Gas vs PSD
Elder User
Joined: May 2010
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From: WV
My post in summary was: An engine with no torque will need massive gearing and/or tranny to make it move a heavy load and this become problematic at high speeds because of that gearing.
We see this all the time. At 70 RPM my V10 is at 2500 rpm with a 4.30 while a newer 6.4 maybe only at 1800 with it's 3.55 rear end. Now if you take a torqueless engine like the rotary, you'll have to run some stupid rear end to be able to move the truck + a 15-20k lb load. Lets just say that since it has about 1/4 the torque of the V10, it would need 4 times bigger rear end, that means we'll be running 13.2 rear end to put the same amount of torque to the tires to get everything moving as my V10 would have (same trannies).
that's fine and all, but what about at 70 mph? While my V10 is at 2500 or so, the rotary will be at 4 times that, or 10,000 RPMs. Same thing when you compare the V10 to the PSD, the more aggressive gears in the gasser that help it get the starting power, are a disadvantage by keeping the RPM's high at highway speeds. I just metnioned the 7.3 PSD because they were similar in hp.
The major difference is that the V10 is practical and usable while the rotary engine is not.
We see this all the time. At 70 RPM my V10 is at 2500 rpm with a 4.30 while a newer 6.4 maybe only at 1800 with it's 3.55 rear end. Now if you take a torqueless engine like the rotary, you'll have to run some stupid rear end to be able to move the truck + a 15-20k lb load. Lets just say that since it has about 1/4 the torque of the V10, it would need 4 times bigger rear end, that means we'll be running 13.2 rear end to put the same amount of torque to the tires to get everything moving as my V10 would have (same trannies).
that's fine and all, but what about at 70 mph? While my V10 is at 2500 or so, the rotary will be at 4 times that, or 10,000 RPMs. Same thing when you compare the V10 to the PSD, the more aggressive gears in the gasser that help it get the starting power, are a disadvantage by keeping the RPM's high at highway speeds. I just metnioned the 7.3 PSD because they were similar in hp.
The major difference is that the V10 is practical and usable while the rotary engine is not.
The 7.3 PSD and rotoray engine both having 250 hp can technically put down the same force to the ground (rather it be tractile force or rear wheel torque), but they can not do the same job. One can do it with reasonable gearing that allows to start pulling the load and pull it at highway speeds. The other engine can pull the load, but the gearing becomes so steep it can not pull the load at highway speeds.
So if the job is to get a load going and pull it down the highway at highway speed (i.e. at least 70 mph), there is a problem with the rotary engine. Why? because it makes it's power at to high of RPM's and requires massive gearing where as the diesel can make it's power at lower RPM's. See the resemblance to the V10 and PSD now? The V10 also makes it's power at higher RPM's than the PSD. Yes, the V10 makes quite a bit of power at low RPM's compared to other gas engines, but not compared to what a diesel engine can do (go back to my other stupid long posts for the chemical reasons why).
Elder User
Joined: May 2010
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From: WV
The reason it is not technically interchangeable is because you are using pound/feet as your unit. There are only 2 ways, that I am aware of, where pound feet can be used at the rear. One is if you are referring to "axle torque". The other is if the truck has 24" tires, thereby rear wheel torque (in pound/feet) and tractive force would be the same number, disregarding the coefficient of traction of course.
I know what you're saying though. It's basically semantics and you'd need a heavy duty pocket protector and taped together black birth control glasses to really care either way. For the record, I don't care either way I was just wondering how long it would take for tractive force to be mentioned.
I know what you're saying though. It's basically semantics and you'd need a heavy duty pocket protector and taped together black birth control glasses to really care either way. For the record, I don't care either way I was just wondering how long it would take for tractive force to be mentioned.
