What flat shift and throttle blip actually do
Lifting off for every upshift costs time and unsettles the car. With flat shift, something tells the Elite ECU that a gear change is starting (a shifter load cell, a switch, the clutch switch or a set of conditions you define) and the ECU pulls engine torque for just long enough to unload the gearbox so the next gear can go in. The balance is everything. Cut too briefly and the dogs or synchros clash, or the gear refuses to engage. Cut for too long and the shift feels lazy, then the car lurches when power comes back.
Throttle blip handles the opposite direction. On a downshift the ECU opens the drive by wire throttle to lift engine speed toward what the lower gear needs. That lets a sequential box go down a gear without the clutch, and lets an H-pattern driver rev-match without heel-and-toe footwork. Because the ECU has to move the throttle itself, blip needs drive by wire set up and working first.
Step 1: tell the ECU what starts a shift
On the Wiring tab you have two triggers, and you can use either or both:
- Conditional Trigger: starts a flat shift from ECU channels that meet rules you write on the Conditional Trigger tab.
- Flat Shift Input Enable: starts it from a physical input. What kind of input is chosen with Input Select.
| Input Select | Use it when | Notes |
|---|---|---|
| Flat Shift Switch | A switch wired straight to the ECU signals the shift, such as a dedicated aftermarket load cell with a switched output | You then pick the SPI or AVI it lands on |
| Clutch Switch | You want pressing the clutch to trigger the torque reduction | Configure the Clutch Switch function separately first |
| Load Cell | An analog load cell on the shift lever reports which way the driver is pushing | Adds a Load Cell tab where you calibrate the upshift and downshift voltages |
Wiring a switch: SPI or AVI
A switched trigger can land on either input type, and each is set up differently.
- SPI: set Edge Select to Falling if the switch connects the input to ground when pressed, or Rising if it feeds voltage to the input when pressed. Sensor Type is Hall Effect for any switch. Turn on the Pullup when the input needs something to hold it high while the switch is open, which is the normal case for a ground-switching button.
- AVI: you give the ECU a Switch On Voltage and a Switch Off Voltage. Put each threshold near the voltage the input really sits at in that state, and leave a wide gap between them so electrical noise can't flicker the state. For a ground-switched input that idles near 5 V, we'd call it on below about 1 V and off above about 4 V.
Step 2: pick a mode
The Settings tab decides how the ECU knows the shift is over.
| Mode | When the torque reduction ends | Best suited to |
|---|---|---|
| Closed Loop (where the ECU offers it) | Once Gear Detection sees the new gear, plus a short settling time from the Flat Shift Time table | Sequentials with a gear position sensor enabled in Gear Detection |
| While Active | As soon as the input or conditions are no longer true | Load cells and switches that release cleanly when the gear is in |
| Timed | After the time set in the Flat Shift Time table | Simple setups with no gear position feedback |
Two safety settings sit alongside the mode. Max Shift Time is a ceiling: if the ECU still hasn't decided the shift is finished by then, it starts recovery anyway, so a stuck input can't leave the car with no power in gear. Blockout is a cooldown after each cut during which a new one can't begin, which stops a bouncing signal from firing several cuts in a row.
Step 3: choose how torque is taken away
Torque Reduction Method offers ignition retard, fuel cut, ignition cut, and combinations of those (fuel and ignition cut, fuel cut with retard, ignition cut with retard, or all three). Any method that includes a cut opens a Percentage Cut table, and any method with retard opens an Ignition Retard table. Both can be mapped in up to 3D, 8x8.
Ignition cut is the most common choice and the one we start with. It takes torque away fast and comes back fast. Retard is gentler and can smooth the edges, which is why the combined methods exist. Retard alone generally doesn't remove enough torque for a clean full-throttle shift on its own.
Recovery: how power comes back
| Recovery Method | Cuts | Retard |
|---|---|---|
| Instantaneous Recovery | Restored at once | Restored at once |
| Ramp Out Retard Only | Restored at once | Faded out |
| Ramp Out Cut Only | Faded out | Restored at once |
| Ramp Out Cut and Retard Together | Faded out | Faded out |
Any ramp option adds a Recovery Time table (up to 3D) that sets how long the fade takes. Values usually land somewhere between 10 and 100 ms. A short ramp takes the hit out of the driveline when power returns without making the shift feel slow.
Direction and minimums
Shift Direction limits cuts to up shifts, down shifts, or both. Min TPS and Min RPM must both be exceeded before a cut can happen, so a gentle part-throttle shift around town is left alone.
