Safe operating RPMs? 7.3L IDI N/A

Bigbirdtrucker

Registered User
Joined
Jan 1, 2017
Posts
14
Reaction score
0
Location
Florida
What is the safe operating range in RPMs for our 7.3 idi naturally aspirated engines? And does anyone know the redline on these engines? What kind of rpms are you turning on the interstate?
 
Last edited:

towcat

Supporting Member
Supporting Member
Joined
Jun 24, 2004
Posts
18,196
Reaction score
1,437
Location
SantaClara,Ca/Hamilton,TX
loaded, I run off the governor.
unloaded, I max out around 3000 rpm.
depending on your rear ratio, your top speed is limited there plus air friction. TX DPS had me clocked at 105 once. CC dually 7.3 turbo IC'd ZF5 4.10 rear.
your results may vary.
 

Clb

Another old truck
Supporting Member
Joined
Mar 1, 2013
Posts
5,695
Reaction score
2,162
Location
nannyfornia
Stickies....check em out. Agnem aka Mel has this covered
Governors kick in around 3600 ish ymmv
 

austin92

Full Access Member
Joined
Jul 20, 2016
Posts
982
Reaction score
295
Location
Brazil. IN
What is the safe operating range in RPMs for our 7.3 idi naturally aspirated engines? And does anyone know the redline on these engines? What kind of rpms are you turning on the interstate?

I've always heard these will turn 3800 all day long. Not sure what equipment, but I read heavy machinery with these engines had 3800rpm fuel shut offs and our trucks have 3300. I believe r&d's pumps have 3800 governors. They don't have much ass past 3k anyways. I turn 2200rpm at 70mph on a zf5 with 3.73s and stock tires


Sent from my iPhone using Tapatalk
 

Hydro-idi

Full Access Member
Joined
Nov 8, 2011
Posts
2,273
Reaction score
359
Location
Lodi, California
~3800 rpm is what these engines can safely wind up to. That's what my mini moose from Mel was calibrated to as well.
 

mjs2011

Full Access Member
Joined
Jun 8, 2013
Posts
307
Reaction score
5
Location
Brookings, SD
loaded, I run off the governor.
unloaded, I max out around 3000 rpm.
depending on your rear ratio, your top speed is limited there plus air friction. TX DPS had me clocked at 105 once. CC dually 7.3 turbo IC'd ZF5 4.10 rear.
your results may vary.
105 mph with 4.10s? You running gear vendors? Or super tall tires?

Sent from my VS990 using Tapatalk
 

mjs2011

Full Access Member
Joined
Jun 8, 2013
Posts
307
Reaction score
5
Location
Brookings, SD
105 mph with 4.10s? You running gear vendors? Or super tall tires?

Sent from my VS990 using Tapatalk
I just punched it into my excel sheet speed calculator. That's 3200 rpm assuming stock tire height and a zf5 with 4.10 rear.

I'm surprised. I had mine up to 95 once and don't think I'd want to go any faster than that. Plus she was chiefin pretty good.

Sent from my VS990 using Tapatalk
 

Macrobb

Full Access Member
Joined
Jun 12, 2016
Posts
2,380
Reaction score
1,234
Location
North Idaho
With a GV(and enough power), 100 isnt a big deal, really. I did it once a while back on a really high speed limit highway.


I've got a Ford IDI Turbo booklet which specifies that 3800 is the limit that should never be exceeded.
That it should be governed to 3300-3600 depending on load.

On my 88, after I first put my R&D rd2-110 pump on, I hit some very high RPMs. The 110+ CC pumps are more or less "ungoverned", and you can easily hit 4K+ RPM.

However... you want to be careful doing that. I revved it too high a couple of times and found that a couple of rocker arm bolts decided to rattle loose.

