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Old 12-17-2018, 12:43 PM   #421
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As far as friction is concerned are you trying to tell me that a diesel engine has more friction than a gas of the same size? I'm sorry but i'm laughing on that one. Engine internals are the same between the two designs. There is no meaningful added items on the diesel to explain parity in engine braking. You say that its the drive train, but if you compare the same truck one gas the other diesel they will both have engine braking which is similar with comparably sized motors and the EXACT same drive train. Your argument about the vacuum doesn't fly and neither does this.
Not at all. As I posted above, I don’t consider that a differentiator. I said that engine friction is different between the 1.9 litre VW engines and the larger pickup truck engines. With the lower friction of the smaller engines the difference in engine braking between the gas and the diesel was obvious. Not so much with the more significant friction of the larger engine where the differences may not be so apparent to the user. Butt dynos are notoriously inaccurate.

Don’t laugh, research.

In terms of diesel vs gas, although it wasn’t my point, consider that the compression ratios are significantly different. And that half of engine friction comes from the ring liner interface. You don’t think the rings are different?
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Old 12-17-2018, 12:57 PM   #422
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Yes, and I have a Lincoln MK VIII that provides little to no engine braking. My wife complains about it all the time. You have to take it out of OD to get any meaningful engine braking.
OD isn’t a spec, it is a concept. Let’s say two otherwise identical vehicles had different transmissions. One has a 0.9 overdrive while the other has a 0.75 overdrive. The latter vehicle would need to be shifted down to gain the same amount of engine braking.

And that would say nothing about the amount of engine braking available at the flywheel
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Old 12-17-2018, 02:08 PM   #423
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jcl, I applaud your efforts. You are a much more patient man than I. I was hopeful in being able to reason with a fellow engineer with facts and logical thoughts, and encourage their own discovery with the wealth of information out there. Yet I guess there are some that can dismiss interpret facts for a flat earth too?
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Old 12-17-2018, 02:13 PM   #424
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Yes, and I have a Lincoln MK VIII that provides little to no engine braking. My wife complains about it all the time. You have to take it out of OD to get any meaningful engine braking.
This proves nothing.

Some engines are specifically tuned (via the throttle body), to minimize engine braking in order to maximize gas efficiency in cruising gears. Yet certainly, these models also will close down the throttle body more aggressively when downshifted to maximize the engine braking function when necessary.

It is a behavior that can be tuned. Doesn't mean it doesn't exist.
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Old 12-17-2018, 03:01 PM   #425
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jcl, I applaud your efforts. You are a much more patient man than I. I was hopeful in being able to reason with a fellow engineer with facts and logical thoughts, and encourage their own discovery with the wealth of information out there. Yet I guess there are some that can dismiss interpret facts for a flat earth too?
Thanks. But unless he can confirm otherwise I don’t think Tuco is an engineer. I assumed he is an instrumentation technician. Not that there is anything wrong with that.
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Old 12-17-2018, 04:58 PM   #426
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Yet I guess there are some that can dismiss interpret facts for a flat earth too?
The earth is round?

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Old 12-17-2018, 05:53 PM   #427
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Thanks. But unless he can confirm otherwise I don’t think Tuco is an engineer. I assumed he is an instrumentation technician. Not that there is anything wrong with that.
https://en.wikipedia.org/wiki/Nuclear_Power_School MMN

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Old 12-17-2018, 05:57 PM   #428
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The earth is round?

