HP Tuners Supercharged LS1 misfires when switching to Power Enrichment

Hey Guys,

I have a supercharged LS1 that has come my way. Engine is in a Nissan Patrol with the factory auto trans. Factory ecu, Tuned using HP tuners.

Eaton M122 Supercharger with 76mm pulley. Fuel system is dead head. No boost reference. Fuel pressure tests as steady during a dyno run.

Low speed and light throttle there is no issues. Full throttle no issues.

At or near 40% throttle the moment PE is switched in HP tuners scanner multiply misfires occur. Back off the throttle and drop into closed loop no miss.

This only occurs when the RPM is between 2000 and 3000.

Log and Map attached.

In the log at 17.30 is where the misfire started. happy to hear any suggestions.

Darren,

The log appears to be 7 min 20 seconds long so I'm not sure where you're directing us with "17.30", but I've looked at both time you get into PE.

In the second instance I see the transition, RPM drops which may be the misfire you mentioned. The spark and fueling behavior seem excessive given low load and that can cause misfiring.

In the first instance, over 20% enrichment occurs without an increase in load or RPM. At 85 kpa MAP and low RPM, AFR in the 11s is excessive.

I would try bringing some enrichment in progressively with MAP and RPM via the open loop EQ ratio table, then bring PE in at higher load, and reduce the enrichment ramp value so the additional fueling PE brings happens as less of a step change.

The 10 degree timing advance reduction when MAP goes from 95 to 105 kpa also seems perhaps a bit much, and potentially a factor in the misfiring, but start with the fuel side first to be extra cautious and then try less of a sharp drop in timing after. It's possible you needed that to avoid knock because the fueling behavior was in need of adjustment.

Hey Mike,

Yes the log is 7minutes and 20 seconds long. I have attached a screen shot that shows the 17.30 I was speaking of. It is a time stamp

Screen shot attached.

The first occurrence is very quick, The second is longer as I held the miss to get more data. 17.30:18 or 5:30 and 18 seconds.

The RPM drop is when the mis occurs.

The information you have provided is very helpful.

I can see two EQ ratio tables One under the open loop / base and the other under power enrich.

Doing a Map compare both of these table are identical to LSA tables.

EQ ratio open loop @ 85kPa is 1.08 giving an AFR of 13.54

EQ ratio PE @2500rpm is 1.25 which equals 11.7 AFR. This is the commanded AFR in the log when the mis occurs.

I an unsure as to which table will allow the PE to be adjusted to come in at higher load. Maybe you can point me in that direction.

The EQ ratio PE looks like a good table to adjust first, given the AFR commanded of 11.7. Image attached of first and only adjustment to the map.

Once tested I will confirm the results.

Darren,

I know it's a bit confusing, totally not your fault. It's a quirk of the program. At the bottom of the screen, below the strip chart down on the line that says Duration: 7m 20s, you should also see "Time" followed by two sets of numbers with a comma between them. The first set will be different for me vs. you when we open the same file and doesn't start at 0, so it isn't helpful when trying to let someone else know where to look. The second set of numbers, the one to the right of the comma, starts at 0, so it works fine for giving someone a point of reference. For example 17.30 doesn't exist when I open the file because when I open it, the first time (left of the comma, and visible at the bottom of the strip chart like you showed) starts at 2:23, ends 2:31 since the log is a little over 7 minutes long. The RPM drop issue occurs at 6:29 into the log, which should match up for you, but only if you're looking all the way at the bottom, at the second set of values right of the comma where it says "Time:" Hopefully that clears things up, I know it's a bit odd.

You found the tables I mentioned which is great. The interpolation change you made to PE amounts is a good test.

PE enables based on the enable values which are listed in the "Enable" section of the Power Enrich tab. You have Min MAP set really low so it's basically always enabled, and then when you hit the Min Torque value PE is going to occur since both enable conditions are met. You can raise the Min Torque amount or the Min MAP if you want PE to occur at a higher load.

Ideally you want to ease enrichment in as load increases rather than dumping all the fuel in all at once, so that's where slowing it by reducing the enrichment ramp value can help.

Hey Mike and anyone reading this,

Been playing with this one still.

I added 20% to the Cold power enrich, No change.

Tried 10% same table, No change

EQ ration gas linearized 2000-3200, No change

Changed the enrich ramp in to 4 seconds from 2 seconds, No change

Change EQ gas ratio to 1.165 from 2000 up to 2800, No change

Changed EQ gas Ration to 1.13 from 2000 up to 2800 No change or very slight change.

Didi not think it was a good idea to go any leaner.

Issue occurs between 40 and 60% throttle

Have not had it occur about 60% throttle or below 40% throttle

As much as it does not seem to make sense this is starting to look like a spark issue.

Plugs are new, I had swapped the coils we some from a naturally aspirated car that was running ok.

Why coils might been an issue at 50% throttle but not above 70%. Maybe a cylinder pressure thing?

In the log 8.5 is where the issue is happening at 50% throttle. 33.8 is no issue @ 70% throttle.

I will let you know if coil make a change.

Darren,

An enrichment rate of 2.0 is still about 100x greater than what GM uses in stock form on some engines, so I understand you had it even higher before, but be aware the value is still so high that the enrichment ramps in so quickly that it's practically all at once.

In this log you if you graph injector pulsewidth for cylinder 1, you can see what looks like a straight vertical wall of fuel from PE hitting all at once. That happens right where the misfire starts.

Adding widebands (1 per bank) and logging them alongside the ECU data via the MPVI unit will help illustrate what that sudden fuel change is doing to air/fuel ratio. Wideband data is also required for proper tuning under load anyway, since the stock sensors aren't usable in that condition, so getting 1 wideband per bank set up to log is your best next step.

Then you can log the current behavior, make changes, and see which direction things are heading in, how far you are from where you need to be, etc.

On a related note, transient tuning should only be performed after steady state tuning at all areas is complete, because a portion of the issue may be related to MAF or SD airflow calculation not being accurate in the area you're transitioning through in these logs. Without widebands, you don't know if that's tuned correctly yet or not, so I'd get the widebands, tune the full range of operation via MAF and SD separately, re-enable both, then tune transients.

Hey Guys,

The resolution to this issue was to go to a file prior to the OS 1 Bar patch being applied.

The OS 2 Bar patch was applied that has Power enrichment and Boost enrichment. This was set up from scratch with the 3 Bar map sensor data and injector data.

The file was scaled as required and tuned. The fault is no longer present.

Still curious to know exactly why the issue was occurring with the original file but at least I know how to fix.

Darren,

Ah gotcha. With a 2 or 3 bar MAP sensor, and boost, the 1 bar patch isn't suited.

1 bar would be for naturally aspirated setups with 1 bar MAP sensors.

I'm glad you got the right patch loaded and are having better results!