This is the short printed version. The full report with every explanation is on your order page: https://lsswapbible.com/tune-report/sample/
Your C10: what to do next
Your file matches the engine you entered. The flow data doesn't match the injectors you entered. Every fuel number depends on this, so confirm the part number and fuel pressure first.
Then: sustained logged knock retard (from your log), idle dips (from your log) and full-throttle timing, plus 8 more below.
What it does: Tells the computer how much fuel your injectors flow, so it knows how long to hold them open.
Why it matters: If it's wrong, every fuel number in the tune is off by the same amount, and the computer spends its time correcting it.
If it's set too low: The file thinks the injectors are smaller than they are: runs rich, smells of fuel, idle can be lumpy.
If it's set too high: The file thinks they're bigger: runs lean, hesitates, can ping under load.
MAP sensor settingIn line
You enteredNaturally aspirated
Your file is set toReads to about 1.05 bar
Scaled like a 1-bar sensor. Confirm it matches the installed sensor.
What it does and how it feels
What it does: Tells the computer which pressure sensor is on the intake, so it can read engine load.
Why it matters: Load decides how much fuel and timing the engine gets. If the setting doesn't match the sensor, the computer misreads load everywhere.
How it shows up when it's wrong: Runs poorly everywhere, with odd fuel and timing, and on a boosted car it may not see boost at all.
MAF or speed densityIn line
You enteredMAF
Your file is set toMAF (from your log)
Your log agrees.
What it does and how it feels
What it does: Decides how the computer measures air: with a mass airflow sensor (MAF), or by calculating it from pressure, rpm and the VE table (speed density).
Why it matters: Big cams and boost often run speed density. Either works, but the tables that matter change completely depending on which one is in charge.
How it shows up when it's wrong: A mismatch (MAF unplugged but the file still expects it, for example) gives a check-engine light, rough running and wrong fuel.
Manual or automatic setup
You enteredAutomatic (4L60E)
Your file is set toPark/neutral idle rows in use
We compare the in-gear rows for warm idle.
What it does and how it feels
What it does: Tells the computer which idle rows to use. GM's Gen III manual files leave the park/neutral idle rows at 0 and idle on the in-gear rows at every stop; automatics use both.
Why it matters: It decides which idle settings actually run your idle, so it decides which ones we compare and which ones you'd change.
How it shows up when it's wrong: If the file is set up for the wrong transmission, idle at a stop can stall or hang, because the computer is reading the wrong idle row.
Fuel pressure
You entered58 psi returnless
Your file is set toNot stored in the tune
For reference: the injector check uses this pressure.
What it does and how it feels
What it does: The pressure the pump pushes fuel to the injectors at. The injector flow numbers in the tune assume one pressure.
Why it matters: If the real pressure is different, every injector flows more or less than the tune thinks, so fuel is off everywhere.
How it shows up when it's wrong: Low pressure runs lean and can stumble under load; high pressure runs rich.
Address these first
What to address first, and why
In the order to do them: confirm the facts first, then the settings that depend on them. Each card has the steps to do it yourself, how to check the result, and the option to have us do it.
Confirm these facts first
Fix first
1. Injector data
You enteredAbout 46.2 lb/hr at your pressure
Your file is set to34.4 lb/hr (lowest cell)
The flow data doesn't match the injectors you entered. Every fuel number depends on this, so confirm the part number and fuel pressure first.
What it does: Tells the computer how much fuel your injectors flow, so it knows how long to hold them open.
Why it matters: If it's wrong, every fuel number in the tune is off by the same amount, and the computer spends its time correcting it.
If it's set too low: The file thinks the injectors are smaller than they are: runs rich, smells of fuel, idle can be lumpy.
If it's set too high: The file thinks they're bigger: runs lean, hesitates, can ping under load.
Typical signs, not a diagnosis.
Do it yourself
Check the injector part number and your fuel pressure.
Then compare the file's injector flow table with that injector's data at your pressure.
How to check the result: Fuel trims in a warm log should sit within about ±5%.
A file change alone can't fix injector size or fuel pressure. Ask us and we'll tell you what this one needs before anything is ordered.
Fix first
Fix first
2. Sustained logged knock retard
From Log 2
2 knock events; the most was 5.6° at 4,460 rpm, 96 kPa, 100% throttle. Over 4° held for more than a second is sustained knock retard. The log shows the computer pulling timing; it doesn't show the cause. Take timing out in that area (and check fuel and octane) before more full-throttle pulls.
What it does: Timing the computer pulls when its knock sensors hear something that might be detonation.
