Post by Stinger on Jul 10, 2010 0:09:45 GMT -5
This should be viewed as an article to get the basics of how to tune your Megasquirt equipped car.
The preferred tuning software is TunerStudio (www.efianalytics.com/TunerStudio/beta/).
Datalog viewing software is Megalogviewer www.ideasandsolutions.biz/MegaLogViewer/download/
The first step of course is to get the engine to start, then to stay running. Once you do the basics like calibrate the TPS in the tuning software, ensure that the timing commanded matches actual timing, and ensure that the sensors appear to be reading correctly on your laptop screen, you're ready to start tuning.
Idle Air/Fuel Ratio Tuning
First the idle fuel cells will almost always need manual tuning. You need to physically see the area's it "floats" in, and make sure their are no drastic table changes. Generally the four primary cells it uses for idle should all have the same VE value. Generally in a stall, as speed drops, load also goes up. Make sure no odd transitions happen in the fuel table there. If it takes a 50% VE to idle at 900 rpm, it probably isn't going to want 20% at 600.
Once the engine is relatively warm (over 160 degrees), you can start tuning the Fuel VE table to dial in the idle air/fuel ratio (AFR). Lower numbers reduces fuel, higher increase fuel. With a relatively tame cam (stock or stage 1) you can expect the wideband reading to be accurate at idle and can therefore modify the cells the engine is idling at until the idle AFR is 14.7:1 or so. You can click-drag to highlight multiple cells in the table and then use the = button on the top right of the table to set the highlighted cells to a particular number value. Typically a change of 3-5 will change the afr by a full point (from 13:1 to 14:1 for instance). I typically select 6-8 cells around where it is currently idling and change them all at once to the same value because once you change the number the idle speed and vacuum will increase/decrease which will move where in the VE table it is currently running. Selecting a number of cells will ensure it stays within the cells you are changing throughout the process.
Idle Air/Fuel Ratio Tuning With Large Cam-Turbo
For those running large cams with lots of overlap (stage 2, stage 3), your idle afr readings won't be accurate because unburnt oxygen is going out the exhaust and skewing the afr value. Readings above 1500 rpm or so will be accurate. In this case, you can use a couple different methods to find the ideal afr target for idle. One is to change the surrounding 6-8 cells and watch the tach. The idle speed should be highest where the AFR is at least within range. Once you get it close, you can stand where the exhaust exits and see how rich it smells. If you can smell a lot of unburnt fuel exiting the exhaust, lower the idle ve numbers to pull some fuel away from the engine at idle. Turbo engines with large cams will typically run best with an indicated idle AFR of 12.5:1-13.5:1.
Idle Air/Fuel Ratio Tuning With Large Cam-Naturally Aspirated
For those running large cams with lots of overlap (typically duration over 225 or so), your idle afr readings won't be accurate because unburnt oxygen is going out the exhaust and skewing the afr value to show lean. Readings above 1500 rpm or so will be accurate. In this case, you can use a couple different methods to find the ideal afr target for idle. One is to change the surrounding 6-8 cells and watch the tach. The idle speed should be highest where the AFR is at least within range. Once you get it close, you can stand where the exhaust exits and see how rich it smells. If you can smell a lot of unburnt fuel exiting the exhaust, lower the idle ve numbers to pull some fuel away from the engine at idle. Typically n/a engines with a large cam will run best with an indicated idle AFR of 16:1-17:1.
Manually Adjusting VE Table For First Drive
Once idle afr is set, you can look at the VE table and see how the numbers surrounding the idle area match the numbers you just set for idle. If it is idling properly with a value 40 for instance and the numbers just to the right or above the idle area is 35 or 55, they need to be modified before you can expect it to drive properly above idle. This is because an increase in rpm (moving right in the table) or a decrease in vacuum/increase in boost (moving up in the table) will require more fuel than the cells below/left of them. This means the general trend will be for the cell numbers to get larger as they go up and to the right so the largest number will be near the top right corner and the smallest will be bottom left.
