Captain Bondo
09-13-2005, 04:22 AM
Ok so I've had this idea for a while, it's 1AM and I'm totally wired and am still unemployed, so prepare to bask in the glory of a kid with too much time on his hands.
Concept: Home-Made Electronic Distributor
Now, the distributor in a typical MS car does two things:
1)It gives you 4 pulses per cam revolution. So you get the 4 sparks you need.
2)it has a rotor which basically acts as a traffic controller. It tell's each of the 4 sparks what cylinder to fire.
Now then, T6 motor's are a bastard because, well, they don't have distributors. And the rest of us might as well face it, distributors are weak sauce these days.
Now then, on a t6 life is a b*tch because it has six friggin coils. How you gonna drive six coils? Well, ,you can buy edist for 350 friggin bucks, or you can buy an expensive-ass engine management system for the safe of getting 2 more ignition outputs. So that's about 800 bucks an output. :roll:
But really- shouldn't it be a simple task to make a box that can take a single ignition output, and turn it into as many outputs as we want? We know the firing order, we know how far apart the pulses are, what's the problem?
So here's the deal. You need two signals.
Tach signal for timing reference. Use the 60-2 flywheel. ok check.
cam position so we can phase properly. Whiteblocks already have em. You could easily epoxy a magnet to the cam pulley and mount a pickup on a red though. It doesn't need to be accurate at all. You could easily set this up when relatively drunk/tired/confused.
Ok so we have some signals. sweet. ok.
so what we need is a standard edge triggered "counter" chip. only needs three outputs (up to 8 cylinders). I made one from nand gates with schmidt triggers or something once. but anyways they're cheap pre-made.
basically it has 4 outputs (we only need 3 for a six cyl). as it receives pulses, it counts in binary sending the outputs high to represent "1".
So at 0, all o/p's lo- it switches a solidstate relay or transistor that allows a signal to travel to number 1 coil.
an ignition pulse comes, fires that coil, triggers the counter, the counter increments to "1". Our series of logic gates result in a logic low input at one of the nand gates. The ign output of the MS is connected to all of them. When it pulse low, you have two lows. The nand goes high, an inverter after that (with an open collector output and a pull-up resistor goes low, and collapses the coil
The counter keeps incrementing with the ignition output, and when the motor completes 2 revolutions (all cylinder have fired) the cam sensor triggers. The cam sensor is set up to trigger the reset on the counter. The counter goes back to zero, and we start over.
You should be able to trigger as many coils as the counter has output states like this.
So the only tricks here are
1)you might need to delay the ign signal to the counter input. You don't want it to switch until AFTER the coil has fired. The propagation delay of the TTL devices might be enough though.
2)you need to "tell" megasquirt that it needs to send 6 equal ignition pulses for each tach pulse (I assume you could mod the code to do that if you had to?)
Anyways It's amost 2am now. I will make a schematic tomorrow. Yes I am mentally unstable. Don't you guys think it'll work though?
Concept: Home-Made Electronic Distributor
Now, the distributor in a typical MS car does two things:
1)It gives you 4 pulses per cam revolution. So you get the 4 sparks you need.
2)it has a rotor which basically acts as a traffic controller. It tell's each of the 4 sparks what cylinder to fire.
Now then, T6 motor's are a bastard because, well, they don't have distributors. And the rest of us might as well face it, distributors are weak sauce these days.
Now then, on a t6 life is a b*tch because it has six friggin coils. How you gonna drive six coils? Well, ,you can buy edist for 350 friggin bucks, or you can buy an expensive-ass engine management system for the safe of getting 2 more ignition outputs. So that's about 800 bucks an output. :roll:
But really- shouldn't it be a simple task to make a box that can take a single ignition output, and turn it into as many outputs as we want? We know the firing order, we know how far apart the pulses are, what's the problem?
So here's the deal. You need two signals.
Tach signal for timing reference. Use the 60-2 flywheel. ok check.
cam position so we can phase properly. Whiteblocks already have em. You could easily epoxy a magnet to the cam pulley and mount a pickup on a red though. It doesn't need to be accurate at all. You could easily set this up when relatively drunk/tired/confused.
Ok so we have some signals. sweet. ok.
so what we need is a standard edge triggered "counter" chip. only needs three outputs (up to 8 cylinders). I made one from nand gates with schmidt triggers or something once. but anyways they're cheap pre-made.
basically it has 4 outputs (we only need 3 for a six cyl). as it receives pulses, it counts in binary sending the outputs high to represent "1".
So at 0, all o/p's lo- it switches a solidstate relay or transistor that allows a signal to travel to number 1 coil.
an ignition pulse comes, fires that coil, triggers the counter, the counter increments to "1". Our series of logic gates result in a logic low input at one of the nand gates. The ign output of the MS is connected to all of them. When it pulse low, you have two lows. The nand goes high, an inverter after that (with an open collector output and a pull-up resistor goes low, and collapses the coil
The counter keeps incrementing with the ignition output, and when the motor completes 2 revolutions (all cylinder have fired) the cam sensor triggers. The cam sensor is set up to trigger the reset on the counter. The counter goes back to zero, and we start over.
You should be able to trigger as many coils as the counter has output states like this.
So the only tricks here are
1)you might need to delay the ign signal to the counter input. You don't want it to switch until AFTER the coil has fired. The propagation delay of the TTL devices might be enough though.
2)you need to "tell" megasquirt that it needs to send 6 equal ignition pulses for each tach pulse (I assume you could mod the code to do that if you had to?)
Anyways It's amost 2am now. I will make a schematic tomorrow. Yes I am mentally unstable. Don't you guys think it'll work though?