Why it matters: A little now and then can be noise. Repeated or large amounts under load mean the computer keeps pulling timing; find out why before more hard pulls.
How it shows up when it's wrong: Pinging or rattling under load, and the car feeling down on power.
Do it yourself
Log it on full-throttle pulls and on hot days. A dyno confirms it.
How to check the result: Log the same drive again after any change and compare.
A file change alone can't fix the cause of knock (fuel, octane or parts). Ask us and we'll tell you what this one needs before anything is ordered.
Fix first
3. Idle dips
From Log 1
About 3 min 15 s of warm idle at 4 stops. It averaged 842 rpm against a desired idle of 850, moving about ±34 rpm (lowest 470). It dropped more than 150 rpm under target 3 times, once close to stalling. More base idle airflow (and a little more idle spark on a cam) usually fixes this.
What it does: Compares the rpm the engine is actually idling at with the rpm the computer wants.
Why it matters: A steady match means the idle airflow is right. A wandering gap means the computer is chasing it.
How it shows up when it's wrong: Hunting idle, stalls at stops, or rpm hanging after you clutch in.
Do it yourself
Log a few minutes of warm idle, plus a few stops.
How to check the result: Log the same drive again after any change and compare.
Similar builds and tunes we've reviewed: 12.4–27.7°
Typical for similar builds: 18.0. The band is the middle of the similar builds and tunes we've reviewed, with unusual outliers left out; it is not a target range.
Your file runs more full-throttle timing than most similar builds we've reviewed. A log and a dyno session are needed to judge a change.
What it does: How early the spark fires at full throttle near peak power.
Why it matters: The right number depends on your engine, fuel and conditions. It's set on a dyno, with knock retard logged.
Your file is above the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too high, you might notice: Pinging or rattling under load, and knock retard showing in a log.
If it's set too low: Flat, lazy pull up top, with hotter exhaust.
Typical signs, not a diagnosis.
Do it yourself
Log knock retard on a few pulls. Set full-throttle timing on a dyno.
How to check the result: Log knock retard and intake temperature after any change. Finish it on a dyno.
Either way, full-throttle fuel and timing get finished on a dyno.
Worth a look
Worth a look
5. Idle airflow, in gear
Base idle airflow, warm, in gear
6.9 g/s
Similar builds and tunes we've reviewed: 7.8–11.3 g/s
Typical for similar builds: 9.8. The band is the middle of the similar builds and tunes we've reviewed, with unusual outliers left out; it is not a target range.
Your file starts with less idle air than most similar builds we've reviewed. Check the actual idle in a warm log before changing it.
What it does: The computer's starting guess for how much air to let in at a warm idle in gear. Gen III manual files use this row at every stop.
Why it matters: If the guess is off, the computer is always chasing the idle. That's the most common cause of stalls and hanging idles after a cam swap.
Your file is below the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too low, you might notice: Idle sags or stalls when you come to a stop.
If it's set too high: Idle hangs high and drops slowly when you stop.
Typical signs, not a diagnosis.
Do it yourself
Look at the idle airflow table at warm coolant, then log a warm idle and a few stops.
Log idle airflow learning (or the idle correction) at a warm idle in gear.
How to check the result: Log again, warm: the actual idle should sit on the target without dips when you stop.
Similar builds and tunes we've reviewed: 17.8–24.0°
Typical for similar builds: 22.0. The band is the middle of the similar builds and tunes we've reviewed, with unusual outliers left out; it is not a target range.
Your file uses less idle timing than most similar builds we've reviewed. Check the actual idle in a warm log before changing it.
What it does: How early the spark fires at idle. The computer also moves it up and down to steady the idle.
Why it matters: Big cams usually idle better with a bit more timing. Too little makes the engine work harder just to idle.
Your file is below the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too low, you might notice: Lazy, rough idle that runs hot and needs extra air to hold rpm.
If it's set too high: Idle can surge or feel jumpy, with timing swinging around in a log.
Typical signs, not a diagnosis.
Do it yourself
Log idle spark and rpm together, warm. Change idle timing in small steps only if the idle is unsteady.
How to check the result: Log again, warm: the actual idle should sit on the target without dips when you stop.
Similar builds and tunes we've reviewed: 1.0–2.5 g/s
Typical for similar builds: 1.6. The band is the middle of the similar builds and tunes we've reviewed, with unusual outliers left out; it is not a target range.
Your file adds more follower air than most similar builds we've reviewed. Check a few tip-outs in a log before changing it.
What it does: Air the computer keeps adding for a moment as you come off the pedal, matched to how far the throttle was open.
Why it matters: It smooths the step from driving to idle so the engine doesn't dip or bog on tip-out.