Elder User
Joined: May 2010
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From: WV
There are CVTs that can take that kind of abuse, but you don't see them in the automotive environment because they usually take up a lot of space are are far too noisy
There are plenty of hydrostatic transmissions that are upto the task though. Hydrostatics have a near limitless "low gear" range. You could be bouncing off the rev limiter at 5500RPM and still be crawling at a quarter mile per hour.
There are plenty of hydrostatic transmissions that are upto the task though. Hydrostatics have a near limitless "low gear" range. You could be bouncing off the rev limiter at 5500RPM and still be crawling at a quarter mile per hour.
Interesting, I don't really follow transmission stuff outside of the auto industry, so I have no idea. I know my lawn mower has a hydrostatic
Postmaster
Joined: Apr 2008
Posts: 4,724
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From: Rogersville, TN
What kind of trannys? What year was the 5.4? Cab sizes? F-150, 250?
The reason why I am asking about the tranny is that, like mentioned before, 97% of SD's are automatics. So chances are people who are comparing the different engines are comparing both of them with automatics. "IF" your 5.4 was an auto and a 2v(like mine, and comparable year to the 7.3) and "IF" your 7.3 is an auto, to save everyone the math, at 2k rpm the tractive force of your 5.4 would have been 3,482 and the tractive force of your 7.3 at 2k rpm would be 5,305. They wouldn't even be close when it comes to getting a load moving. Chances are, with a big enough load and hill, your 5.4 would never see peak hp rpm.
By comparison, my manual is putting 7,415 to the ground in 1st at 2k rpm and 7,112 by 4,500 rpm. Compare that to a 6.4 with a 3.55 and ts. At 2k rpm the 6.4 is putting 7,196 to the ground and at 3k rpm it is putting 6,758 to the ground. So in a race from a dead stop to 4,500 rpm in mine I have no doubt it would be ahead of the 6.4. Shifting to 2nd, 3rd and so on the 6.4 would run off and leave me in the dust, but I am just talking about getting the load moving(0 to ~25 mph).
The reason why I am asking about the tranny is that, like mentioned before, 97% of SD's are automatics. So chances are people who are comparing the different engines are comparing both of them with automatics. "IF" your 5.4 was an auto and a 2v(like mine, and comparable year to the 7.3) and "IF" your 7.3 is an auto, to save everyone the math, at 2k rpm the tractive force of your 5.4 would have been 3,482 and the tractive force of your 7.3 at 2k rpm would be 5,305. They wouldn't even be close when it comes to getting a load moving. Chances are, with a big enough load and hill, your 5.4 would never see peak hp rpm.
By comparison, my manual is putting 7,415 to the ground in 1st at 2k rpm and 7,112 by 4,500 rpm. Compare that to a 6.4 with a 3.55 and ts. At 2k rpm the 6.4 is putting 7,196 to the ground and at 3k rpm it is putting 6,758 to the ground. So in a race from a dead stop to 4,500 rpm in mine I have no doubt it would be ahead of the 6.4. Shifting to 2nd, 3rd and so on the 6.4 would run off and leave me in the dust, but I am just talking about getting the load moving(0 to ~25 mph).
Postmaster
Joined: Apr 2006
Posts: 3,524
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From: CA Bay Area
Ever hear of the Bugatti Veyron? They ran that engine full out for days before releasing it. Not to mention it has 10 radiators.
The VW Pheaton was also designed to run at 90% maximum power with an ambient outdoor temperature of 130F while maintaining an interior temp of 72F for a minimum of 4 hours.
It's all about cooling, an engine can run at 100% output forever if you provide the proper amount of cooling.
As for the V10, I'm not sure because I don't live there, but I bet that radiator which is as big as a 3rd world house can handle some heat.
The VW Pheaton was also designed to run at 90% maximum power with an ambient outdoor temperature of 130F while maintaining an interior temp of 72F for a minimum of 4 hours.
It's all about cooling, an engine can run at 100% output forever if you provide the proper amount of cooling.
