injector pump setting
Thread Starter
|
Hotshot
Joined: Feb 2004
Posts: 11,697
Likes: 3
From: Marengo, Iowa
injector pump setting
Just a question, I figure I alreaday know the answer, but just want to confirm. My 86 250 6.9 4 speed 4.10 rear tows best at 65 mph, this speed has been verified to be right (both good and bad ways!) the max on it is 75. If I tow below 65, it pulls down pretty hard, but if I maintain 65(hard to do on some roads, those pesky guys with the blue lights don't think I should be doing that!
) it pulls great. Is this a matter of the way the IP is set up? It seems odd to me to build it's best power so close to max rpm. It smokes fairly hard at the lower speeds on hills with a load, but not so when it's running faster.
) it pulls great. Is this a matter of the way the IP is set up? It seems odd to me to build it's best power so close to max rpm. It smokes fairly hard at the lower speeds on hills with a load, but not so when it's running faster.
Posting Guru
Joined: Jul 2004
Posts: 1,627
Likes: 0
From: West Valley Utah
It's not only the IP but a combination of gearing, timing, cam, IP setup, even tires play a role in where peak torque/rpm is at and one of the reasons big trucks have lots of gears.
The 80's diesel pickups played to a small crowd and as you can tell they really were not thought out all that well as far as performance goes. When I say performance I mean to be used as a hauler, not how fast it'll go. When the 6.9's are setup right they are a real power house that can get very good fuel milage without having high egt's.
The 80's diesel pickups played to a small crowd and as you can tell they really were not thought out all that well as far as performance goes. When I say performance I mean to be used as a hauler, not how fast it'll go. When the 6.9's are setup right they are a real power house that can get very good fuel milage without having high egt's.
Thread Starter
|
Hotshot
Joined: Feb 2004
Posts: 11,697
Likes: 3
From: Marengo, Iowa
I'm not worried about going fast, but there are occasions I need to go slower and still have enough power to pull. Having a lower gearset like that I expected more power slower, not faster. If that stood for reason, then 3.55 should have their best power closer to 70-75.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
The torque is max close to 1900 RPM
The HP is max around 3100 RPM
So where you are at with your gears is to fast for max torque, to slow for max HP.
All the tires and gears do is move the speed that these occur at around on the speedometer.
With my 3.55's and 33" tires my two best pulling speeds are 52 and 85, that is 1900 and 3100 RPM.
You should have yours at 42 and 69 if you run 31" tires.
From my big truck days there is another factor in why it seems to pull better at higher speeds, momentum plays a big part in how well you pull a hill untill you get to hills way bigger than you have in Iowa.
From those days I do remember that the guys with blue lights have no sense of humor in Iowa, even less in Missouri. But that is kinda how they are everywhere else as well.
The HP is max around 3100 RPM
So where you are at with your gears is to fast for max torque, to slow for max HP.
All the tires and gears do is move the speed that these occur at around on the speedometer.
With my 3.55's and 33" tires my two best pulling speeds are 52 and 85, that is 1900 and 3100 RPM.
You should have yours at 42 and 69 if you run 31" tires.
From my big truck days there is another factor in why it seems to pull better at higher speeds, momentum plays a big part in how well you pull a hill untill you get to hills way bigger than you have in Iowa.
From those days I do remember that the guys with blue lights have no sense of humor in Iowa, even less in Missouri. But that is kinda how they are everywhere else as well.
Thread Starter
|
Hotshot
Joined: Feb 2004
Posts: 11,697
Likes: 3
From: Marengo, Iowa
that would make sense. I only run 30 " (I think, 9.50r 16.5, same as 245/75/r16) Someone before me apparently recalibrated everything, because the speedo is dead on. We do have some pretty good hills, but nothing compared to the hills you would deal with Dave. I do realize that the gears don't determine power, just the rpms that relate to the ground speed. The lower gearset makes it better for pulling, in that it gets to the best power sooner, is all.
