When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Yes, this is a good thing to do in the longrun to be fair, my spals almost kill the car when they come on because their draw is too much and tune is too little, and aside from thickening the wiring for the fans I've kept the stock relays and controls.
It is important to bare in mind that better fans generally means more amperage draw especially without a soft start feature. fd rx7 alt is in my future. Boy do they move some air and cool **** down.
Can a relay be connected to the ckt so that when the sensor turns on the fans. It activates a relay that is powered directly from thw battery with a large thick wire? Eliminating much of the draw on the alternator.???
Can a relay be connected to the ckt so that when the sensor turns on the fans. It activates a relay that is powered directly from thw battery with a large thick wire? Eliminating much of the draw on the alternator.???
my first thought to this is yes you can add a coolant sensor and relay to switch on the fans separately, but logistically the draw on the alternator is the same given its there to support the battery and keep it charged. Where the power is pulled from and whether or not its from a thicker wire off the battery wont change how much work the alternator has to do to keep up with something drawing amperage. Running beefier wires and relays is more of a longevity and safety action, so as not to burn up wires or stock relays from something that is pulling more power than stock.
A big part of the reason for running larger or additional cables was because it puts significantly less droop in the engine due to alternator drag when you have the ability to draw more from the battery to cushion the voltage drop.
I can't imagine running two spal fans when one 19' spal fan is enough, and I had air conditioning (on a caged track car (Florida)).
Consider an inline delay relay between one fan's relay to stagger the draw by 2 or 3 seconds (I hope you don't have both fans on one relay).
A big part of the reason for running larger or additional cables was because it puts significantly less droop in the engine due to alternator drag when you have the ability to draw more from the battery to cushion the voltage drop.
I can't imagine running two spal fans when one 19' spal fan is enough, and I had air conditioning (on a caged track car (Florida)).
Consider an inline delay relay between one fan's relay to stagger the draw by 2 or 3 seconds (I hope you don't have both fans on one relay).
i have two 11” spals iirc, the medium*???* model fm used to use in one of their kits long ago. I still have ac and generally an oem setup regarding fans and their control, ac fan for ac cooling fan for cooling, both on with ac, or both on above 210f - their respective stock relays for either.
Writing this out did help me realize its just one fan turning on that has such a drastic effect.
the delay relay would help, along with bigger wires ( i hadnt known it could in practice help cushion the drop)
mainly I imagine a better tune(r) or something more helpful than speedunios infinite array of features and items everyone knows exists 0-0
Even if just running one fan, delaying the fan by 2 or 3 seconds after the A/C clutch engages would allow recovery from the droop before the fan draw begins and adds more. Mine did.
I also liked idling around 1100 so the a/c was cooler, and the alternator generated more power. Helpful when a/c was on, blower was high, radiator fans were running, headlights were on, wipers were on, and you were trying to roll down the sticking window for something, lol.
Last edited by sixshooter; Oct 11, 2025 at 05:39 PM.
Even if just running one fan, delaying the fan by 2 or 3 seconds after the A/C clutch engages would allow recovery from the droop before the fan draw begins and adds more. Mine did.
I also liked idling around 1100 so the a/c was cooler, and the alternator generated more power. Helpful when a/c was on, blower was high, radiator fans were running, headlights were on, wipers were on, and you were trying to roll down the sticking window for something, lol.
I've never thought of running a larger 12v positive cable to the battery but if that fixed the problems I have on my car with how hard it tries to drag down my idle whenever I do something like roll down the windows or turn the headlights on I might have to consider trying it...
The only way I could run a larger Spal fan was to use a PWM controller. The one I'm using is from a V6 ford fusion, mercury milan or c6 vette. Its best to get one from a yard with the plug.
The only way I could run a larger Spal fan was to use a PWM controller. The one I'm using is from a V6 ford fusion, mercury milan or c6 vette. Its best to get one from a yard with the plug.
I imagine if it were a PWM fan that had a built in controller it would be possible. I used a regular brushed DC fan with the external controller, and it works very well. It has a soft start and is programed for a different speed at specific temps with the ms3 plug&play.
Originally Posted by Riley8425
Pretty sure with an MS3 Pro you can also run PWM natively to a Spal fan?
I just fitted the factory undertray and it's working great. One thing to keep in mind is to seal any gaps between the undertray and radiator, as well as other potential air bypass areas. Air tends to follow the path of least resistance, so think like a molecule and identify where it might escape instead of flowing through the radiator. Seal those gaps to optimize airflow
I imagine if it were a PWM fan that had a built in controller it would be possible. I used a regular brushed DC fan with the external controller, and it works very well. It has a soft start and is programed for a different speed at specific temps with the ms3 plug&play.
ok I figured out the flex fuel sensor issue. I moved it's switched 12v to the METER 15A fuse box with and add a fuse and it seemed to work perfectly fine. I decided to go one step further and wire in a relay tho since the ethanol % is obviously very important to getting accurate fueling. Ran some 16 gauge wires from the battery with a 5v inline fuse on the power. I ran it down behind the passenger seat and under the door sill on that side then mounted the relay right under the old AC condenser? box. This should allow it to not drop below 10.5v and fault just like the common fuel pump upgrade relays do.
Next I'm going to run a 10 gauge wire with a 30amp inline fuse from the alternator battery post over to the fan relay, just need to nail down which wire this weekend. Should help with the fan spool up idle drooping (hopefully). Then maybe do the "big 3" or bigger alternator or even battery at that point if its not fixed.