I'm guessing with a properly built motor, yeah, you could probably handle 4500+ RPM, but the real problem is that you don't have much power up there.
The "crossing point", where increasing turbo boost and decreasing fueling from the pump hits is around 2800 - iit's just a limit of the rotary style pumps.
As such, generally you'll find that your IDI's dyno curve will end up peaking in the 2600-3400 range depending on turbo capabilities.
 

pelky350

Full Access Member
Joined
Sep 11, 2014
Posts
1,546
Reaction score
382
Location
Springfield, OR
With my stock pump it would defuel at 3300 and not go much higher, during a burn out anyway lol new r and d pump I have to watch it it will try and run like 4000+ which after like 3100 there's not much power to be gained so Erving that high is kinda pointlessly hurting the engine I would think
 

towcat

Supporting Member
Supporting Member
Joined
Jun 24, 2004
Posts
18,196
Reaction score
1,437
Location
SantaClara,Ca/Hamilton,TX
I just punched it into my excel sheet speed calculator. That's 3200 rpm assuming stock tire height and a zf5 with 4.10 rear.

I'm surprised. I had mine up to 95 once and don't think I'd want to go any faster than that. Plus she was chiefin pretty good.

Sent from my VS990 using Tapatalk
I can't telll you the exact speed since I dont have a GPS at the time and my speedo ended at 85mph. But be rest assured, his radar was carefully calibrated. :D
 

rustygold

Full Access Member
Joined
Feb 19, 2015
Posts
468
Reaction score
42
Location
conway Arkansas
I can't tell you even if the pump can go to a higher rpms doesn't mean the pistions velocity is safe. 5000 rpms is the maximum pistion velocity but the weight of the pistion will decrease that some to 4000 rpms I would say the safe side. This is all on stock setup and plus rod stretch at that speed could tap the head possible.

Sent from my SAMSUNG-SM-G870A using Tapatalk
 

rustygold

Full Access Member
Joined
Feb 19, 2015
Posts
468
Reaction score
42
Location
conway Arkansas
I run at 65 mph is 2000 rpms best fuel economy for me but I'm running 4.11 with and e4od stock tire hight.

Sent from my SAMSUNG-SM-G870A using Tapatalk
 

Dieselcrawler

Professional wrench holder
Staff member
Joined
Jun 4, 2010
Posts
5,284
Reaction score
616
Location
Quakertown Pa
As stated above, they can run gov all day long. Some truck you have to just to keep up with traffic due to the gearing. My old 83 with 3.07 gears, 33"s and just a 4 speed would hit 110 at the gov.
 

jwalterus

Made in America
Joined
Feb 11, 2010
Posts
2,550
Reaction score
716
Location
Garrison, ND
What is the safe operating range in RPMs for our 7.3 idi naturally aspirated engines? And does anyone know the redline on these engines? What kind of rpms are you turning on the interstate?

As stated before,
Under load, anything under the factory governor (3600ish) is safe, if you are thinking free-rev speed, just don't...............
I don't like to go over 2700 with my truck, I have when I've been towing heavy, but over 3000 just doesn't feel right........

I can't tell you even if the pump can go to a higher rpms doesn't mean the pistions velocity is safe. 5000 rpms is the maximum pistion velocity but the weight of the pistion will decrease that some to 4000 rpms I would say the safe side. This is all on stock setup and plus rod stretch at that speed could tap the head possible.

Sent from my SAMSUNG-SM-G870A using Tapatalk


You need to change your little saying under your avatar to "The anti-DYoung14" after that post...... :rotflmao:rotflmao:rotflmao:rotflmao:rotflmao:rotflmao:rotflmao:rotflmao

Unfortunately, since I see you joined in 2015, you aren't going to get it........
 

rustygold

Full Access Member
Joined
Feb 19, 2015
Posts
468
Reaction score
42
Location
conway Arkansas
Jwalterus I don't get that. Seen lots of big block come apart in all directions from over speeding a motor.

Sent from my SAMSUNG-SM-G870A using Tapatalk
 

Latest posts

Forum statistics

Threads
91,217
Posts
1,128,471
Members
24,043
Latest member
tottripp

Members online

Top