Gas vs PSD
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
the main reason the 6.8 isnt the most impressive gasser released by ford, is because of its low compression. they werent makin a high performance motor, rather somethin that would run on 87 and have the the torque at a low enough rpm that it could be used in a truck. its still around cuz of the horrible reputation of the 7.3's successors. if it were 10.5-11:1, or had a supercharger, it would be much more impressive (although i still wouldnt be impressed).
And as for "still around" - there will ALWAYS be a gas-powered version of a light-duty truck unless something earth-shattering happens. The new 6.2L gasser is quite the machine too
Lead Driver
Joined: May 2011
Posts: 5,800
Likes: 455
Actually, virtually all production modulars, the 4.6, the 5.4 AND the 6.8 are "low compression" running around 9:1 or slightly higher, and 9.8:1 in the VCT versions. The reason is, yes, they run 87 octane. What would you expect an automotive company to produce as a work horse? At 11:1 they'd need 93 octane (been there, done that).
exactly my point. . . .all motors in all trucks from the factory come with low comp. . . .theyre not "high performance" oriented.
And as for "still around" - there will ALWAYS be a gas-powered version of a light-duty truck unless something earth-shattering happens. The new 6.2L gasser is quite the machine too
yea, but ford is the only one continuing their huge displacement gassers in their 3/4 and 1 ton applications. and theyre the only ones who have had severe problems with their diesels after the 7.3 (gotta have an option for the die hard ford guys that are scared of the 6.0 and 6.4, for good reason). we will see in the next couple years whether they continue the 6.8. its due for a "revision". . .so my point wasnt about why gassers are still around, it was about why the 6.8 is still around
exactly my point. . . .all motors in all trucks from the factory come with low comp. . . .theyre not "high performance" oriented.
And as for "still around" - there will ALWAYS be a gas-powered version of a light-duty truck unless something earth-shattering happens. The new 6.2L gasser is quite the machine too
yea, but ford is the only one continuing their huge displacement gassers in their 3/4 and 1 ton applications. and theyre the only ones who have had severe problems with their diesels after the 7.3 (gotta have an option for the die hard ford guys that are scared of the 6.0 and 6.4, for good reason). we will see in the next couple years whether they continue the 6.8. its due for a "revision". . .so my point wasnt about why gassers are still around, it was about why the 6.8 is still around
Cargo Master
Joined: Jan 2005
Posts: 2,413
Likes: 11
I wasn't saying the 6.8 wasn't the most impressive engine put out by ford I was saying inch for inch it wasn't the most impressive of the modulars. I went a step further and even said because ford didn't do anything with them. I don't know what your getting at about 5252 rpms. I know that's where tq and hp cross but what's that got to do with Ford bolting 4v heads and a roots supercharger on a 5.4 and making 500 ftlbs of tq. 5252 is below the redline already. I admit I don't know what the rpm range is on that gt. I would like to think its higher and they use the supercharger to keep it from getting winded.
I reckon you can say rpm to rpm diesels make the best power. Then you get in the noise bleed section and the gaser really starts makeing it power.
I reckon you can say rpm to rpm diesels make the best power. Then you get in the noise bleed section and the gaser really starts makeing it power.
Cargo Master
Joined: Jan 2005
Posts: 2,413
Likes: 11
My speedo only goes to 100 mph. Wed of the tornados I pegged 100 mph for 45. Never came off it. I "think" I was pulling 2600-2700 rpm. Might be less. If my truck will stay in 5th @ 3k rpm I would say it'll do it for a while. I was pulling 900 deg egts. I hit 1000 on the little hills. Tranny ran slightly below 160.
I don't know what the top speed of a v10 is and if 3k rpms is in side of that.
Why do you think a psd will have a problem holding 3k rpms?
Fleet Mechanic
Joined: Feb 2007
Posts: 1,852
Likes: 39
Even if kerosene heaters didn't emit CO, they still deplete oxygen, and in a closed space, that means death, eventually.
Regarding diesels vs. gassers, all that matters to the truck and the load it is pulling is rear-wheel torque. Two trucks of the same weight pulling the same load up the same hill at the same speed are generating the exact same rear-wheel torque. By virtue of the fact that they are going the same speed, they are also generating the exact same horsepower. And the load doesn't care whether that power came from gasoline or diesel.
Engine torque numbers are mostly marketing hype, which apparently many people here have bought into. A high torque number just means that the engine makes its HP at lower RPMs. That is the great thing about diesels, they're turning slower to do the same work. Less fuel, less noise, less wear, etc.
