The Big Fat FD3S Cooling Thread
08-24-06 | 03:02 PM
#27
Originally Posted by cozmo kraemer
I had a question regarding oil temps. I see a lot of data regarding water temps, what is safe/what isn't safe. But, I have had a really hard time finding what sort of oil temps I should see. In 110 degree ambient temps my PFC coolant temp will go as high as 105 C with the A/C on or 95 C or so with the A/C off (A/C condensor must be a significant source of heat at those temperatures). My oil temp will hover around 115 C or a little higher. If you run at a slightly higher rpm (NOT boosting!) the oil temp can climb as high as 120C.
This is all in stop and go traffic. If you get out on the open road and get some real flow through the radiator, the temps come down...maybe 95-99 C coolant with the A/C on. 110 C or so oil temp.
My question would be...What is a safe oil temp? When do things start to get dangerous? Can we just go off of dangerous coolant temps? Will the coolant system fail because of overheat before the oiling system?
I just get a little scared of my oil temps sometimes, but my coolant temps have never been TOO alarming.
FWIW...when the ambient drops to 95ish, my coolant temps hover around 89C with the A/C on and my oil temps around 105C... The extra 15 degrees ambient temperature is HUGE!
This is all in stop and go traffic. If you get out on the open road and get some real flow through the radiator, the temps come down...maybe 95-99 C coolant with the A/C on. 110 C or so oil temp.
My question would be...What is a safe oil temp? When do things start to get dangerous? Can we just go off of dangerous coolant temps? Will the coolant system fail because of overheat before the oiling system?
I just get a little scared of my oil temps sometimes, but my coolant temps have never been TOO alarming.
FWIW...when the ambient drops to 95ish, my coolant temps hover around 89C with the A/C on and my oil temps around 105C... The extra 15 degrees ambient temperature is HUGE!
08-24-06 | 06:47 PM
#28
Originally Posted by RCCAZ 1
I've run my car in both configurations (single and dual oil coolers) and I can tell you that with dual oil coolers your oil temps will parallel you water temps pretty closely, maybe even be cooler by a few degrees. With the single cooler configuration my oil temps were always 5 to 10C higher than my water temps and significantly higher if I got into traffic. Another added benefit is that my WATER temps came down about 3 to 5C once I installed the second oil cooler!
08-25-06 | 03:39 AM
#30
Thanks Kento. It seemed like the veterans were always repeating the same advice, so I thought it would help to gather everything and put it in one place. Much of the technical stuff came from members like yourself.
I hope this thread will teach new members the basics so people can keep enjoying these cars for a long time.
-s-
I hope this thread will teach new members the basics so people can keep enjoying these cars for a long time.
-s-
08-25-06 | 08:50 AM
#31
Originally Posted by Sgtblue
Wow. That's sort of good news...assuming your talking about the R1 dual set up and not aftermarket. I guess I never gave it alot of thought, but 5 to 10 deg. C. is pretty good. Just out of curiousity, were you running synthetic or mineral oil?
Last edited by RCCAZ 1; 08-25-06 at 08:52 AM.
10-03-06 | 02:08 PM
#32
Full Member
Joined: Jul 2005
Posts: 198
Likes: 0
From: Sweden
Im bumping this great thread, hope its ok...
I have the same question. What flow rate (GPM) is required if i install an electric water pump? What happens if it flows to much?
Originally Posted by icydude
what does the stock water pump flow?
I have the same question. What flow rate (GPM) is required if i install an electric water pump? What happens if it flows to much?
10-24-06 | 12:48 PM
#34
I found a great website this week, and thought you guys would want to see it:
http://www.stewartcomponents.com/Tech_Tips.htm
icydude and zebb,
According to this website, and every Mechanical Engineer that I've spoken with, increased coolant flow is a good thing for heat transfer. To measure the flow rate of our water pump, you would need to buy some extra radiator hose, and measure how long it takes to fill a 5 gallon bucket. Here's a quick explanation that I found on google:
http://www.advancedh2o.com/technical...flow_rate.html
There are a few things to consider:
1.) Our system is a closed system, so be sure you've got a second bucket full of water for the pump to pull from.
2.) The thermostat will be closed when the water temperature is below 180F, so you I'd recommend using a "gutted" spare thermostat in order to perform a flow rate test.
