Ok, I'm not near as well-versed as some of y'all are, but I think it'd be cool to share what we know. I'm also going to state the all that's below is assuming we have adequate air as well as oil. Here goes!

I've got stock sticks and I've been running tunes. I've noticed that obviously, more fuel has equated to more smoke and higher egt's... to get more fuel requires increasing the PW (pulse width). This also increases CP's (cylinder pressures) too. But, I know that guys who swapped out for AC's (stage 1's) noticed more power, lower egt's, and better mileage. The egt's are lower and the mileage is better because the larger amount of fuel is delivered in a shorter amount of time than with stock sticks. Egt's can still get high as well as cylinder pressures and the amount of smoke, but only when the PW starts getting higher than what was typically allowed in stock tuning with the stock sticks... 2.5 milliseconds I think? Throw nozzles into the mix and now we're capable of emptying the injector faster... we're not necessarily flowing more fuel either. I have been told that ideally an injector should empty in 2.5 to 3 milliseconds... sound right?

So here's what I'm more curious about more than anything... the egt's and CP's increase not necessarily because we put more fuel in, but because the PW was drawn out to the point where the injection of fuel is occurring farther before and/or beyond that ideal point/time needed to burn it all off efficiently causing incomplete combustion which results in higher egt's and CP's as well as more smoke, right? Stock sticks (AB's, AD's, and AC's w/stock nozzles) take longer to fully empty than is really desired, that's what the nozzles help with... to allow the injector to empty sooner, right? It also helps with more complete combustion so we get a few more horses there as well as less smoke, right?

So here's my thinking in regards to what I have in mind for my truck in the future. My motor is by no means done (323K), but it does need to be treated a bit nicer than a motor with 100K on it. I like my tunes, they make a big difference and if I had enough oil, my tunes would be even better! But I also have much higher EGT's, it smokes more, and I know my CP's are alot higher too. I could go and put nozzles on my AB's... that would bring my EGT's down as well as my CP's, and I'd also get a few more horses and less smoke because combustion is more complete but it wouldn't be much of a power gain. Plus, my injectors are pretty old. So how about some AC's (stage-1's)? They flow more fuel, are more efficient since they're single shots (does that affect EGT's any? Have to wonder), have less smoke to the power, and also are more oil-friendly. I can get more power out of them and the EGT's and CP's will stay nice and low until the PW goes above typical stock PW's. Once the PW starts getting longer, the EGT's and the CP's start to get hairy and it'll smoke more. This is why I'd like to have AC's with nozzles (stage-2's). They'd empty faster and I would assume would lower EGT's and CP's... I'd also get more power because of the more complete combustion and less smoke. This would put me in the 425HP range and would in my mind make for a pretty reliable truck... EGT's stay down as well as CP's and PW. Power would be up and so would the mileage.

So there's how I understand it... add to or correct me. I'm a firm believer in learning something new every day.

 

There's some good thinking there, but I have to make a few corrections.

First, the cylinder pressure PEAK doesn't have to change. I can back off the start of injection to where cylinder peak pressure is WAY below what it is even stock. The longer pulse width of the injector will increase the AVERAGE cylinder pressure, but it has nothing to do with the peak.

AC injectors are NOT less smoky than AB/ADs. The only reason that AB/AD injectors are so smoky is because they are very unfriendly to high pressure oil. ACs have the same nozzles as AB/AD injectors, so while they do have a higher capacity, they also take roughly the same time to empty.

I am not going to dispute any claims you've made toward larger nozzle orifices as you are spot-on. Keep in mind though that the larger you go, the harder it is to tune to remain streetable.

Second, single shot injectors WILL NOT increase your fuel mileage enough to justify the cost. It's like buying aftermarket tuning just to see a mileage increase. If you see anything, it's a bonus. ACs are pretty stock-HPOP friendly (efficient), but larger nozzles on those injectors will also cause the flow demands to be increased (more fluid movement over time) and will likely still need an aftermarket pump to efficiently keep up.

