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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.

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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.

*Approximate HP of injectors with chip. Some injectors require more modifications to see this number.

205cc up to 425hp

238cc up to 500hp

250cc up to 525hp

275cc up to 550hp

300cc up to 600hp

350cc up to 650hp

400cc up to 650+hp


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
 

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Good thread.

Should clear up some confusion

This should be a sticky!
 
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nice write up on PW's and the injection event itself... not a lot of information for people to see about that topic on here :)
 
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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.

I do drive this truck daily.
 

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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.
What do you mean by this ?

Also what do you mean by home brewd b codes?
 

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What do you mean by this ?

Also what do you mean by home brewd b codes?
I run an Eaton Roots TVS blower that feed the turbo.
I built the injectors using B code DT466 split shot injectors that I turned into singles.
 

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I run an Eaton Roots TVS blower that feed the turbo.
I built the injectors using B code DT466 split shot injectors that I turned into singles.
Oh okay I understand the injector situation now but why wouldn't you have the turbo feeding the supercharger instead of the other way around... Plus what I meant by my first question is you said that after manifold pressure reaches around 15 psi the blower doesn't build any pressure... The blower pressure is just going to compound the turbo boost pressure so what do you mean ?
 

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Oh okay I understand the injector situation now but why wouldn't you have the turbo feeding the supercharger instead of the other way around... Plus what I meant by my first question is you said that after manifold pressure reaches around 15 psi the blower doesn't build any pressure... The blower pressure is just going to compound the turbo boost pressure so what do you mean ?
The blower creates 2 psi idle and 13psi @ 3000 rpm alone. Once the turbo spools up it will pull more air than the blower can push. I have a 3" one way flapper valve that sucks open at that point and the pressure differential of the blower goes to 0 and the blower is then requiring very little power to spin freely. (Unloaded)
 

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The blower creates 2 psi idle and 13psi @ 3000 rpm alone. Once the turbo spools up it will pull more air than the blower can push. I have a 3" one way flapper valve that sucks open at that point and the pressure differential of the blower goes to 0 and the blower is then requiring very little power to spin freely. (Unloaded)
If you had the turbo feeding the blower I think you could eliminate that problem cause then it would compound... Either way tho what kind of power is hitting the ground have you dynoed it ?
 

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Also since you did custom tuning of your own ... I'm curious how you decided to tune it with the blower ... Were you conservative on the low rpm torque curve since you have the blower making the down low boost (aka connecting rod insurance lmao)
 

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My tune is pulled back to a max of 1.8ms and 3000 ICP. I have not messed with the rpm fuel limits etc as at this detuned power level the factory forged rods should be ok and have been so far. I did build a 2.3ms tune but fuel pressure could not keep up (stock mechanical only) it had gobs of power but was very Smokey. Worse than a freight train. The ICP also was not dialed in for that tune. The 1.8ms tune is keeping it alive as it is my daily driver and I don't need 800 horses to get me to the grocery store. Right now it's probably 300-350 hp somewhere with the daily tune. I will be keeping it under 400hp unless I build a motor as reliability is a concern. I may build a fun 500 ish tune after I get more supporting mods done.

As for the blower the setup is not done yet. I have a S369 to install first. The TVS is only spinning to about 10,000 rpm @ 3500 and there is more on tap as the blowers maximum rpm is 19,000 rpms. Upgraded bearings would push that further. The blower is capable of 1400+ cfm. I have been running a blower for about 2 years now and have been happy with results.
 

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My tune is pulled back to a max of 1.8ms and 3000 ICP. I have not messed with the rpm fuel limits etc as at this detuned power level the factory forged rods should be ok and have been so far. I did build a 2.3ms tune but fuel pressure could not keep up (stock mechanical only) it had gobs of power but was very Smokey. Worse than a freight train. The ICP also was not dialed in for that tune. The 1.8ms tune is keeping it alive as it is my daily driver and I don't need 800 horses to get me to the grocery store. Right now it's probably 300-350 hp somewhere with the daily tune. I will be keeping it under 400hp unless I build a motor as reliability is a concern. I may build a fun 500 ish tune after I get more supporting mods done.

As for the blower the setup is not done yet. I have a S369 to install first. The TVS is only spinning to about 10,000 rpm @ 3500 and there is more on tap as the blowers maximum rpm is 19,000 rpms. Upgraded bearings would push that further. The blower is capable of 1400+ cfm. I have been running a blower for about 2 years now and have been happy with results.
Very detailed explanation I like that :) I completely understand keeping it at 400 or under for a daily it just gets to unpredictable after that IMO... Very cool that your blower ain't done blowin yet she got more on tap lol.. I was just asking the dyno question to see if you threw it on there just to see what she makes... She's probably somewhere in the 6-700 hp capable range is my guess and a lot more with nitrous ... That just gave me an idea ... A turbo , blower, and nitrous ... Hmmmmm :rofl:
 

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I may dyno it someday. It's not my main concern right now. Still a lot of work to do and I have too many other projects so it will get improved as time allows.
 

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I may dyno it someday. It's not my main concern right now. Still a lot of work to do and I have too many other projects so it will get improved as time allows.
Awesome keep me updated ... Also kudos to you for doing everything yourself and throwing a damn roots blower on there.. Big achievement in my book :)
 

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Good info in the first post. We constantly have guys asking us to detune 250/200 injectors for a bone stock truck. I am always having to explain the reason it does not work well. Sure, you can pull back fuel, but in doing so you get some side effects, as explained above.

I agree with the statement of choosing your injector for your trucks purpose. Towing heavy, don't go with huge hybrids. Building a pull truck, feel free to go with huge hybrids.

Also, matching the injectors with a proper turbo is key! I think this is the biggest issue to get through to people, at least in my experience.
 

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Awesome keep me updated ... Also kudos to you for doing everything yourself and throwing a damn roots blower on there.. Big achievement in my book :)
I have other toys to drive if I needed but it is my daily driver. Which sometimes can be fun but it's a rolling project that does not rest very many days a year. I have to plan to take the truck down for a day or whatever and get it back together asap.
 

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Curious to see what you would recommend for stage 1.5 injectors and turbo? I am seeing a lot of 38rs recommended. Looking at upgrading a few things on my truck. I pull around 15k bout once a month. Other then that it bout 3k in the bed going 400 plus miles to jobs. She has 290k on her. Bout to pull her to do the dreaded oil pan and figured its a good time to clean her up and do upgrades. I've read that injectors are good for about 300k in a diesel so i am thinking I am close enough might as well do it now. Thanks for the original post. That helped out ALOT!
 

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Look at the KC turbo option that CNC sells and a 160/30 seems to be a happy choice. P.I.S. injectors also seem to be a quality choice.
 
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What supercharged said, 160/30's and the kc38r would be excellent. Only reason I have a 38r over the KC version is KC hadn't come out with theirs yet.
 
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