thermostat

[sdean]

Hey now I see folks changing their stock thermostat for a cooler one..even I have done that ..now with some cooling issues my car buddie says that a cooler stat may make the car run hotter because the flow of water is faster through the radiator and does not get a chance to cool as well as with a hotter stat and slower opening for flow to occur..and giving more time for heat dissapation...so what is the right answer? Cooler stat or leave the stock one alone?

[XOCobra]

Hey now I see folks changing their stock thermostat for a cooler one..even I have done that ..now with some cooling issues my car buddie says that a cooler stat may make the car run hotter because the flow of water is faster through the radiator and does not get a chance to cool as well as with a hotter stat and slower opening for flow to occur..and giving more time for heat dissapation...so what is the right answer? Cooler stat or leave the stock one alone?

I did both on my 96. went back with stock and put a pusher fan on it to increase airflow across the radiator :grin:

[Oz98Cobra]

A cooler stat does not increase the flow rate. Some stats are marketed as "high flow", but my experience with these has been that they usually don't flow any more than the stock unit? Understand that it is the water pump and the speed at which it is driven that is the main contributor to flow rate. Leaving the stat out altogether may cause problems, as might one which is overly restrictive? No stat or an overly restrictive one is likely to cause problems with the cooling system pressure more than overall flow rate - messing with this can cause problems like localized boiling. If you restrict the flow too much at the stat, pressure behind it goes up - if you reduce the restriction at the stat, pressure behind the stat drops, and our systems are designed to run in a certain pressure range.

You do have to be careful with how cool a stat you put in your car because our computers expect a certain temp range to be reached and until it is reached it does not go into normal driving mode. A 180 degree stat is not going to cause problems, but a 160 might in very cold weather in a car with a good cooling system - unless you have a tune specifically programmed to make sure the computer is working as it should? It's also important to understand that a low temp thermostat will NOT make your car run cooler - all it does is allow coolant to flow sooner in the warm up process, but once that engine is hot, the stat is wide open and it can do nothing to help lower temps. They are popular with dyno tuners and drag racers because a cool engine makes power. I also recommend them for cars used on the road course along with switching the fans in earlier because it helps prevent heat soak when sitting around on the grid waiting for the next session. The temp at which the fans switch in should always be matched to the stat you choose.

So the bottom line is that a switch to a lower temp stat may be of some help in certain situations as long as it is not too low, and unless you buy some total POS product, they won't mess with your flow rate.

Hope this helps dispell some myths :)

[Oz98Cobra]

BTW, the temp rating of a stat is usually the temp at which it begins to open (stats don't just snap open at their trigger temp, they open gradually). The stock stat in most of our cars is rated at 192 - they start to open at that temp and are fully open at around 210. The Hypertech 180 degree stat I run stat starts to open at 180 and is fully open at around 198.

[sdean]

Well I figure that once the stat is open then flow will occur according to the engine and pump and the stat will allow the flow to occur when the opening temp is reached..My confusion is to help run the system cool in this Texas weather and the fact that I have an intercooler in front of the radiator..i think the '03 Cobra is set to run at a given temp and the ECU will try to get there..(i think 194 degrees) but what about these cooler stats? Is it a good idea or go back to stock or just a few degrees cooler...and what about a larger capacity radiator? What is the bottom line?

[burlesonsnake]

Bigger is better! Heat.... more HP = more BTUs burned = more heat in the combustion process. The coolant must transfer (in your case extra) heat from the heads/block/oil to the radiator. There is a set amount of coolant so only a set amount of heat may be transfered at any time. The radiator then must transfer the heat to the surrounding air.
A bigger radiator will give more coolant plus more area for heat transfer. The next problem is getting the heat out of the coolant and then away from the engine compartment. Better airflow through the radiator and then out of the engine compartment is as (if not more, in your case) important as moving the heat to the radiator. A hood with relief capability may be helpful. Just some things to think about.

[Oz98Cobra]

Absolutely! You're not still running the stock 03 radiator in that beast of yours surely? It should have been part of the design from the get go? But then again, we know that the folks who designed the system tuned out not to have much of a clue right?

My 98 n/a DOHC is pretty much stock, and the original radiator was not adequate to stop the temp gauge from pegging when I ran it on a road course in the Texas summers. I upgraded to an 03 Cobra radiator, and it cured the problem - but only just! The stock 03/04 radiator has 50% more capacity than a regular Mustang radiator, but it is still just a single row (the core is 1.5" thick compared to a regular Mustang radiator that is only 1" thick). I would consider it just adequate for a stock street driven 03/04 - but not even close for a souped up 03/04? If you don't have one already, consider a big old Fluidyne or similar? These aftermarket rads have around a 2" thick core and are double row (which means the coolant spends a lot more time in the rad for heat to be extracted).

[Oz98Cobra]

..i think the '03 Cobra is set to run at a given temp and the ECU will try to get there..(i think 194 degrees) but what about these cooler stats? Is it a good idea or go back to stock or just a few degrees cooler...

I'd recommend a 180 degree - cooler than stock but will ensure that sufficient temps are reached in any conditions.

