Vp44 Injector Pop Pressure theory and testing

There are plenty of ways to get more power out of a smaller injector yet minimize low engine speed smoke. I tend to think about ways to create something like this for different applications quite often, and to be honest for a VP equipped engine I'm not sure I would use anything other than a modified factory 7-hole VCO nozzle.

If you will scroll up you will see wherei noted not everybodys (runs great) is the same. Some run horrible but their owners feel differently. To each their own. Dont go calling me out for helping you understand. Figure the rest out yourself.

Given that we can pull fueling commands below stock.

Example Data log


I don't see a need to run "smaller" injectors really. In a perfect world you wouldn't need much wiretap on a DD duty vp truck. Wiretap starts to shine in the 2400-3k region when the oem fueling message drops off, the wiretap will help extend that region of the powerband.

what I have found is by using bigger injectors and pulling the fueling command down, rather than the typical up, results in better tps movement resolution compared to before. I no longer have to leave a light using 0-%30 throttle position then roll into to avoid smoke. that %30-%100 throttle is effectively wasted in offidle situtations.

I guess "smaller" is realitive in this situtation. A set of nice 7 hole vco's that are able to flow ~500 hp worth of fuel without smoke issues would be nice.

turbo2387 said:

If you will scroll up you will see wherei noted not everybodys (runs great) is the same. Some run horrible but their owners feel differently. To each their own. Dont go calling me out for helping you understand. Figure the rest out yourself.

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I don't need your help understanding fueling and how much fuel my turbo is "suited" to use with my tuning. my point stands, you have no place to judge how my setup runs.

me78569 said:

Given that we can pull fueling commands below stock.

Example Data log

I don't see a need to run "smaller" injectors really. In a perfect world you wouldn't need much wiretap on a DD duty vp truck. Wiretap starts to shine in the 2400-3k region when the oem fueling message drops off, the wiretap will help extend that region of the powerband.

what I have found is by using bigger injectors and pulling the fueling command down, rather than the typical up, results in better tps movement resolution compared to before. I no longer have to leave a light using 0-%30 throttle position then roll into to avoid smoke. that %30-%100 throttle is effectively wasted in offidle situtations.

I guess "smaller" is realitive in this situtation. A set of nice 7 hole vco's that are able to flow ~500 hp worth of fuel without smoke issues would be nice.





I don't need your help understanding fueling and how much fuel my turbo is "suited" to use with my tuning. my point stands, you have no place to judge how my setup runs.

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Makes sense, also more throttle pedal pulls back on the trans tv lever more and keeps from short shifting.

me78569 said:

I don't see a need to run "smaller" injectors really. In a perfect world you wouldn't need much wiretap on a DD duty vp truck. Wiretap starts to shine in the 2400-3k region when the oem fueling message drops off, the wiretap will help extend that region of the powerband.

what I have found is by using bigger injectors and pulling the fueling command down, rather than the typical up, results in better tps movement resolution compared to before. I no longer have to leave a light using 0-%30 throttle position then roll into to avoid smoke. that %30-%100 throttle is effectively wasted in offidle situtations.

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One of my favorite personal setups was an 8x0.010" VCO nozzle with a bit wider cone angle and a Van Aaken. They were easy to control with the throttle, yet fueled pretty well and got very good mileage with a modified HX35.

Smokem said:

One of my favorite personal setups was an 8x0.010" VCO nozzle with a bit wider cone angle and a Van Aaken. They were easy to control with the throttle, yet fueled pretty well and got very good mileage with a modified HX35.

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I can imagine that would be a good setup.

jasonc said:

Makes sense, also more throttle pedal pulls back on the trans tv lever more and keeps from short shifting.

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Yep, I still use %35-%40 throttle to get the truck moving from the light in normal traffic, but It does not smoke. As boost comes up the fueling does as well and it makes more than enough power. Shift points are not low in the rpm band, unless light on the throttle.


The best part is as a result of pulling fuel down by %35 at 0 psi my cruise control works great. I have no surging or over then under fueling.

me78569 said:

I can imagine that would be a good setup.

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I can tell you in my instance being an '01 automatic, at 300BAR opening pressure the truck would constantly stall going from neutral into reverse, and periodically from neutral to drive. Now oddly enough dropping the opening pressure to 290BAR alleviated this while seemingly not changing any of the other characteristics.

I tested over ten sets in the same truck over a few month time frame, including 6-hole, 7-hole, 8-hole, varying cone angles, VCO, small sac, and large sac nozzles. There were several that I liked, a few I did not, and it made it rather clear what worked best for certain applications.

