Turn-on tune: get your LS running
Everything you need to get a swapped LS started, idling and driving gently, step by step, with the values that real tunes run. Then take it to the dyno.
Read this first
This is what has worked for us, not a guarantee for your engine. Every build is different: cam, heads, injectors, fuel, altitude, converter and gearing all change what your engine wants. Use the numbers here as a starting point and let your logs decide.
A turn-on tune gets the engine started, idling and driving gently. It is not a finished tune. We always recommend a dyno tune, or a professional tuner with a wideband, before any wide-open pass. Do not flash it and go WOT. Keep it out of boost and off the top of the throttle until it has been tuned, and stop the moment you see knock, lean air/fuel or a pressure drop (our Don't blow it up checks).
Use at your own risk.
What you'll need
We may earn a commission when you buy through links on this page.
- Tuning interface: HP Tuners MPVI4, the current model (plus credits for your computer; an MPVI3 you already own also works). Budget route for P01, P59 and E38 computers: an OBDX Pro GT (about $140) with free PCM Hammer and TunerPro
- Wideband air/fuel gauge so the logs tell the truth: AEM X-Series wideband or Innovate LC-2
- Fuel pressure gauge for the first start: LS fuel rail test gauge
- Battery charger to top the battery up before each write (unplug it while you write): 10-amp battery charger / maintainer
- Injectors sized for your power: size them with our fuel system tool
Build your turn-on tune sheet
Tell us about your build. You get your turn-on tune step by step: every value it should have, in the order you set them, with the walkthrough step that shows how.
Based on 882 real tunes so far, 32 of them on a cam we can name. This grows as we add tunes.
Read and save your stock file first
Before you change anything, read the computer and keep a clean copy of what came out of it. If a write ever goes wrong, that file gets you back.
Read it with VCM Editor
- Battery fully charged (charge it first, then unplug the charger), key on, engine off.
- Connect your MPVI4 (an MPVI3 or MPVI2+ works too) to the OBD-II port and your laptop.
- In VCM Editor, read the vehicle and let the read finish completely.
- Save it straight away with a clear name, like
2000-camaro-stock-2026-10-04.hpt, and copy it somewhere off the laptop. - Make every change to a copy. Never overwrite the stock file.
Read it on the bench
- Power the computer on the bench with a steady 12.5–14 V supply (about 1 A) or a charged battery.
- Connect your OBDX Pro GT (or a good J2534 cable).
- In PCM Hammer, read the full contents and save the .bin with a clear name. Keep a copy off the laptop.
- Note the OS id it shows: it tells you which XDF to load in TunerPro.
- Edit a copy in TunerPro, never the original.
Step by step: the values a turn-on tune needs
This is the order we set them in. Each step links to the full how-to in our HP Tuners walkthrough.
- Save the stock file and turn off VATS. Read and save the stock file before you change anything, and keep a copy. Turn VATS (anti-theft) off or the engine won't start. Charge the battery fully before every write, and unplug the charger while you write. How →
- Enter the known values. These are facts, not tuning:
- your injectors' real data from the maker;
- displacement;
- stoich for the fuel in the tank (gasoline about 14.7, E10 about 14.1, E85 about 9.8);
- gear ratio and tire size;
- fans;
- a sensible rev limit (6,000–6,200 rpm on a stock-valvetrain truck engine);
- for boost, MAP sensor scaling (GM 3-bar 12223861: linear 329.41, offset -6.35).
- Set the idle. Hot idle target, base idle airflow, idle spark, and cracker/follower so it doesn't stall coming back to idle. A cam is where most turn-on tunes need work. Check what stock looks like for your engine first. How →
- Leave fuel close to stock until you can log. Start with stock power enrichment (lambda about 0.85). Get the MAF or VE close from logs at part throttle before you push it. How →
- Keep spark conservative. Start at the low end of the ranges below, and never add timing without watching knock retard. How →
- First start and gentle drive. Check oil pressure, fuel pressure (about 58 psi on a factory-style LS system), trims within ±10%, and no knock retard. Then drive it gently and log. How →
- Then book the dyno. WOT fuel and spark get dialed in on a dyno, or with a pro tuner and a wideband, not on the street. Our pre-WOT checks →
What real tunes run
Ranges from the real LS tunes we've pulled apart, by computer family and NA vs boost, one tune per build. Where a computer and induction has only a few tunes with a value, the range comes from every tune with the same induction. Where we have 10 or more tunes, the range is the middle 80% of them, so one unusual tune doesn't stretch it. They are what experienced tuners settled on for those builds, not targets for yours. Where an owner reported a problem (a stall, a surge, a weak pull), we left that part of their tune out.