3.) The water pump speed will be proportional to engine RPM. You'll need an assistant to hold the throttle if you want to measure flow rates at various RPMs.
I wish I had the time to do this myself, I might get around to it this summer...
-s-
http://www.stewartcomponents.com/Tech_Tips.htm
icydude and zebb,
According to this website, and every Mechanical Engineer that I've spoken with, increased coolant flow is a good thing for heat transfer. To measure the flow rate of our water pump, you would need to buy some extra radiator hose, and measure how long it takes to fill a 5 gallon bucket. Here's a quick explanation that I found on google:
http://www.advancedh2o.com/technical...flow_rate.html
There are a few things to consider:
1.) Our system is a closed system, so be sure you've got a second bucket full of water for the pump to pull from.
2.) The thermostat will be closed when the water temperature is below 180F, so you I'd recommend using a "gutted" spare thermostat in order to perform a flow rate test.
3.) The water pump speed will be proportional to engine RPM. You'll need an assistant to hold the throttle if you want to measure flow rates at various RPMs.
I wish I had the time to do this myself, I might get around to it this summer...
-s-
10-24-06 | 01:37 PM
#35
2/4 wheel cornering fiend
Joined: Nov 2002
Posts: 3,090
Likes: 3
From: Pasadena, CA
Originally Posted by scotty305
According to this website, and every Mechanical Engineer that I've spoken with, increased coolant flow is a good thing for heat transfer.
Cavitation is one of the reasons that underdrive pulleys were developed. Sustained high-rpm operation sometimes causes cavitation at the pump, drastically reducing efficiency. Of course, they were made for racing (sustained high rpm), which is why they're not for street use.
Last edited by Kento; 10-24-06 at 01:40 PM.
10-25-06 | 04:26 PM
#36
Originally Posted by Kento
It is, but within limits. You need to be careful of cavitation occurring in areas where the coolant fittings and jackets aren't shaped for that flow. Cavitation means bubbles, which means less heat transfer.
Cavitation is one of the reasons that underdrive pulleys were developed. Sustained high-rpm operation sometimes causes cavitation at the pump, drastically reducing efficiency. Of course, they were made for racing (sustained high rpm), which is why they're not for street use.
Cavitation is one of the reasons that underdrive pulleys were developed. Sustained high-rpm operation sometimes causes cavitation at the pump, drastically reducing efficiency. Of course, they were made for racing (sustained high rpm), which is why they're not for street use.
10-25-06 | 06:50 PM
#37
2/4 wheel cornering fiend
Joined: Nov 2002
Posts: 3,090
Likes: 3
From: Pasadena, CA
Originally Posted by a3dcadman
Wouldnt cavitation be minimal in a closed cooling system that has been properly burped and has an AST in place?
10-25-06 | 07:00 PM
#38
Also, the water has to sit in the radiator for a hot-second before moving on just to exchange some heat.
What I don't know is if any pump is so strong to even challange this fact.
For the newbs, good ducting (through the radiator) and a wide mouth are the best cooling mods ever!
What I don't know is if any pump is so strong to even challange this fact.
For the newbs, good ducting (through the radiator) and a wide mouth are the best cooling mods ever!
Last edited by rajeevx7; 10-25-06 at 07:03 PM.
10-25-06 | 07:13 PM
#39
2/4 wheel cornering fiend
Joined: Nov 2002
Posts: 3,090
Likes: 3
From: Pasadena, CA
Originally Posted by rajeevx7
Also, the water has to sit in the radiator for a hot-second before moving on just to exchange some heat.
What I don't know is if any pump is so strong to even challange this fact.
What I don't know is if any pump is so strong to even challange this fact.
10-25-06 | 07:14 PM
#40
Mentos and Magnums
Joined: Apr 2005
Posts: 3,373
Likes: 0
From: FLROIDUH
My freind was saying his car runs fine and doesnt overheat one bit but the coolant bubbles after shutdown sometimes on a long ride or a hard one. even with some cooldown time/ light driving. does this matter? I havent really seen this in my car. what is the difference. we both have r models and factory cooling systems.
