Anyone running their car without the thermostat?
07-06-06, 06:24 PM
#1
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Anyone running their car without the thermostat?
I was just wondering.......I mean all thats really for is to help warm the car up faster. I don't mind sitting a little longer till the car warms up. It would be one less thing to worry about going bad. Any experience's with this would be appreciated.
07-06-06, 06:59 PM
#3
RX-7 Bad Ass
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You need some restriction in the cooling system. Also, the car will likely never get to operating temp - if the engine is cold, it drinks more fuel, and power is also affected.
Use quality Mazda thermostats and you won't have a problem. If you want to get crazy with it, change the thermostat every 50,000 miles.
Dale
Use quality Mazda thermostats and you won't have a problem. If you want to get crazy with it, change the thermostat every 50,000 miles.
Dale
07-06-06, 11:57 PM
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bad idea,
don't just do something cuz it "seems" like a good idea.
it's not.
you're not going to get better cooling efficiency from it,
and the added cold warm up time will add wear to your motor.
it is also possible that your motor never reaches full operating temp,
which would mean added wear as well.
the key to engine cooling is warming up your motor quickly and properly,
then keeping it there.
get an upgraded radiator if your worried about it
don't just do something cuz it "seems" like a good idea.
it's not.
you're not going to get better cooling efficiency from it,
and the added cold warm up time will add wear to your motor.
it is also possible that your motor never reaches full operating temp,
which would mean added wear as well.
the key to engine cooling is warming up your motor quickly and properly,
then keeping it there.
get an upgraded radiator if your worried about it
07-07-06, 01:40 AM
#5
If you remove the thermostat completely, you'll need to cover the bypass hole or it will allow coolant to flow straight back into the engine, completely bypassing the radiator.
According to Mazda Motorsports ( www.mazdamotorsports.com ),
According to Mazda Motorsports ( www.mazdamotorsports.com ),
A common problem with the rotary engine when used in sustained, high rpm use (road racing) is that of overheating. The following recommended modifications are intended for racing use ONLY. Unfortunately, a single modification usually will not solve an overheating problem. It generally takes a few (if not all) modifications to solve a serious overheating problem, depending on the conditions (temperature, etc.) you race under.
Pulleys
Changing to competition drive and water pump pulleys will significantly reduce, if not eliminate, water pump cavitation. Water pump cavitation on a rotary engine (with stock pulleys) is unavoidable at rpms above 6500-7000 and is a significant contributor to engine overheating. Cavitation is defined as a disruption of the water/coolant flow through the water pump. It is created when the water pump impeller spins at such a high speed that it is actually churning instead of pushing the coolant through the pump. Changing to a larger water pump pulley and a smaller drive pulley, allows the water pump to spin at lower rpms, effectively transporting the fluid through the pump.
NOTE: An alternate size alternator pulley is available that reduces the speed at which your alternator spins, providing longer alternator life.
Water Pump
Water Pump/Thermostat
If you are using a stock (cast-iron) water pump, we recommend "gutting" the stock thermostat, leaving just the thermostat casing. Because some "restriction" is helpful, generally removing the thermostat is not as effective as using a gutted thermostat or restrictor. It is also important to plug the thermostat housing's water bypass. This can be done very easily by tapping the hole (1/2" pipe tap) and installing a plug.
Radiator
In general, we have found that for road racing, rotaries need a heavy duty radiator and oil cooler to improve engine cooling. We offer competition aluminum radiators, heavy duty oil coolers and water/oil heat exchangers for rotary applications.
A water/oil heat exchanger can be used with, or in place of an oil cooler. They are very effective in bringing down oil temperatures.
RX7's
The oil cooler on these RX7s is mounted under the oil filter. It should not be used for competition purposes. Early model (1979-82 RX7s) use a shorter radiator than the 1983-1985 RX7s that allows room for the oil cooler to be mounted underneath. Although an oil cooler can be mounted in front of the 1983-1985 RX7 full length radiator this set-up seems to significantly restrict air flow to the radiator, which can cause overheating.
Pressure
Increasing the cooling system pressure by changing the cap will raise the boiling point of the fluid and will also keep the fluid from being expelled into the overflow tank. We recommend use of a radiator cap with a pressure rating no higher than 17-18 lbs.
Fluid
We recommend using a 90% water to 10% glycol mix. Water has superior heat transfer properties (2-1/2 times better) than glycol-based coolant products. Using distilled or purified water will reduce scale build-up.
It's important to remember to change back to a 50/50 water/glycol mix when storing the car, especially if you live in severe winter climates.
Pulleys
Changing to competition drive and water pump pulleys will significantly reduce, if not eliminate, water pump cavitation. Water pump cavitation on a rotary engine (with stock pulleys) is unavoidable at rpms above 6500-7000 and is a significant contributor to engine overheating. Cavitation is defined as a disruption of the water/coolant flow through the water pump. It is created when the water pump impeller spins at such a high speed that it is actually churning instead of pushing the coolant through the pump. Changing to a larger water pump pulley and a smaller drive pulley, allows the water pump to spin at lower rpms, effectively transporting the fluid through the pump.