Your file is above the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too high, you might notice: The engine hangs or feels like it's still pulling for a moment after you lift.
If it's set too low: A dip or stumble when you come off the gas.
Typical signs, not a diagnosis.
Do it yourself
Log a few light-throttle tip-outs and watch rpm and airflow.
How to check the result: Log again, warm: the actual idle should sit on the target without dips when you stop.
Total trim (short + long) averaged -12.3% across 4 driven areas. The biggest correction was -12.7% on bank 2 at 1,800–2,600 rpm, MAP 45–70 kPa: the computer is pulling fuel there. Running rich everywhere points to one cause across the board (injector data, fuel pressure, or the MAF calibration as a whole) more than one bad area. Over 10% means the MAF calibration is off in that area. Correct it in small steps and log again.
What it does: How much fuel the computer adds or removes on its own to hit its target. Plus means it's adding, minus means it's pulling.
Why it matters: Small numbers mean the base tune is close. Big or uneven numbers mean the fuel tables or injector data need work.
How it shows up when it's wrong: Large corrections show up as surging, poor mileage, fuel smell or hesitation.
Do it yourself
Log short- and long-term trims at idle, cruise and light acceleration, warm.
How to check the result: Log the same drive again after any change and compare.
Total trim (short + long) averaged -12.0% across 2 driven areas. The biggest correction was -12.2% on bank 1 at under 1,000 rpm (idle), MAP under 45 kPa: the computer is pulling fuel there. Over 10% means the MAF calibration is off in that area. Correct it in small steps and log again.
What it does: How much fuel the computer adds or removes on its own to hit its target. Plus means it's adding, minus means it's pulling.
Why it matters: Small numbers mean the base tune is close. Big or uneven numbers mean the fuel tables or injector data need work.
How it shows up when it's wrong: Large corrections show up as surging, poor mileage, fuel smell or hesitation.
Do it yourself
Log short- and long-term trims at idle, cruise and light acceleration, warm.
How to check the result: Log the same drive again after any change and compare.
Your wideband read richer than the tune asked for, for a sustained part of 2 runs. In run 1 (2,500–5,953 rpm) it averaged lambda 0.795 against about 0.855 asked, with 6.5 s more than 5% richer than asked (up to 7.7% rich) (6.5 s compared of 6.5 s after the first second). In run 2 (2,500–5,953 rpm) it averaged lambda 0.795 against about 0.855 asked, with 6.5 s more than 5% richer than asked (up to 7.7% rich) (6.5 s compared of 6.5 s after the first second). Compared moment by moment after the first second of each run (wideband read as lambda). That usually means the fuel model (injector data, VE or MAF) is off at full load. Check it on a dyno.
What it does: Compares the air/fuel the tune asks for at full throttle with what a wideband sensor actually measures.
Why it matters: It's the only way to see what fuel the engine actually got at full throttle, not just what the tune asked for.
How it shows up when it's wrong: Leaner than asked is a reason to stop and check the fuel system. Richer than asked usually means the fuel model needs work.
Do it yourself
Needs a wideband logged as lambda (or AFR on pump gas) together with Equivalence Ratio Commanded. Without both, we can't compare them.
How to check the result: Log the same drive again after any change and compare.
Either way, full-throttle fuel and timing get finished on a dyno.
Worth a look
11. Hot-air timing pullback: where it starts
Intake-temperature timing correction begins at
149°F
Similar builds and tunes we've reviewed: 86–140°F
Typical for similar builds: 103. The band is the middle of the similar builds and tunes we've reviewed, with unusual outliers left out; it is not a target range.
Your file starts pulling timing for hot air later than most similar builds we've reviewed. Review this table with logged intake temperature and timing.
What it does: The intake air temperature where the computer starts taking timing out, to lower the chance of knock.
Why it matters: Hot air makes knock more likely. This table decides how much timing comes out on hot days or after sitting in traffic.
Your file is above the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too high, you might notice: Starts late: on a hot day or after heat soak at a light, the first hard pull may ping before the computer reacts.
If it's set too low: Starts early: the car can feel lazier on hot days or after a long idle, even when it doesn't need protection.
Typical signs, not a diagnosis.
Do it yourself
Open the IAT spark correction table and look at where it starts taking timing out and how much.
Log intake temperature, timing and knock retard on a hot day, including a pull after sitting at idle.
How to check the result: Log knock retard and intake temperature after any change. Finish it on a dyno.
Either way, full-throttle fuel and timing get finished on a dyno.
