I came across this data for PSD injectors, which included a "rule of thumb" that you can get about 2 HP per cc from a given injector fuel flow rating.

AA...90cc single shot
AB...120cc Split shot (Early 99)
AD...140cc Split shot
AC...160cc Single shot
Stage-1's...basically same as AC's
Stage-2's...180cc single shots
stage-3's....215-250cc single shot hybrids
BD...250cc single shot

For example, based on the above I assumed that my Early 99 injectors could flow a maximum of 120 cc of fuel during each injection event leading to a PS=Power Stroke. I've checked the following conversion factor and my calculations several times, but this wouldn't be the first time I kept checking an obvious error without catching it! I get that 1 cc=0.00026417 gal, so that my injector flows (0.00026417)(120)=0.0317 gal max for each injection during a PS. There are 4 PS per revolution, so that the #PS/min=(4)(RPM), and the #PS/hr=(60)(4)(RPM). Therefore the max VFF=Volume Fuel Flow, gal/hr=GPH is given by... (#PS/hr)(#gal/PS)=(60)(4)(RPM)(0.0317 )=(7.608)(RPM), which implies that my puny injectors can flow over 7600 GPH at 1000 RPM, which is clearly an incorrect result! Even if the 120 cc is referring to oil flow, and I divide by x7 to get the fuel flow per injection, the answer is still way to high, as I think that the max flow of the fuel pump is something like 50 GPH! What's going on here????

It seems to me that the above injector #'s are at least a x500 to large to make sense. If my injector flowed (120)/(500)=0.24 cc per injection I'd get a max GPH=48.7 at 3200 RPM, which would match the fuel pump capability, and if they're x1000 too large (misplaced decimal point) I'd get 24.4 GPH, which would still be more than enough VFF to make the 260 HP predicted by my model.

 

That is alot of very useful information but was wandering how could i tell what injectors i have in my truck? do i need to pull a valve cover and look at the injector or are the injectors changed by year?

 

You have AD injectors.

 

thanks for responding, just curious but what is the differance between split shot and single shot? Which is better?

 

Single shot is one injection of fuel, where a split shot will have a smaller "pilot" injection to begin pre-detonation, then a secondary larger injection.

Split shots will have a quieter idle.

Singles can support more fuel, like the hybrids and BD's. The reason is that HEUI injection has it's limits in terms of fuel delivery when it comes to splits.

 

E. I think I see where the problem is. Now I know very little about intricacies of injector operation, but I think you leaving out one very important variable in operation. The variable is that injectors are fired with variable pulse width signals, the longer the signal the more fuel is injected in that shot. So though the injectors are capable of injecting 120, 140, 180 cc shots that is a rating at maximum pulse duration for that injector, and maximum pulse durations are only going to occur at WOT. So at idle you should be controlling the injector with a very narrow PW to inject a very minimum amount of fuel.
I have seen numbers for pulse widths measured for duration times taken by others on injectors, maybe not ours but I believe this is similar. maximum pulse widths for a shot can be calculated I believe by calculating the time of number of degrees of rotation of the crank that you need the injection event to take place in for a given rpm, as an excercise.

Anyway without being an expert this is how I believe the injectors work.

 

PS. Also thinking about it further and comparing in my mind the size of the injetors and what a 120 (or 140, 160, 250) cc looks like in a syringe, I would think that is a lot of fuel! I cannot see that it would actually take that much fuel to make the power. Nor that an injector could actually even hold that much fuel given the volume dimensions of the injectors. Maybe you need to research on an injector builder site what those cc ratings are actually signifying and if they are tied to a physical dimension of the injectors. Or how flow rates are determined for specifying an injector in cc's. It may be a bench flow rate that is only loosely tied to volume of fuel that would be injected during a power stroke.
A sanity check could be to also take the enrgy content of a gallon of fuel, assume an efficiancy of the system (maybe 25 to 30%?) for the whole truck as a black box, then convert energy to HP and determine how much fuel it should take to produce a given HP. You should be at least in the ballpark then for how much fuel it actually takes.

