New Megasquirt ECU - What features do you want?
Thread Starter
Joined: Jun 2006
Posts: 6,020
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From: Athens, Greece
How about a voltage inverse multiplier feedforward for various linear solenoids (e.g. idle, VVT)?
A solenoid's position is a function of duty cycle and system voltage.
If voltage abruptly drops, the solenoid will close a bit. A multiplier will prevent this.
For example. You're idling at 14V and have 50% on some solenoid.
Fans kick on and voltage abruptly drops 10% lower. All solenoids will close down by 10%. If the duty cycle were all automatically increased by 10%, they wouldn't.
Here's the equation, which assumes 14V is the "normal" system voltage:
corrected_duty = duty * 14V/actual_voltage
This equation works when said solenoid or pulldown driver output has a "flyback" diode to 12V.
------- another suggestion ---------
Staggered delay for the 2 fans:
second fan turns on 3 seconds after first fan
---- or ----
3 fan relay outputs - these 3 relays will be wired so that the fans can be run in 2 modes: low, where the fans are connected in series, and hi, where both fans see 12V. Then you have 2 thresholds for CLT fan triggers, e.g. fans on low at 90*C, high at 95*C, with 2* of hysteresis...
A solenoid's position is a function of duty cycle and system voltage.
If voltage abruptly drops, the solenoid will close a bit. A multiplier will prevent this.
For example. You're idling at 14V and have 50% on some solenoid.
Fans kick on and voltage abruptly drops 10% lower. All solenoids will close down by 10%. If the duty cycle were all automatically increased by 10%, they wouldn't.
Here's the equation, which assumes 14V is the "normal" system voltage:
corrected_duty = duty * 14V/actual_voltage
This equation works when said solenoid or pulldown driver output has a "flyback" diode to 12V.
------- another suggestion ---------
Staggered delay for the 2 fans:
second fan turns on 3 seconds after first fan
---- or ----
3 fan relay outputs - these 3 relays will be wired so that the fans can be run in 2 modes: low, where the fans are connected in series, and hi, where both fans see 12V. Then you have 2 thresholds for CLT fan triggers, e.g. fans on low at 90*C, high at 95*C, with 2* of hysteresis...
The Enhanced MS2 does have delay for the fans:
- In cooling mode, the first fan turns on at 95*C, the second at 98*C.
- In A/C mode, the first fan turns on 250ms after the A/C compressor, and the second fan 150ms after the first.
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Elite Member
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A %IAC correction table would help a lot but isn't mathematically correct for all cases 
For example, if solenoid is running at 20% and the correction is +5% for a 1V drop, then if solenoid is running at 40% the proper correction for a 1V drop will be +10%, not +5%. (it should be a multiplier, not an adder)
Re: VVT solenoid. FWIW voltage can drop due to other issues than fans coming on at idle.
In A/C mode perhaps it's better to increase 2nd fan delay some more?
For example, if solenoid is running at 20% and the correction is +5% for a 1V drop, then if solenoid is running at 40% the proper correction for a 1V drop will be +10%, not +5%. (it should be a multiplier, not an adder)
Re: VVT solenoid. FWIW voltage can drop due to other issues than fans coming on at idle.
In A/C mode perhaps it's better to increase 2nd fan delay some more?
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Thread Starter
Joined: Jun 2006
Posts: 6,020
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From: Athens, Greece
My mistake the IAC correction is a multiplier, not an adder.
On the VVT solenoid, any reasons that voltage can drop above idle? Because it doesn't matter at all during idle.
As for the A/C, a programmable delay sounds better, yes.
On the VVT solenoid, any reasons that voltage can drop above idle? Because it doesn't matter at all during idle.
As for the A/C, a programmable delay sounds better, yes.
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Joined: Sep 2005
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From: Chicago. (The less-murder part.)
Since you mentioned this, I'll go ahead and make a feature-request.
Forget about the MS2.
Seriously. Backwards-comparability sounds cool and all, but it always winds up compromising the design. Backwards-compatibility was responsible for bringing us such marvelously unsuccessful products as the Apple III, the Commodore 128, and the Atari 7800. It's why Intel machines of the 1990s struggled with such a retardedly complex memory architecture, why the NTSC television standard was known as "Never Twice the Same Color" among industry professionals, and why a "standard gauge" railroad is built to the incomprehensible track spacing of 4 feet 8½ inches.
The MS2 is the past. If you're going to design an Uber-ECU, don't be held back by old farts like me running obsolete CPU architectures.
Forget about the MS2.
