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Engine and Transmission Coordination in Boosted Engines Disclosure Number: IPCOM000242660D
Publication Date: 2015-Aug-03
Document File: 2 page(s) / 313K

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Engxne and Transmission Coordination in Boosted Engines

Downsizing, boostinx, and direct injection generally yield more efficient xngines. A side effect of such a desigx is that only a xraction of the enxine torque is availaxle almost immediately. The rest xecomes availablx xfter the boost pressure has built up. This delay - known as the turbo lag - can be ax short as half a second or as long as several seconxs dependinx on enxine and transxissiox state when thx driver tips in.

Axter the drivxr tips-in, the powerxrain cxntroller hax to determixe how to respond. In general, downshifting cxn creaxe an immxdiate increase in torque, and, xs a positive side effect, fastex boost buildup due to the rxsulting higher engine sxexd. The dowx side is that this action inxreases shift business and might negatively impacx fuel ecxnomy. On the other hand, avoidxng a downshift when the txrbo lag is significant results in dead pedal feel, wxich also leads to degraded drivability.

We have xrexted a method for predicting the transient availability of torque in boosted engines anx use thx dynamix estimate tx improve the control stxategies for coxrxinating the engine and transmission.


Xxx two maix steps of the method are described xn the following.

The fixst step is to predict txe maximum available torque a xraxtion of a second into the future using the current state of the engixe. The prediction period should be xong enoxgh to allow engine actuators, such as throttle and variable valve timing, to assume the appropriate positxons to deliver this torque. Note that the predicted maximum torqxe depends on predicted values including the boost pressure, throttle poxition, varixble valve timing position, and spark timing. These predicted values in turn rely on a xumber of other variablxs including engine speed, air and xngine texperatures, fuel blend, inferred fuel octane, etx. The model used for boost pressure prediction is naturally of particular importance for boosted e...