Speed Density or Maf Tune ?
10-11-2014, 10:19 PM
#24
Yes and no. The MAF is very accurate at metering true air density so it's great for compensating for atmospheric changes. But, if you tune your VE table to be very accurate in SD with a wideband, it's still going to be very close when the weather changes or you climb a mountain since the ambient baro pressure changes which is picked up by the MAP and the IAT sensor compensates for temp fluctuations. Many, me included, feel that the SD tune is more responsive and losing the MAF as a restriction is always a win, no matter how small. It's also the only way I know of to force a lean cruise.
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10-12-2014, 05:47 PM
#30
Here is a data log of LC kicking in on my 04 Silverado. It activates around frame 216 and disengages around frame 2130. Note the commanded a/f and the o2 sensor voltages while it is active. I used the LC table settings from a Holden calibration. I tried it on the truck for several months and never saw a noticeable increase in mpg. I finally took it off thinking it might be hurting the cats running it that lean. I'm just posting this to show that it can be enabled easily with what I use.
10-17-2014, 01:07 PM
#32
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ok so i went back to a MAF tune car started and idle just a little surging between 1000-1200 rpm. Also ran a scan until 220f+. My question now is with the cells that where hit in the scan, do i copy them and put them in the cells of the tune i installed. For example if it particular cell read 27* in the scan and in the tune that exact cell is set at 30* do i change it to 27* ?
thanks to all who have responded in the past
thanks to all who have responded in the past
10-17-2014, 10:37 PM
#34
OLSD is pretty easy to enable. You go to Fuel > Open & Closed Loop > Closed Loop Enable and set everything to 284 or 285 depending on your OS. This forces OLSD. Here is a good write-up from HPT on the entire process: http://www.hptuners.com/help/vcm_edi...to_user_sd.htm
As for what to do with your scanner results, select the values you want, paste special-multiply by % into the tune file. It makes the changes automagically.
I'd set to OLSD, disable all fuel adders outside of VE, and drive it and log. Get the cell counts over 30 minimum but 50 would be better. Once you get the VE table dialed in, go ahead and tune the MAF. Or, if you want, turn CLSD back on. Between the O2s, IAT, and MAP, you'll be fine without the MAF. You just have to tune the O2s to be less sensitive to overlap. In fact, the best bet is to run OLSD at idle and CLSD for lean cruise. Then use PE to command the proper A/F ratio under load.
Here is how you setup OL idle and CL cruise:
1. set PE to 1.0 up till 1200RPM
2. set TPS enable PE to 0 up till 1200RPM
3. set open loop F/A to 1.0 up till idle MAP, so if idle at 60kPa, 0-60kPa from say, 20*C up
4. disable LTFTs (it sucks... a lot) (not necessary for this, but LTFT truly do suck)
5. set PE MAP enable to 15kpa
6. set PE enable delay RPM to 0
7. disable the P0131 and P0151 DTC codes
8. disable STFT open loop enable (if its not already)
9. return to the Closed Loop enable table and set the temps back to stock
But that means you need to tune the Open Loop EQ Table for when you're out of PE at idle. Commanding and EQ Ratio of 1.00 for all kPa values below whatever your cam idles at is a good bet. The map for a 2004 GMC Sierra is a very good map for this as it keeps most at 0 or right around 0 and in the colder temps, commands more fuel.
As for what to do with your scanner results, select the values you want, paste special-multiply by % into the tune file. It makes the changes automagically.
I'd set to OLSD, disable all fuel adders outside of VE, and drive it and log. Get the cell counts over 30 minimum but 50 would be better. Once you get the VE table dialed in, go ahead and tune the MAF. Or, if you want, turn CLSD back on. Between the O2s, IAT, and MAP, you'll be fine without the MAF. You just have to tune the O2s to be less sensitive to overlap. In fact, the best bet is to run OLSD at idle and CLSD for lean cruise. Then use PE to command the proper A/F ratio under load.
Here is how you setup OL idle and CL cruise:
1. set PE to 1.0 up till 1200RPM
2. set TPS enable PE to 0 up till 1200RPM
3. set open loop F/A to 1.0 up till idle MAP, so if idle at 60kPa, 0-60kPa from say, 20*C up
4. disable LTFTs (it sucks... a lot) (not necessary for this, but LTFT truly do suck)
5. set PE MAP enable to 15kpa
6. set PE enable delay RPM to 0
7. disable the P0131 and P0151 DTC codes
8. disable STFT open loop enable (if its not already)
9. return to the Closed Loop enable table and set the temps back to stock
But that means you need to tune the Open Loop EQ Table for when you're out of PE at idle. Commanding and EQ Ratio of 1.00 for all kPa values below whatever your cam idles at is a good bet. The map for a 2004 GMC Sierra is a very good map for this as it keeps most at 0 or right around 0 and in the colder temps, commands more fuel.
Last edited by JakeFusion; 10-18-2014 at 08:35 PM.