10-25-06 | 07:26 PM
#41
Rotary Freak
Joined: Jan 2004
Posts: 1,899
Likes: 0
From: tampa
it is the drawing/pushing of the wp impellers that cause cavitation. just like the low pressure spot behind a truck, it takes time for the coolant to catch up behind the impeller, which leaves space which then collapses and so on..... blade design is most important
10-26-06 | 02:25 AM
#42
rajeevx7, I'd like to see data showing that increased coolant flow will make the system less efficient. Everything I've seen and read points to the opposite effect: a higher flow rate will transfer MORE heat. (this goes both for coolant flow and airflow across the radiator)
burnoutking999, I would guess that your system is holding pressure better than your friend's car. He might want to replace his pressure caps.
I found a nice photo of cavitation on google:
http://www.marin.nl/Faciliteiten/Lar...on_Tunnel.html
Note that cavitation can damage the blades of the water pump as well. Mazdaspeed recommends using underdrive pulleys and gutting the thermostat if you're going to race an RX-7.
-s-
burnoutking999, I would guess that your system is holding pressure better than your friend's car. He might want to replace his pressure caps.
I found a nice photo of cavitation on google:
http://www.marin.nl/Faciliteiten/Lar...on_Tunnel.html
Note that cavitation can damage the blades of the water pump as well. Mazdaspeed recommends using underdrive pulleys and gutting the thermostat if you're going to race an RX-7.
Originally Posted by 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/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/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.
-s-
10-26-06 | 11:48 AM
#43
Big Snail
Joined: Dec 2001
Posts: 1,230
Likes: 3
From: San Antonio
That makes sense, hence the need to upgrade the OE radiator to a two pass or even three pass setup. I live in south Texas with 100+ Degree weather and with my drilled OE thermostat, Koyo radiator, water temp gauge, and fan mod I never have over heating problems. I also run a 70/30 mix of coolant, of course 70 percent being distilled water. I think the key is proper preventive maintenance (which mainly consist of reliability mods) and simply watching your water temp gauge. Lets face it the FD is not a Honda Civic, in other words its not a car that you can simply jump in and drive without paying attention to your instrumentation.
Originally Posted by scotty305
rajeevx7, I'd like to see data showing that increased coolant flow will make the system less efficient. Everything I've seen and read points to the opposite effect: a higher flow rate will transfer MORE heat. (this goes both for coolant flow and airflow across the radiator)
burnoutking999, I would guess that your system is holding pressure better than your friend's car. He might want to replace his pressure caps.
I found a nice photo of cavitation on google:
http://www.marin.nl/Faciliteiten/Lar...on_Tunnel.html
Note that cavitation can damage the blades of the water pump as well. Mazdaspeed recommends using underdrive pulleys and gutting the thermostat if you're going to race an RX-7.
-s-
burnoutking999, I would guess that your system is holding pressure better than your friend's car. He might want to replace his pressure caps.
I found a nice photo of cavitation on google:
http://www.marin.nl/Faciliteiten/Lar...on_Tunnel.html
Note that cavitation can damage the blades of the water pump as well. Mazdaspeed recommends using underdrive pulleys and gutting the thermostat if you're going to race an RX-7.
-s-
10-26-06 | 02:50 PM
#44
Originally Posted by Kento
Not necessarily. All it takes is a high enough flow over a surface that creates turbulence. Just because the system is pressurized doesn't mean that it cannot happen. Note that submarine propellers still suffer from cavitation even when under the super-high pressure of deep water. Again, it's the reason that underdrive pulleys were developed; the water pumps weren't designed to spin that fast, so they developed cavitation at sustained high rpm.
Been a very long time since I studied these subjects, so Im relying on memory and as Ive gotten older, CRS has set in (Cant Remember ****). I should probably break out the old textbooks from school and bone up on fluid dynamics and STP studies. Or I can rely on you young bright guys for enlightenment.
Kento, thanks for your input and clarification.
Scott, you have done an exemplary job putting this thread together. Did you get my last email regarding the datalog info you needed?
-chuck
Last edited by a3dcadman; 10-26-06 at 02:55 PM.
10-26-06 | 04:05 PM
#45
Originally Posted by a3dcadman
I understand a little about boundary layer separation creating turbulence in the form of swirling vortices. These vortices would disrupt optimum flow through the cooling system in proximity of the water pump impeller. What Im a unclear about is the bubbling. Is this phenomenom from suspended air pockets being agitated creating smaller and smaller bubbles throughout the coolant. I can see how this could create conditions conducive to cavitation. This takes me back to my original question re: sealed hi pressure burped system with AST for purging air pockets.
