Diesel vs Gasoline

[Charles R]

My heavy tow package 3.73 ratio 2019 Expedition with the 10spd runs between 1600-1900rpm on typical highway trips. 75mph its in the 1900ish range.

Yep! Better cruise rpm for diesels for sure!

My CRD has the Mercedes OM642 (Sprinter engine, no Bluetec/DEF) with a torque peak @ 1900rpms. Like yours, that's where the rpm should be at cruise. In the case of these Jeeps, using the Hemi's 545RFE transmission would have been a much better choice than the Mercedes 722.6/NAG1 transmission it has. Just doing that would have given it the gear ratios needed to cruise at a proper lower rpm level, since the only axle ratio available was a 3.73. One fun thing is that since I've increased the tire size, the cruise rpm has gotten closer to 'the ideal'! haha! I currently cruise about 2100rpm @ 65mph.

As I'm sure most know, you typically want to gear the vehicle to cruise near an rpm that compliments it's engine's torque peak rpm, for peak highway mileage. That torque peak is where an engine is running at it's most efficient point. These days, keeping the RPM close to it's torque peak at all times is also why we're seeing more gear speeds for engine/transmission packages in general. The OEM's are trying to keep the engine running as close to it's max efficiency point as possible, to bring the economy numbers up as much as possible.

 

[calicamper]

Its actually impressive how much grunt these modern gas engines have in the low RPM ranges. This is the 3.5L 2019 Ford Expedition Platinum which does have a different power rating than the lower trims.
My 06 4.7L V8 didn’t start to get good grunt till you were up into the 2500+ range. These modern engines are a totally different experience they loaf along and never feel like they are running hard. Where my 4.7 V8 there were many times you felt like it was being worked hard when you were hitting 3500+rpm which is pretty rare to see in this 3.5 combo.

 

[nickw]

View attachment 569318View attachment 569318View attachment 569319Its actually impressive how much grunt these modern gas engines have in the low RPM ranges. This is the 3.5L 2019 Ford Expedition Platinum which does have a different power rating than the lower trims.
My 06 4.7L V8 didn’t start to get good grunt till you were up into the 2500+ range. These modern engines are a totally different experience they loaf along and never feel like they are running hard. Where my 4.7 V8 there were many times you felt like it was being worked hard when you were hitting 3500+rpm which is pretty rare to see in this 3.5 combo.
View attachment 569318

Yup, better than many V8s and on par with smaller displacement diesels.

 

[billiebob]

The flipside is with the cab gone you are basically working on a bare engine which will make things easier.

Or...

 

[85_Ranger4x4]

Or...
View attachment 569547

I have kinda wondered myself if some of the Powerstrokes maintanence issues in the past is the people that designed and built the engines put them in trucks like this:

 

[BigSwede]

One problem with gas engines has been the hunt for horsepower (mostly for marketing purposes) has hurt the low-end torque. When Chevy switched from the good ol' tree-fitty (5.7L) to the 5.3L, hp went way up but it was actually a worse motor for towing as the torque wasn't any better, and worse the torque peak went from 1700 to over 3000 (going from memory).

 

[Buliwyf]

That's what 6 speeds are for. Lol.

The 6.2l Ford performs much like my 7.3 diesel did, if I avoid looking at the rpm guage.

 

[nickw]

One problem with gas engines has been the hunt for horsepower (mostly for marketing purposes) has hurt the low-end torque. When Chevy switched from the good ol' tree-fitty (5.7L) to the 5.3L, hp went way up but it was actually a worse motor for towing as the torque wasn't any better, and worse the torque peak went from 1700 to over 3000 (going from memory).

Torque peak is largely meaningless....an engine can have torque peak at 3,000 RPM but it can have adequate "torque" at much lower RPM, plenty to get the job done.....which is exactly why we look at HP or the HP curve to figure out an engines work capacity since gearing makes up the difference.

If your stuck on low end torque, this big block crate engine, the"High Torque" 502 V8, has max torque at 3200 RPM.....but it still has 490+ at 2400 RPM and I'm guessing well over 400 into the teens....

HT502 Big Block Crate Engine: 88890534 | Performance

With 512 lb-ft of torque, the HT502 big block crate engine is a powerful alternative to rebuilding - see images, dyno specs, installation info and more.

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I can't imagine any gas small block (or big block) V8 outside of specialized industrial applications that have max torque values at 1700 RPM. Generally any engines with max torque that low are very low revving, low HP engines. The older straight 6's come to mind, like Ford 4.9L, Chevy 292, Toyota 2F, etc and maybe some of the older V8 long stroke gas engines like the tall deck GMC engines...

 

[85_Ranger4x4]

That's what 6 speeds are for. Lol.

The 6.2l Ford performs much like my 7.3 diesel did, if I avoid looking at the rpm guage.

*with proper management.

You can't have a trans that tries to keep your little V6 just off idle when it has no power there. I have tied into a couple of those and they drive me nuts on the highway. The little V6 needs to breath but the computer tries to keep it at 1500rpm... and then the computer has a panic attack throwing gears at trying to get something done at the last minute at a hint of a hill. It was like the engine department didn't talk to the transmission department or something... and sometimes some ninny puts stupid highway flier gears in it too.

Torque peak is largely meaningless....an engine can have torque peak at 3,000 RPM but it can have adequate "torque" at much lower RPM, plenty to get the job done.....which is exactly why we look at HP or the HP curve to figure out an engines work capacity since gearing makes up the difference.

