Top R.P.M's for a D21

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

Moderators: plenzen, Nissan_Ranger

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Highway Man
Posts: 46
Joined: 4 years ago
Location: Hillman West Australia

Top R.P.M's for a D21

#1

Post by Highway Man » 4 years ago

Evening Chaps,

As you all know by now, I have a 1987 D21, powered by the "Almighty SD-25", better known as the, "Eight Wonder of the World", {Pause for the Bow}, but i do really have a pressing question,
please!

Can any of you People in the know, tell me the "Red Line" of this "Screaming Beast", The Owners Manual states she will Idle at "600 R.P.M." If she is in the mood and purrs at this,
But, I have no idea what she is doing in the Dark, and I have no Rev Counter to keep her in check,

Now I know quite well I can go down to our local "Drag Track" and give Her, her Head but wouldn't want to embarrass anyone who rose to my Challenge, so I thought I would ask you Dudes
if you could help me!

Best Regards,

Highway Man!

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: Top R.P.M's for a D21

#2

Post by waynosworld » 4 years ago

My SD25s don't like it above 3000rpms, fact is that I shift around 2600rpms, but on the hiway in 5th gear I have run it up to 3200rpms for a little while, normally I don't go above 3000rpms.
I even have a turbocharger on one of my SD25 engines, it don't act any different, above 3000rpms in any gear other than 5th sounds over revved, I do have tachometers in all my diesel trucks.

Highway Man wrote:Evening Chaps,

As you all know by now, I have a 1987 D21, powered by the "Almighty SD-25", better known as the, "Eight Wonder of the World", {Pause for the Bow}, but i do really have a pressing question,
please!

Can any of you People in the know, tell me the "Red Line" of this "Screaming Beast", The Owners Manual states she will Idle at "600 R.P.M." If she is in the mood and purrs at this,
But, I have no idea what she is doing in the Dark, and I have no Rev Counter to keep her in check,

Now I know quite well I can go down to our local "Drag Track" and give Her, her Head but wouldn't want to embarrass anyone who rose to my Challenge, so I thought I would ask you Dudes
if you could help me!

Best Regards,

Highway Man!
I know the voices are not real,
but they have some really good ideas.

Highway Man
Posts: 46
Joined: 4 years ago
Location: Hillman West Australia

Re: Top R.P.M's for a D21

#3

Post by Highway Man » 4 years ago

Hello again Waynosworld!

I travel most times at around 75 to 80 Kilometres an hour as this is my top for Fuel Consumption, and she burns no Oil either, and with no Tacko I rather guess she is traveling at about
2700 Revs by sound alone, and this I like, I don't like her at 95 Klm's to 100 Klm's as she feels uncomfortable too me and sounds a bit like a "Banshee", but I have no way of checking this,
Hence my question to the Forum!

Thanks again,

highway man!

plenzen
Posts: 868
Joined: 13 years ago
Location: Cochrane Alberta Canada

Re: Top R.P.M's for a D21

#4

Post by plenzen » 4 years ago

Mine too seems to enjoy the 90 km/h speed. I can have a look in my FSM to see what the max rpms are but seems to (back in the day) we used to set throttle stop at 3800 and I think the governor will stop it at 4 -4200. (Those were SD22'S but pretty much same beastie)
There is a hill coming out of town that it will not pull in 4th. I put my flashers on and keep to the right lane (left lane for you "left is right" types) and hold it at 60kph in 3rd. I can run it near to 80kph but fear oil pan failure at that rpm. The rest of the world can just go around me.
I drive mine pretty much the same as Wayne does.
I wish I had about 5lbs of boost and it would pull that hill in 4th I'm pretty sure. The EGT to do it may not be worth it though and with near 400,000 km on it now It's not worth it.
IMO that is.
I also live at 4700 ft as well. That has more to do with it I believe.
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

Highway Man
Posts: 46
Joined: 4 years ago
Location: Hillman West Australia

Re: Top R.P.M's for a D21

#5

Post by Highway Man » 4 years ago

Today I will be checking out Her Water catchment filter as i am nearing this Maintenance Period and then She gets a coat of paint and a quick visit to the local Weighbridge to check out
Her "Tare and Aggravate" so I can fix her new Stickers on the Door, as i have fitted a Toolbox on the Tray Permanently along with a Genset for cutting metal to be collected!

