intake heater

[dieselpower]

hey,
im not exactly sure what makes and models but some big trucks have an intake air heater instead of glowplugs. i was wondering if drilling and tappin holes about and inch above the ports in the intake then wiring up a set of glowplugs in there would help with cold starting. the way i see it is the glowplugs only heat up the air inside the cylinder so it only gets one compression stroke to ignite before it sucks in -20* air. whereas with the air getting heated in the intake as well should maybe make it start nicer and run better right after starting in the cold. has anyone had any experiance with intake heaters before and it there anything i'm mising that makes this a stupid idea?
thanks


Mark

[vwmike]

Why not just move someplace warmer?  

[Dr. Diesel]

i've wondered how those intake heaters work as well. You'd think that they'd only be effective for the first couple of turns before cold air was drawn in faster than it could be heated. I think the benefit of glowplugs isn't so much that they heat the air, but that they're an orange-hot surface that some of the fuel is injected on. Probably better to save some money for a rebuild if you're getting low on compression.

[andy2]

the intake heaters that you see on the 5.9 cummins etc dont really help the startability too much they are there to heat the cold air as the engine starts to warm up which gives less warm up emissions, thats really all they are there for. Remember those engines are direct injected and in some applications that engine does not have any intake heater anyways,so If you were to install one you would have a cleaner warm up thats all.

[MacGyver]

I've always wondered how effective manifold heaters are/were.
The 85 Tempo diesel I had, had one. It would go into series with the glow plugs in the afterglow phase. Can't remember if it heated up before cranking. QuickTD might remember, he had an Escort with the same setup.
I'd be careful what you got one from though, anything large size would pull a LOT of current, hope you got a good battery...or several of 'em

If they're only for emmisions, why do old industrial engines like Perkins have them?

Also then, there's the  fuel fired style, dunno proper term, where there's an injector in the manifold that feeds fuel in & burns during cranking. I have a 236 4cyl Perkins in my garage that has this. The engine is out of a forklift. I would think this would comsume more oxygen than the heat benefit overcame, but apparently it works.

[QuickTD]

I think that "manifold heater" in the escort and tempo diesels was more of a convenient place to mount the dropping resistor for the glow plugs than an actual heater. It didn't come on until the afterglow phase so it didn't really help with starting. It also didn't have much surface area exposed to airflow. The cummins air heater might be more effective but draws much juice. I'd want a second battery if I were using one...

Also then, there's the fuel fired style, dunno proper term, where there's an injector in the manifold that feeds fuel in & burns during cranking.

Ah, the CAV "thermo-start". They have a thermo disc valve and a coiled element. When the element heats up it pops the valve open admitting fuel from the pump return line. This fuel actually catches fire on the hot element, warming up the intake manifold. They are effective on DI engines like the perkins. The engine usually won't start while the flame is present. The trick is to get it cranking with thermo start button pressed and release it when the engine starts to sputter, it'll take right off then. A friend of ours has tried one of these in an IDI mercedes with mixed results. He said it didn't help much but didn't hurt either. I'm guessing that most of the heat loss during compression in an IDI engine happens in the prechamber. Heating the incoming air is only marginally effective if the prechamber walls are ice cold. I think for best results the prechamber needs the heat. Duraterm glow plugs, a big direct drive starter and lots of battery would likely be the best way to get an IDI to start in extreme cold.

[janb]

I have a manifold heater on my Case Crawler (70's vintage)

it is in the center of intake manifold (which has a very short run) and similar to a water heater element.  I use it for 30 - 45 sec. I've considered adding one to a tired VW, but... the long Alum intake would cool off the air.  Heat Guns help, but not too practical.  A diesel fired furnace, like in a boat would be nice, and provide adequate air flow.  Then there is always the real solution, increasing compression, and having operable glow plugs.
 
Dozer does have 2 batteries.  
janb

[dieselpower]

my glowplugs work good. its just that it gets really cold where i live. sometime down to -40*(of coarse i wouldnt drive then)but when its like -20ish*C then i was just wondering if that would help any on top of my glowplugs because i have nowhere to plug it in at school. right now i have them wired up to a switch so they turn on and stay on while cranking and stay on after it starts so that it clears up the smoke faster. i have pretty low compression i think but im waiting to rebuild it till it breaks something else like that.
thanks for the input


Mark