Worth a look
12. Rev limiter
Fuel-cut rev limit, in gear
6,900 rpm
Similar builds and tunes we've reviewed: 6,000–6,800 rpm
Typical for similar builds: 6,200. The band is the middle of the similar builds and tunes we've reviewed, with unusual outliers left out; it is not a target range.
Your file revs higher than most similar builds we've reviewed. Match it to your cam card and valve springs.
What it does: The rpm where the computer cuts fuel to stop the engine revving higher.
Why it matters: It should sit below the rpm your valve springs and parts are rated for. Bigger cams often need better springs before more rpm.
Your file is above the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too high, you might notice: Lets the engine rev higher. If that's past what your valve springs are rated for, you may feel a stumble or miss near the limiter (valve float).
If it's set too low: Hits the limiter early and bounces before your shift point.
Typical signs, not a diagnosis.
Do it yourself
Check your cam card and valve spring rating against the limit.
Match it to your cam card and spring rating.
How to check the result: Confirm it on the dyno with your valvetrain in mind.
Either way, full-throttle fuel and timing get finished on a dyno.
Connect the file to the engine
What your log shows
What the engine actually did, read from the logs you sent. A street log shows trends; it doesn't replace a dyno. Anything here that needs action is also in the cards above.
Log 1: 7.0 minutes, 4,200 samples, 18 channels we use.
Looks right in this logCoolant temperature
Coolant went from 196°F to 198°F.
What this means and why it matters
What it does: Engine temperature. The computer changes idle, fuel and timing until it's warm.
Why it matters: Most comparisons only make sense once the engine is fully warm. It also shows cooling problems.
How it shows up when it's wrong: Runs too hot, or never warms up fully (a thermostat problem).
Fix firstIdle dips
About 3 min 15 s of warm idle at 4 stops. It averaged 842 rpm against a desired idle of 850, moving about ±34 rpm (lowest 470). It dropped more than 150 rpm under target 3 times, once close to stalling. More base idle airflow (and a little more idle spark on a cam) usually fixes this.
What it does: Compares the rpm the engine is actually idling at with the rpm the computer wants.
Why it matters: A steady match means the idle airflow is right. A wandering gap means the computer is chasing it.
How it shows up when it's wrong: Hunting idle, stalls at stops, or rpm hanging after you clutch in.
Worth a lookFuel trims high
Total trim (short + long) averaged -12.3% across 4 driven areas. The biggest correction was -12.7% on bank 2 at 1,800–2,600 rpm, MAP 45–70 kPa: the computer is pulling fuel there. Running rich everywhere points to one cause across the board (injector data, fuel pressure, or the MAF calibration as a whole) more than one bad area. Over 10% means the MAF calibration is off in that area. Correct it in small steps and log again.
What it does: How much fuel the computer adds or removes on its own to hit its target. Plus means it's adding, minus means it's pulling.
Why it matters: Small numbers mean the base tune is close. Big or uneven numbers mean the fuel tables or injector data need work.
How it shows up when it's wrong: Large corrections show up as surging, poor mileage, fuel smell or hesitation.
Looks right in this logKnock retard
No knock retard recorded in this log (7.0 minutes, no full-throttle run).
What this means and why it matters
What it does: Timing the computer pulls when its knock sensors hear something that might be detonation.
Why it matters: A little now and then can be noise. Repeated or large amounts under load mean the computer keeps pulling timing; find out why before more hard pulls.
How it shows up when it's wrong: Pinging or rattling under load, and the car feeling down on power.
NoteNo wide-open-throttle pull
The log has no full-throttle run, so WOT fuel, timing and injector duty aren't checked. If you already log on a dyno or a track, one 3rd- or 4th-gear pull from about 2,500 rpm tells us a lot. Don't make full-throttle runs on the street for us.
What this means and why it matters
What it does: Compares the air/fuel the tune asks for at full throttle with what a wideband sensor actually measures.
Why it matters: It's the only way to see what fuel the engine actually got at full throttle, not just what the tune asked for.
How it shows up when it's wrong: Leaner than asked is a reason to stop and check the fuel system. Richer than asked usually means the fuel model needs work.
Looks right in this logIntake air temp
Intake air topped out at 99°F.
What this means and why it matters
What it does: How hot the air going into the engine is.
Why it matters: Hotter air means less power and more chance of knock. Hot-air timing pullback is based on it.
How it shows up when it's wrong: Feeling slower after sitting in traffic or on hot days.
Idle: actual vs desired rpm
Idle dips.
actual rpmdesired idle rpm
The longest warm idle at a stop in this log (70 s, coolant 196°F).