I really like that about my 7.3, which is why it is my primary tow vehicle. But at 250 HP, it is anemic. My 330 HP 400 ft. lb. small-block GM will tow circles around it, but I hate using it because I don't like listening to that engine all wound up and burning all of that gas.
Now let's see, where did I put that Nomex suit?...
Regarding diesels vs. gassers, all that matters to the truck and the load it is pulling is rear-wheel torque. Two trucks of the same weight pulling the same load up the same hill at the same speed are generating the exact same rear-wheel torque. By virtue of the fact that they are going the same speed, they are also generating the exact same horsepower. And the load doesn't care whether that power came from gasoline or diesel.
Engine torque numbers are mostly marketing hype, which apparently many people here have bought into. A high torque number just means that the engine makes its HP at lower RPMs. That is the great thing about diesels, they're turning slower to do the same work. Less fuel, less noise, less wear, etc.
I really like that about my 7.3, which is why it is my primary tow vehicle. But at 250 HP, it is anemic. My 330 HP 400 ft. lb. small-block GM will tow circles around it, but I hate using it because I don't like listening to that engine all wound up and burning all of that gas.
Now let's see, where did I put that Nomex suit?...
Cargo Master
Joined: Jan 2005
Posts: 2,413
Likes: 11
Even if kerosene heaters didn't emit CO, they still deplete oxygen, and in a closed space, that means death, eventually.
Regarding diesels vs. gassers, all that matters to the truck and the load it is pulling is rear-wheel torque. Two trucks of the same weight pulling the same load up the same hill at the same speed are generating the exact same rear-wheel torque. By virtue of the fact that they are going the same speed, they are also generating the exact same horsepower. And the load doesn't care whether that power came from gasoline or diesel.
Engine torque numbers are mostly marketing hype, which apparently many people here have bought into. A high torque number just means that the engine makes its HP at lower RPMs. That is the great thing about diesels, they're turning slower to do the same work. Less fuel, less noise, less wear, etc.
I really like that about my 7.3, which is why it is my primary tow vehicle. But at 250 HP, it is anemic. My 330 HP 400 ft. lb. small-block GM will tow circles around it, but I hate using it because I don't like listening to that engine all wound up and burning all of that gas.
Now let's see, where did I put that Nomex suit?...
Regarding diesels vs. gassers, all that matters to the truck and the load it is pulling is rear-wheel torque. Two trucks of the same weight pulling the same load up the same hill at the same speed are generating the exact same rear-wheel torque. By virtue of the fact that they are going the same speed, they are also generating the exact same horsepower. And the load doesn't care whether that power came from gasoline or diesel.
Engine torque numbers are mostly marketing hype, which apparently many people here have bought into. A high torque number just means that the engine makes its HP at lower RPMs. That is the great thing about diesels, they're turning slower to do the same work. Less fuel, less noise, less wear, etc.
I really like that about my 7.3, which is why it is my primary tow vehicle. But at 250 HP, it is anemic. My 330 HP 400 ft. lb. small-block GM will tow circles around it, but I hate using it because I don't like listening to that engine all wound up and burning all of that gas.
Now let's see, where did I put that Nomex suit?...
Please show me your math on the trucks doing the same speed haveing same hp and same tq. That makes no sense to me. If physical size and shape and weight is the same, everything being the same but the drive train you could have truck 1 doing 65 turning 2k rpms and truck 2 turning 1800 rpms @65 mph. Difference here 1 truck is geared around 3:73 the other 4:11. This isn't actually figures its off the top of my head but should be close. Look at that engines tq to rpm range. You clearly see the tq and hp isn't the same. Now gear em both the same get the rpms the same. There's still a difference in the out put tq and hp of both engines.
Tq and hp isn't a ploy to sell you on an engine it is actually numbers to show the work ability of the engine. That's like saying the watt rateing on a light bulb is meaningless.we all know that it does. Hp and watt just about the same thing.
Hotshot
Joined: Dec 2006
Posts: 14,069
Likes: 17
From: Melbourne, Ky
As for gearing in a diesel, the 97 in my signature has 4:56 gears with an E40D automatic tranny. Check out the miles on it. It had 116,000 5 years ago when I bought it.
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Hotshot
Joined: Dec 2006
Posts: 14,069
Likes: 17
From: Melbourne, Ky
As for those afraid of the 6.4, check out this thread.
https://www.ford-trucks.com/forums/9...g-the-dpf.html
https://www.ford-trucks.com/forums/9...g-the-dpf.html
Senior User
Joined: Sep 2004
Posts: 116
Likes: 0
Please show me your math on the trucks doing the same speed haveing same hp and same tq. That makes no sense to me. If physical size and shape and weight is the same, everything being the same but the drive train you could have truck 1 doing 65 turning 2k rpms and truck 2 turning 1800 rpms @65 mph. Difference here 1 truck is geared around 3:73 the other 4:11. This isn't actually figures its off the top of my head but should be close. Look at that engines tq to rpm range. You clearly see the tq and hp isn't the same. Now gear em both the same get the rpms the same. There's still a difference in the out put tq and hp of both engines.
