In the US, on 93 models, the ECU was programmed for a leaner deceleration
mixture. A direct consideration for improved mileage. Some riders, do to
their riding style, could produce a stalling condition under decel with a
stock 93 ECU. Yamaha US had enough complaints that they adopted the use of
the European Spec ECU for stock application on 94 models of GTS. The position
of Yamaha US was that these European spec ECU's addressed the decel stalling
issue only. George P has a 93 GTS that got updated to the 94 ECU. He did some
head to head comparisons of performance, specifically addressing the low RPM
surge. My memory of his comments were that there was no difference in the
surge between the 93 and 94 ECU. He did note a decrease in gas mileage.
George also removed the cover from the ECU for inspection. I don't remember
specifically what he found, but I do remember him not seeing any area that
would easily be modified to improve the low RPM performance. George? HELP!
Anyhow, that is what I know about the ECU issue. Not being from Europe, and
based on the way the 94 ECU was represented in the US, it sounds like their
ECU was always the same between 93 and 94. After that, I have no idea because
the US stopped importing them.
RSRBOB
