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Old 04-21-2018, 12:57 AM   #81
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Originally Posted by gypsydad View Post
Pteck- we get it; you love your SUV... But have you ever owned a 3/4T diesel PU for pulling an AS? Have you driven one for an extended period pulling a 27' or larger AS in recent years? If not, you may not get the point most of us owners are making, vs gas or other TV's. Just saying...the 3/4T diesels are pretty darn nicely equipped for the job of towing a larger AS...easier to pull, stop, control, and engine brake is heavenly...plus theres plenty payload with several people on board, a generator, firewood, gas, kayaks, camping gear, etc, etc, etc... We get it; you love your SUV...enjoy.
The Thread was gas vs diesel F250, I thought?

To repeat my earlier post; this is my first F250 Diesel 2017; big truck to drive compared to my F150 EB. Love it for the job it does pulling my 28'. 13mpg pulling; 17mpg without trailer. Service and fuel cost a bit more. Does the job exceptionally well pulling the 28' AS. Service manager at Ford I talked with last week said he has same year (2017) F250 6.2 gas; said his mileage is not close to mine pulling his 28' Jayco and wishes he had gotten the diesel. Hope this helps.
Er? I'm not off topic in my post. I'm specifically trying to understand the Ford 250 diesel service issues and procedures relative to the gasser f250. Or if it's both, that's bad on Ford, which already has a less than steller reliability record. As a product designer and engineer myself, that's some serious trade off there in regards to serviceability. In a truck!

I personally don't care what kind of performance or torque it offers with that BS cab off requirement as I couldn't work on it myself. Even though I have a lift in my own garage. Sounds like they're overly pushing their motors too.
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Old 04-21-2018, 05:43 AM   #82
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Er? I'm not off topic in my post. I'm specifically trying to understand the Ford 250 diesel service issues and procedures relative to the gasser f250. Or if it's both, that's bad on Ford, which already has a less than steller reliability record. As a product designer and engineer myself, that's some serious trade off there in regards to serviceability. In a truck!

I personally don't care what kind of performance or torque it offers with that BS cab off requirement as I couldn't work on it myself. Even though I have a lift in my own garage. Sounds like they're overly pushing their motors too.
The Dodge and Duramax are just as much as a pain to work on as the Ford. The engines in new trucks are further back than they used to be. If you think itís easy to work on any of these engines with the cab in place you obviously have never worked on them. Unless you have experience, best stick to air filter changes and leave the rest to the professionals.

If you canít do a cab off on these in 2 hours you just arenít any good. And once itís off, repairs are straightforward.
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Old 04-21-2018, 07:40 AM   #83
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The Dodge and Duramax are just as much as a pain to work on as the Ford. The engines in new trucks are further back than they used to be. If you think itís easy to work on any of these engines with the cab in place you obviously have never worked on them. Unless you have experience, best stick to air filter changes and leave the rest to the professionals.

If you canít do a cab off on these in 2 hours you just arenít any good. And once itís off, repairs are straightforward.
Yes, I haven't worked on a new gen 3/4T. Are you guys using an overhead hoist or just some adapter to a lift for the cab?

I consider myself quite proficient at wrenching. I can drop the driveline in most front engine/RWD in about 4 hours in a home garage. Or a Porsche turbo in 8hrs with its crazy small tool clearances and 4wd trasnaxle.

Is this just the diesel varients or do the gassers need cab off to get at things too in the Ford and Dodges?
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Old 04-21-2018, 09:45 AM   #84
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What it means is that since you were not there, there are these things called temperature gauges that will tell you when you are reaching a condition that will switch on the MIL and put the vehicle into limp mode. Pulling over to let things cool down works well, but is time consuming. Also, an infrared temp monitor can display the brake temps. But enough of hijacking this thread, I'll let you armchair engineers continue your debate. Happy trails!
Would it have been hot or overheated without the trailer?

Fuel aroma isnít the thing. Itís trailer brakes that matter.
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Old 04-21-2018, 12:02 PM   #85
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pteck covered it. More fully, because it is an interesting story, the compression release brake was invented to rectify a deficiency when an early Cummins diesel was retrofitted into a highway truck, circa 1931, they overheated the service brakes on a descent, and Clessie Cummins described it as "we had escaped certain death by inches". The patent holder was Clessie Cummins, but he had left the Cummins engine company by that point, so looked for a manufacturer. He found the Jacobs manufacturing company, who were looking for products to make, and that is why we have what became known as the Jake Brake. Not the same mechanism as an exhaust brake like on pickups, but the same effect, and that is where it started.

