Detuning large injector nozzles - How to pick injector size for upgrades!

This is a topic that I have battled with since I began tuning 7.3 liter PowerStrokes. At some point, someone posted online that you can have large 100 % - 200 % nozzles while maintaining the ability to tow heavy simply by having your tuner “detune” the truck. What I am frequently encountering, people believe that “detune” means we can adjust the rate of flow & atomization of fuel down to that of a stock nozzle. I can’t. No tuner can. If they tell you that they can, they are simply full of ****.

The easiest way I can explain this within an example is to compare a stage two - 180cc / 100 % against the characteristics of a Stage 1 – 180cc / 0 %.

The injector pulsewidth (PW) is a measurement for how long the injector is spraying fuel into the cylinder. Our goal as tuners is to match the desired pulsewidth duration to the depletion rate of the injector. Depletion rate is the amount of time it takes to empty the entire displacement of the injector.

A Stage 2 – 180cc / 100 % injector, it is capable of spraying all 180cc of fuel in an injection window of just 2.6 ms PW.
A Stage 1 – 180cc / 0 % injector, it is capable of injecting all 180 cc of fuel at 3.5 ms PW.

As a general statement, the amount of power your truck is capable for has to do with the amount of fuel injected. So if you are able to inject 180cc of fuel, you will have around 380 - 420 rwhp out of a tune which fully depletes the injector. I know someone will say “but a Stage 2 builds more power”, and they would not be incorrect. But what people do not pay attention to is the amount of torque you sacrifice to build that little bit of extra power.

For those that do not know where hp / torque comes from in relation to the injection cycle, I will try to briefly explain it so we can move on to the next point.
As the piston raises, the fuel will start injecting pre-top dead center (TDC). This is your measurement for timing advance. As the piston crosses the point for TDC, the explosion of energy that bursts the piston downward is where your horse power comes from.
The force that continues push the injector downward is what creates your torque.



You will only gain 10 – 15 rwhp when going to a stage two injector. This is because the higher injector flow rate of the injector is able to inject a greater amount of fuel before the piston is at top dead center giving the piston a greater push on the decent of the stroke. The point that is often overlooked is the continual push of the piston downward which creates your torque. Since the Stage 2 injector will deplete at 2.6 ms PW and .8 ms of that injection window was pre-TDC, you only have 1.8 ms of driving force to continue to push the piston down with a stage 2.

Now compare that to a stage one injector that has a depletion rate of 3.5 ms PW. You now increase the duration of the driving force to generate torque up to 2.7 ms (holding timing advance constant at .8 ms). This is one of the reasons that you will find stage one injectors pushing around 50 lb ft of torque greater than a stage two injector.

______

When we attempt to “detune” an injector, the main thing we are able to do as tuners is to reduce the amount of fuel injected into the cylinder. We do this by trimming the pulsewidth down to a shorter injection window. The thing that we face is the larger nozzle does not atomize fuel as well as a factory nozzle will causing the injection of larger droplets of fuel. Fuel burn rate is directly related to the amount of surface area where the particles of fuel contact air. Smaller droplets of fuel (smaller nozzles) atomize the fuel better causing a higher surface area for the fuel to react to air. This causes a more efficient burn. More efficient burn = lower exhaust gas temperatures (EGT).

The rule of thumb that I use when recommending injector size to people is strictly based off the amount of weight they plan to tow with the truck or if they do not tow, what their horsepower goal is. Since I can not find a good conclusive list for injector size, I feel this is as good a place as any. This is just a guideline. There are many factors that come into consideration such as turbo size, compound turbos, nitrous, etc. This list does not apply to those guys but if they are building that type of power, they already know this information.

Factory Injectors

AA code Injectors
1994 - 1997 PowerStrokes
90 cc of fuel
Single Shot

AB code Injectors
Early 1999
100 - 110 cc
Split Shot

AC code Injectors
Found in International T444E motors
160 cc
Single Shot

AD code Injectors
Late 1999 - 2003
135 cc
Split Shot

*** Factory injectors do not have a limit for the amount of weight you can tow due to excessive EGT ***

Performance Injectors

Stage 1 Single
160 - 180 cc
0 % over stock nozzle
Capable of 380 rwhp
No limitations on ability to tow

Stage 1.5 Single
160 - 180 cc
30% over stock nozzle
Capable of 380-390 rwhp
NOT RECOMMENDED FOR TOWING OVER 15,000 lbs

Stage 2 Single
160 - 180 cc
80 - 100% over stock nozzle
Capable of 390 - 400 rwhp
NOT RECOMMENDED FOR TOWING OVER 10,000 lbs

Stage 3 Single - There are several different options that are classified as "Stage 3". These injectors are not recommended for anyone who tows.

