I can't make this mod now, nor do I have a good way to measure thus theoretical. But it's something I'm wondering about that I can't quite wrap my head around.

So if I knew I was going to be idling for a long time would it be better to purposefully draw in hot air? Picture something along the lines of the hot air systems on older gas engines that draw air from a shroud around the exhaust manifold.

All internal combustion engines are in general more efficient when the intake air is cold. But that said diesels don't make much heat at idle, under certain circumstances can actually cool too much, and a certain amount of heat is important for good combustion.

Taking in hot air the thermal efficiency of the combustion process would be lower cause the difference in temp between compression and combustion is lower. But on the flip side the operating temperatures would be more stable and the combustion itself more complete/stable. This of course is more true in colder climates and if one reason the engine is idling is to provide heat to the cab. This is my thought process anyway.

Thoughts?

 

That's an interesting line of thought!

I know that extended idling is considered "severe duty" by Ford, at least as it concerns oil change intervals.
And I've heard the same thing about too-low temps at idle doing something but can't remember exactly what.

Why idle for a long time? Just for heat?

 

Sleeping in and working out of the rig, heat or AC and accessory power. Alternator, and eventually engine drive air compressor.


Like I said more of a thought experiment at this point, it's bugging me that I can't wrap my head around this. But maybe eventually I can put it to practice.

 

Best way is to set it up for high idle.

 

One thought is to setup an electric fan or electric-clutch on the stock fan. Then, you can shut it off when it's too cold - It will warm up under idle with no fan, at a relatively slow rate. So your fan might only kick on for a few seconds every 10 minutes. But that would definitely control the temps.

 

I agree with the last two comments. Electric fans are great on a diesel because you can totally turn them off for warm up and idling. High idle is a must also.

As for extra heat, I have always wondered about all that waste exhaust heat. If you had some kind of heat exchanger wrapped around the exhaust manifold, you could pump coolant through it to gain extra heat. I would love to do this on every cold start to get the engine up to temp faster.

Another thought is to install a large alternator and power inverter, and plug in your block heater while you idle. The added load on the alternator will produce more heat within the engine, and of course, so will the block heater. As bonus now you have a nice power inverter setup for anything else.

 

Let's assume all kinds of other fuel saving goodies, electric fan, electric water pump, AC clutch on the PS pump, etc.

A water cooled exhaust manifold would be detrimental to the engine in all other conditions, that isn't something you can just turn off. It would cool the exhaust which is bad for the turbo, and heat the coolant which is hard on the cooling system.

Using an electric heater could be useful for a fast warm up but not for fuel efficiency, the drag on the alternator would defeat the purpose.

 

Are you asking about high efficiency or are you asking about idling while maintaining high temperatures? You will never get both, choose one.

I didn't say it would be easy, but those are not things a little engineering could not solve. Yes, if you spent some time and money on a system like that it could be turned on and off at will. Certainly no more complicated than your idea of feeding the engine hot air. You could get the exhaust heat after the turbo, or in my case, I don't have a turbo, and don't want one...

 

Anybody know what EGTs would be ideal to keep the cylinder temps in a safe range?

It also occoured to me just now that you could retard the timing to bring more heat into the party. Not sure how much it would take but that's one idea.

Electric water pump?!?

 

Sure, you've never seen an electric water pump on an engine? I ran one on my jeep back in the day, it worked great, I was a little worried that it wouldn't move enough water but that sucker stayed cool. I'd like to on my IDI but time/money + custom is a lot harder then a bolt on SBC chevy one I got a deal on.

They work great, cause they can run at a constant speed and not engine speed so they are always going at an efficient speed when on, and of course can be switched off or kept on with the engine off.

Three common ways to do it: 1 a compete unit that replaces the water pump, you can get these for the common engines, SBC, BBC, SBF. 2. An electric motor and a belt connecting it to the stock pump. 3. A stand alone unit that goes in line with the radiator hose. If I did it on my IDI I'd do a motor and belt on the stock pump.

 

I've been wanting an electric water pump too. Most people seem to think they won't work on a diesel for some silly reason, but if they cool a big block chevy, they should have no problem cooling the same horsepower level in a diesel engine.

I've noticed some new options on ebay for remote mount pumps in the $150 range. I want to get rid of everything belt driven except for one big alternator some day...

 

No not really. You wouldn't be able to just shut off the coolant flow into the manifold, you'd have to empty the coolant passages. Were talking a chunk of iron that get's in the 1000 deg area, you can't keep water in that unless your goal was to make a bomb.


I'm talking a little sheet metal, a flap, and some hose.

 

Right. Without spending all day engineering it, some combination of check valves, solenoid valves, and pumps would solve that problem, with additional safety items like a high temp/pressure relief.

I didn't say it would be easy, but I bet I could do it cheaply with enough time and random ebay surplus parts.

 

This is interesting conversation, but to me the concept of efficient idle to power peripherals from a 444 cubic inch motor with a 21 to 1 compression ratio is crazy. From what I have read, a Honda generator and a 100' extension cord (to get the generator far enough away from the truck to keep you sane!) would power everything you require, except the on board air compressor, and at that point you can throw efficiency out the window anyway. All of these trucks set up to run pto's or power larger peripherals use a high idle switch. I believe standard range is 1k rpm.

 

I agree with Mac for sure. Modern Honda generators are pretty darn quiet too. Although it would add gasoline to the party, and having to have it at hand whenever the generator is needed.

No, I hadn't heard of an electric water pump... But I'm not a big gearhead, I just love to know how what I own works and how to fix it. I've only owned 5 vehicles in my driving life of 13 years. The most "modern" vehicle I've owned is a 1990 VW Cabriolet, lol.

But since you got me thinking about it, with an electric water pump and e-fans... You could potentially have a switch that selects a different thermal probe that runs much higher, like 230° or something to keep the block hotter.
Without actual temperature numbers to know what the goal is to keep the cylinders from having issues, we're kinda in the dark.
But keeping the block hotter would probably net a similar result to sucking in air from a heat exchanger plumbed into the cooling system.