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What temps are too hot to be normal?

Old 05-04-2017, 12:19 PM
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If you don't have the hose and pipe to lower it significantly or don't want to lower it , the other options are to create a better flow path above the crossbar or to trim the lower opening of the bumper mouth to allow a greater space between it and the intercooler for air to pass beneath the IC. Same pic for visualization, ignore the markings.


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Old 05-04-2017, 08:19 PM
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Originally Posted by joe morreale View Post
My 2001 has had the turbo on for about 2 months. Running hot has been an issue. I have and use AC. I have closed all the holes in the undertray and around the radiator/ IC / condensor. It was still not able to drive at 80 mph, with the ac on for more than 20 minutes without the temps running up to over 230. I changed to water wetter and bought the Flyin miata fan kit, with the dual Spal fans. Yesterday I drove, in 90 degree heat, with the ac on, for about 45 minutes between 75 and 85 mph, with a couple of boosted jumps. Temps went up to 220. I think this is as high as it's going to go. Is it still too high? At slower speeds, or with the ac off, temps will run between 195 and 210. I have the MK turbo kit. It's oil fed only, so no water lines going to it. Friends are telling me to do a reroute on the cooling but I've read mixed reviews on doing that to VVT cars, without changing the head gasket. Am I being too paranoid about temps or are they ok. Car has 55mm Mishimoto radiator and Vibrant intercooler, that is a knock off of the Fab9 one. It all just seems too hot to me. I'm using a 180 thermostat as well. I don't want to get stuck driving all blazing summer either not using ac or only driving 70 mph max, so I appreciate any responces.
I have done what you're doing before, had the same problems. Best I managed was about 215*F after extended driving on a 100*F day. In my case the next thing to do was to cut the crash structure out and move the heat exchangers around to allow more clean air to hit the radiator. I instead moved the a/c condenser to get it out of the way. You need to do SOMETHING to get more air to hit the radiator without having to go through all the other heat exchangers first, as already said the radiator just isn't receiving enough air. See if there's any way to duct it so that more air goes over, under, or around the front exchangers and straight to the radiator. On my current setup I let air go under the intercooler and then to the radiator.
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Old 05-07-2017, 01:19 PM
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Lars, from MK turbo is going to fit me with a smaller intercooler so I can get some airflow. I'm just probably going to drive without ac or go hard for long distances until I get it. I'll see what happens then.
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Old 05-07-2017, 02:38 PM
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I run the Supermiata crossflow radiator and rerout, and I can drive hard with the radiator completely covered with cardboard until 70 degrees ambient.

I'm sure you have some tweaking of intercooler placement, but I'd also say your radiator is part of the problem. IIRC Mishimoto isn't crossflow, and cant high powered fans hurt airflow across the radiator at speed? Aren't you supposed to only use a single spal fan to help combat this effect? Sorry if this stuff is wrong.
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Old 05-07-2017, 05:29 PM
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Down flow vs. cross flow doesn't matter if the radiators are built with the same cores. Now the stock radiator is down flow but has a single 5/8" core and just about all the aftermarket radiators are dual 1" cores and are bigger in surface area. None of that will matter if you don't get enough air flow through it. Get the mouth sealed to the radiator and leave some room for air to make it around the intercooler, thne focus on getting the air out from under the hood. I've seen guys cool 250 hp with those dinky half width Honda radiators with good ducting.
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Old 05-09-2017, 11:23 AM
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Originally Posted by sixshooter View Post
If you don't have the hose and pipe to lower it significantly or don't want to lower it , the other options are to create a better flow path above the crossbar or to trim the lower opening of the bumper mouth to allow a greater space between it and the intercooler for air to pass beneath the IC. Same pic for visualization, ignore the markings.


I have the factory air dam, for the bumper and undertray to attach to. It seals tight to the bumper mouth, as does the rest of the IC. I cut it according to flyin Miatas website.

I see you do not have the air dam. Are you not running an undertray or have you fabbed a different way of mounting it. Is the bumper stable without the air dam? Or am I totally wrong and you took this pic while it was apart, at some time.
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Old 05-09-2017, 11:40 AM
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That's Lars' pic. Mine is different from that. I'll post some when I get back to a computer.
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Old 05-09-2017, 12:52 PM
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My undertray goes to the bottom of the bumper and not the bottom of the bumper mouth. Air passes beneath the intercooler headed to the radiator.



In my case, the piece in the bottom bumper lip is notched to allow air to pass downward.





Air also passes above my intercooler and beneath the crossbar. If you lower your intercooler air may pass through there.



Additionally, air travels upward from the top of the bumper mouth between the crossbar and the black plastic inner bumper. I opened that up a little bit and placed my oil cooler there but yours will be open. Air that goes through there will go over the crossbar and past the hood latch mechanism to the radiator. This is probably the only pathway by which air is going to your radiator aside from going through your intercooler first. And it was a smaller opening before the sawzall molested it.

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Old 05-09-2017, 02:18 PM
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Great description. Have a poscat. Does anybody have similar pictures for NB?
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Old 05-11-2017, 05:42 PM
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Originally Posted by joe morreale View Post
in 90 degree heat, with the ac on, for about 45 minutes between 75 and 85 mph, with a couple of boosted jumps. Temps went up to 220.
Same issue here with a similar turbo/radiator/fan setup. Temporary fix works and keeps temps ~10deg cooler.

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Old 05-11-2017, 06:11 PM
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Originally Posted by sv650_ck View Post
Same issue here with a similar turbo/radiator/fan setup. Temporary fix works and keeps temps ~10deg cooler.

