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

[jeremiahmercier]

Had 160/0s and D66 with T500 originally, had high Egt's and Smokey down low, decided to change the combo to the BASB (364.5) and 175/100s, had almost zero smoke and never really had to watch pyro anymore. I personally had better experience with the larger nozzles, but it's also important to note I chaged turbo at the same time, and we all know that was a major contributor to the lower Egt's as well. Mine was a zf5, and had 285/75/r16, with 3.55s. But after my experience with that truck, when we decide to upgrade injectors in our 02, it'll probably get 230+ with whatever nozzle. Both truck are/were primarley bought to tow travel trailers, in particular at that time we were pulling my parents 31ft with two large slides (only around 8000lbs), this was just my experience and am in no way trying to argue Jay's point, again just my experiance

06-6.0l, CCLB 4X4, studded, reworked heads, egr gone, cab reroute, blue spring mod, 6.4 banjos, updated dummy plugs, stand pipe, and stc fitting; New oil cooler, New ipr, New icp, atlas 40 FICM, powermax turbo, and Geerhead tunes, 325/65R18

 

[cjfarm111]

Once again it has a lot to do with he oil side as well. Wish someone could cook up a single big pump at a reasonable price to full support these A codes. That sure would make a lot of people happy with there injectors

 

[Luke@MillerPerformance]

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

For all your complaints about big nozzles, you can still tune them pretty freaking good. About to go flash Hot Sauce v2 in my truck.

 

[Chatham036]

Thank you sir.
All I can go by is what our customers give us as feedback.

Feedback is typically much better in regards to stage 1s than any other size. Hence why I recommend them so strongly.

None of this is to say that live tuning can't set off a set of 200% nozzles to run great by implementing live tuning into the equation.

 

[superpsd]

One advantage I can see with a stage 1 injector is availability of a replacement AC code injector anywhere across the state's if you are traveling a lot far from home. A little more difficult and you will be down longer waiting for a custom injector to show up.

 

[ja_cain]

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

I posted up a paper illustrating how effective atomization can be with regards to power production. I'm too tired to repost it right now, but add it to the thread again if I find it. The problem I struggle with is the fact that the large nozzle hybrid can inject more fuel when conditions are just right for combustion (temp/pressure) overcoming the decreased surface area argument. I know there has to be a tipping point, but I don't have the software or know how to model it. Lol!

Thanks for your insight in all of this. I agree that it is better to use the smaller nozzle and higher icp to created a more efficient setup. I think there is a point of diminishing returns with regard to nozzle size vs icp though. I also think higher injection pressures are going to take their toll on the heui injectors and orings after a while. I have a feeling they just are not designed to run at those higher pressures on a regular basis.

 

[ja_cain]

One more thing, larger nozzles are going to exacerbate any differences in cylinder compression ratio differences. Hence the comment by Chathem stating they can cause a miss.

 

[ja_cain]

One advantage I can see with a stage 1 injector is availability of a replacement AC code injector anywhere across the state's if you are traveling a lot far from home. A little more difficult and you will be down longer waiting for a custom injector to show up.

Excellent point man. One more reason to go with a DTA-360. LOL!

 

[Arisley]

good to see you guys posting again..

I agree. Discussions with this group of people tend to stay more on track. I have missed them.

 

[m_j]

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.

is this just an over simplification?
cause it dont ring true unless you weld the nozzles closed
isnt the nozzle opening the 'restriction' in the 'pressure is a measurement of restriction'?

I think there is enough simple information out there.

timing got glossed over in this as well.

 

[CurtisF]

At some point, someone posted online that you can have large 100 % - 200 % nozzles while maintaining the ability to tow heavy

It's not exactly "detuning" per-say, but my old truck towed frequently and often very heavy loads (up to 25K lbs) all at elevation..... with 200% nozzles. EGT's weren't an issue, and that was just with a little 38R.

There is something I wanted to point out along those lines as to why it is possible:

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).

Yes, a more efficient burn can help decrease lower exhaust temps. However, there is something else that happens between small vs large nozzles.

When you drag pulsewidth out too far, EGT's begin to rise exponentially. This is regardless of how good the atomization is and how small the droplets are. Too long of a pulsewidth creates way too much heat. This is why EGT's skyrocket on small or stock nozzle injectors when attempts are made to "empty" them out. It's why it's near impossible to tow heavy loads up a mountain pass in a common race tune on stock injectors.

In comes larger nozzles. Sure they aren't as efficient in terms of atomization, however they are far superior in delivering greater amounts of fuel in a much smaller amount of time. This enables greater power levels to be achieved without an astronomical temperature spike. Larger nozzles have the ability to inject more fuel into that small window, especially as RPM's increase and that injection window shrinks.