Fuel corrections by rpm and MAP
Short + long term trim, warm closed-loop driving only, from the loop status in your log (about 7 min of it in this log). + means the computer adds fuel (running lean), − means it pulls fuel (running rich). A hatched cell means too little driving there to read.
Bank 1
RPM \ MAP
under 45 kPa
45–70 kPa
70+ kPa
under 1,000 rpm (idle)
−12.0%
–
–
1,000–1,800 rpm
−11.9%
−12.3%
–
1,800–2,600 rpm
–
−12.6%
–
2,600–3,600 rpm
–
–
–
3,600+ rpm
–
–
–
Bank 2
RPM \ MAP
under 45 kPa
45–70 kPa
70+ kPa
under 1,000 rpm (idle)
−12.1%
–
–
1,000–1,800 rpm
−12.3%
−12.3%
–
1,800–2,600 rpm
–
−12.7%
–
2,600–3,600 rpm
–
–
–
3,600+ rpm
–
–
–
Add these to your next log
Wideband O2 (AFR or lambda)The only way to see actual WOT fuel.
Log 2: 1.7 minutes, 1,030 samples, 19 channels we use.
Looks right in this logCoolant temperature
Coolant went from 199°F to 201°F.
What this means and why it matters
What it does: Engine temperature. The computer changes idle, fuel and timing until it's warm.
Why it matters: Most comparisons only make sense once the engine is fully warm. It also shows cooling problems.
How it shows up when it's wrong: Runs too hot, or never warms up fully (a thermostat problem).
Looks right in this logIdle
About 0 min 40 s of warm idle at 2 stops. It averaged 850 rpm against a desired idle of 850, moving about ±15 rpm (lowest 830). Steady and on target.
What this means and why it matters
What it does: Compares the rpm the engine is actually idling at with the rpm the computer wants.
Why it matters: A steady match means the idle airflow is right. A wandering gap means the computer is chasing it.
How it shows up when it's wrong: Hunting idle, stalls at stops, or rpm hanging after you clutch in.
Worth a lookFuel trims high
Total trim (short + long) averaged -12.0% across 2 driven areas. The biggest correction was -12.2% on bank 1 at under 1,000 rpm (idle), MAP under 45 kPa: the computer is pulling fuel there. Over 10% means the MAF calibration is off in that area. Correct it in small steps and log again.
What it does: How much fuel the computer adds or removes on its own to hit its target. Plus means it's adding, minus means it's pulling.
Why it matters: Small numbers mean the base tune is close. Big or uneven numbers mean the fuel tables or injector data need work.
How it shows up when it's wrong: Large corrections show up as surging, poor mileage, fuel smell or hesitation.
Fix firstSustained logged knock retard
2 knock events; the most was 5.6° at 4,460 rpm, 96 kPa, 100% throttle. Over 4° held for more than a second is sustained knock retard. The log shows the computer pulling timing; it doesn't show the cause. Take timing out in that area (and check fuel and octane) before more full-throttle pulls.
What it does: Timing the computer pulls when its knock sensors hear something that might be detonation.
Why it matters: A little now and then can be noise. Repeated or large amounts under load mean the computer keeps pulling timing; find out why before more hard pulls.
How it shows up when it's wrong: Pinging or rattling under load, and the car feeling down on power.
NoteFull-throttle runs
2 full-throttle runs; the longest went 2,500–5,953 rpm over 7.5 s, MAP up to 97 kPa.
What this means and why it matters
What it does: Compares the air/fuel the tune asks for at full throttle with what a wideband sensor actually measures.
Why it matters: It's the only way to see what fuel the engine actually got at full throttle, not just what the tune asked for.
How it shows up when it's wrong: Leaner than asked is a reason to stop and check the fuel system. Richer than asked usually means the fuel model needs work.
Looks right in this logCommanded WOT fuel
The tune commanded lambda 0.855 at full throttle (about 12.6:1 on a gasoline-scale wideband), so power enrichment is coming in. This is what the tune asked for, not what the engine got.
Worth a lookRicher than commanded at WOT
Your wideband read richer than the tune asked for, for a sustained part of 2 runs. In run 1 (2,500–5,953 rpm) it averaged lambda 0.795 against about 0.855 asked, with 6.5 s more than 5% richer than asked (up to 7.7% rich) (6.5 s compared of 6.5 s after the first second). In run 2 (2,500–5,953 rpm) it averaged lambda 0.795 against about 0.855 asked, with 6.5 s more than 5% richer than asked (up to 7.7% rich) (6.5 s compared of 6.5 s after the first second). Compared moment by moment after the first second of each run (wideband read as lambda). That usually means the fuel model (injector data, VE or MAF) is off at full load. Check it on a dyno.
