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Towing and Hauling Towing and hauling with Ford diesel trucks and vans.

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post #1 of 17 (permalink) Old 02-02-2009, 12:13 PM Thread Starter
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Safe RPMs

I have an 03 6.0, lifted 8' with 22's & 37 toyos(E rated), 4.56 gears. I tow a 40' 5th wheel toyhauler, weighs about 13.5K dry.

My question is, what RPM's should I be running to keep the engine from overworking? I usually tow about 200 miles once a month with it, and my current rpms are at 2500, when doing 55mph(boost is 15 to 20). I have to do 2750 rpms on the grades and will only do about 45 to 50, is this normal? I'm just not used to running 2500 rpms for 4 hrs.

I also had my last oil analysed and the iron content was high, they indicated this was normal in heavy towing vehicles, but how much longer will my engine last at this rate? I currently have 65K miles on it now
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post #2 of 17 (permalink) Old 02-02-2009, 01:41 PM
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I'm just not used to running 2500 rpms for 4 hrs.
2500 RPM's won't hurt it. A lot of PSD's spend their entire life at those or higher RPM. My 97 F-350 SRW ran about 72 MPH at 2500. That's where I drove it most of the time. The duallys had slightly smaller tires than the SRW. I have seen F-350 duallys run 2800 RPM all day.

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post #3 of 17 (permalink) Old 02-02-2009, 10:23 PM
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What 444-4D said.

The '03 6.0L stock engine produces 325 horses at 3,300 RPM. It's a diesel, so it can run at the horsepower peak for hours on end and not hurt a thing but your pocketbook - because it doesn't get great fuel mileage at 3,300 RPM.

Many marine diesel engines are set up to run at near the horsepower peak for days at a time. So I wouldn't worry about it if you are only turning 2,750 RPM. But if you are geared down so you are only making 45 to 50 MPH at 2,750 RPM, then I'd speed up to 3,000 RPM or so and get some decent speed up the mountain.

What RPM should you shoot for? The torque peak is 2,000 RPM, so you never want to cruise at less than 2,000 RPM. About 2,500 RPM should be a good cruising RPM for compromising between torque and HP peaks. But you should be going a lot faster than 55 MPH at 2,500 RPM unless your 4.56 gears are way too short for your needs.





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My Sierra Blanca (Spanish for White Mountain) in the sig pic was a great pickup for 11.5 years. I sold it several years ago. I drove a hand-me-down 2003 F-150 SuperCrew 4.6L 2V for a while, but it was unacceptable for towing more than a rowboat. Replacement is a 2012 F-150 EcoBoost SuperCrew Lariat that tows my 5,000-pound TT like a dream. Replaced the 2012 with a 2019 F-150 3.5L EcoBoost with max tow.
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post #4 of 17 (permalink) Old 02-03-2009, 09:31 AM
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Originally Posted by biofumes View Post
I have an 03 6.0, lifted 8' with 22's & 37 toyos(E rated), 4.56 gears. I tow a 40' 5th wheel toyhauler, weighs about 13.5K dry.

My question is, what RPM's should I be running to keep the engine from overworking? I usually tow about 200 miles once a month with it, and my current rpms are at 2500, when doing 55mph(boost is 15 to 20). I have to do 2750 rpms on the grades and will only do about 45 to 50, is this normal? I'm just not used to running 2500 rpms for 4 hrs.

I also had my last oil analysed and the iron content was high, they indicated this was normal in heavy towing vehicles, but how much longer will my engine last at this rate? I currently have 65K miles on it now
With this set up, I'd recommend you stop goofing around, and get an EGT gauge & learn to drive by it. No hotter than 1250* pre-turbo.

OMC

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post #5 of 17 (permalink) Old 02-03-2009, 12:01 PM Thread Starter
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With this set up, I'd recommend you stop goofing around, and get an EGT gauge & learn to drive by it. No hotter than 1250* pre-turbo.

OMC
EGT gauge is already installed, it never goes over 800*. My concern was having the engine reved up 2700rpms, and from the kind advice I've recieved, it sounds like that can be normal operation.
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post #6 of 17 (permalink) Old 02-03-2009, 01:23 PM
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Where do you have the Exhaust thermocouple installed that you are only getting 800*, before Turbo or after turbo ?