I had issues with stalling to start but then I edited the quadzillas code to adjust down the fueling % from idle state and the issue went away.

The best I can tell the ecm was command to much fuel causing rpms to spike then the ecm would defuel and the engine would stall. By cutting the % of fuel the ecm was trying to command it resulted in a more stable offidle situation.

The truck has not stalled in 5 days now cold hot doesn't matter.

Well this was a few moons ago and with a Van Aaken reducing fueling percentages wasn't an option. So I guess in short the higher opening pressure could create problems unless someone had the ability and was willing to modify the fueling tables to make it work properly.

Compeltely understandable, You work with what you have and there is more than 1 way to skin a cat.

I will say if I were to do it again, I personally would be tempted to get more out of a smaller orifice at 290BAR.

If I was a rich man I would buy everything needed to start R & D'ing it only to understand it fully.

I find the ideas in injector setup very interesting.


For those thinking the 7 x .012's are too much fuel for the setup I did another video to show that it is %100 possible to control the fueling to the point where the little he351ve doesn't blow. I have no idea how much hp these injectors will flow, but they are very well suited to the turbo and the needs of the truck.

Quadzilla 7 x .012 injectors vp44 valet mode / Anti theft - YouTube


I am not a mindless idiot looking to launch the compressor into space.

At full potential, they are overkill.
I don't typically make it a habit of buying things way over suited for my scenario just to dial things back to make them work. To each his own.


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At full potential, in terms of the max duration canbus tuning can do, the injectors don't push the he351ve out of it's map. If you add more than ~500 us worth of wiretap then you start to see the turbo come out of it's map, as in over 125,000 rpm and drive pressure starts to increase in a non linear fashion. As it sits I am only using 100-200 us of wiretap and only after 2k rpm.

They seem like a good fit to me, :shrug: Not gonna convince anyone though, oh well doesn't matter I suppose. Datalogs of towing and wot driving are all posted if anyone cares to look lol.

I rather enjoy the bigger injectors while not needing max duration right off the bat and needing wiretap to make power in the meat of the powerband. 0.02

I like the idea of running the larger injectors and altering the fuel curve to pull some fuel out of it. From what I know, In gas engines, generally it isn't ideal to run a High % of duty cycles.

It kind of makes sense in that the duty cycle is comparable to the duration commanded by the tuner. In my mind that translates to less wear on the pump. If that even makes sense.

Boy you guys took that and ran with it.


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ill go along with Weston..i have had a few sets of his inj due to my own not knowing what I want. always a wealth if information and spot on
he supplied whats im truck right now..

im in on this one

To each their own. If you guys want to find something in the logs that shows I am vastly overfueled be my guest. They are posted nothing to hide no smoke and mirrors.

as for reducing duty cycle being easier on the pump ...meh maybe or maybe not. I don't see that we are doing damage by maxing the duration and holding it there, but it is a ceiling in terms of tuning that we have to deal with. You can only push canbus so far, before it hits that 4095 limit and you are done. If you can't increase the max then reduce the min...doing so with larger injectors effectively gives you more range to work with.

I don't want or need the max fueling command at %50 throttle and 20 psi I want it at %100 throttle and 30 psi.


I don't think Weston is wrong. I think he builds his injectors to suite the vast majority. I also believe he builds the best you can buy. The thread was not a question as to his quality, rather a question of the reason why pop pressure on vp injectors seems to be limited to a might tighter range than ppump injectors.


It is important to understand that I am not holding fueling down by %35 across the board, only offidle, or at 0 psi of boost. As boost climbs I am increasing my fueling IE: by 20 psi I am asking for oem fueling commands, by 30 psi I am asking for max duration. Its not like I am nuttering the injectors across the board, only down low to keep from smoking out the world if I want to use more than %20 throttle to leave a light.

me78569 said:

I have no idea how much hp these injectors will flow, but they are very well suited to the turbo and the needs of the truck.

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Here is what I will tell you from experience, I have a lot of people send me injectors to look at and the majority of the time they are not what they are supposed to be. Knowing this I would be careful making assumptions as to how something performs unless you are very confident in what it in fact is.

Smokem said:

Here is what I will tell you from experience, I have a lot of people send me injectors to look at and the majority of the time they are not what they are supposed to be. Knowing this I would be careful making assumptions as to how something performs unless you are very confident in what it in fact is.

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This.

We see it almost daily in the turbo game. I can only imagine how the injector game is.

People always tell me how much more power they made on the engine dyno with some harts 5x25s over every other brand and it has always made me wonder how close they actually are to 5x25s.