Injector duty peaked at about 64% (worked out from pulse width and rpm) in runs up to 5,953 rpm. Duty climbs with rpm, so check it again on a full pull to your shift point.
What this means and why it matters
What it does: How much of the available time the injectors are held open.
Why it matters: As it gets near the top, the injectors are running out of room to add fuel. That matters most on boosted or high-rpm builds.
How it shows up when it's wrong: Lean at the top of a pull on a big-power build.
Looks right in this logIntake air temp
Intake air topped out at 107°F.
What this means and why it matters
What it does: How hot the air going into the engine is.
Why it matters: Hotter air means less power and more chance of knock. Hot-air timing pullback is based on it.
How it shows up when it's wrong: Feeling slower after sitting in traffic or on hot days.
Idle: actual vs desired rpm
Idle.
actual rpmdesired idle rpm
The longest warm idle at a stop in this log (25 s, coolant 199°F).
Full throttle: commanded vs measured lambda
commanded lambdameasured lambda (wideband)
The longest full-throttle run in this log, 1 s either side. RPM on its own panel, same time scale.
Fuel corrections by rpm and MAP
Short + long term trim, warm closed-loop driving only, from the loop status in your log (about 1 min of it in this log). + means the computer adds fuel (running lean), − means it pulls fuel (running rich). A hatched cell means too little driving there to read.
Bank 1
RPM \ MAP
under 45 kPa
45–70 kPa
70+ kPa
under 1,000 rpm (idle)
−12.2%
–
–
1,000–1,800 rpm
–
–
–
1,800–2,600 rpm
–
−12.1%
–
2,600–3,600 rpm
–
–
–
3,600+ rpm
–
–
–
Bank 2
RPM \ MAP
under 45 kPa
45–70 kPa
70+ kPa
under 1,000 rpm (idle)
−11.8%
–
–
1,000–1,800 rpm
–
–
–
1,800–2,600 rpm
–
−11.8%
–
2,600–3,600 rpm
–
–
–
3,600+ rpm
–
–
–
Full-throttle runs in this log
RPM
MAP max (kPa)
Commanded lambda
Wideband lambda
Knock max (°)
Intake air (°F)
Injector duty (%)
2,500–5,953 (7.5 s)
97
0.855
0.795
5.6
105
64
2,500–5,953 (7.5 s)
97
0.855
0.795
2.5
106
64
Put the rest in context
How the rest of your file compares
Every setting we compared, grouped by what you'd feel. "In line" means the setting sits where similar builds we've reviewed sit; it doesn't mean the tune is finished.
Settings that already have a card above aren't repeated here.
similar builds (not a target)typicalyour file
At idle and coming off the pedal
How the engine holds its idle, and how it lands back on idle when you lift off or push in the clutch.
Warm idle speedIn line
Warm idle target, in gear
850 rpmSimilar builds: 700–900 rpm (the middle of the range)
What it does: The rpm the computer aims for once the engine is warm.
What it does and how it feels
What it does: The rpm the computer aims for once the engine is warm.
Why it matters: A cammed engine needs enough rpm to idle smoothly, but not so much that the car pushes against the brakes.
If it's set too high: Car creeps or pushes in gear (automatics), and rpm is slow to come down when you stop.
If it's set too low: Shaky, lopey idle that dips when the A/C or fans come on, and can stall at a stop.
Idle airflow, in gearWorth a look
Base idle airflow, warm, in gear
6.9 g/sSimilar builds: 7.8–11.3 g/s (the middle of the range)
Your file starts with less idle air than most similar builds we've reviewed. Check the actual idle in a warm log before changing it.
What it does: The computer's starting guess for how much air to let in at a warm idle in gear.
What it does and how it feels
What it does: The computer's starting guess for how much air to let in at a warm idle in gear. Gen III manual files use this row at every stop.
Why it matters: If the guess is off, the computer is always chasing the idle. That's the most common cause of stalls and hanging idles after a cam swap.
Your file is below the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too low, you might notice: Idle sags or stalls when you come to a stop.
If it's set too high: Idle hangs high and drops slowly when you stop.
Idle airflow, park/neutralIn line
Base idle airflow, warm, park/neutral
7.9 g/sSimilar builds: 7.6–10.4 g/s (the middle of the range)
What it does: The same starting guess for idle air, used in park or neutral.
What it does and how it feels
What it does: The same starting guess for idle air, used in park or neutral. GM's Gen III manual files set this row to 0 and idle on the in-gear row instead.
Why it matters: If it's the row your car idles on and it's off, the idle hunts. Manual cars feel it most when the clutch goes in.
