Miata cooling system thread
#861
In adding to the turbo coolant question, after noticing a boiling sound near my turbo, even after a 5 minute idle after only a mild street drive, I instrumented my turbo outlet line. If I stopped the engine for 2 minutes, when I started it back up the turbo coolant line was reading 120C!
I was confused when on track, my coolant temperature from the turbo was reading less than the main coolant temp reported by the ECU. But now that I've measured a difference front to back of head in terms of coolant of 5-7C hot, this makes more sense as this would suggest 3-5C rise in the turbo coolant temperature as it passes through the turbo.
It does seem that the logical thing would be to take a little amount of post water pump but pre block coolant that is cold and high pressure and return it to the head, pre stat, that way it can get controlled by the stat and go to the radiator. Has anyone tried this?
Also, how much heater coolant flow is there even with a fully open thermostat? It looks to me like there would be quite a lot. Can anyone quantify how much? A thermostatically controlled heater valve seems like it would make sense to improve radiator efficiency. (the one that measures the difference between heater outlet and inlet, and if both are hot and not delta, shuts off flow).
I was confused when on track, my coolant temperature from the turbo was reading less than the main coolant temp reported by the ECU. But now that I've measured a difference front to back of head in terms of coolant of 5-7C hot, this makes more sense as this would suggest 3-5C rise in the turbo coolant temperature as it passes through the turbo.
It does seem that the logical thing would be to take a little amount of post water pump but pre block coolant that is cold and high pressure and return it to the head, pre stat, that way it can get controlled by the stat and go to the radiator. Has anyone tried this?
Also, how much heater coolant flow is there even with a fully open thermostat? It looks to me like there would be quite a lot. Can anyone quantify how much? A thermostatically controlled heater valve seems like it would make sense to improve radiator efficiency. (the one that measures the difference between heater outlet and inlet, and if both are hot and not delta, shuts off flow).
#863
I'm not suggesting anyone block off their heater lines entirely!
#864
Yes, but I thought there was a heater flow control valve that was both thermostatic (ie it won't open until the engine stat opens) and it also only closes when both the heater lines are at the same temperature, ie it will open if the heater is on and the coolant in the heater out is cooler than the heater in.
I'm not suggesting anyone block off their heater lines entirely!
I'm not suggesting anyone block off their heater lines entirely!
Coolant boiling in the turbo after shutdown is pretty normal as the heat soaks out of the exhaust housing/manifold, etc. AFAIK the only way to avoid it is an electric coolant afterrun pump like some OEMs use.
--Ian
#865
So few that come here are willing to actually work to gain an understanding and just want to be spoon fed. You seem to contribute as much info as you gain. Welcome.
/drift
__________________
#866
Gaining that extra delta at the top of the rad is great.
Also, no miata has a valve for the heater, its always-on, although some people do rig valves (manual or otherwise) to bypass it for various reasons (reducing cabin heat in the summer or on track for instance, since the heater isnt perfectly sealed to the cabin)
RE: thermostat, I actually see below opening temperature (~87-88C) after a while of cruising on the highway, with oil temps ~90C on a ~24C ambient day using QMAX, good ducting and ebay 52mm rad. When speeds drop it quickly shoots up to 91-92C.
I do like this thermostat on the street, especially with the stock engine as you are running the engine within the optimal temperature for the tolerances it was designed with (reduced blowby etc..),
The 180F has a few advantages on track for those with insuficient cooling capacity (not everyone is willing or able to run one or more of: crossflow/hood vents/reroute), this thermstat will allow a cooling lap to reduce temperatures well below 91C to allow a longer run time before needing to do it again (and for 20m sessions, perhaps one lap is enough).
Last edited by lbatalha; 07-04-2019 at 06:18 AM.
#867
It is true that running a 180 tstat will give a car that tends to overheat, a great greater "thermal battery" capacity. But because of our background in longer events, we have always engineered for steady-state capacity which means not allowing it to overheat, even for short bursts.
__________________
#868
According to our Garrett contacts, the water flow through the turbo isn't all that important during operation - and after shutdown, the water circulates by thermal siphoning. Thus the noise. What would be really interesting would be to cut off off the water flow to the turbo during operation and only open it up (pumped or otherwise) after shutdown.
