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Post by subyswamper on Mar 22, 2009 10:14:51 GMT -5
I am just looking for some pointers on converting a carbed justy over to mpfi. Anyone got some good diagrams or pictures ect? I am considering just grabbing a whole mpfi harness and changing everything. Is that more work than is needed?
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Post by hollandjusty on Mar 22, 2009 11:38:34 GMT -5
you'd need a mpfi ECU, mpfi engine wiring, mpfi cylinderhead + inlet + exhaust, You might need bigger fuel lines + an other fuel pump. I think that's all
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Post by jeremydde on Mar 22, 2009 15:37:30 GMT -5
Check out my turbo build thread. I converted the carbed motor to fuel injection with a megasquirt. I showed how I did the fuel pump as well. I was able to use the factory fuel lines and haven't had any problems with that so far. The factory fuel injected engine harness didn't plug into the carbed body harness, so you would probably have to remove the dash and replace all that wiring as well if you want to use the factory FI parts.
Jeremy
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Post by Deleted on Mar 22, 2009 16:07:26 GMT -5
I too am interested in this. Here's a link to a previous discussion. subarujusty.proboards20.com/index.cgi?board=engine&action=display&thread=1208It drifts off topic, but shows some stuff. For those of us (me), who have never done this, but plan to do the swap, it would be nice to develop a bit of a write up for both the Megasquirt and factory set-up in the future. Thank you hollandjusty for the list of needed parts-that really helps at the junkyard. And jeremydde, you make an amazing turbo build look like an afternoon project. The megaquirt diagram you provded is great. Neither of these two options sound too complicated. Are there tricky or critical points that we should know about?
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Post by jeremydde on Mar 22, 2009 16:17:17 GMT -5
I too am interested in this. Here's a link to a previous discussion. subarujusty.proboards20.com/index.cgi?board=engine&action=display&thread=1208It drifts off topic, but shows some stuff. For those of us (me), who have never done this, but plan to do the swap, it would be nice to develop a bit of a write up for both the Megasquirt and factory set-up in the future. Thank you hollandjusty for the list of needed parts-that really helps at the junkyard. And jeremydde, you make an amazing turbo build look like an afternoon project. The megaquirt diagram you provded is great. Neither of these two options sound too complicated. Are there tricky or critical points that we should know about? I tried to modify the megasquirt diagram to closely reflect our application. I can provide assistance to anyone who needs help and would like to further pursue the megasquirt. I will also post my finalized MSQ file for those that do go forward to have a decent starting point to work off of. The megasquirt installation is straightforward providing that you follow the instructions closely. The tuning aspect of it can be overwhelming however, especially for a first timer. I have the proper equipment to accomplish each task which is why it appears to be an "afternoon project". My current map is fully wideband tuned already, but with the larger injectors. I have a basic get you up and running map on the factory injectors as well. Jeremy
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Post by subyswamper on Mar 23, 2009 8:19:49 GMT -5
Thanks for the help with that.
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Post by jeremydde on Mar 23, 2009 17:54:54 GMT -5
I have been asked to clarify my last post regarding my MSQ file and fuel maps in general. When I refer to my "fuel map", this is independant of the map sensor hardware. All fuel injection computers need a basic firmware/software embedded within them to run an engine correctly. This is a load vs rpm chart that is programmed into the ecu (Engine Control Unit) so that when the engine RPM matches a specific load cell (Pressure value) in the chart the ecu can inject the proper amount of fuel via the fuel injectors. Vehicles with map sensors (Like the Justy) vary in vacuum pressure depending on the amount of throttle that is applied at any given RPM. This means that depending on the ecu's resolution this can require a significant amount of programming. As illustrated below, we have a 12 x 12 fuel map from the megasquirt that was downloaded off of my running Justy. The numbers in the chart aren't really important themselves, it's the change in those numbers that is important. Behind these fuel maps are injector scalars. That is to say that I could set the idle cells (Low vacuum, Low RPM) to 0 and scale the rest of the map out. That would mean that both the charts below are actually the same map, but with different scalars (multipliers). The ecu converts these values into injector pulsewidths accordingly. As you can see, the ecu relies almost entirely on the map sensor, and the distributor's ignition signal (RPM). The remaining engine sensors (Coolant Temp ECT, Intake Air Temp IAT, Throttle Position TPS, & O2) are all present for corrections only. The o2 sensor can make subtle changes to the injector pulsewidths to compensate for natural fluctuations. The ECT is present to allow the car to start and warmup with different temperatures. Cold dense air requires more fuel. This is the same with the IAT sensor. The engine may be running optimally, then you drive through a low-land where the air is cooler, and denser. The ecu has to compensate otherwise you would run lean. Those of you who ride a motorcycle would understand how quickly the air temp can change in certain areas when you ride. Here is another fuel map from a 650 HP Honda with alot of resolution. By resolution I refer to the number of steps between each rpm and load point. The higher the resolution, the more precisely tuned the engine can be. However, this kind of resolution can be quite time consuming to program compared to the 12 x 12 map above. So when I was referring to my "MSQ" file for the megasquirt, I was referring to the ecu basic programming, along with the fuel/timing maps along with it. Hope I am not too far off topic... Jeremy
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Post by jeremydde on Mar 23, 2009 19:39:30 GMT -5
-Do you enter the map values via computer interface or MegaSquirt "keypad" on dash? Most modern standalone computers, including chippable factory ecu's are fully tuned via laptop. Some manufacturers give you the option of a handheld controller as well. The handheld controllers have small screens and are usually a pain to fully tune an engine with. They are really only good for minor changes after you have your fuel/timing maps very close. -Are the 2 first maps for stock injectors? Technically they are for any injector size within reason. The key is the injector scalar. The point I was trying to get across is that once you have a tuned fuel map, changing the injectors requires a change to the injector multiplier. The first map could be "stock" injector, and the second the larger injector. Or the first map could be the bigger injector, and the injector multiplier is lowered accordingly to compensate. -What is MSQ? megasquirt Q____? MSQ is just a file name, like jpg. The software saves/opens MSQ files. This is just specific to megasquirt. Most engines open up "bin" files. Again this is just a file type. Nothing technical here. -If you've done away with a MAP sensor, how does the computer know the pressure. Does this 'load cell' do it? We haven't done away with the map sensor at all. Each load cell ie 150kpa @ 5000rpm would be a load cell. The map sensor is integral to the functioning of the engine. The map sensor reads that the engine is at 150kpa (~7psi boost) at 5000rpm. It then responds by injecting fuel based on the load cell that corresponds to 150kpa @ 5000rpm. In the first map this would be 97 (which the computer than equates into injector puleswidth). -Is there another map that you set timing advance values? Yes there is. It works exactly the same way that the fuel map does. It has "load cells" as well. In this case the numbers in the chart correspond with timing advance. This is the timing to fire the spark plug before top dead center (BTDC). When you turbo an engine, you have to be able to pull timing. This means that instead of running 25 degrees advance at 5psi, we want to burn the mixture a bit later, like 15 degrees as an example. This is called retarding the timing. Jeremy
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