My New 2019

[Newsa]

Interesting discussion of the bore vs. stroke in the torque discussion. Seems like there would be more capability to increase the stroke in the inline piston arrangement vs. The V8 pistom arrangement? And more "room" to engineer in a longer stroke without crearing crank angle issues. I don't mean space when speaking of "room". I mean more engine deaign flexibility.

 

[Wayne M.]

Exactly, Newsa. That’s why Chrysler slanted their 6 in 1960.

 

[sag2]

The greater torque from a diesel engine comes from a combination of stroke and the ability to add more fuel because of the excess combustion air. When you have longer stroke it increases the lever length between the main bearing center and the rod bearing center. Just as mentioned it is like adding a cheater bar to a ratchet. The second increase comes from being able to add more fuel after the piston is past TDC on it's way down. Because there is no throttle plate on a diesel, there is always excess air in the cylinder. Once the main injection event is over, generally a few degrees ATDC there is enough oxygen left over to have a second injection event. Because the crank pin is heading to the 90 degree position where the lever length is the longest, that little bit of fuel raises combustion pressure up and adds a significant amount of torque.

 

[Newsa]

Seems increased bore would be more important in a naturally aspirated engine than a turbo/super charged design?

 

[Wayne M.]

Seems increased bore would be more important in a naturally aspirated engine than a turbo/super charged design?

I think the combustion time (dwell) is more important in this case of a lower RPM, high duty cycle Diesel, like Stan explained.
The bore/ stroke/ con rod ratio combination is tailored for the intended use of the engine. That’s the big goal of the engine designer, weather it’s an OEM engineer or a shade tree hot rodder. The purpose of the engine and it’s desired outcome must first be determined.

 

[Ozymandias]

There is a natural limit to Bore vs. Stroke as at one point the connection rod will touch the cylinder wall. Before or after TDC.

 

[gsbrockman]

Even without changing the stroke, a taller deck height and longer rods enhances torque. Look at a 427 GM truck gasser. The piston pauses longer at TDC.

I’d imagine those ol’ 413 Dodge truck engines were similarly designed to a 427 GM.

 

[Wayne M.]

The 413 truck/ industrial is a bit different from the car/ pickup engine, especially in the cylinder heads. They really made it a high duty cycle power plant. The GM 427 wasn’t much different from the pass car version. I believe the tall deck was just for lower compression. The bore/ stroke I think are the same.

 

[TFucili]

I’d imagine those ol’ 413 Dodge truck engines were similarly designed to a 427 GM.

We rebuilt a few at my buddy's shop. Some of the farmers had R-Model Mack grain trucks with OEM 413 Chryslers. Too long ago to say I could give an accurate comparison

 

[gsbrockman]

We rebuilt a few at my buddy's shop. Some of the farmers had R-Model Mack grain trucks with OEM 413 Chryslers. Too long ago to say I could give an accurate comparison

I recall reading that some of the old C-Series trucks had 413’s as standard, but IH engines available as an optional engine.

 

[Wayne M.]

We rebuilt a few at my buddy's shop. Some of the farmers had R-Model Mack grain trucks with OEM 413 Chryslers. Too long ago to say I could give an accurate comparison

Oh wow- what id give to see one of those!!

 

[SnoKing]

Chrysler 413
The 413 cu in (6.8 L) RB was used from 1959 to 1965 in cars. It was also used in medium and heavy trucks including truck-tractors such as the C-1000, up until 1979. It has a bore of 4.1875 inches.
Piston stroke‎: ‎3.75 in (95.25 mm)
Block material‎: ‎Cast iron
Cylinder bore‎: ‎4.1875
Head material‎: ‎Cast iron

 

[AH64ID]

Just to be clear on adding torque or hp, there must be an rpm shift down in the power band to add tq for the same hp, and vice versa. Rpms, Hp, and tq are mathematically paired and if you know 2/3 you can calculate the remaining one.. on any engine from bunker oil slow (or slower) to turbine speed.

So stroke doesn’t add torque, it helps allow for lower rpm operation which is where the big torque number comes from. Same thing with gas vs diesel, the torque difference is from the rpm difference which is allowed by the type of fuel.

5252 is the magic rpm where hp=tq. Below that there is more tq than hp, and above there is more hp than tq. Think of torque as how much work you can do, and hp as how fast. All the below rpms will do the work at the same rate, but the lower rpms means more work is being done. That doesn't even start to get into gear reduction and torque multiplication thou, which is why a pair 20,900 rpm turbines can lift 24K lb helicopters with 355 lb/ft of toque each.