Tq and hp isn't a ploy to sell you on an engine it is actually numbers to show the work ability of the engine. That's like saying the watt rateing on a light bulb is meaningless.we all know that it does. Hp and watt just about the same thing.
Tq and hp isn't a ploy to sell you on an engine it is actually numbers to show the work ability of the engine. That's like saying the watt rateing on a light bulb is meaningless.we all know that it does. Hp and watt just about the same thing.
Senior User
Joined: Sep 2004
Posts: 116
Likes: 0
And, IMO, medium-duty, too. I, and my coworkers, have noticed an increase in customers picking gas powered trucks (mostly class 4/5) in the last year or so. While certain types of companies have long chosen gas, we've noticed more of the those that have typically been diesel only opting for gas.
Cargo Master
Joined: Jan 2005
Posts: 2,413
Likes: 11
If they are both under the same load (same weight, same drag, same incline), and maintaining the same speed (neither accelerating or decelerating), then the hp/torque to the ground has to be the same from both. If it wasn't, then one truck would have to be changing speed. However, that doesn't mean that both or either are making max power. Unless it is a very heavy load and/or very steep hill, both are likely at part throttle.
Of tq to the tranny 500x.73= 365 put to the rearend. The v10 only makes 457 @ 3400? So what's fair to guess at 2100? 80%? Aight ill buy that. 457x.80=365.6 so 366x.73=267 sent to the rearend. Now if boyh trucks where geared the same then well there's your answer. There not so therrs another step. Maybe ill figure it out later or you'll show your math and it'll turn out I'm full of crap.
The advantage of high end tq is to take advantage of gearing.
Senior User
Joined: Sep 2004
Posts: 116
Likes: 0
That's makes no sense to me. I'm going to leave rearend out cause simpley I can't figure that out in my head. I can't remember right off but I think 5th gear on the torqshift tranny is .73 we'll use the 3v v10 and my 04 6.0l. Me and kevin going down the highway cruise set on 65. My tach is on 2k his is like 2100. I have 4.11s and he has 4:30s. The 6.0 is putting out 560 ftlb of tq @ 2200 so I'll just say imnputting out 500 ftlbs
Of tq to the tranny 500x.73= 365 put to the rearend. The v10 only makes 457 @ 3400? So what's fair to guess at 2100? 80%? Aight ill buy that. 457x.80=365.6 so 366x.73=267 sent to the rearend. Now if boyh trucks where geared the same then well there's your answer. There not so therrs another step. Maybe ill figure it out later or you'll show your math and it'll turn out I'm full of crap.
The advantage of high end tq is to take advantage of gearing.
Of tq to the tranny 500x.73= 365 put to the rearend. The v10 only makes 457 @ 3400? So what's fair to guess at 2100? 80%? Aight ill buy that. 457x.80=365.6 so 366x.73=267 sent to the rearend. Now if boyh trucks where geared the same then well there's your answer. There not so therrs another step. Maybe ill figure it out later or you'll show your math and it'll turn out I'm full of crap.
The advantage of high end tq is to take advantage of gearing.
If the trucks are identical with respect to truck/trailer weight and size, and are going the same speed on the same terrain, the the forces opposing each trucks motion have to be the same. If your engine was putting out more force than his, then one of you would be making more or less than enough power to equal the load you see. Either you would be speeding up, or he would be slowing down.
Postmaster
Joined: Oct 2006
Posts: 4,171
Likes: 12
From: SE Texas
The numbers you list are peak numbers. That's what the engines would make at that rpm at wide open throttle. Neither would be at WOT, though, so neither would be the maximum torque they could at that rpm. Instead, both are making some percentage--different for each engine--of the torque they are capable of.
If the trucks are identical with respect to truck/trailer weight and size, and are going the same speed on the same terrain, the the forces opposing each trucks motion have to be the same. If your engine was putting out more force than his, then one of you would be making more or less than enough power to equal the load you see. Either you would be speeding up, or he would be slowing down.
If the trucks are identical with respect to truck/trailer weight and size, and are going the same speed on the same terrain, the the forces opposing each trucks motion have to be the same. If your engine was putting out more force than his, then one of you would be making more or less than enough power to equal the load you see. Either you would be speeding up, or he would be slowing down.
JL
