Calling all Porsche Megasquirt Nerds, Ignition questions...

[Gabe.]

Hi all,

I'm new to this, this is my first time digging into a standalone ecu. It has a steep learning curve and I've been enjoying starting to understand the process. I've spent hours searching and have some pretty specific questions when it comes to my desired setup.

I have an MS2 with a v3.57 board. I've recently rebuilt my 3.2 Carrera engine with JE 10.5:1 pistons and have twin plugged my heads in the process. It has a 36-1 crank trigger and no cam trigger(yet?) so wasted spark is all I can do at the moment (without going back to a distributor).

When it comes to COP, is there a desired setup to run wasted spark? Can the v3.57 board do this natively? In the most recent v3.57 hardware manual (2/2/2016), section 5.3.1.4 illustrates that the ecu is setup for the resistor method for Spark A, B, & C. However this requires "going low" and seems to be the least desirable method. Can each one of those channels potentially trigger 4 coils? That would be Wasted Spark on 2 cylinders with 4 total plugs. Are there any specific ignition coils that work well with this setup?

If that isn't the most desirable method and "going high" is preferred, I've been having a hard time finding documentation on adding the TC4427 circuits to the 3.57 board (like where could you actually install them? Or do you need to add a prototype board somewhere? That seems to open up the type of coils we can use, whether VAG R8 coils, LS2 coils, Toyota, etc.

At this point I'm looking for some guidance for those of you that have already done this before.

Thanks in advance for your help!
Gabe

[targa44]

Have you tried the MSextra forum? Lot's of help there.

[Nux]

ah the joy of Megasquirt and ignition.......

I would not recommend wasted spark with COP. Wasted spark can be used if your using good strong coil packs. The COP solution does not offer enough spark in a wasted spark mode.

You need to ad a cam sensor or use coil packs.

The easy and cheap way is to use a "smart coil pack". Most post ´98 or so is a smart coil pack. You can get VR6 smart coils very cheap.

Then ad 4.7K Ohm from 5V proto to d15, d16 and d17. From the same soldering point to db37 IGN, SPR3 an SPR2 (if you are not allready using those). There's your ignition output.

I'm starting to dislike Megasquirt. Too much messing around.

I'm going VEMS next time

[Gabe.]

Originally Posted by targa44

Have you tried the MSextra forum? Lot's of help there.

I've done a lot of searches there but haven't yet made a thread. Figured I'd start by going to the place where there are more twin plug engines.

Originally Posted by Nux

ah the joy of Megasquirt and ignition.......

I would not recommend wasted spark with COP. Wasted spark can be used if your using good strong coil packs. The COP solution does not offer enough spark in a wasted spark mode.

You need to ad a cam sensor or use coil packs.

The easy and cheap way is to use a "smart coil pack". Most post ´98 or so is a smart coil pack. You can get VR6 smart coils very cheap.

Then ad 4.7K Ohm from 5V proto to d15, d16 and d17. From the same soldering point to db37 IGN, SPR3 an SPR2 (if you are not allready using those). There's your ignition output.

I'm starting to dislike Megasquirt. Too much messing around.

I'm going VEMS next time

Haha, I do have to say that digging into the hardware and electronic aspect of it has given me a greater appreciation for some of the newer ecus. It's also helped me understand how these work which is always useful for a greater understanding.

I think that adding a cam sensor might be the best bet so that I can run sequential. I'll start searching but does anyone have any good diys on converting a distributor into a cam sensor?

[jpnovak]

Let's clarify a few things.

1. Most modern ECUs can handle a wide range of inputs. The configuration is different but the capability is there.
2. Pick an input trigger that works with your 911. Your 3.2 stock flywheel does not play well with other ECU inputs. There are 2 options. Crank pulley trigger or 965 flywheel trigger. The 965 flywheel gives you a 60-2 tooth pattern and is bolt-on. You can use the stock VR trigger rewired to connect to your MS-ECU. The crank pulley can be modified with magnets and a hall effect sensor or a replacement pulley with a 36-1 toothed wheel added behind the pulley. Pick one and go with it. They are both equally effective.
3. The MS2 ECU is software configurable for a "high" rising edge or "Low" trailing edge trigger signal. Takes a few seconds to setup properly to match your coil of choice.
4. COPs in general have a weak spark compared to modern CDIs. Not a problem unless you are running highly rich mixtures or boost.
5. You want to install a 4 wire "logic level" COP. This is also called a smart coil. Uses a voltage signal to trigger the coil to fire. Power and ground come from separate wires. This does not put electrical load on the ECU - meaning the ECU transistors do not have to provide the current to fire the coil.
6. If you are using logic level COPs they can be easily connected in parallel. twin plug wasted spark is no problem for this type of configuration. There are several output channels that get your to 3 channels of spark.
7. You can run 6 channel sequential as described above. Yes, you need another input from cam to run sequential so that the ECU knows if its on the #1 or #4 crank rotation. This setup limits I/O channels for other devices and usually requires a separate driver board to convert logic level signals with pull-up and pull-down resistors to make sure you get a very clean signal. Up to you if you want to wire this way.
8. Yes, you can use the distributor as a TDC indicator for sequential. simple way would be to epoxy a magnet on the distributor shaft and put a hall effect sensor. Or use a VR sensor and some metal bolt/screw in same manner. Make sure the position of this sensor is adjustable so that you can control the phase angle where it triggers relative to TDC.
9. Most use a Clewett sensor setup on the backside of the 1-3 cam.

