Ebay rad should be under $100. I just ordered one for $93.

I have one of those group buy spacer rerouts. No issues with warmup, my car comes up to temp quick abd sits right at 183-185F (180f thermostat) with the stock fans and SM crossflow (that is being replaced with the ebay rad since it is leaking where the tubes meet the end tanks after only 2 yesrs and 10k miles. Cools super well though).

Edited my post for clarity.

MY car has this problem, with the old MTuned reroute. I had put in a new thermostat in the remote tstat housing, and I was getting a significant temp spike before the tstat would open. I took it out and drilled a hole, realized I did it in the wrong place, drilled another small hole. This solved the temp spike, but now my car has a hard time staying up to temp when it's cool outside. Coolant plumbing to turbo could also be an issue here, hadn't thought of that before this moment though so not sure.

@Quigs , which reroute do you have? I didn't read your post carefully enough before - shouldn't have any issue getting up to temp while cold when under load, that's for sure.

I've got a 1999 Miata. Indeed - I'd also like to have "even" cooling. I even thought that would be the natural progression of things... radiator...reroute...louvers. I would be wondering if all you had was a regular radiator setup + louvers, would you delta from front to back be even greater, or would the engine run generally cooler (since it's always getting much cooler coolant on the intake) - with similar/unchanged delta temps.

Your mod process is correct - Radiator, reroute, louvers. Some may say even doing the reroute very first, then radiator. Again, this is about even cooling more than overall cooling. Doing hood louvers with a stock-flow cooling system on pre- '01 Miatas is sortof like mounting wide hoosiers on stock wheels. You're skipping a step.

I live in the south where it can get fairly hot in the summer. I'm running an aluminum radiator, two fans (one for A/C the other for cooling), reroute, 180° tstat, and SM hood louvers. Just installed a turbo a few weeks back so I am not sure of how it will do in the summer however I did run all the cooling parts pre turbo and never have had an issue. Now I get to see how everything will hold up with the heat.

I have an OEM 195* thermostat. The car gets up to temp at idle no problem and idles between 190-205 exactly as it should. As soon as airflow at track speed is introduced the temps plummet. Not as much in August, but in March and November ambient temperatures at the track don't get much above 55-60 at the peak of the afternoon with near freezing morning sessions. A lot of guys tape up radiator openings in the cooler months that don't have the increased airflow of the hood louvers, so I'm sure some taping in both places for me should help get the temps up a bit higher. Just haven't experimented with it yet.

DIY reroute with Bell Tuning spacer, Kia thermostat housing/water neck, unmodified OEM 195* thermostat, and upper radiator hose that matches the one on my tow rig (2004 Silverado 2500HD with Vortec 6.0). CSF down flow radiator, OEM "shrouding", and distilled water with a splash of Water Wetter.

As others have said I would do reroute first, radiator second, and ONLY if you absolutely need it then consider the hood louvers. An aluminum aftermarket radiator provides more benefits than simply cooling efficiency or increased capacity. Most importantly they don't blow up because of old, brittle, plastic end tanks.

There is also the MSM stock radiator if you want something better than stock as far as more capacity and inexpensive. Ditch the AC if you have it for more flow and ducting.

I can't brain a scenario in which a functioning cooling system with a thermostat would over-cool.

r

A thermostat closing in a stationary engine will prevent it from over cooling. Not a moving vehicle with unregulated airflow. More capacity and more airflow is going to lower the temp if the thermostat closes. I had a 1.6 with proper reroute, meizer inline T-stat(not ideal), bypassed heater core and two different radiators(pwr and SPM csf) and used 2-3 different thermostats. Vented hood and had a unbeatable overcooling issue. It got up to temp fine but once moving temps dropped fast and would stay at 150-160* unless romped on continuously.

Tstats don't care if your moving or not. They function purely off of water temps. Dropping from 190f to 50f that suddenly sounds like a bad tstat sticking wide open to me. Even if the water in the radiator is 50f, the tstat *should* snap closed again once the heated block coolant has passed through and it sees the ice cold radiator coolant. My $0.02.

