Running ISB close to the redline

[TomGolden]

I know a little about diesels, but am by no means anywhere close to an expert. I had always been under the impressions that diesels didn't like to run anywhere near their redline (rpm wise). But not too long ago someone posted on the Ford diesel site that modern diesels, at least those designed for pickups, could be run all day right at the redline and suffer no problems at all.

I have about a 20 mile each way work commute, and about 3 - 4 times a year make trips to visit family in Southern Cal, about a 1000 mile round trip for me. I don't anticipate towing much for at least a few years, and not likely to haul heavy loads very often either. When on longer trips, I'd like to be able to cruise at around 80 mph, and while I know with the 6 spd, that wouldn't be even close to the redline, I was just curious.

Thanks,
Tom


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Tom Golden
Intense Blue 2001 2500 SLT QC 4X4 ETH/DEE, Tow & Camper packages, Ltd. Slip on order
2001 Bright Blue Mustang Cobra on order

 

[_Bill]

I hope you ordered the 3. 54 axle ratio if you intend to cruise at 80 mph.

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2001. 5 2500 QC, ETH/DEE, SLT plus, LWB, 4x4, solid white w/agate leather, 3. 55 LSD, camper/trailer tow, 241HD,TT mirrors, 4 wheel disc brakes

 

[TomGolden]

Bill, thanks for the reply. I did in fact order it with 3. 54 rear end, but why do you feel this is so important? I realize that with 3. 54's I would be able to keep the engine at lower RPMs than with 4. 10's, but would it really make that much of a difference?

Thanks,
Tom

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Tom Golden
Intense Blue 2001 2500 SLT QC 4X4 ETH/DEE, Tow & Camper packages, Ltd. Slip on order
2001 Bright Blue Mustang Cobra on order

 

[Ski Bum]

With 265/75-16 tires on a 2500 you're at about 2200 RPM at 80 MPH with 3. 54 gears, and at about 2550 RPM with 4. 10 gears. Yes you should be able to run the engine all day at 2550 RPM, but if you're not towing you will keep looking at the shifter wishing you could shift up one more gear to quite the engine. 2500 RPM is usually where I shift to the next gear (when accelerating) so it seems like a high RPM for continuous operation.

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Just got my 2001 2500 QC, SB, 4x4, ETH 6-sp, 3. 54 LSD, SLT++ (everything but those lights on top of the roof), White over Silver, Tan leather. Picked it up 8/31/00.

 

[_Bill]

Tom- ditto on Ski Bums reply.

 

[Pete Peterson]

Tom, Diesels are by design meant to run at governed RPM. it doesn't hurt them a bit. Look at all your diesel powered generators they sit on the governor limit all day long. I expect the motor might last a couple of weeks longer if you keep the RPM down a little but thats why the govenor is there. Their not like gassers. Regards Pete

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99'3500,quad cab,4X4,a/t
3:54,all the right packages!PROPER VALVEMENT

 

[Bob-TEXAS]

Dittoes on the 3. 54's, I have that on my 3500 5sp and when empty I wish I had another gear. That is with stock 215 tires. I've pulled some heavy loads for short distances, and never needed 4. 10's.

 

[illflem]

Fuel economy will go down at higher rpms,the 3. 54 is the way to go unless you're towing heavy loads. I found that once the rpm gets over 2000 the milage really takes a dive.

 

[StakeMan]

I have the 4. 10 ratio and drive 80-85 mph on the highway and still get 18. 6 mpg unloaded. My father's 6 spd/3. 54 gets about the same at that speed. I got the 4. 10's so I could go to a taller tire later on.

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2001 Flame Red Sport, Auto, 4. 10, 4x4, LOADED!, DC Sport Brush Gaurd, DC Painted Running Boards, DC Splach Gaurds, Line-x over the rails

1998 Durango SLT+

2000 FL60, 16 ft. Flatbed, Cat Powered

 

[TORQUED]

I have the cummins cheatsheet and peak economy is at 1600 and the ISB300 peakpower ia at 2500. They recomend operating at 1900-2200 This is where the ISB is the HAPPYEST(spelling)

 

[JyRO]

Tom,

The 3,300 rpm redline is still very low rpms. Whether its running on the governer or not. For example (these may not be real good examples), I raced motorcycles. Mine redlined at 14,000 rpm but the ignition wouldn't shut off until 15,000 rpm, and it ran great all the way to the rev limiter. And where's the redline on a modern V-8 gas motor, it's pretty high (compared to 3,300 rpm). Of course I wouldn't want to run the engine at that speed for any extended length of time. Too loud and too much fuel.

