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Old 10-05-2017, 11:39 AM   #1
me78569

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Vp44 Injector Pop Pressure theory and testing

At the advice of @jlbayes I decided to post up some questions for the injector builders to answer. I don't know what kind of response I will get but it is worth a shot.

I have been wondering for awhile what the result of increasing pop pressure would be. there has been a lot of " not worth it" "lope idle" " stalling in gear" talk, but never much beyond "don't do it because I know best" with no real explination as to why.

There is also a lot of thoughts from the other side saying that increased pop pressure will help atomize fuel better on big injectors. They theory makes sense, if you increase the hole size but keep the pressure static then you in theory loose the ablity to atomize fuel as efficently. I have experienced this direcetly as the first set of 7 x .009's I got from DFI were set at ppump pressures. Those things smoked like crazy regardless of situtation. I sent them back to him and got them repoped and that resolved the smoke issues.

So I made the jump from some 7 x .009's from DFI, I was very happy with them, to a set of 7 x .012's vco at 330 bar from DAP.

I wanted to know if I could control the injectors well enough to make them %100 dd friendly, tow friendly, and emissions friendly.

I have been running them now for ~ 1 week. I have the Quadzilla tuned to remove nearly all the smoke in all situtations ( to the point where I will pass emissions no prob). I thought I would have to offset timing to compenstate for the later pop pressure, but I see no reason to at this point. I don't think the extra 20-30 bar is effecting timing near as much as people say it would. you can sort of feel the difference until ~1200 rpm, but beyond that you would never know the difference.

Here's a WOT take off to show the resulting tuning, there are plenty more videos and datalogs of the videos, but I don't see a need to junk up the thread.
7 x .012 330 bar Quadzilla Tuning - YouTube

What I have found is that I am able to throw a good bit more fuel at the truck with the 7 x .012's offidle than I was able to with the 7 x .009's without exceeding stoic limits for haze turning into smoke. I am forced to believe that per mm3 of fuel injected the bigher pop pressure injectors are atomizing fuel more efficently.


So the main question I have is, given what I have found so far, what prevents the builders from setting pop pressure higher? If you are a builder, have you actually tested the results of setting injectors at a higher pop pressure? I can't believe increasing pop pressure causes stress on the pump considering the vp44 can build ~1600 bar worth of pressure.

Comments? Insights? Insults? Anything more than "just get better injectors"?

Last edited by me78569; 10-05-2017 at 11:41 AM.
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Old 10-05-2017, 11:55 AM   #2
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Quote:
Originally Posted by me78569 View Post
If you are a builder, have you actually tested the results of setting injectors at a higher pop pressure?
Yes.

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Originally Posted by me78569 View Post
So the main question I have is, given what I have found so far, what prevents the builders from setting pop pressure higher?
Experience.
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Old 10-05-2017, 11:59 AM   #3
me78569

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Originally Posted by Smokem View Post
Experience.

which I have faith in. but no insights into what that experience taught you?


Did you not find any difference in offidle smoke? Did you find a negative effect? throw me a bone here, what did you find as a negative effect of higher pop pressure?
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Old 10-05-2017, 12:13 PM   #4
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There is also a lot of thoughts from the other side saying that increased pop pressure will help atomize fuel better on big injectors.
Your confusing atomization with intensity, a quality nozzle with quality orifice finish will atomize very well even at 200BAR.

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Did you not find any difference in off idle smoke? Did you find a negative effect? throw me a bone here, what did you find as a negative effect of higher pop pressure?
Idle smoke is usually caused by the nozzle type and/or cone angle. Opening pressure set too high will do as you said earlier; cause loping and stalling issues. The fact of the matter is the higher the opening pressure, the duration event is shortened and overall less fuel is injected.
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Old 10-05-2017, 12:19 PM   #5
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something like every 10 BAR is minus 1 degree of timing ish.

something to consider is the total amount of fuel injected. if the pump has to work harder to get the injector to open the process starts later and ends sooner. this will limit the total fuel injected. by how much? I have no idea but it will. the injection pump will be working harder to push less fuel out in a shorter amount of time. that fuel will be more atomized but at what cost... that cost will be power and reliability. when you could have a high quality component that works within stock pressures that delivers fuel better than a stock tip ect ect.

personally I like the benefits of being a few BAR over stock pressures. things just seem to work a bit better. but going 30,40,50 BAR over OE specs is going to have ill effects on how the system works.
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Old 10-05-2017, 12:20 PM   #6
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dang it. he beat me. thats what I get for proof reading

Last edited by turbo2387; 10-05-2017 at 12:22 PM.
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Old 10-05-2017, 01:52 PM   #7
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Quote:
Originally Posted by Smokem View Post
Your confusing atomization with intensity, a quality nozzle with quality orifice finish will atomize very well even at 200BAR.
Do some 6 x .13 atomize fuel as efficently at say, 300 bar, as 6 x .011? Or is there is a reduction in how well the injector atomizes fuel under low load as injector size increases?


