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Old 02-17-2014, 05:12 PM   #1
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Default How much power is enough?

With all the new models and engine/transmission combinations showing up, there have been quite a few sidebar conversations about if they are powerful enough, or not. Lots of good opinions, and considerations have been brought out. Obviously, blasting up any grade, fully loaded, at 70 mph would be enough power, but a bit unrealistic.

I guess the question is: In what kind of driving does a lack of power become an issue, and how much power do you have to be down before it is too much?

We have a 2007 Chevy Roadtrek 190 with the 6.0 engine 300hp/360 torque.

I think I put the most irritating is when we get in rolling hills on the two lanes, where the van downshifts on nearly all of them, or loses 20+ mph if you drive it so it doesn't downshift (which drives everyone behind you nuts). I haven't seen grade markings on these hills, but are probably 3-4% maybe. They are usually two lane, so you can't pull over and let folks by, unless there is an occasional truck lane, and it sucks to leave it in the lower gears the whole time. I think it would take quite a bit more engine to not have this happen, especially if there is a headwind.

Low grade climbing acceleration from stops would be next for us, as again it is often two lane, traffic, and lots of backup behind you. We find ours fine in this respect. On a trip in the UP of Michigan last year we came out of a small town, from a stop, behind a new (1-2 years it looked like), Sprinter class C, and it was very slow to go up the moderate grade that went on for a few miles. It was not even steep enough to make our 6.0 go down a gear, so we were very surprised. When we got to a truck lane and passed it, we could hear that it was running hard, so the driver was not backed off on throttle. I think that would be getting into the too low on power for us, if it is typical, as he did hold up traffic badly. I think they can weight in the 12,500# range, so a regular b would do much better, I would think.

Next very steep, low traffic roads next. The Chevy climbs them well, but heat can be an issue, and often there are limited places to pull over to cool off.

Mountain passes on the freeway are actually fairly low on our list of what is important for power. There are multiple lanes, truck lanes, pull offs to cool off, etc, so as long as we are not any slower than the semis, we would be fine. We have limited experience in this area to this point, but expect the Chevy to do fine, as long as we can keep it cool (we have trans cooler, added electric fan).

Once I thought about it, and made the list, I was a bit surprised by the order. I assumed the long mountain passes on the freeway would be higher up on the list. I think it is because we have enough power to go up them reasonable, even if it is not at posted speeds. I don't know how slow would be too slow for us, but I would think you would want at least 30mph. After that it becomes a matter of the stress of holding up others unnecessarily or putting up with constant shifting of the transmission.

The smaller engines will shift down more, and be slower off the line and uphill, which for us would be a worse penalty than slower climbing of mountain passes on the freeway. I am sure holding up traffic would be much more of an issue.

There is also the question of the engine and transmission design. In general, the higher average % of max power you use, the shorter the life of the engine. Most engines are designed for high output levels all the time. Semi engines are designed to pull at or near max all the time. The Sprinters are probably close to that. I think that GM does some things different in the 4.8 and 6.0, as they go in the heavier light trucks than the other V8s, but they are not made for full output all, or most, of the time, I think. The Ford V10 is a very good high load engine that does very well in the heavy vehicles. The Ecoboost probably will be able to pull hard a lot, as it was designed as a turbo truck engine, plus it has so much torque and hp, it will be at a low % of output most of the time, and with the turbo, they turn down the power if it gets hot or stressed, on the fly. At this point, we don't know how the new engines are designed, or if the high output will be hard on them.

Quite a while ago, I did get a ride in a Toyota Dolphin, and it was way off the end of underpowered, even on the flat, no wind, so at least we know there is a limit to lower power, for us.
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Old 02-18-2014, 12:40 AM   #2
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Default Re: How much power is enough?

I have owned 2 VW Westfalia campers of different vintages. The first had the VW rear mount engine and the second had the Audi engine up front. They were absolutely great for traversing the back fire roads of a National Forest but severely lacking out on the road. The slow acceleration, even on the flat, could be downright dangerous in a highway merge lane.

I also owned a class B Coachmen on a Ford chassis that had some oomph on the flat, but struggled in the mountains that we love so much. It struggled accelerating from a hairpin turn on a steep road and was continually downshifting on hills in the mountains, even at highway speeds. It would heat up on both steep uphill and downhill sections.

My RT Agile feels much more at home on the steep twisty roads near me and in the high Sierra. It also provides a lot of engine braking without heating up. Note that I have a 6 cyl Agile. I test drove the 4 cyl on some twisty hilly roads and it seemed to be working a bit harder and downshifting a lot (sometimes going down two gears on the same short grade).

I haven't had a chance to give it the more thorough test of crossing Tioga Pass (9,950') yet because of the snow. The roads in that vicinity are a pretty good test, with a lot of tight corners at a 45 mph speed limit at altitude.
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Old 02-18-2014, 01:19 PM   #3
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Default Re: How much power is enough?

