cold start penalties & block heaters

[npauli]

Background:

So, being the geek I am, I did some quick and dirty hand calculations to compare the amount of energy that can be stored on my vehicle in different ways (kinetic, thermal, electrical, etc.). Next to the fuel in the tank, I was surprised to learn that thermal energy took 2nd place. Roughly speaking, it takes the energy contained in .1 gal of diesel fuel just to get my engine, oil, and coolant from room temp to operating temp. Consider that not all your fuel energy heats the engine (some goes out the tailpipe, some heats the air), and it looks like every cold start costs me on the order of .25 gal (or $1 in economic terms). Now my average trip length probably burns about 1 gal of fuel, so it looks like eliminating all cold starts could give a huge boost to mpg. Easier said than done though.

Questions:

1) Does anybody use a block heater or other source of heat for every cold start, rather than just when it's really cold outside? I'm wondering how concerned I should be about corrosion from using the heat more than "necessary" since electricity + heat + metal + water = corrosion.
2) Has anybody tried using solar, batteries, etc. to keep your vehicle warm while you're parked away from home?
3) How much reduction in this startup penalty can I realistically expect to see?

[Shrek]

I have one golden 'trick-with-a-stick' that I use. As soon as I get to a flat piece of road in the first seconds/minute after starting to drive, I let the car drive in idle with 2'th or 3'rd gear. This pushes the RPM down fro 1600 to 1000, and gives the exhaust time to heat the engine walls. Power is enough for 10-15 MPH.

By the end of my small piece of road before it starts to go downhill towards the highway I already have my FE down to 10 l/100km.

[cephraim]

I was just over at Amazon looking at solar panels, controllers, rechargeable 12V batteries and 12V heaters. Although it would be expensive (over $200), I think you could easily cobble together a system that charges the 12V portable battery with a 15W solar panel that can sit on your front or back deck while at work and provide enough power to defrost your windows and keep you toasty with a portable heater on that cold ride home.

[vtec-e]

I haven't used solar panel or anything but i have blocked the hell out of my radiator (60-70%). Warms up much quicker and runs hotter too so my fuel use at 80 to 100 kph seems to be around the 3L/100k mark. My wife drove home from work today and had 5.5L/100k so i guess if you drive like everyone else, a diesel engine will drink the same amount fuel no matter what mods you use. Unless you do a lot of aero mods like Basjoos.....

ollie

[seftonm]

How did you determine that using the block heater will cause more corrosion? Electricity does not flow through the coolant or engine, it simply goes through a heating element in the block heater. So all you will have is heat + coolant + metal, something which already happens anyway inside your engine. I would say corrosion is not worth worrying about.

In my first mile, I will get about 30% better fuel economy if the engine is already warmed compared to starting from 70F.

Going for the low hanging fruit first would probably be your best bet. I am sure your Duramax has quite a large grill and radiator for towing reasons so try experimenting with a grill block. The block heater will also help a lot; experiment with it on a timer to figure out when it ends up sucking more electricity than it's worth.

Getting a useful heating system out of solar panels and batteries could get expensive. Making heat requires a lot of electricity so you will either need quite a few solar panels or a long charging time to get much out of them.

[npauli]

How did you determine that using the block heater will cause more corrosion?

Not a fact that I've experienced first hand, but the sum of some anecdotal evidence + some educated guesses.

1) A guy at work with a gas pickup had a freeze plug corrode to the point of leaking - it happened to be the one with the heater.
2) Things like water heaters always have corrosion at some rate.
3)Higher temps, higher temperature gradients, and more dissimilar metals in contact all make corrosion happen faster. We get a little of all 3 with a block heater. Maybe not enough to matter, but a step in the wrong direction.

All that to say, I know the block heater costs me something (electricity and maybe accelerated corrosion) and gains me something (better starting fuel economy, with more benefit at colder temps). I'm just not sure where the best tradeoff lies. I'll plan on doing some trial and error in the coming months to try to find out

Thanks for all the comments so far. For what it's worth, I plan on finding a "diesel engine winter cover" to help keep the heat in the radiator. I'd prefer something porous that covers the whole radiator over something that completely covers part of the radiator, in order to keep radiator temps as uniform as possible.

[vtec-e]

Originally Posted by npauli

[i]

1) A guy at work with a gas pickup had a freeze plug corrode to the point of leaking - it happened to be the one with the heater.

Could it be galvanic corrosion?

ollie