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Old 06-05-2015, 01:39 PM   #1
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Default (Help)Looking for a delay relay for fan circuit or other solution

The new giant Spal fan and shrouding do nicely at keeping the engine cool on track and the A/C cool around town, but it really draws some amps. I get a little rpm drop when the fan comes on but if it comes on with the A/C compressor clutch my voltage can momentarily drop below 10v which is troublesome to the wideband and the megasquirt.

I would like to find a delay relay that would give the fan a 2 to 5 second delay so that all of the increased draw doesn't come at once. I have an MS1 so the IAC system is reactive instead of proactive and I've done all I could with it (bumped up idle speed, IAC closed value, and fiddled with the dashpot adder settings). I could also run a larger battery for more reserve amperage, but would prefer to just find a 12v circuit delay of some sort.

Google hasn't given me what I am searching for yet, so I thought I would ask the experts.
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Old 06-05-2015, 02:56 PM   #2
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Pics of your setup? Interested to see it...

For your question, here's a time delay relay I run on my miata, though for a different purpose: Time Delay Relay

Call this time delay relay relay 1.

For what you're wanting to do, if you add another relay (Relay 2) to invert the signal from the A/C Compressor, it could flip the signal coming from the A/C compressor, so that the relay is off when comp is on, and on when compressor is off.

Then use that so that when the comp turns on, the relay turns off, and the time delay kicks in for some number of seconds, then the time delay turns "off". It turning off would again be inverted if needed for your fans.

That's how you can do it with relays, no microcontroller or capaicitors or Inductors.

You could also do it by installing an inductor inline with the fan relay. Probably eaiser to install, but you'd have to do some calculations to size the right Injuctor size for the delay needed. If you wanna do it this way I can calculate what you'd need if you tell me the resistance of the coils on the relay you use for your fans.
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Old 06-05-2015, 02:59 PM   #3
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Also consider a soft-start fan controller, those are nice too though they cost a bit more than a couple relays or an inductor.

Also depending on what year miata you have, you can find larger alternators on newer miatas.
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Old 06-05-2015, 03:11 PM   #4
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It is ironic that I just threw a time-delay relay into the garbage a few days ago.

They are not cheap: S1DXM-A2C10M-DC12V Panasonic Industrial Automation Sales | 1110-2513-ND | DigiKey
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Old 06-05-2015, 03:39 PM   #5
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I'm trying to draw the two relay diagram in my head while driving and the ways I see it in my head aren't working correctly. Are we talking about a NC or NO relay for relay #2?

Would someone be willing to draw the psychology major a diagram so he gets it right?
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Old 08-24-2015, 01:43 PM   #6
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I don't mean to revive this thread, but it might be relevant.

I've been having some difficulty trying to get the car to not stall from idle when the fans kick on. I'm using the FM big air kit with two spal fans (daily driven w/ ac condenser). The main fan is wired to the stock harness, and the A/C fan is in parallel off a relay.

I just ordered a relay delay module which would delay the A/C fan relay by about 5 seconds so it won't draw so much at the same time. While you're primarily concerned with the A/C clutch + fan engagement, perhaps delaying the fan with this might do the same trick as opposed to getting a specific relay.

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Relay Delay Module

Your dual cooling fan system works much better than the single OEM fan. But, doubling the relay load tends to overload the OEM relay (which is designed to run one fan only) so you most likely use one of our dual relay fan conversion harnesses. But, in certain applications, turning on both fans at once causes a “sag” in the electrical system, leading to engine stumble, shutoff, or worse. These applications can be remedied by using our Relay Delay Module. This module is required when using two cooling fans on your GN. Attaches to one of the fan relays, this module will delay that fan for about 5 seconds, assuring a more linear startup load to the electrical system. Designed to attach to a fan relay only (not to the fan motor). Simple, two wire installation.


