MSefi.com read only forum (Jan.15,2018)

So i just picked up megasquirt to do my efi to carb conversion. So what i was wondering is there any differnt/after marked relay boards that any one is useing. Or is it easyer to just megasquirt realy board.
thanks john

It would probably be easier for a beginner to use the relay board. I used one on my first MS project, but I migrated away from it because it involves just that many more mechanical connections to keep track of. Meaning that my MS is wired directly to the engine. (ie. sensors, injectors, ignition etc.)

In place of the required relays (and fuses) I used this item, which worked out very well with my setup.

http://www.summitracing.com/parts/ARC-1440/

I am not intending to discourage you though. The relay board will probably work very well for you. Just offering up my perspective on things.

Ken

I agree with Ken. The relay board introduces lots of extra connections within the loom - and connections are the things that fail first. There are various relay bases available including ones which clip together and with mounting brackets. These could be mounted close to the MS within the car rather than engine bay. Good relays have a long life so don't need to be very accessible.

Ok well I am trying to stay away from having alot of wires going to the engine bay.
Trying to keep in as easy as posable the set up in going into a turbo drag car.

turbojohnnyb wrote:Ok well I am trying to stay away from having alot of wires going to the engine bay.
Trying to keep in as easy as posable the set up in going into a turbo drag car.

It isn't going to make any difference in the number of wires going to the engine bay, whether you use the MS relay board or not. You will still have the same number of sensors, injectors, coils etc. that need to be connected to the MS regardless of where it is mounted.

The only point that I was trying to make, was that for every mechanical connection you make you create an equal number of possible failure points. Which is why I no longer use my relay board. I hard wire everything (soldered, shrink wrapped, etc).

Of course that could be because, according to Freud, I may be anal retentive!

Ken

If u want to hard wire everything how do I go about doing that.

turbojohnnyb wrote:If u want to hard wire everything how do I go about doing that.

You'll have to make a big enough hole in the bulkhead to get the loom through, and use a grommet to seal it. 1.5inch or so is usually enough - or to suit an easily available grommet.

turbojohnnyb wrote:If u want to hard wire everything how do I go about doing that.

That is more a matter of personal preference, and applicability to your setup, than anything else. There are a number of hardware sources out there, such as DIY AutoTune who offers a variety of harnesses, both pre-built and diy.

The basic external wiring of sensors, injectors, relays, etc. are covered quite well in the MegaManual and this forum.

Ken

There is a really good book out there called Performance Fuel Injection. It has some really good information in it on building your own harnesses. You can find it here: http://www.DIYAutoTune.com/catalog/perf ... p-436.html In fact the guys over there at DIYAutoTune, literally wrote the book!

There are several approaches. In my years of making harnesses, the approach that makes the simplest layout, build, and cleanest harnesses is to work backwarrds towards the ECU. Start in the engine bay with the furthest sensor away, and work in towards the ECU. If your using heat shrink, this is the only way.

Everything takes thought and planning. When I do a build, I will take a bunch of pictures, measurements, and drawings. I like to use graph paper to draw out a basic layout. I rarely follow the OE path, but it can give you some ideas.

And these days the options for simply plugging into the stock harness are plentiful.

The hardest part usually is wiring up the power grid. While I have used many of the MS relayboxes, they are not only limiting, but I can tell you from dealing with the cars afterwards they are a much more common failure point than a properly custom done setup.

I'm more in favor of relays (or some type of mid-harness terminal strip) for a street car or for an EFI or MS beginner. I have zero experience with the MS relay board but have a ton of relay board expereince from my last job. Picture a relay board about 11x17 with over 20 relays, mounted in custom-built utility trucks, and you get the idea.

My perspective:
A 1-piece harness is great when it's a standalone system, everything works well, and no diagnostics or repair are ever required (and maybe that'll be the case with a drag-only car). A street car though, with a bunch of existing electrical loads and OEM harnessing, ought to have some way to integrate yet isolate the MS system from teh OEM stuff. A properly-installed relay panel allows you to add items without overloading any original circuits and also allows easier 1-man troubleshooting. With a full-length harness some diagnostics might require a continuity check from sensor to ECM connector -- and the firewall might be in your way or you might need really long arms or meter cables.

There's no right or wrong answer though.

My approach is to build an new engine only harness and fit a connector from that to the main original loom. The connections through that are usually just things like the switching signal for the main relay from the ignition switch, and feeds to the tach, pump, etc. The high current feed new, and direct from the battery. I have EDIS, and that has its own feed direct from the battery with an extra relay switched from the ignition circuit.