LQ4 Tuning Help

[btagg]

I just finished putting a 2004 LQ4 into my 1972 k20 with an nv4500 transmission. I am using the stock PCM with a BP automotive speed density only harness (no MAF) as well as the DBW pedal and the TAC Module from the same wrecked pickup. I used the built in HP tuners software upgrade to run a 1 bar MAP in speed density mode. I did install a sloppy mechanics stage 2 cam with the following specs: 228/230 .585"/.585" 112 LSA. Everything else about the engine is stock. The pickup starts, idles, and runs good and I have put around 100 miles on it so far. I could use some advice on how to make it more drivable.

The issues:

1. At low rpm and low speed just off idle (driving through a parking lot) the engine will surge and get the whole pickup "bucking" until you shove in the clutch slip the clutch a bit to keep the engine closer to 1200 rpm.
2. At any rpm above around 2000 when shifting, the rpms are slow to fall even when not touching the throttle making it slow to shift into the next gear.
3. The last and probably most significant issue is that when coming to a stop light when you push in the clutch to coast the last 10 feet or so, if you do not give it any throttle the engine will drop rpm and most of the time it dies.

Attached are the most recent tune from the computer and a datalog of the last trip I made with the pickup. Any advice on what tables or values need to be changed to make this pickup more drivable would be greatly appreciated.

- Brett

Attachment 145890
Attachment 145891

[edcmat-l1]

You did not attach your files correctly.

[btagg]

You did not attach your files correctly.

Does this work?

[edcmat-l1]

Does this work?

Yeah looks like you got it.

[edcmat-l1]

Your VE is completely original. I can tell just by looking at it. You need to plot your trims, which is the percentage the fueling off, and apply the correction to your VE table.

The closer you get to ideal, the better it will run. There will be a bunch of other crap that needs done but this is the most important.

trims, VE off.jpg

[blindsquirrel]

Your VE is completely original.

Nope! You just need to add a few decimal places...

screenshot.04-05-2024 13.59.51.png

[edcmat-l1]

Nope! You just need to add a few decimal places...

screenshot.04-05-2024 13.59.51.png

Oh my gosh you're right! I did a compare and I was off a country mile!! LOL

difference.jpg

[btagg]

Your VE is completely original. I can tell just by looking at it. You need to plot your trims, which is the percentage the fueling off, and apply the correction to your VE table.

The closer you get to ideal, the better it will run. There will be a bunch of other crap that needs done but this is the most important.

trims, VE off.jpg

Okay, copied the LTFT values and added those the Primary VE table and did a little of interpolation between values to fill smooth it out a little. This is what the table looks like now. Does this look more like a proper table?

I appreciate the help and if you couldn't tell, I know just enough to be dangerous.

- Brett

[5FDP]

Two things I want to say.

What is your fuel system like. Return or returnless? What is your fuel pressure?

And you need larger injectors on a 6.0 with a camshaft that size. It's going to run out of head room above 5,000rpm.

[edcmat-l1]

Okay, copied the LTFT values and added those the Primary VE table and did a little of interpolation between values to fill smooth it out a little. This is what the table looks like now. Does this look more like a proper table?

I appreciate the help and if you couldn't tell, I know just enough to be dangerous.

- Brett

Highlight the whole table, hit smoothing once, flash it to the vehicle.

As others will be saying, jumping in here, there's more to it, but this is a start.

[btagg]

Two things I want to say.

What is your fuel system like. Return or returnless? What is your fuel pressure?

And you need larger injectors on a 6.0 with a camshaft that size. It's going to run out of head room above 5,000rpm.

I am running an AEM 50-1005 (400 lph) pump and a holley fuel pressure regulator/filter combo with a return to the tank. I tested the fuel pressure at the rail and had 60 psi.

- Brett

[btagg]

Highlight the whole table, hit smoothing once, flash it to the vehicle.

As others will be saying, jumping in here, there's more to it, but this is a start.

Went for a drive and repeated this process and now all my long term fuel trim values are single digit numbers that seem far more reasonable. It does seem to be running a little smoother however I can't really tell a difference in the surging issue or the engine dying when rolling to a stop.

What would be the next area yall suggest looking at and working on?

- Brett

[blindsquirrel]

Is Holley's filter/regulator like most of their products, where they simply take a Chinese copy of a commodity item like a stock replacement filter for a 99-03 Corvette and put it in a Holley box and price it at 3 times what the same thing would cost you at the parts store if it came in a Champ or Airtex box?

Because the return orifice inside the stock replacement filter/regs is too small to flow enough return fuel back to the tank with pumps larger than 255LPH.

[btagg]

Is Holley's filter/regulator like most of their products, where they simply take a Chinese copy of a commodity item like a stock replacement filter for a 99-03 Corvette and put it in a Holley box and price it at 3 times what the same thing would cost you at the parts store if it came in a Champ or Airtex box?

Because the return orifice inside the stock replacement filter/regs is too small to flow enough return fuel back to the tank with pumps larger than 255LPH.

It is essentially just a stock replacement with -6AN ends brazed onto the intlet and outlets. I did check the fuel pressure at the rail and without the engine running it had 60 psi which I understand is about what it should be.