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Y2K 2500 Cummins ETC/DEE, SLT+, 4X4, Quad, LB, Intense Blue Sport, 3. 54 anti-spin, rear aux. springs (camper special), sliding rear window, all options except cab clearance lights including agate leather, totally stock, some ring fell off, whistles louder since & D/C must have screwed up on the wiring cause the fogs stay on with high beam. Since everybody else listed their toys, I will too.
1995 Kawasaki ZX6-R (For Sale)
1990 Toyota Celica
1983 Mazda RX-7 GSL (For sale)

 

[Alan Reagan]

I'm with the StakeMan. I can run 80 with the 4. 10. When you get on it at 70 it will goes to 80 with no problem. That's about 2550 and it isn't straining at all. I can go to bigger tires later and drop the ratio if I want. Running to the redline. No problem with a diesel. But 80 MPH is a ways from it.

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2001 HO 6 spd 2500, 4. 10 LSD, Towing Package, Electric Brakes, SPA EGT/Boost Gauges, Running Boards, Fog Lights, Real Backup Lights, Running Boards

 

[Turbo-6]

Hi Tom,
A lot of people don't like to run the ISB to redline for various personal reasons, myself included. But, I think the facts are that they are built to run efficiently at the redline 24/7 and have a long productive life.


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99 3500 Reg Cab, Red, 2wd, 5spd, 4:10

 

[Sean Flanagan]

The marine spec ISB's I believe are governed at 2800rpm, where they are run all day long. I am pretty sure the only conifg of the ISB that has the 3400 limit is for the Dodge Ram where it should only be at intermittently.

 

[BV]

Has anyone seen the Cummins Spec for an ISB?? I think that most non-DC applications are governed at or below 2600 and with that being said I believe that DC bumped up the redline to help compete with the v8. Personally I don't think it's good to run it on the gov all day unless the gov is set properly. Gen-set govs I have seen are set for peak HP/Torque which is below redline.
BTW - Mine can hit 3500 rpm.

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4-sale with less than 19,000 miles. '99, 3/4, QC, SLT, 4x4, ISB, 5sp, 3. 5xlsd, tow pac, HD tcase, tow mirrors, camper pac, White over driftwood, Mist gray interior.

 

[Vaughn MacKenzie]

Yes I think most or all other applications the ISB is governed under 3000 rpm. There is a definite reason diesels don't rev like gassers: HEAVY pistons and HEAVY connecting rods. Even though the ISB has great bearings running it at redline all the time certainly can take its toll on the bearings.

I rap mine out quite a bit but try to keep it inder 3000 rpm unless I'm REALLY getting on it. Now that it's BOMBed with the upgraded fuel lines and injectors, it is very easy to rip it right to the redline since there is now power falloff past 2800rpm like before.
Vaughn

 

[Royal]

Originally posted by Pete Peterson:
Tom, Diesels are by design meant to run at governed RPM. it doesn't hurt them a bit. Look at all your diesel powered generators they sit on the governor limit all day long. I expect the motor might last a couple of weeks longer if you keep the RPM down a little but thats why the govenor is there. Their not like gassers. Regards Pete

Pete, Small & midsize gen set's are govenored
at 1800 RPM, the speed required to generate power at 60 cycles. They do not run at the normal full engine speed.

 

[Mr. B]

If you want low rpms try A Gear vendors 22% Overdrive. Mine with the 3. 54 Auto goes 94mph at 2000rpm and 130 @ 2700rpm. if you want to run near redline look for 150mph if you add 150hp.
If you want info Email me.



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99 SLT auto Q. C. 3. 54 W/: GearVendors 22% OD,Velvet Ride,Rino Lining,Snug Top Highliner,Smittybuilt,4" exhaust,K&N,275 injectors,VA,gauges,Named "The Sleeper"

 

[Turbo-6]

Check out this thread for some interesting info on what the ISB capable of RPM wise. I don't think 3400 is going to hurt anything unless there is already a problem.
https://www.turbodieselregister.com/ubb//Forum4/HTML/002262.html

 

[Pete Peterson]

Royal, your right except the generators I worked on were 400 cycles and precise to with 1. 5 db. Regards Pete