Transit updates from SMB?

[carringb]

Great example and explanation of HP vs Torque!

I actually don't mind letting an engine rev if that's what its made to do. But, I often am in a hurry. I'd rather spend my limited time playing than driving, especially when the drive involves the entire Midwest or California's central valley. And, I like having more power than I need. I don't want to spend my time in the truck lane, or get stuck behind a Prius going 15 under the speed limit, until of course they get to the passing lane and speed way up to prevent anyone from passing in the passing zone. I'd rather just make a quick pass whenever its safe and not have to deal with them again.

[WhitH]

Carringb, I've passed that same Prius on 126 and on 58 many times. The consistency is amazing....

[EMrider]

Originally Posted by Chance

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.

I think that I get it now, or at least have a much better understanding. Very helpful, thanks.

My bias is also to not rush when driving and take the scenic route.


Rob

[dhally]

I would be pretty skeptical about putting a turbocharger into a van (ecoboost). This is based on my experience with ONE vehicle. I had a 1990 Mazda 626GT, which had a 2.2L turbocharged gas engine. I normally got 27 mpg, which was probably 2 to 4 mpg better than a similar V6. When I spooled up the turbo, it accelerated like a cut cat! (It could have used some traction control.)

The problem was, the engine was cooked at 150,000 miles. I had to replace every piece of rubber in the engine compartment, the exhaust manifold studs broke, and at the end it started loosing compression.

I could have driven it like an I4, but the hooilgan in me always wanted just a "little" boost everytime I shifted through the gears. Then both my daughters used it to learn to drive and I'm sure they had heavy feet. Bottom line, a turbo just adds heat and stress which shortens engine life. I suppose this would be OK for a passenger vehicle where it would be sold at 100,000 miles. But a camper van has a huge investment in upgrades, so I want my chassis to last 200k or 300k.

The ecoboost does sound like magic - more power, better economy, and all in a smaller, lighter package! It remains to be seen how long they last.

[carringb]

In case you haven't seen the Torture Test video series.
[youtube:37bhqkqj]

[WhitH]

I'm wondering what the fuel economy would look like in our little comparison. The standard V6 revving at 4000 rpms vs the Ecoboost at 2500. I'd venture to guess they would be very similar or the Ecoboost would be slightly better. If that were the case then the next discussion begins, how many miles until the price premium of the Ecoboost justifies itself through mpgs gained? It likely doesn't happen in an unladen/stock weight vehicle, but it might be a different story with a loaded down camper van.

[carringb]

Originally Posted by WhitH

I'm wondering what the fuel economy would look like in our little comparison. The standard V6 revving at 4000 rpms vs the Ecoboost at 2500. I'd venture to guess they would be very similar or the Ecoboost would be slightly better.

At the exact same HP output, the EcoBoost will actually consume a little more fuel. This is why even in the granny-driving EPA tests the 3.7L does slightly better. Turbos use energy to spin those turbines. Most of it goes back into the motor in the form of boost, however a lot is still lost as heat at the turbos and through the intercooler. While there is a fuel-consumption/RPM relationship at constant throttle for a non-turbo motor (because atmospheric pressure is constant, and volume is determined by the cylinders pumping), this relationship doesn't work out as well for turbo'd motors because air-volume relates more to boost pressure than to engine-RPM.

Where the EcoBoost shines is comparing to a larger motor. The EcoBoost makes about the same power as the 6.2L over most of the RPM range (more at lower RPMs, less at upper), but the EcoBoost is only using lots of fuel under boost while the 6.2L is sucking fuel the entire time.

So yes, if you only need the HP of the 3.7L, it will be the most economical choice. There will not be an efficiency payback for the EcoBoost. It only "pays-off" when comparing to a larger-displacement motor.

[WhitH]

Just hoping to give somebody another excuse to pony up the Ecoboost, but alas you've crashed that delusion on the rocks of reality. In all seriousness your knowledge is much appreciated. I look forward to seeing the new Transit when it comes out. Like has been expressed, there will be several engines to choose from based on personal taste and need. Here's hoping the 4x4 conversion guys all get on board so there will be plenty of choices there as well.

[Chance]

Originally Posted by WhitH

I'm wondering what the fuel economy would look like in our little comparison. The standard V6 revving at 4000 rpms vs the Ecoboost at 2500. I'd venture to guess they would be very similar or the Ecoboost would be slightly better. If that were the case then the next discussion begins, how many miles until the price premium of the Ecoboost justifies itself through mpgs gained? It likely doesn't happen in an unladen/stock weight vehicle, but it might be a different story with a loaded down camper van.

In my opinion this is a very poor example on which to base relative fuel consumption. I say this because both engines are producing around 200 HP, which means a typical driver spends very little time in that power range or we'd be getting around 5 MPG.

At around 70 MPH, a van is using more like 50 to 60 HP or so. If it were much more than that it could not deliver fuel economy in the range of 18 to maybe 20 MPG.

At 200 HP at 2500 RPM, the EcoBoost may do slightly better than the std V6 at 4000 RPM. But when cruising or driving normally at power well below 100 HP, the standard V6 should be slightly more fuel efficient (if everything was equal).

And the reason is that both engines will end up in 6th gear and thus running same RPM and torque to maintain same vehicle speed. ASSUMING both have same axle ratios. Which they probably won't, particularly for high-roof vans.

If EcoBoost has 3.31 and 3.7L V6 has 4.10, the two engines will run different RPM and torque. And this should help the EB. Whether enough to equal or better the standard V6 in fuel economy is anyone's guess. If driven equally I doubt there will be much difference in any case.

As carringb said, the EB may have a payback when compared to a 6.2L V8, or an Econoline V10 which has comparable power, but I doubt it will pay for itself against a 3.7L V6.

[Chance]

Originally Posted by WhitH

I'm wondering what the fuel economy would look like in our little comparison. The standard V6 revving at 4000 rpms vs the Ecoboost at 2500. .....cut......

I'd seen the information below before but it took me a while to find it. Hopefully it answers your questions without being too technical to the point of being confusing.

The data here (on left) shows the baseline non-turbo engine's fuel consumption at 2000 RPM. On the right it shows the general Brake Specific Fuel Consumption map for the entire torque and RPM range.

Rather than showing torque in lb-ft (on y axis) which would only apply to one engine size, they show it as "brake mean effective pressure" so it standardizes it to apply to a 4 or 6 cylinder engine the same. Or any other size including one-cylinder test engines. So torque is shown as average cylinder pressure, and in units of "bars".

Anyway, we can see from this data that a modern engine like the Transit's standard V6 has lowest specific fuel consumption when operated in the range of the dark green oval, and almost as good in the lighter green oval. A speed of 2500 RPM and a torque represented by 9 bars is ideal to minimize fuel consumption, but depending on required horsepower, any speed between 1800 and 3200 RPM is not too bad provided torque is in the range of 7 to 10 bars.

And the light green oval shows that pretty low fuel consumption can be obtained at speeds of up to 4000 RPM as long as torque is not too low.

By the way, the lowest fuel consumption of 250 grams per kilowatt-hour is about 0.41 pounds per horsepower-hour. It's very good for gasoline engine.

If this is not too confusing to the point of being useless I'll then compare to EcoBoost data.