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Old 02-24-2014, 02:34 PM   #99
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Originally Posted by rostam View Post
Times have changed. We are not in the 70's anymore and almost no one uses a sedan as TV. Car companies know this and have softened up the sedans to reduce the cost and increase the profit; they have no incentive to make "beefed up" TV sedans either, as the profit margin on trucks in already great. In my opinion, after market modifications cannot make sedans a viable tow vehicle either. No matter how good Andy is I cannot see how a modified sedan, rated to tow 1000#, can safely 6000#. Most people do a risk vs reward analysis and decide that using a modified sedan (designed to move passengers, with little margin put in by manufacturer) is not worth it as a TV. Customers want peace of mind not possible liability.
This is a theoretical argument. The fact is these cars ARE towing big trailers. Doesn't matter what one theorizes is not "beefy," or what tests one theorizes aren't done. There is a fact on the table: These cars DO tow big Airstream trailers. And, there are many of them. And they are not breaking axles and plowing into people. Hard to ignore the facts.
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Old 02-24-2014, 02:45 PM   #100
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"many of them" and "facts" arent stats.

In order to settle this (and we won't because real data does not exist) one would need a collection of statistically significant samples carline by carline, with comparable groupings of towing mileages, of each carline. There would have to be equal groupings of those vehicles who exclusively tow within mfr limits and those who exceed mfr limits...by equally graduated amounts. I know of nowhere in the industry where this kind of data has been collected.

Anything less than that kind of empirical data is nothing more than cannon fodder. However, some of us live in that world (both inside knowledge of engineering and marketing practices and customer interface) and have experiences over decades which can offer educated opinions. But even that has no statistical absolute validity.
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Old 02-24-2014, 02:51 PM   #101
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I don't understand what you are referring to here. Are you saying your minivan engine makes more HP than your truck engine? Why refer to first gear?

Torque multiplies as a result of gearing. If you put 100 pounds feet torque into a transmission gear with a 10 to one reduction you now have 1000 pounds feet of torque. Now put that into your differential and multiply by that ratio. That engine torque becomes a big number....That is why different gear ratios make otherwise like vehicles feel so different. HP is HP, gear ratios have no impact on that, this has always been my understanding anyway...

Torque developed by an engine is just a small part of the equation. Torque curve and gearing play a very large part in the picture.

Just curious....
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Looking at his signature, he's got a 2000 Dodge 1500, so it's not difficult at all to imagine that a new minivan would have more horsepower and similar torque compared to the 318 (230 hp, 300 lb-ft) or 360 (245 hp, 335 lb-ft) available at the time.

A modern engine's torque curve can be MUCH flatter with better computer controls and especially with direct injection. Add forced-induction to that and the results are amazing, as we see in the Ecoboost engines from Ford. Huge amounts of torque available below 2,000 RPM, and a fat, flat torque curve way up into high RPM levels.

While the direct effect of reduction gears multiplies torque, the right choice of gearing also puts the engine in a "good" rpm range at the desired road speed. There are lots of trade-offs in what that "good" range might be (fuel consumption, power production, NVH, longevity, etc.)

PS: Yes I realize there aren't any Ecoboost minivans, I was just geeking about about modern engines.
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Old 02-24-2014, 02:52 PM   #102
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Times have changed. We are not in the 70's anymore and almost no one uses a sedan as TV. Car companies know this and have softened up the sedans to reduce the cost and increase the profit;
Apparently a common misconception that modern sedans have been "softened up"....

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Old 02-24-2014, 03:04 PM   #103
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IMO, no.
IMO No too. Looking at truck specs, if you add $$$$ options the tow rating goes down. Add diesel, 4x4, big wheels with low profile tires etc and the rating starts to dwindle. Often the big tow rating used for an advert is reg cab, 2x4, gas, 17" cheapie rims and no luxuries.
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Old 02-24-2014, 03:06 PM   #104
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Apparently a misconception that modern sedans have been "softened up"....

Crash Test 1959 Chevrolet Bel Air VS. 2009 Chevrolet Malibu (Frontal Offset) IIHS 50th Anniversary - YouTube
Wow!
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Old 02-24-2014, 03:13 PM   #105
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I don't understand what you are referring to here. Are you saying your minivan engine makes more HP than your truck engine? Why refer to first gear?
That's the highest gear, in which you will get the most actual thrust at the drive wheels. engine torque x 1gear ratio x final drive (rear end) ratio /wheel diameter = thrust at the wheels.
My truck, in 1st gear, will produce 2000lbs. (weighs ~5300lbs, give or take)
the "mini" will produce 3000. (and weighs 4500).

truck engine--318v8, designed in the 1960s, 220hp, and a horrible torque curve--300ftlbs at its peak of >4000rpm; much much less at rpm's that you can actually use

Mini-3.6L: 283hp, 260ftlbs torque, and its a much wider torque band.

