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SVTPerformance's Chain of Restaurants
Tuning À la carte
Is Your Car Tuned Correctly?
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<blockquote data-quote="MichaelFreedman" data-source="post: 12506752" data-attributes="member: 39467"><p>Just going to address tuning the MAF curve on the dyno. Can it be done... yes, but it is tedious and prone to errors. You have to turn off all adaptive controls in the PCM, set the Desired A/F for ALL load conditions to be the same, and disable all A/F modifiers and preferably lock the timing and disable spark modifiers as well. Then you can datalog MAF voltage and plot against wide band O2 and adjust the MAF table to achieve programmed A/F ratio. Once that is done, re-enable adaptive controls and verify that in closed loop you run at 14.7:1 A/F with little if any short or long term fuel corrections. If you have ANY substantial fuel corrections, you may get the tune right on the dyno, but driveability will suck. </p><p></p><p>For this reason, it is FAR better to have a meter that is calibrated on a flow bench. You're MAF tells the computer how much air that is going into the motor. This is used more importantly to calculate load. You may be able to get 11.5:1 a/f by putting 10.5 in the table thus bandaiding a bad MAF curve. Makes for nice dyno charts. But what you don't see is that the MAF is also used to calculate load. Load is then used to select where in the timing map you are. A/F may look great, but if your computer thinks there is less air, you can end up in a lower load cell and detonate. NOT because you are lean, but because there is too much timing due to an incorrect MAF calibration.</p><p></p><p>Mike</p></blockquote><p></p>
[QUOTE="MichaelFreedman, post: 12506752, member: 39467"] Just going to address tuning the MAF curve on the dyno. Can it be done... yes, but it is tedious and prone to errors. You have to turn off all adaptive controls in the PCM, set the Desired A/F for ALL load conditions to be the same, and disable all A/F modifiers and preferably lock the timing and disable spark modifiers as well. Then you can datalog MAF voltage and plot against wide band O2 and adjust the MAF table to achieve programmed A/F ratio. Once that is done, re-enable adaptive controls and verify that in closed loop you run at 14.7:1 A/F with little if any short or long term fuel corrections. If you have ANY substantial fuel corrections, you may get the tune right on the dyno, but driveability will suck. For this reason, it is FAR better to have a meter that is calibrated on a flow bench. You're MAF tells the computer how much air that is going into the motor. This is used more importantly to calculate load. You may be able to get 11.5:1 a/f by putting 10.5 in the table thus bandaiding a bad MAF curve. Makes for nice dyno charts. But what you don't see is that the MAF is also used to calculate load. Load is then used to select where in the timing map you are. A/F may look great, but if your computer thinks there is less air, you can end up in a lower load cell and detonate. NOT because you are lean, but because there is too much timing due to an incorrect MAF calibration. Mike [/QUOTE]
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Tuning À la carte
Is Your Car Tuned Correctly?
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