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How should I cool my budget DIY turbo setup?

 
Old 02-21-2019, 10:31 AM
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Default How should I cool my budget DIY turbo setup?

As the title states, I'm trying to figure out the best solution for cooling my DIY turbo setup on my NB1. It will be primarily a street car, although I would like to hit the drag strip and the track at some point. Track use is going to be pretty rare though. Im located in the midwest and experience down to 0 degrees F in the winter and up to around 105 degrees F in the summer. I like to drive my Miata year round, and want to make sure that the setup I choose facilitates that (keeps the car cool on the hottest days but still allows it to warm up properly in freezing temps).

From what I understand (and correct me if I am wrong), but cooling cylinder number 4 is still an issue as the NB1s don't have the revised head the NB2s do.

What would you all suggest is the best radiator option below to go with or without a cooling re-route, keeping a budget mindset? (Might not be the best wording, let me know if I need to clarify)

Traditional (non-crossflow) radiator options:
  • Stock
  • Ebay Aluminum
  • Mishimoto / Koyo
Crossflow Radiator Options:
  • Trackspeed
  • SuperMiata
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Old 02-21-2019, 10:36 AM
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Coolant reroute and ducting should be the first things to do.
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Old 02-21-2019, 10:40 AM
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Are you keeping AC?

Driving hwy or spirited with AC on requires much more robust cooling solutions
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Old 02-21-2019, 10:49 AM
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Originally Posted by Skamba View Post
Coolant reroute and ducting should be the first things to do.
Ducting beyond the stock "under tray" thing? Like one of the upper radiator cowl covers?

Originally Posted by borka View Post
Are you keeping AC?

Driving hwy or spirited with AC on requires much more robust cooling solutions
Yes, I have to keep AC, I would boil alive without it during the summer. It only gets up to ~105 F here, but its a humid 105. I typically try to avoid doing spirited driving with it on though. It would mostly be used during highway driving, which will be a decent portion of my driving.
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Old 02-21-2019, 10:58 AM
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Originally Posted by atotalpro View Post
Ducting beyond the stock "under tray" thing? Like one of the upper radiator cowl covers?
Yes - basically you want every bit of air that goes through your bumper hole also to go through the intercooler/radiator. With a bit of DIY it's not that hard to do.

This yt-video is quite insightful, but there's plenty of threads on here too:

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Old 02-21-2019, 11:19 AM
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Originally Posted by atotalpro View Post
Ducting beyond the stock "under tray" thing? Like one of the upper radiator cowl covers?



Yes, I have to keep AC, I would boil alive without it during the summer. It only gets up to ~105 F here, but its a humid 105. I typically try to avoid doing spirited driving with it on though. It would mostly be used during highway driving, which will be a decent portion of my driving.
i am no cooling expert, but here is what my experiences are:

99 turbo miata: stock radiator, no air guide, with under tray:
- No AC normal driving, no problem. with AC will overheat on hwy, and im sure will overheat at a track day

02 turbo, big ebay aluminum radiator ala mishimoto style, but no name, coolant reroute, with under tray
- Also will overheat with AC on hwy

new 02 turbo (current car) Mishimoto radiator w/stock fans, light diy ducting, air guide and undertray installed, and singular hood vents and reroute.
- Can hammer on it all i want at the track, never goes above 210-215f
- with AC on hwy (75-80pmh) its barely keeping up on the hottest florida days, will kreep up to 220f or so, but have not overheated

so moral of the story, AC on hwy is the biggest heat inducing part, and will need the most versatile cooling solution.

this is my personal experience, others may have better suggestions or solutions.
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Old 02-21-2019, 02:16 PM
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Originally Posted by borka View Post
i am no cooling expert, but here is what my experiences are:

99 turbo miata: stock radiator, no air guide, with under tray:
- No AC normal driving, no problem. with AC will overheat on hwy, and im sure will overheat at a track day

02 turbo, big ebay aluminum radiator ala mishimoto style, but no name, coolant reroute, with under tray
- Also will overheat with AC on hwy

new 02 turbo (current car) Mishimoto radiator w/stock fans, light diy ducting, air guide and undertray installed, and singular hood vents and reroute.
- Can hammer on it all i want at the track, never goes above 210-215f
- with AC on hwy (75-80pmh) its barely keeping up on the hottest florida days, will kreep up to 220f or so, but have not overheated

so moral of the story, AC on hwy is the biggest heat inducing part, and will need the most versatile cooling solution.

this is my personal experience, others may have better suggestions or solutions.
Originally Posted by Skamba View Post
Yes - basically you want every bit of air that goes through your bumper hole also to go through the intercooler/radiator. With a bit of DIY it's not that hard to do.