The mini is more truck-ish than my truck. Or...the truck is very pokey. (But nobody thinks I'm a nut-bar when I pull into the campground with it. )

Here's another fun fact: the new Durango with the Hemi motor (giant gobs of both hp and torque) only produces about 3200lbs of thrust in 1st gear, because of the lower gearing. But it weighs in at about the same as my truck, so...
With all of its HP, it probably won't shift as much on highway grades, but my point is just that thinks aren't always as they seem at first glance.
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Old 02-24-2014, 03:18 PM   #106
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All of this discussion of cars compared to trucks for towing, and safety, yet no mention of the fact that passenger vehicles are designed, built, and tested to meet passenger vehicle safety standards that many trucks are exempt from due to their GVW. In other words, the starting point is safer.

I see debate about whether a hitch can be safely added to a passenger vehicle, but has anybody considered what it would take to re-engineer a pickup truck for passenger car levels of crash safety, performance in roll over tests, etc? It would be far easier to get the passenger car to tow than it would be to make the pickup truck equally safe in a crash, IMO.

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Old 02-24-2014, 03:38 PM   #107
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All of this discussion of cars compared to trucks for towing, and safety, yet no mention of the fact that passenger vehicles are designed, built, and tested to meet passenger vehicle safety standards that many trucks are exempt from due to their GVW. In other words, the starting point is safer.

I see debate about whether a hitch can be safely added to a passenger vehicle, but has anybody considered what it would take to re-engineer a pickup truck for passenger car levels of crash safety, performance in roll over tests, etc? It would be far easier to get the passenger car to tow than it would be to make the pickup truck equally safe in a crash, IMO.

Jeff
NHTSA test and rates through 3500/350 (One ton) series. Not every year, every model as trucks don't change much during their lifecycle. Go to their website, you don't have to guess. Some trucks perform better than some cars in some categories. Cars generally do better than trucks in some categories. And some cars are better than other cars in some categories.
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Old 02-24-2014, 03:59 PM   #108
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Originally Posted by jcl View Post
All of this discussion of cars compared to trucks for towing, and safety, yet no mention of the fact that passenger vehicles are designed, built, and tested to meet passenger vehicle safety standards that many trucks are exempt from due to their GVW. In other words, the starting point is safer.

I see debate about whether a hitch can be safely added to a passenger vehicle, but has anybody considered what it would take to re-engineer a pickup truck for passenger car levels of crash safety, performance in roll over tests, etc? It would be far easier to get the passenger car to tow than it would be to make the pickup truck equally safe in a crash, IMO.

Jeff
I believe older pick up trucks were terrible in terms of being safe in an accident, newer trucks are being engineered with all the safety improvements available. Safety sells these days.

You do bring up something I have always wondered about though. What is the impact of the chassis stiffening done to enable a modern car tolerate the loads of towing a large trailer? Do these modifications impact the factory designed crumple zones or safety features?
Curious....
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Old 02-24-2014, 04:57 PM   #109
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I'd agree that older trucks were very poor for safety performance, and that newer ones are better.

I would expect intuitively that a rear crumple zone on a passenger car would be impacted slightly by a receiver. One vehicle that I installed a factory hitch involved stiffening to the rear unibody to support the receiver, and removal of the collapsible bumper supports. The bumper was stiffened, apart from the receiver, presumably so that it could still meet the bumper impact damage rules without the shocks. All of this was using factory OE parts, installed after delivery.

I wonder what comprises the rear crumple zone of a pickup truck? And how is it impacted by installing a heavy duty receiver?

This is all after the fact, though. I think the most important safety features are active ones, that allow one to avoid an accident in the first place.

Jeff
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Old 02-24-2014, 05:06 PM   #110
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Most of the OE receivers are now actually THE rear cross member of the frame and designed that way. That's just in the last few years' new introductions. BUT, for GM, if it is offered as OE it is engineered and crash tested with the receiver installed.
However, with a PU there is 5 to 8 feet of "crumple zone" from bumper to occupants. It's really not defined as such, but offers a lot of distance from the intruder, so to speak.
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Old 02-24-2014, 05:37 PM   #111
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However, with a PU there is 5 to 8 feet of "crumple zone" from bumper to occupants. It's really not defined as such, but offers a lot of distance from the intruder, so to speak.
Assuming that that 5 to 8 foot box is empty...
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Old 02-24-2014, 05:42 PM   #112
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Assuming that that 5 to 8 foot box is empty...
true dat! Customers are responsible for their loads and their safety, just like what they tow.

Of course, the same concern is there for whatever you load in any vehicle rear compartment/space.
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