Tony, I respectfully disagree. If you datalog a "mafless" tune on a 997tt, the output MAF values show as 0s throughout the RPM range on the Durametric. However, that is not true for LOAD values. They are calculated/appear as "normal". So how do you think these values are calculated when no MAF sensor is present?

 

OK,,Then you are saying a data log wont show the correct boost over a dash gauge or the test gauge in which both differ in this case??
Then what would be correct to judge it by??..This seems very contradicting over everything you have said in the past about getting real boost from data logging

 

Fast fwd brought up a good question for me. Difference in gas can cause a .2 bar change in boost? As in if I'm running 91 instead of 93 I can lose that much boost? I figured I would be losing a little power but that's a fair amount.

 

Boost is not a measure of power, although they do go together. As Tony points out above, the map provides a target engine load, and the ecu controls the various inputs (injector time, boost, etc.) are adjusted to reach that load, if it is safely possible to get there. Lambda values, knock sensors, inlet air temps, etc. are all part of the evaluation of engine conditions. Some of the inputs, such as ignition angle and boost level are modified to prevent detonation. You can't provide more air than you can provide fuel for.

Lower octane, higher ambient temperatures, higher altitude all will lead to lower power. My max load decreases by about 5% in the middle of the summer when it's hot and humid. Boost goes down as well. OTOH, on cool days in the fall I can reach full target load and the boost is 0.1-0.2 bar higher.

Jon

 

Hmmm....When I was on a road trip once,,,,I only had a choice of 91 octane as the highest fuel their....My boost did show the same on the dash as with the normal 93 octane but the car lost some pulling power and felt slower to me....

 

Thanks for the clarification. I also meant to clarify in that I knew lower grade fuel would result in lower power, but I wanted to make sure that using a lower grade fuel wouldn't actually lower boost.

 

To the OP, where is the sensor for the aftermarket boost gauge located relative to the stock sensor location? Pressure loss due to piping and intercoolers may explain the difference in two readings.

 

I hate threads that never get updated with the resolution.

 

I was told on my MAFLESS tune that my datalogged LOAD% was falacious, a forgazi, but when I did the vbox double take the implied torque and engine power seemed spot on (996 Turbo)