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Sun 7 Dec, 2008 02:48 pm
My 2005 Pontiac Grand Prix with the 3.8 L single exhaust moter 47K miles ,seams to have floating valves at 116 or 117 miles per hour under full excelleration. Does this seem likely? Twice at the speeds listed the car basically started decellerating? Its not possible that GM installed a govener on these cars is it? If so out it goes. Of course this is at the track.
Thanks very much,
Frank
Absolutely... GM put top speed limiters in almost every EFI car they produced from 1985 to present.
The computer in your car starts limiting fuel delivery at its top speed. My 91 Beretta was limited to 110. My 96 Impala SS is limited at 125 which I removed.
Its not a floating valve issue. The valvetrain in your car is designed to prevent float up to and above redline. Provided you aren't exceeding redline at those speeds, its not valve float.
Well, fan me with a blowtorch. I never dreamed they would do that. Does it actually limit speed, Curtis, or rpm?
Both. The RPM limiter starts dropping spark from random cylinders. The top speed limiter drops fuel injection from random cylinders to maintain a max speed.
My 91 Beretta just shut off completely at 110, then kicked back on around 100. Nothing like shitting your pants when your car shuts off at 110 and the wind resistance gives you a half a G of braking.
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