As for the V10, I'm not sure because I don't live there, but I bet that radiator which is as big as a 3rd world house can handle some heat.Running at redline the tank of fuel in the car last for about 1/2 hr
Wouldn't that be 40 minutes shorter than in Bill's van?
Sad part is, that technicality any gasoline engine is way more of the heater than an engine. Only about 1/3 of gasoline is converted into HP. And that is for the most efficient engines, what V10 is not
Now show me a pickup with 10 radiators?
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Modular motor junkie
Joined: May 2009
Posts: 6,190
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From: Texas
I have put 6k over the back axle, but lets not try it on the bumper.
I drove the set on the picture above on Nevada desert keeping the engine close to redline for about 20 minutes when I was climbing the big mountain at 90F outside.
Not only the engine didn't overheat, but I was using AC at part of the time.
If there is a gas engine that can match that performance, I would like to see it.
Not only the engine didn't overheat, but I was using AC at part of the time.
If there is a gas engine that can match that performance, I would like to see it.
I know what a PSD can do. There is one on Youtube pulling an 80' mobile home. My V10 could do that too though.
Senior User
Joined: Nov 2009
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Why doesn't some one just get together all the engines of the same years and hook up identical trailer up a hill and see who wins.
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Posting Guru
Joined: Oct 2009
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From: Rogue River, Oregon
Already been done, and not surprisingly, the diesel did it the best. There is truly no denying that when it comes to heavy towing, turbo diesels are great at towing. But some people contend (I'm one of them) that the extra initial cost, coupled with higher maintenance costs and greater repair costs aren't enough to justify owning one. I am well aware of the fact they tow better, get better mileage and so on, but it only takes one $10,000 repair bill to wipe that out. I also am fully aware that most diesel trucks are trouble free, and even more so when they are maintained well. But a quick look through any of the diesel-specific threads on this forum will prove my point that IF a diesel breaks, it sure as heck ain't free to fix!
Postmaster
Joined: Apr 2008
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From: Rogersville, TN
I got my 5.4 on a much shorter and a little steeper hill with ~the same weight trailer and was 8-10 mph faster than the v10 and 7.3 when I ran out of road. With an automatic I probably would have been 8-10 mph slower than them though.
What I would like to see is a stock 3v v10 with a manual and 4.10 gear against a stock 6.0 or 6.4 with an automatic.
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Modular motor junkie
Joined: May 2009
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From: Texas
It has never been done with an 05+ V10! They used a 00-04 V10 vs a 6.4.
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From: Isanti, MN
Turbocharged engines need time to build boost, and every time you shift you'd have to build boost all over again. The auto can shift with power being applied so there's no lost boost.
Secondly, the torque converter makes launching that much weight on a grade a stupidly simple affair. Mash the go pedal, release the stop pedal, and away we go. No burnt up clutches, no stalled engines, just seamless power.
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Modular motor junkie
Joined: May 2009
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From: Texas
I would go further than that and say I'd like to see a 6.0L/6.4L auto and manual run in a similar test as to what we did in Millersburg. I'm pretty confident the 5R110 would put a hurtin' on the ZF6 on a very steep grade for two reasons.
Turbocharged engines need time to build boost, and every time you shift you'd have to build boost all over again. The auto can shift with power being applied so there's no lost boost.
Secondly, the torque converter makes launching that much weight on a grade a stupidly simple affair. Mash the go pedal, release the stop pedal, and away we go. No burnt up clutches, no stalled engines, just seamless power.
Turbocharged engines need time to build boost, and every time you shift you'd have to build boost all over again. The auto can shift with power being applied so there's no lost boost.
Secondly, the torque converter makes launching that much weight on a grade a stupidly simple affair. Mash the go pedal, release the stop pedal, and away we go. No burnt up clutches, no stalled engines, just seamless power.
If done right power shifting will keep you from losing boost.
Its harder to do, but done right you can launch a ZF5/6 much faster than a TS.
Should only burn the clutch if its done wrong.