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Old 12-22-2012, 06:54 PM   #41
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Originally Posted by Savington View Post
All true, but what you're conveniently forgetting is that beyond switching to dual cores (we have) and making the radiator slightly taller (we have), there is no other way of increasing core cross-sectional area other than going thicker (or tube-framing the front of the car, but I don't think that's reasonable for most people). We are restricted by the shape of the car, so we have to do what we can within the space constraints.

The gains from going thicker are diminishing, yes, and it's not the ideal way to increase heat transfer, but it's the only option that large-market aftermarket radiators have, and there are still gains to be seen. We've proven this empirically through hundreds and hundreds of hours of testing.



No, they don't. You are associating "bigger radiator" and "larger water capacity" without acknowledging that 1) a larger radiator with a greater transfer area from the incoming air to the coolant is going to shed more heat, and 2) larger radiators don't always have more water in them. If you put an insulated water tank with zero heat transfer capability in-line with one of the radiator hoses, then yes, it's just going to delay the problem, but the increased water capacity is not what keeps the car cooler. The truth is that our radiators actually have LESS water capacity than a Koyo 55mm, which is why (despite their size) they weigh the same when filled with water.
-You can decrease tube spacing, and more fins/inch, and just switch to a higher quality core. Thicker cores/radiators weigh more and are in front of the centerline of the front wheels. This is bad for vehicle dynamics so if you can cool just as well without adding weight, that is a huge benefit. Also with deceased tube spacing, you could have the radiator double passed or triple pressed (depending on water side Reynolds Number).

-The only way a thicker radiator wouldn't have as much water in it is if the height or width has decreased or if it has less tubes/drastic tube size differences.

-Only reason to need a 55mm core on a Miata is a bad ducting design. Also going with quality race proven radiator core like Denso or PWR helps a lot. Even Vista-Pro makes a few decent cores one could use.
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Old 12-22-2012, 07:11 PM   #42
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plucas, I assume you personally race a Miata with one of the cores you mentioned? I know a lot of people with 55mm Koyos in Spec Miatas with all-OEM plastic ducting who can't keep their cars cool in 100*F weather.
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Old 12-22-2012, 07:24 PM   #43
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All good theory. Have any actual test data from a Miata to back it up? What do you personally race?
On a Miata? No

I personally race nothing currently. However my job currently is the design of heat exchangers which includes radiators. So my theory is not only backed up with science, but the real world. I am still looking on what I want to buy to build my own race car. A Miata is on the top of my list because owners actually like to build racecars Also I am not trying to be a dick so don't take it that way. I just have experience in designing radiators and trying to pass on my knowledge.

I can tell you a 27mm Denso core will cool ~800hp nascar around IMS.
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Old 12-22-2012, 07:32 PM   #44
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You can do the reroute for about $125 or so. You order the Begi spacer, get the kia water neck, and the GM coolant hose. Then get the TSE front block off plate.
I cannot endorse the BEGi spacer. I recommend the M-tuned reroute.
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Old 12-22-2012, 07:34 PM   #45
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On a Miata? No

I personally race nothing currently. However my job currently is the design of heat exchangers which includes radiators. So my theory is not only backed up with science, but the real world. I am still looking on what I want to buy to build my own race car. A Miata is on the top of my list because owners actually like to build racecars Also I am not trying to be a dick so don't take it that way. I just have experience in designing radiators and trying to pass on my knowledge.

I can tell you a 27mm Denso core will cool ~800hp nascar around IMS.
Yeah, but they also have awesome ductin-aero that we don't have space for. If I could build a 2' long carbon fiber, aero friendly duct, I would. We have about 6-3" of space to work with and none of us own an autoclave.
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Old 12-22-2012, 07:37 PM   #46
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Originally Posted by plucas View Post
On a Miata? No

I personally race nothing currently. However my job currently is the design of heat exchangers which includes radiators. So my theory is not only backed up with science, but the real world. I am still looking on what I want to buy to build my own race car. A Miata is on the top of my list because owners actually like to build racecars Also I am not trying to be a dick so don't take it that way. I just have experience in designing radiators and trying to pass on my knowledge.

I can tell you a 27mm Denso core will cool ~800hp nascar around IMS.
Gotcha, very cool.