This yt-video is quite insightful, but there's plenty of threads on here too:

https://www.youtube.com/watch?v=VULqIfWu_XI
Alright guys, looks like a re-route and ducting is where my time and money will be best spent.

I think im going to approach these from a DIY angle and I have a quick question on coolant flow in relation to the heater core. Does the coolant flow from the front of the block, through the heater core, and then rejoin the system and the back of the head to flow to the radiator, or is it the reverse? If it is the former, there shouldn't be an issue placing the connection for the heater core -> back of the head after the thermostat, right?

Edit: Never mind, I answered my own question. It is the later in terms of flow direction. In this case, would there be any negative effects placing the heater line after the thermostat?

Last edited by atotalpro; 02-21-2019 at 02:21 PM. Reason: partially answered my own question
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Old 02-21-2019, 06:00 PM
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CSF (Supermiata has it) or the new 37mm Koyo; with re-route, stock fans, and proper ducting. Ducting does not have to be real complicated, or noticeable. When you set it up, don't let the FMIC block all the air to the radiator. Bypass some of the air.
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Old 02-21-2019, 07:12 PM
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I think the $100-$110 all aluminum ebay radiators can not be beat for the price. I only use those or TSE radiators in all my cars.
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Old 02-21-2019, 08:32 PM
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I'm going to disagree with people here a bit.

In my experience, for STREET DRIVING, coolant reroutes and hood vents are unnecessary. You can't use the throttle enough on the street for the turbo power to really matter -- what matters is the fact that the intercooler is blocking your radiator airflow, and you probably removed all the factory ducting up front along with the undertray when you installed it. Put those back in, modifying the ducting to fit. If the ducting is too hacked up to fit, then look into making some DIY ducting.

Put a decent-sized aluminum radiator in it, if only because a stock plastic that's as old as an NA/NB one will shatter if you look at it cross-eyed. No need for expensive cross-flow, etc.

I have no experience with the drag strip, but I suspect that 12-13 seconds of WOT every 30 minutes isn't likely to tax the cooling system much. Water has a lot of thermal mass.

TRACK DRIVING is something else entirely, and well-covered elsewhere on this forum.

--Ian
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Old 02-21-2019, 09:00 PM
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You need ALLOFIT or you may as well just junk the car.
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Old 02-21-2019, 09:07 PM
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Originally Posted by codrus View Post
the drag strip, but I suspect that 12-13 seconds of WOT every 30 minutes isn't likely to tax the cooling system much.
^Yep, this.

12 seconds of WOT and 45 seconds of return cruise don't tax the cooling system at all. You need to make sure you are warmed up before you go, and coolant temps drop compared to waiting in line. The FMIC is heavily taxed, at least with my setup.
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Old 02-22-2019, 01:43 PM
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I have a 2001 mk turbo car. Mishimoto big radiator, flyin miata spal fans and no reroute. With ac on and sustained hiway speeds of 80 or more temps will got to 210*.Took more than an hour at 87* outside weather. Normal hard, boosted street driving temps rarely get to above 200*. I have ducted the mouth, at the bottom, sealing the ic, condenser and radiator. I believe my next step is a reroute. Beyond that more ducting. I'm waiting for the heat of summer to really test my latest ducting results, then I'll decide what to do.
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Old 02-22-2019, 08:01 PM
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Lots of good feedback here. Before posting here, I suspected an oversized radiator would be enough for my driving and it sounds like it probably is, although just barely. I do like the idea of correcting Mazda's corner cutting with the re-route though and it seems like the re-route can be done for a pretty low price if you follow Beavis Motorsport's recipe.

This brings me back to my other question from earlier. Does anyone know know if putting the heater fead hose after the thermostat would have any ill effects? Also, what is considered appropriate temp ranges for street and track driving?
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Old 02-23-2019, 03:17 AM
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Originally Posted by atotalpro View Post
This brings me back to my other question from earlier. Does anyone know know if putting the heater fead hose after the thermostat would have any ill effects? Also, what is considered appropriate temp ranges for street and track driving?
You need to circulate coolant around the motor before the thermostat opens, in order to allow the heat from the interior of the block to get into coolant that is sitting next to the thermostat so that the thermostat will open. If it can't circulate then you wind up with stagnant volumes of water where the heat takes a long time to transfer across. In the stock configuration this is achieved by having the heater core provide a small (thus relatively high restriction) bypass around the thermostat. If you move the heater core location, you will screw this up.

In general there are basically only two cooling configs that make sense -- one of them is stock and the other is the one that's used by the major coolant reroute kits on the market. There are at least a couple big threads on this forum in which people talk about all kinds of possible alternate coolant routing systems, if you want more details on why various options don't work I suggest reading those threads.