Once the engine exceeds peak hp rpm, the fuel demands will drop back down a bit as rpm increases. What you can learn from this (besides getting the base table setup safe) is that if you make a low boost pull and find the "ideal" numbers to be around 115 and then notice that the numbers in the next higher boost range are in the 110 range, it's going to run lean when it reaches that cell. Use your brain and realize if it needs 115 at 10psi, it's going to need more than 115 at 15psi. Same theory for rpm increases. If it's safe at 115 at 4500 rpm and the number you didn't reach in the previous pull (so yet untuned) is only 110 at 5000 rpm, raise it to 115 or 118 or something before making the next pull. This will prevent it from going dangerously lean.
If there are any rpms under boost where the tune is way lean, fix it manually rather than driving through it and letting auto tune take care of it. That's a good way to blow a headgasket or worse before you ever get it tuned.
You'll also be much better off from a knowledge standpoint to do some tuning manually before starting auto tuning. Reason being, you'll learn a ton about what your engine wants/needs by doing it manually and this will help tremendously in the future. Just letting auto tune do all of the work is like letting a mechanic do all the work on your car. It may work fine but you won't learn a damn thing and won't be able to diagnose or fix any issues in the future, nor will you be able to use all of the features of the MS2 system and software.
Using VE Live Tuning While Driving-No Boost
You'll want to get the car to idle well, then to be driveable before you start to auto tune using the VE Live tuning tab. At that point, the easy or normal change settings will depend on the length of the drive and how far off the tune is. Initially you'll probably want it on easy so it can change the tune with ease. Drive around cruising without boost and let it dial in the cruising tune until the afr is where it should be (around 14.7:1 under non-boosted conditions), be sure to run through different rpm ranges with different throttle positions (light throttle to 5000 or something, wide open to 2500 then let off, cruising around normally down side streets slowly, highway driving at higher speeds, etc. You want to cover every possible "out of boost" scenario, then start doing a little boost at low rpm and see how close the afr is.
Using VE Live Tuning While Driving-Boost
When driving with low boost, if it's crazy lean (more than 14:1 or so at low boost), manually add some fuel to that area of the map before continuing. The best bet is to give it more fuel than it should need under boost and let auto tune lean it out, not start lean and let it richen it up. Lean kills engines, rich doesn't. By all means do not just floor it and expect the VE Live "auto tune" to fix the afr numbers before it goes lean and blows a headgasket or melts a piston because it won't. You have to manually get it safe (rich) and then let it lean it back out. Your AFR target under boost should be 12.0:1 or so, no leaner than 12.5 and no richer than 11.5.
Sample Fuel VE Table:
Example of How Using an Auto Tune Function Exclusively Can Cause Problems
Here is an example of why you shouldn't just expect any form of "auto tune" to just make everything perfect without your input. This table started out as a base tune that was much too rich for the setup (ve numbers too high). After using VE Live there was a small tuned section and a rather large untuned section that the car didn't typically reach because of where the boost was set (21psi) and where the car would misfire because of the untuned portion of the map caused an overly rich condition (5700 rpm).
At 5700 The attached VE table goes from a cell with a value of 86 to a cell of 120. That's why it's going pig rich. In the tuning guide above it says to make sure there are no drastic changes in the numbers at any point in the table. This wasn't manually adjusted in this example. There is also the sharp increase in cell values all the way across the top of the table at the boost pressures that haven't been reached. Vecause it never reaches those cells during a datalog, it doesn't "fix" them when you have the program adjust the table. You need to manually adjust the cells that you don't reach when driving, otherwise it will throw off any cell near there because the system is always using the "average" of the 4 cells closest to where it's running to get the proper fueling. If you have two numbers in the 80's and two in the 120's, the "average" cell value that it's using is around 100 but NONE of the cells in the table are actually 100.
Note the picture I attached, it shows the tuned and untuned sections of the VE table. The two yellow cells are the two I'm referring to that it goes through at 5700 rpm from running good (86) to a rich misfire (120). It's got a good afr in the first cell and then when it goes to the cell to the right (120) it goes extremely rich. This is because 86 to 120 is an addition of about 40% more fuel. The orange line is the path the engine is following during the wide open throttle pull. The blue bubble around the orange line is the cells the ecu is "averaging" from during the pass. Note how it's halfway into the untuned section. This is why you can't allow those untuned sections to stay untuned and expect it to work properly. A slight increase in boost pressure will drastically change the tune in this case because it will reach farther into the untuned section.
