E38 Fuel Pressure settings on returnless stock LS3, no FPCM, but using 65psi ZL1 pump

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10-20-2023
88mdok

E38 Fuel Pressure settings on returnless stock LS3, no FPCM, but using 65psi ZL1 pump

I'm running a stock crate LS3, stock injectors etc, FPCM not installed/disabled. (601: FPCM Fitted: No).

Therefore I am assuming the E38 would otherwise be expecting a default 58 psi at the fuel injector rail.

However I am using a ZL1 pump assembly which puts out 65 psi (448kpa) hard wired to 12 volts so I am assuming it will be putting out full capacity at all times at the rated 65psi via the regulator built into the drop-in pump assembly.

I seem to be running rich, so I am assuming the ECU is expecting 58psi at the rail but as it is actually getting 65psi it is likely dumping a good 10% too much fuel in at any point and also for any adjustments/calculations it is trying to perform to self-correct the problem.

So I have now changed:

Engine, General
Injector Control, Rail Pressure
13541: Rail Pressure Min to 448kPa
13542: Rail Pressure Max to 448kPa

Fuel System, Fuel Pressure
Desired Fuel Pressure
7033: Normal to 448kPa
7030: High Flow to 448kPa
7031: Low Flow to 448kPa
7032: Cold Engine to 448kPa
7034: Default to 448kPa
7035: Fail to 448kPa

Are these the only fields I need to change? I would assume I don't need to change 12307 Injector Flow Rate Vs Pressure Delta as I am using the stock 42Lbs injectors. I have seen some users shifting this table to the left three cells to help solve this same problem. I have not attempted this potential fix yet though, because my thinking tells me that this table/curve should be left alone and elsewhere it should be told 65psi is incoming.

With the FPCM disabled, does the E38 default to expecting 58psi at the rail no matter what I change? Or have I in fact made the right changes (as shown above) to have it believe it is receiving 65psi?

Note I'm only just doing the startup tunes at the moment. Has been going ok so far. It could very easily be something else in my tune creating the rich result.

Thanks,
Matt
10-21-2023
Alex14SS

Quote:

Originally Posted by 88mdok

I'm running a stock crate LS3, stock injectors etc, FPCM not installed/disabled. (601: FPCM Fitted: No).

Therefore I am assuming the E38 would otherwise be expecting a default 58 psi at the fuel injector rail.

However I am using a ZL1 pump assembly which puts out 65 psi (448kpa) hard wired to 12 volts so I am assuming it will be putting out full capacity at all times at the rated 65psi via the regulator built into the drop-in pump assembly.

I seem to be running rich, so I am assuming the ECU is expecting 58psi at the rail but as it is actually getting 65psi it is likely dumping a good 10% too much fuel in at any point and also for any adjustments/calculations it is trying to perform to self-correct the problem.

So I have now changed:

Engine, General
Injector Control, Rail Pressure
13541: Rail Pressure Min to 448kPa
13542: Rail Pressure Max to 448kPa

Fuel System, Fuel Pressure
Desired Fuel Pressure
7033: Normal to 448kPa
7030: High Flow to 448kPa
7031: Low Flow to 448kPa
7032: Cold Engine to 448kPa
7034: Default to 448kPa
7035: Fail to 448kPa

Are these the only fields I need to change? I would assume I don't need to change 12307 Injector Flow Rate Vs Pressure Delta as I am using the stock 42Lbs injectors. I have seen some users shifting this table to the left three cells to help solve this same problem. I have not attempted this potential fix yet though, because my thinking tells me that this table/curve should be left alone and elsewhere it should be told 65psi is incoming.

With the FPCM disabled, does the E38 default to expecting 58psi at the rail no matter what I change? Or have I in fact made the right changes (as shown above) to have it believe it is receiving 65psi?

Note I'm only just doing the startup tunes at the moment. Has been going ok so far. It could very easily be something else in my tune creating the rich result.

Thanks,
Matt

Hey Matt,

using a ZL1 pump assembly on a stock LS3 is interesting. The stock E38 is indeed expecting around 58 psi, but you're pushing 65 psi with that ZL1 pump. This higher pressure can certainly lead to the engine running richer because the ECU isn't expecting that much pressure, and consequently, more fuel is being delivered.

Now, I see you've adjusted settings in HP Tuners, specifically the 'Rail Pressure' and 'Desired Fuel Pressure' parameters to 448 kPa to match the 65 psi from the pump. That's a good move. By doing this, you're essentially telling the ECU, "Hey, expect more pressure because that's what's coming."

As for the Injector Flow Rate Vs Pressure Delta, since you're using stock injectors, you might be on the right track by leaving it as is. This table is more about how the injector behaves rather than the pressure. Changing it might introduce more complications, and we want to avoid that.

