Grit dog wrote:4x4ord wrote:Grit dog wrote:
So 4x4ord has a point with the overall gearing (Trans od ratios and rear gears) and power the engine puts out.
But What he is actually saying is the 4.30 geared Ford doesnโt โneedโ that low of gears and there may be a small fuel consumption advantage to the taller gears when cruising empty. I doubt youโd see any measurable difference hooked up heavy. Any small efficiency on the engine end of lower rpms will still have to drive through taller finals.
Likely a wash.
My old Mega is a good example of what Iโm saying above. Even with taller than stock tires, the shallow OD ratio puts it at 2000rpms just a little over 60 mph and cruising at 85mph is like 2600-2700 rpms. Truck will do it all day long but Iโve driven similar trucks with a deeper OD and it seems the fuel economy is not much different.
So many conditions affect fuel economy, the gearing is only a small part of the equation.
Regardless of what the president of the Ram mafia says, by the numbers a new 4.30 450 Powerstroke IS king of the hill right now on all fronts when it comes to capability.
Tests have been conducted on Agricultural tractors by Nebraska Tractor Tests and have shown that when 1/2 of rated HP is needed a tractor will burn nearly 30% less fuel running the engine at 80% rated engine rpm vs running at full rated rpm. The same is likely true of the Powerstroke. If 235 HP were needed to pull a very heavy trailer it should be expected that running at 2080 rpm would burn about 70% the fuel vs running the engine at 2600 rpm while running the same road speed. When less HP is required (such as what is required to pull a heavy RV .... 110 - 140 HP)running the engine at 1600 rpm could potentially save significantly more fuel.
I don't disagree with you, theoretically, however, realistically, unless all the online calculators are wrong (and I'm not busting out the statics and dynamics book tonight), 24-28k gross, 96 sf frontal area at 70mph is average around 230-250hp to overcome air drag and rolling resistance.
That's average. No head or side winds, no grades, etc.
Yes, the new Powerstrokes make impressive HP down low, but it's not quite as rosy as it seems, IMO.
And you're talking roughly 1600rpms vs 2000rpms on a F450 with 4.30s vs 3.55s. You're not going to hold 10th gear with 3.55s with any large trailer at 70mph except in a vacuum.
So down it shift a gear or 2 and then pops back up when the wind stops for a second, then down when you go up the other side of a dip in the road and back up when you go down the dip, so then yo ulock it in 8th gear and there you are...
Bobtail or light trailers, sure 3.55s will hold top gear all day, likely. And drop a couple/3/4 gears for the BIG loads.
I agree that deep gears aren't needed except for BIG loads and even at that, with 10 cogs, there's a gear for every condition.
But if you're tugging around the stuff that requires a 450 chassis, why not have the most snort behind the skinny pedal?
Bet you're not saving appreciable fuel unless running light weight, but then that's not what the truck is made for with 4.30s although it'll still do 10x better than my old 6 speed with higher gears.
Let's take a look at the numbers from a little different vantage point. Here is the test results of a Cummins ISX 15 liter engine:
Running at peak HP it was able to operate at 600 maximum HP while burning 225 lbs of fuel per hour .... 0.37 lbs of fuel per HPhour. A pick up truck running a part load is not going to be able to get that kind of fuel economy but just for kicks lets say pulling a heavy RV a pick up consumes 0.4 lbs per HpHr.
If at 70 mph you are getting 8 mpg in your pick up pulling a heavy RV you're probably not going to be thrilled with your mileage but even so you'll only be burning 8.75 gallons of fuel per hour. There is about 7.2 lbs of fuel in a gallon so 8.75 x 7.2 = 63 lbs of fuel per hour which means the truck was producing 63/.4 = 157 HP.