Incidentally, that story, including the quote, and the full story of the rise of the diesel engine in transportation applications in North America, is told in the book "The Engine That Could" by Jeffrey L Cruikshank and David B. Sicilia, (1997) from the Harvard Business School Press. it is essentially the story of the Cummins Engine Company over a 75 year period, 1919-1994, but that story is intertwined with the development of diesels overall. I found it a very interesting read, so recommend it to anyone who is interested in how it all came about, particularly if you have an interest in diesel engines. Seems there are lots of posters here who do.

Jeff
........the compression release was used on the earlier cummins engines to start them only..I have driven many of them in the 1960ís and 70ís...get her spining,then push the handle in...they did have compression on the down hill side, you gear down at the top...that was the way it was done before the Jacobs engine brake.....later Williams came out with the exhaust brake....which didnít do much...computers have done a lot....so much better now....my ram engine brake does a good job...for only 400 cubic inches....early cummins were only 700 plus cu in with 74,000 lbs pushin it....later it became 855 cu in...
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Old 04-21-2018, 12:23 PM   #86
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The compression release was used on the earlier Cummins engines to start them only. I have driven many of them in the 1960’s and 70’s. Get her spinning, then push the handle in.
Two different things.

A compression release brake, often called a Jacobs brake or Jake brake, releases compression cylinder by cylinder, at the top of the compression stroke. It is closed on the compression stroke to provide a braking effect.

A manual compression release valve is often used for starting purposes, on everything from small engines to large stationary engines. It released all compression, so that one can get the crank spinning over. It is then closed, and the momentum carries the crank for the next revolution. It is still used on some motorcycles.
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Old 04-21-2018, 05:18 PM   #87
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Yes, I haven't worked on a new gen 3/4T. Are you guys using an overhead hoist or just some adapter to a lift for the cab?

I consider myself quite proficient at wrenching. I can drop the driveline in most front engine/RWD in about 4 hours in a home garage. Or a Porsche turbo in 8hrs with its crazy small tool clearances and 4wd trasnaxle.

Is this just the diesel varients or do the gassers need cab off to get at things too in the Ford and Dodges?
Havenít had to do anything to my gas truck yet but Iím only at 120,000 miles. Cam phasers go out on these but thatís not a cab off job so I may never find out. I looked at mine today and head gaskets look possible (remember these trucks are tall so I would need something to stand on). Pulling the cab isnít that much work. The truck is designed to simplify that. You do have to evac and recharge the AC but by that mileage that should be done anyway.

Cab lift is done with the hoist. At home in the barn I use winches from the beams. I also pull the beds on trucks to do fuel pumps but thatís my preference. Hate dropping gas tanks.
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Old 04-21-2018, 05:55 PM   #88
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Two different things.

A compression release brake, often called a Jacobs brake or Jake brake, releases compression cylinder by cylinder, at the top of the compression stroke. It is closed on the compression stroke to provide a braking effect.

A manual compression release valve is often used for starting purposes, on everything from small engines to large stationary engines. It released all compression, so that one can get the crank spinning over. It is then closed, and the momentum carries the crank for the next revolution. It is still used on some motorcycles.
......I do realize all this...I have run them...many miles.. compression release like I said is for starting....it opens the intake valves...
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Old 04-21-2018, 07:46 PM   #89
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I do realize all this. I have run them. Many miles. Compression release like I said is for starting. It opens the intake valves.
Compression release is an incomplete description. Again, two different things.

Compression release brake is not for starting.

Compression release valve is for starting, but generally works on the exhaust valves, or is a separate valve.
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Old 04-21-2018, 08:09 PM   #90
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Friction is a pretty big thing. Here is some reading on the breakdown of frictional losses.

https://www.researchgate.net/publica...ustion_Engines
Unfortunately the link gives faulty data due to at least one incorrect assumption. This computer model is a case of garbage in garbage out. It might be useful for an overall picture of friction vs rpm, but the numbers are suspect.
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Old 04-22-2018, 12:25 AM   #91
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Unfortunately the link gives faulty data due to at least one incorrect assumption. This computer model is a case of garbage in garbage out. It might be useful for an overall picture of friction vs rpm, but the numbers are suspect.
That is a pretty strong charge. The model discussed in the linked paper was validated with a case study. How has your work shown it to be faulty?
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Old 04-22-2018, 08:10 AM   #92
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That is a pretty strong charge. The model discussed in the linked paper was validated with a case study. How has your work shown it to be faulty?
Here is the part of the model that is faulty that I know of so far.