Why were my injectors at ppump pop pressure so much more smokey than the injectors set at proper vp44 pop pressures?

My assumption, of what you will say, is that the DFI nozzles are low quality causing it to be subject to issues when pop pressure is incorrect?

That is a perfectly acceptible answer, I just want to make sure we are on the same page.


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Idle smoke is usually caused by the nozzle type and/or cone angle. Opening pressure set too high will do as you said earlier; cause loping and stalling issues. The fact of the matter is the higher the opening pressure, the duration event is shortened and overall less fuel is injected.
offidle smoke is what I am talking about, in the 900-1200 rpm range. That's the region where it seems that vp trucks struggle to clear smoke on bigger injector trucks. Again I am not talking about in the pure HP world, I am talking about trying to make a vp44 truck run as clean as a CR truck at a higher hp than we could a few years ago with control of the fueling and timing.

So if I am not encountering any issues with stalling or loping is there really a downfall that I am unaware of? Considering my goals are not all out power. It wouldn't bother me if I lost 50 hp as a result of pop pressure being to high. consider also I have wife that would not be happy with spending money on the POS that is my truck hahaha.

Thanks for the insight it is helpful into the situtation. I am sure you are sick of hearing about it by now haha.



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something like every 10 BAR is minus 1 degree of timing ish.
I see no evidence to support this. I can set my idle timing to whatever I want on command. The truck could care less between the 330 bar and the 305 bar injectors. After watching / datalogging timing commands for the last year my ears can tell a 2* difference that these injectors should have according to the above, but I just dont hear the difference. That's gonna sound hard to believe, but I can reliably tell where timing is at by sound now.

Do you have evidence to support this claim of 1* per 10 bar?


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personally I like the benefits of being a few BAR over stock pressures. things just seem to work a bit better. but going 30,40,50 BAR over OE specs is going to have ill effects on how the system works.
Can you go into more detail on this statement? How did you define where the "limit is" for upping injection pressure? What made you think "this is better" but that is "worse" ?



I completely understand quality trumping all, I was more curious about issues as a result of upping pop pressure. Is increasing pop pressure on low quality injectors a cheap why to help with idle haze, offidle smoke, and the other issues that seem to go hand in hand with cheap big injectors?
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Old 10-05-2017, 02:11 PM   #8
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you see no evidence because you have never played with it yourself. by having about 10 sets of injectors in this truck in about a years time all ranging from 260-300 bar and just playing with it you can figure a little bit out on what works best. no hard proof though just real life time and $$$ spent.

if you delay the injection event you retard timing. simple as that. period there is nothing to argue.

a slightly higher pop pressure has always given me better idle and right off idle driving characteristics. unless it is the wrong hole count or spray pattern. too much of a good thing is almost always bad. you can tune slightly higher pop pressure into static timing (12V) by raising the timing. want 20* with 280BAR injectors set to 22* and you get the benefits of better off idle with slightly better low end compared to the same injectors at 260 bar and 20* timing. but at some point in pop pressure things will not even out and you will start to see noticeable negative effect. your truck ran like garbage with 260 bar injectors because it was opening almost 600PSI lower than what the ECM wanted it to.

Last edited by turbo2387; 10-05-2017 at 02:12 PM.
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Old 10-05-2017, 02:32 PM   #9
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you see no evidence because you have never played with it yourself.
....I am running 330 bar right now. So yes I am playing with it.

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if you delay the injection event you retard timing. simple as that. period there is nothing to argue.
Not argueing that, I am saying there is no evidence I can find to say there is a 1* difference per 10 bar. Upping pop pressure does retard timing, it's how much that is up for debate. From what I have seen it is not as significant as 1* per 10 bar. I very much doubt my delay time has changed more than .5*

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your truck ran like garbage with 260 bar injectors because it was opening almost 600PSI lower than what the ECM wanted it to.
Yep I get that.

So think about this more, if the system is not designed to handle 50 extra bar, why is it that guys run vp pop pressure on a ppump swapped truck with no issues?

I see no difference in ppump swap guys running vp pop pressures and me running 330 bar. Shouldn't the same rules apply? I beleive the p7100 builds pressure faster than a vp, but you are talking nearly double the bar increase going from 260 bar to 305 bar as going from 310 bar to 330 bar.

Sure there is fuzzy math going on but plenty of guys run 45 bar over stock on a ppump without issues.
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Old 10-05-2017, 02:54 PM   #10
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So think about this more, if the system is not designed to handle 50 extra bar, why is it that guys run vp pop pressure on a ppump swapped truck with no issues?
A P7100 does not use an electronic governor. I will have to address your other questions later when I have more time.
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Old 10-05-2017, 03:03 PM   #11
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No rush I am still learning and testing.
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Old 10-05-2017, 04:40 PM   #12
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There's a loss in power running vp pressure with a p pump. How sure are you on your injector pressure?

