Wattage needed for block heater?

[Tygen1]

So I purchased a Kat's freeze plug block heater, 400w. Got it the other day and it is the size of my thumb and I got skinny fingers. It's really tiny and makes me wonder if it will be enought to get the engine warm, I'm expecting/hoping around 130F. I have a 2Liter four cyclinder and the cooling system holds 2.5gallons total, probably almost a gallon in the motor. I was hoping to put it on a timer and have it turn on 1-2 hr's before I leave for work in the morning. Does anyone have any expirience with these? Do I need another heater.... or two?
I'd like to know if I need more, before installing, because it is quite a challenge to get it in.

Thanks.

[Daox]

The 300W block heater I have for my Matrix runs for about 2.5-3 hrs before I leave in the morning. It usually gets coolant temps into the mid 90s. The downside to my setup is I'm sure I'm loosing a lot of heat right out of the aluminum block.

[MetroMPG]

FYI: 300w, exteral element style (less efficient than your frost plug style) heater, on a 1.0L block:



800w inline heater:



from Experiment: how long should a block heater be plugged in? - MetroMPG.com

I'd expect yours to fall closer to the middle of the two than the 300w end, just because you're heating the coolant directly.

[TomO]

From personal experience on my 1.5L aluminum blocked 94 Civic VX:
After 2 hours on time from a 400W freeze plug style heater, the heater exterior casing was showing 120°F, the exterior of the aluminum block was showing 92°F within a 2" radius from the block heater. The further away from the frost plug heater the cooler it got, down to 75°F at the opposite end of the block. Air temperature indicator showed 65°F under the hood of the car just inside the WAI opening (approx. 12" from the frost plug heater). Temp gauge that I have that is in the head of the motor only reads down to 100°F, so I'm guestimating that the acual water temp inside the block was closer to 80-85°F.

The thing about the setup from Honda is that the frost plug for the heater is not simply a threaded open hole in the block. It actually only goes in an inch and then is encapsulated with a vent hole on the top of the capsule and the bottom. Think of a milk cap recessed in the block with a hole at the 12 and 6 o'clock positions. This leads me to believe that the frost plug heater heats the coolant more indirectly by warming that aluminum block and allowing the warm block to warm the coolant rather than heating the coolant directly. I believe Honda has done that to reduce thermal shock of the coolant and temperature differential in the coolant itself, since the frost plug location is not in the center of the block.

I do know that on the Ford and Chevy V8 motors, once you knocked out the frost plug, it was a direct shot (unrestricted) into the water jacket.

So in your case, the frost plug may be a direct port into the water jacket allowing for faster convectional circulation of the coolant. Allowing for a shorter (2 hr) warmup time for your block.

Metro (Dan), Do you remember if your frost plug allowed direct access (unrestricted) into the water jacket or was it something similar to what I described in my Honda motor?

[MetroMPG]

Tom, you talkin' to me?

I don't have the frost plug style. The 300w one is an external bolt-on element. Sits flush against the rear of the block.

The 800w inline one is a tank style, spliced into the heater core loop.

[Tygen1]

Mine is directly in the coolant passage. In fact there are two freeze plugs in the back of the block. So it's easy to do both freeze plugs at the same time. Problem is I gotta take the intake manifold off to get access, quite a headache if one can't do the job.
Is there such a thing as too much? I'd hate to spend the extra money and time if it won't make much of a difference?
Should I just try one and see if it can cut it, or just go for it and put in two 400w freeze plug heaters. I also see those tank style and lower heater hose styles that I haven't considered before....
Thanks for your patience with my questions.
BTW, I also got the 150w pad heaters for the engine and trans oil pans

[TomO]

Originally Posted by MetroMPG

Tom, you talkin' to me?

I don't have the frost plug style. The 300w one is an external bolt-on element. Sits flush against the rear of the block.

The 800w inline one is a tank style, spliced into the heater core loop.

Ah I see, so the 300W relied on heating the actual block and then allowing convection (proper term there?) to heat the coolant.

The 800W used the properties of the rising heated coolant to circulate then and warm the block.

Originally Posted by Tygen1

Mine is directly in the coolant passage. In fact there are two freeze plugs in the back of the block. So it's easy to do both freeze plugs at the same time. <snip>
Is there such a thing as too much? I'd hate to spend the extra money and time if it won't make much of a difference?
Should I just try one and see if it can cut it, or just go for it and put in two 400w freeze plug heaters. I also see those tank style and lower heater hose styles that I haven't considered before....
Thanks for your patience with my questions.
BTW, I also got the 150w pad heaters for the engine and trans oil pans

I wouldn't go with two heaters, personally, kind of overkill, unless you want to spend twice the money on electricity to warm you car up a little faster/hotter, especially if you're going to use the pad type heaters as well.

If you have a system that will work with a tank style heater, that might be the way to go as you will have to run it for less time to achieve the same temp and it promotes more circulation than a frost plug type heater. this may be less work than installing the frost plug type as well since you've stated that you'll need to pull off the intake manifold to install the frost plug heater.

EDIT: just read the first post again and see that you already have the frost plug type in hand, might be best to go with that as you have the part already rather than having to hunt down a tank style and research if your system will work with it.

[Tygen1]

For those interested, the generic Kat's 35mm freeze plug heater does not fit the Ford Zetec. I was soo close, I had to bend the heating element up quite a bit to get it around the narrow opening in the water jacket, but when it came time to tighten it up the bolt snaped because it is made for a deeper water jacket. Oh well, I did get the oil pan and trans pan heaters hooked up. They are hot to the touch in less than a minute.