Sorry, not meaning to stir things up but I just find it funny that this post:
was posted by a person who works for Cobb Tuning...and is followed by this:
where fuel pressures are looking very strong.
Again, not trying to stir things up, but that is the same exact problem I had with the AP when I had it. The map said "target 18.5psi" and I was getting 20+. My case is slightly different because I wasn't using the exact mods that the tune called for...so a bit more understandable in my case...but if you're seeing that with just an intake that's kind of sad. Best of luck to you!
SomnoSpeed3,
Glad you got your issue "straightened out", as it were. Going to the colder plugs with a smaller gap should help with your stutter. Keep us posted on that as well.
AutoEuphoria,
We have seen several cases of these exact symptoms being caused by inadequate fueling. The common initial assumption we hear is to blame it on the map. This has happened so often that we have fallen into the trap of automatically assuming it is the fuel pump's fault. Ultimately, as we can see, the datalogging feature is a tool that needs to be leveraged to properly diagnose issues.
In this case, the fault was not with the map, but with the modifications not adhering to the requirements specified in the map notes. The map was designed for a very specific set of modifications, including an intake with an air straightener. Without the air straightener in the intake, the MAF sensor readings would be significanlty different than what the map was designed for, meaning the ECU would not be able to accurately calculate the amount of air in the system as well as the appropriate fueling. In the course of trouble shooting, it is important to verify that the mechanical base is sound and not at fault. That is, if a car has boost leaks, a bad fuel pump or other inappropriate modifications, these are factors that would invalidate the mapping given different assumptions.
In some instances a problem with tuning may be present, but making sure that the basic mechanical functions of the car are up to par is the first step in diagnosing any drivability issue. Granted, the type of hard "fuel cut" could have been an indicator, but datalogging is easy, and as part of the AP package, can give solid data to assist in diagnosing tuning type issues. Requesting datalogs will become part of my troubleshooting analysis going forward.
Since the ECU uses the MAF sensor to calculate everything from fueling to boost targets, altering the intake can cause all kinds of fueling and boost control issues. This is why map notes tend to be rather specific, as was illustrated here, even seemingly benign changes in the intake can result in drastic changes to the car's behavior. Since the addition of the straightener resolved the issue , it appears that this scenario was very similar in nature to others who have had this problem.
Travis
COBB Tuning
