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Isaac Zackary · 04-11-2015, 02:15 AM

So I have a 1985 VW diesel. So far I've been getting upper 50's (mpg US) on the highway.

But the problem I've been having is warmth. Even during the summer our town is so small that if I drive to the store, work, anywhere in town, it's so close that the engine does not warm up to running temps in that distance. To make matters worse winter temperatures here are constantly below freezing and can reach well below zero Farenheit for most of January sometimes reaching as low as -40° F. This not only makes me a bit unconfortable (ya, I wear long johns, sweater, coat, hat scarf, gloves, boots, the works!) but it also worries me for the engine's sake. I'm sure that it's not good for fuel efficiency nor the enviroment when I'm billowing out huge clowds of white and black smoke as it warms up.

I've got it adjusted so that it hardly smokes at all at full throttle when warm (only when at high RPM and full throttle). But all that smoke when the engine is cold indicates that much of my fuel is not burning completely or at all!

I think part of the reason is that my engine is a bit too efficent. With a 23:1 compression ratio I think it converts too much fuel into power instead of heat. I've tried new thermostats, different temperatures, grill block offs, and a block heater. My current block heater is a 1,600 circulating tank heater that does a very good job, if I'm where I can plug it in. But when I leave the car at work and other places it cools down fast. Now what?

So instead of using 0W-20 to keep my oil pressure from blowing my oil filter, wouldn't it be nice to have a way to warm and keep warm my engine? I'm throwing a couple of ideas out there. Any other ideas would be welcome!

Passive solar block heater
So I've been thinking of plating below and around the whole engine. I'd leave a space in the back where air from the radiator can exit. Also I'd like to keep the radiator blocked off, at least during winter. Automated louvres would be nice! Besides that I was thinking of cuting a large part out of the hood and placing a piece of glass in it. I might coat the whole inside with aluminum foil. With the black engine all that light should reflect on it and keep it warm, at least during the day.

Exhaust coolant heater
I was also thinking of using exhaust heat somehow to heat the coolant. There are few ideas to this. One would be to just place one piece of tubing along the exhaust down pipe and re-route the heater hose through it so that it doesn't overwhelm the cooling system during summer use. Another idea would be to have the exhaust pass through a heat exchanger, maybe a modern TDI EGR cooler, and have an exhaust valving system that bypasses the heat exchanger once operating temperatures are reached.

Also there are two coolant sources on my engine for this. One is the cabin heater coolant circuit, which passes back near the exhaust system. This is constantly flowing, although probably not as much as the cold bypass circuit does when open. The cold bypass coolant circuit is on the front of the engine and it circulates coolant until the thermostat opens the radiator circuit completely, at which point it shuts off this circuit. This could be routed to the back of the engine.

Of the two each has their pros and cons. The heater does not have an air recirculating feature, so the coolant running through the heater is obviously going to be cooled quite a bit. So it makes sense to reheat this coolant as much as possible. On the other hand it is constant whereas the cold bypass circuit shuts off when hot. Yep, if I did have an overheat situation, this would generate steam at the heat exchanger. But as long as the thermostat is working, at least it would not continue to circulate coolant through the heat exchanger.

I kind of like both ideas. But maybe someone else has a better idea. What's your thoughts?

04-11-2015, 02:15 AM	#1 (permalink)
Isaac Zackary Full sized hybrid. Join Date: Apr 2015 Location: Colorado Posts: 602 Suzy - '13 Toyota Avalon Hybrid XLE 90 day: 37.18 mpg (US) Thanks: 369 Thanked 108 Times in 84 Posts	How to keep an efficient engine warm? So I have a 1985 VW diesel. So far I've been getting upper 50's (mpg US) on the highway. But the problem I've been having is warmth. Even during the summer our town is so small that if I drive to the store, work, anywhere in town, it's so close that the engine does not warm up to running temps in that distance. To make matters worse winter temperatures here are constantly below freezing and can reach well below zero Farenheit for most of January sometimes reaching as low as -40° F. This not only makes me a bit unconfortable (ya, I wear long johns, sweater, coat, hat scarf, gloves, boots, the works!) but it also worries me for the engine's sake. I'm sure that it's not good for fuel efficiency nor the enviroment when I'm billowing out huge clowds of white and black smoke as it warms up. I've got it adjusted so that it hardly smokes at all at full throttle when warm (only when at high RPM and full throttle). But all that smoke when the engine is cold indicates that much of my fuel is not burning completely or at all! I think part of the reason is that my engine is a bit too efficent. With a 23:1 compression ratio I think it converts too much fuel into power instead of heat. I've tried new thermostats, different temperatures, grill block offs, and a block heater. My current block heater is a 1,600 circulating tank heater that does a very good job, if I'm where I can plug it in. But when I leave the car at work and other places it cools down fast. Now what? So instead of using 0W-20 to keep my oil pressure from blowing my oil filter, wouldn't it be nice to have a way to warm and keep warm my engine? I'm throwing a couple of ideas out there. Any other ideas would be welcome! Passive solar block heater So I've been thinking of plating below and around the whole engine. I'd leave a space in the back where air from the radiator can exit. Also I'd like to keep the radiator blocked off, at least during winter. Automated louvres would be nice! Besides that I was thinking of cuting a large part out of the hood and placing a piece of glass in it. I might coat the whole inside with aluminum foil. With the black engine all that light should reflect on it and keep it warm, at least during the day. Exhaust coolant heater I was also thinking of using exhaust heat somehow to heat the coolant. There are few ideas to this. One would be to just place one piece of tubing along the exhaust down pipe and re-route the heater hose through it so that it doesn't overwhelm the cooling system during summer use. Another idea would be to have the exhaust pass through a heat exchanger, maybe a modern TDI EGR cooler, and have an exhaust valving system that bypasses the heat exchanger once operating temperatures are reached. Also there are two coolant sources on my engine for this. One is the cabin heater coolant circuit, which passes back near the exhaust system. This is constantly flowing, although probably not as much as the cold bypass circuit does when open. The cold bypass coolant circuit is on the front of the engine and it circulates coolant until the thermostat opens the radiator circuit completely, at which point it shuts off this circuit. This could be routed to the back of the engine. Of the two each has their pros and cons. The heater does not have an air recirculating feature, so the coolant running through the heater is obviously going to be cooled quite a bit. So it makes sense to reheat this coolant as much as possible. On the other hand it is constant whereas the cold bypass circuit shuts off when hot. Yep, if I did have an overheat situation, this would generate steam at the heat exchanger. But as long as the thermostat is working, at least it would not continue to circulate coolant through the heat exchanger. I kind of like both ideas. But maybe someone else has a better idea. What's your thoughts?