My old truck could tow with a higher power level under the 250/200's then I ever could with stock injectors. EGT's were less with the bigger injectors at equal power levels. Towing with a 300+ hp racing tune on stock injectors netted EGT's well over 1400 degrees while trying to tow up a mountain pass. Towing with a 300+ tune on 250/200's would peak under 1200 degrees. This is with the same turbo setup, same exhaust, same intake, etc.

Is it "detuning"? Well not exactly, but there are ways to dial in even larger nozzles to behave.

Is it easy? Absolutely not. I was constantly tweaking tunes trying to find the right balance. I was a novice tuner at best, I'm sure a professional probably could have dialed it in much quicker than me. However I did manage to get it running like I wanted.

Is it for everyone? Again, absolutely not. If you want to experiment, by all means have fun with the larger nozzles/injectors. But if you want something solid and proven right out of the box, go with Jay's recommendations.

That was all. Just a different observation. In reality I do agree with Jay, but just wanted to point out something that is important and a very good reason why larger nozzles exist in the first place: to create more useable power.

 

[Chatham036]

is this just an over simplification?
cause it dont ring true unless you weld the nozzles closed
isnt the nozzle opening the 'restriction' in the 'pressure is a measurement of restriction'?

I think there is enough simple information out there.

timing got glossed over in this as well.

All we can do is calculate the final pressure at the nozzle. There is no feasible way to measure the actual pressure.

"isnt the nozzle opening the 'restriction' in the 'pressure is a measurement of restriction'?"​

There is definitely a lot of math to back up the fact that a larger nozzle will flow greater volume. With the intensifier piston traveling at a set rate from top to bottom in one injector to the next, you would see a final injection pressure drop with larger nozzles.

One thing you may not be taking into consideration is that as the final drive pressure is reduced from the larger nozzle, the intensifier piston will then move more quickly from top to bottom in attempt to balance out the injection ratio.

"I think there is enough simple information out there."​

I thought so as well until I started getting feedback from my customers who were having excessive EGT issues when towing heavy weight. Someone, somewhere told them they could tow unlimited weight with a 180cc/100% injector without the concern of EGT. So they slapped a set of stage twos in then over fueled the rest of the system.

"timing got glossed over in this as well."​

Yes it did. The target audience for this article is for the person who just wants a little more power while still being reliable with the ability to tow heavy. 95% of these people typically do not have a solid understanding of timing advance that would constitute as a solid foundation to elaborate off of.

Particularly when we start talking about the inherent timing advance from a larger nozzle in it's relation to the desired timing advance through the tuning. Then there is the conversation on how temperatures effect timing. Then the conversation on compression ratio in it's impact on pressures.
But that still does not cover the topics needed for that conversation. You also have to consider the point of injection in it's relation to the point of combustion which will subsequently lead us down the road back to intensifier pistons and ICP.

All this and the topic of timing by RPM is still not even grazed upon.

In conclusion, the goal of this article is for the average Joe and to simplify the topics enough to be palatable to them in a way for them to digest the information.

 

[mikeeg02]

I thought so as well until I started getting feedback from my customers who were having excessive EGT issues when towing heavy weight. Someone, somewhere told them they could tow unlimited weight with a 180cc/100% injector without the concern of EGT. So they slapped a set of stage twos in then over fueled the rest of the system.

Isn't this more of the problem than the nozzle size? Maybe it wasn't explained better the need for supporting mods to run the larger injectors, or they didn't want to spend the money. Maybe they were told they could run them detuned until they upgraded the charger etc.

The caveat is if they complained about it being hot, I'd dare to bet they were running too hot a tune for the charger etc. So they actually caused their own problems by allowing themselves to run too hot a tune for the fuel they had available?

Just thinking out loud.

 

[Chatham036]

Isn't this more of the problem than the nozzle size? Maybe it wasn't explained better the need for supporting mods to run the larger injectors, or they didn't want to spend the money. Maybe they were told they could run them detuned until they upgraded the charger etc.

The caveat is if they complained about it being hot, I'd dare to bet they were running too hot a tune for the charger etc. So they actually caused their own problems by allowing themselves to run too hot a tune for the fuel they had available?

Just thinking out loud.

You are right on par with my mind set on the matter.
If I had a 7.3 and wanted to be able to tow while having 600 hp on tap, I would be running 300cc/200% injectors with compound turbos. Something in the realm of a s364.5 SXE as a high pressure with an s488 as low pressure.
I would be willing to bet that combination would never see over 1,200 degrees at wot, even with less than desired tuning.