1 hp = 5252 lb/ft at 1 rpm
1 hp = 4 lb/ft at 1313 rpms
1 hp = 2 lb/ft at 2626 rpms
1 hp = 1 lb/ft at 5252 rpms
1 hp = .75 lb/ft at 6565 rpms
1 hp = .5 lb/ft at 10504 rpms
1 hp = .25 lb/ft at 21,008 rpms

Easy to see why diesel makes so much torque when you operate most of the time below the 2:1 ratio of tq:hp.

It also explains why most test tows didn't feel much difference on the 19 HO vs the 18HO. At rated rpm (2800) the 15 hp is only 28 lb/ft more, and at peak torque the 70 lb/ft is only 24 hp extra, and it's peak torque is 100 rpms higher. Not that the numbers are shabby, just hard to feel in the driver seat. Even the difference from 15-18 with minor torque updates is hard to tell, but a 15-19 will be noticeable.





In terms of shifting I played with TH and non-TH a little over the weekend. With my normal acceleration the truck would consistently shift, during acceleration, at ±1750 in non-TH and ±2000 in TH.

 

[Wiredawg]

Just to be clear on adding torque or hp, there must be an rpm shift down in the power band to add tq for the same hp, and vice versa. Rpms, Hp, and tq are mathematically paired and if you know 2/3 you can calculate the remaining one.. on any engine from bunker oil slow (or slower) to turbine speed.

So stroke doesn’t add torque, it helps allow for lower rpm operation which is where the big torque number comes from. Same thing with gas vs diesel, the torque difference is from the rpm difference which is allowed by the type of fuel.

5252 is the magic rpm where hp=tq. Below that there is more tq than hp, and above there is more hp than tq. Think of torque as how much work you can do, and hp as how fast. All the below rpms will do the work at the same rate, but the lower rpms means more work is being done. That doesn't even start to get into gear reduction and torque multiplication thou, which is why a pair 20,900 rpm turbines can lift 24K lb helicopters with 355 lb/ft of toque each.

1 hp = 5252 lb/ft at 1 rpm
1 hp = 4 lb/ft at 1313 rpms
1 hp = 2 lb/ft at 2626 rpms
1 hp = 1 lb/ft at 5252 rpms
1 hp = .75 lb/ft at 6565 rpms
1 hp = .5 lb/ft at 10504 rpms
1 hp = .25 lb/ft at 21,008 rpms

Easy to see why diesel makes so much torque when you operate most of the time below the 2:1 ratio of tq:hp.

It also explains why most test tows didn't feel much difference on the 19 HO vs the 18HO. At rated rpm (2800) the 15 hp is only 28 lb/ft more, and at peak torque the 70 lb/ft is only 24 hp extra, and it's peak torque is 100 rpms higher. Not that the numbers are shabby, just hard to feel in the driver seat. Even the difference from 15-18 with minor torque updates is hard to tell, but a 15-19 will be noticeable.





In terms of shifting I played with TH and non-TH a little over the weekend. With my normal acceleration the truck would consistently shift, during acceleration, at ±1750 in non-TH and ±2000 in TH.

That's why it was interesting to hear folks comparing feel between 4th Gen HOs and the new HO. It would be negligible, unless maybe SO to HO. I've been adding power to my trucks from my 93 all the way to my current 2017. After all that, couldn't really feel ~30HP/60Lb ft, but could feel nice improvement ~60HP/120LB ft.

That's why going from my 09 4500 with ~90HP/180LBFT added compared to my stock 17 5500 was a little tough. I added ~60HP/120LBFt to my 17 and love it. I haven't dyno'd either truck; butt in the seat is the BEST measure of usable power, IMHO. Stock, my 17 is 325HP/750LBFt TQ.

Thanks y'all for making this an interesting AND educational thread.

Cheers, Ron

 

[kthaxton]

So stroke doesn’t add torque,

But it does, it's basic physics. You increase the lever length, you increase the torque.

 

[AH64ID]

But it does, it's basic physics. You increase the lever length, you increase the torque.

You can't maintain hp and rpm and increase torque. So for torque to increase something else has to change, is it the rpms decreasing or the hp increasing?

The whole equation has to be looked at, even with basic physics.

Generally speaking a motor with a longer stroke is a lower rpm motor than one with a shorter stroke, that makes for a higher torque producing motor... generally.

 

[Wayne M.]

Motor?

 

[Ozymandias]

Motor!

 

[AH64ID]

Motor?

Motor?

 

[kthaxton]

You can't maintain hp and rpm and increase torque. So for torque to increase something else has to change, is it the rpms decreasing or the hp increasing?

The whole equation has to be looked at, even with basic physics.

Generally speaking a motor with a longer stroke is a lower rpm motor than one with a shorter stroke, that makes for a higher torque producing motor... generally.

You are over complicating it. Let's slim it down to a single power stroke of the piston....all other things being equal, there will be more twisting force (torque) at the crank with a longer stroke vs. a shorter stroke....because there is more leverage applied to the crank.