I found this information on stage 3 injectors based off Full Force Diesel Performance's website. I agree with them on these numbers for the guys shooting for a target horsepower.



Long story made short, if you use your truck as a truck:
BUY STOCK or STAGE ONE INJECTORS

Y'all please use this thread to openly discuss your own experience with injectors and driving characteristics!
If you are still unsure of which injector best fits your application, please give us a call!

Jay Chatham
Power Hungry Performance
678-890-1110

:toast:

One question: How does turning up the ICP effect the atomization on a larger injector?

Please don't take this as criticizing, I need to understand something a little better here.

And maybe I am misunderstanding how engines work, but isn't torque just a measurement of the horsepower at a certain RPM? I'm having a hard time grasping your concept on how part of the stroke makes horsepower, and part of the stroke makes torque.

TORQUE = (HP x 5252) ÷ RPM

By going to a larger nozzle, we inject faster, so that we can raise our peak horsepower RPM?

And to keep that smooth/linear to your new peak HP rpm, you may "lose" torque at a lower rpm, possibly because your actually injecting a little less fuel at that rpm? (Think CC's of fuel, not injector pulse width)

But if you allowed the faster injector to inject even more fuel at a lower rpm, you would in fact make more torque and thus give you more horsepower at that rpm? ( This is assuming your turbo was designed to work at that specific RPM and give you an ample amount of air, or if you didnt care about EGT's)

I guess thats all my questions for now.

Luke@MillerPerformance said:

:toast:

One question: How does turning up the ICP effect the atomization on a larger injector?

Click to expand...

I am a fan of analogies. I have one that will explain this quiet well actually.

Take your typical spray bottle like the one pictured.



Now when you use this bottle, pull the trigger in slowly. Notice how the liquid that comes out does not have a nice, consistent mist? Much larger droplets of liquid should be observed.

Now squeeze the trigger in at a quick pace. Notice how the liquid now becomes a mist? This is because you are generating a higher pressure using the internal intensifier piston in the sprayer.

In relation to our Heui injection system, the ICP from your high pressure oil rail is the same as your finger is on the spray bottle. The more pressure you put, the harder it drives the intensifier piston, the better atomization is achieved at the nozzle.

Increased ICP also causes a greater volume of fuel to be injected in a given period of time.


In explanation of the attachment:
Where a stage 3 (238cc - 80 %) will deplete at 3.5 ms of pulsewidth, this is at 3,000 psi ICP.

With only 2,000 psi ICP, it will require 4.0 ms PW to deplete the same 238-80

mikeeg02 said:

Please don't take this as criticizing, I need to understand something a little better here.

And maybe I am misunderstanding how engines work, but isn't torque just a measurement of the horsepower at a certain RPM? I'm having a hard time grasping your concept on how part of the stroke makes horsepower, and part of the stroke makes torque.

TORQUE = (HP x 5252) ÷ RPM

By going to a larger nozzle, we inject faster, so that we can raise our peak horsepower RPM?

And to keep that smooth/linear to your new peak HP rpm, you may "lose" torque at a lower rpm, possibly because your actually injecting a little less fuel at that rpm? (Think CC's of fuel, not injector pulse width)

But if you allowed the faster injector to inject even more fuel at a lower rpm, you would in fact make more torque and thus give you more horsepower at that rpm? ( This is assuming your turbo was designed to work at that specific RPM and give you an ample amount of air, or if you didnt care about EGT's)

I guess thats all my questions for now.

Click to expand...

Horsepower is actually a derivative of torque based off the same equation. A dynometer will measure torque then calculate the hp.

Take this into consideration, how is the rate in which RPM climbs correlated into this?

"By going to a larger nozzle, we inject faster, so that we can raise our peak horsepower RPM? "

I think the answer to what your asking is that as the engine RPM increases, the allowable limit for pulsewidth decreases. A larger nozzle injector will inject more fuel with a smaller PW window (caused by increased RPM).

"But if you allowed the faster injector to inject even more fuel at a lower rpm, you would in fact make more torque and thus give you more horsepower at that rpm? ( This is assuming your turbo was designed to work at that specific RPM and give you an ample amount of air, or if you didnt care about EGT's)"

I actually share this same theory with you which is why I often find myself recommending people to get a 238cc - 30% injector. It will allow for the full pulsewidth window to be utilized while still injecting a greater volume to produce power. The smaller nozzle will allow for greater atomozation when compared to an 80 - 100% nozzle.

