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Injectors, PW, and Flow rates! OH MY!

41K views 264 replies 62 participants last post by  southmike 
#1 ·
Standard theory disclaimer here guys. It is just physics and is the basic principles that I operate under. Its more along the lines of this is how I build my truck and if you disagree it don’t matter…. :poke: The following information and graphs show concepts and will put you into a ballpark, not guaranteed results. There is no garantee that the computer will even work at the extreme end of the RPM band, but I think it is good for a good ways North of where we are...

I’m going to try and explain why we have been talking about fast injectors and what that means, implies, and what we hope to achieve by advancing this technology. And trust me this is EXACTLY how the rest of the mechanical world keeps advancing and stepping up its game. For all out max power that will ALWAYS remain that way. But for everyone that would like to drive their truck everyday or keep up with the common rail crowd this applies to your truck!

First lets take a look at some 238cc Hybrid injectors with 80% tips. Here is a 3d graph that I generated from flow data collected on a typical set of these injectors:



You can tell that the fuel quantity maxes out as ICP and PW maximize. Nothing particularly spectacular about that. But I then took this data and overlapped that with the FDCS capabilities of the 7.3L PSD. Then I removed some of the high fueling down low on a WOT run and used that information on fuel quantities to generate HP and Torque curve capabilities. This doesn’t take into account any other limitations other than fuel, and can be shifted around by tweaking parameters. Not here to argue the numbers, just show the concepts that the graphs represent.



Looks pretty much exactly like a “typical” hybrid dyno graph except it goes to 6K RPMs right? I ran it out to 6K RPMs to help illustrate our current fueling capabilities and further my point. Notice that the graph peaks at about 2800 RPMs? Pretty familiar huh? By the time you pull enough torque out down low to make your motor live, you will never empty an off the shelf 238cc injector. You can add more power capabilities in down low by adding in more PW below this, but this also ups the torque curve which one of the reasons we all need all these fancy billet rods and junk…..

Compare those HP and TQ curves with many dyno graphs of a PSD with hybrids and you should find them pretty close in concept and shape. Probably similar peak numbers in some instances, a little low for others a little high for the rest.

Now here is the 3d flow graph of a “FAST” 455cc injector:



Yep. That’s a lot more fuel in the same period of time compared to the 238cc hybrids with 80% tips. There is way more going on there than just a tip change – but that is a subject that I won’t discuss in detail.

Now – Take this information and run it through the same process I ran the hybrid data through….

HP and TQ curve:



NOW I’m not here claiming any HP numbers, but this is what the data says. I limited the torque to 1200ft-lbs to show something that might be possible to make live. Note that even doing these limitations the peak of the HP line happens roughly 1000 RPMs higher. The limitations to peak HP are occurring because we passed the point where the max quantity of fuel can be injected. Faster injectors have helped move the curves farther up the RPM band, but they are not fast enough to move the peak any farther up. As the technology continues we will be able to move that peak even farther up the RPM band.

What about the guy that doesn’t want all that fuel, and just wants a good driving truck? What does this mean for you?

Lets take those fast fuel mods and run them on a “standard” 238cc hybrid. :D



It maxes out the fuel quantities for a much larger portion of the 3d graph simply because there is no more quantity to be had. Lets take that and look at what a theoretical HP and TQ curve:



NOW that’s what I am talking about. That would make one nasty, drivable, and fairly competitive truck in some classes. Torque was held to a level where a “stock” bottom end would live, but that says nothing of balancing, valve train, engine clearances to run RPM, etc…

Verification of data….

Take at look at Nate’s dyno sheet:



Now he is running the injectors that the 455cc flow graph was generated from. While on the dyno he was only using about 1.5-1.6 ms of PW throughout the run based on OBDII data. (Charlie – yes I know… need to verify with a scope… I agree, but it hasn’t happened yet)

Here is the theoretical chart based of off 1.6ms of PW using the flow data from the injectors:



Not perfect, but close enough to say that the data works for peak HP. If I were to massage the torque curve differently then I could get closer there too, but its not worth it for what I would like to show. The truck was not really tuned in and was having some wastegate issues that are now resoved. (I think anyway... Nate would have to confirm that.....)

Take it for what its worth. The data is showing that we are making progress. And I think we have made a lot in recent times, but there is a lot yet to go. I have no idea what happens to the HP/cc ratio does when nitrous is added…. I assume that moves the value up substantially.