With the FPCM disabled, the ECU probably defaults to expecting 58 psi, yes. But by changing those pressure settings, you've redirected its expectations. So, in theory, it should now be looking for that 65 psi you're supplying.

However, there's more to consider. Even with these changes, if it's running rich, you might want to take a look at other factors. Check the MAF calibration. A mis-calibrated MAF can send incorrect air volume data to the ECU. Also, peek at the O2 sensor feedback. If they're malfunctioning or sending skewed data, the ECU might think it's leaner than it actually is and compensate by enriching the mixture.
10-21-2023
88mdok

Quote:

Originally Posted by Alex14SS

Hey Matt,

using a ZL1 pump assembly on a stock LS3 is interesting. The stock E38 is indeed expecting around 58 psi, but you're pushing 65 psi with that ZL1 pump. This higher pressure can certainly lead to the engine running richer because the ECU isn't expecting that much pressure, and consequently, more fuel is being delivered.

Now, I see you've adjusted settings in HP Tuners, specifically the 'Rail Pressure' and 'Desired Fuel Pressure' parameters to 448 kPa to match the 65 psi from the pump. That's a good move. By doing this, you're essentially telling the ECU, "Hey, expect more pressure because that's what's coming."

As for the Injector Flow Rate Vs Pressure Delta, since you're using stock injectors, you might be on the right track by leaving it as is. This table is more about how the injector behaves rather than the pressure. Changing it might introduce more complications, and we want to avoid that.

With the FPCM disabled, the ECU probably defaults to expecting 58 psi, yes. But by changing those pressure settings, you've redirected its expectations. So, in theory, it should now be looking for that 65 psi you're supplying.

However, there's more to consider. Even with these changes, if it's running rich, you might want to take a look at other factors. Check the MAF calibration. A mis-calibrated MAF can send incorrect air volume data to the ECU. Also, peek at the O2 sensor feedback. If they're malfunctioning or sending skewed data, the ECU might think it's leaner than it actually is and compensate by enriching the mixture.

Hi Alex14SS thanks for the response.

Yes you are probably right on the MAF calibration. I'll check that out.

On the O2 sensors, these could also be a culprit. They are just some cheap and cheerful imported junk from an ebay seller. Still, scanner is showing voltages as expected on these.

I guess my biggest question here is am I pointlessly going around in circles trying to use this 65psi pump assembly if the e38 will in no way be able to be set to expect anything other than 58psi whenever the FPCM is disabled. As you have said, it would seem as if what I have changed is heading down the right path, but I'm hoping someone with a definitive answer can chime in and give their opinion/experience on if I am making the correct settings changes (not saying your opinion is invalid, by the way!).

Oh and I'm using it because I built my own fuel tank out of aluminium and I was able to get the full drop-in pump assembly with level sender and a weld-in aluminium ring/mount on sale for less than a standard 58psi hanger assembly without the weld-in mounting ring. My thinking at the time was a combination of "getting more pump for less" and "future proofing for further horsepower upgrades later down the line". Perhaps it is now causing more problems than what it is worth....
10-21-2023
gtstorey

There is a reason oems put a way to regulate pressure. I would expect pressure to not be very steady just free flowing based upon voltage. What happens when the voltage goes up or down? What happens when the pump gets a little age on it?
10-21-2023
blindsquirrel

I would just shift the injector data tables (move everything 2 columns to the left so that the 448kPa data ends up in the 408kPa column). Both Flow Rate vs Press & Offset vs Press vs IGNV. I am pretty sure that all those rail pressure fields are ignored when FPCM Fitted = No.

I'm assuming this is a late 128-768 axis file, so if it's something else then I look like an idiot. Thanks for not posting this file you are working with. You'll get better, more specific answers if you do. And also show that you respect the folks you're asking for help.
10-21-2023
obthomas

LS3 injectors are rated at 42# per hour at 60 PSIG. The flow from these injectors for our purposes is directly proportional to the square root of the pressure. Flow rates and pressures meeting this criteria are what is in the flow vrs pressure table. As long as you are operating within the confines of this table the E38 knows the flow based on the pressure. If you tell the E38 there is a fixed pressure of 65 it interpolates the table to get the new flow. The best thing you can do is make sure that the flow is 42 at 60(rated) and then that the flow at 65 psi is also correct. Use the HPTuners unit conversion tool for injector flow to check this.

The reason I got into this thead is I just finished a LS3 project with an E38 and a fixed 55 psi fuel pump. With all my adjustment efforts and experience I am completly confident in what I said above.
10-21-2023
blindsquirrel

Quote:

Originally Posted by obthomas

With all my adjustment efforts and experience I am completly confident in what I said above.

