MEFI adjustment ideas for rich idle on a Procharged motor?
08-15-2012, 10:03 PM
#31
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08-15-2012, 10:07 PM
#32
08-15-2012, 10:27 PM
#33
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That is some good info to start with. The first thing that comes to mind is your MTX-L needs to be recalibrated. Follow the instructions and make sure you pull the wide-band sensor OUT of the exhaust and free air calibrate the sensor. Don't get lazy and calibrate it installed as it can skew the calibration.
I'm running about 2.39 BPW on a 377 at 700 rpm with a 13.5ish AFR on a warm motor. Your 2.5 value should not be giving you an 11.0 AFR at idle on a big block. My initial suspicion is your wide band is out of calibration giving you bogus numbers. The fact that you make a small change and it leans out and dies leads me to believe your 11.0 AFR at idle may actually be 14.7 or higher. Mine starts idle rough and want to die when it gets above 15.0, and usually quits when it hits the 17.0 range.
I'll crunch through some of the numbers and have a back up plan if the MTX is indeed functioning properly. My other concern is the value difference between 4 cells in the idle region.
I'm running about 2.39 BPW on a 377 at 700 rpm with a 13.5ish AFR on a warm motor. Your 2.5 value should not be giving you an 11.0 AFR at idle on a big block. My initial suspicion is your wide band is out of calibration giving you bogus numbers. The fact that you make a small change and it leans out and dies leads me to believe your 11.0 AFR at idle may actually be 14.7 or higher. Mine starts idle rough and want to die when it gets above 15.0, and usually quits when it hits the 17.0 range.
I'll crunch through some of the numbers and have a back up plan if the MTX is indeed functioning properly. My other concern is the value difference between 4 cells in the idle region.
BTW I smell partially burned gas at idle
Last edited by yellowjacket; 08-15-2012 at 11:24 PM.
08-15-2012, 11:12 PM
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08-15-2012, 11:14 PM
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08-16-2012, 12:50 AM
#36
How lean does the MTX-L go when it dies?
I have the same wide-band system and I don't believe the soot will be a factor. I've had mine as rich as 10.8 at idle on baseline tuning and the wide band didn't give me one problem, motor wasn't happy but it did sound like a top fuel motor
Let's assume then the wide band system is calibrated correctly. I can't see how a 2.5 bpw will give you an 11.0 reading. We need to figure out this issue before things move forward.
The 35 kPa seems off to me. That's heavy vacuum from my experience. I would think it should be closer to 50ish.
Correct .xdf file in TunerPro?
Looking at your table values you have plenty of fidelity left to make small BPW changes and thus AFR changes. I have to drive a 42lb injector from 2.2 all the way to 4.0+ to get the AFR from 13.7 or so down to 10.8, therefore your min change should not go from 11.0 to lean stall. Does your IAC surge a lot?
I have the same wide-band system and I don't believe the soot will be a factor. I've had mine as rich as 10.8 at idle on baseline tuning and the wide band didn't give me one problem, motor wasn't happy but it did sound like a top fuel motor
Let's assume then the wide band system is calibrated correctly. I can't see how a 2.5 bpw will give you an 11.0 reading. We need to figure out this issue before things move forward.
The 35 kPa seems off to me. That's heavy vacuum from my experience. I would think it should be closer to 50ish.
Correct .xdf file in TunerPro?
Looking at your table values you have plenty of fidelity left to make small BPW changes and thus AFR changes. I have to drive a 42lb injector from 2.2 all the way to 4.0+ to get the AFR from 13.7 or so down to 10.8, therefore your min change should not go from 11.0 to lean stall. Does your IAC surge a lot?
Last edited by Trash; 08-16-2012 at 05:21 PM.
08-16-2012, 01:05 AM
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I would think 50kpa is a bit off, too. I run a decent cam in my motor, same elevation (650ftamsl) and I'm in the 70s at idle. Could there be a vacuum leak somewhere?
08-16-2012, 05:20 PM
#38
It just seems odd that a 2.5ish BPW is giving an 11:1 AFR on a 454. Regardless, don't you feel he has plenty of fidelity left on the BPW/MAP table to get the idle AFR dialed in? I think he does but something else is amiss.
08-16-2012, 07:19 PM
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I do, and as mentioned above, there may need to be some adjustments made to the surrounding cells.
Yellowjacket - would you be willing to email your bin file? I'd like to have a look at it for grins.
Yellowjacket - would you be willing to email your bin file? I'd like to have a look at it for grins.
08-16-2012, 07:52 PM
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table resolution
A little data to move your discovery
BPW - RPM vs MAP
0 - 15
This is a stock 454 Mag on the MEFI2
RUN FUEL vs MAP and RPM
RPM MAP
30 40 50 60 70 80 90 100
5200 3.66 3.54 4.94 6.04 7.87 8.73 10.62 10.19
4800 3.66 3.54 4.70 6.41 7.69 8.91 9.70 11.47
4400 3.60 3.91 5.00 6.53 7.81 9.16 10.19 11.72
4000 3.54 4.21 5.37 6.59 8.00 9.22 10.68 12.21
3600 3.48 4.39 5.62 6.71 8.18 9.52 10.62 12.82
3200 3.42 4.70 5.92 6.90 8.12 9.40 10.50 12.39
2800 3.36 4.52 5.80 7.08 8.24 9.28 10.31 12.02
2400 3.30 4.03 5.13 6.41 7.45 8.73 10.01 11.41
2000 3.23 4.27 5.49 6.59 7.63 8.73 9.95 11.11
1600 3.17 4.09 5.31 6.16 7.32 8.48 9.70 11.11
1200 3.11 4.09 5.25 6.29 7.51 8.61 9.64 11.23
1000 2.99 3.85 4.94 6.10 7.20 8.18 9.40 10.99
800 2.81 3.72 4.82 5.86 6.90 8.00 9.28 10.74
600 2.56 3.54 4.33 5.37 6.23 7.63 8.79 10.50
BPW - RPM vs MAP
0 - 15
This is a stock 454 Mag on the MEFI2
RUN FUEL vs MAP and RPM
RPM MAP
30 40 50 60 70 80 90 100
5200 3.66 3.54 4.94 6.04 7.87 8.73 10.62 10.19
4800 3.66 3.54 4.70 6.41 7.69 8.91 9.70 11.47
4400 3.60 3.91 5.00 6.53 7.81 9.16 10.19 11.72
4000 3.54 4.21 5.37 6.59 8.00 9.22 10.68 12.21
3600 3.48 4.39 5.62 6.71 8.18 9.52 10.62 12.82
3200 3.42 4.70 5.92 6.90 8.12 9.40 10.50 12.39
2800 3.36 4.52 5.80 7.08 8.24 9.28 10.31 12.02
2400 3.30 4.03 5.13 6.41 7.45 8.73 10.01 11.41
2000 3.23 4.27 5.49 6.59 7.63 8.73 9.95 11.11
1600 3.17 4.09 5.31 6.16 7.32 8.48 9.70 11.11
1200 3.11 4.09 5.25 6.29 7.51 8.61 9.64 11.23
1000 2.99 3.85 4.94 6.10 7.20 8.18 9.40 10.99
800 2.81 3.72 4.82 5.86 6.90 8.00 9.28 10.74
600 2.56 3.54 4.33 5.37 6.23 7.63 8.79 10.50
Last edited by tunertech; 08-16-2012 at 07:57 PM.
