Tyrod
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Why does the 7.3 have to have such major upgrades to match the 6.0 that has only been "chipped"?
What is the 7.3's bottleneck on power?
- Thread starter Tyrod
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Tyrod
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...or it could be a good excuse to build one that will hit the numberFire1 said:Rods exiting the block can be a "bottle neck" for us with PMR's.
DaveBen
SDD Senior Member
It is an old design that was made for trucks and not performance. The 6.0 was made with performance in mind. That and advances in the technology.
Dave
Dave
whatabudro
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Common Fuel Rail, the lack of. I don't know if the 6oh has one, but its the main difference between the new diesels and the 7.3.
The 6.0 is not common rail, but I believe is a move advanced version of the 7.3 style hydraulic actuated injectors. The 6.0 also has a better factory turbo. I think more untapped power was left on the table from the factory.
Hoss 350
My GSP, Dutch
The 6 liter is HEUI, also, but a newer generation of HEUI. The 7.3 liter HPOP would not keep up with the volume and pressure needed to make big HP. Also, the 7.3 started out much lower than the the 6 to begin with. Most were released at 235 HP, so the 6 liter had a 70 HP headstart on the 7.3 from the start. The VVT on teh 6-liter also allows them to create power where the 7.3's "dumb" turbo is not nearly as able. The stock 7.3 injectors suck, where the 6 liter had a pretty big headstart on injector flow and pressure over the 7.3. The 7.3 makes insane cylinder pressures when it is modded, as does the 6.0, but the 7.3 have a very large piston surface to transmit the pressure back to the bottom end (psi means pounds per square inch. More square inches=more pounds). I read somewhere that the 7.3 has about 25% more piston surface area than the 6.0, which means this...
At a piston surface area of 19.625" (a guess, and only a guess, but it works for a comparison) for the 6.0 and 24.53" for the 7.3 (25% more) and CPs of 2,200 psi, the stresses pushed back into the lower end by the CPs are
43,175 lbs for the 6 liter
53,996 for the 7.3
NOTE! These stresses are only what would occur if the piston was absolutely static and unmoving. I know that these stresses never actually occur in real world applications, it is just for comparisons sale.
Anyway, you can see that the 7.3 rods undergo a pretty substantially higher amount of stress, and here is the clincher, the rods, as far as I can tell, are nearly identical. YES, the 6.0 DOES have PMR's! I know this comes as a shock to some, but the PMR idea is not necessarily flawed, it is a good way to make a rod. The rods in the 7.3 are just undersized for the application, whereas they are not for the 6.0. I am sure that some will disagree and say this is a flawed analysis, but it is how I look at it.
In any case, slide a VVT, a better HPO system (or even, GASP, a HPCR!), stronger rods into a 7.3, and you are going to have a serious competitor.
Also, the programming just got better over the years, and the R&D is all going to the 6 liter, not the 7.3...
At a piston surface area of 19.625" (a guess, and only a guess, but it works for a comparison) for the 6.0 and 24.53" for the 7.3 (25% more) and CPs of 2,200 psi, the stresses pushed back into the lower end by the CPs are
43,175 lbs for the 6 liter
53,996 for the 7.3
NOTE! These stresses are only what would occur if the piston was absolutely static and unmoving. I know that these stresses never actually occur in real world applications, it is just for comparisons sale.
Anyway, you can see that the 7.3 rods undergo a pretty substantially higher amount of stress, and here is the clincher, the rods, as far as I can tell, are nearly identical. YES, the 6.0 DOES have PMR's! I know this comes as a shock to some, but the PMR idea is not necessarily flawed, it is a good way to make a rod. The rods in the 7.3 are just undersized for the application, whereas they are not for the 6.0. I am sure that some will disagree and say this is a flawed analysis, but it is how I look at it.
In any case, slide a VVT, a better HPO system (or even, GASP, a HPCR!), stronger rods into a 7.3, and you are going to have a serious competitor.
Also, the programming just got better over the years, and the R&D is all going to the 6 liter, not the 7.3...
Well the 7.3 PMR rods are sized fine for the "intended" application. Just not for adding 150+ additional HP. Then again why should the factory design that in? That is not their goal nor should it be really.
DaveBen
SDD Senior Member
That is why we spend big dollars for aftermarket hotrod parts. Those manufactures build parts that the factory never invisioned. And we get people who ask why Ford did not make the 6.0 capable of 500 hp in the rod department?
Dave
Dave
roosterdiesel
Earl needs B100
6.0L PMRs were designed to be just that....PMRs. The 7.3L PMRs were not redesigned and are almost identical to the forged pieces. The biggest difference that I noticed are the "cracked caps" on the PMRs, they tend to get out of round easier and can only be honed out to accept oversized outside diameter bearings. The beams are the same size on both, which is not good in my mind. I haven't seen any 6.0 rods(in person) but I'd like to see 7.3 forged and PMRs next to a set of them.
BTW, my experience with these rods comes from a 3 year stint as an engine machinist.
BTW, my experience with these rods comes from a 3 year stint as an engine machinist.