12 Valve 2nd Gen Dodge Cummins 94-98 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with P7100 Injection Pumps

Stock RPMs?

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Old Sep 27, 2009 | 05:13 PM
  #11  
Hammer's Avatar
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Ok....
I have asked this in many places and feel its time it gets asked here for you newbies...

What do you feel your going to gain by spinning your truck over 3000rpm?...

Many of us have seen what these motors do powerwise above 3k and there is really not alot of benefit in RPM's above 3k.In fact,the 12v motors powerband drops like a brick the further above 2700 rpm you go.So I am curious to find why guys think they need the big rpm load with nothing more than a stock motor.......Andy
 
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Old Sep 27, 2009 | 06:32 PM
  #12  
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if i had an auto the first thing i would have done was get a 3k gsk dodge autos dont shift until the pump is already defueling and its a major pain but 4k isnt really needed unless you want to hook coming off the line with the biggest rs you can is a big help i saw a huge differenec when i was pulling trailers being able to wind the gears out was a big help
 
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Old Sep 27, 2009 | 07:24 PM
  #13  
94 12valve's Avatar
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andy the advantage of a 4k is it fuels way harder down low and pulls better up to 3k than a 3k gsk will and that alone in enough reason for the 4k kit. you are right on the power droping like a brick and that is mainly due to your head/cam/turbo set up.
 
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Old Sep 27, 2009 | 07:29 PM
  #14  
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4k GSK here..... mine pops when the valves lift and i just dont run it above 3400..... but i have the springs just too lazy to install..... next week since the new manual vb billet trans just went in!!
 
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Old Sep 28, 2009 | 12:09 AM
  #15  
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The 3k and 4k kits fuel exactly the same down low,I have seen that on a test stand with my pumps.I agree with the comment about head,cam,turbo application killing power up top but realistically valve float kills more than them.

You will hear many people say "I need the rpm for wheel speed when pulling" and to that I say BS.You may need the rpm to get the sled moving but proper gear/tire diameter selection will keep the motor in its happy rpm range and have you making power where the pump and motor are the most efficent.

A properly set up pump with 3k springs would be what most of the average street driven trucks would need as there is no need for RPM's above 3k anyway IMO.I have done extensive work on my street combo and can tell you that anything above 3k is wasted energy.The dyno sheets show that mine is really happy and making the best power at 2700 and I do have springs that can go way more than that.

The reason I asked this was to the novice owner many think that they need the bigger spring set up for power without ever having seen what their trucks want for power.There is more to tuning than reading the forums and deciding a 4k kit and a "100 plate" is the best choice.Not all pumps are the same,nor are the motors and even though they are the same basic engine each one will have its own needs and they may be all a tad different.
 
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Old Sep 28, 2009 | 12:23 AM
  #16  
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very well said powerplants are just like rifles every one needs there own load worked up you can have the same cal. same make with the same conditions and they are very rarely ever the same might be close but that dont quite cut it
 
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Old Sep 28, 2009 | 08:14 AM
  #17  
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sorry it took me so long to get back to ya dan33 but it doesnt have any kit on it? other than waht i have done to it its totally stock. the farm i work for bought it new and they are to damn stupid to know how to do anything like that.besides they dont beleive in doing anything to upgrade. hell they hardly do maintanance on their vehichles. now ive got it and the only thing ive done to the pump is crank the star wheel.
 
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Old Sep 28, 2009 | 03:47 PM
  #18  
94 12valve's Avatar
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Originally Posted by Hammer
The 3k and 4k kits fuel exactly the same down low,I have seen that on a test stand with my pumps.I agree with the comment about head,cam,turbo application killing power up top but realistically valve float kills more than them.

You will hear many people say "I need the rpm for wheel speed when pulling" and to that I say BS.You may need the rpm to get the sled moving but proper gear/tire diameter selection will keep the motor in its happy rpm range and have you making power where the pump and motor are the most efficent.

A properly set up pump with 3k springs would be what most of the average street driven trucks would need as there is no need for RPM's above 3k anyway IMO.I have done extensive work on my street combo and can tell you that anything above 3k is wasted energy.The dyno sheets show that mine is really happy and making the best power at 2700 and I do have springs that can go way more than that.

The reason I asked this was to the novice owner many think that they need the bigger spring set up for power without ever having seen what their trucks want for power.There is more to tuning than reading the forums and deciding a 4k kit and a "100 plate" is the best choice.Not all pumps are the same,nor are the motors and even though they are the same basic engine each one will have its own needs and they may be all a tad different.
there was a night and day difference when Iwent to a 4k fro a 3k.

as for your pulling comment if both of our trucks have the same gearing and same size tire your truck at 3k and mine at 4k, I'll bet I go further than you. I have also been told that while pulling you want to keep the motor away from your peak torque because that is where you will break the most driveline parts.
 
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Old Sep 28, 2009 | 07:10 PM
  #19  
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Again...
On a test stand,I have seen zero difference in the low end fueling between the two kits,up top yes,down low nope.I was not chatting about what guys do when the pump is done on the truck.

As for pulling...
A properly set up pump with 3k's and the right gear/tie selection and I would bet any money they could not only run with you but give you a fit.I also said nothing about running the truck at where max torque is made.Torque is what gets the sled rolling,but running at a rpm where your making the most efficent use of your available power is what creates distance.

When a truck makes max power like yours at around 3000 and drops like a stone from there out,why would you even try to run up where it makes no power or like in yoiur case,looses almost 200hp.You would want the right tire and gear selection to keep the motor happy and around 3k to maximize the distance.If you had a tighter charger then the powerband would move down a bit and make the combo even better.
 
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Old Sep 28, 2009 | 08:10 PM
  #20  
94 12valve's Avatar
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when you run more rpms in a pull you can also run a bigger charger helping your power band above 3k

I'm not gonna start an online pissing contest if you wanna hook to a sled and prove me wrong be my guest but I'll stick with my rpms.

and fyi I lost under 50 hp when I was above 3k before the gov springs defueled the pump if I had them tighter I would have lost less.
 
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