Towing with PMRs and RPMs

LakeBum

New member
Joined
Aug 16, 2017
Messages
57
Reaction score
0
I've got a stock injector truck (SXE turbo) with 3.73s and 35s.

In third gear at 61 MPH Im turning 2200 RPMs. POWER and EGTS are GREAT.

If I shift to 4th, RPMs fall to 1750 and about 68 MPH. IMHO this is to fast of speed for what I feel comfortable towing at. But the truck will do it and pull to 75 MPH as RPMs rise. Again EGTs are not a problem.

I'd like to get a smaller tire to raise my 4th gear RPMs so I can use 4th for most things and then 3rd when I really need to pull a grade.

Question is what RPM is safe for towing with PMRs. Stock tires and gearing would be 1830 RPMs at 65 MPH. is 1800-1900 safe towing heavy with PMRs?
 

DieselDC

Member
Joined
Jan 10, 2017
Messages
401
Reaction score
0
keep driving. Plenty of things to worry about. Pmr ain’t on the list.


—————signature—————
~Don’t overthink something simple~
...:uptight people suck:...
 

Petro

Well-known member
Joined
May 22, 2011
Messages
1,209
Reaction score
34
Location
Lincoln Nebraska
I'm trying to understand why you're worried about connecting rods at stockish power levels? If powdered metal rods were that weak, every 7.3 that used them would have blown up by now. If you get up closer to 500, then you can start to worry about low rpm torque/ cylinder pressure. Until then drive it like you stole it.
 

The Brad

New member
Joined
Feb 5, 2014
Messages
375
Reaction score
0
Location
People's Republic of CA
There has been more than a handful of stock injectored 7.3s tossing rods back when tuning wasn’t as understood. Now that tuning is better, will it save the rods while running an SXE which can easily push over 20 psi at 1700 rpm sustained while towing? The S467 has been dubbed a forged rod killer, so can the SXE do the same to a PMR rod?
 
Last edited:

DieselDC

Member
Joined
Jan 10, 2017
Messages
401
Reaction score
0
There has been more than a handful of stock injectored 7.3s tossing rods back when tuning wasn’t as understood. Now that tuning is better, will it save the rods while running an SXE which can easily push over 20 psi at 1700 rpm sustained while towing? The S467 has been dubbed a forged rod killer, so can the SXE do the same to a PMR rod?



20psi huh.... keep DRIVING...


—————signature—————
~Don’t overthink something simple~
...:uptight people suck:...
 

Petro

Well-known member
Joined
May 22, 2011
Messages
1,209
Reaction score
34
Location
Lincoln Nebraska
There has been more than a handful of stock injectored 7.3s tossing rods back when tuning wasn’t as understood. Now that tuning is better, will it save the rods while running an SXE which can easily push over 20 psi at 1700 rpm sustained while towing? The S467 has been dubbed a forged rod killer, so can the SXE do the same to a PMR rod?

Do you have any idea how f*cked up the tune would have to be to make that happen? I had several customers kick the ever living **** out of pmr motors for 2 or 3 years with 238's and a 38r, and only one had a rod issue when he hydrolocked his motor when a gasket failed. This isn't 2003, tuning has come a looooonnnnnnnggggg way. Start worrying when boost reaches 40 psi under 2k rpm, until then run the piss out of it, you won't hurt a rod on stock injectors with any sort of modern tune.
 
Last edited:

LakeBum

New member
Joined
Aug 16, 2017
Messages
57
Reaction score
0
Do you have any idea how f*cked up the tune would have to be to make that happen? I had several customers kick the ever living **** out of pmr motors for 2 or 3 years with 238's and a 38r, and only one had a rod issue when he hydrolocked his motor when a gasket failed. This isn't 2003, tuning has come a looooonnnnnnnggggg way. Start worrying when boost reaches 40 psi under 2k rpm, until then run the piss out of it, you won't hurt a rod on stock injectors with any sort of modern tune.

Would be interesting to here from a Cody on the subject...
 

superpsd

Active member
Joined
Jun 10, 2014
Messages
1,928
Reaction score
3
Location
Missouri
Excessive cylinder pressure is what kills PMRs. Like running a tune with way too much timing advance. Jacked up SOI tables and multipliers were the cause of blowing out PMRs. On a stock injector truck you dont have much to worry about as long as the tuning is good. I think there has even been a few to run 300cc injectors in a PMR motor as long as the tune is good.
 
Last edited:

ja_cain

Active member
Joined
Aug 10, 2013
Messages
4,597
Reaction score
2
I think the general rule of thumb is to keep torque down low below a 1000.

Sent from my Pixel 2 XL using Tapatalk
 
Top