Steve, the SEST will not allow me to populate all the cells in the AFR at 14.6 Is this a limitation of the SEST or or is it just not possible to set those cells to 14.6. Does the VTune software carry this limitation?

 

You can set the AFR to 14.6 for all RPM cells from 20 MAP to 90 MAP. MasterTune will only allow 13.5 MAP in the 100 MAP column.

Once the V-tune is complete you can then re-set them to your desired normal operating AFR's.

B

 

Any cell that cannot be set to 14.6 cannot be tuned with the factory switching sensors. This will also screw with the adjacent cells too! The ECM just does not switch off then on, it works on a weighted average type system. There are also other behind the scene limits that may take effect while the engine is running event if the cell is set to 14.6 so one must know whats going on as it may not be at 14.6 just because you put it there!

Like I said before it's just not that simple!

 

i have a 2008 rocker just put a 2 into one vance hines pipe only and have all kinds of answers from dealers on the tuners some say i dont need one some say i do if i change the air intake. looking for some answers . not looking for more power just looks

 

I understand that just because I set the AFR in a cell to 14.6 that doesn't necessarily mean that the actual AFR at that point is 14.6, but doesn't it mean that closed loop is turned on for that cell? So the VE information returned in that range should be accurate. Correct?

The VE information does come from the O2 sensors doesn't it?

Not trying to debate anything here, just want to learn.

 

Your Rocker should be fine. My understanding is that the EFI system can make this aedjustment for pipes. How does it run? Does it backfire, pop, feel weak?

 

Take any 4 cells of information and the ECM does what's called a weight average to produce the values that it uses. Now mind you that's not all it does but this should give you the basic idea. So it takes all 4 values and comes up with an answer. So if any of the 4 cells are not 14.6 on the AFR table the data being returned is open loop data and the O2 sensors are not being used. If they are not being used you cannot tune with them.