| Setting | Gen III, NA | Gen III, boosted | Gen IV, NA | Gen IV, boosted |
|---|---|---|---|---|
| Hot idle target | 575–950 rpm (median 800, middle 80% of 496 tunes) | 600–900 rpm (median 800, middle 80% of 69 tunes) | 525–900 rpm (median 750, middle 80% of 174 tunes) | 550–1,000 rpm (median 750, middle 80% of 43 tunes) |
| Warm idle airflow (in gear) | 5.8–15.0 g/s (median 9.2, middle 80% of 486 tunes) | 6.0–15.4 g/s (median 9.3, middle 80% of 69 tunes) | 6.5–13.7 g/s (median 8.6, middle 80% of 174 tunes) | 6.2–14.3 g/s (median 9.6, middle 80% of 43 tunes) |
| Idle spark, 800 rpm (Gen III: base spark in drive; Gen IV: idle base spark) | 17–28° (median 22, middle 80% of 481 tunes) | 16–23° (median 21, middle 80% of 69 tunes) | 13–22° (median 18, middle 80% of 174 tunes) | 13–22° (median 17, middle 80% of 42 tunes) |
| Rev limit (fuel cut, in gear) | 6,000–7,000 rpm (median 6,500, middle 80% of 530 tunes) | 5,900–6,950 rpm (median 6,600, middle 80% of 74 tunes) | 6,000–7,100 rpm (median 6,600, middle 80% of 179 tunes) | 6,000–7,100 rpm (median 6,750, middle 80% of 43 tunes) |
| PE lambda | 0.78–0.87 (median 0.83, middle 80% of 490 tunes) | 0.77–0.87 (median 0.83, middle 80% of 65 tunes) | 0.76–0.87 (median 0.83, middle 80% of 165 tunes) | 0.76–0.85 (median 0.79, middle 80% of 37 tunes) |
| PE enable throttle, 3,200 rpm | 19–90% (median 55, middle 80% of 517 tunes) | 20–90% (median 50, middle 80% of 74 tunes) | 11–80% (median 38, middle 80% of 179 tunes) | 8–48% (median 19, middle 80% of 43 tunes) |
| WOT spark, 5,000 rpm, about 0.9 g/cyl | 12.0–27.0° (median 19.2, middle 80% of 500 tunes) | 11.7–21.0° (median 15.0, middle 80% of 66 tunes) | 12.5–25.0° (median 19.2, middle 80% of 172 tunes) | 10.0–23.5° (median 17.0, middle 80% of 41 tunes) |
| Intake air temp where timing pull starts | 86–140°F (median 104, middle 80% of 497 tunes) | 86–149°F (median 122, middle 80% of 67 tunes) | 86–149°F (median 122, middle 80% of 169 tunes) | 86–149°F (median 126, middle 80% of 38 tunes) |
These are ranges, not settings to copy. Start a turn-on tune near stock, log it, and get WOT fuel and spark set on a dyno before any wide-open pass.
Cam size and idle. In the tunes where we know the cam, cams with 227° or more intake duration at .050 idle at 775–1,000 rpm (median 888, 90 tunes). Cams under 227° idle at 600–900 rpm (median 750, 46 tunes). Idle airflow did not track cam size the same way: it follows displacement, throttle body and the rest of the build, so set it from your logs.
Two things the numbers show. Boosted tunes keep the PE table itself near lambda 0.85, the same as NA tunes. The extra fuel under boost comes from elsewhere in the tune (the VE/airflow model or a custom-OS boost table), so check boost fueling on a wideband, not the PE table. And boosted tunes start pulling timing for intake heat later than NA tunes do (see the last row). We still suggest starting the pull at about 100–115°F on a boosted street car: that is more cautious than most of these tunes, and it costs nothing until it's tuned.
What stock looks like (Gen III P01/P59)
Before you change a value, know where GM started. These are read straight out of 38 stock GM calibrations we decoded, by engine: the median, with the range in brackets when files differ. Compare your stock file to these. If a "stock" file you bought or pulled is far off, it has probably been tuned already.