Been a very long time since I studied these subjects, so Im relying on memory and as Ive gotten older, CRS has set in (Cant Remember ****). I should probably break out the old textbooks from school and bone up on fluid dynamics and STP studies. Or I can rely on you young bright guys for enlightenment.
Kento, thanks for your input and clarification.
Scott, you have done an exemplary job putting this thread together. Did you get my last email regarding the datalog info you needed?
-chuck
Been a very long time since I studied these subjects, so Im relying on memory and as Ive gotten older, CRS has set in (Cant Remember ****). I should probably break out the old textbooks from school and bone up on fluid dynamics and STP studies. Or I can rely on you young bright guys for enlightenment.
Kento, thanks for your input and clarification.
Scott, you have done an exemplary job putting this thread together. Did you get my last email regarding the datalog info you needed?
-chuck
10-26-06 | 05:07 PM
#46
Full Member
Joined: Jul 2005
Posts: 198
Likes: 0
From: Sweden
Good info, thx.
Im thinking of installing a Davies Craig EWP, but i really dont know if there is any good alternatives. I need some kind of easy-to-adjust thermostat. A complete kit (like the Davies Craig) would be nice.
Is there someone with experience of other waterpump/thermostat setups here?
Im thinking of installing a Davies Craig EWP, but i really dont know if there is any good alternatives. I need some kind of easy-to-adjust thermostat. A complete kit (like the Davies Craig) would be nice.
Is there someone with experience of other waterpump/thermostat setups here?
10-26-06 | 05:25 PM
#47
Originally Posted by herblenny
Good question chuck.. I'm curious about this too. as cavitation I understand is when the water pump blade is spinning so quick that the water is no longer being moved. Not really because its creating "bubbles"...
Locally, cavitation erodes the blades because the vapor bubbles contract back to liquid water with tiny implosions. These implosions will erode high strength materials like stainless steel. In the large hydroelectric plants where I worked, it was very clearly audible sorta like pinging in a piston engine.
Cavitation signals the limit of the useful range of the water pump, past which the pumping efficiency goes way down. It's not a hard limit, but it's important.
Dave
Last edited by dgeesaman; 10-26-06 at 05:30 PM.
10-26-06 | 05:27 PM
#48
Originally Posted by a3dcadman
Wouldnt cavitation be minimal in a closed cooling system that has been properly burped and has an AST in place?
10-26-06 | 05:39 PM
#49
-If cavitation is indeed a problem, one way to limit it would be to increase the system pressure.
-The info on the Mazdaspeed site is for RX-7's in general, so it's possible that our cars don't even have cavitation issues to start with.
-Measuring flow rates at various RPMs would let you know if you're cavitating at high RPMs: flow rate should increase with RPMs. If the RPMs increase but flow decreases, your impeller blades are probably causing cavitation.
Chuck (a3dcadman), sent you a PM regarding datalogging.
-s-
-The info on the Mazdaspeed site is for RX-7's in general, so it's possible that our cars don't even have cavitation issues to start with.
-Measuring flow rates at various RPMs would let you know if you're cavitating at high RPMs: flow rate should increase with RPMs. If the RPMs increase but flow decreases, your impeller blades are probably causing cavitation.
Chuck (a3dcadman), sent you a PM regarding datalogging.
-s-
10-26-06 | 08:20 PM
#50
2/4 wheel cornering fiend
Joined: Nov 2002
Posts: 3,090
Likes: 3
From: Pasadena, CA
Originally Posted by scotty305
-If cavitation is indeed a problem, one way to limit it would be to increase the system pressure.
Originally Posted by scotty305
-The info on the Mazdaspeed site is for RX-7's in general, so it's possible that our cars don't even have cavitation issues to start with.
Originally Posted by scotty305
-Measuring flow rates at various RPMs would let you know if you're cavitating at high RPMs: flow rate should increase with RPMs. If the RPMs increase but flow decreases, your impeller blades are probably causing cavitation.
All I'm getting at with all this is that you have to exercise caution in trying to increase internal coolant flow rates. I know it's not your intention, but it needs to be mentioned that it's not as simple as just spinning the water pump impeller faster and faster to get a cooler-running engine.