"The atmospheric pressure (pa) is considered as 101.325 kPa throughout the simulation. As concerns the intake pressure (pi), it is estimated considering that the effective open area (from the air passage) remains constant for throttle open higher than 80 %, and assuming that when the throttle is fully closed, the intake manifold pressure is 10 % of the absolute atmospheric pressure."

What do you think is wrong with these assumptions?
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Old 04-22-2018, 11:19 AM   #93
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Here is the part of the model that is faulty that I know of so far.....

What do you think is wrong with these assumptions?
Not much at first glance. The model shows less than 1% error on that element (pumping losses) when compared to previous studies. The model is designed to show the potential losses in a spark ignited engine. You don’t have a throttle plate, so discount that factor when considering intake manifold pressure drop.

You claimed that the numbers are suspect, but you won’t get any numbers until you use the model to predict real world figures for a specific case. Recall the adage that all models are wrong, but some are useful. The model shows the relative weights of different factors. That is where the utility comes from.

Maybe you should explain why you think the model is faulty.
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Old 04-22-2018, 11:53 AM   #94
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Not much at first glance. The model shows less than 1% error on that element (pumping losses) when compared to previous studies. The model is designed to show the potential losses in a spark ignited engine. You don’t have a throttle plate, so discount that factor when considering intake manifold pressure drop.

You claimed that the numbers are suspect, but you won’t get any numbers until you use the model to predict real world figures for a specific case. Recall the adage that all models are wrong, but some are useful. The model shows the relative weights of different factors. That is where the utility comes from.

Maybe you should explain why you think the model is faulty.
The best vacuum you're going to see on a mild engine at idle is 15 inHg which is about 50% of atmospheric. By the time the throttle plate is open between 40-50%, vacuum has fallen to almost zero (1-2 inHg). When you put a cam into an engine with a lot of valve overlap the idle number drops significantly. I'm sure in today's engines with their VVT and high horsepower that a more performance cam grind is being used. The computer smooths out the rough idle and poor characteristics of the larger cam (but that just a guess on my part).
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Old 04-22-2018, 04:28 PM   #95
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The best vacuum you're going to see on a mild engine at idle is 15 inHg which is about 50% of atmospheric. By the time the throttle plate is open between 40-50%, vacuum has fallen to almost zero (1-2 inHg). When you put a cam into an engine with a lot of valve overlap the idle number drops significantly. I'm sure in today's engines with their VVT and high horsepower that a more performance cam grind is being used. The computer smooths out the rough idle and poor characteristics of the larger cam (but that just a guess on my part).
I suspect you are confusing the 10% figure with a measure of manifold vacuum, or (Pa-Pi), and bringing idle speed into it on the assumption that at idle the throttle is fully closed. We want to be able to calculate throttle losses over a full range of rpm, however. See the graphs in the paper.

The 10% in the equation is a curve fitting parameter. What it suggests is that with the throttle fully closed, it is theoretically possible to achieve a manifold vacuum of 90% of atmospheric, or 26.5" in round numbers. To test that for reasonableness, consider a decal at high engine speed (over-run), with the throttle fully closed. I think that 26" or 27" would be pretty close. To calculate the actual manifold vacuum at any specific throttle position using the model, you would need a figure for the throttle open friction, ie the slope of the line on the graph, and it won't be zero.

Hope that helps.
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Old 07-07-2018, 06:55 PM   #96
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This is great info. Hubby uses the truck as his everyday, so price and that helped us make our decision. Locally, we have gentle hills and small mountains that show us what the 250 can do on those and we will head into West Virginia in August and that will give a little more info. We most certainly do a full on out west trip and that will be coast to coast within the next year and a half.
With a year under your belt with the F-250 6.2 gasser is there anything you can add to this discussion? Are you satisfied with your choice or would you do something different?

Nothing like experience!

