MAF tuning advanced discussion
04-26-2005, 09:56 PM
#1
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MAF tuning advanced discussion 1. OK, so I went ahead an dialed in my VE table, pretty close to 13:1 across the board.
2. I then turn back on afr, closed loop, and PE
3. I then set the MAF Fail to 0 in order to do some MAF tuning, so I logged the Dynamic Airflow and the MAF Frequency.
4. I then used the MAF Spreadsheet on here REDSUPRA's (modified by Black02SS) to dial in my new MAF table according to the log I made. I double checked some of the values by manual calculation and it seems to work pretty good...
5. OK so Now I go for a long drive and I am getting really poor results from under 2000rpm. So after a little more driving I turn 'ON' LTFT Learn.
Did about 20 mins more driving and logged the following:
Link To HP Tuners LOG
How in the hell can my LTFT be so NEGATIVE and yet my AFR in the same cells be so LEAN????????????
Any of you guys think you know what I should try? It seems that the car runs so lean down low but if that is the case then why isnt it reporting positive fuel trims?
Motor is a 408, 238/242 .608, 90/90 setup, and yes I have MAF Ends
2. I then turn back on afr, closed loop, and PE
3. I then set the MAF Fail to 0 in order to do some MAF tuning, so I logged the Dynamic Airflow and the MAF Frequency.
4. I then used the MAF Spreadsheet on here REDSUPRA's (modified by Black02SS) to dial in my new MAF table according to the log I made. I double checked some of the values by manual calculation and it seems to work pretty good...
5. OK so Now I go for a long drive and I am getting really poor results from under 2000rpm. So after a little more driving I turn 'ON' LTFT Learn.
Did about 20 mins more driving and logged the following:
Link To HP Tuners LOG
How in the hell can my LTFT be so NEGATIVE and yet my AFR in the same cells be so LEAN????????????
Any of you guys think you know what I should try? It seems that the car runs so lean down low but if that is the case then why isnt it reporting positive fuel trims?
Motor is a 408, 238/242 .608, 90/90 setup, and yes I have MAF Ends
04-27-2005, 12:38 PM
#3
What MAF do you have? I have a couple year old SLP and I'm going to put my stocker back on because I've noticed that my LTRIMs are really far negative too. I want to see if a bad MAF is the issue. I just cleaned the wires to see if dirt could be causing the issue. I haven't had a chance to relog yet to see if that made a difference.
In any case, I would like to know what other suggestions are out there since I may be in the same boat too.
In any case, I would like to know what other suggestions are out there since I may be in the same boat too.
04-27-2005, 12:42 PM
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Do you STFTs jump around alot or are they stabilizing. Something I've noticed is that at least on my buddy's car, his STFTs are always hopping around at low rpms and low TPS. I think it's one of a few things, cam overlap distorting fueling, O2s on the way out, his dumped exhaust, etc. Another thing to think about is that cam overlap can also confuse a wideband just as easily as a narrowband, so what you may think is perfect in open loop mode, very well may not be... 
04-27-2005, 02:45 PM
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Originally Posted by txhorns281
Do you STFTs jump around alot or are they stabilizing. Something I've noticed is that at least on my buddy's car, his STFTs are always hopping around at low rpms and low TPS. I think it's one of a few things, cam overlap distorting fueling, O2s on the way out, his dumped exhaust, etc. Another thing to think about is that cam overlap can also confuse a wideband just as easily as a narrowband, so what you may think is perfect in open loop mode, very well may not be...
04-27-2005, 02:54 PM
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Originally Posted by Ragtop 99
What MAF do you have? I have a couple year old SLP and I'm going to put my stocker back on because I've noticed that my LTRIMs are really far negative too. I want to see if a bad MAF is the issue. I just cleaned the wires to see if dirt could be causing the issue. I haven't had a chance to relog yet to see if that made a difference.
In any case, I would like to know what other suggestions are out there since I may be in the same boat too.
In any case, I would like to know what other suggestions are out there since I may be in the same boat too.
Thunder MAF Ends
04-27-2005, 02:55 PM
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Originally Posted by Dustin Butts
How in the world do you get a large cam tuned in then? I mean if you can't trust your O2 sensor readings?
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04-27-2005, 02:56 PM
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Originally Posted by txhorns281
Do you STFTs jump around alot or are they stabilizing. Something I've noticed is that at least on my buddy's car, his STFTs are always hopping around at low rpms and low TPS. I think it's one of a few things, cam overlap distorting fueling, O2s on the way out, his dumped exhaust, etc. Another thing to think about is that cam overlap can also confuse a wideband just as easily as a narrowband, so what you may think is perfect in open loop mode, very well may not be...
04-27-2005, 03:04 PM
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Originally Posted by hc_performance
I think that you have to use a Co2 analyzer like the ones they use to check your emissions. Maybe someone else who knows a little more about this can elaborate on this.
04-27-2005, 03:52 PM
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That's the trick fellows.... finding a way to compensate for false O2 readings... wideband or narrow. why do you think that all these big cam people have trouble getting their part throttle fueling in line?
CO analyzer could be used, but i dunno how to correlate that data to scanner data, or you could do an open loop tune and guesstimate values according to the shape of your VE table where the wideband is distorted
CO analyzer could be used, but i dunno how to correlate that data to scanner data, or you could do an open loop tune and guesstimate values according to the shape of your VE table where the wideband is distorted
04-27-2005, 03:54 PM
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Originally Posted by SSnakekiller
Well doesnt it usually mean that whatever reading you are getting on the wideband could be leaner than the car is really running due to air leaking through from the overlap? The LSA is 115 btw.
Last edited by txhorns281; 04-27-2005 at 04:00 PM.
04-27-2005, 03:55 PM
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Originally Posted by Dustin Butts
How in the world do you get a large cam tuned in then? I mean if you can't trust your O2 sensor readings?
you don't need a donkey-dick cam to make good power... 
04-27-2005, 04:12 PM
#13
115 LSA reduces your overlap, but you still have 10* of overlap at .05
Your big cubes absorb some of it, but you have way more overlap than GM is using in the LS7 cam to give you a point of reference.
So how is the car driving? If it drives smoothly and mpg isn't too far from expected, that is the ultimate test.
Your big cubes absorb some of it, but you have way more overlap than GM is using in the LS7 cam to give you a point of reference.
So how is the car driving? If it drives smoothly and mpg isn't too far from expected, that is the ultimate test.
04-27-2005, 06:42 PM
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Originally Posted by Ragtop 99
115 LSA reduces your overlap, but you still have 10* of overlap at .05
Your big cubes absorb some of it, but you have way more overlap than GM is using in the LS7 cam to give you a point of reference.
So how is the car driving? If it drives smoothly and mpg isn't too far from expected, that is the ultimate test.
Your big cubes absorb some of it, but you have way more overlap than GM is using in the LS7 cam to give you a point of reference.
So how is the car driving? If it drives smoothly and mpg isn't too far from expected, that is the ultimate test.
If I scaled the VE table then wouldnt the maf and 02's just be off? And I cant scale the MAF table for RPM so
04-27-2005, 06:48 PM
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Originally Posted by txhorns281
Go with a not so large cam... you don't need a donkey-dick cam to make good power...
you don't need a donkey-dick cam to make good power... As ragtop said, the cubes do absorb a lot. I could easily put a bigger cam in and still be comfortable, but I love it the way it is. Just need to figure out this low end AFR!!!