NOTE: An alternate size alternator pulley is available that reduces the speed at which your alternator spins, providing longer alternator life.
Water Pump
Water Pump/Thermostat
If you are using a stock (cast-iron) water pump, we recommend "gutting" the stock thermostat, leaving just the thermostat casing. Because some "restriction" is helpful, generally removing the thermostat is not as effective as using a gutted thermostat or restrictor. It is also important to plug the thermostat housing's water bypass. This can be done very easily by tapping the hole (1/2" pipe tap) and installing a plug.
Radiator
In general, we have found that for road racing, rotaries need a heavy duty radiator and oil cooler to improve engine cooling. We offer competition aluminum radiators, heavy duty oil coolers and water/oil heat exchangers for rotary applications.
A water/oil heat exchanger can be used with, or in place of an oil cooler. They are very effective in bringing down oil temperatures.
RX7's
The oil cooler on these RX7s is mounted under the oil filter. It should not be used for competition purposes. Early model (1979-82 RX7s) use a shorter radiator than the 1983-1985 RX7s that allows room for the oil cooler to be mounted underneath. Although an oil cooler can be mounted in front of the 1983-1985 RX7 full length radiator this set-up seems to significantly restrict air flow to the radiator, which can cause overheating.
Pressure
Increasing the cooling system pressure by changing the cap will raise the boiling point of the fluid and will also keep the fluid from being expelled into the overflow tank. We recommend use of a radiator cap with a pressure rating no higher than 17-18 lbs.
Fluid
We recommend using a 90% water to 10% glycol mix. Water has superior heat transfer properties (2-1/2 times better) than glycol-based coolant products. Using distilled or purified water will reduce scale build-up.
It's important to remember to change back to a 50/50 water/glycol mix when storing the car, especially if you live in severe winter climates.
07-07-06, 03:26 AM
#7
Originally Posted by rx7superman
I was just wondering.......I mean all thats really for is to help warm the car up faster. I don't mind sitting a little longer till the car warms up.
~Ramy
PS: You've been on the forum since '01. You should know better than to post w/o searching. This topic has been covered - and thoroughly - a THOUSAND times now...
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07-07-06, 06:44 AM
#8
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Hi, thanks for all the input guys. It was just a thought.....I guess I did'nt really think of the consequences or the reality of it. I'll just go with a pettit thermostat then. I really do appreciate the feedback from everyone. Thank you!
07-07-06, 07:12 AM
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Originally Posted by DaleClark
You need some restriction in the cooling system. Also, the car will likely never get to operating temp - if the engine is cold, it drinks more fuel, and power is also affected.
Use quality Mazda thermostats and you won't have a problem. If you want to get crazy with it, change the thermostat every 50,000 miles.
Dale
Use quality Mazda thermostats and you won't have a problem. If you want to get crazy with it, change the thermostat every 50,000 miles.
Dale
1. Don't even think of it without an oil temp gauge.
2. Generally a bad idea and not even worth it.
07-07-06, 07:15 AM
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Originally Posted by FDNewbie
You're mistaken. You're referring to the coolant running through the TB. THAT coolant is only useful during warmup. The t-stat is to enable and maintain your engine in optimal temp range (190 - 220 F). If you don't run a t-stat, it'll never reach 190, so you'll always be running the motor out of the optimal temp range. Not only will that cause you to lose power and run inefficiently, but also it is BAD for the motor. In short, cooler isn't ALWAYS better
The gauges are indicating the heat content of the water. It's more accurate to say "the water will never warm up." The block itself is definitely hot.
07-07-06, 10:04 AM
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That's correct. The reason it won't read that is because the temp gauge measures the temperature of the coolant it's in - it's just a variable resistor (constant 5v sent, heat changes resistance, ECU calibrated to the resistance curve derives measured temperature of coolant the probe is in). Since the sensor itself is not in the block - it won't indicate block temperature - and even that would be incredibly latent and not a good indicator for problems until it's much too late.
So in simple terms, b/c the coolant is circulating too fast to absorb (enough) heat from the block, the coolant is essentially cold, right? 
07-07-06, 01:50 PM
#14
Originally Posted by Fish
One thing that might be worth trying is replacing the stock thermostat with the one from the MX-5/Miata. They open at a lower temp.
Fish
Fish
How many people do this? First the FC thermoswitch, now the Miata thermostat?
Would this prove beneficial? I have a fluidyne radiator and autocross. I guess I want to know if it would be a safe thing to do and not have any downfalls, since I have the engine out right now.
07-07-06, 02:33 PM
#15
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I ran for 4 months with no stat. The car will take an age to warm up. Plus in cruising the car will drop into cold start. Dont bother doing it. how come you re thinking of this ?