I'm trying to pull together accurate HP & Torque specs for the new vans. It's harder than I thought Lot of site with lots of different info out there. Please let me know if any of the numbers below need to be corrected.

2014 Ram ProMaster:

3.0L ECODIESEL I4
174 horsepower @ 3,600 rpm / 295 lb-ft of torque
Six-speed automated manual transmission

3.6L PENTASTAR® V6
280 horsepower / 260 lb-ft of torque @ 1,400 rpm
Six-speed automatic transmission

2014 Mercedes Sprinter:

OM651 2-Stage Turbo Diesel Engine
161 horsepower @ 3,800 rpm / 265 lb-ft of torque @ 1,400 to 2,400 rpm
Seven-speed 7G-TRONIC transmission

OM642 6-Cylinder Diesel Engine
188 horsepower @ 3,800 rpm / 325 lb-ft of torque @ 1,400 rpm
Five-speed transmission

2015 Ford Transit:
Six-speed automatic transmission

3.7-liter V-6
266 horsepower @ 6,500 rpm / 249 lb-ft of torque @ 4,000 rpm

3.5-liter EcoBoost V-6
300 horsepower @ 5,000 rpm / 400 lb-ft of torque @ 2,500 rpm

3.2-liter turbodiesel I-5
197 horsepower / 347 lb-ft of torque

------------------------------------------------------------

The EcoBoost in the Ford seems to be the standout particularly if highway cruising speed is obtained at around 2,500 RPM. It might nicely handle the rolling hills that booster describes. Is it an expensive option? Why even offer the 3.7 liter?

My '97 Savana Van specs (from the brochure):
6.5 L Turbo Diesel V8
190 horsepower @ 3,400 rpm / 385 lb-ft of torque @ 1,800 rpm

It doesn't shift much when I'm highway cruising at around 2,000 RPM.

Re: the Ford numbers above - I couldn't find the specs on Ford's site so they might not be accurate. If you know of a good source for the info let me know.
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Old 02-18-2014, 01:59 PM   #4
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Default Re: How much power is enough?

The Fords do look to be the clear winners in the power categories. I agree that the Ecoboost might be a very good solution to the rolling hills, as the turbo can increase the output at the same rpm much more than a non boosted engine can, and they have a lot of power available at the right rpm range. From what we have heard here, most of the vans seem to run about 2200 rpm at highway speed. With the torque peak that low and a 5000 rpm max hp, it is definitely tuned to the low rpm, pulling side of the range. Torque and hp curves cross at 5250 rpm, so at 5000 rpm that engine would still be making around 300 ft-lbs of torque, which is nearly as much a the torque peak on the most powerful non Ford (Sprinter V6 at 325 ft-lbs, 1400 rpm). The extra 3.5 times torque multiplier at 5000 vs 1400 (done with gears) would give it the equivalent of over a 1000 ft-lbs at 1400 rpm. That is the torque that the rear end sees.

I had seen some slightly higher numbers on the Ecoboost, but they were from pickup truck applications, which are often higher because of packaging issues with the vans that cost power.

Sometimes Edmunds will have information that is hard to find for specifications, but they haven't been as good lately.

I do like the way the numbers look for your Savana. I would expect it to pull very well at the highway speeds and rolling hills, as it is very close to the rpm it likes.

I think Ford probably has chosen the better path for the US market. Both their engines are at the top for power. I think they learned lowered power doesn't sell well in heavy vehicles with their pickups (granted a different user, but most of the vans will go to commercial use). If they can keep the fuel efficiency close to the others, I think they will have an advantage once folks drive them.

I think I need to go to a Ford dealer, and pretend I need a pickup truck, so I can actually drive an Ecoboost to see how it feels in the real world.
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Old 02-18-2014, 02:49 PM   #5
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Default Re: How much power is enough?

I had dug out some torque curves on the 6.0 engines a while ago, and finally found them.

Here is the 6.0 that is in our 2007 Express. It is one of the last before the went to variable valve timing.



Here is the 6.0 for 2010 that has the variable valve timing, and appears to be the same as the current version.



The first thing you notice is that the VVT engine is rated at less than its max hp, most likely do to not being able to keep it cool at higher levels. They probably limit the rpm at that point. The VVT engine also loses low end power compared to the older engine. The VVT engine is probably a pickup engine where they go for more hp and aren't limited by cooling, and used to reduce engine variations in production. It isn't a great choice for this application as it doesn't match the power curve to the application very well.

The second thing you see is that the older 6.0 has within 10 ft-lbs of torque when compared to the Sprinter V6 (the most powerful non Ford) at the Sprinter torque peak of1400 rpm. It climbs from there and has more torque than the V6 peak of 325 ft-lbs all the way up to 5000 rpm. Since the torque converter will flash at 1500 rpm or more in a heavy vehicle like this, you would never have less than 325 ft-lbs of torque available.