AC's will bury a pyrometer needle pretty effortlessly and depending on the tuning, larger nozzles may only make a small difference. Larger nozzles on your stock ABs (or ADs) will only make the injectors MORE oil hungry than they are now, but with the lower pulse width required to empty them, you may not notice. It all depends on how hard you run it and how healthy your pump is.

I regret to say that I let a fellow over at PSN get to me a little bit and I had a little disagreement with him. If you're up for some reading on this, you can check it out.

 

Makes sense... CP's are something I don't know much about just because I don't tune. This is good stuff to know... would like to know a bit more about CP's, though. I had read that more HP doesn't necessarily mean more CP and that high-hp can be had running the same or less CP than stock. But I'm guess peak isn't as big a deal as average CP, right?

EGT's are interesting... I wasn't figuring a big difference as I know that more fuel is still more fuel. I guess what I'm shooting for is what would be more efficient... while not necessarily a big difference, a shorter PW seems to go hand in hand with lower CP's, EGT's, and more complete combustion.

Like I say, I've got 323K... I'm not gonna rebuild just because I wanna see how far it'll go, but I do want to be nice to it. My goal I guess was to find an injector that would empty in the desired 2.5 to 3 ms range while flowing a decent amount. AC w/nozzles (stage-2's) seemed to do it. Any larger and the supporting mods seemed to start getting hairier.

 

I also understand about unloading too fast... I called Casserly and asked them about nozzles on AC's and they said that with 100% nozzles, they'd empty in 2.5 to 3 ms. I've been told that's fairly easy to tune for. Sound right?

 

No, PEAK cylinder pressure is what makes connecting rods make an exit, stage left. Average cylinder pressure makes everything happy....as well as the driver.

The same amount of fuel in less time will use all of the oxygen in the cylinder more efficiently. Dragging out the injection event, while making a higher average cylinder pressure, tends to be more smoky because oxygen is being consumed while the injector is still spraying fuel.

My current FFD 160/100% injectors begin to tax my high pressure oil system at about 2.5mS of actual injection pulse width. They are not quite empty at that time though, however, it's hard to tell when I can't maintain 3000 PSI at that value and the pulse width goes sky high to maintain the mass fuel desired. 2.5-3.0 mS is a HUGE amount of difference when dealing with injection pulse width...especially with larger nozzles. Once I get an Adrenaline, I'll push for 3.2 mS and see where my numbers are. I don't plan on making much more power, but due to my own curiosity.....

 

I was gonna go with bigger oil, anyways... I've got the old 15* pump so a new one is in order anyways. I get the CP's, now... sure would like to do some tuning some time to see all this for myself. Have you had your 160/100% on a dyno, yet?

 

What do you consider to be an ideal PW for an injector to empty at? Also, how do your egt's and CP's at a given PW compare to running stock sticks and tunes? Assuming oil isn't an issue...

 

A LOT. Heck, I've even started it on fire on the dyno.

 

What kinda numbers did you see?

 

Ideally? Depends on the injector and the injection pressure. When pressure goes down, the pulse width has to go up to maintain the same amount of mass fuel desired. There is no "ideal" pulse width.

Stock sticks and tunes are close to the 160/100% injectors with my home-brew tuning. I mess with very little in regard to when the fuel is injected (peak cylinder pressure). I am a believer in the longevity of the engine. The engine stays quiet and I use the same 375 RWHP tune for daily driving, towing, performance, etc.

 

402 on a bone-stock truck. Only injectors. I used a straight-through muffler off of a 95-97 truck too.

I did it to give the finger to those people who claim you need all sorts of aftermarket stuff.

 

Sweet... that's pretty good there.

 

When my 95 needs new injectors, I'm thinking of 100% nozzles on the stockers......

just to be different.

I don't need more than 260 HP in that truck.

 

Yeah... mine aren't bad. No more than 1.5 to 2% of RV on a couple three cylinders. My dad and I just got done working his 6.4L over so now I've gotta do something to my truck... his 180hp street tune is just crazy!