The reroute config is "better", but by the nature of being aftermarket it has downsides. First is the cost, it's a two to three hundred bucks for a complete kit that's done properly -- that's a lot of money to spend if it's not going to provide any benefit to you. After that, having the thermostat at the back of the head makes maintenance harder. It's a cramped space so there's less access, it's tight working in there. You may need to extend the wiring harness for the coolant temp sensor (M-tuned kit), which introduces additional wiring crimps and potential future failure pints. There are more joints in the cooling system, which means more places for it to leak. Parts are non-standard, meaning that you can't just ask the guy at the parts desk for a Miata thermostat or gasket or whatever, instead you need to look up the cross-reference numbers. This makes it more difficult to get the car serviced at a normal auto repair shop if for some reason you might want/need to in the future. As for reliability, the top radiator hose is now much longer and runs along the intake side of the engine where there are lots of other components it can potentially rub, which means you need to inspect it more frequently.

These are all relatively small issues and I'm not saying anything bad about the kit manufacturers, it's just inherent in the nature of an aftermarket part. It's absolutely the right choice for a track car but if you don't have one of those then what's the point? What are you gaining by doing it?

--Ian
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Old 02-24-2019, 01:43 AM
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Originally Posted by codrus View Post
You need to circulate coolant around the motor before the thermostat opens, in order to allow the heat from the interior of the block to get into coolant that is sitting next to the thermostat so that the thermostat will open. If it can't circulate then you wind up with stagnant volumes of water where the heat takes a long time to transfer across. In the stock configuration this is achieved by having the heater core provide a small (thus relatively high restriction) bypass around the thermostat. If you move the heater core location, you will screw this up.

In general there are basically only two cooling configs that make sense -- one of them is stock and the other is the one that's used by the major coolant reroute kits on the market. There are at least a couple big threads on this forum in which people talk about all kinds of possible alternate coolant routing systems, if you want more details on why various options don't work I suggest reading those threads.

The reroute config is "better", but by the nature of being aftermarket it has downsides. First is the cost, it's a two to three hundred bucks for a complete kit that's done properly -- that's a lot of money to spend if it's not going to provide any benefit to you. After that, having the thermostat at the back of the head makes maintenance harder. It's a cramped space so there's less access, it's tight working in there. You may need to extend the wiring harness for the coolant temp sensor (M-tuned kit), which introduces additional wiring crimps and potential future failure pints. There are more joints in the cooling system, which means more places for it to leak. Parts are non-standard, meaning that you can't just ask the guy at the parts desk for a Miata thermostat or gasket or whatever, instead you need to look up the cross-reference numbers. This makes it more difficult to get the car serviced at a normal auto repair shop if for some reason you might want/need to in the future. As for reliability, the top radiator hose is now much longer and runs along the intake side of the engine where there are lots of other components it can potentially rub, which means you need to inspect it more frequently.

These are all relatively small issues and I'm not saying anything bad about the kit manufacturers, it's just inherent in the nature of an aftermarket part. It's absolutely the right choice for a track car but if you don't have one of those then what's the point? What are you gaining by doing it?

--Ian
Thanks for going over the cooling routing. It makes a lot of sense with your explanation. I will admit, the re-route does sound like a lot of added complexity for a gain I don't even know if I need yet.

At this point I will probably just toss in one of those aluminum e-bay radiators and construct some ducting. If that isn't sufficient, then I will look further into a proper re-route.
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Old 02-26-2019, 12:32 PM
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I believe the consensus regarding coolant reroutes (at least from what I have gotten from reading multiple cooling threads) is 1990-2000 Miatas always benefit from a re-route, given they aren't running a VVT Engine with the stock head gasket. 2001-2005 Miatas have a different head gasket design keeping coolant from flowing as much to the front cylinders. Emilio from 949 Racing has ran many VVT equipped miatas on the track with a re-route, keeping the stock head gasket and hasn't had any issues. The main concern seems to be that the coolant temperature sensor is at the back of the block, and not the front, so if cylinder 1 is significantly more warm than cylinder 4 you wouldn't be able to tell until something catastrophic happens, for both stock 4W gaskets and Z3 gaskets with a re-route. As I am cheap and my Miata is currently NA, I have only gone with a Flying Miata Stage 2 Airflow kit (which is severely overkill for NA builds) and have foregone the coolant re-route. If I were to open up my engine, I would install a 4W head gasket instead as well as a re-route, which would most likely lead to the best case cooling scenario between all the cylinders, however I would rather not get into the engine internals unless I have to.

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