[Subscribe to Daily Digest] |
My take, with the T5, is that the fuel cut point in the ECU signifies that the ECU has kown workable maps up to that point. So I see that there are no issues at all. I cannot see a situation where they would engineer the maps to go to the fuel cut pressure if there was not enough fuel to get there. And we know that the 2.0L NG900's can be taken up towards 20 psi with the Abbottized ECUs without going lean. So that is a good guide to the fuel delivery capacity of the NG900s. The experiences with modified ECU's on the 9K's should tell a similar story.
As for adaption... The interaction of the fuel system relief pressure, state of injectors, air intake temperature sensor and O2 sensor, with the ECU, causes the ECU to work out some correction constants or tables to calibrate these relative to the O2 state. This occurs under off-boost condtions while cruising etc. So this process has nothing to do with boost at all. When on boost, the ECU runs rich and the O2 sensor is overwhelmend and the ECU is running open loop. Now the ECU is using some of the parameters gathered during off-boost contitions in calculating the on-boost fuel mapping, but there is not adaption done or attempted while on boost. Now while on boost, the system may adjust timing, richness and possibley boost if the trionic thinks that there are knocking condtions, but that is kkock adaption, not the same thing. And with an MBC and the BPC valve isolated (or removed), the T5 works very well without the ability to reduce boost pressures.... but use good fuel, low restriction inlet and exhaust and keep the plugs in good shape and injectors clean. You can't be boosting a engine that is not well maintained.
Brad has reported and others have... inserted a resistance into the MAP sensor output lead to fake out the ECU. When this is done, the ECU will adapt to the off-spec map sensor to get the mixtures back on target. Depending on the amount of resistance used, this can involve a lot of coughing and sputtering until the ECU figures things out. This is a good indicator of how adaptive the T5 ECU is. For larger amounts of resistance the fuel pressure must be increased to allow the adaption to complete. So this is not something that folks should be doing just because they read about it on the BB. But is does serve to illustratre how the ECU adaption works. ... and the fuel cut set point is moved so a stock ECU-BPC arrangement can have lots of boost without fuel cuts, and the APC knock protection is maintained. Or one can use a MBC and have the fuel cut moved.
posted by 208.24.179...
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