I am a believer that you want the smallest possible nozzle size to inject the desired amount of fuel. If you want 500 rwhp, you have to have around 238 - 250 cc of fuel injected. If that amount of fuel is able to be injected out of a 30% nozzle, you will notice greater atomozation causing the fuel used to run more efficiently than say a 100% nozzle.

Chatham036 said:

I am a fan of analogies. I have one that will explain this quiet well actually.

Take your typical spray bottle like the one pictured.

Now when you use this bottle, pull the trigger in slowly. Notice how the liquid that comes out does not have a nice, consistent mist? Much larger droplets of liquid should be observed.

Now squeeze the trigger in at a quick pace. Notice how the liquid now becomes a mist? This is because you are generating a higher pressure using the internal intensifier piston in the sprayer.

In relation to our Heui injection system, the ICP from your high pressure oil rail is the same as your finger is on the spray bottle. The more pressure you put, the harder it drives the intensifier piston, the better atomization is achieved at the nozzle.

Increased ICP also causes a greater volume of fuel to be injected in a given period of time.


In explanation of the attachment:
Where a stage 3 (238cc - 80 %) will deplete at 3.5 ms of pulsewidth, this is at 3,000 psi ICP.

With only 2,000 psi ICP, it will require 4.0 ms PW to deplete the same 238-80

Click to expand...

So if you jack up the ICP pressure and cut duration can you make a larger injector behave more like a "stock" injector? Or is it too limited?

ToMang07 said:

The difference between hp and tq..... is like the difference between fast and quick.

Torque is how much turning power the wheels have. Horsepower is how fast the wheels turn.

Click to expand...

I always liked the phrase, "HP can be described by how hard you hit the wall. Torque is a matter of how far you push the wall"

He is correct in his equation. Torque / hp correspond by RPM.

Luke@MillerPerformance said:

So if you jack up the ICP pressure and cut duration can you make a larger injector behave more like a "stock" injector? Or is it too limited?

Click to expand...

"yes"

It will cause a lot of other issues like an overly sensitive pedal, romping, etc.
Heck, I have even seen excessive ICP cause the truck to develop a miss.

Through implementation, it just doesnt work as well as the theory would suggest.

Very interesting read jay. Keep the info coming. One question though.....how does the lower injection ratio of a hybrid change any of that

Chatham036 said:

Horsepower is actually a derivative of torque based off the same equation. A dynometer will measure torque then calculate the hp.

Take this into consideration, how is the rate in which RPM climbs correlated into this?

"By going to a larger nozzle, we inject faster, so that we can raise our peak horsepower RPM? "

I think the answer to what your asking is that as the engine RPM increases, the allowable limit for pulsewidth decreases. A larger nozzle injector will inject more fuel with a smaller PW window (caused by increased RPM).

"But if you allowed the faster injector to inject even more fuel at a lower rpm, you would in fact make more torque and thus give you more horsepower at that rpm? ( This is assuming your turbo was designed to work at that specific RPM and give you an ample amount of air, or if you didnt care about EGT's)"

I actually share this same theory with you which is why I often find myself recommending people to get a 238cc - 30% injector. It will allow for the full pulsewidth window to be utilized while still injecting a greater volume to produce power. The smaller nozzle will allow for greater atomozation when compared to an 80 - 100% nozzle.

I am a believer that you want the smallest possible nozzle size to inject the desired amount of fuel. If you want 500 rwhp, you have to have around 238 - 250 cc of fuel injected. If that amount of fuel is able to be injected out of a 30% nozzle, you will notice greater atomozation causing the fuel used to run more efficiently than say a 100% nozzle.

Click to expand...

I agree with all of the above, I guess when I read your initial description in the OP, it comes off as part of the combustion is used for torque, part of it as horsepower, and the nozzle has everything to do with that. Hence why it didn't make sense to me in what you were saying.

Yes the fuel/time is what we run out of to inject our fuel and make our HP at higher RPM, which is ultimately what makes us desire the larger nozzles, and help keep our rods in the block, and effectively reduce unnecessary "low end" torque.

I agree on using the smallest nozzle to give you enough time to inject the amount of fuel to make the power you want (and at the RPM you want). (Though that's not how I ended up with my nozzles)

Luke@MillerPerformance said:

So if you jack up the ICP pressure and cut duration can you make a larger injector behave more like a "stock" injector? Or is it too limited?

Click to expand...