PWR makes a radiator for the Miata - something in the 37mm range, IIRC. It's well-respected but also expensive and it doesn't seem to do a significantly better job than a 37mm Koyo or even the larger 55mm Koyo.

When we were doing our development, we focued on a few hard-to-cool applications:
-Spec Miatas, which are forced to run OEM ducting, no reroute, and spend lots of time with the radiator inlet stuffed up the rear bumper of the guy in front of them.
-A/C-equipped forced induction cars, which have both an intercooler and an A/C condenser in front of the radiator (not good for airflow)
-Extremely high horsepower (300+whp) forced induction road race cars

The SMs we switch from Koyo 55s to our dual-core rads typically see CLT drops of 30-40*F. Early SMs (90-97s) want to run ~170*F since the ECU pulls timing above that, and our radiator allows for that even in high ambient temps. We also spent a lot of time testing in my turbo car, which (when it last ran) was ~350whp and held several of the Miata-chassis track records in California. That car had a full sheetmetal ducting setup, vented hood, coolant reroute, but still wouldn't stay cool with a 2" CSF. Switching to our big dual-core unit dropped CLTs from the 250+ range down to ~210-215*F. Basically, lots and lots of empirical data showing that our rads kick *** when compared to the other commercially-available aftermarket rads out there.

How big is that Denso core (area-wise)? Presumably those motors are also reverse-flowed and probably far more thermally efficient than our 25-year-old iron-block BPs
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Old 12-22-2012, 07:47 PM   #47
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none of us own an autoclave.
Speak for yourself, working-class peasant scum.
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Old 12-22-2012, 08:13 PM   #48
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Originally Posted by Savington View Post
Gotcha, very cool.

PWR makes a radiator for the Miata - something in the 37mm range, IIRC. It's well-respected but also expensive and it doesn't seem to do a significantly better job than a 37mm Koyo or even the larger 55mm Koyo.

When we were doing our development, we focued on a few hard-to-cool applications:
-Spec Miatas, which are forced to run OEM ducting, no reroute, and spend lots of time with the radiator inlet stuffed up the rear bumper of the guy in front of them.
-A/C-equipped forced induction cars, which have both an intercooler and an A/C condenser in front of the radiator (not good for airflow)
-Extremely high horsepower (300+whp) forced induction road race cars

The SMs we switch from Koyo 55s to our dual-core rads typically see CLT drops of 30-40*F. Early SMs (90-97s) want to run ~170*F since the ECU pulls timing above that, and our radiator allows for that even in high ambient temps. We also spent a lot of time testing in my turbo car, which (when it last ran) was ~350whp and held several of the Miata-chassis track records in California. That car had a full sheetmetal ducting setup, vented hood, coolant reroute, but still wouldn't stay cool with a 2" CSF. Switching to our big dual-core unit dropped CLTs from the 250+ range down to ~210-215*F. Basically, lots and lots of empirical data showing that our rads kick *** when compared to the other commercially-available aftermarket rads out there.

How big is that Denso core (area-wise)? Presumably those motors are also reverse-flowed and probably far more thermally efficient than our 25-year-old iron-block BPs
Yeah PWR stuff is very salty. Their cores are top notch though and have a lot of adjustability with tube spacing and fin pitch. They also offer extruded tubes to be able to run higher pressure.

Developing a radiator for multiple applications applications is difficult. Designing one that receives not so optimum air like spec miata makes it even more difficult which makes having a thicker core make sense. With no sort of rules on mounting and air ducting, I am a big fan of thinner cores.

The 27mm Denso comes in three common header dimensions (if I remember right). Smallest is 23.50" with the largest being under 30" as I forget the exact sizes. I can get actual sizes on Wednesday if interested. Height can be anything really as cores can be cut to height. Tube spacing for the Denso in 0.33" apart so heights can in increments of that number.
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Old 12-23-2012, 01:26 PM   #49
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Some time ago I measured radiator coolant inlet and outlet temp, and air temps in front and behind, in order to decide if the problem was poor heat transfer from the coolant to the radiator, or from the radiator to the air. It was very clearly the latter - the air in the back of the rad was very hot, and the coolant temp drop was reasonable. (Test was on the street, low-speed uphill twisties. Street car with a/c and i/c. I already had a pair of large shrouded Spals, sealed airflow around the radiator.)

