Having trouble tuning the car. Graphs on the datalog are very jumpy. Speed and RPM will jump 10+mph and 1000rpm, respectively. On the cluster the speedometer will freak out. Drop to zero then sweep back to where it's supposed to be.
We've swapped the computer, cluster, and speed sensor and nothing has changed. We've gone over all the wiring, everything looks good. We cut power to all aftermarket electronics (boost controller, turbo timer, gauges, radio). No change.
We've also run without the alternator or ABS thinking it might be RF interference. No change.
Tuner read the speed and crank sensors with an oscilloscope and said they look good. Problem must be downstream of the sensors somewhere.
The tuner was also suspicious of his equipment, but isn't seeing the problem in any of the other cars that he has tuned.
We're using SCT. The yellow line is speed, red is rpm, blue is air flow (lb/min).
![Image]()
We've swapped the computer, cluster, and speed sensor and nothing has changed. We've gone over all the wiring, everything looks good. We cut power to all aftermarket electronics (boost controller, turbo timer, gauges, radio). No change.
We've also run without the alternator or ABS thinking it might be RF interference. No change.
Tuner read the speed and crank sensors with an oscilloscope and said they look good. Problem must be downstream of the sensors somewhere.
The tuner was also suspicious of his equipment, but isn't seeing the problem in any of the other cars that he has tuned.
We're using SCT. The yellow line is speed, red is rpm, blue is air flow (lb/min).
