MS Wiring

[Josh]

Just drawing out the schematic for my MS wiring and I have a couple questions:

Why is the main power feed fused if all the individual circuits are fused? Seems redundant to me.

Has anyone done a MS controlled cooling fan circuit? I have one designed right now but I would like to see someone else's take on it.


Thanks in advance!

[rdarlington]

Just drawing out the schematic for my MS wiring and I have a couple questions:

Why is the main power feed fused if all the individual circuits are fused? Seems redundant to me.

Has anyone done a MS controlled cooling fan circuit? I have one designed right now but I would like to see someone else's take on it.


Thanks in advance!

Without looking at the diagram, I'm going to take a stab at this.

Either the fuse is close to the battery to prevent shorts between the fuse/relay box and the battery from starting a fire. I do this with lines I run for ham radio. If my fuse at my radio and my power line shorts where it passes through the firewall, it will start a fire. Fuse at the battery and it immediately (hopefully!) disconnects the power line.

Or it's there so that if by some chance you draw a total current that exceeds the current capacity of the battery cables, then you don't start a fire.

For instance, in your house you might have twenty 15 amp circuits branching out from your fuse panel with a 200 amp breaker in it. If you had a space heater plugged into each branch circuit you would not trip any of the 15 amp fuses, but you would trip the main breaker because you'd be pushing 300 amps of current.

-Bob

[AdmiralSenn]

Based on this diagram:

http://www.megamanual.com/ms2/V3_ext_wire.gif

It's as Bob said. If you follow the path from the battery to the main relay, you have one 20A fuse for the feed to the relays, and then it splits repeatedly and each split has its own fuse if it has potential to draw or sink enough power to damage itself or its wiring.

This also has a nice side benefit of making fault tracing MUCH easier. I was blowing injector fuses on my first harness and I likely would have spent much longer finding the problem if they'd been blowing the main fuse instead.

As far as the cooling circuit, I haven't seen one for the DMC offhand, or if I have I forgot. I was 100% okay with using Dave McKeen's solid state fan controller system and the factory wiring - I figure if there's already a harness run for something and a nice relay setup for it and everything, why not keep that design as long as it's up to snuff? For the same reason I used his fuel pump relay and didn't have MS control the fuel pump. I also wanted to save as many outputs from the MS system as I could for future expansion. Of course that's me, your car is your own etc etc infinitum ad nauseum.

Are you using the relay board for your fan circuit?

[Spittybug]

Has anyone done a MS controlled cooling fan circuit? I have one designed right now but I would like to see someone else's take on it.


While I too have Dave M.'s cooling fan modules, I do have MS configured to sound a really annoying buzzer should my coolant temp exceed a set temperature. I didn't have the need to make MS the primary controller of such, but I do like having the redundancy just in case.

That same buzzer can be configured to sound with many different events. This can be helpful when doing your on-street tuning. For example, I used it to beep at me when my AFR exceeded a target. This would allow me to quickly gauge where I was (RPM and load) and adjust my tables accordingly. You can set it to sound when your AE kicks in too. Sometimes the audible warning is better than trying to catch it on the TS display while you are driving.

[Josh]

Without looking at the diagram, I'm going to take a stab at this.

Either the fuse is close to the battery to prevent shorts between the fuse/relay box and the battery from starting a fire. I do this with lines I run for ham radio. If my fuse at my radio and my power line shorts where it passes through the firewall, it will start a fire. Fuse at the battery and it immediately (hopefully!) disconnects the power line.

Or it's there so that if by some chance you draw a total current that exceeds the current capacity of the battery cables, then you don't start a fire.

For instance, in your house you might have twenty 15 amp circuits branching out from your fuse panel with a 200 amp breaker in it. If you had a space heater plugged into each branch circuit you would not trip any of the 15 amp fuses, but you would trip the main breaker because you'd be pushing 300 amps of current.

-Bob

Well your house breaker panel convinced me. Good analogy!


Based on this diagram:

http://www.megamanual.com/ms2/V3_ext_wire.gif

It's as Bob said. If you follow the path from the battery to the main relay, you have one 20A fuse for the feed to the relays, and then it splits repeatedly and each split has its own fuse if it has potential to draw or sink enough power to damage itself or its wiring.

This also has a nice side benefit of making fault tracing MUCH easier. I was blowing injector fuses on my first harness and I likely would have spent much longer finding the problem if they'd been blowing the main fuse instead.

As far as the cooling circuit, I haven't seen one for the DMC offhand, or if I have I forgot. I was 100% okay with using Dave McKeen's solid state fan controller system and the factory wiring - I figure if there's already a harness run for something and a nice relay setup for it and everything, why not keep that design as long as it's up to snuff? For the same reason I used his fuel pump relay and didn't have MS control the fuel pump. I also wanted to save as many outputs from the MS system as I could for future expansion. Of course that's me, your car is your own etc etc infinitum ad nauseum.

Are you using the relay board for your fan circuit?

I am pretty determined on eliminating the otterstat, so the fan will have to be controlled with MS. Same goes for the RPM relay. I am much more side cutter happy though. The engine harness is getting redone and I am eliminating quite a few circuits from the fuse/relay area. Just trying to simplify things as much as possible, which will mean some troubleshooting when I get everything running I guarantee!

I originally planned on using the relay box. But after pricing it out with a cord, I was kind of turned off to the whole idea. Also, I have the cooling fan circuit and and EDIS module, so two new circuits would need to be created anyway, making the relay box a moot point. So I am wiring the relays and fuses from scratch.


While I too have Dave M.'s cooling fan modules, I do have MS configured to sound a really annoying buzzer should my coolant temp exceed a set temperature. I didn't have the need to make MS the primary controller of such, but I do like having the redundancy just in case.

That same buzzer can be configured to sound with many different events. This can be helpful when doing your on-street tuning. For example, I used it to beep at me when my AFR exceeded a target. This would allow me to quickly gauge where I was (RPM and load) and adjust my tables accordingly. You can set it to sound when your AE kicks in too. Sometimes the audible warning is better than trying to catch it on the TS display while you are driving.


Interesting idea. I will still have an open output after the cooling fan control, gives me an idea about how it can be utilized. That would be nice for AFRs, since I do not want to bother with a permanent installation gauge. I will be having the laptop running shotgun for quite a while before I feel confident in my tune though!

[lazabby]

Josh,
Did you ever get MS set up to control the fans, thereby eliminating the otterstat?

[Exolis]

It's similar to the House analogy, I assume there's no fuse junction box for the rest of the things such as fuel pump. The purpose of fuses is to protect the harness, not the module(modules sometimes has their own internal fuses), but the design intent is to make sure if there is a short, the wire doesn't burn and catch on fire.

[Josh]

Josh,
Did you ever get MS set up to control the fans, thereby eliminating the otterstat?

Yes I did. I have a four wire IAC so I used the Fidle circuit to trigger the fan relay. I have it programmed to start the fans at 205F and shut them off at 195F. Attached is a schematic of the circuit. If you run it off the IAC1 or 2 outputs you can make use of the positive trigger and eliminate the polarity changing relay.

Sorry I missed this thread, just stumbled upon it today!

Edit: I am using aftermarket fans that consume 8A each. the 20A breaker is sized appropriately. If you are using the stock fans put in a larger breaker and size the wiring appropriately. I highly reccomend replacing the crappy stock fans, they suck up a whole lot of current and dont move much air. DPI and DMCNW have some excellent replacements.