[Lyle]

Don't forget that underdrive pulleys also slow the water pump down and therefore don't move the coolant as fast as stock.

[Oz98Cobra]

Don't forget that underdrive pulleys also slow the water pump down and therefore don't move the coolant as fast as stock.

Good point - slowing down the water pump is actually a good thing for a car that that spends a lot of time at high revs like those that are run on road courses - but not necessarily so good for blown cars on the street?

[sdean]

I'd recommend a 180 degree - cooler than stock but will ensure that sufficient temps are reached in any conditions.
I started with a 170 or 178 I still have it..do you recommend putting in a used stat?

[burlesonsnake]

As cheap as they are, I wouldn't.

[Coop]

Airflow and heat extraction are what you need to add.

Pusher fan (or two) on front, then do something about the additional heat you now have under the hood. Your force fed engine is generating more. That coupled with the two turbos and all that additional exhaust header tubing -- well, you get the idea.

May I suggest a heat extractor hood?

[sdean]

I talked about pusher fans and the guys said that at speed the fans would be restrictive and not allow flow faster that the speed I was going so the pusher idea was nixed and indeed a different hood may work too

[Coop]

I'm curious as to who those "guys" are. Sounds like they are full of good advice ;)


Now here's some personal experience --

I've got two 14" pusher units, thermostatically controlled. I installed in addition to factory puller. Made a BIG difference for me. A/C, Texas summer heat, no problem. Air flow? At speed, water temp actually drops to just below thermo set point (even with a/c running).

Bought fans on eBay for $25 apeice. 2200CFM flow, quiet curved blade design, intended for pusher use. Added relay, thermo controller and dedicated 8 ga fused circuit to battery. I re-programmed factory fan low/high set points to come on sooner (via Tweecer), and then programmed the pushers to compliment factory high speed circuit. Now only on when needed, automatically.

For efficiency -- add aluminum ducting. Prevents re-circulation of hot engine compartment air at low speed (like in traffic) and ensures all air goes through radiator and not around at higher speeds. Take a look underneath your car and you'll see why I did this.

So, do pusher fans restrict air flow? In my case, the gains far exceeded the so-called restriction.


In case anyone is curious, parts totaled around $110 for the mod -- two fans, controller, sheet metal, relay and some wiring. Would have been even less if I hadn't bought the thermo controller at 'always over priced' Pep Boys.

.

[sdean]

i talked to two guys and one worked for Patrick Racing on the NASCAR circuit and has built and is building now a street rod..and the other guy has also built hot rods and award winning magazine featured cars...but your setup sounds very good and tempting and I will persue something to tackle the heat

[TTvert]

i talked to two guys and one worked for Patrick Racing on the NASCAR circuit and has built and is building now a street rod..and the other guy has also built hot rods and award winning magazine featured cars...but your setup sounds very good and tempting and I will persue something to tackle the heat

dont feel bad steve, mine started to get hot, I had no idea, that once it starts to get where it maybe overheating, the ac just blows hot air, I guess i was cruising around in it too much today, stayed up late last night changing the oil in both of my cars, hey btw, is monthly meeting next saturday, I still need to get that paperwork in, I guess I can just bring it to the meeting right.

[Oz98Cobra]

I talked about pusher fans and the guys said that at speed the fans would be restrictive and not allow flow faster that the speed I was going so the pusher idea was nixed and indeed a different hood may work too

I think whether pusher fans would be a help or a hindrance depends on what the car is used for? On something like a race car that is usually moving pretty fast, pushers would likely be a hindrance and do little but restrict the available air flow a small amount - whereas on a street driven performance car, which would often find itself in slow moving traffic in summer, the pushers like on Coops setup would be a big help over the stock fan?

Here's an example - the Bondurant Cobras that have recently been retired and sold off to racers and open trackers around the country were eqipped with a pair of pusher fans up front, and an old school engine driven mechanical fan behind. They needed this setup to survive long periods of idling with the A/C on in the brutal 100deg+ Arizona heat when used in a driving school environment. But when converted for use in regular racing, this setup was not ideal - while it cooled the engine OK, all those fans were heavy and the mechanical fan robbed about 12HP, so most owners ditch the bondurant setup for a stock style single electric fan behind the rad - which works just fine for racing even in Texas summers.

In Steve's case, I would recomend a heat extractor hood first and put some thought into where the airflow is going, especially with those turbos making all that heat and affecting the airlfow on the back side of the rad? Make sure the fan is reprogrammed to kick in lower than stock - and if it still has trouble staying cool, then consider adding the pushers as Coop suggests. And you do have a big double row radiator already right Steve?

[sdean]

I have got to do something..I drove it the other day and it boiled over..

[Coop]

Steve,

I took a closer look at your setup last Sat at the meeting. You have some challenges, given placement of turbos and the air-to-air heat exchanger taking up the room in front.

You'll need to devise and implement some other createive cooling alternatives. I have some ideas. Do you want my help? You've got my email -- drop me a note.

- coop

**

[sdean]

I am looking for alternatives