Discuss.
 
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#6 ·
:whs: I like where this thread is going. :D

Jason what rpm limit do you think would be good to run with these faster injectors? 4500ish? That would seem to be fairly doable with just bolting in springs and pushrods, correct?

Dave
 
#11 ·
"FAST" injectors are just injectors that have been modified to increase the rate of delivery. That includes a tip change and several internal modifications. Every internal modification was made and flow tested and we picked up fuel rate every time using the exact same tip.



IMHO running 4500ish RPMs regularly without doing valve reliefs is dangerous. I know many will probably disagree with me but there is not enough piston to valve clearance in these motors even in stock form to sustain those RPMs. I know there are some pictures out there of a stock motor that was torn down that had lots of extended time at higher than average RPMs while running down the interstate and lots of piston to valve contact was the result. But that is another discussion for another thread.

:rockon: Awesome info looks like the injector/rpm fueling issues have been resolved? What about the FDCS @ higher rpms? In your HP/TRQ graphs what PW are you using to make the 800hp with the 455's? Also, why just 2500psi ICP for the fast injectors? Sorry for all the questions and thanks for informative post!

Man I want another seven three SO bad...
I wouldn't say all the issues have been resolved. We are leaps and bounds behind.... :( But we are getting there! None of this information takes into account the electronics beyond the FDCS signal limitation. If you decide to inject fuel in a meaningful duration the FDCS signal doesn't start to bother you until you get very high.... All of these graphs were built using a maximum injection window of 45* of crankshaft rotation. That time period was calculated for each RPM then 0.5ms was added to it to give a commanded injection duration. All of the PWs used to generate those graphs are capable of fitting into the FDCS signal at the RPMs they were used at.

800HP takes place at 2.375ms of commanded injection.

Grrrr.... stupid graphs..... the last labeled ICP is 2500, the next increment is 3000. I know I fixed that once so everything is labeled.... Anyway last line on that axis is 3000psi ICP.
 
#9 ·
what are these "fast fuel mods" you speak of? good work.
 
#10 ·
:rockon: Awesome info looks like the injector/rpm fueling issues have been resolved? What about the FDCS @ higher rpms? In your HP/TRQ graphs what PW are you using to make the 800hp with the 455's? Also, why just 2500psi ICP for the fast injectors? Sorry for all the questions and thanks for informative post!

Man I want another seven three SO bad...
 
#14 ·
Very Nice Jason!!! As Matt Stated, my truck was having issues, wastegates that were blowing open, intercooler tubes blowing off, shredding silicone hoses, etc.... All in all, I was pretty impressed with the runs it put down for the issues we were having with it that night. We are slowly working on those issues to get them resolved.

IMHO, I think we have a lot more work to do before I hit the 800HP mark, but I can guarantee that there is plenty of fuel in my injectors to make it capable of 800HP when the rest of the truck is prepared for it.

I feel fairly confident that these injectors can even be made fairly "streetable"... I wouldn't go so far as to say that you could tow with them, but I have been driving my truck everyday since we got it done, and I still average about 15-16MPG in town. Granted I'm only weighing in at 5800lbs, and I'm not drag racing it from every stop light, but still I was not expecting to see even that good of a result being easy on it...

I will not go into a lot of details about the injector internals, just to state that a lot of time and massage work goes into them to make them work right and be balanced.
 
#15 ·
I have a question to propose to some wondering about Fast injectors and high HP injectors.

If a standard P7100 Plunger and barrel assembly is 12mm in diameter and you can get around 600 cc's with it, then why do they make 17mm plunger and barrel assemblies for? And when they put the 17mm plungers in, why is it that they are not looking to inject any more fuel quantity?

P.S a 17mm Plunger and barrel assembly is capable of 1700cc's
 
#20 ·
Except supposing nothing breaks in the pump, there wont be quite the sacrifice. Id imagine the pump will consume a bit more hp to run, as it is pushing on more fuel, but it is not relying on an hydraulic ratio to compress the fuel that is sprayed into the cylinders. Rather i would compare it to a b-code, except running 17mm pump would be something like a f-code, if it existed.
 