I then swapped my i/c from the AVO bar/plate design, to the TDR tube/fin which has more open area to cooling airflow for the radiator, plus more "aerodynamic" ducting in front of the i/c. The results were pretty dramatic. The TDR tube/fin design also showed a huge increase in airflow from the fans when the car wasn't moving.

One other thing that I think helped my cooling noticeably, was the modified head gasket for my VVT head....
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Old 12-23-2012, 02:33 PM   #50
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I think Savington's latest radiators (Trackspeed Engineering) were dual pass radiators, which is the same style as what at least one spec Miata builder I know is running.
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Old 12-23-2012, 03:11 PM   #51
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Snipped a bit -
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Sure, if the fans are 18" in diameter and crank-driven. Twin 12" Spals aren't even going to come close to providing the necessary airflow through the radiator to effectively cool a track car. I know because I've tried.

Fans are for A/C equipped street cars. If your track car is overheating, you need to duct it from the front - no electric fan will come close to being as effective as a little bit of ABS ducting.

I don't know when this idea of "bigger radiators delay the problem" became popular, but it's total bullshit.
Andrew, the answer to your question is the same one I've asked a million times as I have scratched my head re; people such as yourself still claiming that shrouded fans don't provide "the necessary airflow through the radiator to effectively cool a track car". Years after I was selling my set-up, FM found on their cooling rig that a shrouded fan is more efficient at cooling than a couple fans strapped to the core. Most of you may remember that FM's cooling set-up prior to their current system comprised just the fans. You can lead a horse to water......

To the OP, a radiator that has a larger and more efficient core that allows more of the coolant/water into the core at one time WILL reduce temps beyond what a smaller radiator can. The Trackspeed radiator which is a very nice unit I might add and for those of you considering it to aid in your cooling efforts, you could do much worse. This radiator (or the one from FM or BEGi, the horizontal units) coupled with the re-route, proper ducting/sealing of the inlet to the radiator/IC/A/C condenser face and a properly shrouded set of fans should allow you to run your Miata in all but the hottest summers at full tilt.
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Old 12-23-2012, 03:24 PM   #52
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Snipped a bit -

Andrew, the answer to your question is the same one I've asked a million times as I have scratched my head re; people such as yourself still claiming that shrouded fans don't provide "the necessary airflow through the radiator to effectively cool a track car". Years after I was selling my set-up, FM found on their cooling rig that a shrouded fan is more efficient at cooling than a couple fans strapped to the core. Most of you may remember that FM's cooling set-up prior to their current system comprised just the fans. You can lead a horse to water......
Who was running "just fans" and running the cars hard enough to make the turbo hardware relax in 103*f heat? Serious question. There is still no fan that can move as much air as a car driving down the track.
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Old 12-23-2012, 03:33 PM   #53
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I'm probably a bit late to this thread, and i didn't read the last 20 or so posts. I'm just going to throw my input in here.

I was having overheating problems, i had the bumper ducting ripped out, belly pan ripped out, and stock radiator with stock fans (no reroute). Not only that i had an intercooler and the A/C still sitting up front. I thought i'd just throw money at the car to solve my problems. Ended up buying a Mishimoto 3 row (the big one) with their slim fans.

Didn't solve my problem. Helped a little at speed, but still had issues. After reading threads like this on here and getting some advice i built myself some bumper ducting and that solved 90% of my problems. I actually have overcooling problems now. I drove in about 40F rainy cold weather on the highway and i never came out of warmup enrichment (until i adjusted it).
The only time i overheat now is when the engine is off. Idling the fans run about 80% of the time. If i shut off i have bay heat issues. But that's another story.

Does your fan setup have a shroud on it? ** just read 2 posts up. Shroud your **** if you just have a fan strapped to it.
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Old 12-23-2012, 03:45 PM   #54
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Who was running "just fans" and running the cars hard enough to make the turbo hardware relax in 103*f heat? Serious question. There is still no fan that can move as much air as a car driving down the track.
If ANYONE is running hard enough to have turbo related hardware failure due to heat, then engine cooling isn't the primary issue. That's akin to having the ***** and believing it came from a sprained ankle.

