Running ISB close to the redline

[TomGolden]

Alan, Ski Bum,

Thanks for the RPM number comparrisions between the 3. 54's and 4. 10's at 80MPH. In my '87 Ford 6. 9, with supposedly 3. 55's (according to the factory sticker on drivers door, I bought it when the truck was 9 years old) and the 3 spd auto with no overdrive, I currently have to go 2900 RPMs to hit 70 MPH! I really hate pushing the old thing that hard, but I just hate going anywhere at 65 MPH and getting passed by Yugo's.

Even still, I will rarely be towing, and so I'll stick with the 3. 54's in my new Ram.

Thanks again,
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

 

[Ethdee]

Tom, that's what a friend of mine runs with his Ford diesel, and he's got 4. 10s in it...


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James
1990 <FONT SIZE="1">Ford</font size> 1/2 ton shortbed 4x4, 351, 4. 10 LSD

[This message has been edited by Ethdee (edited 05-16-2001). ]

 

[KWIKKURT]

The ISB will run for years at redline..... No worries there. .


On a different note: I don't remember the math. But it goes something like this.

Double your HP and the Main / Rod bearing and Piston pin load goes up 20 to 40%

Double your RPM and the Loads go up 40 to 80%

These #'s can be off but that is the general rule.

 

[Todd G]

For my delivery business I used an Isuzu FSR. It's a 2 ton truck with a motor just like ours - 5. 9L, 175 HP. That thing redlined at 3000 rpm and 65 mph. I sold it after 250,000 miles, half of which was at redline. Never did a thing to the motor except change the oil and filters. Of course it was an inline 6 with iron heads, not aluminum. Isuzu can make good motors, just not for GM.
Todd

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1995 Ram 2500,SLT,5-spd,4. 10,std cab,4X4,215 injectors,Banks Powerpack,boost and pyro guages,gutted CAT,33"/16. 5 BFG AT's,Outdoorsman cap,Reese Titan V hitch

 

[SmokinJoe]

Originally posted by Pete Peterson:
Their not like gassers.

Cummins designs the engine for 100% duty cycle. Gasoline engines are NOT even 50% duty cycle...



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2001. 5 QC 2500 White Sport 4x4 LWB ETC 5-Speed Anti-Spin 3. 54 Trailer Tow 241HD SLT+ Tan Leather(Mad Cow Disease) LT265/75R16E ARE Z Series Cap Bedrug ICI Nerfbars

 

[Hale on wheels]

I feel wind resistance is more of a fuel consumption issue than RPM with this motor. When I tow my travel trailer, I usually go about 65mph. In O/D, that is about 1850RPM or so, get about 13mpg, but the power is not there to keep it going up hills, so lately I have switched to 3rd gear at 2500RPM, 65mph, and have been getting the same fuel mileage.

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Cody Hale
01. 5 2500, QC, LB, 4x4,Auto
Gig'em Aggies!

 

[Deezal Man]

Royal,

My Kubota Diesel gen runs at 3600 RPMs, because its a 2 pole gen. It is true, most Diesel gens run at 1800 because the Diesel can handle a 4 pole gen load.

As far as the red line issue, I think common sense will take you a long way here.

I do know that its ok to run a Diesel pulling at red-line, but it is not a wise idea to have the load push it at red-line.

Meaning, keep it out of red-line going down a hill. The gov cannot generate enough hold back to limit the RPMs.

Instead of saying I know... I should say that is what I've heard from guys with extensive Diesel experience. FWIW...

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98. 5' Emerald Green 24v 2500 Auto/3. 54 4x4 SB QC 285. 75. 16's Bridgestone Dueler A/T's on 16" x 8" Alcoa's under Rancho 9000's. Everything but leather. PIAA 1200's, AMSOIL dual filter relocation system, Smittybuilt Stainless Steel Nerfs, Rhino Liner(Junk).

 

[SandDemon]

There was a killer post last week in "Towing" on HP loss vs. Speed. The efficiency loss from 2200 - 2500 rpm is nothing compared to the HP requirement to drive at 80 instead of 70. It's like 40hp! That'll chew up fuel quick.

Jeff

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2001. 5 ETH/DEE 2500 4x4 3. 54 lsd. 33' Weekend Warrior 5er and an army of toys to fill it!
'96 1500 360 3. 90 LSD 3" cat back no muffler! 110,000 and still eating chebbys for lunch!

 

[MCummings]

For me,, 3rd and 4th gear see 3K plus RPM when empty.

My Dad used to tow 70MPH in 4th with the 3. 54/3. 55 gears.

My truck is confusing in the way that. . People here say Dodge has 3. 54 rear-end gears, and under the hood it says 3. 55. Go Figure.

I think redline is as High as the engine should rev. On a diesel I feel that anything over 2700RPMs un-loaded is pushing it, but 3,000RPM's underload is just perfect.

I heard a while back on "here" (the TDR) that Cummins said, anything under 2,600RPM was considered lugging, and Lugging is very harmfull to the ISB Engine.

Mi Dos Cintavos. (My Two Cents)

MerrickNJr

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1998. 5 Dodge 3500, 2wd
5-Speed, Light Driftwood
STRAIGHT PIPED!
3. 55_LSD
A. R. E. Camper w/side pop up windows
Michelin LTX A/T 245/75/16's
Autometer Gaugeworks 3 Gauge A-Pillar Pod
Fuel Pressure (0-15Lbs)
Boost Pressure (0-35Lbs)
EGT Gauge (0-1600*F)
ATS Manifold too!!
My"REAL" Hobby

 

[Utah Willie]

I've 3. 54s and a U. S. Gear O/D that gives me 70 MPH @ 1800 PRM in fifth over. It makes for a real quiet ride (relatively!) and mileage seems to be pretty good when running with just a shell. I agree with the comment about wind, etc. I get very close to the same mileage with my Lance camper on board as I do when towing the Alfa 5er. I think frontal area has a lot to do with straight-away mileage whereas weight will take its toll on the steeps.