|
Title: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on January 05, 2015, 11:50:05 AM Ok friends. I have another doubt that I want your advice.
First ECU family is M383/M592 and this is the configuration: bigger injectors (+58%), bigger MAF housing (+27% linear scaled) and injectors factor (-58% scaled). With that factors LTFTs (Idle and Partial Load) are around +7%, but on boost fueling is something nice with some spots only, but not bad at all. Driveability is nice, idle stability with and w/o load is excellent, temperature compensation is quite good for a simple scalation, accelaration enrichment is good (don't overfuel), startups are ok (cold, warm & hot) and decceleration is nice (not overfuel too). But if I increase injectors factors to match LTFTs, almost everything is messed up, not badly but it losses nice like stock driveability, idle hunting, hot startup got bad, acceleration enrichment got something bad (some overfuel) and decceleration got bad too (some overfuel too). Then I have looking for info about it and found two routes, some people dial injectors factor for fuel trims, but others talks about MAF curve tweak for proper trims. My doubt is changing or dialing MAF curve also LOAD curve is modified too, with it possibility to make things worst. What do you think???? I have read that a simple but proper injector factor, LOAD and MAF curve scalation will let ECU tweaks to a minimum, talking about temperature compensation, acc enrichment, cold & hot startups. Then can you elaborate how do you do MAF Curve dialing during this situation??? What do you recommend friends???? Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: seishuku on January 05, 2015, 02:09:12 PM Personally I shudder when I see people changing the MAFS curve to correct fueling...
It's just like putting an SAFC on the car, yeah it changes fueling, but it also affects timing, which may work, but it's not the correct way to do it. Especially when you have access to full ECU parameters. Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: nyet on January 05, 2015, 02:34:18 PM Personally I shudder when I see people changing the MAFS curve to correct fueling... Not if the fueling is off because the MAF curve is wrong :) Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on January 05, 2015, 04:12:39 PM Not if the fueling is off because the MAF curve is wrong :) Then the right procedure is use or calculate a MAF Linearization or Transfer Curve as best as possible to the real one (for an specific sensor in a defined housing) and do not touch it. Right???Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: nyet on January 05, 2015, 04:35:16 PM You can do it empirically too
1) if you know you have your fueling parameters 100% dead nuts on *everywhere*, you can tune MLHFM/KFKHFM via fuel trims and/or comparing with wideband if you have a narrow band car (assuming you don't have any boost or vac leaks etc). or 2) you can compare ps_w to actual boost and make HFM calibrations accordingly (assuming you don't have any boost leaks or dv issues etc). However, if you are truly working with no known good parameters, you should get the MAF (INCLUDING ENTIRE INTAKE SETUP) flow bench tested as a starting point. Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on January 05, 2015, 04:53:13 PM You can do it empirically too 1) if you know you have your fueling parameters 100% dead nuts on *everywhere*, you can tune MLHFM/KFKHFM via fuel trims and/or comparing with wideband if you have a narrow band car (assuming you don't have any boost or vac leaks etc). or 2) you can compare ps_w to actual boost and make HFM calibrations accordingly (assuming you don't have any boost leaks or dv issues etc). However, if you are truly working with no known good parameters, you should get the MAF (INCLUDING ENTIRE INTAKE SETUP) flow bench tested as a starting point. I have the info about MAF. In fact I am going to bigger MAF housing. OEM MAF is HFM2 type with 61.7mm ID VW#037906461C Bosch #0280217117. New housing is 69.7mm ID (measured with caliper) VW#021906462A Bosch #0280217504. I have OEM MLHFM, do you think my best bet is do a simple linear scalation using areas relation? Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: nyet on January 05, 2015, 04:57:10 PM I have OEM MLHFM, do you think my best bet is do a simple linear scalation using areas relation? Ya, but it will likely read a bit high. Start with that, then see where ps_w is. Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on January 05, 2015, 05:12:27 PM Ya, but it will likely read a bit high. Yes but I am using a GT2560R turbo for 300BHP estimated @ 20-22psi max. I don't want to send MLHFM curve too high to pass my 12.75ms ECU limit. I have been investigating about an exponential scalation too, to avoid this issue.Start with that, then see where ps_w is. I read something like scaling OEM MLHFM from -7% to +36%. Off course I could tweak my curve to match the linear scaled one at the lower to middle zone (vacuum & boost transition zone) but growing up a little more going to VR6 final step one (for example or maybe a little less) allowing me more range of work without sending LOAD readings too high. What do you think? I comment all this because I know my big MAF housing could support it going barelly to it limit. But it should work. Also I can tweak it a little via KHFM. PS_W is intake manifold absolute pressure, right?. Remember that I am talking about M383/M592 ECU. Anyway in a generic way the topic applies to any MAF related system. Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on January 05, 2015, 06:28:49 PM Sorry about all that comment. I will like to understand MAF Flow and Curve matching for proper ECU functionality, without maxing out MAF or ECU Load Limits. Thanks in advance for the advice.
Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: nyet on January 05, 2015, 08:39:02 PM PS_W is intake manifold absolute pressure, right?. Remember that I am talking about M383/M592 ECU. Anyway in a generic way the topic applies to any MAF related system. No, in ME7 ps_w is modeled manifold pressure. It does not apply in your case... but your topic didn't specify, and unless people say otherwise, I tend to assume they are asking ME7 questions. Apologies. Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on January 06, 2015, 07:53:18 AM No, in ME7 ps_w is modeled manifold pressure. It does not apply in your case... but your topic didn't specify, and unless people say otherwise, I tend to assume they are asking ME7 questions. Apologies. Don't worry your experience and help is really appreciated. Take a look. Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: Dropout on February 23, 2015, 11:44:28 AM Hi, interesting topic, I'm in the same boat so here is what I did . Since I'm using a VR6 maf housing , I copied MLHFM from a VR bin file, problem was that in the mid rpms (3800 - 4500) I was hitting max load at 1.2 bars of boost (t3 super 60 turbo). To cure this I scaled khfm down by 12% and now with load 12.6 I'm holding 1.4 bar of boost in those same rpms. Of course I use a wideband to monitor and adjust fuelling and before I scaled down khfm I pulled 5 degrees of timing above 7.00ms just to be on the safe side. After that I did a couple of pulls in 3-rd gear while logging and slowly upped the timing. It's interesting that in the low/mid loads there was no timing correction so I didn't have to touch them. With these corrections the car is running absolutely fine without any issues (it's my daily drive). Boost currently is 1.4bar 3700-5000, 5000-6500 1.5 bar and 6500-7000 1.4 bar (I've lowered the requested load after 6500). When I've time I would like to scale down a little more khfm so I have 1.5bar with load around 12.0 , this will give my more head room if later on I change to a better turbo.
P.S. I have tuned the car in steps, i.e. I first changed the injectors and got the mixtures correct , 2-nd step was changing the maf and finally when everything worked the way I liked it I started downscaling the load. Still have e lot to do ...but it's a hobby :) P.P.S my setup is Golf mk4 AGU, t3super60 turbo,380cc/min weber injectors, VR maf housing with stock MAF sensor, 255l walbro fuel pump. Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on February 23, 2015, 12:05:08 PM Hi, interesting topic, I'm in the same boat so here is what I did . Since I'm using the VR6 maf housing , I copied MLHFM from a VR bin file, problem was that in the mid rpms (3800 - 4500) I was hitting max load at 1.2 bars of boost (t3 super 60 turbo). To cure this I scaled khfm down by 12% and now with load 12.6 I'm holding 1.4 bar of boost in those same rpms. Of course I use a wideband to monitor and adjust fuelling and before I scaled down khfm I pulled 5 degrees of timing above 7.00ms just to be on the safe side. After that I did a couple of pulls in 3-rd gear while logging and slowly upped the timing. It's interesting that in the load/mid loads there was no timing correction so I didn't have to touch them. With these corrections the car is running absolutely fine without any issues up to now (it's my daily drive). Boost currently is 1.4bar 3700-5000, 5000-6500 1.5 bar and 6500-7000 1.4 bar (I' lowered the requested load after 6500). When I've time I'll like to scale down a little more khfm so a have 1.5bar with load around 12.0 , this will give my more head room if later on a change to a better turbo. P.S. I have tuned the car in steps, i.e. I first changed the injectors and got the mixtures correct , 2-nd step was changing the maf and finaally when everything worked the way I liked it I started downscaling the load. Still have e lot to do ...but it's a hobby :) P.P.S my setup is Golf mk4 AGU, t3super60 turbo,380cc/min weber injectors, VR maf housing with stock MAF sensor, 255l walbro fuel pump. I have done same procedure here. It works nicely. A question how are your load values at idle? did you compare it with your OEM idle load values? Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: Dropout on February 23, 2015, 12:11:12 PM If I recall correctly they are almost spot on but I'll check the logs and get back to you (have to find to OEM logs).
Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on February 23, 2015, 12:22:21 PM If I recall correctly they are almost spot on but I'll check the logs and get back to you (have to find to OEM logs). I ask because I notice that decceleration LOAD values could be around 0,55-0,45ms in my case @ 3280feet (1000mts) altitude and @ 82F (28C) temp. degrees. Then if you decrease too much KHFM you can get into too low LOAD values.Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: Dropout on February 24, 2015, 12:24:52 AM I don't think deceleration will be a big issue since on decel. your on "overrun" down to a given rpm. Checked the logs currently my idle load is ~ 0.90ms, deceleration load is ~0.50-0.55ms, this is with the current set up and load (KHFM) scaled down by %12 (will pull the stock loads from the laptop tonight) . BTW I also lowered the load threshold in the TLRAN tables, as I understand these are the closed loop lambda control threshold .
P.S. One thing that I've noticed is that g/s no longer mach the hp using the g/s / 0.8 formula, my g/s are a lot higher , do you have the same effect ? Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on February 24, 2015, 05:50:37 AM I don't think deceleration will be a big issue since on decel. your on "overrun" down to a given rpm. Checked the logs currently my idle load is ~ 0.90ms, deceleration load is ~0.50-0.55ms, this is with the current set up and load (KHFM) scaled down by %12 (will pull the stock loads from the laptop tonight) . BTW I also lowered the load threshold in the TLRAN tables, as I understand these are the closed loop lambda control threshold . P.S. One thing that I've noticed is that g/s no longer mach the hp using the g/s / 0.8 formula, my g/s are a lot higher , do you have the same effect ? I also have to tweak down TLRAN values for close loop control. Inclusive TLRAN at high RPMs depends a lot in turbo spool up behavior, needing to down it considerably. Mine is ball bearing and practically jumps from vacuum to almost full boost instantanealy. Ok anyway about MAF values, I also notice a little high gr/s values with VR6 MAF housing only. But due to some weird behavior I have notice sometimes at idle and around it (idle jumping / hunting, worse with AA sometimes - I also check for leaks.) I switch to complete VR6 OBD1 MAF to completely match MLHFM values. I have studied both curves ( VR6 MAF housing - linear scaled - and complete VR6 MAF) and I notice that it give us a little more resolution at high boost (high gr/s values) but it is not precise at all at low values (idle) for example. With complete VR6 MAF I have seen MAF values up to 223 gr/s @ 18psi max with GT28 turbo not totally tuned. I don't know if with complete MAF, g/s / 0.8 formula applies. Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: Dropout on February 24, 2015, 07:35:16 AM Interesting, I have rock stable idle, like oem. Whats your idle load ? Is the AFR correct? At one point I had a bit of hunting idle which was due to a lean mixture and the idle adaption hitting the limit, after enriching the mixture everything got back to normal . Also check the plastic tube going from the plenum to the brake booster, mine was cracked and was loosing pressure, took me a week to figure out why the car was throwing an error (checked all the other hoses and so on, even looked at this tube, but the cracks where on the bottom), finally found out the hard way when it broke off, good thing I was on an empty road .
P.S. have you changed the ignition timing at idle, it can also lead to hunting . Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on February 24, 2015, 08:08:05 AM Interesting, I have rock stable idle, like oem. Whats your idle load ? Is the AFR correct? At one point I had a bit of hunting idle which was due to a lean mixture and the idle adaption hitting the limit, after enriching the mixture everything got back to normal . Also check the plastic tube going from the plenum to the brake booster, mine was cracked and was loosing pressure, took me a week to figure out why the car was throwing an error (checked all the other hoses and so on, even looked at this tube, but the cracks where on the bottom), finally found out the hard way when it broke off, good thing I was on an empty road . P.S. have you changed the ignition timing at idle, it can also lead to hunting . Thanks a lot for your interested Dropout. Take a look --> http://nefariousmotorsports.com/forum/index.php?topic=7443.0 (http://nefariousmotorsports.com/forum/index.php?topic=7443.0). This jumpling/hunting idle occurs sometimes only, specially after DTCs clean or after ECU reflash. Normally AFRs at idle are from 14.8 to 14.2, sometimes can be from 15.2 to 13.9. . Generally idle is really stable. LOAD at idle and engine hot are around 0.9-0.95ms. Ignition timing at idle (maps) was not changed, it is OEM 12° at idle. Also trims are -0.8% / -0.8% all around. Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: Dropout on February 25, 2015, 05:43:10 AM I'll take a better look at the log tonight, but one thought, maybe the injector spray pattern its not correct which could cause this problem ? Have you tested with other injectors with a different spray pattern, maybe one close to the stock injectors ?
Title: Re: Fuel Trims via MAF curve dial or Injectors Factor?????? Post by: eliotroyano on February 25, 2015, 07:00:39 AM I'll take a better look at the log tonight, but one thought, maybe the injector spray pattern its not correct which could cause this problem ? Have you tested with other injectors with a different spray pattern, maybe one close to the stock injectors ? I am using Genesis 415cc injectors. |