And that is ultimately what I was getting at. I haven't tuned, so I do not know how precise the injector pulse width can be. (I would imagine the limit to be in the armature of the solenoid, but it could also be the resolution of the PCM/IDM and what controls the injector itself too) But it would seem to me you would skew the ICP up and the pulse width down to keep IP as high as possible and retain as much atomization as possible. But maybe the injector pulse width doesnt have enough resolution to achieve that clean and smoothly. Having said that, I believe Charles has tuned is big set of 200% nozzled injectors not to smoke, and to pull really well and still on his stock transmission. Which should say something, though I am unsure of his fuel MPG which would correlate to efficiency.

cjfarm111 said:

Very interesting read jay. Keep the info coming. One question though.....how does the lower injection ratio of a hybrid change any of that

Click to expand...

ICP psi: 3,000
Injection ratio: 7:1 (A code intensifier piston)
Final pressure at the nozzle: 21,000 psi

When you switch over to a hybrid style injector, your injection ratio decreases down closer to 5:1

ICP psi: 3,000
Injection ratio: 5:1 (Hybrid injector)
Final pressure at the nozzle: 15,000 psi

Hybrids just allow a greater fuel capacity without a need for high pressure oil volume.

So if money is not an issue an A code with big oil is more efficient then a hybrid?

mikeeg02 said:

I agree with all of the above, I guess when I read your initial description in the OP, it comes off as part of the combustion is used for torque, part of it as horsepower, and the nozzle has everything to do with that. Hence why it didn't make sense to me in what you were saying.

Yes the fuel/time is what we run out of to inject our fuel and make our HP at higher RPM, which is ultimately what makes us desire the larger nozzles, and help keep our rods in the block, and effectively reduce unnecessary "low end" torque.

I agree on using the smallest nozzle to give you enough time to inject the amount of fuel to make the power you want (and at the RPM you want). (Though that's not how I ended up with my nozzles)




And that is ultimately what I was getting at. I haven't tuned, so I do not know how precise the injector pulse width can be. (I would imagine the limit to be in the armature of the solenoid, but it could also be the resolution of the PCM/IDM and what controls the injector itself too) But it would seem to me you would skew the ICP up and the pulse width down to keep IP as high as possible and retain as much atomization as possible. But maybe the injector pulse width doesnt have enough resolution to achieve that clean and smoothly. Having said that, I believe Charles has tuned is big set of 200% nozzled injectors not to smoke, and to pull really well and still on his stock transmission. Which should say something, though I am unsure of his fuel MPG which would correlate to efficiency.

Click to expand...

I wrote this with the powerstroke newbie in mind. I had the voice in my head that knew I would get romped on for the technicalities. I just didnt want to over complicate the point causing someone to stop reading.

I'm surprised no one has jumped on here yet to say "I can tow 30,000 lbs with my 300cc/200% injectors" yet. I know it is coming... :morons:

cjfarm111 said:

So if money is not an issue an A code with big oil is more efficient then a hybrid?

Click to expand...

all day, every day.
Conventional injectors build more power, more efficiently as long as ICP doesnt fall off.

cjfarm111 said:

So if money is not an issue an A code with big oil is more efficient then a hybrid?

Click to expand...

Tim from PIS told me typically his 175/80s dyno within 10 hp of 200/80s. I can only assume the 175s had the supporting oil. Thats not much more HP per 25cc's more fuel

So I would agree.

good to see you guys posting again..

mandkole said:

good to see you guys posting again..

Click to expand...

Yeah... It's always hard because we get absolutely slammed, particularly through spring and early summer, and there just aren't enough hours in the day to accomplish everything. Ya know? I have always enjoyed the debates, educational threads, and just chit-chatting with everyone. I know Jay and Angela do too, and they're more likely to be on here as I always seem to be cooking up crazy stuff in the lab. (Things like finalizing the setup for the Insight Pro/Minotaur package for the 6.0L! imp: )

Anyway, good to see everyone enjoying a spirited debate.

Take care.

My Home brewd B code 350/200%s (never been on a flow bench) are extremely clean detuned and I am not done dialing in the tuning. My guess is a ratio in the middle of 6:1 and VOP nozzle spring set at 3600 psi probably helps cleanliness. They do what I want them to do. I however mildly tow under 5K. I may try some heavier towing in the future this is also with a completely stock factory turbo currently. The blower helps down low and response but once the turbo is spooled and intake pressures exceed 15ish psi the blower is not creating any pressure.

I do however have a touchy pedal when oil is cold as I ramped ICP pretty good and have PW cut back for smoke control. Once I get the 369 installed I will be taking tuning further.