1st Generation Dodge Cummins 89-93 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with Rotary Injection Pumps

How far did you guys go before losing MPG?

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Old 11-25-2009, 12:54 PM
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Default How far did you guys go before losing MPG?

I know there are some mods that increase mpg and some that hurt it. how far did you guys go before you noticed the truck is a little bit more thirsty. what mods helped mpg?
 
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Old 11-25-2009, 02:32 PM
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I get down to about half throttle where mpg starts taking a good hit.

But seriously, the only thing I ever did that really hurt mileage was going to bigger tires. Aggressive AFC mods are going to hurt mileage - smoke screw, loosening the starwheel. Black smoke is unburnt fuel. Bigger injectors certainly won't help.
 
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Old 11-25-2009, 04:25 PM
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In my experience it's not my truck that gets thursty it's my right foot. I've got 221,000 + miles and still see 18 to 19 mpg city and 22 to 23 highway at a steady 65 mph. You can see my mods and numbers in my sig.

Bob
 
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Old 11-25-2009, 08:26 PM
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Originally Posted by NadirPoint
I get down to about half throttle where mpg starts taking a good hit.

But seriously, the only thing I ever did that really hurt mileage was going to bigger tires. Aggressive AFC mods are going to hurt mileage - smoke screw, loosening the starwheel. Black smoke is unburnt fuel. Bigger injectors certainly won't help.
thats balogna.This is always controllable with your foot when you have these mods.bigger injectors(to a point) actually help mpgs with delivering a sharper injection.
 
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Old 11-25-2009, 10:20 PM
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i have bigger injectors, my starwheel is all the way down my fuel pin is ground. i still get 18 city and 20-22 highway, just depends on how bad i get in it my worst tank was16mpg, and that tank had a 4x4 drag race on it and a lot of abuse on the road that week(friend got new chip in his powerstroke and i could still keep up fairly well in the ole girl)
 
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Old 11-26-2009, 08:40 AM
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Originally Posted by stillcummin
thats balogna.This is always controllable with your foot when you have these mods.bigger injectors(to a point) actually help mpgs with delivering a sharper injection.
So, injecting relatively more fuel at any given throttle setting with larger injectors will give better fuel mileage? And better atomization at the same pressure through a larger hole?

Wow, that's amazing! I did not know that!
 
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Old 11-26-2009, 08:48 AM
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If you dont change your pump settings yes its the same amount of fuel,you have a 1st gen,you should know how the VE delivers its fuel.With larger holes Delivery is better.Even when it gets turned up,good nozzles will be more efficient therefore yielding better mpgs.Look at the vw tdi.With just a larger nozzle install you yield 3-5 mpg as well as power!
 

Last edited by stillcummin; 11-26-2009 at 08:50 AM.
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Old 11-26-2009, 08:49 AM
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i still get 23 highway
 
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Old 11-26-2009, 08:58 AM
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Originally Posted by stillcummin
If you dont change your pump settings yes its the same amount of fuel...
I thought the whole reason for bigger injectors was to get more fuel?

---AutoMerged DoublePost---

Originally Posted by hotcummins
i still get 23 highway
Heck, that's nothing! I get 25 on the Internet.
 

Last edited by NadirPoint; 11-26-2009 at 08:58 AM. Reason: Automerged Doublepost
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Old 11-26-2009, 11:43 AM
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Originally Posted by stillcummin
thats balogna.This is always controllable with your foot when you have these mods.bigger injectors(to a point) actually help mpgs with delivering a sharper injection.
i have heard of aftermarket injectors yielding better mpg's but those are some pretty WEAK injectors... like stage one stuff . and the reason they do improve fueling characteristics is b/c you're going from an injector with lord knows how many miles on them to an injector with a fresh set of orfices (man that sounds dirty) spray pattern will be better than a worn out injector. as for same volume of fuel thru larger holes. atomization wont be as good. so you're right a "sharper injection" will be the result but that isnt what we're after

Originally Posted by stillcummin
If you dont change your pump settings yes its the same amount of fuel,you have a 1st gen,you should know how the VE delivers its fuel.With larger holes Delivery is better.Even when it gets turned up,good nozzles will be more efficient therefore yielding better mpgs.Look at the vw tdi.With just a larger nozzle install you yield 3-5 mpg as well as power!
where you see in increase in that situation is from a vehicle being slightly under powered. TO A POINT things like this will help; its a very fine line. if the vehicle has no *** and you hold it open WOT to get somewhere then giving it more fuel and only going half throttle to accelerate at the same rate will more than likely increse your economy.

point is... the amount of fuel that you supply a set of injectors should be tuned to that specific injector. right amount of fuel will yield better atomization and efficiency; too little and efficiency will take a hit. you can MAX out a pump and the pump will only deliver X amount of fuel at X pedal position. easy on the pedal means easy on the fuel mileage. AFC tuning and fuel pin choice has ALOT to do with it all the same. i've actaully cut and ground mine to the point that i probably dont need the smoke screw at all; i'm at one full turn and its still abit much on take off at WOT

---AutoMerged DoublePost---

when you turn up a pump unless you REALLY change some physical parts you're working with a hunk of metal that has design limitations. you arent changing any physical characertistics of the internal parts of the pump (unless its a fuel pin) you're just taking some of the "designed flaws" out of the mix and allowing the pump to operate beyond the factory underpowered settings. so as stated before; before and after turning the full load screw your delivery rate will be the same, until of course you go past the rack travel that the factory settings had you limited at. THEN you'll be delivering more fuel than usual and hurting your economy

---AutoMerged DoublePost---

moral of the story is i talk alot , and economy is easily controlled through how heavy your foot is
 

Last edited by tower_ofpower; 11-26-2009 at 11:43 AM. Reason: Automerged Doublepost
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