Scott
Scott
07-07-06, 04:25 PM
#16
RX-7 Bad Ass
iTrader: (55)
Really, the stock 80 deg. C thermostat is perfect. 80ish degrees is proper operating temp for the motor, and if you have good fan control you can keep it right in that range all the time.
I don't see a reason for a cooler thermostat. The FD's thermostat is pretty cool as-is - there are some cars on the market that run very hot thermostats for fuel economy, and some people have seen performance gains on those cars by going to a cooler thermostat.
BTW, do NOT waste your money on Pettit's thermostat. It's a stock Mazda thermostat with a hole drilled in it.
Dale
I don't see a reason for a cooler thermostat. The FD's thermostat is pretty cool as-is - there are some cars on the market that run very hot thermostats for fuel economy, and some people have seen performance gains on those cars by going to a cooler thermostat.
BTW, do NOT waste your money on Pettit's thermostat. It's a stock Mazda thermostat with a hole drilled in it.
Dale
07-09-06, 01:50 PM
#19
Originally Posted by clayne
As I indicated above, it's generally a misconception that the car will not be running at optimal temp or "never warm up."
The gauges are indicating the heat content of the water. It's more accurate to say "the water will never warm up." The block itself is definitely hot.
The gauges are indicating the heat content of the water. It's more accurate to say "the water will never warm up." The block itself is definitely hot.
besides, i'm pretty sure the coolant temp sensor is right next to the oil pressure sender, which is on the rear iron housing.
07-09-06, 05:36 PM
#20
alexdimen, there are two coolant temp sensors, one is used for the ECU, and the other is only monitored by the (inaccurate) stock temp gauge on the dash.
The ECU coolant temp sensor is located near the filler neck, on the engine side of the thermostat. It is right above the water pump.
The gauge's temp sensor is on the rear iron, as you mentioned, by the oil pressure gauge. The sensor itself responds very quickly, but the stock temp gauge is center-weighted, and has a pretty slow response time as well. Both sensors should see a similar temp, assuming there aren't any air bubbles in the system.
-s-
The ECU coolant temp sensor is located near the filler neck, on the engine side of the thermostat. It is right above the water pump.
The gauge's temp sensor is on the rear iron, as you mentioned, by the oil pressure gauge. The sensor itself responds very quickly, but the stock temp gauge is center-weighted, and has a pretty slow response time as well. Both sensors should see a similar temp, assuming there aren't any air bubbles in the system.
-s-
07-10-06, 05:25 PM
#21
Rotary Enthusiast
Originally Posted by clayne
That's correct. The reason it won't read that is because the temp gauge measures the temperature of the coolant it's in - it's just a variable resistor (constant 5v sent, heat changes resistance, ECU calibrated to the resistance curve derives measured temperature of coolant the probe is in). Since the sensor itself is not in the block - it won't indicate block temperature - and even that would be incredibly latent and not a good indicator for problems until it's much too late.
The reason the oem gage will not show low coolant temps is because it is non-linear, and shows "normal" from about 140F-240F.
Based on on many infared measurements, bulk flowing coolant temps in the block is very close to typical block metal temps, for EGW mixes. As long as system pressure and flow is adequate, true coolant temp gauges are an excellent way of making sure typical local boiling at hot spots is quickly condensed ... avoiding dnb (gross boiling). Rising temp gauges, in general, is often a good safe warning to shut off the engine and find what is wrong.
If running at a track, or city traffic in florida, proper operating temps will be reached if the t-stat is removed (by-pass should be plugged). But, if cruising the highway a mid-winter nite in minnesota, metal and coolant temps will be far too cold for proper ecu function.
The colder you run an engine, the more energy is wasted as heat. There is a reason Nascar engines target 240F coolant temps, with high pressure caps.
07-10-06, 11:39 PM
#22
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everybody is missing one thing, if you removed the thermostat then the coolant wont actually have time to cool in the radiator since it's flowing constantly. Keep in mind it's design has a purpose.
07-11-06, 11:36 AM
#23
Originally Posted by f150rx7
...if you removed the thermostat then the coolant wont actually have time to cool in the radiator since it's flowing constantly...
I am really tired of hearing people regurgitate this crap about the coolant 'flowing too quickly to transfer heat.' At what rate does the coolant flow with the thermostat fully opened? How fast is 'too fast to transfer heat'? What is the flow rate of a system without a thermostat?
If you can't answer these three simple questions, or point me to some data that backs this theory up, please quit repeating this rumor!
-s-
07-11-06, 01:53 PM
#24
Rotary Enthusiast
Originally Posted by f150rx7
everybody is missing one thing, if you removed the thermostat then the coolant wont actually have time to cool in the radiator since it's flowing constantly. Keep in mind it's design has a purpose.
Misinformation is worth missing. Heat transfer co-efficient for fluid metal interface increases with fluid velocity.
A reason to run a gutted stat at a track is to increase pressure around chambers and exh ports, to minimize local boiling (water mix systems).
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