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20% larger "hole" or opening in the nozzle at the same fuel pressure will yield a 20% larger flow of fuel. The problem is that unless you can change the duty cycle so that the injector is running less open time when out of the boost, then you will be running 20% more fuel all of the time. The PCM or computers on most gas cars use the O2 sensor to read the AF mixture and adjust the timing on the injectors so that they don't run too rich. The diesel does not use anything like this and I believe cannot correct the on time of the injectors to compensate for the added fuel in a low demand situation like low load. If they do, then it would have to be based on boost pressure and air flow alone with no way to know that the injectors are larger. Someone in the know, let me know how the PCM would correct for a 20 % larger constant flow from the injectors and keep the engine from running too much towards the rich side all of the time.


Jess
 

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jesshd said:
20% larger "hole" or opening in the nozzle at the same fuel pressure will yield a 20% larger flow of fuel. The problem is that unless you can change the duty cycle so that the injector is running less open time when out of the boost, then you will be running 20% more fuel all of the time. The PCM or computers on most gas cars use the O2 sensor to read the AF mixture and adjust the timing on the injectors so that they don't run too rich. The diesel does not use anything like this and I believe cannot correct the on time of the injectors to compensate for the added fuel in a low demand situation like low load. If they do, then it would have to be based on boost pressure and air flow alone with no way to know that the injectors are larger. Someone in the know, let me know how the PCM would correct for a 20 % larger constant flow from the injectors and keep the engine from running too much towards the rich side all of the time.


Jess




The turbo will make up for the added fuel just like it does with a box installed. The difference is, that all calculations will be skewed by 20% much like (but not the same in the leak dept) running a pressure box that skews 100% of the time.





The one thing that I hear from those running injectors is it gets to sound like the pilot injection is shut off when under load.





I'll also add that the Bosch/GM needles are "coated" which should help them have a happy life. We've been playing with the dissection of many injectors, and it seems (contrary to popular and MY belief) that the nozzle isn't wearing as much as we first thought. It seems the body cracking thing is more common...
 

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Discussion Starter · #23 ·
20% larger "hole" or opening in the nozzle at the same fuel pressure will yield a 20% larger flow of fuel. The problem is that unless you can change the duty cycle so that the injector is running less open time when out of the boost, then you will be running 20% more fuel all of the time. The PCM or computers on most gas cars use the O2 sensor to read the AF mixture and adjust the timing on the injectors so that they don't run too rich. The diesel does not use anything like this and I believe cannot correct the on time of the injectors to compensate for the added fuel in a low demand situation like low load. If they do, then it would have to be based on boost pressure and air flow alone with no way to know that the injectors are larger. Someone in the know, let me know how the PCM would correct for a 20 % larger constant flow from the injectors and keep the engine from running too much towards the rich side all of the time.

You can have larger injectors without having excess fuel. When driving down the road it takes X amount of fuel to move the truck. Now if you are putting more fuel in do to larger injectors then the computer will see this and the fuel management system to cut back which in turn gives you the same amount of fuel as before. Now when the throttle is wide open you will see the effects of the larger injectors. These will work fine and I am sure those that try them will see.

JK
As far as Bosch nozzles with soft seats I never did buy that. They know how to make nozzles and it was dirt doing the damage. These Boiso nozzles are coated as well.


Greg
 

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What's the big trick to installing a set of injectors. How far apart does the intake system have to come apart? I understand that it's a big job but I can't imagine that it would be too hard to do. The heads don't have to come off do they. Are there special tools needed? Sometimes these jobs can get bigger than life. Everyone talked about an engine swap on my last class A motorhome like it was vodoo or something and all it really was was a bunch of work.
 

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Soon as they are ready, so am I...
 

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Kennedy:


Your the man I hear! My buddy Kevin Bowes at River Road Auto and Truck repair raves about your stuff. I have all the mods on my truck as you show on your website. (well, not ALL the mods)


Maybe you can answer this, 03' Dmax with 33,000 miles.


Very hard starting, when it does finally start, truck has no power loss, has no other problems, and has no problems smoking (the competition or the tires).


Taking to dealer for diagnosis. Hopefully not injectors.


Thanks Kennedy,


TommJr, Hudson-Prescott WI
 

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NOW I remember why I liked caruretors so much.
You could rebuild them yourself.
They gave massive low end power (you punched it and it moved). I remember the first injected car I drove. I thought to my self my God its flat.
 

