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'''This page is dedicated to Low-Z injector tuning, at BMW M30B34 turbo engine.''' Injectors are the stock ones for this engine: Bosch part no. 0 280 150 200, maybe 270-300 cc/min @3/3.5bars (different sources say different values). R=~3 Ohms. ---- My previous calculation was for required fuel: Req_fuel = 6.49 * (D / N / I) = 6.49 * (3450 / 6/ 300 cc/min) = 12.44 ms = 0x7C Which seems to be on the high side. (So the injectors are not 'so' big for this displacement). But engine was flooded with those values, finally I ended up with a Req_fuel of 5ms, and still I've got VE values of 20-30 (decimal) near idle. Idle is ~1ms pw. I guess something is wrong with injector settings. I worked with the following settings: http://quasar.dynaweb.hu/~lezsi/bmw/attila/attila-injsettings.gif '''UPDATE''' 2006.01.22 Installed powerflyback, and everything changed a lot! I had to raise VE table to 3-4x values, which are close to previous calculations. I guess it's because of much more quick injector closing time. After that, we were able to tune the car in an hour. Thanks, powerflyback! :) The bad news is, after that we've killed some (10A) fuses (powering the injectors). Changed it two times, but had no chance to find reasons there (-8 degrees C, some snow, hard wind and dark). Finally we felt burned smell from the GenBoard... Fortunately the car almost brought us home before (no point to tow on the front). No more details yet, but I guess, it has something to do with bad GND connections (which were verified many times before...), and the favorite point of failure. :( ---- '''Obsolete''' I guess a PowerFlyback couldn't be a bad choice here. If you're interested [http://quasar.dynaweb.hu/~lezsi/bmw/attila/datalog200512302240run.xls here's] a datalog with starting, badly oscillating idle, and cruising home with unmapped car, etc. For analysis I suggest my actual favorite: [http://www.ideasandsolutions.biz/MegaLogViewer/ MegaLogViewer] the first program which knows everything I wanted, not buggy (just a bit slow -java) * Have you tried divider 2 (or is it 3 for 6cyl? I dont know), so no injection on every rotation -> twice longer pw. ** I'm not sure about inj calculations (and manual doesn't cover divider config), but let me guess: if (alternate+1)*divider should be equals to 6 in my case, then if I use divider=2, then I need to use alternate=2 which means to me that I have to form 3 injection banks? ** If above equation is true, using divider wouldn't twice inj-pw but cut into half! Please correct me. *** Divider means you get squirt every Nth trigger, Mostly suitable if you have injectors in banks. Doesnt affect pulsewidth at all. //Emil *** OK, I shouldnt say anything that I don't really know. I remember doubling pw from megasquirt, used with coil triggering. -OK, i feel totally lost. What happens if I change my divider to 2? '''A:''' with divider = 1, every trigger event results in a injector pulse, but if you wire up the injectors in pairs, you get all injectors opening twice per full engine cycle, which makes idle harder to tune and other negative effects. In that case, configuring divider = 2, injectors will only fire every second trigger event, and get the injectors to fire only once (per injector) for every full engine cycle (720 degrees on 4-stroke). //Emil * Powerflyback may help if pw is near 1mS, someone else may know it better. If (injpwm14 + multfact(VBatt) * injpwm6 ) > 100% (at certain - low enough - VBatt) than it is railed at 100% (since that is the limit of the duty) * To keep same current, example if pwm@14v=30% pwm@6v=70%, so is injpwm6=40% correct? Or what is this multfact(VBatt)? ** In my mind that seems correct.
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