Author Topic: Injector Duty Cycle & AFM questions (Read 7303 times)

bearsbmw · « **Reply #15 on:** November 29, 2008, 01:50:24 AM »

Quote from: bmwman91;61893

The injector duty cycles are controlled by (in no particular order):
AFM (primarily)
Intake Air Temp.
Coolant Temperature (warm-up enrichments)
Throttle Position
Exhaust Gas Oxygen Content*

*The O2 sensor's input is only used below 85% throttle & 4000RPM, if I recall correctly.

Keep in mind that the AFM's signal is the load-variable's primary input, and that ignition timing is directly affected by the ECU's computed load value at a given instant. Tweaking it might cost you some performance due to incorrect ignition timing, or a whole motor.

What exactly are you working on here? I saw evidence of boost......

well the idea is cheap and simple ... I plan to falsely send a signal to the ecu from both knock senors and using a map sensor and a small home made computer for anything over 8psi with correct size injectors afm ajustment not sure if it will work or not but I like to mess around

bmwman91 · « **Reply #16 on:** November 29, 2008, 10:16:55 PM »

Quote from: bearsbmw;61904

well the idea is cheap and simple ... I plan to falsely send a signal to the ecu from both knock senors and using a map sensor and a small home made computer for anything over 8psi with correct size injectors afm ajustment not sure if it will work or not but I like to mess around

Good stuff, experimenting is always fun stuff. When you say homemade computer, are you talking about using a microcontroller & some custom code or something, or Megasquirt / etc? I am all about custom microcontroller apps!

bearsbmw · « **Reply #17 on:** November 29, 2008, 11:29:15 PM »

Quote from: bmwman91;61943

Good stuff, experimenting is always fun stuff. When you say homemade computer, are you talking about using a microcontroller & some custom code or something, or Megasquirt / etc? I am all about custom microcontroller apps!

yes microcontroller and someone to right me a Mini App for it with USB connection... I was thinking maybe use a old black berry and flash it with new software ...I realy have no idea what im doing but I have all winter to screw around ... the reason I started all this stuff is that buddy is runing 14psi on a m42 stock internals and 2 extra injectors in the intake and no spark tune and the motor run's fine when boosting... It's starting to get to me and I need to find out why the ECU is allowing for it and it's not like he's been driving around for a day or two this way... he has been in the that range for a few years

bmwman91 · « **Reply #18 on:** December 01, 2008, 10:04:45 AM »

Quote from: bearsbmw;61950

yes microcontroller and someone to right me a Mini App for it with USB connection... I was thinking maybe use a old black berry and flash it with new software ...I realy have no idea what im doing but I have all winter to screw around ... the reason I started all this stuff is that buddy is runing 14psi on a m42 stock internals and 2 extra injectors in the intake and no spark tune and the motor run's fine when boosting... It's starting to get to me and I need to find out why the ECU is allowing for it and it's not like he's been driving around for a day or two this way... he has been in the that range for a few years

Very interesting. I haven't heard of 14psi on stock internals on the M42 before, but I'll take your word for it. Has your friend dyno'ed it or anything yet?

bearsbmw · « **Reply #19 on:** December 01, 2008, 10:41:42 AM »

Quote from: bmwman91;62031

Very interesting. I haven't heard of 14psi on stock internals on the M42 before, but I'll take your word for it. Has your friend dyno'ed it or anything yet?

no dyno yet... faster then my 8psi for sure...I need to see a m42 stock ignition map to figure things out

roundel318 · « **Reply #20 on:** December 02, 2008, 08:24:02 PM »

have you asked your friend what he uses?

bearsbmw · « **Reply #21 on:** December 02, 2008, 08:36:09 PM »

Quote from: roundel318;62135

have you asked your friend what he uses?

what should I be asking?

bearsbmw · « **Reply #22 on:** January 03, 2009, 02:41:11 PM »

well after talking to a good friend of mine and figuring out how to do a crude tune with almost zero budget we figured it out and it's so very simple! using 36# injectors I'm able to control idle with AFM ajustment...Next thing is the TPS.. we all know that when your on half throtle your car will start to boost and the ECU does not like it at all and you can see knock very easly on hot days so to get around this we wired a 1psi boost activated On/off switch on the signal line for the TPS therefor tricking the ECU and making it think its in WOT postion when your only half... were still working on ECU adaptation

roundel318 · « **Reply #23 on:** January 03, 2009, 07:33:08 PM »

interesting, good update

bearsbmw · « **Reply #24 on:** January 04, 2009, 01:18:53 AM »

I need to find a away to simulate the electrical fluctuation of a normal cycle o2 sensor and keeping the ECU happy ... Not sure how this will be done yet but will take any suggestions ... thanks!

nuvolarossa · « **Reply #25 on:** January 04, 2009, 02:20:59 AM »

Quote from: bearsbmw;64010

I need to find a away to simulate the electrical fluctuation of a normal cycle o2 sensor and keeping the ECU happy ... Not sure how this will be done yet but will take any suggestions ... thanks!

I'm trying to do that with the analog output from my wideband (innovate lc-1), but until now I get only ground issues and the value that ecu see goes negative, thus ecu show the error about the wrong voltage...
you need to trick the heater system of the lambda sonde otherwise it will show the error for that too.

there are some circuits that plug directly on the lambda connector, search with google for "o2 simulators"... be careful, not all simulate the fluctuation (some send a fixed voltage)... ECU is not happy with a fixed voltage, it needs the fluctuation.

I'll try more in next days to solve my problem with a multimeter!

tricking the TPS will change the load that the ECU sees so it will change ignition timing too... you need to check HOW MUCH

bearsbmw · « **Reply #26 on:** January 04, 2009, 02:32:25 AM »

Quote from: nuvolarossa;64014

I'm trying to do that with the analog output from my wideband (innovate lc-1), but until now I get only ground issues and the value that ecu see goes negative, thus ecu show the error about the wrong voltage...
you need to trick the heater system of the lambda sonde otherwise it will show the error for that too.

there are some circuits that plug directly on the lambda connector, search with google for "o2 simulators"... be careful, not all simulate the fluctuation (some send a fixed voltage)... ECU is not happy with a fixed voltage, it needs the fluctuation.

I'll try more in next days to solve my problem with a multimeter!

tricking the TPS will change the load that the ECU sees so it will change ignition timing too... you need to check HOW MUCH

Intresting!! I didn't know there was sims with fluctuations... thought they were all fixed ! either way you look at it, the TPS trick is better then what was going down befor and at WOT the computer would retard the timing by default I would think/hope lol ... I could be wrong ! I wish I could see some Fuel and Ign map's for this motor GRRR!