...and if your posts were longer, I'd swear you were a kingtal0n sockpuppet account.
10-21-2023
88mdok

1 Attachment(s)

Quote:

Originally Posted by blindsquirrel

I would just shift the injector data tables (move everything 2 columns to the left so that the 448kPa data ends up in the 408kPa column). Both Flow Rate vs Press & Offset vs Press vs IGNV. I am pretty sure that all those rail pressure fields are ignored when FPCM Fitted = No.

I'm assuming this is a late 128-768 axis file, so if it's something else then I look like an idiot. Thanks for not posting this file you are working with. You'll get better, more specific answers if you do. And also show that you respect the folks you're asking for help.

Hi blindsquirrel, thanks for the response and info.

I'll give the shifting of these two tables a try. I Wanted to try those fields mentioned in my original post first as I thought this may have been the quick/easy/simple fix without the complication of muddying up the waters on my tables. However it is my sneaking suspicion that as you have said, all those fields may actually be ignored when 601 FPCM Fitted = No.

I have attached the tune file now. Sorry I was unaware attaching tune file was a "must do" around these parts. I thought my question was a simple enough one. But oh well, I'm a newb so I don't mind learning, being wrong etc. Note the file does not yet have the "shifted tables" done yet. I'll do that in the next attempt.
10-21-2023
88mdok

Quote:

Originally Posted by gtstorey

There is a reason oems put a way to regulate pressure. I would expect pressure to not be very steady just free flowing based upon voltage. What happens when the voltage goes up or down? What happens when the pump gets a little age on it?

Agreed. Which is why they use something like their FPCM. I however don't want to have to use that module.

I'm pretty sure I mustn't be the first person using an e38 to want to tell it that something other than 58Psi is incoming, for whatever reason.
10-21-2023
88mdok

Quote:

Originally Posted by obthomas

LS3 injectors are rated at 42# per hour at 60 PSIG. The flow from these injectors for our purposes is directly proportional to the square root of the pressure. Flow rates and pressures meeting this criteria are what is in the flow vrs pressure table. As long as you are operating within the confines of this table the E38 knows the flow based on the pressure. If you tell the E38 there is a fixed pressure of 65 it interpolates the table to get the new flow. The best thing you can do is make sure that the flow is 42 at 60(rated) and then that the flow at 65 psi is also correct. Use the HPTuners unit conversion tool for injector flow to check this.

The reason I got into this thead is I just finished a LS3 project with an E38 and a fixed 55 psi fuel pump. With all my adjustment efforts and experience I am completly confident in what I said above.

obthomas, thank you for your response.

Assuming my injectors are performing as designed and that I'm working within the confines of the table for the correct flow rate versus pressure, how exactly, in your project did you "tell the E38 there is a fixed pressure of 55..." ?

You have stated that you are confident in your efforts that this has worked, but you haven't exactly said HOW you told it about the 55 incoming. Was it altering some of the fields in my original post? Was it altering 12307: Injector Flow Rate vs. Pressure Delta ? Perhaps some other field or table I have missed?
10-21-2023
gtstorey

Quote:

Originally Posted by 88mdok

Agreed. Which is why they use something like their FPCM. I however don't want to have to use that module.

I'm pretty sure I mustn't be the first person using an e38 to want to tell it that something other than 58Psi is incoming, for whatever reason.

There are simpler ways of regulating pressure than FPCM. This is probably an ideal place for a Corvette regulator. If you aren’t going to regulate, then you need a good way of monitoring pressure from now on. I seems to me like this is a good way to go just lean enough at WOT to hurt something.
10-21-2023
gtstorey

Sorry, I just reread your original post and didn’t realize that there is a regulator built into the pump assembly.

But you still need to confirm pressure at WOT as you get there,
10-22-2023
obthomas

Quote:

Originally Posted by 88mdok

obthomas, thank you for your response.

Assuming my injectors are performing as designed and that I'm working within the confines of the table for the correct flow rate versus pressure, how exactly, in your project did you "tell the E38 there is a fixed pressure of 55..." ?

You have stated that you are confident in your efforts that this has worked, but you haven't exactly said HOW you told it about the 55 incoming. Was it altering some of the fields in my original post? Was it altering 12307: Injector Flow Rate vs. Pressure Delta ? Perhaps some other field or table I have missed?

Fuel/general/rail pressure minimum 13541 and fuel/general/rail pressure max 13542 were set at 55 psi. My logged injector flow is sensitive to these rail pressure settings. Good luck.
10-22-2023
88mdok

Quote:

Originally Posted by obthomas

Fuel/general/rail pressure minimum 13541 and fuel/general/rail pressure max 13542 were set at 55 psi. My logged injector flow is sensitive to these rail pressure settings. Good luck.