Specializing in automotive interconnect and wiring systems
I hope it works, I'll update if it does.
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Old 08-24-2015, 02:42 PM   #7
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Default (Help)Looking for a delay relay for fan circuit or other solution

That's just what I was looking for.
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Old 08-24-2015, 03:00 PM   #8
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didnt hornetball create some firmware that had idle up of sorts?

why not just man up and upgrade to ms2 for $50?


what's a delay going to do if the brain still has no idea you are going to turn on something with load? youre going to flip the switch, wait a moment, and then be back a square one when the system still has to react to the fan, after the delay and still draw tons of power and drop to 10v...

I'd rather upgrade to an 80A rx7 alternator (over your 60A) before doing this or an ecu with code that's already designed to handle voltage drops and load changes...
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Old 08-24-2015, 03:32 PM   #9
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Because I have a Brain built MS1 and it is all anyone should ever need.

How do I upgrade it for $50?

I didn't know there was a drop in 80a alternator from an RX7 to fit my na8. Any idea what years?
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Old 08-24-2015, 03:47 PM   #10
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a 91 turbo rx7 should be almost PNP.

the flanges are different, so you will need a different long bolt/nut and maybe a spacer of sorts. (look at pics, youll see)

connectors are same.



I've sold a few MS2 cpu's for $50. They used to be $90 retail, not sure what they are anymore.
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Old 08-24-2015, 06:16 PM   #11
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My '96 appears to have a 70 amp and a serpentine belt and the '91 rx7 turbo is a v-belt with 80 amps. That must be an upgrade for the 1.6 cars or something.

I'm running the lighter chromoly flywheel and a small battery, neither of which helps the issue when physical load and electrical draw are simultaneously suddenly increased. I've tuned it to where the engine doesn't ever die but staggered engagement would make it smoother.

I'd like a modern ECU but frankly, this works pretty effectively in most of the important ways. It idles quite well with and without the A/C except for the moment of engagement. Scott did a good job building it. And I am an awesome MS1 tuner, lol.
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Old 08-24-2015, 06:44 PM   #12
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I enjoy the speaking as though Scott and Brain are not one in the same.
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Old 08-24-2015, 08:40 PM   #13
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I think you want a FD alternator, serp belt and larger pulley for more idle volts?

https://www.miataturbo.net/general-m...16/#post618169

Please try it and let me know, so I can try FC alt on my 1.6
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Old 08-25-2015, 07:53 AM   #14
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Quote:
Originally Posted by sixshooter View Post
My '96 appears to have a 70 amp and a serpentine belt and the '91 rx7 turbo is a v-belt with 80 amps. That must be an upgrade for the 1.6 cars or something.

I'm running the lighter chromoly flywheel and a small battery, neither of which helps the issue when physical load and electrical draw are simultaneously suddenly increased. I've tuned it to where the engine doesn't ever die but staggered engagement would make it smoother.

I'd like a modern ECU but frankly, this works pretty effectively in most of the important ways. It idles quite well with and without the A/C except for the moment of engagement. Scott did a good job building it. And I am an awesome MS1 tuner, lol.

Ah, the FD is 100A.

With all that in mind, my best recommendation is a better ECU.
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Old 08-25-2015, 08:55 AM   #15
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Quote:
Originally Posted by psyber_0ptix View Post
I enjoy the speaking as though Scott and Brain are not one in the same.
Have you ever seen them together in the same place?


Quote:
Originally Posted by deezums View Post
I think you want a FD alternator, serp belt and larger pulley for more idle volts? Please try it and let me know, so I can try FC alt on my 1.6
I've already got a serpentine arrangement. Yes, the FD alt looks good for the na8 (70a up to 100a) and the FC looks like a fit for the na6 (60a up to 80a). The clocking, pulleys, and connectors look like a match for each.

Quote:
Originally Posted by Braineack View Post
With all that in mind, my best recommendation is a better ECU.
Agreed. And I will go that way soon. The dust is still settling from a mortgage refinance which involved a sizable cash outlay, so I'll likely wait a few months.
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Old 08-25-2015, 09:35 AM   #16
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Bought this for the same issue and solution but never got around to installing it. Maybe this time around.

DC 12V Delay Timer Relay Power on Time 0 60 Minute Solid Delay Socket H3Y 2 Base | eBay

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