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And Diesels rule! So I guess we are all happy!!
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Old 12-17-2018, 06:32 PM   #429
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Thanks. Donít know anything about nuclear power plants. Looks interesting. We refer to courses of up to two years at technical schools as producing technicians and technologists, and four year courses from degree granting institutions as producing (potential) engineers. There are requirements after graduation to work in a type of apprenticeship to achieve the professional designation, P.Eng. here. Requirements vary by jurisdiction.
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Old 12-17-2018, 07:39 PM   #430
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Thanks. Donít know anything about nuclear power plants. Looks interesting. We refer to courses of up to two years at technical schools as producing technicians and technologists, and four year courses from degree granting institutions as producing (potential) engineers. There are requirements after graduation to work in a type of apprenticeship to achieve the professional designation, P.Eng. here. Requirements vary by jurisdiction.
What is a P. Eng?
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Old 12-17-2018, 07:46 PM   #431
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What is a P. Eng?
A registered Professional Engineer. In my case, 5 years of university, then working under the supervision of a PEng for three years while demonstrating increased responsibility. For those years you are an EIT (engineer in training) In Canada it is a self regulated profession, like doctors and lawyers. The US version is a state licensed PE.
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Old 12-17-2018, 10:37 PM   #432
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A registered Professional Engineer. In my case, 5 years of university, then working under the supervision of a PEng for three years while demonstrating increased responsibility. For those years you are an EIT (engineer in training) In Canada it is a self regulated profession, like doctors and lawyers. The US version is a state licensed PE.
And your underlying engineering degree is in what?
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Old 12-17-2018, 11:18 PM   #433
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And your underlying engineering degree is in what?
BASc in Mech Eng
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Old 12-18-2018, 12:05 PM   #434
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BASc in Mech Eng
You're an ME working on his certification to work without supervision if I understand where you are at in your education. I don't understand why someone with that background would push the narrative that a piston acting on a vacuum actually does work. PTeck worships the ground you walk on and will parrot whatever you say and do. So at this point until he provides some background of his engineering skills I'll take what he says as coming from you. Now either you missed something in class or your pushing an agenda. Can you explain to me which it is, or am I missing something here?
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Old 12-18-2018, 12:18 PM   #435
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Please take the personal sniping about education, qualifications and the "I'm right you're ignorant" nonsense offline.
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Old 12-20-2018, 04:28 PM   #436
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And I understand that...no argument. My point to Ptek and others who "dis da diesels" is not meant to be an argument against their choice of Lexas or other TV's. I pose the question asking "have you ever driven a newer diesel pulling a larger AS??" I get all kinds of "yea, but's" which tells me likely not. The airbrakes are only one benefit I like with my 6.7l. As I cruise the steep grades at highway speeds 60-65mph while on cruise, the engine is loping along at 1500rpms getting 13.0-13.4 mpg; I have kayaks on top, generator in back with 2 BBQ grill's, charcoal and propane bottle, firewood, camp gear, and 1100lbs tongue weight...that's all I am using to compare...not sure Ptek has pulled his AS with a newer diesel like many of us do, to give a actual comparison of his opinion? I respect the daily driver need...I didn't buy my F250 for daily driver. I do love driving it on the highway; just don't like filling it, parking it, nor servicing it; it's expensive, but when I am on the road pulling the 28' in MT and Northern states...it is night and day more pleasurable over my F150 in many ways; and I loved my F150 for my 25's when I owned them.


Amen brother! Own a 31 ft Classic and no comparison between my former F250 gasser and my current F250 diesel- to each his own
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Old 12-20-2018, 06:15 PM   #437
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I drive a Dodge with a Cummins diesel that does not have an exhaust brake. (early 2007). I still have engine braking. From whatever sources, air resistance, rolling resistance, engine braking, transmission friction, it will hold its speed in OD without increasing on up to a 4% grade. Beyond that I need to add pedal braking and shift down. But if I need to stop at the middle or end of the grade I need the brakes. I remember testing the engine braking when I first pulled with the diesel and decided that it had about the same amount of engine resistance pulling the trailer as the 97 model 150 Ford with the little v8 gasser that it replaced,

Coasting with the diesel the intake and the exhaust valves still function. There is some slight vacuum on the intake side (but not much) and some flow resistance from the muffler and CC on the exhaust side. Overall they do provide some engine braking.
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Old 12-21-2018, 06:42 PM   #438
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Article in OVERLAND JOUNAL

Our latest Overland Journal just arrived. Great article "North American Overland" SUV in your driveway, by Chris Cordes. Starts on page 67. Page 72 caught my eye, Chris is towing his 27' AS w/2000 7.3 Excursion. His comment on the Excursion tells it all. Bottom left of page 72.



For those that may not know, this magazine is written by overland traveler's that travel the world to explore, driving in conditions not of our asphalt roads. Boon docking has a whole other meaning.



