high/low boost computer settings

[warpz0r]

hi all

another question about afc's/computers

if i have a low boost setting and a high boost setting, does that mean if i have a rechipped computer in my rb20det, it would only be tuned for the High boost setting?

so the low boost setting would be rough and wasting fuel and stuff?

[666DAN]

Unless you've got an R34..then the remapped stock ECU will not adjust to the boost being supplied but to the AFM signal...so if your computer is tuned for higher boost, it will waste fuel and lose performance at lower pressures...as the AFM signal isn't the most accurate thing in the world.

[Trust33]

Does this problem occur with a pfc and an ebc running hi/lo.Would you need to get a pfc boost controll kit to overcome this problem.

[Sydneykid]

The AFM is the best device yet invented for measuring airflow. Boost is irrelevant, it's airflow that makes power and the ECU knows how much airflow (via the AFM) so it adds the programmed amount of fuel for that airflow. For constant throttle cruise and idle it runs closed loop, so it constantly adjusts the A/F ratios to maximise the fuel economy and minimise the emissions.

There is no"problem" with the standard ECU, other than its (open loop) programmming is usually a bit rich. A properly tuned Power FC has no such problem of course.

Hope that helps:cheers:

[Trust33]

Thanks Sk....So now i understand that the fueling is controlled by the afm and cpu to get the correct afr's.And it can also be done with no afm at all on certain cpu's.

[Sydneykid]

....it can also be done with no afm at all on certain cpu's.

Correct, but not as accurately, they use manifold pressure in the algorithm (with rpm, throttle position etc) to calculate the airflow. The AFM actually MEASURES the airflow.

[666DAN]

The AFM is the best device yet invented for measuring airflow

I wouldn't tend to agree with that when talking about the hotwire type though, MAP sensors are more reliable though for the ECU to react to boost levels, there for adjust timing to suit.