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Potential Bulk Buy for FreeEMS first edition PCB 
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LQFP144 - On Top Of The Game

Joined: Sun Jul 13, 2008 2:58 pm
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Location: South Wales, UK
8InchesFlacid wrote:
, why are you taking out that wonderful computer of theirs?


The same reasons as everyone else on this forum, I like to tweak and I have got to the point where I can go no further without a standalone ECU I can tune myself.
The OEM ECU is perfect for the original spec engine it is designed to last decades, start first time every time and be as dependable as any high quality electronic device ever can be. but that is not enough for me, I want more, maybe I'm just greedy!

I fully understand what total flexibility of a modular design can bring in terms of new interest and mass utilisation across many platfroms. what I am really concerned about is building in weak links.
For example my ECU's PCB is conformaly coated at some time during the design cycle they thought that there was the possibility of moisture collecting on the PCB this may cause early life failure. how would you go about ensuring any stacking connectors were just as protected?

As far as having FreeEMS in its stable incarnation as part of your daily driver, why not as long as some of the lessons learned by Automotive industry have been taken into account, there should be no reason why i can't walk out to the car at 7am every morning and expect it to do everything the OEM ECU did, and on the weekend or at track days it can go that little further.
Hell how long have carbs been around for?? what we are talking about is mixing fuel and air and firing the plugs at the right time.

For me the critical points I am considering when designing my Bosch replacement FreeEMS are:
The main connector has to be something suited to the task either Ampseal, MIL spec or OEM.
The engine harness should be suited to the grounding system employed on the ECU. or easily adaptable to become suitable.
The parts used should spec'd correctly i.e. Automotive grade. with nothing getting close to its maximum capability.
The board should be conformaly coated to prevent moisture ingress.
The Case should also be sealed to IP66 or better if its in the engine bay or IP64 in the cabin.
Leaded solder to be used if you want perfect solder joints likely to last 20 years.
Lots of LED indicators to assist debug.
As many critical systems on the main board as possible.

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Mon Sep 29, 2008 12:06 am
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davebmw wrote:
there should be no reason why i can't walk out to the car at 7am every morning and expect it to do everything the OEM ECU did

As much as I agree with most everything you said, I think MS has conclusively proven that the hardware durability aspect of the system is probably of the least concern in reality.

People have all sorts of issues with MS systems, but the one thing they virtually never have issues with is : db37 connector and DIP40 sockets (many of which are yucky dual wiper type)

Heaps of people have daily driven their MS systems for many many miles and starts without issue.

The OEMs want the car to NOT come back AT ALL, whereas we only want it to probably not give us headaches. For the OEM it means a warranty cost and service centre with techies diagnosing and repairing and new parts etc = big dollars for a single failure. For one of us, it means cracking out a meter and a screw driver and sorting it out in an hour or two. Very different ball games.

Anyway, I'm not trying to stop you doing it right, I'm just sticking up for doing it "wrong" so that people don't get put off the basic way and we don't lose testers :-)

Fred.

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Mon Sep 29, 2008 12:27 am
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I seem to recall conformal coating is typical used to help prevent moisture from soaking in over time. Small amounts of moisture get absorbed by the PCB changing it's RF / breakdown properties, ect. The coating helps keep that kind of moisture out. It's not really intended for a drop of water, or such protection. The ECU case should have the ability to breath and drain for protection against those bits.

Right now all power bits do not traverse the TA connector scheme. So we aren't at risk of immediate failure there. As for long term failure relative to the connector, they will likely be tin coated, if so use the lub like the tyco commandments tell you to, or use gold plated. Either approach should make those connectors easily work for 5+ years with out long term issues arising. The nickel from the tin coating is the major issue. Over time it likes to do funny things. Mostly crystallization issues, that can cause funky issues with resistance, ect in the connection. However if you have a tendency to move that connector once in a while, that mechanical motion will prevent many of those issues.

I totally agree that less connectors are better. That's why I'm going straight harness connectors, no PCB edge connector at all. I just think the base version needs to be flexible enough that folks can figure out the vehicle wiring harness, on a prototype. Once they have it working that way, and understand the harness, they can do custom spin for a specific application.


Mon Sep 29, 2008 10:23 am
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