Car starts with Stock ECU but not MS
12-04-2019, 12:38 AM
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Car starts with Stock ECU but not MS
So I've got a 1.8 '94 Miata. When I bought the car it had a Voodoo box piggyback ECU on it. The car was running rich and I don't know/don't know anyone who can tune a piggyback so I decided to drop the $800 and buy a MegaSquirt PNP gen2 for my car. (Also, I have a Flyin Miata Turbo Kit on the car). So for those who don't know, the voodoo box is a piggyback ecu that needs to be tapped into the stock wire harness to work. So to remove it, I cut the wires off and respliced them into place. I plugged the stock ECU back into the car, and started it to see if I made any mistakes with my splicing. The car started and idled fine (It actually drives fine as well, I took it for a test drive with the waste gate open to check). So okay, the stock ECU starts and runs the car without a problem, let's put the Megasquirt in. I took it to a guy I know has done numerous Megaquirts before. However after hours of trial and error. The only thing we could get the car to do was crank and die. Crank and die. Maybe a backfire here and there. We tried every base map for the MS on their website, the tuner even tried creating his own basemap. It won't even let us run any logs. I'm at a loss. Why would the car start with the stock ECU but not with the Megasquirt? Is the Megasquirt defective? Any help?
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12-04-2019, 02:18 PM
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Good question. But, even if some of the I/O's are different, the other settings should be correct.
So, perhaps just download the msq from Scott and copy the tables for start-up items; and VE, Spark, etc into your map from DIY.
DNM
So, perhaps just download the msq from Scott and copy the tables for start-up items; and VE, Spark, etc into your map from DIY.
DNM
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12-05-2019, 08:52 PM
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ECU needs to know where the piston is (and where the cams are) in order to know when to spray fuel or fire spark.
It does this through the Cam and Crank angle sensors (being an NA i think you just have the Cam one, which is essentially just a mutant distributor)
The ecu needs to be shown where these sensors are at TDC, so it knows what to look for, and in turn to then fire spark/fuel X degrees before/after that.
Normally you'll start the car, lock timing to 10btdc, then use a timing light and adjust offset until what you see at the crank is bang on 10 degrees. Then unlock the timing and the ECU will do it's usual advance/retard as needed.
Without setting the offset, the ECU is just advancing and retarding timing from an unknown point, and in turn trying to fire spark or spray fuel at the wrong time (which can be pretty cool when you launch a fireball out the intake and explode the piping)
SO yeah, try stuffing with the offset.
or jsut twist the CAS to the extremes of it's adjustment and try to crank (same thing, just one you're doing in software)
Once it tries to idle, get a timing light on there and properly adjust offset.
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12-06-2019, 02:28 AM
#14
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To elaborate here.
ECU needs to know where the piston is (and where the cams are) in order to know when to spray fuel or fire spark.
It does this through the Cam and Crank angle sensors (being an NA i think you just have the Cam one, which is essentially just a mutant distributor)
The ecu needs to be shown where these sensors are at TDC, so it knows what to look for, and in turn to then fire spark/fuel X degrees before/after that.
Normally you'll start the car, lock timing to 10btdc, then use a timing light and adjust offset until what you see at the crank is bang on 10 degrees. Then unlock the timing and the ECU will do it's usual advance/retard as needed.
Without setting the offset, the ECU is just advancing and retarding timing from an unknown point, and in turn trying to fire spark or spray fuel at the wrong time (which can be pretty cool when you launch a fireball out the intake and explode the piping)
SO yeah, try stuffing with the offset.
or jsut twist the CAS to the extremes of it's adjustment and try to crank (same thing, just one you're doing in software)
Once it tries to idle, get a timing light on there and properly adjust offset.
ECU needs to know where the piston is (and where the cams are) in order to know when to spray fuel or fire spark.
It does this through the Cam and Crank angle sensors (being an NA i think you just have the Cam one, which is essentially just a mutant distributor)
The ecu needs to be shown where these sensors are at TDC, so it knows what to look for, and in turn to then fire spark/fuel X degrees before/after that.
Normally you'll start the car, lock timing to 10btdc, then use a timing light and adjust offset until what you see at the crank is bang on 10 degrees. Then unlock the timing and the ECU will do it's usual advance/retard as needed.
Without setting the offset, the ECU is just advancing and retarding timing from an unknown point, and in turn trying to fire spark or spray fuel at the wrong time (which can be pretty cool when you launch a fireball out the intake and explode the piping)
SO yeah, try stuffing with the offset.
or jsut twist the CAS to the extremes of it's adjustment and try to crank (same thing, just one you're doing in software)
Once it tries to idle, get a timing light on there and properly adjust offset.
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12-06-2019, 11:11 AM
#15
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Did you try a regular datalog or a composite log? The composite log will log the crank and cam triggers. That will help tell whether there are crank/cam wiring issues. Just search "megasquirt composite log" for instructions.
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