Need to finally solve the .3 difference
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From: Port Tobacco, MD
Need to finally solve the .3 difference We have been fighting the calibration between the LM1 and HPT software for almost 2 years. The LM1 shows .3 tenths lower than what HPT software will record and from the logs I'd be willing to believe the LM1. On standard tunes with the O2s hooked up and the computer commanding stoich the LM1 reads 14.7-14.8 while the HPT shows 15.0-15.1. Is there anything we can do to correct this condition??? We just were at the track and we thought the A/F was 12.2:1 and going back and looking at the LM1 logs the A/F was ~11.9:1. Not a big difference but when you need to be @ 13.2:1 and the A/F is 11.9.... 
Phil
Phil
Make your own calculated PID for the wideband. When I calibrate a wideband, I make a new calculated pid to ensure it is exact and both match. You will need to set the output on the LM1 to a constant and record the values. Do this for a few points, .5, 2.5, 4.5v and then see what the LM1 reads. If you set it to only display .5 and you see .490 then that can have an effect on the outcome of the calculation. Same goes for 2.5 and 4.5 If they are set to those values and you see them in HPT/EFILive as something different, then you need to compensate for the voltage difference.
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From: Port Tobacco, MD
I think I need to create a custom pid like Black02ss stated and leave the LM1 the way it sits. I guess the only way to make it work is to shift the A/F output .3.... Volts / .5 + 9.7 to remove for the EIO reading .3 too high?
Phil
Phil
Last edited by Phil99vette; Mar 25, 2006 at 10:39 AM.
Even though it is a global difference, you need to really check the voltage of what the LM1 is outputting through HPT. You can't just take the .3 and take it off as it isn't always correct. I did that a long time ago and found out it wasn't right. You need to see what you are getting in HPT for the FLATLINE values you program in Logworks.
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From: Port Tobacco, MD
Ok....here's an update...
Test 1: Drive with O2s and MAF enabled cruising where a/f should be 14.7x stoich
Results:
Wideband screen/logworks displays 14.7+-.07
HP Tuners shows 15.0-15.1
I think wideband with logworks are known to be correct. Fresh sensor and fresh calibration
Test 2: LM1 voltage vs A/F
started car up and averaged A/F and voltage and found 3.10 volts out to HPT = 14.2 A/F on LM1
So....
0.00 = 11.5
5.00 = 16.0
Test 1: Drive with O2s and MAF enabled cruising where a/f should be 14.7x stoich
Results:
Wideband screen/logworks displays 14.7+-.07
HP Tuners shows 15.0-15.1
I think wideband with logworks are known to be correct. Fresh sensor and fresh calibration
Test 2: LM1 voltage vs A/F
started car up and averaged A/F and voltage and found 3.10 volts out to HPT = 14.2 A/F on LM1
So....
0.00 = 11.5
5.00 = 16.0
Phil, if you go into VCM Control in HPT and command several different AFRs and compare the voltages with log works and then you can come up with a calibrated pid just like Black02SS said. I works great. I am using a LC1 and I calibrated it with Logworks and now my EFILive and Logworks reads the same.
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I've suggested before that you look at ground current,
ground voltage offsets between the WB and the EIO
cable. There is substantial current thrown by the LM-1
heater drive and it is also variable - leading perhaps to
a situation where there is no single offset that fits all
corners of operation, but rather an offset that varies
with exhaust gas / "natural" O2 sensor temp (and the
heater loop's required average current, there).
As an experiment it might be interesting to cut the WB
output lines and insert a series 100-ohm resistor in both
the signal and return (ground) legs; then you could put
a DMM across each resistor and see what kind of voltage
drop, indicating whether current loops / ground loops are
the cause as I suspect.
Another thing to do is, simply put a 1.5V battery to the
EIO cable input independent of the vehicle electrically;
take DMM and logged EIO voltage values and judge the
input A/D accuracy. This tells you whether there's any
intrinsic error to the EIO voltage measurement absent
any offsets coming from the larger picture.
With the two pieces not connected you could put the
DMM from EIO jack shield, to LM-1 jack shield and take
a voltage offset reading with the LM-1 lit up and heater
current running.
Be interesting to see just how much, and how variable
any such offset is.
ground voltage offsets between the WB and the EIO
cable. There is substantial current thrown by the LM-1
heater drive and it is also variable - leading perhaps to
a situation where there is no single offset that fits all
corners of operation, but rather an offset that varies
with exhaust gas / "natural" O2 sensor temp (and the
heater loop's required average current, there).
As an experiment it might be interesting to cut the WB
output lines and insert a series 100-ohm resistor in both
the signal and return (ground) legs; then you could put
a DMM across each resistor and see what kind of voltage
drop, indicating whether current loops / ground loops are
the cause as I suspect.
Another thing to do is, simply put a 1.5V battery to the
EIO cable input independent of the vehicle electrically;
take DMM and logged EIO voltage values and judge the
input A/D accuracy. This tells you whether there's any
intrinsic error to the EIO voltage measurement absent
any offsets coming from the larger picture.
With the two pieces not connected you could put the
DMM from EIO jack shield, to LM-1 jack shield and take
a voltage offset reading with the LM-1 lit up and heater
current running.
Be interesting to see just how much, and how variable
any such offset is.
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