Hybrid System - Characteristic Acceleration Feel

GROUP
Engine

NUMBER
115

MODEL
Optima Hybrid
(TF HEV) 2011-12MY

DATE
March 2012

SUBJECT:
CHARACTERISTIC ACCELERATION FEEL (OPTIMA HYBRID)

This bulletin provides information relating to the Optima Hybrid which features an advanced hybrid powertrain of the parallel variety. This means that the vehicle can operate under either electric power only ("EV Mode") gasoline engine power only or a combination of the two ("HEV Mode"). The two power sources are selected automatically by an engine clutch which may provide a new and different driving feel to customers who are accustomed to conventional vehicles or other hybrid vehicles.

Part of this new driving feel is a slight oscillation in forward acceleration which may be described as a slight shudder judder or jerking motion. This happens after the powertrain transitions out of EV Mode and into HEV Mode by engaging the engine clutch. This oscillation may occur in multiple situations but it is particularly noticeable when the following combination of events occur:

^ After cold-start; and

^ At low speed (less than 20 mph); and

^ Under light accelerator pedal input (less than 20%).

Oscillations under these conditions can be mitigated by temporarily turning off ActiveEco mode with the steering wheel-mounted eco button or by adjusting driving style (using different accelerator pedal inputs) when circumstances allow. Because the oscillation is reduced after vehicle warm-up the customer may elect to re-enable ActiveEco after the vehicle is warmed up typically after 5-10 minutes of driving time.

Based upon the technology used in the Optima Hybrid this oscillation is a normal characteristic is not an indication of a detect and is integral to the Optima Hybrid powertrain design that maximizes fuel economy and durability.

Kia advises dealer personnel (especially technicians service advisors and sales consultants) to have first-hand experience of the normal operation of Optima Hybrid vehicles under a variety of conditions and particularly under the conditions outlined above. This will ensure that dealer personnel can properly address any customer questions on this topic and can demonstrate normal operation to efficiently address customer concerns without attempting unnecessary repairs and can identify situations requiring further diagnosis (non-characteristic driving feel).