#869
On an entirely separate note, I just wanted to thank you for your contributions to the forum. You research, ask questions, have good knowledge of certain areas, collect and share data and are open minded to options for setting up your project.
So few that come here are willing to actually work to gain an understanding and just want to be spoon fed. You seem to contribute as much info as you gain. Welcome.
/drift
So few that come here are willing to actually work to gain an understanding and just want to be spoon fed. You seem to contribute as much info as you gain. Welcome.
/drift
My car is an awful lot better than it otherwise would have been thanks to this forum (and a lot of your contributions), so sharing my data and helping others to do likewise is the least I can do. Also, finding like minded individuals is nice bonus. I should probably start an actual build thread to keep the information in one place.
#871
A properly configured cooling system with an expansion tank also has the advantage of eliminating coolant flow drop at high TW. The outlet of the expansion tank outlet should connect to the water pump inlet and the air volume is in the expansion tank. The cap only acts as an emergency bleed, and it's the defined air volume in the exp. tank which regulates the system pressure. As the coolant heats up it expands and also heats up the air. Since PV=nRT, the volume is fixed so the pressure must increase if temp increases. This applies pressure at the water pump inlet, which is where the cavitation is occurring. Curiously, I've seen a few OEM's use an expansion tank and not take advantage of this. Depending on the cooling system, you can see as much as 20% flow drop due to cavitation between like 80C and 115C.
Last edited by engineered2win; 07-03-2019 at 10:05 PM.
#872
And/or an expansion tank. The expansion tank needs to be the highest point in the system. A line from the turbski runs to the inlet of the expansion tank and allows for natural convection and the tank deaerates the coolant. When you shut the car off you can hear bubbling in the expansion tank.
A properly configured cooling system with an expansion tank also has the advantage of eliminating coolant flow drop at high TW. The outlet of the expansion tank outlet should connect to the water pump inlet and the air volume is in the expansion tank. The cap only acts as an emergency bleed, and it's the defined air volume in the exp. tank which regulates the system pressure. As the coolant heats up it expands and also heats up the air. Since PV=nRT, the volume is fixed so the pressure must increase if temp increases. This applies pressure at the water pump inlet, which is where the cavitation is occurring. Curiously, I've seen a few OEM's use an expansion tank and not take advantage of this. Depending on the cooling system, you can see as much as 20% flow drop due to cavitation between like 80C and 115C.
A properly configured cooling system with an expansion tank also has the advantage of eliminating coolant flow drop at high TW. The outlet of the expansion tank outlet should connect to the water pump inlet and the air volume is in the expansion tank. The cap only acts as an emergency bleed, and it's the defined air volume in the exp. tank which regulates the system pressure. As the coolant heats up it expands and also heats up the air. Since PV=nRT, the volume is fixed so the pressure must increase if temp increases. This applies pressure at the water pump inlet, which is where the cavitation is occurring. Curiously, I've seen a few OEM's use an expansion tank and not take advantage of this. Depending on the cooling system, you can see as much as 20% flow drop due to cavitation between like 80C and 115C.
#873
My current cooling system- Stock WP, 20psi radiator cap, FM crossflow from 2016, FM Stage 2 Fans, OEM 2002 coolant routing, minimal ducting but aluminum under tray is installed, 70/30 distilled water/coolant, 185F thermostat
Problems- My car runs generally hotter than I would like to see city driving (210-220) and will hit 230 in stop and go traffic when using AC.
Upgrade path:
1. FM reroute, leave everything else the same.
2. TSE radiator and the recommended single spal fan for ac cars.
What route do you think I should take here? I don't mind spending the cash on the TSE I just cant believe I don't see other people having this problem. Maybe less people have AC turbo street cars than I think.
Thinks I wont do:
Hood vents
Problems- My car runs generally hotter than I would like to see city driving (210-220) and will hit 230 in stop and go traffic when using AC.
Upgrade path:
1. FM reroute, leave everything else the same.
2. TSE radiator and the recommended single spal fan for ac cars.
What route do you think I should take here? I don't mind spending the cash on the TSE I just cant believe I don't see other people having this problem. Maybe less people have AC turbo street cars than I think.