Step 4: throttle blip on downshifts
| Setting | What it does | Our advice |
|---|---|---|
| Enable | Turns blip on and adds the Throttle Blip Amount and Throttle Blip Duration tables | Confirm DBW tracks its target well before enabling |
| Rev Match Limiter | Applies a soft ignition cut if the blip carries rpm past the Throttle Blip RPM Target, the correct match for the lower gear | Worth enabling; it catches a blip that is too big |
| Min Speed / Min RPM | Blip only happens above both | Keep blips out of parking-lot maneuvers |
| Delay | Holds the blip back by a set time | Useful when the clutch switch changes state before the clutch is really released |
| TPS Correction | How quickly throttle is wound back, per second, once target rpm is reached | Start conservative and refine from logs |
| Gear Tolerance Enable | Adds the Throttle Blip Gear Tolerance table | Use it on H-pattern cars so the blip waits for the clutch |
The Throttle Blip Amount table is the throttle opening, in percent, the ECU commands during a blip. Throttle Blip Duration is how long that opening is held in milliseconds: a cell of 250 holds the blip for a quarter of a second unless an exit condition ends it sooner.
Gear tolerance deserves a plain explanation. The ECU knows the road speed each gear produces per 1000 rpm. While engine rpm and road speed still line up with one of those ratios, the drivetrain must be connected, so the clutch isn't in yet. Say third gear works out to 30 mph per 1000 rpm and the tolerance is 4%. Anything from 28.8 to 31.2 mph per 1000 rpm reads as "still in third," and the blip waits until the ratio falls outside that window.
Conditional Trigger tab
Here you build rules from any ECU channel. Each line has a Select (the channel), a Maths operator (equal to, not equal to, greater than, less than, or the or-equal versions) and a Value. And/Or joins lines together when several things must be true at once. A typical use is only allowing a cut when the car is above first gear and throttle is well open.
Load Cell tab
This tab appears only when Input Select is Load Cell. To calibrate, reset the ECU, open the Flat Shift function again, hold the lever in the upshift direction and press the calibrate button. The captured voltage fills in by itself. Do the same pushing toward downshift.
Each direction also has a Hysteresis: how far the signal has to move back from the calibrated value before the ECU treats the lever as released, or as out of range. It absorbs noise and small lever movement. A good starting point is half the gap between the rest voltage and that direction's calibration. If the lever rests at 2.5 V and upshift reads 3.5 V, that's 0.5 V.
Reading flat shift in your logs
The Flat Shift States channel is the fastest way to see what the ECU thinks is happening:
| State | Meaning | Torque reduction? |
|---|---|---|
| 0 | Min RPM or Min TPS not satisfied | No |
| 1 | Trigger was already on when requirements were met, so the ECU waits for it to reset | No |
| 2 | Armed and waiting | No |
| 3 | Old gear still engaged (Closed Loop only) | Full |
| 4 | Mid-shift; ends according to the mode, or at Max Shift Time | Full |
| 5 | New gear detected, holding for the settling time (Closed Loop only) | Full |
| 6 | Recovery, instant or ramped | Fading |
| 7 | Blockout after the shift | No |
Flat Shift Direction logs -1 for a downshift, 0 for no shift and 1 for an upshift.
Troubleshooting
| Symptom | Usually |
|---|---|
| Gears grind or won't engage | Cut too short or too small, or the trigger fires late in the lever travel |
| Slow shift, big kick when power returns | Cut too long, or instant recovery where a short ramp would help |
| State stays at 0 | Min TPS or Min RPM set above where you're shifting |
| State stuck at 1 | Trigger input never turns off; check switch polarity, edge or voltage thresholds |
| Double cuts on one shift | Noisy input; raise Blockout or load cell hysteresis |
| Blip starts before the clutch is in | Add Delay or enable Gear Tolerance |
Flat shift FAQ
Do I need a sequential gearbox for flat shift?
No. It's most common on sequentials with a load cell, but a clutch switch trigger works for H-pattern cars where the driver still uses the clutch and just keeps the throttle down.
Can I blip the throttle with a cable throttle body?
No. The ECU has to be able to open the throttle, so blip requires drive by wire.
Is flat shifting hard on the drivetrain?
A well-tuned cut is easier on it than a sloppy lift-and-shift, because the gearbox is unloaded at the moment it changes. A badly tuned one is not. If you'd like us to look over your logs, book a free consultation.
