Megasquirt MS3X > 3.6 > 88 Carrera wiring queries

[billjam]

I am in the final stages of drawing up my wiring diagram for Megasquirt MS3X on a 3.6 engine going into my '88 Carrera and I have a few queries that I haven’t been able to figure out. Naturally, I have raised these on the MS forum, but there is next to no traffic there on MS3X issues so I thought I’d come back home to Pelican and try my luck.

Tacho Wiring
Can anyone clarify how they wired up their tacho to MS3X?

5V Sensor Supply
I have three sensors requiring 5V power - cam position, ignition timing and TPS.
Can I use the main board DB37 pin 26 to supply all three?

O2 Sensors & LC-1
Pin 23 on main board DB37 connector is for O2 sensor. Where would I connect a second O2 sensor input?

Grounds
I am planning to join the grounds from both DB37 connectors and run one fat (2.8mm2) wire from each connector to the main engine ground. However, I remember reading somewhere that all 0.5mm ground wires from each connector should be run all the way to the main engine ground, but this starts to get a bit messy when there is something like sixteen wires all fighting for space at this point.
What is the problem with joining the small grounds and running one main wire from each DB37 connector (as in my wiring diagram)? Please tell me it will be OK!

I have attached a copy of my wiring diagram but the detail is too fuzzy to see in a jpeg file. It’s not quite final yet, but I am happy to email a clear PDF version to anyone who is interested to review and comment on it. (Click on my name for email.) The yellow items are OE parts. Quite happy to get some feedback from others who have already done it.

[sjf911]

MS3X adds a lot of complexity to the MS experience. The wiring is tremendously more complicated than MS1/MS2 with the addition of cam sensing and sequential ignition/injection not to mention all of the additional input/output ports. I ended up rewiring the entire engine bay using a RTMR fuse/relay panel and a main power circuit breaker. I tried to anticipate future expansions with the wiring such as electric boost control, direct control of water injection, addition of a MAF sensor, spare sensors, A/C control, etc, and pre-wire those locations. I also added a 2 faraday line conditioner. Since my original install of MS3X I have added a blow-through MAF, pre-IC IAT sensor, methanol flow sensor, and rewired my A/C for idle-up control and WOT interrupt. Since I had prewired for these, it was relatively easy.

MS3X has a number of flexible input/outputs which are already pre-named such as EGO2, TACHO, etc.. I am using the TACHO output from the MS3X card to drive my tach without issues.

There are at least 4 ports that can be used for EGO2 input between the main board and MS3X and then you can add as many as you want with a CAN setup.

The 5V supply appears to have enough output to handle all of the sensors without difficulty. I found the TPS signal to be relatively unreliable for setting idle control so I am using the OEM idle switch on the throttle body to signal idle and switch ignition/injection tables. This made a big difference in idle quality for me.

Ideally, you would like to have all of the grounds run back to the same spot but this is difficult with the long runs we see. I typically link them in bundles of three going from 3x 20g to 1x 14g so I have 4-5 14g ground wires. Even then, you end up with a very fat harness.

[billjam]

Steve,
How do you find the Safeguard knock sensor unit?
I have been trying to find a system that works and doesn't have heaps of negative feedback on forums.
I am fitting the standard 964 knock sensors but not connecting them until I can find a system that works. DIY AutoTune are suggesting they might have something available soon, so I was going to wait and see what they come up with.
Thanks for your comments above. I also intend to include a bunch of extra wires in the harness for future options, including the knock sensors.

[sjf911]

Originally Posted by billjam

Steve,
How do you find the Safeguard knock sensor unit?
I have been trying to find a system that works and doesn't have heaps of negative feedback on forums.
I am fitting the standard 964 knock sensors but not connecting them until I can find a system that works. DIY AutoTune are suggesting they might have something available soon, so I was going to wait and see what they come up with.
Thanks for your comments above. I also intend to include a bunch of extra wires in the harness for future options, including the knock sensors.

I just installed the Interceptor so I haven't had much time to log with it. I wired it in such a way that it will be easy to revert to the original wiring if it doesn't work out.

[billjam]

Bump

[sjf911]

The wiring diagram looks very nice. One thing, you have 3 wire coils shown which are usually "dumb" coils and will need some sort of ignitor wired between them and the MS3X. MS3X is designed to run logic "smart" coils specifically like the LSx types which are usually 4 or more wires.
Pin 22 on MS3X is pre-named for a second O2 sensor. Here is a TunerStudio screen shot of how you would set it up from the pull down menu:



Normal EGO is MS3 #23, EGO2 (ADC 12) is MS3X #22 and then you just set which injectors go to which O2 sensor. You do have to edit the project properties to set what specific type of WB controller you are using and their calibration.

By the way, what program did you use to draw your wiring diagram?