Ok so I've gone down a rabbit hole on Mazdaspeed fan relays and holy crap is it confusing with the switched ground relay, dual speed fans. I've been going over the fan relay diagram for a couple hours now and think I have a plan. If anyone happens to be a electrical engineer please speak up before I ruin my car lol.
Here's the plan:
I have no AC
I have two fans, I want in parallel, single speed.
I want to reduce the idle drop when the fans kick on
Similar relay as my flex fuel sensor, except its a 4 pin. All wire will be 12 gauge (except ECU stock one)
Pin 30 will go to my alternator battery post.
Pin 85 will go to a chassis ground
Pin 86 will get the stock RED/YLW wire for signal from the old Fan Relay 1. I plan on tapping into this from the pass. side fuse box.
Pin 87 will go to both fan power wires
I will also change the ground for the fan motors to chassis ground as well (I think they're currently ground via the stock relays) (maybe this needs battery ground?)
Well I figured I knew enough to sort of just send it and test it out. I found my fans were currently on the yellow wire, which is energized in the relay from the red/yellow from the ECU. I found a forum post also confirming this to be the low speed trigger.
I wired in everything in a test config and went to Tuner Studio's Testmode and checked and it worked! I then wired it all in permanently. I now have a single relay for the fans and left all 4 previous fan related relays, disconnected. You cannot do this setup if you still have AC.
That Fan Relay 1 was also a massive PITA to find! Its under the black cover on this metal brace and theres a sneaky 10mm nut on the fender as well.
I mounted the relay where the old emissions system used to be and actually used the switched 12v from there after confirming with the multimeter it functioned correctly.
Each fan motor is grounded separately as well.
After a few hours of fun, I tested it on a drive and the fans DID NOT COME ON! I popped the hood and found the 30amp fuse had blown. The cumulative fan amperage pull on startup was 29.5 so that was too little margin. I threw a 40amp in there and everything has been working great! The idle still droops but it didn't seem to be as harsh or as low of a drop. I also messed with the idle up fan delay in TS to 500ms, I will play with this more. Pretty happy with the result. I'm still seeing my flex sensor fault once every 10 or so starts so I think battery and alternator upgrade are going to be a must. That FM antigravity battery looks incredible, but I don't think I can stomach the price!
Nice electrical work man! Doing all that work with a multimeter is time consuming and so rewarding haha. Glad it all amounted to a tangible difference.
Holy hell, yeah the FM Antigrav kit is pretty 'spensive. I ran an AntiGravity ATX-12-HD on my NA, which I then threw into my current car, with great results. Cold starts in both cars at 30*F weren't an issue. That battery might be a downgrade in cranking amps compared to what you have now, though. The ATX-20 would probably work great for you. I think they're still under $300.
Currently running a Noco NLP20 in my car, which is a couple pounds heavier (a whopping 6lb total) and claims to have another 120CA over the AXT-12-HD. Been working well in my NC which I assume has an overall higher amperage draw, but I've only had it for a month and a half so can't comment on longevity.
You're the man Z!! I just bought the ATX-20HD from Antigravity since its 15% off for Black Friday. I really appreciate the real-world experience with them. I finally got a combo oil pressure/temp sensor, RX7 alternator and oil cooler supplies. My goal is to get this thing ready to hit the track next Spring with a few things yet to do. I will likely still need to insulate the battery since it gets quite cold here in Colorado.
I'm still seeing idle drop when the fans kick on. Its sliiiiightly better but maybe the new alternator and a lithium battery capable of faster voltage discharge will help.
A friend and I run the Antigravities on a total of 4 cars, one of which sits outside year round and sees well below freezing temps. The outside car sometimes cranks a little slower after it sits for a week in 20F weather, but always starts. In my car that is garaged, I don't have an issue, and I've left it outside once in a while to test, and have started it without trouble in the 20s. The battery does drop from 13v to about 12.4 or 12.6 in the cold while resting, but again, hasn't been an issue. I believe mine is the ATX-20-HD, and my friend is running that and an older one I don't remember the model.
Sorry if I'm re-iterating things you know, but with the idle drop, you can try giving the controller a head-start by increasing the fan on delay. Some fans, like the FM non-PWM spals and the stock Mazdaspeeds, need up to 500ms of delay. I also tend to give the controller some help with the voltage offsets to counteract the initial hit + have the ignition control do it's thing. Of course that's assuming your voltage isn't dropping to oblivion when the fan starts, which I've also seen with some FM fans (down to the 11s!).
Thanks a ton for that input!! I think I'll be just find, especially since I bought one of their battery tenders and only drive it 1-2 days a month over winter when its exceptionally nice out.
oh dang, I was only running 200ms of delay and thought that was quite a bit. I just bumped it up to 400 for the next drive and will keep ya posted, good shout!
Time sure does fly and I haven't gotten much done lately with the car.
I took the plunge on the AG battery, man it is LIGHT!! Because of the obvious size difference, I ended up designing and printing a new battery tray that raises it up to utilize the same metal bracing bar. With it being skinnier too, I just made a couple little blocks and glued them to the bar. I found some insulation off amazon as well that is sticky on one side so I threw that on there just to maybe help with it being sensitive to temperature.
In addition to that, I bought a 130amp alternator from eBay. With the new relay attached to the alternator post, the increase in fan idle up delay and the Lithium battery, I'm happy to report the idle droop is so much better! The only downside is this alternator whines like crazy. I loosened the belt quite a bit and it quieted down but its nowhere near as quiet as the stock one.
Spall Fans
0
