hello all... I was wondering the process of upping the speed of a truck that has a governor cap or speed restriction on it.. It is a 03 diesel truck made by GMC. I believe it is a w-series.. a box truck. Are they usually mechanical or computer? Thanks!
I'd be surprised if it wasn't built into the ECU. Are you talking about the factory limit or something much lower that your boss is imposing on the fleet? To get past it you will need to get an aftermarket ROM from some tuner supply house. There's a lot of that kind of gear available for the PowerStrokes, so I am sure you will find what you want for the Chevy.
If you are talking about bypassing the factory limit, why would you want to? I can understand why you would want more power or torque to get to max speed quicker, but changing what that top speed is is asking for trouble. There is a reason why you don't see pickups out at Bonneville breaking land speed records. Even on quarter mile strip I doubt this truck could get to whatever the governed speed is. Either you are trolling or crazy.
Just for kicks, what is it the governor set at?
The ROM is were the parameters and lookup tables for the ECU are stored. A programmer would talk to an aftermarket ROM - not really a ROM in the literal sense at that point - to update those parameters, either while it is plugged into the vehicle or plugged into the programmer. Shop around to see what the aftermarket shops are offering.
The modern computer controlled diesels are grossly detuned on purpose to maintain efficiency emissions. Besides getting past the speed governor, you'll probably also be able to play with the available power output. Don't expect Chevy to extend warranty coverage to any mods, though.
You'll need to get in touch with the tuner shops to see what exactly each offers.
Adjusting the top speed will make NO difference in the pulling power of the engine. It is a setting in the ECU that looks at the speed sensor and the rpm of the vehicle and cuts fuel flow to keep the vehicle from exceeding 70. It is not the reason why it will only climb hills at 60, that is because it only has enough power to climb that hill at 60, if it had enough power to climb it at 70 then it would still run 70 until it hit the governed speed.
As for changing the top speed, that can be done by a dealer BUT they probably will want you to sign a waiver to cover them in the event the higher speed causes a problem. You might want to look at the tires on that vehicle as well, they may not be rated to handle higher speeds.
Not to mention that driving on highways with an 80 MPH speed limit in traffic with trucks that are arbitrarily limited to 70 is frightening and dangerous, both for the truck driver and for the rest of us.... Been there/done that!
That said, setting the governor at 80 will NOT improve the uphill speed of the truck at all. That is a simple power/weight+drag ratio problem. The truck is underpowered, and even if the governor is set at 80 it will still drop back to the same speed on an uphill grade that it will with the governor set at 70.
I did not say that the two were related, just that the two were both equally tunable. The ECU controls all those things, so I mentioned that changing out the stock parts could have many more benefits than just changing the top speed. Changing the ECU programming will be able to address both issues. Adjusting fuel timing and volume are just as much a function of the ECU as rev and speed limiting.
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