Originally Posted by EMrider
I was lost because of the substantial difference in EB and 5.0 torque at 2500k and 5000k RPMs respectively, in light of the comment that the EBs low end pulling capabilities were exaggerated.
Reading further I suspect that this mat not be the best or most relevant point of comparison......but still don't fully understand why. I will stay tuned to this thread.
Rob, I'm not sure if this will help or not. I couldn’t find a much better real-world example so let’s look at the one already mentioned above that caused some confusion. It’s fairly straight forward and not too hard to follow because the numbers are close enough that it makes it easy to compare. That’s not always the case though because transmission gear steps may not match differences in engine speeds that you may be interested in comparing.
First keep in mind that traditional transmissions do not create any “power” whatsoever. They simply trade torque for speed or speed for torque depending on gear ratio. And by “traditional” transmission I mean those that are not for hybrid vehicles that may include electric motors inside transmission.
Since Transit engine specs are not available yet, let’s use the F-150’s engine specs from previous post. The 6R80 transmission will be used in both F-150 and Transit as far as I know. Published gear ratios appear identical. So let’s compare the standard V6 in second gear against the Eco-Boost in third gear because the results are close when both engines are at rated peak-torque RPM. I’m not trying to make a case for one versus the other being better, just simply stating how “gearing” works so you can run your own numbers and determine what is important to you.
6R80 Gear Ratios (from Transit and F-150 specs):
1 – 4.17
2 – 2.34
3 – 1.52
4 – 1.14
5 - .86
6 - .69
R – 3.40
Std V6 (from F-150 specs):
302 HP @ 6500 RPM
278 lb-ft at 4000 RPM (212 HP)
EcoBoost (from F-150 specs):
365 HP @ 5000 RPM
420 lb-ft @ 2500 RPM (200 HP)
To keep numbers simpler let’s assume the transmissions are 100% efficient. They won’t be in the real world, but for comparison it won’t make much difference since 2nd and 3rd ratio efficiencies should be similar. Also to keep it as simple as possible let’s assume torque converter is locked so there is no slippage.
Std V6 in 2nd gear:
278 lb-ft engine torque X 2.34 gear ratio = 650 lb-ft at driveshaft
4000 RPM / 2.34 = 1710 RPM at driveshaft
Eco-Boost in 3rd gear:
420 lb-ft engine torque X 1.52 = 640 lb-ft at driveshaft
2500 RPM / 1.52 = 1650 RPM at driveshaft
As you can see there isn’t a lot of difference as it affects what the driven rear axles see. As long as the vans have equal axle ratios we can conclude that the standard V6 will pull just as hard at 4000 RPM as the EB at 2500 RPM. But that is “ALL” this says. And nothing more. Regardless, I can already hear all the “buts”.
Please understand that I’m very aware that there are many other factors one can consider like those mentioned by other members. For example, the EB can also double its speed from 2500 to 5000 RPM while the standard V6 can’t go from 4000 to 8000 RPM. And while that’s good to know and may be of great value to some, it doesn’t change the fact that in some cases a less powerful engine may be enough if the driver is willing to use higher engine RPMs instead of higher engine torque to get the job done.
Whether a driver prefers pulling a trailer up a steep hill at 420 lb-ft at 2500 RPM under boost versus 278 lb-ft at 4000 RPM under no boost is a matter of choice. I normally buy vehicles in large part based on value, and since I’m not in a big hurry when camping, I’m also willing to climb mountains at slower speed in a lower gear if necessary. As mentioned before, as long as Ford rates the standard V6 with a high-enough GCWR to meet my occassional towing needs (so it doesn’t void warrantee) I would not hesitate buying a Transit with the base engine. I also like simpler stuff and the standard engine meets that criteria better for me.