Return Style System with ID1300 - WOT Fueling WAY OFF

So I am using ID data for the ID1300x2 that I have (I realize there is now newer data, but its not that much difference).

I have a dual 450lph Fore pump, 10an feed, 8an return, Aeromotive 1000 regulator, Fore rails, 1300x2 injectors.

My WOT area of my VE table is down in the low 90's at 19psi of boost on my 426ci 4.5L whipple setup, something is very wrong with the fueling. I am getting way more fuel than the ECM thinks I am.

Anyone else experience this? The low VE is putting me in strangly low aircharge spots in the timing tables, which causes me a headache on the dyno.

Vacuum multiplier is all 1's
Data is copy and paste in the injector tables from ID

I will post the tune a little later, just wanted other's feedback. WOT I am around 10-11ms injector timing, .78 lambda on MS109.

By vacuum multiplier, are you talking about the row axis of the offset table?
fuel>general>offset?

On my 2016 Scat (stock tune) it is the same from 0 to 100kpa, which seems incorrect.

Is your pressure regulator referenced to manifold pressure?

Yes, regulator is boost and vacuum fed, my vacuum multiplier table is all 1?s

Try unhooking the vacuum reference and (carefully) make some runs and see if that is indeed the issue.

What exact table are you talking about that is all 1s?

I found 2 that could be the table you're talking about.
fuel>general>offset
and
fuel>open loop/base>pressure dif mult (I think it's called Vacuum on some other applications)

Clearly taking 19psi of fuel pressure out of my system will bring the fuel delivery way down. Not looking to do that.

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Originally Posted by 06300CSRT8

Clearly taking 19psi of fuel pressure out of my system will bring the fuel delivery way down. Not looking to do that.

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Jordan fwiw I have never run a boost referenced FPR on any of my boosted Hemi's for this reason. Never saw the need when I always had enough injector to just fuel it directly, accounting for the fuel going in the motor.

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Originally Posted by HemiC

Jordan fwiw I have never run a boost referenced FPR on any of my boosted Hemi's for this reason. Never saw the need when I always had enough injector to just fuel it directly, accounting for the fuel going in the motor.

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Gotcha, interesting. There is something to be said about the spray pattern at varying pressures. I am no expert, but my "training" always told me the generally a higher pressure and short pulsewidth produces a more even fuel spray pattern than lower pressure and longer pulsewidth. Probably negligible. My system is setup to run up to 3 pumps for max effort e90 or higher fuel, so for now i will just play around with the tune to keep it mechanically running the same (i.e. boost referenced).

are you getting the AFR's you want with the low 90's VEs? depending on the cam, that doesn't sound TOO "wrong" for the short runner whipple setup....

The VE in the tune is all referenced to manifold pressure, not atmosphere, so once you get to ~1.0 pratio, the VE itself is going to flatten out quite a bit (unless you have the most absurd cam overlap possible). It's probably more likely that the ID flow tables for the fuel rail pressure you are using is off....

I guess my main issue is as I?m chopping away at the VE, I?m bringing my airflow calcs (used in timing) way way down, lower than stock, which means each time I lower my VE I go lower in airflow which ends up being HIGHER timing, very bad to control all of that.

Yes I?m getting the AFR I ultimately want

Quote:

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Originally Posted by 06300CSRT8

I guess my main issue is as I?m chopping away at the VE, I?m bringing my airflow calcs (used in timing) way way down, lower than stock, which means each time I lower my VE I go lower in airflow which ends up being HIGHER timing, very bad to control all of that.

Yes I?m getting the AFR I ultimately want

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Very peculiar, all of this. You'd think that as long as the injector data were accurate and there were no modifier/multiplier tables mucking around with your airflow or fuel flow model that VE would at least stay very similar to the 1.0 PRatio loadpoint as load increased from there. And it seems (theoretically, at least) that the 1:1 rrpfr should warrant a 1.0 multiplier in the Fuel Mass Vacuum Multiplier table. But, just to throw a monkey wrench in the system, let me toss this at ya.

Mopar engineers developed a S3 turbo kit for the Dodge Neon SRT-4 that used its own Mopar calibrated PCM, and a rising rate fuel pressure regulator that was integrated into the fuel rail. You'd hook the vacuum line up to your intake manifold, at atmospheric pressure you'd have 58 psi fuel pressure, in vacuum it would decrease at a 1:1 rate, and in boost it would increase at a 1:1 rate. Just like the regulators we use in the aftermarket, only the Mopar design was done via a deadhead method (no return line).

It came as quite a surprise to me that, despite fuel pressure maintaining a 4 bar pressure differential regardless of manifold pressure, they still used that Fuel Mass Vacuum Multiplier table. It's interesting, however, that they use a different "Zero Point" (1.0 multiplier load point) compared to the stock, static fuel pressure calibration. The rate of increase/decrease per unit of vacuum is also a bit different, though not by a huge margin.

Here's a comparison of a Mopar S3 calibration against a stock calibration:

Attachment 92127

Might be worth playing around with.

Thanks, I had a S3 SRT4 back many moons ago and recall that exact setup.

One question that I just thought about, since the S3 calibration has a higher number in boost (-150kpa I am comparing) this leads me to believe the vacuum multiplier table is actually telling the ECM how much the fuel system supplies versus it being actually used as a multiplier. If it was a true multiplier, the S3 calibration SHOULD in theory have a lower number, as it is supplying more fuel than an S1-S2. Wouldn't you agree?