[Peter M]

Excellent post Jamie!

Is a 965 flywheel a bolt in replacement for a standard 3.2 flywheel?

Thanks
Peter

[Gabe.]

Originally Posted by jpnovak

Let's clarify a few things.

1. Most modern ECUs can handle a wide range of inputs. The configuration is different but the capability is there.
2. Pick an input trigger that works with your 911. Your 3.2 stock flywheel does not play well with other ECU inputs. There are 2 options. Crank pulley trigger or 965 flywheel trigger. The 965 flywheel gives you a 60-2 tooth pattern and is bolt-on. You can use the stock VR trigger rewired to connect to your MS-ECU. The crank pulley can be modified with magnets and a hall effect sensor or a replacement pulley with a 36-1 toothed wheel added behind the pulley. Pick one and go with it. They are both equally effective.
3. The MS2 ECU is software configurable for a "high" rising edge or "Low" trailing edge trigger signal. Takes a few seconds to setup properly to match your coil of choice.
4. COPs in general have a weak spark compared to modern CDIs. Not a problem unless you are running highly rich mixtures or boost.
5. You want to install a 4 wire "logic level" COP. This is also called a smart coil. Uses a voltage signal to trigger the coil to fire. Power and ground come from separate wires. This does not put electrical load on the ECU - meaning the ECU transistors do not have to provide the current to fire the coil.
6. If you are using logic level COPs they can be easily connected in parallel. twin plug wasted spark is no problem for this type of configuration. There are several output channels that get your to 3 channels of spark.
7. You can run 6 channel sequential as described above. Yes, you need another input from cam to run sequential so that the ECU knows if its on the #1 or #4 crank rotation. This setup limits I/O channels for other devices and usually requires a separate driver board to convert logic level signals with pull-up and pull-down resistors to make sure you get a very clean signal. Up to you if you want to wire this way.
8. Yes, you can use the distributor as a TDC indicator for sequential. simple way would be to epoxy a magnet on the distributor shaft and put a hall effect sensor. Or use a VR sensor and some metal bolt/screw in same manner. Make sure the position of this sensor is adjustable so that you can control the phase angle where it triggers relative to TDC.
9. Most use a Clewett sensor setup on the backside of the 1-3 cam.

Thanks for your two cents Jamie! I was hoping you'd offer up your advice. That's a great list for anyone searching for megasquirt advice in the future.

It seems to me that it's worth adding a cam sensor, I think the Clewett setup would require some mods to a 3.2 cam housing to accommodate. Which leads me to modding my original distributor, I'm open to figuring that out myself or having Clewett make the mods. I found out two weeks ago that he's right down the street from me, really nice guy!

As for the coils, there wasn't really a concrete list out there of what preferred the "high" rising edge or "Low" falling edge ignition coil options were, just that going High was the preferred method and that you need to modify the 3.57 board with TC4427 chips that invert the signal. That all makes sense, I just don't know where to put all the stuff inside the case because the 3.57 board doesn't have the same prototyping area that the 3.0 board does.

As for also having CDI, I don't fully understand what it does. Reading through your thread, project minne has megasquirt, a distributor, and ignition coils. What functionality does the CDI add to that setup that could otherwise run the ignition on it's own? Is it just a different spark wave? Or the second spark that it offers?

Thanks to all of you for your advice! This is new territory and something I'm excited to understand.

[ohecht]

It’s been a while since I’ve looked at tweaking my setup...I’ve been running EDIS twin plug sequential with MS 3.57, Clewett cam sensor, and GSF 36-1 crank trigger wheel with a VR sensor. The only problem I have is when the engine and/or ambient temps are high and I get misses at very high rpms. I think it’s the VR sensor overheating based on the conditions when it happens and the fact that a few times the sensor has quit entirely and either cooling it down (canned air propellant) or swapping it with a spare fixed the problem immediately.

I’d like to switch to a hall setup for the crank trigger since i think that might be more reliable and maybe also go to a COP setup after that.

Jamie, it’s been forever since you helped me initially set up MS and it’s been great - I hope you’re doing well! Do you have any sources for a crank trigger wheel with magnets? I can’t seem to find any and would prefer buying vs fabbing that part. Also, are there any smart coils you recommend as most reliable, especially when they’re installed on the exhaust side of the heads?

Thanks!