Professional driver. Do not attempt.
The Symptoms
Examples (two) of fuel cuts. Now that ambient air temperatures are very low, 9F (-12C), the air-fuel mixture is so dense that it's going off the ECU's map, and the computer is shutting down the party.
It happens at low speeds also, any gear, typically when boost reaches 17-18psi.
Notice the cuts happen immediately and are terminated as soon as paramaters are normal, in these cases, milliseconds after each cut. In other words, there is no return-to-normal lag or penalty.
I'll get an additional low-speed example up soon.
This is posted here for discussion and its high "shoot-the-sh!t" value, not because I'm having a problem. Simply: it's very interesting to me.
Let's Take This to the Oracle
Robert Arnold at ARD answered my question about it weeks ago, offline. Here it is:
The Answermatthew1 wrote:Robert, with my MBC and "R" ECU (don't know if the ECU factors in this, but there it is either way) I'm getting fuel cutoff at 2/3 up to WOT when boost reaches 17PSI. The fuel cutoff is immediate, and startling.
1997 850 T5 w/ MBC, R ECU, stock injectors, stock exhaust, free-flow intake w/ KnN, clean fuel system, new cap/rotor, synth oil, etc.
Question 1: what is causing the fuel cutoff?
Question 2: what would fix it? Bigger injectors?
It's happening all the time now with the cold air packing more O atoms. In the summer it was very very difficult to achieve cutoff. I've had the MBC in for well over 6 months now.
His reply: a tune. It'll remap that out-of-bounds area to be in-bounds, among other things.
ARD-Lucky wrote:That's pretty typical for a stock ECU, even the R ECU. There is a programmed limitation if air flow and boost go too high on the stock tune. Fixing it would be to reprogram it.
