I understood, I was just adding the idling question on top of the rest of the discussion. Sorry to add to the confusion.
But your statement "that common rail cars use more fuel when coming up to temperature" still is not registering with me. You say the AHL takes much longer to heat up. So are you saying in the shorter
time period - let's say 5 minutes - the common rail is running to reach temp, it has used more fuel than the ALH which has run for - let's say 10 minutes - to reach temp? That doesn't seem right.
Note I'm not disagreeing with you, but rather trying to understand better.
I think what you mean is this:
Let's say the CR burns .2 gallons to come up to temperature, and it takes 5 minutes. It then burns .1 gallons over the next 5 minutes, for a total of .3 gallons in 10 minutes.
Now let's say the ALH burns .1 gallons per 5 minutes right from the get go, using a total of only .2 gallons over the same 10 minute time period.
Let's say they both use .1 thereafter.
In actuality, they both used .2 gallons to reach temperature, but the CR used it quicker and reached temperature quicker. So it's not using more fuel to get to temp, just using the same amount faster. For the full time period of 10 minutes it takes the ALH to reach temp, the CR used .1 gallons more than the ALH, but operated with heat 5 minutes sooner.
In this scenario, the ALH is achieving better overall FE, and bearing out your short trip statistics between the two. This would tend to prove out if longer commutes showed a closer result between the two as warmup time diminished as a factor of overall operating time. Is this along the lines of what you are saying?
Seems a fair trade for warmth, actually. I don't think any ALH drivers in MN would mind if their cars heated up quicker in January
