Thermal blanket for engine
 

I've got grill blocks installed on my Subaru WRX. I've also used a piece of foam to partially block the intercooler. The engine warms up a bit faster, but I'm not seeing much of an improvement in engine temperature rise with my block heater. It can get down to -40 C here, and I've got a lean-burn engine tune with reduced cold idle speed, which increases warm up time.

The hood is insulated, but the hood scoop also has vents that go directly into the engine bay on either side of the intercooler. I'm sure a lot of heat escapes from here, so I thought I'd just put an insulating blanket on top of the engine in this area.

What is a good, inexpensive material that will work? It's a boxer engine, so everything hot is down low in the engine bay. I might also use it to cover the oil filter and oil-coolant heat exchanger, which could get up to 100 C.

I have a fire blanket in the engine bay. It's made of fibreglass. Does a decent job in tandem with the block heater. I just make sure it stays clear of the radiator fan, belts and pulleys.

My first thought for the OP, since all heat rises, and sounds like trapped heat escaping is an issue, how about restricting cold air rising from the bottom, ala an engine compartment area belly pan on steroids? Based on other threads here, if able to handle the heat, it could be stretched fabric?:D

I put in an OEM block heater on my Avalon, and it only heats it some 30 °F (17 °C) difference compared to ambient temperatures. It can also get down to -40 °F (-40 °C) here.

I want to put a 1,000W or 1,500W circulating block heater. But I want to get a 120V pump to go with it since trying to hook one up so it circulates via temp differences and boiling is a bit of a pain on a new engine and a way to make coolant bypass things it shouldn't.

Thanks for the suggestion. I just ordered a couple of them.

That seems awfully low. My coolant heats up by around 30-33 C in 4+ hours. On my last car it was 40 C. Both 400 W block heaters.

What is the power rating of the heater? I'd check its resistance with a multimeter to make sure you don't have a wiring issue. Should be 33-36 ohms for a 400 W block heater.

I got thick fire fiberglass insulation and the. Covered it with aluminum bubble insulation RV people use on their windows and then sealed and taped it shut.

I'll check, but I belive these are supposed to be 150 or 200W.

Do you know what kind of aluminum bubble insulation you used, or what its temperature rating is? I looked into using this type of insulation before, but the stuff I found is only rated for temperatures up to 180 °F.

Some years back I experimented with block heaters. The Honda OEM block heater I was using was 450w, which helped, but I also put a pad heater on the oil pan and transmission, which made a noticeable improvement. I got these from eBay and connected them to a multi-outlet that hung from the front grille.

You really have two separate issues -

1) Getting enough watts to heat the engine block while it's sitting - you're not going to be able to insulate it enough to massively change heat retention.

2) Closing the bay off enough from airflow while the car is moving.


While the car is sitting, air in the engine bay is essentially still. While the car is moving, air might be passing over the engine at 100kph (or more, because the grille and ducting may accelerate the air).

Heat rise will not be a significant factor in an engine bay. It's leaky enough that any warm air will be blown out by the slightest breath of wind, and while moving, there will be no thermal gradient. Hot spots are generally from heat sources, and what that direct radiant heat hits.