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Old 10-05-2017, 04:56 PM   #13
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Again I am not really concerned about a loss in power, the point in the test is not to find out what HP does. The test was purely to see if increasing pop pressure could help to clean up cheaper / affordable big injectors on a vp truck. I got the 7 x .012's so that I would have more fuel than I needed so I could afford to back down the fuel rather than ramping it up to get the ~400 hp I had before with the 7 x .009's + wiretap.

The point stands that people run vp injectors on ppump trucks all the time with no issues. Spec of ppump is ~260 bar, spec of vp injectors is 310 bar. My 20 extra bar is considerably less than the 50 bar difference.

I am pulling the oem fueling command down by %35 offidle, this gives me a ton of room to work with in terms of commanding the right amount of fuel at the right time.


My total fueling as it sits is about perfect, my 351VE is sitting at 120,000 rpm at 35 psi and 40 DP. EGT's are hard to top 1200*F and i am very happy with my power, driveablity, towing, and spool.

I called and talked to Jacob about it. He and his builder understood my goals and what I wanted to test. The invoice had a note on it saying 330 bar and then there was also a sticker on the bag saying 330 bar.

Last edited by me78569; 10-05-2017 at 04:58 PM.
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Old 10-05-2017, 06:00 PM   #14
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7x12's at 35psi on a he351ve?????

Oh my.
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Old 10-05-2017, 06:02 PM   #15
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That's plenty of injector for the turbo for sure.


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Old 10-05-2017, 06:11 PM   #16
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Quote:
7x12's at 35psi on a he351ve?????

Oh my.
Like I said I am pulling fuel down signficantly. Rather than using smaller injectors, like the 7 x .009's and maxing wiretap, I am using bigger injectors and reducing the duration so that at the peak of the map of the turbo I am asking for %100 duration from the vp.

The result is a turbo that is in it's map, nice to drive and no smoke or egt issues. Please explain to me the downfall here?

I guess I need some "street cred" to not be looked down upon....
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Old 10-05-2017, 06:15 PM   #17
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Originally Posted by turbo2387 View Post
a slightly higher pop pressure has always given me better idle and right off idle driving characteristics.
This is due to higher intensity of the fuel penetration into the cylinder.

Quote:
Originally Posted by me78569 View Post
Do some 6 x .13 atomize fuel as efficently at say, 300 bar, as 6 x .011? Or is there is a reduction in how well the injector atomizes fuel under low load as injector size increases?
A smaller orifice will always create smaller fuel droplets, and as fuel density increases it requires more intensity to ignite early in the combustion event or at low engine speeds.

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Originally Posted by me78569 View Post
Why were my injectors at ppump pop pressure so much more smokey than the injectors set at proper vp44 pop pressures?
My opinion on this is simple, you don't know all the facts. Unless you verified the nozzles to be the same, tested the injectors before/after, and removed and installed them yourself, you are making an assumption to some degree and the resulting difference is invalid.


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So if I am not encountering any issues with stalling or loping is there really a downfall that I am unaware of?
No. I typically set them at an area that creates success for the broadest range of circumstances, if someone is willing to experiment and understands that it may require alterations in the future, anything is possible.
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Old 10-05-2017, 06:16 PM   #18
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Everybodys very happy varies i guess. I hated my 7x12's with a 475 at 70psi. I couldt imagine them on a stocker.
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Old 10-05-2017, 06:17 PM   #19
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Originally Posted by me78569 View Post
The test was purely to see if increasing pop pressure could help to clean up cheaper / affordable big injectors on a vp truck. I got the 7 x .012's so that I would have more fuel than I needed so I could afford to back down the fuel rather than ramping it up to get the ~400 hp I had before with the 7 x .009's + wiretap.
I don't quite understand how buying two sets of "cheaper" injectors is more cost friendly than one good set, it costs three times as much to do something twice.
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Old 10-05-2017, 06:35 PM   #20
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A smaller orifice will always create smaller fuel droplets, and as fuel density increases it requires more intensity to ignite early in the combustion event or at low engine speeds.
Got ya. Makes sense as well. So in theory increasing pop pressure, if no other issues crop up as a result of that increase, should result in better low rpm situtations such as right offidle? This does not mean the injector as a whole will perform better.


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My opinion on this is simple, you don't know all the facts. Unless you verified the nozzles to be the same, tested the injectors before/after, and removed and installed them yourself, you are making an assumption to some degree and the resulting difference is invalid.
I %100 agree with that.


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No. I typically set them at an area that creates success for the broadest range of circumstances, if someone is willing to experiment and understands that it may require alterations in the future, anything is possible.
That makes sense and is good business.

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don't buy stuff twice
Normally I would agree Smokem, the situtation is not normal though in terms of cost and I won't get into that. You are right, but it does not apply to my situtation.

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Everybodys very happy varies i guess. I hated my 7x12's with a 475 at 70psi. I couldt imagine them on a stocker.

stocker on your truck does not equal stocker on my truck. My truck requirements are different that yours. The he351ve runs great with the 7 x .012's and I have zero issues meeting the requirement of the truck. If you want to come drive my garbage and tell me that my setup is not good then you can. until that point you should consider a less pessimistic view.
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