NOTE: TOO LITTLE OR TOO MUCH IGNITION ADVANCE CAN DAMAGE YOUR ENGINE. USE CAUTION WHEN SETTING YOUR ADVANCE CURVE. Once the fuel curve is determined, optimum ignition timing can be determined. Start the engine and let it warm up. Run the engine up to an RPM that is a breakpoint and note the MAP. With the engine under load, use key 3 in the Engine Monitor screen to increase or decrease the timing. Find the best timing by holding a steady RPM and load while increasing timing (key 3) until you hear a slight detonation. Back that advance angle down one degree and write down the RPM, MAP and Advance Angle. Repeat this for as many RPM and MAP combinations as you can. An alternate method to listening for the knock limit is to tune for peak torque. This is done on a dynamometer by trial and error to find the best advance which produces the highest torque for that RPM and MAP combination. Other methods include lowest NOx point or optimum EGT.When as many of the 64 cells are done, transfer your data permanently to the Advance Table by going into the Edit Menu and selecting Advance Table. Move around the advance table with the arrow key and type over the old advance angle values with your new ones. If you could not test all the RPM and MAP break points, split the difference between two of the nearest points so that a smooth line is made. Extrapo- lating in a straight line is OK for points beyond tested RPM and MAP break points. Escape out of the Advance Table and save and download your new calibration. 1. Observe the idle mixture Using IOT and TOG, get the engine to settle into an acceptable range. You may also need to experi- ment with the timing by adding or subtracting a couple of degrees. It may also be necessary to readjust the throttle stop so as to have an adequate amount of air flowing. If you are using a MAP sensor try to get the engine to idle with the lowest kpa value possible, this also depends a great deal on cam overlap, so it may not be as low as anticipated. Once an acceptable idle has been achieved by making TOG, IOT and timing changes, record the closed throttle voltage, the injector pulsewidth and the idle kpa as well as TOG and IOT needed to do this. Next review the values recorded and verify that they conform to the parameters dis- cussed earlier. Now change the name of your *.bin file in the edit page of your software and make the changes required for best idle. NOTE: Remember to save the file changes and download the new file to the TEC.TIP: While in the Monitor Screen, you can turn off the EGO sensor adjustment by typing 'C', this allows you to make adjustments to IOT and TOG without having the Oxygen Sensor feedback interfere. Setting the throttle plates One of the most overlooked areas in tuning in a stable idle is the base throttle plate settings, or minimum air rate. The function of the idle air control (IAC) motor is to compensate for cold start and other loads such as the A/C kicking in and out, or the transmission being put into and out of gear. The idle air control motor is not, however, supposed to be maintaining the base idle speed when hot. When the engine is fully warmed up and not under any load the idle should be about 25 to 50 RPM above the desired hot idle speed, assuring that the IAC is inactive. In order to adjust these idle speed settings follow this outline: 1. Fully warm up the engine. 2. Disable the Idle Air Control motor and block the bypass-air passages. 3. Set the idle to approximately 25 RPM above the desired idle speed as outlined in the calibration. 4. Re-enable the IAC and verify that the engine RPM is still where you set it. Load Test the engine and verify adequate fuel delivery If equipped with data-logging software, it will be possible to log some light acceleration or load condi- tions to verify adequate fueling. If data logging is not available, a little creativity will be necessary, it is not recommended to monitor the engine functions with a lap top while driving the vehicle. If tests are being made in a driving condition, someone other than the driver should be making the adjustments. Should the engine be too rich under load at the upper end of the RPM range, verify that the acceleration enrich- ments have timed out and decrease TOG to make the engine lean out. Should the engine be too lean under the same conditions, increase TOG only if the 'before you start the engine' calculations show that an increase in pulsewidth is still possible, otherwise you will need to increase fuel pressure or injector size(s). 6. Set your VE's The Volumetric Efficiency Table allows for correcting fuel flow in the mid range. TOG should only be used to correct the fuel flow at the RPM limit, the VE table will allow an increase in pulsewidth at RPM's below the limit, for example if the engine is lean at 5,200 RPM, but it is rich at the RPM limit of 7,200, then it is recommended that the TOG be lowered and adjusted for 7,200 RPM and an increase in pulsewidth be effected by entering a positive value in the VE table at that specific load and RPM. Each specific engine RPM has its own pulsewidth limit, so it is important not to exceed that limit. For example doing the math for 7,200 RPM determines the maximum pulsewidth is 7.333 milliseconds and if this is TOG, and the engine is lean at 6,000 RPM where the maximum pulsewidth is 9.000 ms, then the maximum value that can be added to the VE table at 6,000 RPM is 0.227. Knock Threshold "A" With the engine warmed up, observe the Knock reading on the Engine monitor screen. It should be low, below 30. Put the engine in gear and load it by either driving it or running it on a dynamometer. As the engine goes faster the number may go up, even with no knock. With a light load, try increasing the spark timing. Use "key 3" on the engine monitor screen. With a sharp ear you should hear the characteristic sound of detonation with 5 to 10 additional degrees advance. Note that as the detonation comes on the knock number should go up. Using a moderate RPM and load, note the number at which you just begin hearing knock. Take this number and transfer it into permanent memory by going back into the Edit menu, selecting Change Knock parameters and changing the Knock Threshold to this number. Exit, save and download your new calibration into the TEC. Repeat the same RPM and load and verify that the KNOCK symbol appeared just at the onset of knock. The Knock may be slightly audible but that may be OK. As the knock is occurring, the spark timing should be dropping. If the spark timing drops a great amount and the knock does not subside, then the spark curve is set too high at that RPM - MAP point. Try using key 3 on the engine monitor screen to reduce the timing. Note how far you had to reduce it for the knock to go away. Go back to the edit menu and change the Advance curve. To further assist in making the engine knock, try using the lowest octane gas available or disconnect the EGR valve. Short bursts of power braking against an automatic transmission may also stimulate knock. Rate at Which Advance is Retarded When knock is detected the TEC begins retarding the timing once per tach event until the knock subsides. The rate at which it reduces the timing should be set between .25o and 1.0o per engine function. Setting this too high will cause poor engine response because the engine will be running too retarded at the slightest detection of knock. Maximum Retard Allowed The knock control must have a limit to the number of engine degrees that it can pull out. Too much will make the engine run sluggish. Too little will cause excessive knock to come through when you use very low octane gas. Set this value between 10 and 15 degrees. Rate at Which Advance is Increased When the engine is recovering from a period of detonation the TEC begins advancing the timing back to what is programmed in the Advance table. This rate should be set slow to keep the engine from oscillat- ing. Set it to only .25o per engine function. RPM Above Which Knock Control is Inhibited The Knock function does have difficultly separating engine noise and detonation noise at high RPM's. Therefore, it is necessary to disable the knock function at high RPM's so that the Knock circuit won't pick up stray crankshaft or valve train noises. This is especially true in race cars with solid lifters. Typically, the Knock sensor won't work above 5,000 RPM. This limitation makes knock control for high speed race engines virtually useless. At high RPM, generally, the circuit goes dead and knock could be present without any ability to retard the timing automatically. It is recommended to set the limit to 4,500 RPM and make sure the spark advance curve over 4,500 RPM is not overly aggressive.