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post #7 of 17 (permalink) Old 02-04-2009, 12:58 AM Thread Starter
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Where do you have the Exhaust thermocouple installed that you are only getting 800*, before Turbo or after turbo ?
After turbo, on the down down pipe. Premix bio 50/50, keeps the temps down, its slower burning, less energy so when it comes out you get cooler, cleaner fumes(biofumes)
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post #8 of 17 (permalink) Old 02-04-2009, 02:16 PM
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After turbo, on the down down pipe. Premix bio 50/50, keeps the temps down, its slower burning, less energy so when it comes out you get cooler, cleaner fumes(biofumes)
I notice my pre turbo egt's are a lot lower when running on B100. I keep a keen eye on the egt's when towing. I also run her up to 3500 rpm's before I shift when going up hills. When climbing hills the motor seems to run stronger above 2500 rpm's. Climbing hills I will see 1150 egt. And that is working her really hard.

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post #9 of 17 (permalink) Old 02-04-2009, 05:11 PM
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After turbo, on the down down pipe. Premix bio 50/50, keeps the temps down, its slower burning, less energy so when it comes out you get cooler, cleaner fumes(biofumes)
with the kind of weight you are towing I would install your EGT gauge pre turbo. You are not getting reliable readings with it post turbo.

1996 F250 4x4 ext. cab, long bed 5 spd. 3.55ls, Tymar Intake, Tymar 4" downpipe and 4" exhaust. AIC, B&W turnoverball, EBPV brake, tranny temp gauge, boost gauge, and egt gauge. 2.5" axle drop bracket, F350 springs up front, and F350 rear axle blocks. 260k miles. RETIRED.

NEW (to me) 2005 F350 FX4 Crewcab shortbed, SRW, Lariat, auto, V10. 5600 lbs front end.
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post #10 of 17 (permalink) Old 02-04-2009, 11:04 PM Thread Starter
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with the kind of weight you are towing I would install your EGT gauge pre turbo. You are not getting reliable readings with it post turbo.
I had it taken to a shop and thats where they installed it, I thought they knew what they were talking about??

I know not to pass 1250* from the downpipe, but what should they not exceed if tapped into the manifold?
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post #11 of 17 (permalink) Old 02-04-2009, 11:08 PM
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Don't pass 1250 from the manifold. Who knows what that would show post turbo? If you're ANYWHERE near 1200 post turbo you've already melted something.

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post #12 of 17 (permalink) Old 02-05-2009, 07:40 AM
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I had it taken to a shop and thats where they installed it, I thought they knew what they were talking about??

I know not to pass 1250* from the downpipe, but what should they not exceed if tapped into the manifold?
Like Mark said. 1250 on the manifold side. Not the downpipe.

1996 F250 4x4 ext. cab, long bed 5 spd. 3.55ls, Tymar Intake, Tymar 4" downpipe and 4" exhaust. AIC, B&W turnoverball, EBPV brake, tranny temp gauge, boost gauge, and egt gauge. 2.5" axle drop bracket, F350 springs up front, and F350 rear axle blocks. 260k miles. RETIRED.

NEW (to me) 2005 F350 FX4 Crewcab shortbed, SRW, Lariat, auto, V10. 5600 lbs front end.
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post #13 of 17 (permalink) Old 02-05-2009, 04:17 PM
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I had it taken to a shop and thats where they installed it, I thought they knew what they were talking about??
Either you misunderstood, or else you have an idiot for a gauge installer.

A thermocouple (sender for a pyrometer or EGT gauge) in the downpipe (which is post turbo) is used only for engine shutdown. It is NOT used for driving. Lots of OTR trucks have a post-turbo pyrometer, but it is used only to tell the driver when it's okay to turn off the key and shut down a hot engine/turbo. The computer program (tune) for the engine prevents too-high EGT when driving.

The computer program that controls your stock engine also won't pump enough fuel to cause too-high EGT. So Ford doesn't provide you with a stock pyrometer. But for driving with a hot-rod tune, you want the thermocouple mounted before the turbo (pre-turbo), either in the exhaust manifold or in the up pipe between the exhaust manifold and the turbo.

Out here in cow country, we have lots of "cowboys" driving hot-rod Pete 18-wheeler cattle haulers. But along with their hot-rod tune, those "good ole boys" all add a pre-turbo pyrometer for driving, because they know their stock post-turbo pyrometer is only for shutting down a hot engine. And if you think a holed piston in your 7.3L engine would be expensive, have you priced a 15-liter Cat lately?

