HP differences between #2 and Winter Blend #1/#2?

This is a tangent off of the http://competitiondiesel.com/forums/showthread.php?t=20109 Thread.

I know I lose about 3mpg in the winter time up here with fuel supposed to be protected to -30 below (Minneapolis). And in the dead of winter, it gets close

Has anyone dynoed the 2 fuels in the same dyno session somehow? What about at least 6 months apart. I suppose corrected numbers only with the 6 month apart tests.

Does timing have an effect on fuels with different BTU levels?

Make sure you figure in the extra cold air charge from that -30* weather too, that ought to be good for a few horsies....

JFlagg said:

Make sure you figure in the extra cold air charge from that -30* weather too, that ought to be good for a few horsies....

Click to expand...

Hence the corrected numbers would smooth over the results a little.

Can it be? The colder better air with the less energy in the fuel make for the same over all WOT horse power with an overly fueled truck. I do notices less smoke in the colder months then when it's 100degrees 6 months later.

But at the same time while at cruise the air charge doesn't really work to your advantage as much such that you have plenty of room for more then enough air. however, to get that air spooled up in -30 you need more fuel, hence the drop in millage?

I actually got my best mileage when it was cold....but I think it was a one time fluke. Generally my mileage drops 2-3 mpg in the winter also. Had a discussion awhile back wether it was the winter blend fuel, the colder air, the longer idle times in the morning or what that contributed to it....I feel my truck runs best when its warmed up all the way and driving in sub-20* weather, but I don't get to experience that to much in STL.

60degrees and low humidity my truck runs best and "Feels" best. ironically ideal dyno conditions. Traction is typically better I'm borderline to much horsepower vs traction in the winter months.

JFlagg said:

I feel my truck runs best when its warmed up all the way and driving in sub-20* weather, but I don't get to experience that to much in STL.

Click to expand...

I too feel this. I contribute it too the Vp44 Brain. When its sub 20* and you sit at a stop light and the VP senses the cool air coming in it advances the timing to keep truck warm from what I understand. Then when you take off you get a nice little boost from the advanced timing. Just an assumption at work this morning.

I know when it gets that cold and I don't have a winter front in and I stop at a long redlight I've actually watched my thermostat drop to the 170* range from 190* So you might be onto something there Haloman. But my seat of the pantsometer may not be as highly calibrated as some folk's are...

I thought timing is retarded when cold outside so that fuel is injected closer to TDC where the compression stroke has the highest heat.

Trucks get best mileage in summer. Less rolling resistance in the rubber tires, bearings etc. Combustion gives off heat as a product so the more heat that is present before combustion, the more products it can give off because then combustion does not have to make up the difference between -20* air and 100* air. That take energy.

Winter fuel has higher cetane, so it it will combust at lower temp. But due to higher aromatics, it is a lighter fuel and thus lower BTU content per gallon.