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Wickedsprint said:
You probably drove a crappy injected car, that statement is a bit vague PC.

I have to agree!


I had the old Corvette Rochester Injection on a 350HP 327CI in a 57 chevy when I was in the Marines (1966-70) and it out ran every carbuarted thing I ran on that car and I got up to 17mpg with a 370 rear.


2DAMAX
 

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I hate to burst any ones bubble but, the PCM willnot correct for larger injectors, period! There is no feedback like there is in a gas motor. Fuel is delivered based on throttle position, engine rpm and air flow. From this the computer looks up a fixed pulse width and delivers it. The turbo willnot make up the difference. Take a look at the wastegate on your truck, there is no computer control. Once boost reaches a predetermind level it opens. Add-on boxes, both pressure and pulse width and PCM reprograms donot add fuel at light load and idle conditions as the 20% larger injectors will do. Someone needs to do there homework before opening their mouth!


You may get away with 20% more fuel but until they have been tested I wouldnot give out false and misleading information. The reason the pilot injection gets screwed up is too much fuel is delivered during pilot time. This is all something that can be fixed in computer reprogramming but without doing that you've increased flow 20% at all times and that's not a good thing. Above 50% throttle they will mostlikely work fine and make more Hp but at lower throttle angle you may get excessive smoke and loss of mileage.
 

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Edited by: sdaver
 

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"Above 50% throttle they will mostlikely work fine and make more Hp but at lower throttle angle you may get excessive smoke and loss of mileage."

Purfect !!!!!!! Bring on the NOS .....

Mac
 

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Mackin said:
"Above 50% throttle they will mostlikely work fine and make more Hp but at lower throttle angle you may get excessive smoke and loss of mileage."

Purfect !!!!!!! Bring on the NOS .....

Mac

I thought there was only two throttle positions to use, 50% and 100%
 

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Joey D said:
Mackin said:
"Above 50% throttle they will mostlikely work fine and make more Hp but at lower throttle angle you may get excessive smoke and loss of mileage."

Purfect !!!!!!! Bring on the NOS .....

Mac

I thought there was only two throttle positions to use, 50% and 100%
Pretty much !!!!!! Just give me an idle speed too !!!!!

Mac
 

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I did not see how the PCM could make up for the extra fuel without some sort of closed loop feedback sensor. Since there is no AFM or O2 sensor on a diesel, then it would make sense that the PCM is using a fixed timing and fuel map to regulate the fuel injected. There are only two ways to get more fuel into the engine on an injected motor. Either raise the rail pressure to increase the amount of fuel squirted through the same size hole, or increase the size of the hole. If there was a way to put a variable fuel pressure regulator on that could sense vacuum and boost, then it would be possible to use the "stock" fuel flow at low demand, and then let the boost pressure to the variable raise the rail pressure as boost increases. This was a popular way to get more fuel into gassers when installing an aftermarket turbo kit. The problem was that it did not regulate well enough. You would probably have to have Quad, TTS, Juice, or some company that has visibility to the maps in the PCM program the fuel maps to take advantage of the higher rates of fuel flow and adjust the injectors for a 20 % lower duty cycle at times of less demand and off boost running. It really is not just as simple as sticking in bigger injectors without adjusting the timing and fuel maps to compensate for the larger fuel flow. It will smoke more and run richer all of the time and hurt fuel economy and off boost response unless to you can get into the maps and recurve them to take advantage of the larger injectors both on boost and off boost. Someday very soon someone will come up with a program and interface that allows visibility to the stock fuel and timing maps. Then you will be able to see what the aftermarket programmers are doing to the maps. Until someone either makes a read only program that can do this, or one of the aftermarket tuners comes out with a program or box that will let us program our own timing and fuel maps, we are just guessing at best. The only ones that really know what the maps are doing are the programmers like Quad, Edge and Diablo. It would be very very interesting to know what they use to get access to the maps and how they decide on what to change. I for one am used to the gassers that allow full access and visibility to the maps. Then you are not just taking someones word for whether or not the programming is "right". It would be very easy to compare the fuel and timing maps from one programmer to the other, say the Predator to the Juice, and see why one runs hotter and the other does not. It is still just a matter of more or less timing vs more or less fuel at certain vacuum and boost conditions. There is not any rocket science, other than no ignition parts to worry about. More timing and more fuel mean more power. The "art" is knowing when to apply and how to apply to get the most power at the safest levels without creating any drivability issues.


Jess
 
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