[billjam]

Thanks for comments Steve.

I have already re-jigged the wiring diagram to suit the 4 wire coils. The coils actually do have 4 wires but I thought I could get away with only using three. The coils test fire OK using three wires and I initially was told that the 4th wire was for an error/misfire signal back to the Toyota ECU. There is still some doubt about this and I am inquiring further, but in the meantime, I'm going to run those wires anyway and then figure out what to do with them later.
The Toyota coil terminals are:
1 - coil +12V
2 - diagnostic to ECU (edited)
3 - 5V signal from ECU (edited)
4 - coil ground

At this stage, I don't even have my MS3X unit (shipped last week ) and the engine is many months off being installed in the car. My main activity at present is making up the engine and ECU harnesses.
The wiring diagram is done in MS Visio. I can email a clear PDF version if you are interested.

[brads911sc]

I think MS3 is still very new which is why there is so few using it on here. I have MS 2, V3.57. Are you using the MS Relay board? It is a nice touch and makes alot of the wiring neater/ easier. Why did you select MS3? What features are you using that arent in MS2? I chose MS 2 because there is alot more information out there and Im not enough of a Guru to be a pioneer. Looks great btw!

[billjam]

Brad,
MS3X was the only version that supported COPs (without wasted spark) and sequential injection.
Neither are absolutely essential, but I decided that if I was going to jump into this, it may as well be straight into the deep end! Believe me, it's been quite a learning curve so far, and I haven't even got started on setting up the ECU yet!

I'm not using a relay board. I did consider it, but in the end decided against it.

What you say about pioneering seems true to some extent. I have found it difficult getting feedback here and on the MS forms for MS3X. I thought the MS forums would be quite helpful, but throwing in the Porsche factor probably doesn't help.

[sjf911]

The coils must use a shared ground for the igniter and the logic signal if you can fire them off of only 3 wires. That would imply that the fourth is, in fact, a status monitor.
MS3 is really still in the development phase with the software far from finalized. This means there are still bugs to work out and a lot of additional capabilities to be written into the code. A lot of the current development is toward VVT and other technologies foreign to the air-cooled Porsches. To top it off, the code is way ahead of the documentation so there is a fair amount of the blind leading the blind going on.
As to the relay board, I found it did simplify the initial wiring but it really wasn't very robust or secure especially in the harsh environment of the Porsche engine bay. I was eager to rip it out when I converted to MS3 and I am now very happy with my Bussmann RTMR panel.
As far as your wiring harness, it looks like you have it pretty well layed out. I would encourage you to consider using the DIYautotune harnesses. They do a nice job and for a lot less money than you can build one on your own, at least here in the states. I built my own MS3X harness before DIY had any available and it easily cost me 3X what they charge not to mention the time required to source the various wire colors/sizes and then build the stupid thing.

[billjam]

I have just come back from a lunchtime visit to local Toyota dealer where we confirmed that the 4th wire is in fact a diagnostic signal back to ECU and that coil and signal use same ground. Signal voltage is specified as 4.5V or more.

I am using the harness wiring kit from DIY rather than their complete harness. I didn't like the idea of being stuck with all their pin connections and I wanted to use spare wires for other services. It definitely is a pain trying to come up with suitable colours and sizes for all the additional services though. No one supplier here has everything that I need, and of course they are scattered all over town.

[roblav]

Bill - I posted a note on the MS3 board on a thread of yours. Didn't realize it was you. That is QUITE the wiring diagram.

[billjam]

Thanks. I can't believe it is a year and a half since I started this thread! Engine is sitting in my garage under a cover as I just don't have time to finish off the engine swap, but it will happen in 2013 (new year resolution #1).
The wiring diagram has grown a few more legs since I posted above. It now includes knock sensor wiring and more detail for the relay panel. I'm quite happy to share the original Visio files or a PDF version by email if anyone is interested. Just send me your email address.

[Jaskas]

My friend in Finland built me a total plug and play MS3 Ecu for my 993 3.6 engine. It uses all stock sensors and wiring. You can swap between stock ECU and MS3 Ecu in seconds.

A pic of the ECU:

Ecu lid open


Dyno run with the MS ECU:
Dyno session 031112 - YouTube


There is more discussion of this at Rennlist under 993 section...
100% plug'n'play aftermarket ECU for our cars for under $1000 - Rennlist Discussion Forums

[Tippy]

Bill -

Never saw your thread until now. I hope for you the best to tackle that beast of a wiring diagram. That is not for the faint of heart. I should print that out on a large plotter and laminate for a cool wall poster. HEHE

Seriously though, good luck. Didn't realize you were doing this on a Carrera 3.2 with a 3.6 from your older posts on my frantic thread.

Jaskas -

That is way cool! Your friend could really capitalize on that. Especially for boosted applications where fully programmable EFI is a must.