| Engine | Hot idle, in gear / P-N | Idle airflow, in gear / P-N | Idle spark | PE lambda | WOT spark, 5,000 rpm, about 0.9 g/cyl | Injectors | Rev limit |
|---|---|---|---|---|---|---|---|
| 4.8 LR4 (iron truck) 4 stock files | 525 (525–600) / 550 rpm | 5.5 (5.3–5.5) / 5.3 g/s | 22° (19–22) | 0.81 (0.77–0.81) | 19.8° (18.8–25.2) | 25.2 (24.5–25.2) lb/hr | 6000 (5600–6000) |
| 5.3 LM7 (iron truck) 13 stock files | 525 (525–550) / 550 rpm | 6.0 (5.6–6.3) / 5.8 (4.9–5.9) g/s | 18° | 0.77 (0.77–0.84) | 13.3° (11.9–22.0) | 25.2 (24.5–27.5) lb/hr | 6000 (6000–6400) |
| 5.3 LM4 (aluminum truck) 1 stock file | 550 / 550 rpm | 5.8 / 4.9 g/s | 18° | 0.77 | 11.9° | 25.2 lb/hr | 6000 |
| 5.3 L59 (flex-fuel truck) 3 stock files | 550 (525–550) / 550 (538–550) rpm | 5.8 (5.6–5.8) / 4.9 (4.8–4.9) g/s | 18° | 0.77 | 11.9° | 33.0 (33.0–35.4) lb/hr | 6000 |
| 6.0 LQ4 (iron truck) 12 stock files | 575 (550–600) / 575 (550–575) rpm | 6.5 (6.0–6.8) / 6.2 (5.9–6.2) g/s | 16° | 0.82 | 9.2° (9.1–13.2) | 24.5 (24.5–25.2) lb/hr | 5700 (5600–6000) |
| 6.0 LQ9 (high-output truck) 2 stock files | 538 (525–550) / 550 rpm | 6.6 (6.5–6.8) / 6.2 g/s | 16° | 0.81 | 8.6° | 24.5 lb/hr | 6000 |
| 5.7 LS1 1 stock file | 640 / 650 rpm | 8.4 / 6.9 g/s | 20° | 0.82 | 26.0° | 29.1 lb/hr | 6200 |
| 5.7 LS6 2 stock files | 800 / — rpm | 7.4 / — g/s | 17° | 0.81 | 22.0° | 29.1 lb/hr | 6600 |
How to read it: idle is the warm (about 198 °F) desired idle. Idle airflow is the Gen III "desired airflow" table, which reads about 2–3 g/s lower than the idle airflow figure HP Tuners shows on Gen IV (E38) computers, so don't compare it with the Gen IV column above. Manual files: in GM's stock manual setup (M6) the park/neutral idle target and airflow rows are 0 and the engine idles on the in-gear rows at every stop. Truck PE leans richer at high rpm (the lambda here is at 4,500 rpm). Engines with one or two files are a single example, not a rule. A cam, injectors or boost change most of these. Stock values are a reference point, not your tune.
Questions, by where you are
Before you start
HP Tuners or PCM Hammer?
HP Tuners (MPVI4 plus credits) covers Gen III and Gen IV and has the 2- and 3-bar speed density and flex fuel operating systems. PCM Hammer with TunerPro is free and needs only an OBDX Pro GT cable (about $140), but it covers P01, P59 and E38 computers, and boost or flex on Gen III needs HP Tuners. Pick it in the sheet above and the steps change to match.
How many HP Tuners credits will I need?
Most GM engine computers take 2 credits. Some newer ones take more. Check the vehicle list in HP Tuners before you buy.
Do I need a wideband?
For a turn-on tune that only starts, idles and drives gently, the factory O2 sensors get you going. Before you touch part-throttle fuel seriously, and always before any WOT tuning, you want a wideband in the logs.
While you flash
How do I flash safely?
Charge the battery fully first, then unplug the charger: write with the battery at 12 V or more, never below 11.5 V. Doors shut, accessories off, laptop plugged in with sleep turned off. In HP Tuners, use Write Calibration Only for normal changes. Write Entire is only for changing the operating system (for example moving to a 2- or 3-bar custom OS). Don't touch the key or the cable until it says the write is complete.
The write failed partway. Now what?
Don't pull a fuse or disconnect the battery. Check the cable connections, restart VCM Editor, open the same file you were writing and write it again the same way. It matters that it's the same file. Don't switch to Write Entire to recover a failed normal write. If it still fails, stop and contact HP Tuners support. With PCM Hammer, the P01 and P59 have a recovery write; the E38 doesn't, so if an E38 write fails, keep it powered and get help before trying anything else.
After the first start
It hunts, stalls or hangs at idle
That's almost always idle airflow, not fuel. Work through the idle steps in our walkthrough: hot idle target, base airflow, idle spark, then cracker and follower. Log after each change.
When can I go wide open?
Not on a turn-on tune. Get it idling and driving clean on logs first, then finish WOT fuel and spark on a dyno or with a pro tuner and a wideband. Our pre-WOT checks →
Tools in this hub
Turn-on tune sheet
The values to start with for your computer, induction, fuel and cam.
What does my tune need?
The checklist of everything your swap's tune has to handle.
HP Tuners, step by step
58 steps: the tables, what to log, the targets and when to stop.
Don't blow it up
Our safe limits and the checks before any wide-open pass.