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This '''audi 5cyl works''', but experiences "idle fluctuation problem" We've created this editable page to be able to help him, summarize the findings, suggestions in a thematically organized way. * does it rather happen with cold air/warm air ? ** cold engine / warm engine ? We've experienced that '''similar idle problems are often caused by VE table'''. Can be very sensitive in some cases. Because of the wideband measurement and EGO delay it's hard to diagnose properly (the leaning shows up later in the log than the actual problematic loadsite). In '''many cases the idle fluctuation was cured when the VE was fixed at the right loadsite'''. * Temporarily '''disabling EGO correction''' (or even permanently for idle) also worths a try. ---- * injector size= ?? ** req_fuel= ---- '''History''' - Mattias wrote on chat: * some guy with an Audi 5 cyl posted on [http://www.vemssupport.com/forum/index.php/topic,1503 this forum thread] * he was having trouble with the engine falling through when letting it down to idle http://www.savarturbo.se/~mattias/motor/vems_data/log-pics/overrun-1.png http://www.savarturbo.se/~mattias/motor/vems_data/log-pics/overrun-2.png At that point, fuel should be resumed after overrun, shouldn't it? Expression grid says ecu pulse width = 0, and so it is.. but the overrun fuelcut settings don't say so. ---- '''LOG FILE''' http://ranz.planet.ee/idle2.vemslog '''Important''': In the log he tries at first with no overrun fuelcut, later with the ones in my screenshots. Interesting thing after TPS pulse during engine breaking and RPM is falling, '''observe injector pulsewidth''' : * There are 3 tps pulses in the log. After the TPS pulse when the RPM is falling the pulsewidth is not 0, and match with the VT calculations. The two later pulses when RPM is falling the pulsewidth is 0 and does not match with VT calculations in expression grid. You can see the config change around 22 seconds into the log (orange marker in the multigraph, see picture above). Changes to '''overrun fuelcut''' goes from : *pressure based: 0 -> 18kPa *Fuelcut rpm: 8000 -> 2500 rpm *Fuel resume rpm: 500-> 1800 rpm In the log the fuel resumes at higher pressure than 18 kPa and at much lower RPM than 1800 rpm. So the settings are not interpreted correctly. More like 25 kPa and at 1174 RPM, which is not intended. '''Other observations on the configuration''' * MAT/TPS enrichment table is wrong, should be copied from a default firmware config to enable proper scaling with MAT. * MAT/TPS ignition retard is not too safe for turbo * Boost target is above fuel cut ---- '''The log/config has some config errors which WILL cause idle problems.''' (Reidar, some of these were suggested in the forum thread already. All the config changes are in the log file, look above how to see this) IAC PWM Frequency: is set to 250hz. 25hz works fine on the audi aan/aby/adu/3b Set the whole idle area in the Ignition table to the same ignition advance.. 15deg on idle or so. The PID settings is somewhat off in my opinion and experience with these cars. '''P''' = Increase this, try value: 70 '''I''' = Lower this value, try value: 3 '''D''' = Increase this value, from experience a really high D often helps on cars with AirCond where they got stall issues when AirCon active, try a value of 150. Use the ignition based idle control to get a steady idle. I usually tune it a bit rich on idle. 0.95 or so.
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