#21 ·
I think it would be interesting to see someone go to the trouble of making a 4mm larger plunger setup than what is being used in hybrids today unless someone already has, seems it is only logical. :shrug:
 
#22 ·
I would think after reading the hints about the12mm and 17mm plunger, this is what was done along with other things. It makes sense, if the plunger only has to move x amount of space to push x amount of fuel, you change the size of the plunger and it will now push out x more amount of fuel or the same x faster. The sacrifice is Atomization, but does a p-pump worry about that when tweaked?
 
#40 ·
YEAH! and what happened to SMART ASS as well LOL! Good stuff guys keep it coming!
 
#28 ·
Jason

Once you get the injectors going take a good hard look at the pulses in the fuel rail and oil rail and I think you will find your answers as to why things work and not work. We used accumulators that need to be tuned each time a fueling change was made to settle things down when the flows got up and the time when down. Just think of what happens when the oil starts moving one direction and suddenly stops! Same thing goes for the fuel.

Looks like your making good progress and I believe you are going the right way. There will be some limits as to how fast you can get things to refill that you are going to need to watch out for when things are all up to temperature in th ehead, good luck.
 
#30 ·
Jason

Once you get the injectors going take a good hard look at the pulses in the fuel rail and oil rail and I think you will find your answers as to why things work and not work. We used accumulators that need to be tuned each time a fueling change was made to settle things down when the flows got up and the time when down. Just think of what happens when the oil starts moving one direction and suddenly stops! Same thing goes for the fuel.

Looks like your making good progress and I believe you are going the right way. There will be some limits as to how fast you can get things to refill that you are going to need to watch out for when things are all up to temperature in th ehead, good luck.
Steve, do still have the TTC, and Hutch data/archives on the accumulators? I think I got some from Haul_N_Horses also. I have been able to find bits and pieces, but most of that work and data has vanished into the digital void. A shame really.

Jason, An accumulator as an HX can dampen the shock waves running up and down the rails - may help.
 
#34 ·
The simplest way I can put it is that it matters big time! A properly adjusted accumulator showed no less than a 30 - 40 Hp gain peak, cooler EGT's and the injector noise was reduced. Until you sit and work with a running engine and do the work you just will not understand it. Cylinder pressures all evened out and the spikes between cylinders that moved with RPM as to when and where they occurred basically got cut in half.

If you think the injectors do not care about the fluctuation then you have not understood what's happening at all. The more fuel the injector flows the worse the problem becomes. Take a look at what happens when 2 injectors in the same rail try to fill at near the same time and then over lay that with cylinder pressure and it may open your eyes. There was a lot of work that went into all this and it was proven not only by myself but TT and International as well. Split shots made these issues much worse due to the double pulse each injector put into the rails.
 
#44 ·
I don't have my white coat on but I think your talking harmonics correct? I know that applies to gasses in boosted atmospheres. It is also found in Hyd's. Anything that reduces "bad harmonics" increases flow so I see your point.
 
#36 ·
We tried several that we found and ended up making them. Understand nothing was ever put together into a kit, just like when we came up with the return fuel system, we just told everyone what we found and let them go about it themselves. The easiest one was nothing more than a billet housing with a plunger inside that sealed with O-rings. Used a light spring and air pressure for tuning. The idea was that once figured out we could find a spring to do the job. TT took it further than that and found some that he installed on customers trucks but once Doug got sick everything pretty much stopped. After that no one cared about it too much so it all died with the few trucks that both of us had done. I haven't looked at this stuff for years but still know how much it matters to the HEUI system.
 
#39 ·
OK I managed to find a few (and only a few) of the things I have laying around. There was a lot of stuff on both accumulators on both the fuel and oil sides of the rail. The Hydac were one HP oil accumulator used.
http://www.fluid-flow-control.com/glued-gas-bag-original-mercier/glued-gas-bag-original-mercier.html

http://www.hydacusa.com/accum/diaph.htm

http://www.mcmaster.com/#hydraulic-accumulators/=28z1e4

I also found a captured thread that does capture the fuel rail accumulator and some of the tuning it in the attached PDF

And some Hydac cat PDF pages on accumulators and dampers



From Hutch:




 

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#37 ·
the accumulators are basically a mechanical arrester . An air arrester is a shock absorber in the plumbing inside a house that keeps your pipes from jumping around inside the walls and tearing themselves up . I could see where that kind of pressure pushing a fluid through tubing could certainly tear some crap up when the flow was stopped immediately .
 
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