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I know not to pass 1250* from the downpipe, but what should they not exceed if tapped into the manifold?
As others have mentioned, you were misinformed. The 1,250° red line is with a pre-turbo pyrometer. Nobody knows the red line with a post-turbo pyrometer, because it varies so much, affected by several conditions. I've seen my pre-turbo pyrometer over the 1,250° red line while the post-turbo pyrometer was still back at 850°. I've also seen my pre-turbo pyrometer over the red line and at the same time the post-turbo pyrometer was sitting on 1,200°. So what is my post-turbo redline? If I have only one pyrometer, and that one is plumbed after the turbo, then I'd use 850°. Others have said 800° would be safer.

The purpose of a pre-turbo pyrometer is to protect the aluminum pistons from meltdown caused by too-high engine heat. 1,250° EGT is the red line because the melting point of your aluminum alloy pistons is a hair more than 1,250°.

The purpose of a post-turbo pyrometer is to protect the turbo from disastrous high residual heat in the turbo bearings when a hot engine is shut down. Most automotive engineers agree that about 300° to 350° is the maximum shutdown temp, depending on your motor oil. Since I use dino motor oil, I use 300° as my shut-down temp. Synthetic motor oil is not cost effective, so I don't waste my money. But one advantage synthetic has is it can stand a bit more heat without deteriorating. So if you have synthetic motor oil, you can shut down at around 350° EGT.

I have an automagic gizmo that shuts down my engine when the EGT cools off to about 300º. In the meantime, I have the keys in my pocket, the doors locked, the steering wheel and tranny locked, and I'm going on about my business. The gizmo is an ISSPRO Turbo Temp Monitor (TTM), available from any ISSPRO gauge dealer. With my TTM, I don't need a post-turbo pyrometer to tell me when it's safe to shut down the engine.





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My Sierra Blanca (Spanish for White Mountain) in the sig pic was a great pickup for 11.5 years. I sold it several years ago. I drove a hand-me-down 2003 F-150 SuperCrew 4.6L 2V for a while, but it was unacceptable for towing more than a rowboat. Replacement is a 2012 F-150 EcoBoost SuperCrew Lariat that tows my 5,000-pound TT like a dream. Replaced the 2012 with a 2019 F-150 3.5L EcoBoost with max tow.

Last edited by SmokeyWren; 02-05-2009 at 04:38 PM. Reason: typo
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post #14 of 17 (permalink) Old 02-09-2009, 09:14 AM
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well i was always told 900 on post turbo probes, and i have pushed that to 950 for some pretty extended hills, without harm.(on cats and detroits 60 series) has your speedo been corrected that might explain the rpm at 55 indicated. the thing to understand with a post turbo probe is that it will read lower because the turbo has extracted ENERGY from the hot gas. you could assume that regardless of what engine,(6.0, cat cummins detroit) that a "stock" turbo would have a similar efficiency and therefore a similar relationship between the post turbo temp and the actual cylinder temp. definately 800 is pretty safe. my experience with 18 wheelers is that to get from 800 to 900 you really have to work it awfully hard . i.e. peak torque rpms at full throttle and hold it there
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post #15 of 17 (permalink) Old 02-10-2009, 08:07 AM
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well i was always told 900 on post turbo probes, and i have pushed that to 950 for some pretty extended hills, without harm. (on cats and detroits 60 series)
But 950° post turbo could be anywhere from 950° to 1,500° pre-turbo. So you don't have any idea whether you were in danger or not. The experts tell us that 1,250° pre-turbo is the red line, but you cannot use post-turbo EGT to detemine even close to actual pre-turbo EGT.

If your engine had a stock tune, then you were probably okay. But if you had a performance that burned even a smidgen more fuel than stock, then you were courting an expensive disaster.

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my experience with 18 wheelers is that to get from 800 to 900 you really have to work it awfully hard . i.e. peak torque rpms at full throttle and hold it there
Same with a stock PSD. But when someone messes with the tune, the rules all change. With a 100-additional-horse tune on a 7.3L, you can get over 1,300° pre-turbo EGT in a very short climb up a steep grade with a loaded trailer at 2,500 RPM in direct drive. But depending on several exact conditions your post-turbo EGT may be way back down at less than 950°.

(The big-truck engines have a much lower RPM range than our PSDs, so you cannot compare RPM in a C-15 Cat to a 7.3L PSD.)



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