Hi, this is Chris from DC Performance, I'm responsible for the calibration work here, and thought I would chime in. Cammed Vipers tend to buck in the lower rev range to varing degrees, with the amount of bucking depending on the parts combination, compression ratio, O2 senor location, header type, and how it was tuned. If a car is running closed loop with the factory ecu, I have been able to, in most situations, get most of the bucking out. I say most because I have noticed that even the factory cars, especially the earlier models, have a tendency to surge slightly as a result of the normal mixture oscillation that happens when the cars run in closed loop. That being said, I feel that the tolerance level for low speed drivabiltiy varies considerably between people, some people like the roughness with the cam and some people don't car for it at all. A car that has enough cam in it, is not going to run as smooth as a stocker no matter how it's tuned simply because of the reversion that's going on in the intake and the amount of dilution from the overlap. Out here I take the time to carefully tune all the light-part throttle load sites steady state , and make some other changes to reduce the closed loop hunting that can attribute to the bucking or surging that happens at lower engine speeds. We like to run the cars closed loop because most of the cars we tune run catalysts, and many people are concerned with emissions compliance. If that is not a concern for you, there is the option to run the car open loop, which can help smooth things out if the cam is big enough. I'd be happy do discuss this further on the phone.
- Chris
