Sweet Spot
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Freshman User
Joined: Sep 2017
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Sweet Spot
Hi,
I'm new to the PSD and have some questions.
I have a lot of miles with diesel trucks, 14L to 5.9L and they all have a RPM sweet spot where they are the "happiest".
Where are the 2017 6.7L PSD's the "happiest" in the RPM range?
TIA
I'm new to the PSD and have some questions.
I have a lot of miles with diesel trucks, 14L to 5.9L and they all have a RPM sweet spot where they are the "happiest".
Where are the 2017 6.7L PSD's the "happiest" in the RPM range?
TIA
Hotshot
Joined: Oct 2015
Posts: 19,695
Likes: 12,821
From: Wyoming
1800 RPM is max torque. There is a thread in the 2017+ subforum where a member calculated out RPM for each gear ratio. I think this is the thread: https://www.ford-trucks.com/forums/1...at-70-mph.html. See post #10.
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Freshman User
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1800 RPM is max torque. There is a thread in the 2017+ subforum where a member calculated out RPM for each gear ratio. I think this is the thread: https://www.ford-trucks.com/forums/1...at-70-mph.html. See post #10.
This is me:4.10 axle is turning 2051 RPM according to the math on that thread. Does the PSD like to run at max torque consistently? I've been dropped on my head several times so mafs is hard for me.
Lead Driver
Joined: Nov 2005
Posts: 5,225
Likes: 4,239
From: Kaysville Utah
Computer seems to find the right gear for me. With over 150,000 miles on my 2011 truck and 80,000 miles on my current 2015, I can't tell you that I've found an rpm that my truck hated.
I'm not sure what sweet spot you are looking for. Are you looking for best fuel mileage or best coolant/oil temps? These engines seem to lug along at 1500 -1600 rpm on interstate roads with almost no effort.
I'm not sure what sweet spot you are looking for. Are you looking for best fuel mileage or best coolant/oil temps? These engines seem to lug along at 1500 -1600 rpm on interstate roads with almost no effort.
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Freshman User
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Computer seems to find the right gear for me. With over 150,000 miles on my 2011 truck and 80,000 miles on my current 2015, I can't tell you that I've found an rpm that my truck hated.
I'm not sure what sweet spot you are looking for. Are you looking for best fuel mileage or best coolant/oil temps? These engines seem to lug along at 1500 -1600 rpm on interstate roads with almost no effort.
I'm not sure what sweet spot you are looking for. Are you looking for best fuel mileage or best coolant/oil temps? These engines seem to lug along at 1500 -1600 rpm on interstate roads with almost no effort.
I am looking for the spot that satisfies the most parameters you mentioned. Everyone wants the fuel milage but road and atmospheric conditions play a role in fuel economy that are out of our control. What you are hauling or towing obviously impacts fuel economy. My understanding is the driver is responsible for about 35% of fuel economy. For that reason I use the cruise as much as I possibly can.
I totally agree with you. I have not found any road conditions that cause any effort for this motor at all loaded or empty.
It's good to know that there is no particular rpm to avoid/that is hated.
Post Fiend
Joined: Nov 2001
Posts: 6,748
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From: Tallassee, ALabama
I don't look at rpm but the mph I seem to have the best all around performance is 62-65mph. I have 3.73 gears, so this puts it around 1800 rpm. Also, the tires on my travel trailer are only rated at 65mph as safe.
Bee surprised how many times the same people will pass you on a long haul multiple times when you are loping along at 62-65mph.
Bee surprised how many times the same people will pass you on a long haul multiple times when you are loping along at 62-65mph.
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I don't look at rpm but the mph I seem to have the best all around performance is 62-65mph. I have 3.73 gears, so this puts it around 1800 rpm. Also, the tires on my travel trailer are only rated at 65mph as safe.
Bee surprised how many times the same people will pass you on a long haul multiple times when you are loping along at 62-65mph.
Bee surprised how many times the same people will pass you on a long haul multiple times when you are loping along at 62-65mph.
I used to subscribe to the gear fast run slow theory and it worked very well for me but even with the 4.10's on 17's below 65 "feels" like I'm lugging it a bit.