Ok so as you are running 55 and default is 58 did you shift any tables to the right ? Or no tables shifted and only these two fields altered?
10-22-2023
88mdok

4 Attachment(s)

I shifted the two tables two columns to the left.

Wrote the tune and it is running much better now. Not as rough and also not "hunting" around as much to keep stable RPM. Also my eyes aren't burning in the garage with fuel in the air.

So I think we are onto a winner. Note that I don't conclusively know if it is the table shifting to the left or the fields 13541 and 13542 set to 448kPa that have made the desired effect.

I have attached the tune and also some of the latest logs if anyone is interested to peruse.

Note that I noticed my crank relearn had not been done. I did that process restarted and cleared codes on the latest most log and that seemed to clear the crank relearn code. It is not showing any more on scans.
10-23-2023
obthomas

Quote:

Originally Posted by 88mdok

Ok so as you are running 55 and default is 58 did you shift any tables to the right ? Or no tables shifted and only these two fields altered?

Shifting the flow vrs pressure table to the left or right has the effect of changing the injector size. Remember your injectors are RATED at 42#/hr at 60 PSI. Shifting is like applying an offset. It has an effect and it may apply just what you need to make the engine run to your satisfation. In my case I changed fuel pressure rather than shifting the flow table.
10-23-2023
obthomas

Quote:

Originally Posted by 88mdok

I shifted the two tables two columns to the left.

Wrote the tune and it is running much better now. Not as rough and also not "hunting" around as much to keep stable RPM. Also my eyes aren't burning in the garage with fuel in the air.

So I think we are onto a winner. Note that I don't conclusively know if it is the table shifting to the left or the fields 13541 and 13542 set to 448kPa that have made the desired effect.

I have attached the tune and also some of the latest logs if anyone is interested to peruse.

Note that I noticed my crank relearn had not been done. I did that process restarted and cleared codes on the latest most log and that seemed to clear the crank relearn code. It is not showing any more on scans.

By moving your injector table to the left you now have the table for a 44.3#/hr at 60 psi injector instead of 42#/hr at 60 psi. The computer is going to shorten the pulse length allowing for the extra flow that is not really there and lean your running kinda like an offset.
10-23-2023
radrace19

Quote:

Originally Posted by 88mdok

Agreed. Which is why they use something like their FPCM. I however don't want to have to use that module.

I'm pretty sure I mustn't be the first person using an e38 to want to tell it that something other than 58Psi is incoming, for whatever reason.

No, your not the first. Most use a kit by Vaporworx to correct the pump fuel pressure regulator.
Regulator adapter to use a standard 2002 Camaro fuel pressure regulator or
the drop in regulator
-Greg
10-23-2023
Alvin

Quote:

Originally Posted by radrace19

No, your not the first. Most use a kit by Vaporworx to correct the pump fuel pressure regulator.
Regulator adapter to use a standard 2002 Camaro fuel pressure regulator or
the drop in regulator
-Greg

This looks like a good idea.

I think the CTSV and ZL1 sending units basically have a safety pop off valve (its set high on the CTSv assembly)
10-23-2023
carlc

The safety overpressure valve in all Gen5/SS cars is 85psi. If battery voltage is applied to the fuel module the pressure will vary from 85psi to something much lower at WOT depending on fuel demand. Using it this wayjust won't work well. Converting to the regulation method mentioned by Greg above works if manifold referenced fuel pressure is not needed and if a reduction in pump life is acceptable. Using either the OEM FSCM or a stand-alone PWM controller with the ZL1 fuel module is much preferred.

The C5 FFR is not recommended for any modern fuel module (Gen5, CTS-V2, Gen1-3 Coyote, etc.) unless there is a return tube that goes back into the lower reservoir. There are conditions where the lower reservoir will run dry when run on an external regulator without the return going back to the reservoir.

The primary job of the safety overpressure regulator is to keep hot key-off fuel pressure under 85psi. Heat soak from then engine (even on cold days) will cause the fuel line pressure to exceed 200psi. I have witnessed conditions where car owners swear that there is no fuel pressure when in reality their hot rail mounted fuel pressure gauge needle has swung 360* and is resting against the stop peg, hence looking like 0psi. This is not good for lines or fittings, but above 100psi the injectors stop working. Above 100psi across the injector and it just can't open/close, so the car won't start. 85psi is high enough to stay out of the normal operating pressure of the FSCM (the electronic pressure regulation system) but low enough to allow the injectors to work on hot days/low cranking voltage conditions.

Though the CTS-V2 does have a similar safety overpressure regulator, it has a 74psi rating for reasons having to do with the FSCM. There are higher pressure regulators available from DW, but the FSCM might become unhappy with a stock calibration, and for sure when the higher power DW300 pumps are installed. There are ways to cure these conditions.