is necessary...

A=50
T(O)=210, which is 98.8 Celsius
T(I)=195, 90.5 Celsius
L= .009 meters

So P for no insulation =
737,777 J/sec

And then assuming (16+.103)/2 is k-value for plastic insulation... and that L, thickness is now .013 meters P is =
271,825 J/sec

That is a 63% difference in convection!

 

But don't you first need to establish how you want to keep heat out of the airbox?

Why would you want insulation versus reflection for example or some combination of techniques?

 

So staz87, do I leave the airgap, or fill with something? Does your calculation tell me the reduction in convection from my setup (approx) without insulation, or with something in the airgap?

As I said, the final airbox has Al-clad fiberglass insulation wrapped around it, so there's an additional layer of reflection/insulation not shown in the photo above. But once that's applied you can't see the double wall construction, which was what I wanted to show.

 

That DEI stuff is great. I use it to help control heat on the RX7. Ceramic coatings (from a good vendor) also help.

 

Looking forward to your results / numbers. I insulated my metal airbox (al-clad fiberglass), but felt as if it just heat soaked + then stayed that way, worse than before. For low speed or stop + go, I'm going with the assumption that it's O-K as is.

 

http://www.gtt.uk.com/parts1.asp, GTT 'COLD RAM' INDUCTION KIT

An excerpt from the blurb (bold is mine), "True cold feed using a larger (note the angled side) 'twin skin' upper airbox to shield away the heat from the adjacent hot exhaust manifold This increases airbox volume by around 25% over all other designs that seal against the bonnet underside. The 5mm air gap between the skins gives a superb thermal barrier. After a hard run the Ram Pipe remains ice cold to the touch. The upper airbox/heatshield is anodised in an attractive blue finish for good appearance and longevity."

 

Basically it was just a rough calculation based off having no gap in the air box. Basically, if you use a gas as an insulator, it will be better than almost anything you can put in there. Using air for example instead of asbestos would be 10x more effective. However, from what I understand this is only if the gas is contained and possibly pressurized. So using insulation would be the next best thing.

But I think there is a reason that engineers don't insulate the air boxes. If you think about it the air traveling through is only present for a moment, and can only absorb so much energy from the airbox before it enters the engine. So while you may have greatly reduced conduction, the temperature drop of incoming air is probably nominal.

Anyway, even if it only drops one degree, using Boyle's law, that should equate to about one extra horsepower.

Keep us informed, curious to see if it works.

 

I can't believe they just said it was "Ice cold"
That's impossible unless they started the engine cold in subzero temperatures, revved it and called it a hard run

 

The Marketing silo strikes again!