If the Ecoboost curve looks anything like the 2007 curve, and I think it will be much better based on the numbers, it should severely outpull anything else on the Marko's list, and it will not lose power in the mountains like the 6.0. Whether the the others are "powerful enough" will be a personal choice, and time, economy, and sales will dictate their success.

Those extra 65 ft-lbs of torque that Marko has at cruise would surely explain his less downshifting.

Full torque curves used to be readily available on the manufacturer's sites, but are getting very hard to find. If anybody knows of any sources, it would be great to hear about them. I found the Chevy ones by accidentally getting into a database of other specs that had a section on the engines, also. They eliminated access to it very shortly after that. It would be very interesting to see the actual curves on these engines, rather than just two points.
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Old 02-18-2014, 04:09 PM   #6
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Default Re: How much power is enough?

Booster - what axle ratio does your Chevy have? My van has the 3.73. The 4.10 was an option and I think it would have been nice to have. My van would have a bit more "oomph". That would be nicer when it comes to passing on the highway and also better for towing.
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Old 02-18-2014, 05:09 PM   #7
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Default Re: How much power is enough?

From some fairly extensive (and sometimes worrisome) experience, when faced with gradient climbs at various altitudes above sea level and in varying higher ambient temperatures, we have found that any grade that is greater than about 6%-7% uphill, in temps > or = 70F, at altitudes above 1,000 feet, and at reduced speeds below 40-50mph, are absolutely the worst situation for our 2002 C190P with the 5.7L V8. It exacerbates the potential over heating issue, which we've had to deal with most often. The usual scenario is when we get caught behind a slower moving vehicle, like a semi truck, crawling up the same grade, in warmer (70F+) summer temperatures, because we weren't watching or I didn't estimate the speed of the vehicles in the right most lanes accurately, and take the opportunity to move left to pass in heavier traffic situations in all lanes. Trapped in the right lane by overtaking traffic in the left, behind a slow moving vehicle, in the summer, pretty much ruins my day.
If that makes sense?
I've been caught all over the continent, at different times on different trips, in this scenario.
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Old 02-18-2014, 07:01 PM   #8
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Quote:
Originally Posted by markopolo
Booster - what axle ratio does your Chevy have? My van has the 3.73. The 4.10 was an option and I think it would have been nice to have. My van would have a bit more "oomph". That would be nicer when it comes to passing on the highway and also better for towing.
Ours does have the 4.10 rear end.
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Old 02-18-2014, 08:22 PM   #9
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Quote:
Originally Posted by Mike
From some fairly extensive (and sometimes worrisome) experience, when faced with gradient climbs at various altitudes above sea level and in varying higher ambient temperatures, we have found that any grade that is greater than about 6%-7% uphill, in temps > or = 70F, at altitudes above 1,000 feet, and at reduced speeds below 40-50mph, are absolutely the worst situation for our 2002 C190P with the 5.7L V8. It exacerbates the potential over heating issue, which we've had to deal with most often. The usual scenario is when we get caught behind a slower moving vehicle, like a semi truck, crawling up the same grade, in warmer (70F+) summer temperatures, because we weren't watching or I didn't estimate the speed of the vehicles in the right most lanes accurately, and take the opportunity to move left to pass in heavier traffic situations in all lanes. Trapped in the right lane by overtaking traffic in the left, behind a slow moving vehicle, in the summer, pretty much ruins my day.
If that makes sense?
I've been caught all over the continent, at different times on different trips, in this scenario.
You need to do the Nascar pop out of line for air routine, or drop back from anything big. The airflow blocked is huge, and will cause the temp of your van to climb. When we had electric fans, and marginal cooling ability on our old Challenger, you could actually see the temp gauge move when you came up behind things, and big trucks made it go up very quickly. We could even tell if the wind was against or behind us by the temp we ran. It is very possible that your heat issue is not as much speed related airflow, as it is blocked airflow. Either way, this is the kind of condition that an auxiliary fan very well could help.
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Old 02-18-2014, 09:13 PM   #10
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Default Re: How much power is enough?

It's not always easy to pop out from behind these things in heavy traffic on the interstates, or on a 2 lane switch back road, behind some pinhead in a sedan doing his best uphill sightseeing tour bus speed. We've been caught on I-17 southbound to Phoenix, on the uphill climb to the top of the Olympic ski hill in Lake Placid, and out in Cape Breton and Gaspe, once each. If there were pullouts to take a break, we would, but they don't have them where I usually get stuck. There have been other times in other places, but I can't recall the exact co-ordinates. Probably on 89 south of Page, AZ once or twice, as we've been through there often. It's more frustration at letting us get stuck in the slow lane in traffic, than any real danger, although I've watched the analog dash water temp gauge, and more recently the ScanGauge numbers rise, as we slow down in the conga line and slowly bake. If I can keep our speed above 35-40 mph, it's not as bad and we're getting air flow through the grill, but we've literally been slowed to a crawl in some strange traffic scenarios. I try to watch for and predict the "danger zones" now, if at all possible.
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