Premium octane fueling maps
Brett Dikeman
brett at cloud9.net
Thu Mar 6 17:37:43 EST 2003
At 11:54 PM -0500 3/5/03, Suffolk GameServer LAN wrote:
>Q: On 3B motors does it matter the number of starts to get
>back to the premium octane map in the ecu?
There is an adaptive value or two for fuel quality.
>Reason I ask: I use 87 octane
The owner's manual says the engine requires 91 octane.
> and never dip far into the turbo ( in fact car so new to me I
>haven't but once ) except there are track events where I fill up
>with super to get the most out of the motor.
It's not a matter of "getting the most out of the motor", it's a
matter of "not blowing up the motor." The 20v -requires- 91 octane.
In the winter with temps so low and charge air temps low as well,
it's -possibly- OK for now.
Especially if the engine is not chipped, don't waste money on race
gas at the track. If you're nervous, find a station with 93 or 94
octane.
>So back to the 3B: Does the fueling map reset after each start or is
>there some "proceedure" I should follow?
Ignition retard is quick, but building back up takes time. I believe
whereas the CIS units switched back after a certain # of starts(was
it 20 or so? Been so long since I owned my 5kCST), the 20vt works
over time.
The ECU will keep trying to go back to normal ignition timing and
boost levels, and it won't back off again until it gets knocking.
As for resetting the ECU, pull the two fuses under the red "MOTOR"
cover in the fusebox, leave them out for a minute or so. Probably a
good idea to wait until the ECU has finished the MAF burnoff cycle,
too, before you yank the fuse- I know disconnecting the MAF or ECU
during the burnoff will do very nasty things, don't remember if the
same is true for yanking the fuses.
Resetting should be done any time the injectors(or fuel pressure
regulator) are serviced, O2 sensor is changed, ISV system is cleaned,
vacuum leaks are fixed, etc. Note that you will get poor mileage,
idle might be off a little too for a bit as the system re-adapts to
the engine. I think lambda adaptations are mostly complete after
about 50 miles mixed driving.
Brett
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