But doesn't it hurt your *** when you sit on it?
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Old 05-11-2017, 07:10 PM
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/D3d
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Old 05-11-2017, 07:22 PM
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You might as well remove the thermostat completely, that's not restricting flow enough to matter. Again you're focusing on the wrong issue, it's an airflow problem. I wouldn't​ waste effort on anything else till you vent the hood. Then get back to figuring out a better duct setup on the front side.
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Old 05-11-2017, 07:29 PM
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Car doesn't overheat.

Blocks radiator.

Car overheats.

People: "Have you tried changing the alternator belt?"
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Old 05-15-2017, 12:41 PM
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The only times I ever had serious overheating problems was when I had leaks in my coolant system. Even a tiny leak lowers the boiling point enormously which means that hot spots get shielded by bubbles instead of cooled, which leads to the hot spots spreading, and so on. And boiling coolant slowly leaving via the leak doesn't help either. Years back, I remember overheating on the highway (no boost, just cruising along at 70mph) because I had a heater hose with a tiny crack in it. This was back when I had the turbo but before I had done any cooling mods.

Nowadays I have a reroute, a huge radiator with a high pressure cap, big fans and a homemade fan shroud to help them suck through the radiator. And an oil cooler with a fan. My typical around town temps are 90-92 C coolant and 190 F oil. Coolant is measured at the back of the head, oil is measured at the filter, before the thermostat/cooler. The fans for both switch on when the coolant is at 92C.

Contrary to what everyone here advises, I don't run any under nose panels at all and make no efforts to force air through the intercooler/ac/radiator besides fan shrouds that seal up the area between the fans and the radiator. So long as your fans are working and they are pulling air through the radiator I don't see why an intercooler would be a problem.
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Old 05-15-2017, 12:47 PM
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Originally Posted by AlwaysBroken View Post
The only times I ever had serious overheating problems was when I had leaks in my coolant system. Even a tiny leak lowers the boiling point enormously which means that hot spots get shielded by bubbles instead of cooled, which leads to the hot spots spreading, and so on. And boiling coolant slowly leaving via the leak doesn't help either. Years back, I remember overheating on the highway (no boost, just cruising along at 70mph) because I had a heater hose with a tiny crack in it. This was back when I had the turbo but before I had done any cooling mods.

Nowadays I have a reroute, a huge radiator with a high pressure cap, big fans and a homemade fan shroud to help them suck through the radiator. And an oil cooler with a fan. My typical around town temps are 90-92 C coolant and 190 F oil. Coolant is measured at the back of the head, oil is measured at the filter, before the thermostat/cooler. The fans for both switch on when the coolant is at 92C.

Contrary to what everyone here advises, I don't run any under nose panels at all and make no efforts to force air through the intercooler/ac/radiator besides fan shrouds that seal up the area between the fans and the radiator. So long as your fans are working and they are pulling air through the radiator I don't see why an intercooler would be a problem.
Post pics of your Miata's mouth looking at intercooler. Does it or does it not restrict airflow to the radiators?
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Old 05-15-2017, 01:04 PM
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Also keep in mind that a turbo motor makes more heat in the engine than a comparable N/A or even supercharged motor. Not only are the EGT's higher but that heat is under pressure and held up against the head by the turbo so the cooling system has to work harder than it would for a given HP made otherwise.

Relying o the air's inertia is a bad way to proceed, I can share an example of 3rd gen Camaro that will overheat on the highway because the ducting isn't sealed, this is with a mechanical fan that is shrouded moving over 20hp worth of air through the radiator. Little bit of plastic to seal the radiator to the nose and it's fine now.
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Old 05-15-2017, 01:17 PM
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I've been running ceramic coated exhaust/turbine/dp for ages. Dunno how much it helps, but that's one thing.

I've run two intercooler setups over the past 14 years.
The first one was a smaller intercooler (2 inches thick, something like 12x20 ballpark IIRC) that was angled so that the bottom was up against the bumper and the top was near the radiator... it was nearly a 45 degree angle and the entire front of the radiator was exposed to the under body airflow. The rad fans could suck air through the radiator like normal at low speeds.
The second intercooler setup was a larger intercooler (3" thick x huge) that I still angle a bit forward, just not as much because there just isn't as much room.

In both my setups, the worst case air flow scenario is still the fans sucking air through radiator that draws air in from under the intercooler instead of through it. Having the intercooler pressed up tightly against the radiator would murder airflow during stop and go traffic and probably not do any favors at highways speeds unless you have every square milimeter of space sealed up tight so that air going in the front is forced through the restrictive 3 layer sandwich of IC + AC + RAD. What if the holes from one heat exchanger to the next don't line up properly?

I know, I know, it's crappy for downforce, but I don't overheat and I can beat on the car mercilessly. Btw, unless you're running hood vents, all the air through the nose still ends up under the car.

IMO, it would be a lot easier for airflow if the IC + AC + RAD were all integrated into one 6" thick heat exchanger so the air doesn't have to navigate the incompatible air passages of three heat exchangers sandwidched together. The first 2-3 inches could be intercooler airflow, the next 2 inches could be radiator and the last inch could be the AC cooling bit (maybe make one side of that last inch be oil cooler). Drive it all with one strong fan. You'd have to make the intercooler end tanks be top/bottom or convert the radiator to L/R flow so that all the passages are the same orientation. The more I think about this idea, the more it seems like a bad idea- but the only real alternative is to separate the parts of the sandwich and manage their airflow separately.

Last edited by AlwaysBroken; 05-15-2017 at 03:02 PM. Reason: added intercooler size notes, comments at the end
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Old 05-15-2017, 01:27 PM
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Btw, I found this while googling the subject.

During WWII, they found that you could angle a heat exchanger (air to air intercooler here) as much as 70 degrees from the air flow and there's almost no effect on flow through the intercooler. This seems to have been a low speed test despite the aviation application. Caveats galore.

http://www.dtic.mil/dtic/tr/fulltext/u2/a801014.pdf
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