Miata Needs a Real ECM
07-21-2014, 01:58 PM
#1
Supreme Member
Thread Starter
Join Date: Feb 2002
Location: Buckhannon, WV
Posts: 2,663
Likes: 0
Received 3 Likes
on
2 Posts
Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
Miata Needs a Real ECM
It's been a while folks......like 10 years since I've been active on the forum. In case anyone remembers me I had a TBI system on my Monte, that now lives on in my brothers camaro running his HO crate motor clone.
New project for me, need to put a real ecm in this auto-x car I picked up. The OBD 1 Miata system is crap, no data to log, no knock sensor, not boost friendly, and most importantly it's not tuneable. I'll use this thread to document my conversion. Ideally I would like to reuse all or at least most of the mazda sensors and harness but I'm prepared to yank it all and start over if need be.
First issue, the Miata motor uses a "crank angle sensor" CAS for short, this has dual hall effect sensors that get conditioned to pulse at 5 volts. One pulses 4 times per cam revolution one for each cylinder TDC. The other pulses twice per cam revolution, true engine TDC I suppose. I know the DIS systems we play with uses a hall effect sensor. I also know the ignition module converts this signal to something the ECM can understand. Any chance I can hook this up directly to the ECM? Will the ignition module work off of this 5 volt signal since it's just looking for a cross at 0 volts?
This is the big hurdle, would love to stay away from an external reluctor wheel and and sensor if possible. Next step will be deciding if the mazda coil pack will work....but baby steps are in order at the moment. I'm leaning towards a 730' ecm since there are 4cyl variations of code I could start with but I'm open to suggestions.
New project for me, need to put a real ecm in this auto-x car I picked up. The OBD 1 Miata system is crap, no data to log, no knock sensor, not boost friendly, and most importantly it's not tuneable. I'll use this thread to document my conversion. Ideally I would like to reuse all or at least most of the mazda sensors and harness but I'm prepared to yank it all and start over if need be.
First issue, the Miata motor uses a "crank angle sensor" CAS for short, this has dual hall effect sensors that get conditioned to pulse at 5 volts. One pulses 4 times per cam revolution one for each cylinder TDC. The other pulses twice per cam revolution, true engine TDC I suppose. I know the DIS systems we play with uses a hall effect sensor. I also know the ignition module converts this signal to something the ECM can understand. Any chance I can hook this up directly to the ECM? Will the ignition module work off of this 5 volt signal since it's just looking for a cross at 0 volts?
This is the big hurdle, would love to stay away from an external reluctor wheel and and sensor if possible. Next step will be deciding if the mazda coil pack will work....but baby steps are in order at the moment. I'm leaning towards a 730' ecm since there are 4cyl variations of code I could start with but I'm open to suggestions.
Last edited by BMmonteSS; 07-21-2014 at 02:27 PM. Reason: Edited to correct information on Miata CAS sensor
07-21-2014, 02:01 PM
#2
Supreme Member
iTrader: (2)
Join Date: Jan 2005
Location: Hurst, Texas
Posts: 9,995
Received 386 Likes
on
329 Posts
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Re: Miata Needs a Real ECM
It's been a while folks......like 10 years since I've been active on the forum. In case anyone remembers me I had a TBI system on my Monte, that now lives on in my brothers camaro running his HO crate motor clone.
New project for me, need to put a real ecm in this auto-x car I picked up. The OBD 1 Miata system is crap, no data to log, no knock sensor, not boost friendly, and most importantly it's not tuneable. I'll use this thread to document my conversion. Ideally I would like to reuse all or at least most of the mazda sensors and harness but I'm prepared to yank it all and start over if need be.
First issue, the Miata motor uses a "crank angle sensor" CAS for short, this has dual optical sensors that pulse at 5 volts. One pulses 4 times per cam revolution one for each cylinder TDC. The other pulses once per cam revolution, true engine TDC I suppose. I know the DIS systems we play with uses a hall effect sensor which is a different signal type all together. I also know the ignition module converts this signal to something the ECM can understand. Any chance I can hook this up directly to the ECM? Will the ignition module work off of this 5 volt signal since it's just looking for a cross at 0 volts?
This is the big hurdle, would love to stay away from an external reluctor wheel and and sensor if possible. Next step will be deciding if the mazda coil pack will work....but baby steps are in order at the moment. I'm leaning towards a 730' ecm since there are 4cyl variations of code I could start with but I'm open to suggestions.
New project for me, need to put a real ecm in this auto-x car I picked up. The OBD 1 Miata system is crap, no data to log, no knock sensor, not boost friendly, and most importantly it's not tuneable. I'll use this thread to document my conversion. Ideally I would like to reuse all or at least most of the mazda sensors and harness but I'm prepared to yank it all and start over if need be.
First issue, the Miata motor uses a "crank angle sensor" CAS for short, this has dual optical sensors that pulse at 5 volts. One pulses 4 times per cam revolution one for each cylinder TDC. The other pulses once per cam revolution, true engine TDC I suppose. I know the DIS systems we play with uses a hall effect sensor which is a different signal type all together. I also know the ignition module converts this signal to something the ECM can understand. Any chance I can hook this up directly to the ECM? Will the ignition module work off of this 5 volt signal since it's just looking for a cross at 0 volts?
This is the big hurdle, would love to stay away from an external reluctor wheel and and sensor if possible. Next step will be deciding if the mazda coil pack will work....but baby steps are in order at the moment. I'm leaning towards a 730' ecm since there are 4cyl variations of code I could start with but I'm open to suggestions.
07-21-2014, 02:05 PM
#3
Supreme Member
Thread Starter
Join Date: Feb 2002
Location: Buckhannon, WV
Posts: 2,663
Likes: 0
Received 3 Likes
on
2 Posts
Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
Re: Miata Needs a Real ECM
Hey Fast,
Been a long time, you really helped me out in my TBI days. Megasquirt is the easy out, but at 800$ it's not really up my alley. Pretty much all my tuning experience is with GM stuff, and I have a ton of parts laying around. Guess I'm cheap like that.
The Miata motor is called the "BP" engine and the fords used it extensively. Lots of parts swap between. Again, hate to learn a new platform with the ford stuff but that sounds like a good plan B if I can't figure out an easy path with the GM stuff.
Ninja Edit:
Just found a really good explanation of the Miata CAS, looks like I was wrong and my 95' has the hall effect sensors but still out puts a switching 5v signal, so it must have some sort of ignition module built into the module.
http://www.rivercityroad.com/garage/cas.htm
Been a long time, you really helped me out in my TBI days. Megasquirt is the easy out, but at 800$ it's not really up my alley. Pretty much all my tuning experience is with GM stuff, and I have a ton of parts laying around. Guess I'm cheap like that.
The Miata motor is called the "BP" engine and the fords used it extensively. Lots of parts swap between. Again, hate to learn a new platform with the ford stuff but that sounds like a good plan B if I can't figure out an easy path with the GM stuff.
Ninja Edit:
Just found a really good explanation of the Miata CAS, looks like I was wrong and my 95' has the hall effect sensors but still out puts a switching 5v signal, so it must have some sort of ignition module built into the module.
http://www.rivercityroad.com/garage/cas.htm
Last edited by BMmonteSS; 07-21-2014 at 02:13 PM.
Thread
Thread Starter
Forum
Replies
Last Post
Pac J
Tech / General Engine
3
05-17-2020 10:44 AM