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Originally Posted by 06300CSRT8

Thanks, I had a S3 SRT4 back many moons ago and recall that exact setup.

One question that I just thought about, since the S3 calibration has a higher number in boost (-150kpa I am comparing) this leads me to believe the vacuum multiplier table is actually telling the ECM how much the fuel system supplies versus it being actually used as a multiplier. If it was a true multiplier, the S3 calibration SHOULD in theory have a lower number, as it is supplying more fuel than an S1-S2. Wouldn't you agree?

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Not sure I grasp your question. Looking at the s3 calibration, it has its boost range up into -175 kpa vacuum (or, as any normal person would label it, 175 kpa boost), while the stock calibration is scaled up to -150 kpa vacuum (150 kpa boost). I still don't get why they scale the vacuum range past 100 kpa, as absolute vacuum seems like it would simply be 100 kpa vacuum.

I have verified in the past that this table is definitely a multiplier, and has a direct impact on fueling. I've frequently tweaked this table for high boost setups on Neons that run upwards of 30 psi boost. Unfortunately, the table can only be scaled up to -250 kpa vacuum (250 kpa boost), but it still provides a bit more of a normal looking VE table when using this table to compensate for the pressure differential changes on static pressure fuel systems.

Simple....

Lets use the -150kpa multiplier...

So if you say your tune commands 500mg of fuel mass based on VE and pressure ratio, the vacuum multiplier would be 1.265 for a stock car and 1.414 for a S3 car. So the S3 car commands more fuel overall, even though it has the benefit of higher fuel pressure? I would think the multiplier would need to be less, not more, for a car with rising fuel pressure.

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Originally Posted by 06300CSRT8

Simple....

Lets use the -150kpa multiplier...

So if you say your tune commands 500mg of fuel mass based on VE and pressure ratio, the vacuum multiplier would be 1.265 for a stock car and 1.414 for a S3 car. So the S3 car commands more fuel overall, even though it has the benefit of higher fuel pressure? I would think the multiplier would need to be less, not more, for a car with rising fuel pressure.

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Gotcha. I'll have to verify what my thought process has been on this when I get home from work today. Have a Neon in for tuning that I need the get started on. I'll work on verifying the boost vs vacuum region of the vacuum multiplier map first and report back when I have conclusive data.

thanks, really appreciate it. My guess is the stock values should be used as a reference point, and change by percentage from there.

SO my stock values are damn near close to 1.000 at zero vacuum, and go to 1.013 by -10 kpa but that's it. I would assume the ECM is going to extrapolate that out past -10kpa to whatever boost I am running, which I can solve for based on the couple cells I have and figure out a slope. My guess is by setting to all 1.000 I have actually reduced the amount of fuel called for versus my stock values. This would make sense given the huge increase in fuel pressure in my system, but maybe its not as simple as zeroing out the factors (i.e. setting to 1.0).

My only guess is the injectors fuel flow isn't linear across dynamic pressure, i.e. increasing rail pressure by 10psi does not equate to having 10psi more manifold pressure hitting the injector tip. Its plausible, but I would think others would have already found this issue.

Quote:

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Originally Posted by 06300CSRT8

thanks, really appreciate it. My guess is the stock values should be used as a reference point, and change by percentage from there.

SO my stock values are damn near close to 1.000 at zero vacuum, and go to 1.013 by -10 kpa but that's it. I would assume the ECM is going to extrapolate that out past -10kpa to whatever boost I am running, which I can solve for based on the couple cells I have and figure out a slope. My guess is by setting to all 1.000 I have actually reduced the amount of fuel called for versus my stock values. This would make sense given the huge increase in fuel pressure in my system, but maybe its not as simple as zeroing out the factors (i.e. setting to 1.0).

My only guess is the injectors fuel flow isn't linear across dynamic pressure, i.e. increasing rail pressure by 10psi does not equate to having 10psi more manifold pressure hitting the injector tip. Its plausible, but I would think others would have already found this issue.

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OK, went out and verified some things.

1) A value of anything greater than 1.0 (for example 1.10) is an open loop fuel mass multiplier. In the case of a value of 1.10, it means it adds 10% fuel mass. And, of course, the inverse is as you would expect. Any value less than 1.0 decreases the amount of open loop fuel mass delivery.

2) The negative kpa values are boost, the positive kpa values are vacuum. Hence why the table is labeled vacuum. Vacuum is already a negative, thus a negative value in this instance equates to positive pressure (boost).

As far as your extrapolation theory is concerned, I would assume that anything that runs out past the range of the load axis will just use the last known value. So, if your boost reference ends at -10 kpa vacuum, then any boost over 10 kpa will continue to use the multiplier value of the -10 kpa vacuum breakpoint.

Thanks very much, very helpful.

I guess in my instance I am a bit stuck because I have two of three variables unknown to start and cannot develop a good VE table. I believe I have good injector data, and would have to estimate my VE which is tough to do, then tweak the vacuum multiplier until fuel is close, then fine tune the VE across rpm ranges.

It seems like the way to approach this is to unhook the manifold pressure reference to the fpr and then dial in the VE.

Then hook up the manifold reference and dial in the vacuum correction.

But why do the 2nd step if you don?t need to?

Is that table even for scaling injector flow in this application?