Thanks!
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Old 07-08-2018, 07:28 AM   #97
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With a year under your belt with the F-250 6.2 gasser is there anything you can add to this discussion? Are you satisfied with your choice or would you do something different?

Nothing like experience!

Thanks!
Hi

We've been running our gasser for a bit over a year. The hills here in the east (10% grades) have not been an issue in any way for it. That's with a bit over 10,000 pounds of "stuff" (trailer + people + dogs + junk ) being hauled.

I have no idea how fast it'll pull up a steep grade. Anything over 70 MPH I'll let others do the research on ....

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Old 07-08-2018, 07:42 AM   #98
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All I can add to this conversation is my new F250 diesel is awesome for both towing and non-towing duty. The new F250’s drive so much better than even a few model years past. Turning radius/ parking is more of a challenge than my previous SWB Expedition.
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Old 07-08-2018, 09:10 AM   #99
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My F350 2016 Diesel 4x4 tows the 25 foot International on the open highway better than my 2014 Tundra 5.7L 4x4. No comparison in power and ease in accelerating or slowing down in the Rocky Mountains, higher elevations and steeper grades of ascent and descent.

The excess cargo capability works out very well for my style of Off the Grid Boondocking and requiring some extra weight in equipment.

Off the paved roads the 3/4 and 1 ton have a stiffer ride, but at 5mph to 40mph, not unexpected. No tow vehicle is better nor worse on washboard. An empty F350 without a trailer in tow is helpless in heavier washboard than a lighter truck.

Other Threads bring up that the Airstream trailer and heavier suspension truck will cause rivets to pop on the interior. I had this with the Tundra 4x4's. The popped rivets occur on the curved sections of the interior. This is a debate that may never be resolved.

At this point in time, the F350 Diesel 4x4 excels in towing ability. Excels in braking down steep grades. Has plenty of traction with 4x4 on gravel steep grades up or down hill.

The heavier tow vehicle may not be needed for those who do not spend a lot of time in the Rocky Mountains. Diesel or Gasoline. It is then more of a WEIGHT capacity that would be the deciding point for towing capacity. I am 100% satisfied with my Ford's ability. Overkill, but better than the lesser option of under.

Take your current tow vehicle and trailer up and down Monarch Pass in South Central Colorado. Then you have encountered the toughest example of what any tow vehicle is capable. If you are content... keep doing what your are doing. You have found the right tow vehicle to trailer combination.
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Old 07-08-2018, 11:41 AM   #100
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My F350 2016 Diesel 4x4 tows the 25 foot International on the open highway better than my 2014 Tundra 5.7L 4x4. No comparison in power and ease in accelerating or slowing down in the Rocky Mountains, higher elevations and steeper grades of ascent and descent.

The excess cargo capability works out very well for my style of Off the Grid Boondocking and requiring some extra weight in equipment.

Off the paved roads the 3/4 and 1 ton have a stiffer ride, but at 5mph to 40mph, not unexpected. No tow vehicle is better nor worse on washboard. An empty F350 without a trailer in tow is helpless in heavier washboard than a lighter truck.

Other Threads bring up that the Airstream trailer and heavier suspension truck will cause rivets to pop on the interior. I had this with the Tundra 4x4's. The popped rivets occur on the curved sections of the interior. This is a debate that may never be resolved.

At this point in time, the F350 Diesel 4x4 excels in towing ability. Excels in braking down steep grades. Has plenty of traction with 4x4 on gravel steep grades up or down hill.

The heavier tow vehicle may not be needed for those who do not spend a lot of time in the Rocky Mountains. Diesel or Gasoline. It is then more of a WEIGHT capacity that would be the deciding point for towing capacity. I am 100% satisfied with my Ford's ability. Overkill, but better than the lesser option of under.

Take your current tow vehicle and trailer up and down Monarch Pass in South Central Colorado. Then you have encountered the toughest example of what any tow vehicle is capable. If you are content... keep doing what your are doing. You have found the right tow vehicle to trailer combination.
Ray- I agree with your assessment for sure...my F250 6.7D is light years ahead of my F150EB while towing up/down grades like Monarch Pass...we made that trip with my 25' and my F150EB...power going up was not an issue, but going down surely gets your attention....my F250 was night and day difference...set the cruise, the engine brake on auto, and safe distance monitor and sit back, relax...not to mention the cargo capacity...we love it with our 28'.
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