Merry X-mas and a happy new year to all of you.
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Old 12-27-2018, 07:01 AM   #439
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Amen brother! Own a 31 ft Classic and no comparison between my former F250 gasser and my current F250 diesel- to each his own
Still running drum brakes on the TT with the cheap Prodigy 3 equivalent controller?

That’s where the improvement should have been: trailer antilock discs. Lighter & more capable (stable) tow vehicle.

Not heavier TV without corresponding load. All that does is make total braking distance worse. In every condition. With or without the load. Cutting open road top speed even farther.

And you CANNOT use exhaust brake in the wet.

Exhaust brake adds nothing with these trailers. They’re tiny as to weight.

Too high a descent speed is the underlying problem.

How on earth did they ever descend these mountains in the 1960s and 1970s with trailers just as heavy? With 4,5,6 people in the car.

Wait while I consult memory.

Oh, yeah. Rig is at highest vulnerability to loss-of-control accident on a downslope. Descent speed has to account for WOT acceleration with trailer brakes absolutely closed.

What follows from that? The, “How to Do a Descent?” No matter how bad the TV choice as to inherent stability.

Gas versus Diesel doesn’t exist in the real world.

Almost without exception I get you dummies passing me and other big trucks on the upslope. Considering we have somewhat better “hitch rigging”, the downslope concern about the travel trailer pulling out to pass (as yours & mine will want to do) is a GIGANTIC concern. The biggest of the day. The week. The year.

Hitch rigging OTHER than taut is what you minimize. Practice. (How do you Exit the Interstate? Down to 50-mph BEFORE exit ramp and down to 35 immediately. Then just as quickly back up to 40-45. To enter the side road WITH TAUT HITCH RIGGING.

It is NOT about the brain-dead “control” of speed going downslope, it is SPACE out ahead, and proper procedure of service brake use. The whole way.

It’s still true that the ascent and descent are made at the same speed. Below 40-mph isn’t simply “fine”, it’s prudent (go look that up).

The heavier the TV, and the less-responsive the engine choice, the harder the job.

It’s brakes and gearing. Up & down. On or off the highway.

Pay strict attention to hitch rigging slack.

.
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Old 12-27-2018, 07:35 AM   #440
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And I understand that...no argument. My point to Ptek and others who "dis da diesels" is not meant to be an argument against their choice of Lexas or other TV's. I pose the question asking "have you ever driven a newer diesel pulling a larger AS??" I get all kinds of "yea, but's" which tells me likely not. The airbrakes are only one benefit I like with my 6.7l. As I cruise the steep grades at highway speeds 60-65mph while on cruise, the engine is loping along at 1500rpms getting 13.0-13.4 mpg; I have kayaks on top, generator in back with 2 BBQ grill's, charcoal and propane bottle, firewood, camp gear, and 1100lbs tongue weight...that's all I am using to compare...not sure Ptek has pulled his AS with a newer diesel like many of us do, to give a actual comparison of his opinion? I respect the daily driver need...I didn't buy my F250 for daily driver. I do love driving it on the highway; just don't like filling it, parking it, nor servicing it; it's expensive, but when I am on the road pulling the 28' in MT and Northern states...it is night and day more pleasurable over my F150 in many ways; and I loved my F150 for my 25's when I owned them.
And it’s a good thing you limit the rig to a high of 58-mph under perfect conditions, and do ascents & descents at 25-mph. Right?

The answer you likely intend will show that “too fast for conditions” was the underlying premise as to TV change. I’ve seen you try and make it before.

That 150 would have been better in THE test: emergency double lane change at set travel speed.

You’ve chosen the slower vehicle, so how far down did you ratchet the travel speed? (You didn’t, did you?).

It’s the physics involved. Roll Center Height.

Again, diesel seems nice, but it’s a penalty in every price category today; it worsens braking, and as it is worse for RCH, the combined rig is even less stable than before.

And all that junk you carry: it won’t move if the pickup lands on its side, right? Still on the bed floor? The subject is, “Load Securement”. I suggest you take it even more seriously.

..
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