Yeah that sounds broken to me. The only time i've had a car overcool, ever, is when a thermostat wasn't working, or when i had a Begi Racer Reroute, which literally simply just bypassed the thermostat.

So wait... what I'm hearing here is that regardless if you had, for exaggeration's sake, a 100x capacity radiator (we'll just call it a huge tub of fresh room temperature coolant), starting up and warming up the engine should take the same amount of time since the thermostat's closed. Once it hits temperature it'll start opening up, and out goes the HOT coolant, and in comes the ~70F coolant. At this point the thermostat would proceed to close up again...only to repeat the process.

Does that mean, a system with high heat capacity just results in a thermostat that works "less?" Since it'll always be supplied with nearly ambient temperature coolant? So the time between needing to open, closing and opening again increases thereby causing the thermostat to do "less work?" Vs a system that's undersized, and even if the thermostat was stuck open, there wasn't enough cooling available...?

How fast does a thermostat open - and close? Its reaction time then would dictate the possibility of overcooling especially if the coolant on standby can maintain a nearly ambient temperature...no?

Reaction time wouldn't have any bearing on a consistent overcooling condition. Bad reaction time would cause swings, yes. But not consistently 50F below target.

Consistently below target = something is wrong.

To highlight this (basically effect of "weak actuator" on a control system) here's a graph showing these overshoots. I'm not a huge fan of this paper as a whole, and obviously the rpm/head of the water pump and heat generated by the engine will have a significant effect, but a picture says a thousand words.

https://cimg7.ibsrv.net/gimg/www.mia...15c6afb785.jpg
(Source: 10.11113/jt.v78.9667)

Thermostat is not a switch. It is an analog Proportional control only, once it opens the first time. Hence, initial warm-up goes above normal temp, and then things settle.

The ups and downs are caused by the fan, which is a digital control with a set operating high and low limit.

Correct. Ok - it's a spring. The fan's primarily have its job during idle and standstill...since when you're up to speed, that flow is generally >> the fan. Ok so in this case, after warmup - thermostat's open - albeit a little late due to its response - so there's the initial temp spike. Fresh coolant comes in...and the thermostat closes a little - accordingly - depending on the resultant temperature. So quigs is talking about his water temperature staying around 140F during those colder days with 65F ambient. So in this case, are we to assume that the coolant, radiator combo, thermostat position reached steady state at that temperature of ~140F? Let's just for fun's sake say the thermostat is effectively ~50% open at that temperature. Between the coolant coming in at 65F, and the water leaving out (I'm assuming this is where the sensor is) at somewhere north of 140F, being completely cooled back down to 65F (ish), is this effectively what's happening?

Standard Tstats for miatas open at 180°. That's when the Tstat STARTS to open. So remaining below that for any amount of time indicates a Tstat sticking open and not regulating correctly.

I see...so effectively, whenever the coolant goes below 180F for any reason, that TSTAT should be closing, etc. correct...? I haven't checked diagrams in a while, is there any source of bleeding that allows some coolant to bypass the thermostat? But regardless - it would still stand that a stock radiator, and a radiator with 20x capacity (exaggerated on purpose) SHOULD then warm up at the same amount of time since the thermostat's closed, correct?

When it opens though - out goes the hot coolant, and in comes the cold coolant............(let's assume 65F coolant)............will the thermostat close again, to allow the coolant to absorb more heat before heating back up to 180F and thermostat STARTS to open again?

Your bypass is the heater core. Warmup time is the same. Larger radiators only allow the water in them to cool for a longer period of time.
Your Tstat will will only open slightly if head temp is 180* and coolant is 60*. Its not an on/off switch, it opens in increments. Properly functioning Tstat will open only just slightly so that a small amount of very cold coolant will enter, keeping the coolant temp in the head at 180*.