Engine insulation for hybrids to improve fuel economy

[Phase]

Originally Posted by Talos Woten

I agree with your buddy that just laying down insulation on top of the engine is questionable. Aside from moving parts there are also bumps and vibration that might abrade the envelope. Attaching to the hood with a gap seems safer in my mind.

The current insulation reigning champion are aerogels:
https://www.aerogel.com/about-aerogel/
but that is hideously overpriced and better suited to other applications (like space flight where every ounce costs money to launch).

There are at least four factors that we want to consider for an insulation in the engine compartment.
1) Temperature. Since most compartments won't be above 200F, virtually all insulations mentioned will be fine temp-wise. The only potential issue is failure cases like an engine overheating, in which case you'd want something rated past 300F just to be safe.
2) Flammability. Engine fires happen, and we have to account for them. This rules out any kind of paper, cellulose, etc. and makes us favor mineral wools, which are already known for their non-flammability. Ceramic fiber is a kind of mineral wool.
3) Longevity. Many kinds of insulation are hydrophilic, which long-term degrades their insulation capacity and/or structure. This is a notorious weakness of fiberglass bats. However, in this application, moisture will likely be regularly baked out of the material, so it's less of a factor.
4) Cohesion. We want the material to retain its shape and to not flake into the engine compartment. This rules out all fills, grains, etc. It also makes us favor pre-made insulation that is faced or sided.

So after the whole analysis, mineral wools come out on top because of flammability. If you dropped that constraint, then a whole range of insulations (including foam et al) would then be viable. Oh, mineral wool is also generally hydrophobic with good cohesion, which is why I chose it in my own case.

If you are just looking to buy something, the product Isaac Zachary linked is great. Any faced mineral wool would work... the only thing I would do is try to find something in a larger single piece, and cheaper. That makes it easier to install, and easier on your wallet.

Good luck!

Okay I was leaning towards a product like he mentioned, then completely seal it with foil all around

I was thinking of using some heavy duty Velcro with many different mounting points to attach it, that way in the summer I can just take it off for better cooling

[cRiPpLe_rOoStEr]

How would Velcro withstand to the high temperature inside the engine bay?

[Phase]

Originally Posted by cRiPpLe_rOoStEr

How would Velcro withstand to the high temperature inside the engine bay?

Velcro would be on the other side of the insulation from the engine. Attached to the hood right? I’d just have to use an adhesive than can handle heat

[Isaac Zachary]

Ahem...

Velcro brand products for high temperature

VELCRO® Brand products include solutions that can withstand at least 800° F (426.6° C).

[Phase]

So far it seems like my plan is to get ceramic fiber 1 inch thick from Amazon or Home Depot, cover it with aluminum reflective bubble foil, then tape off and seal the edges. Then after that just attach it to the hood

[Talos Woten]

Originally Posted by Phase

I was thinking of using some heavy duty Velcro with many different mounting points to attach it, that way in the summer I can just take it off for better cooling

I seem to recall your Ioniq has the automated radiator grille, in which case permanent attachment is also an option (for those lazy like me) . Though making it removable does give you more options and makes it easier to test, to boot.

Just FYI, I've restricted my air intake to ~70 sq in and leave the hood insulation on all the time. I'm a snowbird so I'm mostly in hotter weather. I've been watching my temps carefully, especially when I turn on the AC, and I have a problem with *overcooling* my engine now, because of the new way that I've routed the airflow. All this is to say, it doesn't seem like the insulation will cause overheating, assuming your radiator system is working properly. And if the latter fails, it won't matter when you have the insulation in or not.

Let us know how it works out!

[Phase]

Originally Posted by Talos Woten

I seem to recall your Ioniq has the automated radiator grille, in which case permanent attachment is also an option (for those lazy like me) . Though making it removable does give you more options and makes it easier to test, to boot.

Just FYI, I've restricted my air intake to ~70 sq in and leave the hood insulation on all the time. I'm a snowbird so I'm mostly in hotter weather. I've been watching my temps carefully, especially when I turn on the AC, and I have a problem with *overcooling* my engine now, because of the new way that I've routed the airflow. All this is to say, it doesn't seem like the insulation will cause overheating, assuming your radiator system is working properly. And if the latter fails, it won't matter when you have the insulation in or not.

Let us know how it works out!

the shutters rarely open. all i remember is seeing them open in arizona this summer. drove about 500 miles from north arizona to yuma this summer. it was hot out, black car. stopped at a gas station and noticed the front shutters open and a fan sound with the car off. guess it was too hot out. would explain why my mpg was so low. 65mph driving on back highways and was only getting 53mpg... the front shutters opening clearly caused a ton of drag

[hayden55]

Yup the insulation doesn't help to heat the engine up faster (noticeably). It just seems to hold heat better when the engine is off. It loses less than a degree per minute for me now. Its like a logarithmic curve though for heat loss. So typically when i care I will leave the car for likw 20-30 minutes and then come back and the car will still be above 150F so it will still operate like a hybrid. I also have my upper and lower grill on my prius blocked off with a hot air intake pull around 30F over ambient air from the headers. The engine bay still vents itself clearly though. Lots of leaks in the front end, underside, through the wheel wells. etc...
I leave my lower grill blocked year round and use the warm air intake year round as well. I will probably use the insulation year round as well now that I don't tow a boat anymore.

[Phase]

Originally Posted by hayden55

Yup the insulation doesn't help to heat the engine up faster (noticeably). It just seems to hold heat better when the engine is off. It loses less than a degree per minute for me now. Its like a logarithmic curve though for heat loss. So typically when i care I will leave the car for likw 20-30 minutes and then come back and the car will still be above 150F so it will still operate like a hybrid. I also have my upper and lower grill on my prius blocked off with a hot air intake pull around 30F over ambient air from the headers. The engine bay still vents itself clearly though. Lots of leaks in the front end, underside, through the wheel wells. etc...
I leave my lower grill blocked year round and use the warm air intake year round as well. I will probably use the insulation year round as well now that I don't tow a boat anymore.

Know any ways to get hot air to blow in the cabin faster? I don’t even care that much about mpg in winter. I just wanna be warm lol

[hayden55]

1. Buy a scan gauge and monitor intake air temps, water temps, and inverter coolant temps.
2. Block lower grill completely
3. Warm air intake from header area with a tube and hose clamps.
4. block upper grill
All vehicles usually have open engine bays that can be seen to a certain degree through the wheel wells. Plug them up and see what improvements it makes and how much you need to plug it up. Same thing for holes in the underbody cover of the engine bay.