DIYPNP on a 99
02-11-2010, 10:11 AM
#141
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Somewhere more like 1 nF. The MS1 only needs the signal to be more or less in the right spot, so you can use a ton of filtering on it. MS2/Extra triggers off both edges and is a lot more sensitive to phase shifts.
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02-12-2010, 06:29 PM
#142
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Join Date: Nov 2009
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You really should check the voltage at the battery using a DVM.
When my DVM said 12V battery voltage, MegaTune said 11.6V. Battery voltage is determined with a resistor voltage divider to bring the 12 volts down to under 5V for the MCU to convert. R3 (50K) and R6 (10K) on the Megasquirt PCB form this voltage divider. These are both 5% tolerance resistors and in my case, the ratio was 5.22 instead of 5, causing the difference between actual and MS values for battery voltage. It's best to use 1% resistors for this. It's important to have a correct reading because the MS changes certain values (injector opening time, dwell etc) depending on the input voltage.
If you find that everything is correct and you really measure 15V at the battery check if you used 1% resistors in the alternator circuit. The setpoint is determined with the formula: 2.495V*(1+ R4/R11), so it's important to use 1% resistors for R4 and R11. I used a 5% for R11 and found my setpoint to be 15.1V!
If you used 1%, you might want to replace the 48K7 resistor with a lower value like 47K5 or 46K4. Make sure your setpoint is about 14.4V. In your case, you'd have to use the 46K4 resistor to get 14.4V if you now have 15V.
Although 15V is still within spec, I don't feel comfortable with it. Your bulbs as well as your battery will live longer at 14.4V
When my DVM said 12V battery voltage, MegaTune said 11.6V. Battery voltage is determined with a resistor voltage divider to bring the 12 volts down to under 5V for the MCU to convert. R3 (50K) and R6 (10K) on the Megasquirt PCB form this voltage divider. These are both 5% tolerance resistors and in my case, the ratio was 5.22 instead of 5, causing the difference between actual and MS values for battery voltage. It's best to use 1% resistors for this. It's important to have a correct reading because the MS changes certain values (injector opening time, dwell etc) depending on the input voltage.
If you find that everything is correct and you really measure 15V at the battery check if you used 1% resistors in the alternator circuit. The setpoint is determined with the formula: 2.495V*(1+ R4/R11), so it's important to use 1% resistors for R4 and R11. I used a 5% for R11 and found my setpoint to be 15.1V!
If you used 1%, you might want to replace the 48K7 resistor with a lower value like 47K5 or 46K4. Make sure your setpoint is about 14.4V. In your case, you'd have to use the 46K4 resistor to get 14.4V if you now have 15V.
Although 15V is still within spec, I don't feel comfortable with it. Your bulbs as well as your battery will live longer at 14.4V
Frank, we put enough resistors together to get 46K4 and it charges at 14.5v. It was really 15.1 before (at the battery) so you were right on it. We may drop it a little lower to reduce the load on the car, we run a tiny battery and it only needs to crank it a few times before we put it back on a battery tender. Thanks for your help, it's people like you that make this easy for the rest of us.
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09-16-2011, 10:52 PM
#150
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Location: Portland Oregon
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As I waited with baited breath to see if the project would succeed I was rewarded with.......a cliff hanger???? You're killin' me here.
This project thread is the answer to the people who have to go through updated smog emissions testing prayers. And how on earth did it manage to get nearly 2 years old???
I know its bad form to resurrect bygone posts, but seriously, this one is worth it.
Additionally,
1) I've always assumed "piggyback" and "parallel" were interchangeable. Am I somehow missing something here?
2) If so, what.
Many thanx,
Cobra
This project thread is the answer to the people who have to go through updated smog emissions testing prayers. And how on earth did it manage to get nearly 2 years old???
I know its bad form to resurrect bygone posts, but seriously, this one is worth it.
Additionally,
1) I've always assumed "piggyback" and "parallel" were interchangeable. Am I somehow missing something here?
2) If so, what.
Many thanx,
Cobra
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09-19-2011, 11:30 AM
#151
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Real quick-- different between a 'piggyback' and a 'parallel' install:
A Piggyback simply tricks the stock computer by intercepting the inputs to the ECU and modifying them to make the stock computer act differently. The inputs aren't shared, they are cut, modified, and the tweaked signals go on to the stock ECU.
A Parallel install leaves both the stock computer, and another standalone ECU, in place. They 'share' inputs, and both computer think they have control of the engine. You can then divy up the outputs. Wanna run the stock computer controller the ignition and idle valve, and the MS ECU running the fuel outputs and the boost control? Just wire up the outputs from each unit to control what you want them to.
Most people use it to allow the stock computer to control everything lame, and to let the standalone control the fun stuff (fuel, ignition, boost, etc)
A Piggyback simply tricks the stock computer by intercepting the inputs to the ECU and modifying them to make the stock computer act differently. The inputs aren't shared, they are cut, modified, and the tweaked signals go on to the stock ECU.
A Parallel install leaves both the stock computer, and another standalone ECU, in place. They 'share' inputs, and both computer think they have control of the engine. You can then divy up the outputs. Wanna run the stock computer controller the ignition and idle valve, and the MS ECU running the fuel outputs and the boost control? Just wire up the outputs from each unit to control what you want them to.
Most people use it to allow the stock computer to control everything lame, and to let the standalone control the fun stuff (fuel, ignition, boost, etc)
__________________
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
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09-19-2011, 07:10 PM
#152
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Join Date: Aug 2011
Location: Portland Oregon
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Thank you for the clarification Jerry. Good info to have in my pocket.
From all that I've been able to ascertain, neither of the two options are ironed out to the point that they're dependable enough to make it through an OBDII inspection without worry. With that in mind, I get the real feeling the solution is to look for a '94 or '95 (need that 1.8 rear end) to use for a platform and tell the OBDII inspector he can eat my shorts.
---Cobra
From all that I've been able to ascertain, neither of the two options are ironed out to the point that they're dependable enough to make it through an OBDII inspection without worry. With that in mind, I get the real feeling the solution is to look for a '94 or '95 (need that 1.8 rear end) to use for a platform and tell the OBDII inspector he can eat my shorts.
---Cobra
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