When you upgrade your MAP sensor in Holley EFI—like going from a 2-bar to a 3-bar—you gain headroom for more boost and more data resolution. But there’s a persistent myth that you must rescale your VE table whenever you do it.
That’s not entirely true.
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✅ When You Don’t Need to Rescale
If you upgrade your MAP sensor and keep your boost levels within your existing VE table’s MAP axis range, then you don’t need to rescale anything—as long as you correctly update the sensor scaling in Holley.
Why? Because your VE table still references the same airflow conditions at each MAP/RPM combination. The sensor just has a wider range—it doesn’t change what the ECU does with the same kPa values already in use.
In other words:
Same MAP value, same VE value, same result.
Nothing breaks until you push past the original MAP axis limits.
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⚠️ When You Do Need to Rescale
If you plan to run higher boost than your current VE axis supports—for example, increasing from a 210 kPa top row to 260 or 280 kPa—then your VE table needs work.
Here’s why:
• Holley doesn’t automatically stretch your table or reassign VE values when you change sensors.
• If you just add new rows manually, the top of your table is now empty (zero) or copied incorrectly.
• Your old full-boost fueling may now be applied too low in the range—leading to:
• Overfueling in mid-boost
• Lean conditions under full load
• Erratic trims and drivability issues
This is where most tuning mistakes happen—not from the sensor change itself, but from boost increases without updating the VE axis and values.
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🔍 Example Scenario
Let’s say your old top row was 210 kPa, and you tuned that for 15 psi of boost.
You upgrade to a 3-bar sensor and start running 28 psi (~290 kPa). Holley now shows 300 kPa max, but your VE table only goes to 210. So when you reach full boost:
• You’re off the map—literally.
• Holley either extrapolates poorly or uses default/fallback values.
• Your fueling goes lean unless you fill in those new rows accurately.
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💻 Holley’s Behavior: What It Does (and Doesn’t Do)
Older Holley EFI versions (especially early Terminator X firmware and V5 software) won’t prompt you to rescale anything. Even some newer versions will let you change the MAP sensor without updating the table.
Holley updates the sensor limits but not the VE axis or data.
That’s tuner territory—and it’s easy to miss.
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🧮 How to Rescale Correctly (Manual Method)
If you’re extending your boost range beyond the old axis, here’s the right way to fix your VE table:
Export your current VE table and note the old MAP axis
Define the new MAP axis (e.g., up to 300 kPa)
Interpolate the existing data to stretch across the new range
Estimate and build out the new high-boost cells
Smooth transitions from cruise to spool to WOT
Import and verify with datalogs
This preserves the original tune logic while giving you safe control in the new areas.
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🧰 Coming Soon: Our VE Table Rescaler Tool
We’re building a tool to automate the remapping process. It will:
• Read your Holley VE table and axis
• Remap values across a new MAP range using smart interpolation
• Preserve data integrity and cell resolution
• Let you export clean VE tables for paste-in
It’s not live yet—but it’s in development and built from real-world needs just like this one.
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🔚 Final Thoughts
If you’ve changed your MAP sensor but your boost stays within the existing VE table’s range, you’re good—assuming sensor scaling is correct. No need to panic or start over.
But if you’re raising boost and expanding beyond the current MAP axis, you do need to adjust the VE table—or risk fueling problems that won’t show up until it’s too late.
Check your axis. Know your limits. Tune with intent.
We’ll have the tool to make this easier soon.