Just for clarification, when I was manufacturing and selling my kit, it was designed to offset the reduced pressure differential that one gets with having an IC and A/C condenser in front of the radiator core. Ram pressure is diminished after each heat exchanger and conduction between the air and each heat exchanger causes a loss in air density so it doesn't matter how fast you are driving if the air volume and density reaching the radiator core isn't enough to allow for good heat transfer.
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Old 12-23-2012, 03:52 PM   #55
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If ANYONE is running hard enough to have turbo related hardware failure due to heat, then engine cooling isn't the primary issue. That's akin to having the ***** and believing it came from a sprained ankle.

Just for clarification, when I was manufacturing and selling my kit, it was designed to offset the reduced pressure differential that one gets with having an IC and A/C condenser in front of the radiator core. Ram pressure is diminished after each heat exchanger and conduction between the air and each heat exchanger causes a loss in air density so it doesn't matter how fast you are driving if the air volume and density reaching the radiator core isn't enough to allow for good heat transfer.
It sure worked well for Savington and I for the last few years and I was ~3 seconds under the SM record on <2m tracks. 2012 BTCC cars are just like ours in regard to stacked heat exchangers and only one little fan so the car can idle.

I'm sure your ideas work too...but Savington, myself, and others are doing it just fine without $500 in fans and a shroud.
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Old 12-23-2012, 06:30 PM   #56
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I have FM's Crossflow radiator, and their Stage 2 airflow kit with the big Spals. It is not enough. I have done the NB dual-fan mod, and I also installed a switch to ground so I can manually run both fans any time I want. In 75* ambient temps I was seeing 230+ coolant temps with both fans running at the end of the back straight at ORP. Note - the heat exchangers were not ducted in front, so there was lots of spillage.

Fans and shrouds are good for creating airflow in otherwise static conditions, but they block too much surface area at speed.

One of this winter's projects is removing the shroud and moving to just the bigger of the two Spals. And ducting the air coming in.
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Old 12-24-2012, 12:38 AM   #57
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Snipped a bit -

Andrew, the answer to your question is the same one I've asked a million times as I have scratched my head re; people such as yourself still claiming that shrouded fans don't provide "the necessary airflow through the radiator to effectively cool a track car". Years after I was selling my set-up, FM found on their cooling rig that a shrouded fan is more efficient at cooling than a couple fans strapped to the core. Most of you may remember that FM's cooling set-up prior to their current system comprised just the fans. You can lead a horse to water......
Myron, I have no problem believing that unshrouded fans are less efficient than shrouded fans, but what you need to understand is that it's still not enough. You missed Hustler's point - if you are driving the car hard enough to relax the turbo hardware (i.e. significantly faster than SM record), you cannot keep it cool with fans. I tried about 3 years and 80whp ago to use a set of shrouded fans to pull air through the intercooler to keep the car cool, and it resulted in catastrophic overheating almost immediately (<2 laps). If you expect to keep the car cool, you need to feed it air from the front of the car, and by the time you move enough air through the core to actually do the job, the fans and shroud are a restriction. (CLTs on my turbo car drop with increased speed).

Quote:
The Trackspeed radiator which is a very nice unit I might add and for those of you considering it to aid in your cooling efforts, you could do much worse. This radiator (or the one from FM or BEGi, the horizontal units) coupled with the re-route, proper ducting/sealing of the inlet to the radiator/IC/A/C condenser face and a properly shrouded set of fans should allow you to run your Miata in all but the hottest summers at full tilt.
I need to be very clear here: our radiator is not comparable to the FM or BEGi units. The only radiator on the market that has similar features to our radiator is Springfield Dyno's radiator, at ~$600/unit. Our radiators have two cores, unlike the FM/BEGi units, and this makes a world of difference when it comes to keeping things cool.
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Old 12-24-2012, 12:49 AM   #58
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I tried about 3 years and 80whp ago to use a set of shrouded fans to pull air through the intercooler to keep the car cool, and it resulted in catastrophic overheating almost immediately (<2 laps).
Well eff that pretty much sums up my current problem. I will have to address it before next summer.
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Old 12-24-2012, 12:59 AM   #59
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Old 12-24-2012, 11:33 AM   #60
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One of my favorite posts ever...
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