Why is my miata running hot?
06-01-2018, 11:01 PM
#1
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Why is my miata running hot?
Hows it going guys. First time poster, long time lurker. (please move this if its in the wrong spot)
Alright so i have a turbo miata that runs hot (at least i think).Ive read and installed every known cooling mod besides blowing big money on a new radiator. Also the turbo is mounted, but not tuned so the car is still N/A. Ive heard people using the ebay rads on modest boost setups, so the fact that it cant handle 90whp worries me. I know 255 will kill a head gasket, but 225 still seems wicked warm. It has the following-
Ebay rad w/ slim fans
Begi reroute
Stock splash gaurd in place
New oem pressure radiator cap
New headgasket
Singular motorsport hood vents
180 degree stant thermostat in an inline housing about 6 inches from the back of the head
1 bottle of water wetter, and probably 70% water 30% coolant
Anything that touches coolant is new/doesn't lose coolant so i know its not a leak.
Fab9 core infront of the rad.
It runs at 215 with no ac and will eventually climb to 225 if i turn ac on. Ambient temp is 80-95 (texas). Temps are verified between ms2 and a standalone gauge. So am i missing something??? Ive seen boosted miatas with stock rads so what gives? Am i being too picky about my temps? Am i the only one actually paying attention to an accurate gauge and thats why im noticing the temps? Or is 225 totally fine for boosting? What are some of your temps? Please dont give me a time on a clock where your stock gauge reads, I need numbers to see if im screwed or just paranoid. Has anyone gotten theirs to run at sub 200s? or is that not possible without moving up north?
Alright so i have a turbo miata that runs hot (at least i think).Ive read and installed every known cooling mod besides blowing big money on a new radiator. Also the turbo is mounted, but not tuned so the car is still N/A. Ive heard people using the ebay rads on modest boost setups, so the fact that it cant handle 90whp worries me. I know 255 will kill a head gasket, but 225 still seems wicked warm. It has the following-
Ebay rad w/ slim fans
Begi reroute
Stock splash gaurd in place
New oem pressure radiator cap
New headgasket
Singular motorsport hood vents
180 degree stant thermostat in an inline housing about 6 inches from the back of the head
1 bottle of water wetter, and probably 70% water 30% coolant
Anything that touches coolant is new/doesn't lose coolant so i know its not a leak.
Fab9 core infront of the rad.
It runs at 215 with no ac and will eventually climb to 225 if i turn ac on. Ambient temp is 80-95 (texas). Temps are verified between ms2 and a standalone gauge. So am i missing something??? Ive seen boosted miatas with stock rads so what gives? Am i being too picky about my temps? Am i the only one actually paying attention to an accurate gauge and thats why im noticing the temps? Or is 225 totally fine for boosting? What are some of your temps? Please dont give me a time on a clock where your stock gauge reads, I need numbers to see if im screwed or just paranoid. Has anyone gotten theirs to run at sub 200s? or is that not possible without moving up north?
Last edited by noahbeale; 06-01-2018 at 11:13 PM.
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06-01-2018, 11:10 PM
#2
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Do you have the plastic under engine tray installed?
My miata runs:
No AC street 40-50mph at 185
With AC street 200
No AC highway 180ish
with AC highway 200-210
Race track i never seen it over 220, after 20 minutes of pounding on it.
I have Mishimoto radiator with stock fans
plastic sheets to box in the mouth opening so all air if forced into the radiator
Plastic under engine tray in place
singular hood vents.
my last 99 turbo miata was acting just like your car. had stock radiator, no engine under tray and no air guide.
With AC on the highway it would climb to 235, then i was forced to turn off the AC.
so you really must have the stock air guide, plastic engine under tray installed. and its best if you can box in all the air to go into the radiator, this includes closing up the sides and top.
My miata runs:
No AC street 40-50mph at 185
With AC street 200
No AC highway 180ish
with AC highway 200-210
Race track i never seen it over 220, after 20 minutes of pounding on it.
I have Mishimoto radiator with stock fans
plastic sheets to box in the mouth opening so all air if forced into the radiator
Plastic under engine tray in place
singular hood vents.
my last 99 turbo miata was acting just like your car. had stock radiator, no engine under tray and no air guide.
With AC on the highway it would climb to 235, then i was forced to turn off the AC.
so you really must have the stock air guide, plastic engine under tray installed. and its best if you can box in all the air to go into the radiator, this includes closing up the sides and top.
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06-01-2018, 11:49 PM
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Remove the intercooler, see what happens. The thermostat location is also most likely a factor. How does it warm up? It should peak at 180 before dipping cooler (thermostat opening, dumping radiator full of ambient water into engine), and oscillate back and forth until finally settling at 180.
