Throttle cut: Difference between revisions
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Finally, the Motronic ME7.1 code can be adjusted to prevent initial boost spikes. |
Finally, the Motronic ME7.1 code can be adjusted to prevent initial boost spikes. |
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[[Category:Tuning]] |
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Revision as of 00:08, 2 September 2006
Definition
Throttle cut is any condition which causes the ECU to reduce the throttle pedal angle, even if the actual accelerator pedal potentiometer is at WOT.
The two main causes of throttle cut are
- ESP activity (a.k.a. traction control)
- The ECU senses that one or more wheels are losing traction. It does this if ESP is enabled and the ABS wheel sensors show a large discrepancy in wheel speeds.
- Boost deviation
- Actual boost pressure exceeds desired boost pressure by around 200-230mbar (3-3.3 psi). The ECU will only restore throttle angle once actual boost pressure falls to at or below the desired boost pressure.
Examples
Throttlecut.csv shows a 3rd gear run where the ECU cuts throttle.
Notice the throttle plate angle drops suddenly from 100% to 43%-48% when the deviation goes over ~200mbar.
| TIME | RPM | Throttle Plate Angle | Boost Pressure Desired | Boost Pressure Actual | Deviation |
|---|---|---|---|---|---|
| 497575 | 4025.75 | 99.6078431372549 | 2327.109375 | 2490.625 | |
| 497645 | 4046.75 | 100 | 2315.1953125 | 2508.90625 | 193.7 |
| 497716 | 4114 | 100 | 2302.1484375 | 2503.0859375 | 200.9 |
| 497786 | 4151.5 | 99.6078431372549 | 2271.1328125 | 2508.2421875 | 237.1 |
| 497856 | 4200.5 | 45.8823529411765 | 2263.1640625 | 2488.203125 | 225.0 |
| 497926 | 4230 | 43.921568627451 | 2248.3984375 | 2457.65625 |
Notice the throttle does not return to 100 until the boost pressure actual returns to almost exactly the boost pressure desired.
| TIME | RPM | Throttle PlateAngle | Boost Pressure Desired | Boost Pressure Actual | Deviation |
|---|---|---|---|---|---|
| 499748 | 5183 | 48.2352941176471 | 2200.546875 | 2222.8515625 | |
| 499819 | 5211 | 48.2352941176471 | 2208.0078125 | 2226.5625 | 18.6 |
| 499889 | 5246.5 | 48.2352941176471 | 2216.2109375 | 2217.34375 | 1.1 |
| 499959 | 5294.5 | 77.6470588235294 | 2220.234375 | 2194.8046875 | -25.4 |
| 500029 | 5319 | 100 | 2227.1875 | 2166.2109375 |
Getting rid of throttle cut
The easiest way, by far, of eliminating throttle cut is by using Lemmiwinks to cut SEL Scaling. However, this also reduces maximum horsepower, so it is not the optimal solution.
Another solution is to use the "3/4" throttle mod, which prevents the driver from pushing the throttle to 100%. This, however, can also reduce overall power.
A master boost controller in parallel can be used to set a hard limit on the actual boost.
A throttle cut defender can be used to "trick" the ECU into thinking the actual boost is lower than it is.
Finally, the Motronic ME7.1 code can be adjusted to prevent initial boost spikes.