ICP Duty Cycle only 79.5%?

[GreenF350]

Here is the short version of my question....Why on my "120hp" tune does my ICP run between 1700 and 2100psi, but my duty cycle "pegs out" at 79.5% and doesn't go any higher?

The background info....I knew my HPOP wasn't doing everything that was being asked of it, but since I am really close to pulling the trigger on some injectors and tunes to go with the head studs, Valve springs, etc that are sitting in my garage waiting to go on I figured I would check it out and see how it was doing. I have one of the Scan Gauges and did a full throttle run from about 55-90. The ICP showed right at 2000psi +/- 300psi and the duty cycle steadily climbed until it got to 79.5% and then it stayed there for the rest of the run. I'd say a new/upgraded HPOP is in my future, but I was just wondering why the duty cycle never went higher? I find it hard to believe that my "120hp" tune only calls for 2000psi at WOT, so is it a case of the gauge not reading correctly or do I have another issue to look for? Truck runs fine, so no obvious issues.
-Aaron

 

[Rideracelivemx7]

its not that your tune is only calling for that PSI its that your pump is basically very weak and cannot keep up.i would highly suggest looking for a upgraded pump in the near future expecially if you want larger injectors. and as far as the DC% the tuning may only let the pump call for so much as like safe mode I guess so it doesn't hurt itself. ive seen DP tunes on stage 2s drain my buddies pump the 89% DC. that straining the pump something fierce. basically you want a lower DC%. like if you held 3100PSI at 30% then you have tons of room to grow

 

[littleredstroker]

its not that your tune is only calling for that PSI its that your pump is basically very weak and cannot keep up.i would highly suggest looking for a upgraded pump in the near future expecially if you want larger injectors. and as far as the DC% the tuning may only let the pump call for so much as like safe mode I guess so it doesn't hurt itself. ive seen DP tunes on stage 2s drain my buddies pump the 89% DC. that straining the pump something fierce. basically you want a lower DC%. like if you held 3100PSI at 30% then you have tons of room to grow

Where with mine 44% is 3200 so I'm about out.

Smoked a bit
Turbo lit
That was it

 

[GreenF350]

as far as the DC% the tuning may only let the pump call for so much as like safe mode I guess so it doesn't hurt itself. ive seen DP tunes on stage 2s drain my buddies pump the 89% DC.

That's pretty much what I was looking for. An explanation at to why it was ONLY getting 79.5% duty cycle with that low of a pressure. I don't totally understand why you would want to limit to any particlar duty cycle, but I DO understand why it's low and the solutions to it, etc. A new HPOP is on the list as well, along with some traction bars, but the list is never complete and there is always something else to do. :morons: Thanks!
-Aaron

 

[lincolnlocker]

How many miles on pump? Also could have a hpo leak somewhere allowing it to bleed off and not hold psi.

live life full throttle

 

[GreenF350]

How many miles on pump? Also could have a hpo leak somewhere allowing it to bleed off and not hold psi.

live life full throttle

It has 265,000 miles or so on it. It is more than likely just worn out.

 

[lincolnlocker]

It has 265,000 miles or so on it. It is more than likely just worn out.

Not nesisarily, how long has it been tuned and how has it been driven its entire life? In your op, you said at wot it would hold 2000psi give er take 300psi... does that mean it would jump up and down from 1700psi to 2300 psi or would hold a steady pressure anywhere in that range? All it will take to make a hpop work harder is a torn hpo oring. Could be anything from the hpo sysem that seals with an oring.

live life full throttle

 

[JAP]

Tunes generally don't go to 100% because it causes drivability issues if I remember correctly. If your ICP is that low, a pump will really wake your truck up.

 

[lincolnlocker]

Tunes generally don't go to 100% because it causes drivability issues if I remember correctly. If your ICP is that low, a pump will really wake your truck up.

As long as there are no other issues like im trying to sort out before everyone jumps on the, just buy a pump wagon.

live life full throttle

 

[GreenF350]

Not nesisarily, how long has it been tuned and how has it been driven its entire life? In your op, you said at wot it would hold 2000psi give er take 300psi... does that mean it would jump up and down from 1700psi to 2300 psi or would hold a steady pressure anywhere in that range? All it will take to make a hpop work harder is a torn hpo oring. Could be anything from the hpo sysem that seals with an oring.

live life full throttle

It has been tuned since before I bought it at 132,000mi. Had an Edge on it when I bought it and I put a DP Tuner on it almost right away. I've paid fairly close attention over the last 7-8 years or so and know those tunes aren't the best, if for no other reason than their age. (Not looking to get into the tuner argument, just by the time there was any discussion against Jody's tunes I had been running them for so long I figured any damage had more than likely been done and they had run good for me.) It has been well maintained, oil changes and all, but it does get driven pretty hard. I'm not afraid of the skinny pedal and it used to do some mudding before I bought my ATV's. I keep pretty close tabs on it and can say for certain it doesn't have an external leak and any other issue would have to have come on slowly over time because I haven't really noticed the change.

