HowTune

Tuning The Turbo Tweak Velosyty Chip on a GMC Syclone & Typhoon

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There are 7 adjustable settings built into the TurboTweak Velosyty chip for the GMC Syclone and Typhoon. This article will cover all the software and hardware settings in the chip.

This article is based on content of the Velosyty Version 2.0 chip documentation. Their docs are available on their site in pdf format.

You'll need a scan tool that can display INT and BLM (or LTerm) to make adjustments outlined in this article.

As a quick reference, the available settings are:

  1. Fuel in high boost (~15psi)
  2. Fuel in mid boost (~7psi)
  3. Spark Timing at WOT in 1st and 2nd gear
  4. Spark Timing at WOT in 3rd and 4th gear
  5. Initial Wastegate Duty Cycle
  6. Max Boost Target
  7. Air/Fuel target at WOT for closed loop wideband mode (wideband required)
Step by Step Instructions

Verify the Sensors are Working

1

Warm up the truck by running it for approximately 15 minutes.

2

Connect a scan tool and verify all the sensors are reading in the correct ranges.

  • IAC/Idle Air Control: 25-35 (warmed up in park)
  • TPS/Throttle Position Sensor: .60-.90 volts (throttle closed)
  • MAP/Manifold Absolute Pressure: 30-40 kPa (at idle)

The manual says these starting points are crucial to the Velosyty chip!

Selecting a Peramater to Adjust

These settings change parameters that are critical to the safety and performance of your engine. Changing these settings can cause serious mechanical failure to your engine if done without care and paying close attention to your air/fuel mixture and knock retard values.

3

Turn the engine off.

4

Turn the key to the on position. Again, not running!

5

Monitor the value for INT in your scan tool. It should display 0.

6

Complete the following procedure in less then 3 seconds:

  1. Press and Release the gas pedal
  2. Press and Release the gas pedal again
  3. Press and Hold the gas pedal to the floor

If you mess up, turn the key off and begin again.

7

Continue holding the gas pedal. After 2 seconds you'll see the INT value begin to cycle from 1 to 7 and back to 1.

Release the gas pedal to select the parameter you wish to change. Here's the list of parameters again:

  1. Fuel in high boost (~15psi)
  2. Fuel in mid boost (~7psi)
  3. Spark Timing at WOT in 1st and 2nd gear
  4. Spark Timing at WOT in 3rd and 4th gear
  5. Initial Wastegate Duty Cycle
  6. Max Boost Target
  7. Air/Fuel target at WOT for closed loop wideband mode (wideband required)

After releasing, wait a few seconds and verify your selection on the scan tool.

Write down your settings. If the ECM loses power, they get reset!

Changing Parameter Values

The BLM (sometimes displayed as LTerm) on your scan tool shows the current value for each setting.

8

Use the gas pedal to change the values displayed under BLM.

  • Below half throttle will slowly decrease
  • Above half throttle will slowly increase
  • Full throttle will quickly increase
  • Release the pedal to select a value

The value will loop around after reaching minimum or maximum value for each setting.

9

Turn the key off to save the setting.

Repeat as needed. Wait at least 5 seconds before turning the key on again.

Detailed Parameter Settings

1: Fuel in high boost (~15psi)

Add/Subtracts fuel from default WOT fuel values around 15psi of boost. With smaller injectors, you may already have maximum fuel or close to it, so adding more will have little to no effect.

  • Range: +/- 18%
  • Default Value: 128 (no change)
  • Resolution: 1 = 1% change in fuel
  • Minimum: 105 (-18%)
  • Maximum 151 (+18%)

2: Fuel in mid boost (~7psi)

Add/Subtracts fuel from default WOT fuel values around 7psi of boost. With smaller injectors, you may already have maximum fuel or close to it, so adding more will have little to no effect.

  • Range: +/- 18%
  • Default Value: 128 (no change)
  • Resolution: 1 = 1% change in fuel
  • Minimum: 105 (-18%)
  • Maximum 151 (+18%)

3: Spark Timing at WOT in 1st and 2nd gear

Add or subtract timing from default values in 1st and 2nd gear at WOT. Be very careful running pump gas and adjusting the timing. Generally the engine will not tolerate more then 14-16 total degrees of timing at full throttle, though 1st and 2nd sometimes will tolerate more.

  • Range: +/- 8.1%
  • Default Value: 128 (no change)
  • Resolution: 1 = .35 degrees of timing
  • Minimum: 105 (-8.1%)
  • Maximum 151 (+8.1%)

4: Spark Timing at WOT in 3rd and 4th gear

Add or subtract timing from default values in 3rd and 4th gear at WOT (over 55mph). This setting requires MPH signal to the ECM. Without it, this setting has no effect. Be very careful running pump gas and adjusting the timing. Generally the engine will not tolerate more then 14-16 total degrees of timing at full throttle.

  • Range: +/- 8.1%
  • Default Value: 128 (no change)
  • Resolution: 1 = .35 degrees of timing
  • Minimum: 105 (-8.1%)
  • Maximum 151 (+8.1%)

5: Initial Wastegate Duty Cycle

Add or subtract from the initial boost waste gate duty cycle, potentially changing how fast the turbo spools. Too high of a value will produce boost spikes that can damage your engine.

  • Default Value: 100 (no change)
  • Resolution: 1 = .4% change in Duty Cycle
  • Minimum: 105 (-20% DC)
  • Maximum 151 (+20% DC)
  • Higher is faster, lower is slower

6: Max Boost Target

Target max boost in closed loop boost mode. If you're not using the factory wastegate solenoid, this value has no effect.

7: Air/Fuel target at WOT for closed loop wideband mode (wideband required)

With a wideband O2 installed, set the desired a/f ration at WOT. The chip needs to be programed for your specific brand of wideband, and it's analog wideband output needs to be connected to the F14 pin on the ECM.

  • Default Value: 99 (off)
  • Resolution: value / 10 = A/F value
  • Higher is more lean, lower is more rich

The TurboTweak documentation has some additional detailed tuning tips for the 7th Closed loop WOT wideband mode.

Hardware Parameter Adjustment

The chip itself has several hardware based settings to adjust.

First are the 2 rotary dials for Idle Fuel Trim and WOT Fuel Trim. Unlike the software settings, these stay when power is disconnected. They are blended into the fuel curve so they will have a small effect near their areas of effect at idle or WOT. Again, watch your data logs (you really should have a wideband!).

  • Default: 8 (middle)
  • Resolution: 1 ~= 3% fuel
  • Minimum: 0 (-24%)
  • Maximum: F (+24%)

There is also a bank of 4 "Dip" switches:

  1. Select optional second program
  2. Open loop idle mode (can smooth idle)
  3. Full Time open loop mode (never uses closed loop on the stock o2)
  4. Wideband emulated narrowband (allows removal of narrow band o2 sensor)

Switching to the Secondary Program

Keep in mind that your software settings will carry over to the secondary program. If you wish to reset the values, disconnect the ECM from power.

If you did not order a second program, do not change the dip switch.

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