Here is a good article explaining why engines want/need different air/fuel ratios under different conditions:
autospeed.com.au/cms/A_1595/article.html
The preferred tuning software is TunerStudio (www.efianalytics.com/TunerStudio/beta/).
Datalog viewing software is Megalogviewer www.ideasandsolutions.biz/MegaLogViewer/download/
The first step of course is to get the engine to start, then to stay running. Once you do the basics like calibrate the TPS in the tuning software, ensure that the timing commanded matches actual timing, and ensure that the sensors appear to be reading correctly on your laptop screen, you're ready to start tuning.
Idle Air/Fuel Ratio Tuning
First the idle fuel cells will almost always need manual tuning. You need to physically see the area's it "floats" in, and make sure their are no drastic table changes. Generally the four primary cells it uses for idle should all have the same VE value. Generally in a stall, as speed drops, load also goes up. Make sure no odd transitions happen in the fuel table there. If it takes a 50% VE to idle at 900 rpm, it probably isn't going to want 20% at 600.
Once the engine is relatively warm (over 160 degrees), you can start tuning the Fuel VE table to dial in the idle air/fuel ratio (AFR). Lower numbers reduces fuel, higher increase fuel. With a relatively tame cam (stock or stage 1) you can expect the wideband reading to be accurate at idle and can therefore modify the cells the engine is idling at until the idle AFR is 14.7:1 or so. You can click-drag to highlight multiple cells in the table and then use the = button on the top right of the table to set the highlighted cells to a particular number value. Typically a change of 3-5 will change the afr by a full point (from 13:1 to 14:1 for instance). I typically select 6-8 cells around where it is currently idling and change them all at once to the same value because once you change the number the idle speed and vacuum will increase/decrease which will move where in the VE table it is currently running. Selecting a number of cells will ensure it stays within the cells you are changing throughout the process.
Idle Air/Fuel Ratio Tuning With Large Cam-Turbo
For those running large cams with lots of overlap (stage 2, stage 3), your idle afr readings won't be accurate because unburnt oxygen is going out the exhaust and skewing the afr value. Readings above 1500 rpm or so will be accurate. In this case, you can use a couple different methods to find the ideal afr target for idle. One is to change the surrounding 6-8 cells and watch the tach. The idle speed should be highest where the AFR is at least within range. Once you get it close, you can stand where the exhaust exits and see how rich it smells. If you can smell a lot of unburnt fuel exiting the exhaust, lower the idle ve numbers to pull some fuel away from the engine at idle. Turbo engines with large cams will typically run best with an indicated idle AFR of 12.5:1-13.5:1.
Idle Air/Fuel Ratio Tuning With Large Cam-Naturally Aspirated
For those running large cams with lots of overlap (typically duration over 225 or so), your idle afr readings won't be accurate because unburnt oxygen is going out the exhaust and skewing the afr value to show lean. Readings above 1500 rpm or so will be accurate. In this case, you can use a couple different methods to find the ideal afr target for idle. One is to change the surrounding 6-8 cells and watch the tach. The idle speed should be highest where the AFR is at least within range. Once you get it close, you can stand where the exhaust exits and see how rich it smells. If you can smell a lot of unburnt fuel exiting the exhaust, lower the idle ve numbers to pull some fuel away from the engine at idle. Typically n/a engines with a large cam will run best with an indicated idle AFR of 16:1-17:1.
Manually Adjusting VE Table For First Drive
Once idle afr is set, you can look at the VE table and see how the numbers surrounding the idle area match the numbers you just set for idle. If it is idling properly with a value 40 for instance and the numbers just to the right or above the idle area is 35 or 55, they need to be modified before you can expect it to drive properly above idle. This is because an increase in rpm (moving right in the table) or a decrease in vacuum/increase in boost (moving up in the table) will require more fuel than the cells below/left of them. This means the general trend will be for the cell numbers to get larger as they go up and to the right so the largest number will be near the top right corner and the smallest will be bottom left.
Once the engine exceeds peak hp rpm, the fuel demands will drop back down a bit as rpm increases. What you can learn from this (besides getting the base table setup safe) is that if you make a low boost pull and find the "ideal" numbers to be around 115 and then notice that the numbers in the next higher boost range are in the 110 range, it's going to run lean when it reaches that cell. Use your brain and realize if it needs 115 at 10psi, it's going to need more than 115 at 15psi. Same theory for rpm increases. If it's safe at 115 at 4500 rpm and the number you didn't reach in the previous pull (so yet untuned) is only 110 at 5000 rpm, raise it to 115 or 118 or something before making the next pull. This will prevent it from going dangerously lean.