If your stuck on low end torque, this big block crate engine, the"High Torque" 502 V8, has max torque at 3200 RPM.....but it still has 490+ at 2400 RPM and I'm guessing well over 400 into the teens....

HT502 Big Block Crate Engine: 88890534 | Performance

With 512 lb-ft of torque, the HT502 big block crate engine is a powerful alternative to rebuilding - see images, dyno specs, installation info and more.

www.chevrolet.com

I can't imagine any gas small block (or big block) V8 outside of specialized industrial applications that have max torque values at 1700 RPM. Generally any engines with max torque that low are very low revving, low HP engines. The older straight 6's come to mind, like Ford 4.9L, Chevy 292, Toyota 2F, etc and maybe some of the older V8 long stroke gas engines like the tall deck GMC engines...

Offroad I do like my kinda low end torque mongers, they both peak at around 2500 so puzting around at 1500ish they are still happy. I don't need crazy gearing or a doubler to get around.

 

[nickw]

*with proper management.

You can't have a trans that tries to keep your little V6 just off idle when it has no power there. I have tied into a couple of those and they drive me nuts on the highway. The little V6 needs to breath but the computer tries to keep it at 1500rpm... and then the computer has a panic attack throwing gears at trying to get something done at the last minute at a hint of a hill. It was like the engine department didn't talk to the transmission department or something... and sometimes some ninny puts stupid highway flier gears in it too.



Offroad I do like my kinda low end torque mongers, they both peak at around 2500 so puzting around at 1500ish they are still happy. I don't need crazy gearing or a doubler to get around.

Sure, theoretically a diesel will have lower effective gearing since it's power is lower in the curve....but practically, I've never needed lower gearing than 4-low, 1st gear....particularly with an automatic. With a stick, I'd agree, lower can be better, but most HD stick shift rigs have crazy low granny gears that are all but worthless...

If you were running the Rubicon doublers make sense, but everyday wheeling, I've never needed anything lower.

 

[Deleted member 9101]

One problem with gas engines has been the hunt for horsepower (mostly for marketing purposes) has hurt the low-end torque. When Chevy switched from the good ol' tree-fitty (5.7L) to the 5.3L, hp went way up but it was actually a worse motor for towing as the torque wasn't any better, and worse the torque peak went from 1700 to over 3000 (going from memory).

Uhhhh... Ive had both and the 5.3 absolutely destroys the 5.7 when it came to towing. Who cares if it has to spin at a higher RPM to get the job done. It does it on less fuel, with less fuss, and with a higher degree of reliability.

 

[IdaSHO]

That's what 6 speeds are for. Lol.

The 6.2l Ford performs much like my 7.3 diesel did, if I avoid looking at the rpm guage.

Exactly my experience

I went from a 7.3 PSD to a 6.2 gasser.

Similar power, MUCH better truck

 

[85_Ranger4x4]

Sure, theoretically a diesel will have lower effective gearing since it's power is lower in the curve....but practically, I've never needed lower gearing than 4-low, 1st gear....particularly with an automatic. With a stick, I'd agree, lower can be better, but most HD stick shift rigs have crazy low granny gears that are all but worthless...

If you were running the Rubicon doublers make sense, but everyday wheeling, I've never needed anything lower.

I have no diesel and referenced no diesel.

I was saying like a peaky NA 4cyl compact pickup... you need all the gear you can get. Even my 2.8 V6, it was 4lo and PLANT the skinny pedal to clean 235/75-15 tires. It worked... but there is no way in $(@# I am going back to that. In the same chassis my 5.0 chants along in high second at 1800rpm cleaning 31's without a care.

With an automatic I rarely used low range in either my F-150 or my Ranger post V8 swap until I put a 5 speed in it. After the 5 speed swap 2nd low and 3rd low are really nice for trail rides. First high seems to be just a hair faster than most automatic guys run (and nowadays everybody else has an automatic)

 

[RoyJ]

One problem with gas engines has been the hunt for horsepower (mostly for marketing purposes) has hurt the low-end torque. When Chevy switched from the good ol' tree-fitty (5.7L) to the 5.3L, hp went way up but it was actually a worse motor for towing as the torque wasn't any better, and worse the torque peak went from 1700 to over 3000 (going from memory).

But that was a long time ago (relatively). Technology has advanced far beyond the 350 and 1st gen 5.3 by now.

With variable cam phasing, direct injection, higher CR, modern V8s are putting out more power anywhere on the rev band, and far more up high.

I have an old 8.0 V10 Dodge, while decently torquey, my 5.7 Hemi w/ the 8 speed absolutely embarrasses it with any kind of a trailer. Imagine a 6.4 Hemi, or the new 7.3 Ford.

 

[Martinjmpr]

Uhhhh... Ive had both and the 5.3 absolutely destroys the 5.7 when it came to towing. Who cares if it has to spin at a higher RPM to get the job done. It does it on less fuel, with less fuss, and with a higher degree of reliability.

I never towed with a 5.7 but I can tell you that the 5.3 in my '04 Suburban really struggled pulling our 3500lb travel trailer. Of course, it could have been the "perfect storm" of the 5.3 mated to a lackluster 4L60 transmission (with a wide space between 2nd and 3rd gear) plus the 3.73 final drive, and finally high altitude (11,000'+.)

EDITED TO ADD: I can't help but think how much more usable power these engine would have if they weren't mated to a power-sucking slushbox. More than once I wished for a decent 5 speed manual transmission on my Suburban.

And yes, I know that ship has sailed and we won't see full size trucks with manual transmissions ever again , but I often think that if Americans could shift their own gears they wouldn't NEED all this HP and torque from the engine.