If it's set too low: Rpm drops hard and can stall when you clutch in coming to a stop.
If it's set too high: Rpm hangs at 1,200 to 1,500 after you clutch in before it settles.
Idle timingWorth a look
Idle spark at 800 rpm
16.0°Similar builds: 17.8–24.0° (the middle of the range)
Your file uses less idle timing than most similar builds we've reviewed. Check the actual idle in a warm log before changing it.
What it does: How early the spark fires at idle. The computer also moves it up and down to steady the idle.
Why it matters: Big cams usually idle better with a bit more timing. Too little makes the engine work harder just to idle.
Your file is below the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too low, you might notice: Lazy, rough idle that runs hot and needs extra air to hold rpm.
If it's set too high: Idle can surge or feel jumpy, with timing swinging around in a log.
Throttle crackerIn line
Throttle cracker at 1,600 rpm, stopped
0.60 g/sSimilar builds: 0.00–1.00 g/s (the middle of the range)
What it does: Extra air the computer adds as the throttle closes and rpm falls, so the engine lands softly on idle.
What it does and how it feels
What it does: Extra air the computer adds as the throttle closes and rpm falls, so the engine lands softly on idle.
Why it matters: It's what keeps a cammed engine from stalling when you lift off or clutch in at speed.
If it's set too high: Rpm hangs above idle for a second or two before it comes down.
If it's set too low: Rpm dips below idle or stalls when you lift off or push in the clutch.
Throttle followerWorth a look
Throttle follower at 13.5% throttle
3.4 g/sSimilar builds: 1.0–2.5 g/s (the middle of the range)
Your file adds more follower air than most similar builds we've reviewed. Check a few tip-outs in a log before changing it.
What it does: Air the computer keeps adding for a moment as you come off the pedal, matched to how far the throttle was open.
What it does and how it feels
What it does: Air the computer keeps adding for a moment as you come off the pedal, matched to how far the throttle was open.
Why it matters: It smooths the step from driving to idle so the engine doesn't dip or bog on tip-out.
Your file is above the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too high, you might notice: The engine hangs or feels like it's still pulling for a moment after you lift.
If it's set too low: A dip or stumble when you come off the gas.
Fuel under load
What your file asks for at full throttle. Only a wideband log shows what the engine actually gets.
Full-throttle fuelIn line
Commanded power-enrichment lambda at 4,500 rpm
0.855Similar builds: 0.776–0.871 (the middle of the range)
What it does: How rich the engine runs at full throttle (power enrichment).
What it does and how it feels
What it does: How rich the engine runs at full throttle (power enrichment). Lower lambda means more fuel.
Why it matters: Extra fuel at full throttle helps control combustion heat and knock. The file only says what it asks for; a wideband shows what the engine actually gets.
If it's set too high: Leaner than the engine needs: pinging under load, or knock retard showing in a log. A wideband log shows what it actually gets.
If it's set too low: Very rich: feels flat or boggy near the top, black smoke, sooty plugs.
When full-throttle fuel kicks inIn line
Power-enrichment throttle threshold at 3,200 rpm
50%Similar builds: 30–90% (the middle of the range)
What it does: How far you have to press the pedal before the extra full-throttle fuel comes in.
What it does and how it feels
What it does: How far you have to press the pedal before the extra full-throttle fuel comes in.
Why it matters: Set too high and the engine runs lean at heavy-but-not-floored throttle, like a highway pass or a hill.
If it's set too low: Extra fuel comes in early: worse mileage and a rich smell at moderate throttle.
If it's set too high: Hesitation or pinging at 70 to 90% throttle, before you're fully floored.
Timing as load and temperature rise
Spark at full load, and how much your file takes out as the intake air heats up.
Full-throttle timingFix first
Full-throttle spark at 5,000 rpm, about 0.9 g/cyl
30.5°Similar builds: 12.4–27.7° (the middle of the range)
Your file runs more full-throttle timing than most similar builds we've reviewed. A log and a dyno session are needed to judge a change.
What it does: How early the spark fires at full throttle near peak power.
What it does and how it feels
What it does: How early the spark fires at full throttle near peak power.
Why it matters: The right number depends on your engine, fuel and conditions. It's set on a dyno, with knock retard logged.
Your file is above the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too high, you might notice: Pinging or rattling under load, and knock retard showing in a log.
If it's set too low: Flat, lazy pull up top, with hotter exhaust.
Hot-air timing pullback: where it startsWorth a look
Intake-temperature timing correction begins at
149°FSimilar builds: 86–140°F (the middle of the range)
Your file starts pulling timing for hot air later than most similar builds we've reviewed. Review this table with logged intake temperature and timing.
