I recieved some information today concerning the new 6.7 and 4.5.ltr B engines in this months training packet. As of now, the only offering will be agricultural use. With ratings for the 6.7ltr at 194hp and 575lb tq at 1400 as of right now.

Some interesting things that I found was that this new engine used the Bosch VE Rotary pump, this is the same pump that is found on the 1st gen Dodge/Cummins engines. However, the gear train is arranged in the back like the 3rd gen engines and the 6.7ltr engine does not use the AFC head VE, only the 4.5ltr. In this application, it also uses the diapraghm type lift pump which is also used on the 1st gen engines. Basically, these engines are purely mechanical at this time.

 

So these are "B" series motors with more displacement? Bigger bore, longer stroke, or both? Are they 12/8 or 24/16 valve?

 

Easy Dave.

Yes, these are "B" Series engines.

These engines are offered in a four and 6 cylinder config. Both designs have a 104mm (4.09in) bore and 132 (5.20) stroke. This gives displacement of 1.12 liters (68.35 cubic inches) per sylinder. The 6 cylinder displaces 6.7 liters (408.9 cu in.) and the for cylinder is 4.5 liters or 274.6 cu in. And yes, these are 12v engines.

Like I said, as of right now, these are only being implemented into agricultrural use as they could not meet on highway regs right now. But, this may gives us a peek at where the B lineup is heading.

 

Dang, that is a long stroke! That's gotta limit the RPM potential. Did they shorten the rod length, too, or just raise the deck height to compensate?

 

They probably had to raise the deck. The rod ratio on our engine is already pretty short at 1.62

jlh

 

That's what I was thinking, but it's an ag engine with peak HP rating at 2,500 RPM. They might have figured on "getting away with it", since it doesn't have to be able to run at 3k all day like a 5.9. I dunno, do you think it's cheaper to raise the deck or shorten the rods? Myself I'd want to raise the deck, but I'm not a bean counter.

 

AGCO (Bought out Deutz-Allis, Allis-Chalmers) uses the 6.7L in it line of 100-150 hp tractors. So far, good as the 5.9L, except that it's a structural block, and has no frame (a feature the last model of tractors had, and they pushed that very hard because we were the only ones that had it, now a structural block is better ?)

They do run pretty fast, 23-2400 rpm if I remember, and idle at like 950 rpm. But throttle response is great, and the power seems to be there all the time. I really wondered about going back to a rotary pump, but for emissions reasons the variable timing of the VE is probably what won it the spot. I guess the P-7100 is just too stupid.

Time will tell, we were just getting used to the 5.9L though, then the EPA causes us to try this new one.

Chris

 

Our rods are 6.85 inches center to center.

Don~

 

YIKES!!

I thought they were over 7" by quite a bit. That's what happens when you store things on top of your head

6.85/4.72= 1.45!!

Did I do the math, right?? That's a VERY short rod ratio! Like 400 chevy short.

I've heard Honda uses some really short rod ratios, under 1.45.

I bet that Cummins gets away with it because:
1) the pistons are very tall (thus, stable)
2) the RPMs are generally low

To put this in perspective for others on the board-- the great 426 Hemi had rods very similar in length to the 5.9 (6.86 vs 6.85). But the Hemi had a MUCH shorter stroke-- only 3.75 inches!

justin

 

Justin,

I was dead wrongo on the center to center. I decided to measure a rod today and stop trusting my memory

Big end = 2.87"
Small end = 1.57
Inside distance between the big and small ends was 5.34"

So, like you said the rod center to center is 7.5" NOT 6.85'!!

7.56/4.72 = 1.60 ratio.

GEESH!!

Im a tard sometimes!

Don~

 

Here is a shots of the new fracture split rods

 

another

 

Im not sure what I think about this rod yet when compared to the older ones. The oldest 12 valve rod was the worse. It used M14 capscrews to hold the cap on. It had a pretty large oiling hole at the small end also.

The 24 valve ISB rod was about the same material but used a M12 capscrews and they did away with the oiling hole in the small end of the rod to provide more strength.

The ISBe rod uses a fracture split cap ( something I like ) and also has no oiling hole, but they went to a M11 capscrew. It is more refined, smoother and just looks better, but the M11 capscrew size makes me somewhat nervous at this point-until I get more details. The larger capscrews in the past were to keep the cap from walking too much. The fracture split deals with the cap walk for certain. Perhaps they decreased the size to leave more material in the rod itself?? I need to talk to a few folks I know at Cummins and I am having ARP test the capscrew strength. The capscrews are super cheesy looking. Poor machine work. I cant tell the material, but it looks like a medium strength alloy. I am rockwell testing the hardness tomorrow at the shop. I really wanted to use the fracture split rod in this shortblock I am building but the capscrews are going to have to be dealt with first. ARP quoted me anywhere from 400-1400 bucks to make a set of sweetheart capscrews

Don~

 

Don, thanks for the great pics and the accurate info. I've never seen any 5.9 internals in person, and when I do, it's going to be expensive

On the capscrews: the smaller M11 screws are probably the result of going to the fracture-split design. When you combine the fracture-split design with the offset cap angle, it takes a LOT of load off the screws.

In a normal cap setup (think domestic V8), the cap screws have to generate enough clamping force to keep the cap seated at high rpm-- lots of force. Since the cap-to-rod connection did little anchoring on its own, the clamping force had to provide a high level of normal force to maintain enough friction to prevent capwalk.

With the fractre-split design, there are millions of tiny imperfections on the mating surfaces that just happen to fit together perfectly. The result is a Velcro-like fit and a LOT of lateral stability. Industrial velcro is pretty grippy when loaded in tension, but AMAZINGLY strong when loaded in shear.

So the capscrew just basically has to maintain enough force to keep the "velcro" connected. The offset cap reduces the amount of force this will require.

Furthermore, the DIRECTION of the offset on the rod is done for a reason. It provides maximum strength when the rod is loaded in tension. Visualize the stresses on the rod on compression and power strokes, then think of the orientation of the offset, and you'll get my meaning.

So, my guess is that the smaller M11 screws are the "payoff" of going with the superior fractured cap design-- Cummins may have felt that the stronger screws were no longer needed.

If you're worried about the stock capscrews, just magnaflux 'em, shotpeen the shanks (not threads, obviously) and call it good.

One last thing-- the smaller screws allow for a more rigid cap (smaller holes). The thicker cross section allowed by the smaller screws may increase the rigidity enough to where the engine's harmonics affect the cap less-- less fatiguing of the caps.

Justin

 

I guess the biggest concerns I have with the new rod is the steel they used to forge the rod VS the old steel they used in the past.

The older steel was a bit stronger over the newer stock. The old steel ( 38 MnSi Vs 5 ) was the strongest, but you cant fracture split that material like the newer steels designed specifically to be fracture split. Most of the newer fracture split style steels are C70. Its just not as strong. This of course does not mean the rod is not capable of holding up to the abuse. I was glad to see the wide parting line indicating the rods are at least forged and not a powdered metal product. There is some sneaky wording being used by some mannufacturers on powdered metal products. Like "Forged steel cracked cap rod" or Forged Steel fracture split rods" Some are leaving out the "powdered metal" portion when they are powdered metal in fact. Some are actually forged steel like the Cummins rod and not powdered metal!!!

Second, the capscrew quality is lacking. I need a better quality capscrew to replace this cheesy thing with. For some unknown reason the capscrew is threaded the entire length. It only needs to be treaded about 1.250" but it is 2.25" under the head and the threads are 2.050". The material appears to be some cheap stuff. Just good enough to get it done. I could be wrong. ARP is testing the fastener for me and I will report back the results.

Don~