It is all a balance of air to fuel at the end of the day. These trucks like to run lean. Overloading the engine with a big fuel just causes them to run rich and smoke excessively.

 

[mikeeg02]

So in effect you do believe larger injectors can typically be detuned, (as im sure you've done plenty) and appropriately. But ultimately it's the users responsibility to utilize the proper tune?

 

[Chatham036]

So in effect you do believe larger injectors can typically be detuned, (as im sure you've done plenty) and appropriately. But ultimately it's the users responsibility to utilize the proper tune?

I can not make a 200 % nozzle function with the same atomization or control as a stock nozzle. Just wont happen. This is what I am referring to when I say you cant "detune" the injector.

Even if you pull 90% of the PW out of the tune for the 200% nozzle, it will not function the same as stock at low RPM / off idle in particular.

The inverse is also true. A stock nozzle will not create the same power at higher RPM as what a larger nozzle can with the same displacement injector.

I do believe that big nozzles have their place with the correct tuning to compliment them.

 

[mikeeg02]

Are you not able to change skew rate for the manual fuel desired? To somewhat mimic off idle start out?

(Honest question, again I dont tune)

Obviously this wouldnt do anything for trying to make the injector more efficient, but I would think it would be an option to slow the rate at which off idle start out "ramps in" keeping it a "stockish" feeling at the pedal?

 

[Chatham036]

Are you not able to change skew rate for the manual fuel desired? To somewhat mimic off idle start out?

(Honest question, again I dont tune)

Obviously this wouldnt do anything for trying to make the injector more efficient, but I would think it would be an option to slow the rate at which off idle start out "ramps in" keeping it a "stockish" feeling at the pedal?

The only thing we can do to slow the rate of the nozzle down is to reduce the ICP which only exacerbates the issue of atomization.

The main way to make the truck feel "stockish" is through the ICP tables in relation to the base pulsewidth tables. It all comes down to how you profile the curve for the way the truck will run. Too much ICP too early in the RPM band can cause the throttle pedal to become overly sensitive causing a romp. Too little and it will haze while being sluggish.
There is a balance somewhere in the middle that allows for the larger injector nozzle to run decently well although it will be more inefficient than a stock nozzle because of the reasons posted above.

Since the stock nozzle has a slower injection rate, it allows us as tuners to have greater control over the pulsewidth window as well as ICP curves.

Here is a loose analogy that might help you understand this concept better.
Someone with a bow & arrow shoots the arrow past you. Your job is to grab the arrow as it passes.
The person shooting has two different speed bows. One is 100 fps (stock rate) and the other is 300 fps ( 200% over stock)
Will it be easier for you to catch the stock rate arrow? or the 300 fps arrow?
The catching of the arrow is to simulate the target fuel quantity.

Say you need to hit 80 mg of fuel per stroke to run efficiently. If the injector has a slower injection rate, it will be more accurate in achieving the 80 mg than the larger nozzle.

Another way to look at it, it is similar to trying to use the fuel pump and stop the pump exactly at 25 gallons. If the pump is moving a lot of fuel, it will be harder to achieve the 25 gallons than if you were pumping at a slower rate.

 

[Derek@Vision Diesel]

Great read Jay!!

It is amazing how much the "opinion", for lack of a better work, changes throughout the industry. Some thrive and preach the larger nozzle idea without any reservation at all on towing or anything. Then you have PHP and a few others that are all about the tiny nozzle/long pulsewidth way of doing things.

I have seen first hand how both can work. I have personal owned a 200% nozzle 7.3 and a 30% nozzle 7.3, they are very different but can be made very similar with great tuning!

 

[mikeeg02]

I think I have a pretty good understanding of the concept we are trying to accomplish, though I do appreciate the further explanation. Where I don't understand is what part of the equation is lacking. Whether there isn't enough resolution to accomplish this on the tuning side, or if it comes down to the probably "sloppiest" part of the injector, which IMO should be in the in the solenoid.

While I think there is good info for to be had in this thread, I think there are two trains of thoughts on "oversizing" injectors.

For me, when someone says they want a hybrid 200cc, 80% nozzle I think to myself, why oh why wouldn't you just get a 238 or 250 with the same size nozzle, and run a tune that only uses ~200cc and have a future if you decide later "D@mn, I wish I had more fuel to play with" They are basically the same price(if not exactly), and since the 238 or 250 can be limited on pulse width to ~200cc of fuel, why wouldnt you do that?

Can you see a reason why that thought process is foolish?
(Or does that thought process go back to the user ending up running too hot of a file and complaining about EGTs?)