I have also made up and fitted a Fuel Tube just behind the Drivers Door to read the Fuel Tank contents without unloading the Batteries and other "Scrap Metal" to read my Dipstick so as
to be certain of my Fuel on board,{something i didnt think of when i placed my dipstick in the tank}, you see, I have a lot of trouble with my legs and find it most troublesome to get up on
the Tray to dip the tank, but i am slowly working my way through these little "Hick.ups" i find from time to time! :oops:

I will try and put a New Photo' on the Forum on Her completion, Oh, as a matter of interest, I live 4 feet above Sea level and collect Scrap generally at 2500Ft above this while collecting the
Scrap Metal in our Rural Area's, with a round trip at around 550 to 650 Kilometers, on both Bitumen and Gravel Roads as well and camping out among the little "Goannas and the bigger
"Bungarrows" as well, but at a definite distance, that's for sure, :shock: My Wife says I have no pride in who's company I keep, Snakes are not a real problem as I am a lousy Cook, and we only have three deadly types in Western Australia, The Brown Snake, The Tiger Snake, and the Dugite Snake,

Well, the Sun is up so I might as well get started on this days work after two weeks of solid rain, :(
all the best too both of you!

highway Man.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: Top R.P.M's for a D21

#6

Post by waynosworld » 4 years ago

I am a speed demon compared to you guys, I get in my vehicles to get where I am going, not to sight-see, I am focused on my driving, even though I scoot along, I get the best mileage with the diesels, as my gas rigs get terrible mileage the way I drive.
OK, when I am on the hiway I drive 75/80mph(120 to 130kph), this is about 3000rpms at 128.7kph with 14 inch tires, I only do this in 5th gear, all the other gears I shift around 2400/2600rpms which is the beginning of sounding over revved, from the sounds of it the rest of you are revving the engine to maybe 2500rpms max, if I could drive 50/55mph(80/90kph) I would be turning around 2000rpms, and I would get around 36mpg, I have done this, but it drove me crazy, so on the way back home I drove normally and got around 28/29mpg which I can live with as I am not tense with this speed like I am when driving slow.
Another thing is that I am turning 3.50 gears in the rear of the 521kc diesel while the stock gears are 3.89(3.90) for the US 720 diesel trucks, I am turning 3.30 gears in the turbodiesel, and if there were such a thing as 3.08 gears for a H190 I could easily turn them, as I have a lot of torque with this turbodiesel setup.
If you want a tachometer for your diesel, this is the one I like, it has worked flawlessly since I installed it.
http://www.googleadservices.com/pagead/ ... IIw&adurl=
I know the voices are not real,
but they have some really good ideas.

plenzen
Posts: 868
Joined: 13 years ago
Location: Cochrane Alberta Canada

Re: Top R.P.M's for a D21

#7

Post by plenzen » 4 years ago

"My Wife says I have no pride in who's company I keep"
Hmmm.....
She realizes you come home from time to time yes ?? :wink:

Wayne
You have to slow down and smell the roses buddy. Take your time, relax, it will still be there when you get there. :)

What kind of pickup does that tach use? Do you have to get into the alternator or is there something you put on the balancer ?
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: Top R.P.M's for a D21

#8

Post by waynosworld » 4 years ago

plenzen wrote:"My Wife says I have no pride in who's company I keep"
Hmmm.....
She realizes you come home from time to time yes ?? :wink:

Wayne
You have to slow down and smell the roses buddy. Take your time, relax, it will still be there when you get there. :)

What kind of pickup does that tach use? Do you have to get into the alternator or is there something you put on the balancer ?

You have to glue magnets on the balancer, and mount the sensor to one of the front cover bolts, it works really well once set up properly.
I have a "tinytach" on the turbodiesel, but I don't like it very much, it goes to total hours when I let off the pedal, I don't like that and the manufacturer won't fix/replace it, I am fairly sure they know the issue, I will not buy another one, my first one worked great though, wish I had kept that one, but it went with that truck when I sold it.
I know the voices are not real,
but they have some really good ideas.

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