What it does: The intake air temperature where the computer starts taking timing out, to lower the chance of knock.
What it does and how it feels
What it does: The intake air temperature where the computer starts taking timing out, to lower the chance of knock.
Why it matters: Hot air makes knock more likely. This table decides how much timing comes out on hot days or after sitting in traffic.
Your file is above the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too high, you might notice: Starts late: on a hot day or after heat soak at a light, the first hard pull may ping before the computer reacts.
If it's set too low: Starts early: the car can feel lazier on hot days or after a long idle, even when it doesn't need protection.
Hot-air timing pullback: how much at 160°FIn line
Timing correction at 160°F intake air
−4.6°Similar builds: −8.4 to 0.0° (the middle of the range)
What it does: How much timing the computer takes out when intake air is very hot, around 160°F (heat-soaked or boosted).
What it does and how it feels
What it does: How much timing the computer takes out when intake air is very hot, around 160°F (heat-soaked or boosted).
Why it matters: It's how much timing comes out in the hottest conditions your engine sees, like heat soak or boost.
If it's set too high: Pulls little: pinging or knock retard when the intake air is hot, like after heat soak at a light.
If it's set too low: Pulls a lot: the car can feel noticeably slower when the intake air is hot.
Engine speed limits
Where your file cuts fuel to stop the engine revving higher.
Rev limiterWorth a look
Fuel-cut rev limit, in gear
6,900 rpmSimilar builds: 6,000–6,800 rpm (the middle of the range)
Your file revs higher than most similar builds we've reviewed. Match it to your cam card and valve springs.
What it does: The rpm where the computer cuts fuel to stop the engine revving higher.
What it does and how it feels
What it does: The rpm where the computer cuts fuel to stop the engine revving higher.
Why it matters: It should sit below the rpm your valve springs and parts are rated for. Bigger cams often need better springs before more rpm.
Your file is above the similar builds we've reviewed. That alone doesn't mean it's wrong for your engine. If it is too high, you might notice: Lets the engine rev higher. If that's past what your valve springs are rated for, you may feel a stumble or miss near the limiter (valve float).
If it's set too low: Hits the limiter early and bounces before your shift point.
Choose how to move forward
Your next steps
Confirm the hardware and build details: Injector data.
Work through the cards above in order, starting with injector data.
Log the car and check how the engine responds: warm idle, cruising, and one full-throttle pull with a wideband.
Finish the tune on a dyno.
A log tells us how the engine is responding; the dyno is where full-throttle fuel and timing get set, with the engine under load and measured.
Let us do it
Start-up File
$79
A flash-ready start-up file for your build: start-up, idle and drivability settings, with every change listed and 10 revisions over 60 days. Open, never locked. It doesn't fix hardware problems (cooling, fuel delivery, injector size, knock from fuel or parts), and full-throttle fuel and timing still get finished on a dyno.
A full custom tune built from your logs, with 10 revisions over 60 days. $199 is the naturally aspirated base price; boost (+$100), flex fuel (+$50) and automatic transmission tuning (+$50) are add-ons. Finish it on a dyno.
These links open the questions box on your order page, so you can ask us about it without re-entering your build. Nothing is ordered or charged until we've agreed what you need. Your order page: https://lsswapbible.com/tune-report/sample/
Report details
Still to verify
Things this report can't settle from the file alone. We go through them with you before any file changes.
Anti-theft (VATS) settings
Which airflow strategy the computer uses (MAF or speed density)
Rev limit against your valvetrain
Build and file details
P59 · OS 00000000
Matched as: HP Tuners · 5.3 L · Gen III · NA · pump gas · MAF · automatic · truck stock intake · cam you typed (220/224, 113 LSA) · 40 lb/hr injectors · fuel system: returnless, 58 psi
How this comparison works
Compared against real-world LS tunes, read table by table: 8,348,736 values from 137,934 tables, in a library of 5,400+ tune files.
We read the tables in your file and review each setting in this report across the builds and tunes closest to yours: same kind of engine, cam, fuel and setup.
The bars show where similar builds sit and what's typical. Each one says whether its band is the full range of those builds or the middle of them (unusual outliers left out, so one odd tune doesn't stretch it). They are not targets, and a setting outside them is not automatically wrong. Where we don't have enough similar builds for a setting, it says "Not compared".
This report compares your file with real tunes. It isn't a finished tune, and every engine is different. Log before you trust any change. Finish the tune on a dyno. A log tells us how the engine is responding; the dyno is where full-throttle fuel and timing get set, with the engine under load and measured.