diff --git a/firmware/config/boards/hellen/hellen128/board_configuration.cpp b/firmware/config/boards/hellen/hellen128/board_configuration.cpp
index 3272b03255..efca7e23dd 100644
--- a/firmware/config/boards/hellen/hellen128/board_configuration.cpp
+++ b/firmware/config/boards/hellen/hellen128/board_configuration.cpp
@@ -115,7 +115,6 @@ void setBoardConfigOverrides(void) {
 	engineConfiguration->canTxPin = GPIOD_1;
 	engineConfiguration->canRxPin = GPIOD_0;
 
-	setHellenDefaultVrThresholds(PASS_CONFIG_PARAMETER_SIGNATURE);
 	engineConfiguration->vrThreshold[0].pin = GPIOD_14;
 }
 
diff --git a/firmware/config/engines/custom_engine.cpp b/firmware/config/engines/custom_engine.cpp
index 1ebf8f605e..b67cd8f54d 100644
--- a/firmware/config/engines/custom_engine.cpp
+++ b/firmware/config/engines/custom_engine.cpp
@@ -765,6 +765,6 @@ void setHellen72etb(DECLARE_CONFIG_PARAMETER_SIGNATURE) {
 void setHellenDefaultVrThresholds(DECLARE_CONFIG_PARAMETER_SIGNATURE) {
 	for (int i = 0;i<VR_THRESHOLD_COUNT;i++) {
 		setLinearCurve(engineConfiguration->vrThreshold[i].rpmBins, 600, 7000, 100);
-		setLinearCurve(engineConfiguration->vrThreshold[i].values, 0.6, 1.2, 0.1);
+		setLinearCurve(engineConfiguration->vrThreshold[i].values, PACK_PERCENT_BYTE_MULT * 0.6, PACK_PERCENT_BYTE_MULT * 1.2, PACK_PERCENT_BYTE_MULT * 0.1);
 	}
 }
diff --git a/firmware/config/engines/mercedes.cpp b/firmware/config/engines/mercedes.cpp
index 25253a653b..3b44e6fed3 100644
--- a/firmware/config/engines/mercedes.cpp
+++ b/firmware/config/engines/mercedes.cpp
@@ -6,9 +6,19 @@
  */
 
 #include "pch.h"
+#include "custom_engine.h"
+
+static void common(DECLARE_CONFIG_PARAMETER_SIGNATURE) {
+	setHellenDefaultVrThresholds(PASS_CONFIG_PARAMETER_SIGNATURE);
+}
+
+void setHellenMercedes128_4_cyl(DECLARE_CONFIG_PARAMETER_SIGNATURE) {
+    common(PASS_CONFIG_PARAMETER_SIGNATURE);
+}
 
 // is this M104 or M112 or both?
 void setHellenMercedes128_6_cyl(DECLARE_CONFIG_PARAMETER_SIGNATURE) {
+    common(PASS_CONFIG_PARAMETER_SIGNATURE);
 	engineConfiguration->specs.cylindersCount = 6;
 	// 1-4-2-5-3-6 M104
 	engineConfiguration->specs.firingOrder = FO_1_4_3_6_2_5; // M112
@@ -16,6 +26,7 @@ void setHellenMercedes128_6_cyl(DECLARE_CONFIG_PARAMETER_SIGNATURE) {
 
 // M113
 void setHellenMercedes128_8_cyl(DECLARE_CONFIG_PARAMETER_SIGNATURE) {
+    common(PASS_CONFIG_PARAMETER_SIGNATURE);
 	engineConfiguration->specs.cylindersCount = 8;
 	engineConfiguration->specs.firingOrder = FO_1_5_4_2_6_3_7_8;
 }
diff --git a/firmware/config/engines/mercedes.h b/firmware/config/engines/mercedes.h
index d5920382a4..79f5e8fbc2 100644
--- a/firmware/config/engines/mercedes.h
+++ b/firmware/config/engines/mercedes.h
@@ -9,5 +9,6 @@
 
