Diy Ignition Amp For Motronic Ml4.1

[davemar 16]

Recently while changing my Mi16 engine from the Jetronic setup to the correct Motronic ML4.1 setup I had all sorts of problems with the ignition amps. After trying a couple of different brands, I still couldn't get the the car the rev without misfiring through the mid-range. At over £30 a go, trying different amps was getting expensive, so I decided to go DIY.

 

As the Motronic ML4.1 ECU sends out a nice square wave on pin1 for the ignition signal, there's none of the signal conditioning that's needed for the distributor pick-up coil type ignition on the Jetronic setup. Therefore the ignition amp just needs to switch based on the ECU's signal, so something simple will do.

 

A bit of research revealed the ISL9V5036P3 IGBT transistor is designed for firing car ignition coils, so I decided to base the circuit around one of those. I've attached the circuit diagram, and you can see how simple it is. Even with a nice metal box (which doubles as a heatsink) the cost of the parts is still less than the standard amps. The auto-reset circuit breaker is optional (Maplin sell them) as I wanted it in there just in case things went wrong.

 

So far the amp has worked flawlessly over the past month or so. The engine revs smoothly and doesn't miss a beat. A vast improvement on the standard amps.

 

So if you're struggling with unreliable amps, you might want to try this circuit.

[jackherer 543]

Good effort, thanks for posting

 

As the Motronic ML4.1 ECU sends out a nice square wave on pin1 for the ignition signal, there's none of the signal conditioning that's needed for the distributor pick-up coil type ignition on the Jetronic setup. Therefore the ignition amp just needs to switch based on the ECU's signal, so something simple will do.

 

Indeed, the standard amp is a bit overkill really, its the same one they used on the 8v so I guess they had a few in stock when they specced the Mi16!

[petert 586]

Good effort! How is the charge time determined?

[davemar 16]

The ECU determines that. It's somewhere between 4-6ms IIRC.

[welshpug 1,657]

so you've essentially created what the later ecu's like the MM 1AP1 on the gti6 have onboard?

[wicked 103 3 Cars]

I think the are/were used on the Megasquirts as well...

[Will Eastman 6]

Sounds good, what is the GND? Also will the unit essentially only have 3 pins? I thought the Mi16 apm had more pins

[pablitosax 1]

Recently while changing my Mi16 engine from the Jetronic setup to the correct Motronic ML4.1 setup I had all sorts of problems with the ignition amps. After trying a couple of different brands, I still couldn't get the the car the rev without misfiring through the mid-range. At over £30 a go, trying different amps was getting expensive, so I decided to go DIY.

 

As the Motronic ML4.1 ECU sends out a nice square wave on pin1 for the ignition signal, there's none of the signal conditioning that's needed for the distributor pick-up coil type ignition on the Jetronic setup. Therefore the ignition amp just needs to switch based on the ECU's signal, so something simple will do.

 

A bit of research revealed the ISL9V5036P3 IGBT transistor is designed for firing car ignition coils, so I decided to base the circuit around one of those. I've attached the circuit diagram, and you can see how simple it is. Even with a nice metal box (which doubles as a heatsink) the cost of the parts is still less than the standard amps. The auto-reset circuit breaker is optional (Maplin sell them) as I wanted it in there just in case things went wrong.

 

So far the amp has worked flawlessly over the past month or so. The engine revs smoothly and doesn't miss a beat. A vast improvement on the standard amps.

 

So if you're struggling with unreliable amps, you might want to try this circuit.

 

Hello davemar:

Your circuit is a "common emitter" amplifier ..is for voltage gain (current indirectly are increased too because the resistance / impedance of the coil is a constant), BUT inverts the signal 180 degrees.

In another words : If you have a pulse on the 12V input to 0V at the collector you will see the opposite , a pulse from 0V to 12V.

If you dont`n need to reverse the signal must add another step to the "amplifier" for example modify this circuit (was made for a Volvo entusiasth to replace points whitout any invert)

(the component list : Component values:

R1 1kohm

R2 1kohm

R3 50ohm

D1 1N4007

D2 1N4007

D3 400V zener diode 1.5KE400

T1 2N7000 Mosfet

T2 BUK854-500IS IGBT )

Edited November 23, 2015 by pablitosax