As for the 300psi fluctuation...it doesn't really jump around, it looks about the same as it does when the duty cycle is climbing. I'm using the Aeroforce ScanGauge for the readings and can't remember how often it records the data, but it takes about 3 or 4 data points of ICP dropping before it starts back up for about the same number of data points. I can only record 2 parameters at once and had ICP PSI and ICP DC% selected. I'm pretty convinced it just can't keep up, but could take a look at a few things if you guys think something might be amiss and have suggestions.
-Aaron

 

[lincolnlocker]

Ok thats a better explanation... now I would say that you could use a hpop... buuutt if you still have the original stock injectors in it then those alone with that many miles on could be wore out also!... and that you more then likely will gain some hpo psi back with a new hpop, it might not be where it should be because the injectors could be worn.

live life full throttle

 

[GreenF350]

Ok thats a better explanation... now I would say that you could use a hpop... buuutt if you still have the original stock injectors in it then those alone with that many miles on could be wore out also!... and that you more then likely will gain some hpo psi back with a new hpop, it might not be where it should be because the injectors could be worn.

live life full throttle

Yeah, the injectors are still hanging in there, but show their age a bit. No specific problems, just "not as good as it used to be". Starting to get tempermental in the cold mornings (down on power until warmed up a bit), etc. That's a big part of the reason for the upgrades now, but I've been planning them for awhile. I wasn't particularly concerned with the pressure, but didn't understand the DC being "capped" at 79.5%. THanks for the reassurances.
-Aaron

 

[lincolnlocker]

Dc isnt capped.. the higher the dc the harder the pump is working to maintain the psi that its putting out... if you already plan on doing injectors you can swap them also to narrow it down to what it is causing the low hpo.. change the hpop and see just jow much you pick up then swap inj..

live life full throttle

 

[GreenF350]

Dc isnt capped.. the higher the dc the harder the pump is working to maintain the psi that its putting out... if you already plan on doing injectors you can swap them also to narrow it down to what it is causing the low hpo.. change the hpop and see just jow much you pick up then swap inj..

live life full throttle

If the DC isn't limited as mentioned by Rideracelivemx7 in the second post, then that takes me back to my original question. Why does the DC steadily climb until it gets to 79.5 and then stay at EXACTLY 79.5 until I let off the throttle? Is my "120hp" tune really only calling for 2000psi @ WOT over 2000rpm? I would think if that was the case the DC would wiggle around a bit and not stay RIGHT at 79.5%. That doesn't seem right to me either and might give me a reason to look for another problem. :shrug:

The ScanGauge can only read the commanded/requested IPR Duty Cycle, not actual DC correct?
-Aaron

 

[littleredstroker]

If the DC isn't limited as mentioned by Rideracelivemx7 in the second post, then that takes me back to my original question. Why does the DC steadily climb until it gets to 79.5 and then stay at EXACTLY 79.5 until I let off the throttle? Is my "120hp" tune really only calling for 2000psi @ WOT over 2000rpm? I would think if that was the case the DC would wiggle around a bit and not stay RIGHT at 79.5%. That doesn't seem right to me either and might give me a reason to look for another problem. :shrug:

The ScanGauge can only read the commanded/requested IPR Duty Cycle, not actual DC correct?
-Aaron

My scangauge seems to show actual. With a ipr issue, I was seeing 65-70 %

Smoked a bit
Turbo lit
That was it

 

[CurtisF]

It's really not going to matter at all if DC is 79%, or 95%. You won't see a bit of difference in actual ICP. In fact, it will still sit at around a max of 2000psi just like you currently see.

As a reference, bone stock tuning limits ICP DC to 64%. Going much over that only gives you very minimal gains in ICP on a stock HPOP.

Furthermore, there's always a lot of "your HPOP is weak, get a new one" or "there must be something wrong with the truck" thrown around in threads like this. In reality the pump isn't weak, instead the pump is flowing exactly the amount of volume it's designed to flow. There's nothing wrong with your truck either.

It's the tuning calling for too much pulse width at WOT in the higher HP tune. The pump simply can't supply that oil volume at that requested pulse width.

Want to test that? Aaron, have your Scangauge monitor pulse width and do a WOT run on that tune and report back what the pulse width is. I'll bet you and everyone here it's way over 4ms.

To put it simply.... it's not the pump and it's not the duty cycle. What's really happening is oil hungry split shot injectors are being called by the tuning to stay open for far too long. Report back on what the Scangauge is reading for PW.

 

[mandkole]

^^^Bingo...

You've got 8 'gates' (the injector poppet valves) that are letting oil pressure out during each injection event as the pump is trying to fill the rails. Those gates are being held open for a long time in this tuning scenario (for stock AD injectors on max effort).

You also must consider the oil that is 'leaking' past those gates (worn injector poppets, injector orings) . At 2500+ rpm, 4ms+, worn parts, there is a lot of oil volume that must be recovered (in this application) by the pump and its not happening. The pump is not 'working' any harder (its running regardless), it just has the IPR at full closed for max supply. For this application, the pump must have an output of a far greater amount than other applications (hybrids/large nozzles on short PW tuning) or system sealing condition.

After about 60%, for all intents/purposes, its maxed out anyway-- asking for 80+% isnt doing anything more.

**the above is for illustrative purposes, not intended for absolute technical accuracy