That 6" piece of hose before the thermostat has to completely warm up with no flow through it before the thermostat opens. Meanwhile, your head is overheating. I'm a huge proponent of ditching that design for anything but that design.
You could compensate by drilling a ~3/16" hole in the thermostat, which would allow some flow past the thermostat, getting warm water to it sooner, therefore helping it regulate temps. But when I've done this, the first peak after warmup is slightly lower, and it oscillates longer before reaching a stable temp. So not a perfect solution in my mind.
That 6" piece of hose before the thermostat has to completely warm up with no flow through it before the thermostat opens. Meanwhile, your head is overheating. I'm a huge proponent of ditching that design for anything but that design.
You could compensate by drilling a ~3/16" hole in the thermostat, which would allow some flow past the thermostat, getting warm water to it sooner, therefore helping it regulate temps. But when I've done this, the first peak after warmup is slightly lower, and it oscillates longer before reaching a stable temp. So not a perfect solution in my mind.
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06-01-2018, 11:51 PM
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My Turbo 95 run around 200-210 in this Texas heat. I needed to clip off the little thermostat valve thing and drill out the hole to help increase flow a bit.
That's with an aluminum rad, FM fans set to 205 for the first one and 210 or 215 for the second. Hood vents, undertray and some ducting.
What do you have your fans set to? That kind of determines the upper temp limit when it's hot out. Thermostat will be fully open long before then.
That's with an aluminum rad, FM fans set to 205 for the first one and 210 or 215 for the second. Hood vents, undertray and some ducting.
What do you have your fans set to? That kind of determines the upper temp limit when it's hot out. Thermostat will be fully open long before then.
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06-02-2018, 12:48 AM
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Ill try taking out the ic to see if that helps. I agree about the stat location, but thats as close as i can get it without putting back into the head. Which i dont want to do because its a total pita to get back there if needed. Ill try to drill a hole to see if that can increase the response time of the stat. I have stock ebay slim fans which im sure arent ideal. The car is on ms2 so the fans are set to come on at 205 (i believe) for the driver side, and the passenger side only comes on with the ac. Is there a way to change the fan engagement temp in ms? Also can i independently set separate temps for both fans?
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06-02-2018, 08:22 AM
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Ive refilled it with coolant after i shut it off over and over until it was full, but i havent jacked up the car and burped it lately. Ill try that next. Increasing speed doesn't help from what ive noticed.
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06-02-2018, 10:55 AM
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Yes, you can change fan activation temp. Looking at a MS2 file I have, it might just be under "boost/advanced", "programmable on/off outputs". One should be green (in use) and set to come on above a certain temperature.
Along with installing decent fans as suggested above, you should also set that temperature down to ~190. If I'm tuning a car I know has a good cooling system, I've set it to ~5* below thermostat opening temperature. That way they're always on, the termostat does it's job to regulate temperature, and the fan aren't coming on/off all the time affecting idle, load, etc.
As for the AC fan, it either comes on only with the button, and you need to wire it in parallel, or there may be another setting for it in the same menu, usually 10-15 degrees warmer than primary fan.
Along with installing decent fans as suggested above, you should also set that temperature down to ~190. If I'm tuning a car I know has a good cooling system, I've set it to ~5* below thermostat opening temperature. That way they're always on, the termostat does it's job to regulate temperature, and the fan aren't coming on/off all the time affecting idle, load, etc.
As for the AC fan, it either comes on only with the button, and you need to wire it in parallel, or there may be another setting for it in the same menu, usually 10-15 degrees warmer than primary fan.
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06-06-2018, 11:38 PM
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Alright so heres what ive done so far
Drilled a hole in the stat
Wired the fans in parallel
Set the temp for the fans to engage at 175 degrees\
Added a bottle of water wetter
And I actually got results! Never got above 208 while i was moving, with wot pulls, and ac on for the whole drive. Stayed at 199-200 for the majority of the drive.The only thing left is to duct the intercooler to the radiator. After that Im fresh outta answers. Should I just be happy with these temps? The numbers above were with 85 degree ambient at night, so they may change when i drive it with the sun out.
Drilled a hole in the stat
Wired the fans in parallel
Set the temp for the fans to engage at 175 degrees\
Added a bottle of water wetter
And I actually got results! Never got above 208 while i was moving, with wot pulls, and ac on for the whole drive. Stayed at 199-200 for the majority of the drive.The only thing left is to duct the intercooler to the radiator. After that Im fresh outta answers. Should I just be happy with these temps? The numbers above were with 85 degree ambient at night, so they may change when i drive it with the sun out.
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06-07-2018, 12:13 PM
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Use OEM fans and duct seal the bumper mouth to the radiator without openings. Allow as much air as possible to go around/over/under the intercooler on the way to the radiator. The radiator is far more important.
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