Seriously. Backwards-comparability sounds cool and all, but it always winds up compromising the design. Backwards-compatibility was responsible for bringing us such marvelously unsuccessful products as the Apple III, the Commodore 128, and the Atari 7800. It's why Intel machines of the 1990s struggled with such a retardedly complex memory architecture, why the NTSC television standard was known as "Never Twice the Same Color" among industry professionals, and why a "standard gauge" railroad is built to the incomprehensible track spacing of 4 feet 8½ inches.
The MS2 is the past. If you're going to design an Uber-ECU, don't be held back by old farts like me running obsolete CPU architectures.
Last edited by Joe Perez; Jun 27, 2012 at 05:10 PM. Reason: Added criticism of Atari 7800.
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Elite Member
Joined: Jul 2005
Posts: 6,420
Total Cats: 84
My suggestions stand (for MS3).
Here are 2 more:
Megasquirt MSEXTRA / MS3EFI • Suggestion: Variable proportional to airflow (View topic)
Megasquirt MSEXTRA / MS3EFI • fuel calc suggestion: VE vs. RPM and calced from AFR targets (View topic)
Here are 2 more:
Megasquirt MSEXTRA / MS3EFI • Suggestion: Variable proportional to airflow (View topic)
Megasquirt MSEXTRA / MS3EFI • fuel calc suggestion: VE vs. RPM and calced from AFR targets (View topic)
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Thread Starter
Joined: Jun 2006
Posts: 6,020
Total Cats: 369
From: Athens, Greece
Since you mentioned this, I'll go ahead and make a feature-request.
Forget about the MS2.
Seriously. Backwards-comparability sounds cool and all, but it always winds up compromising the design. Backwards-compatibility was responsible for bringing us such marvelously unsuccessful products as the Apple III, the Commodore 128, and the Atari 7800. It's why Intel machines of the 1990s struggled with such a retardedly complex memory architecture, why the NTSC television standard was known as "Never Twice the Same Color" among industry professionals, and why a "standard gauge" railroad is built to the incomprehensible track spacing of 4 feet 8½ inches.
The MS2 is the past. If you're going to design an Uber-ECU, don't be held back by old farts like me running obsolete CPU architectures.
Forget about the MS2.
Seriously. Backwards-comparability sounds cool and all, but it always winds up compromising the design. Backwards-compatibility was responsible for bringing us such marvelously unsuccessful products as the Apple III, the Commodore 128, and the Atari 7800. It's why Intel machines of the 1990s struggled with such a retardedly complex memory architecture, why the NTSC television standard was known as "Never Twice the Same Color" among industry professionals, and why a "standard gauge" railroad is built to the incomprehensible track spacing of 4 feet 8½ inches.
The MS2 is the past. If you're going to design an Uber-ECU, don't be held back by old farts like me running obsolete CPU architectures.
Also, the MS3 is +$100, while the MS2 is just fine for a LOT of people. If I can make the ECU compatible with both, and ship it as an MS2 but instantly MS3-upgreadable without sacrificing anything, that would be a good deal.
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Thread Starter
Joined: Jun 2006
Posts: 6,020
Total Cats: 369
From: Athens, Greece
My suggestions stand (for MS3).
Here are 2 more:
Megasquirt MSEXTRA / MS3EFI • Suggestion: Variable proportional to airflow (View topic)
Megasquirt MSEXTRA / MS3EFI • fuel calc suggestion: VE vs. RPM and calced from AFR targets (View topic)
Here are 2 more:
Megasquirt MSEXTRA / MS3EFI • Suggestion: Variable proportional to airflow (View topic)
Megasquirt MSEXTRA / MS3EFI • fuel calc suggestion: VE vs. RPM and calced from AFR targets (View topic)
The second suggestion, I need to read it a little carefully.
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Joined: Jun 2006
Posts: 29,085
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From: Republic of Dallas
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What about onboard bluetooth aswell?
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Thread Starter
Joined: Jun 2006
Posts: 6,020
Total Cats: 369
From: Athens, Greece
The seat belt light is inaccessible from the stock ECU harness, this means that rewiring is required.
The CEL starts blinking at approx 220*F.
Onboard bluetooth is not a very good idea, as the metal enclosure will block off the signal. Having an external antenna may help, but that does increase the cost and complexity a bit too much. Besides, I will probably add a wireless option that will have a one-mile range (but it will be PC-only).
The CEL starts blinking at approx 220*F.
Onboard bluetooth is not a very good idea, as the metal enclosure will block off the signal. Having an external antenna may help, but that does increase the cost and complexity a bit too much. Besides, I will probably add a wireless option that will have a one-mile range (but it will be PC-only).
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