 

dsldrvr's post made me think, so I went and drug out some of my old stuff from farming, I found my 50cc multi dose syringe, and measure it approx it's 3/4" inside diameter by 5" long, that in itself is larger than the injectors in our trucks and is less than half the listed size of the injectors for most of them so those number have to be wrong my guess is that they are actually .120cc

BTW 120cc calculates out to .246 ounce or quarter ounce of fuel per shot.

 

Well that's exactly what I did, but I used my new model at WOT to determine that the 120 cc # for my injector if probably a x1000 more volume than the MAXIMUM voulme it can inject for the max pulse duration on a single injection. BTW, I redid my model to use your suggestion of equivalence ratio, and ran the fuel flow that way from 20% WOT to 100% WOT, if you want to see the new version send to kempegenek@gmail.com and I'll return a copy. I wanted to make sure my model wasn't flowing more GPH than the injectors can provide. There's no way they can flow 7600 GPH, and if the data I posted above (which I've seen in several places) is too high by x1000, I'm just approaching the GPH limitations of my early 99 injectors at WOT, as my model gives a required flow of 24 GPH at max RPM and boost. This # also sounds correct, because I think I read that the stock pump is good for 50 GPH, and at WOT about 50% of the fuel flow is returned to the tank.

My question is are my injectors only good for injecting a MAXIMUM VOLUME of 0.120 cc in a single injection stroke, or can they do better than this? A 120 cc injection is clearly in error, unless I don't know how much is in a cc, and I always thought it was (1/1000) liter.

 

Then how do you explain the rule of thumb about 2 HP per cc? I've searched, and I've seen these 100+ cc #'s for injectors a lot of places. Maybe these #'s come from a flow test spec where you collect the injector output from 1000 max injections and measure that amount?

 

I dont understand is that they flow XXXamount of cc in how much time? There doesnt seem to ever say how much they flow per time. Perhaps they are going by hour, or minute?

 

Well neither do I, that's why I posted, to find out from someone that knows the answer. I posted what I've seen here on FTE (but never thought just what it means until I started checking my model against it) and on the dieselstop site. It just says 120 cc injector, and about 2 hp per cc! My model gives 260 hp for me, and the only thing that seems to make sense is that 120 cc is the total flow on a test bench after 1000 max injection cycles. If someone knows different than this please let me know!

 

Well your questions have lead to some interesting reading and finds. I am starting thinking that monsterbaby is correct in his factor of 1000. All of the literature I have been looking at is describing injection rates in cu. mm per shot. Baby Swamps for the 94-97 ps injectors are described as having stock flow rates at 73 cu mm. listed here:
http://www.blackclouddiesel.com/Ford/injectors.htm
For the 97-2003 injectors flow rates are not specified that I found though.
[url=http://www.freepatentsonline.com/5485820.html, This ] patent from Navistar in table seems to indicate that a stock engine the injectors will need between 4.4 to 68 cu mm of fuel per event depending on a myriad of factors. Does not indicate year model of this engine though.
I too have seen those designations on so many cc injectors, but cannot find the answer to how they come up with those designations, for now dividing by 1000 seems to be as good an answer as any. Then i believe yes, your 120 injectors would be good for a max injection 120 cu-mm or .120 cc and not better. I think the larger volume injectors I have read somewhere basically bore out the chamber inside and therefore increase the dia. of the plungers, etc, along with larger nozzles, except the stage 1.5's that state same size nozzles are used.
a cc, or cubic cm (cu cm) should be 1000 cu mm's if I have my conversion right, and 1cc does = .001 liters.

 

The 120cc rating has to be a flow rate not a volume of flow per injection. By that I mean that it must be 120cc per some unit of time (I'm thinking seconds). I say this because the injectors are controlled via pulse width modulation. Because of this the injectors could theoretically flow 20 gallons in one injection if the pulse was long enough.

Just to add some more info to the discussion. If I remember right my truck's injector pulse width is about 2.5 ms under normal driving conditions. If anyone wants exact numbers let me know and I will datalog the pulse width or anything else on my way home today.

 

However there is a check (ball) valve in the injector so that the injector could only inject as much fuel is in the body of the injector. When the pw goes to zero then the injector is refilled with fuel from the rail.