 #include "engine_configuration.h"
 
+void setHellenMercedes128_4_cyl(DECLARE_CONFIG_PARAMETER_SIGNATURE);
 void setHellenMercedes128_6_cyl(DECLARE_CONFIG_PARAMETER_SIGNATURE);
 void setHellenMercedes128_8_cyl(DECLARE_CONFIG_PARAMETER_SIGNATURE);
diff --git a/firmware/controllers/algo/engine_configuration.cpp b/firmware/controllers/algo/engine_configuration.cpp
index c7f0403edd..e2a5cb22cd 100644
--- a/firmware/controllers/algo/engine_configuration.cpp
+++ b/firmware/controllers/algo/engine_configuration.cpp
@@ -859,7 +859,6 @@ void resetConfigurationExt(configuration_callback_t boardCallback, engine_type_e
 // todo: is it time to replace MICRO_RUS_EFI, PROTEUS, PROMETHEUS_DEFAULTS with MINIMAL_PINS? maybe rename MINIMAL_PINS to DEFAULT?
 	case PROTEUS_DEFAULTS:
 	case PROMETHEUS_DEFAULTS:
-	case HELLEN_128_MERCEDES_4_CYL:
 	case MINIMAL_PINS:
 		// all basic settings are already set in prepareVoidConfiguration(), no need to set anything here
 		// nothing to do - we do it all in setBoardDefaultConfiguration
@@ -938,6 +937,9 @@ void resetConfigurationExt(configuration_callback_t boardCallback, engine_type_e
 #endif // HARDWARE_CI
 #endif // HW_PROTEUS
 #if HW_HELLEN
+	case HELLEN_128_MERCEDES_4_CYL:
+		setHellenMercedes128_4_cyl(PASS_CONFIG_PARAMETER_SIGNATURE);
+		break;
 	case HELLEN_128_MERCEDES_6_CYL:
 		setHellenMercedes128_6_cyl(PASS_CONFIG_PARAMETER_SIGNATURE);
 		break;
diff --git a/firmware/controllers/sensors/vr_pwm.cpp b/firmware/controllers/sensors/vr_pwm.cpp
index 3d81f27ec8..98eb91714d 100644
--- a/firmware/controllers/sensors/vr_pwm.cpp
+++ b/firmware/controllers/sensors/vr_pwm.cpp
@@ -12,7 +12,7 @@ static void updateVrPwm(int rpm, size_t index DECLARE_ENGINE_PARAMETER_SUFFIX) {
 		return;
 	}
 
-	float thresholdVoltage = interpolate2d(rpm / RPM_1_BYTE_PACKING_MULT, cfg.rpmBins, cfg.values) / 100.0f;
+	float thresholdVoltage = interpolate2d(rpm / RPM_1_BYTE_PACKING_MULT, cfg.rpmBins, cfg.values) / PACK_PERCENT_BYTE_MULT;
 
 	// 0v   threshold voltage = 3.3v output from mcu = 100% duty
 	// 2.5v threshold voltage = 0v   output from mcu = 0% duty
diff --git a/unit_tests/tests/test_sensors.cpp b/unit_tests/tests/test_sensors.cpp
index 25e13da5fe..2310847549 100644
--- a/unit_tests/tests/test_sensors.cpp
+++ b/unit_tests/tests/test_sensors.cpp
@@ -7,6 +7,13 @@
 
 #include "pch.h"
 
+TEST(sensors, vrThreshold) {
+	WITH_ENGINE_TEST_HELPER(HELLEN_128_MERCEDES_4_CYL);
+
+	auto& cfg = CONFIG(vrThreshold)[0];
+	ASSERT_FLOAT_EQ(0.8 * PACK_PERCENT_BYTE_MULT, cfg.values[2]);
+}
+
 TEST(sensors, mapDecoding) {
 	WITH_ENGINE_TEST_HELPER(FORD_INLINE_6_1995);