Running 70 on the flat without much wind I was seeing 12.9 with a TC and about 2050 to 2075 RPM but that's just looking at the dash tach. I didn't pull out the torque program and get a digital read on the rpm.
No, I wouldn't be surprised at all. Steady and smooth equals fast. Hammering on it from rest stop to fuel stop to food stop makes exactly no time.
Good on ya for keeping the speed down on those trailer tires. Too fast is too dangerous and you can end up peeling part of the trailer side off if it's not a flat bed.
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Lead Driver
Joined: Nov 2005
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From: Kaysville Utah
Mine have been SRW with 3.55 rear ends and they seem to run just fine in the 1600-1800 rpm range. Climbing mountains or during exhaust braking I'll see rpms in the high 2000's But most driving, with or with out a trailer is 1600-1800
Post Fiend
Joined: Nov 2001
Posts: 6,748
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From: Tallassee, ALabama
1800 ok. That's peak torque. Are you on 17's or what?
I used to subscribe to the gear fast run slow theory and it worked very well for me but even with the 4.10's on 17's below 65 "feels" like I'm lugging it a bit.
Running 70 on the flat without much wind I was seeing 12.9 with a TC and about 2050 to 2075 RPM but that's just looking at the dash tach. I didn't pull out the torque program and get a digital read on the rpm.
No, I wouldn't be surprised at all. Steady and smooth equals fast. Hammering on it from rest stop to fuel stop to food stop makes exactly no time.
Good on ya for keeping the speed down on those trailer tires. Too fast is too dangerous and you can end up peeling part of the trailer side off if it's not a flat bed.
I used to subscribe to the gear fast run slow theory and it worked very well for me but even with the 4.10's on 17's below 65 "feels" like I'm lugging it a bit.
Running 70 on the flat without much wind I was seeing 12.9 with a TC and about 2050 to 2075 RPM but that's just looking at the dash tach. I didn't pull out the torque program and get a digital read on the rpm.
No, I wouldn't be surprised at all. Steady and smooth equals fast. Hammering on it from rest stop to fuel stop to food stop makes exactly no time.
Good on ya for keeping the speed down on those trailer tires. Too fast is too dangerous and you can end up peeling part of the trailer side off if it's not a flat bed.
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Freshman User
Joined: Sep 2017
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Ok that helps. Thank you all for your input. Sounds like 1700 to 1800 rpm is the sweet spot.
Thanks again.
Anything else I should know about these PSD's? Other than good fuel and LOF?
Thanks again.
Anything else I should know about these PSD's? Other than good fuel and LOF?
Senior User
Joined: Aug 2016
Posts: 164
Likes: 1
From: Olympia, WA
That 1600pm range does indeed appear to be the happy place. I have the taller 3.31 gears (18" rims) and I find I am always right someplace in between 1600 to 1750. It's a good cruise pace with our without the trailer. Even with hills there is no gear hunt, usually not until it become a 3% or more grade.
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Freshman User
Joined: Sep 2017
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That 1600pm range does indeed appear to be the happy place. I have the taller 3.31 gears (18" rims) and I find I am always right someplace in between 1600 to 1750. It's a good cruise pace with our without the trailer. Even with hills there is no gear hunt, usually not until it become a 3% or more grade.
I haven't seen the truck hunt for gears yet. Haven't had it break a sweat loaded or empty.
Laughing Gas
Joined: Feb 2007
Posts: 950
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From: Waco, Texas
I think I can relate to what you are calling the "sweet spot". Pulling our 12k fiver, it is right at that 65 mph in T/H which is right at 1650 RPM, 70mph is ok at 1775 rpm. Empty, that 70-75 Mph is great and also pretty easy driving. And the RPMs are the same empty as pulling so really not much difference as you barely know you have anything behind you when pulling anyway.
Senior User
Joined: Jan 2013
Posts: 238
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From: Northern New Mexico
That 1600pm range does indeed appear to be the happy place. I have the taller 3.31 gears (18" rims) and I find I am always right someplace in between 1600 to 1750. It's a good cruise pace with our without the trailer. Even with hills there is no gear hunt, usually not until it become a 3% or more grade.