What is the 7.3's bottleneck on power?

[Fire1]

Here is some 7.3 rod pics http://www.dieselinnovations.com/gallery2/v/tech/forged-vs-pm/

 

[roosterdiesel]

I've seen both those rods in person. What I would like to see is a 6.0 PMR next to both types of 7.3 rods.

 

[Hoss 350]

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.

Interesting. Good point...

 

[smokyred]

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. Weren't the last of the 7.3's rated at 250HP, while the 6.0's are 325.
The stock 7.3 injectors suck, where the 6 liter had a pretty big headstart on injector flow and pressure over the 7.3. Swamp's lists the 6.0 injectors at 135 mm^3, and they list the late '99 and up 7.3's AD injectors at 140-160mm^3. So doesn't that mean the 6.0 injectors flow less from the factory than late-model 7.3's?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). With proper programming, CP's can be kept in check, Jonathon said they were able to reduce CP's without any power loss with programming.

 

[Hoss 350]

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. Weren't the last of the 7.3's rated at 250HP, while the 6.0's are 325.
The stock 7.3 injectors suck, where the 6 liter had a pretty big headstart on injector flow and pressure over the 7.3. Swamp's lists the 6.0 injectors at 135 mm^3, and they list the late '99 and up 7.3's AD injectors at 140-160mm^3. So doesn't that mean the 6.0 injectors flow less from the factory than late-model 7.3's?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). With proper programming, CP's can be kept in check, Jonathon said they were able to reduce CP's without any power loss with programming.
That is why I said *most* were released at 235 HP. Some were even released at 275 HP IIRC, with the manual trans.

As far as the injectors, you have to realize that the 6.0 is a smaller displacement engine, so of course it will take less fuel per shot. The 7.3 with 140's was about 153 mm per liter of engine displacement, and as good as 175 mm per liter of engine displacement with 160's (which I don't think were ever offered from the factory). The 6.0 with 135's is at 180mm per liter engine displacement.

Yes, they can reduce CPs without reducing power, but the fact remains that increased CPs will break a 7.3 sooner than a 6.0. Merely the point i was trying to make.

I am just trying to make some points, none of what i've said should be presented as, or taken as, gospel. No one really knows what the difference between the engine are, since by the PMR logic, the 6 liter should be breaking at 400 HP, also....

 

[smokyred]

Learnin' something new

Hey Hoss 350, I was asking those questions because I wasn't sure of the answers. I never thought about the flow of the injector vs. engine displacement, guess I learn something new everyday(see sig, lol). I don't really know much about the 6.0's other than what bits and pieces I have picked up from conversations, I have only put gooseneck hitches on some, not worked on the engines.

I am curious though, about what you said of CP's, you said 7.3's break sooner. Would head gaskets blowing be a part of CP's? As I have heard(just heard) that 6.0's will blow head gaskets or "puke" coolant when run really hard, even stock? Right now I have a program (BulRid8) on my chip that works great for my setup, but I have been told (by the guy from Swamps that burnt my chip) that when I get injectors that I need the program removed because 7.3 guys have popped head gaskets because the program has alot of timing and can run high CP's.

So if the 6.0 HG problems is because of CP's, then my truck would be less prone to breaking because of CP's than a 6.0, right?

BTW, I have factory forged rods if that makes a difference.

Dave I hope my last post didn't sound harsh, it wasn't meant to be.

 

[roosterdiesel]

The 6L pops HGs because of the lack of head bolts. Ten I believe, not enough to hold the heads down, I believe some have lifted heads when running studs.

The 6L PMRs aren't a problem looks like since they were designed to be that material. Red Racer has proved that against the Snow White's aftermarket bottem end 7.3L. Maybe DI found something that won't turn into a banana with all that NOS he's running.

 

[Weweld]

The PMR's have not been a problem yet , not sure how much more they will take but we will push it harder. The headbolts are not that big of deal in our motor as we have not had any problems with them yet. We do puke coolant from time to time but that is from coolant overheating as the temps reach 260 degrees , so we are working on that problem. Yes we test the coolant from time to time to make sure the head gaskets are still in place. This is just our point of view and others may be different.

GENE

 

[roosterdiesel]

Gene,

Keep up the great work! Are you still running stock head bolts and gaskets?

 

[Weweld]

Yes we will run the stock bolts and gaskets till they give up.

GENE