Re: Transit updates from SMB?
 

In my opinion whether it's enough for a lot of prospective buyers will depend on what tow ratings Ford gives all three engines.

I haven't seen Transit Tow Ratings yet, but if I look at the F-150 with similar V6s, there is a lot of difference between EB and standard V6. Effective axle ratios are not the same due to smaller Transit tires, but a rough comparison has the GCWR for the standard V6 at 11,700 pounds and the EB at 16,900 pounds (depends on models but you get general idea).

If it remains in that approximate GCWR range, the std V6 Transit will have the same problem as the ProMaster. When converted to a camper which adds a lot of weight, there won't be much capacity left for towing. A T-350 van with GVWR of 9500 pounds that weighs close to 9000 pounds loaded may not be able to tow much more than 3000 pounds unless it gets an engine upgrade. And DRW models with their higher GVWR will make a "possible" low GCWR even more important.

Seeing new ProMaster-based RVs at the Houston RV Show limited to around 2000-pound trailers was disappointing. I'm hoping Ford can do better without forcing an expensive engine upgrade.

Re: Transit updates from SMB?
 

Agreed 100%. That's why I said "van". For towing, the EcoBoost is the way to go for sure (or of course a cutaway E-series with the V10).

I don't think the ProMaster would benefit from more power anyways. All that would do is make more smoke as the front tires grasp for traction. I think our V6 Camry is pushing it for too much power in a FWD. It even has equal-length half-shafts but still has crazy torque steer when you get on it, since it doesn't have a fancy diff like the go-fast hatchbacks out there.

Re: Transit updates from SMB?
 

Good thing that's nothing like putting $120K into a van. :b1:

I know apples and oranges, but I couldn't resist.


Herb

Re: Transit updates from SMB?
 

Thanks for the reply.

I am likely the least knowledgable person here on motors and how to objectively assess them.

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

Re: Transit updates from SMB?
 

I wonder if FWD power limits should be considered on an absolute basis, or if it's not better to think of it as a function of vehicle weight; particularly on vehicle weight resting on front driven wheels. My "guess" is that if you can put 300 HP in a 4000-pound FWD car, then 600 HP in an 8000-pound FWD van with similar weight distribution would not be much worse. Please note I'm not suggesting that anyone should put 600 HP in a FWD van. Mostly because it's not needed. But if the drivetrain was designed for that much power, I don't see why it would spin wheels for lack of traction much differently than a performance FWD Acura. For the most part traction should be proportional to weight over driven wheels -- everything else being similar. Granted FWD tends to unload front wheels when pulling or accelerating hard, but due to very long wheelbase this transfer of weight is minimal.

FWIW, I wish Ford would bring the FWD and AWD Transit to US. The FWD version of the mid-roof model would be well suited for Class B conversions.

Re: Transit updates from SMB?
 

Touché

A good one Herb.

Re: Transit updates from SMB?
 

No problem Rob, I enjoy technical discussions as long as they don't turn into arguments.

The thing to remember is that the vehicle's transmission changes (or converts) both engine torque and engine speed between the crankshaft and the driveshaft simultaneously. If we looked at just one of these two, either RPM or Torque, by themselves it's impossible to compare much of real value to us. Also the amount of torque and speed that is changed across the transmission depends on the selected gear ratio.

I don't want to bore with meaningless examples, so I'll try to find an applicable real-world one for the Transit. If I can find one that is easy to follow I'll post it later. Unless you have a specific issue or question you'd rather discuss.

Re: Transit updates from SMB?
 

When it comes to traction, torque is what matters, and a large van generally has more torque than an similar HP passenger car, especially considering transmission and final drive ratios. Also, it will be harder to keep the weight bias forward in a van, simply because there is so much cargo area, and the engine (in the ProMaster at least) doesn't really add any substantial weight compared to a car motor. But probably most relevant is how center of gravity affect weight transfer (higher = more). So in the end, I don't think traction is scalable.

Re: Transit updates from SMB?
 

As I implied above, all vehicles transfer weight back when accelerating and or pulling a load forward. In the case of RWD it adds weight (and thus traction) to driven wheels. With a FWD vehicle the transfer "unloads" the front wheels. But as I stated above, the percentage of weight that is transferred not only depends on height of center of gravity, but also on length of wheelbase. The higher the CG the more transfer, but the longer the wheelbase the less weight will transfer from front to rear axle.

And this ratio is very scalable. A ProMaster with 159-inch wheelbase can have a much higher CG than a car with 100-inch wheelbase before the same percent of weight is shifted back under acceleration.

Also, according to Motor Trend, a long PM has a weight distribution of 62/38 F/R. Depending on the build, a PM camper van could easily maintain about half of the weight over front driven wheels. And if heavy items like generator, batteries, propane tank, holding tanks and so on are added low on the unit, then the CG shouldn't be that high anyway -- at least not in proportion to long wheelbase.

And let's not forget that weight transfer due to hard acceleration is only an issue when there is enough traction to accelerate fast in the first place -- like on dry pavement. On wet or slippery roads acceleration is limited so there isn't as much weight transfer anyway. In these cases of slippery surfaces, higher percent weight over driven wheels is more important. Hence why FWD cars usually exhibit better traction on snow and ice.

Re: Transit updates from SMB?
 

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.