If there are any rpms under boost where the tune is way lean, fix it manually rather than driving through it and letting auto tune take care of it. That's a good way to blow a headgasket or worse before you ever get it tuned.
You'll also be much better off from a knowledge standpoint to do some tuning manually before starting auto tuning. Reason being, you'll learn a ton about what your engine wants/needs by doing it manually and this will help tremendously in the future. Just letting auto tune do all of the work is like letting a mechanic do all the work on your car. It may work fine but you won't learn a damn thing and won't be able to diagnose or fix any issues in the future, nor will you be able to use all of the features of the MS2 system and software.
Using VE Live Tuning While Driving-No Boost
You'll want to get the car to idle well, then to be driveable before you start to auto tune using the VE Live tuning tab. At that point, the easy or normal change settings will depend on the length of the drive and how far off the tune is. Initially you'll probably want it on easy so it can change the tune with ease. Drive around cruising without boost and let it dial in the cruising tune until the afr is where it should be (around 14.7:1 under non-boosted conditions), be sure to run through different rpm ranges with different throttle positions (light throttle to 5000 or something, wide open to 2500 then let off, cruising around normally down side streets slowly, highway driving at higher speeds, etc. You want to cover every possible "out of boost" scenario, then start doing a little boost at low rpm and see how close the afr is.
Using VE Live Tuning While Driving-Boost
When driving with low boost, if it's crazy lean (more than 14:1 or so at low boost), manually add some fuel to that area of the map before continuing. The best bet is to give it more fuel than it should need under boost and let auto tune lean it out, not start lean and let it richen it up. Lean kills engines, rich doesn't. By all means do not just floor it and expect the VE Live "auto tune" to fix the afr numbers before it goes lean and blows a headgasket or melts a piston because it won't. You have to manually get it safe (rich) and then let it lean it back out. Your AFR target under boost should be 12.0:1 or so, no leaner than 12.5 and no richer than 11.5.
Sample Fuel VE Table:
Example of How Using an Auto Tune Function Exclusively Can Cause Problems
Here is an example of why you shouldn't just expect any form of "auto tune" to just make everything perfect without your input. This table started out as a base tune that was much too rich for the setup (ve numbers too high). After using VE Live there was a small tuned section and a rather large untuned section that the car didn't typically reach because of where the boost was set (21psi) and where the car would misfire because of the untuned portion of the map caused an overly rich condition (5700 rpm).
At 5700 The attached VE table goes from a cell with a value of 86 to a cell of 120. That's why it's going pig rich. In the tuning guide above it says to make sure there are no drastic changes in the numbers at any point in the table. This wasn't manually adjusted in this example. There is also the sharp increase in cell values all the way across the top of the table at the boost pressures that haven't been reached. Vecause it never reaches those cells during a datalog, it doesn't "fix" them when you have the program adjust the table. You need to manually adjust the cells that you don't reach when driving, otherwise it will throw off any cell near there because the system is always using the "average" of the 4 cells closest to where it's running to get the proper fueling. If you have two numbers in the 80's and two in the 120's, the "average" cell value that it's using is around 100 but NONE of the cells in the table are actually 100.
Note the picture I attached, it shows the tuned and untuned sections of the VE table. The two yellow cells are the two I'm referring to that it goes through at 5700 rpm from running good (86) to a rich misfire (120). It's got a good afr in the first cell and then when it goes to the cell to the right (120) it goes extremely rich. This is because 86 to 120 is an addition of about 40% more fuel. The orange line is the path the engine is following during the wide open throttle pull. The blue bubble around the orange line is the cells the ecu is "averaging" from during the pass. Note how it's halfway into the untuned section. This is why you can't allow those untuned sections to stay untuned and expect it to work properly. A slight increase in boost pressure will drastically change the tune in this case because it will reach farther into the untuned section.
Here is a good article explaining why engines want/need different air/fuel ratios under different conditions:
autospeed.com.au/cms/A_1595/article.html
