The first kilometer/mile - Fuel Economy, Hypermiling, EcoModding News and Forum

Piwoslaw · 10-14-2012, 02:53 AM

What is the best way to drive the first kilometer/mile to reduce both wear on the cold engine and fuel consumption?

Pulse and engine-on glide, like I always do? The glides are usually longer than the pulses, so the engine is idling cold more often than not, which it really shouldn't be doing.
Pulse and EOC? The engine isn't running cold then, this also extends the distanse before reach operating temperature. In my case, before killing the engine I'd have to wait for the turbo to cool down after each pulse, so I'd still be idling the engine. And once I'm ready to kill it I'll almost be ready for the next pulse.
Steady driving in gear? This may speed up warmup time, but the engine won't be operating in the most optimal rpm/load range, so I'll burn more fuel.
Other ideas???

redpoint5 · 10-14-2012, 03:14 AM

I am no expert on wear, but I practice option 1. This is no different than I normally drive with a warm engine though. I only P&G when there is sufficient downhill grade or utter lack of traffic to not disturb normal traffic flow. Lately I have begun EOC for coasting sections of 0.5 miles or more... Time to wire in an engine kill switch.

Patrick · 10-14-2012, 11:03 AM

2. For better fuel economy. "They" say that with modern engines it won't make much if any difference in engine wear. Where did you hear that you have to cool the turbo after every pulse? I don't think that's accurate.

I know with the Prius they run the engine for a while when it's cold, but that's to heat up the catalytic converter, not the engine.

BHarvey · 10-14-2012, 12:43 PM

Smooth light throttle inputs at a little higher rpm will keep wear to a minimum while the oil gets up to temp. Coolant comes up to temp within 2 miles on my car, but the oil takes another 13-15 miles before it is stable at 188f.

Until the oil is warm on my car it is very difficult to get best mpg's.

Gealii · 10-14-2012, 01:03 PM

I take it easy until my coolant gets up to temp. Though a little different on an auto trans the torque converter doesn't activate until my coolants at 170F and pulse and gliding makes my mileage go down if i don't use it

Piwoslaw · 10-14-2012, 04:03 PM

Quote:

Originally Posted by Patrick

Where did you hear that you have to cool the turbo after every pulse?

Turbo Diesel vs EO(ff)C

Patrick · 10-14-2012, 05:04 PM

Quote:

Originally Posted by Piwoslaw

Turbo Diesel vs EO(ff)C

That makes sense.

I used to have a Mitsubishi twin-turbo. I never idled it after running and never had a problem. I ran synthetic oil to prevent coking, though.

So take my advice and use your own judgment.

AndrzejM · 10-16-2012, 04:16 AM

As far as I know turbo won't heat up to the oil boiling temp during 10 seconds pulse. If you are driving on the highway for extended period of time with high boost that's the time to let turbo to cool down for a bit before killing the engine. And it's less likely for diesels than gassers, because exhaust gasses are much cooler. You should remember that turbo won't heat up just because of spinning, it's exhaust gasses temp that is heating up the propeller and then heat is transferred to the main axle, so it takes some time for heat to build up in the bearings where oil is working.

And regarding your original question. I think that if you want to reduce wear of the cold engine you suffer in FE area and the other way around, if you focus on the FE only your engine will suffer because of cold wear.

Arragonis · 10-16-2012, 03:54 PM

Cold diesels do sound "rough" though which makes us think we are hurting them

in some way, even the ultra modern CR ones. Also the mounts are cold and less supple meaning you get more vibration.

I tend to just drive as soon as the red oil light is out to get the temps up asap. The Prius does this but (as stated earlier) this is to get the cat up to temp and not the coolant - the Prius could do with a much smaller radiator opening IMHO, it looks like a basking shark.

Quote:

Originally Posted by Piwoslaw

Turbo Diesel vs EO(ff)C

I never used EO(ff)C much in the Fabia due to this issue - I really didn't want to spend money on the Turbo which had already been replaced by the DPO. Plus the turbo needs really nice oil otherwise the VNT bits start to clog up - usually easily freed with a prod somewhere. Thinking further though I think the others are right - a quick pulse, even a really fierce one - wouldn't be enough to raise the oil temp enough to cause heat soak unlike a fast trip with a quick shut-off.

Being able to shut off whenever was one of the reasons to swap to Petrol. And also the radiator blocks, which I am about to go outside and refit now that George has had his "pre-winter" service - to keep the warranty alive.

PaleMelanesian · 10-16-2012, 06:09 PM

I have no experience with diesels or turbos, but I approach cold starts just like warm starts. Low rpm, high load (say medium load for the first minute), EOC. I'll let it idle a few seconds after starting, but that's it. Any deviation from that for faster warmup is extra fuel used.* My car has lived 200,000 miles, so I doubt extra wear is a significant factor.

Faster warmup does mean lower fuel usage later in the trip, but at best you get back half of what you spent warming up. Best fuel consumption is to arrive at the other end with the coldest engine you can. Grille block to make it warm up faster.