Thinks I wont do:
Hood vents
#874
mkturbo.com
iTrader: (24)
Join Date: May 2006
Location: Charleston SC
Posts: 15,177
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My current cooling system- Stock WP, 20psi radiator cap, FM crossflow from 2016, FM Stage 2 Fans, OEM 2002 coolant routing, minimal ducting but aluminum under tray is installed, 70/30 distilled water/coolant, 185F thermostat
Problems- My car runs generally hotter than I would like to see city driving (210-220) and will hit 230 in stop and go traffic when using AC.
Upgrade path:
1. FM reroute, leave everything else the same.
2. TSE radiator and the recommended single spal fan for ac cars.
What route do you think I should take here? I don't mind spending the cash on the TSE I just cant believe I don't see other people having this problem. Maybe less people have AC turbo street cars than I think.
Thinks I wont do:
Hood vents
Problems- My car runs generally hotter than I would like to see city driving (210-220) and will hit 230 in stop and go traffic when using AC.
Upgrade path:
1. FM reroute, leave everything else the same.
2. TSE radiator and the recommended single spal fan for ac cars.
What route do you think I should take here? I don't mind spending the cash on the TSE I just cant believe I don't see other people having this problem. Maybe less people have AC turbo street cars than I think.
Thinks I wont do:
Hood vents
#875
My current cooling system- Stock WP, 20psi radiator cap, FM crossflow from 2016, FM Stage 2 Fans, OEM 2002 coolant routing, minimal ducting but aluminum under tray is installed, 70/30 distilled water/coolant, 185F thermostat
Problems- My car runs generally hotter than I would like to see city driving (210-220) and will hit 230 in stop and go traffic when using AC.
Upgrade path:
1. FM reroute, leave everything else the same.
2. TSE radiator and the recommended single spal fan for ac cars.
What route do you think I should take here? I don't mind spending the cash on the TSE I just cant believe I don't see other people having this problem. Maybe less people have AC turbo street cars than I think.
Thinks I wont do:
Hood vents
Problems- My car runs generally hotter than I would like to see city driving (210-220) and will hit 230 in stop and go traffic when using AC.
Upgrade path:
1. FM reroute, leave everything else the same.
2. TSE radiator and the recommended single spal fan for ac cars.
What route do you think I should take here? I don't mind spending the cash on the TSE I just cant believe I don't see other people having this problem. Maybe less people have AC turbo street cars than I think.
Thinks I wont do:
Hood vents
1) Air in system
2) Head gasket
3) Bad radiator cap
4) pinhole leak somehwere
Are you losing any coolant? When's the last time you checked.
#876
1. My burping procedure is as above so I think I should be air free, also with a few thousand miles since I last flushed coolant I would expect any minor bubbles left to have been worked out.
2. No signs of a head gasket. Oil comes out coolant free, coolant in overflow is clean and car makes good power. No white smoke out of exhaust.
3. Just swapped from the one FM supplies to a 20PSI CSF unit same results with both.
4. I'm not loosing any visible amount of coolant. No spots under the car ever, no signs of it in the engine bay, overflow pretty much always at the same level.
I should mention crusing the highway or backroads is fine the only time I experience these heat issues is when using the AC in stop and go traffic. Even on track my temps stay pretty cool for a long time and improving that is just a ducting issue which I am waiting to address.
Edit: To confirm the pinhole leak/headgasket theory I'll rent a radiator pressure tester this weekend and see if it holds pressure.
Last edited by BBro; 10-09-2019 at 01:38 PM.
#877
mkturbo.com
iTrader: (24)
Join Date: May 2006
Location: Charleston SC
Posts: 15,177
Total Cats: 1,681
HF sales a radiator pressure testing setup for a reasonable price.
For burping my cars, I jack up the front as high as I can. I then put on the magic funnel and fill it mostly up. Then run the car until the fans cycle on and off 3 times. Then I let the car cool. Once cool I put the radiator cap back on. Then I usually cycle the fans a few more times and check fluid levels.
If you are going to ad a reroute I would suggest the QMax. Mostly because I have found it the easiest to install on a miata with the engine installed.
For burping my cars, I jack up the front as high as I can. I then put on the magic funnel and fill it mostly up. Then run the car until the fans cycle on and off 3 times. Then I let the car cool. Once cool I put the radiator cap back on. Then I usually cycle the fans a few more times and check fluid levels.
If you are going to ad a reroute I would suggest the QMax. Mostly because I have found it the easiest to install on a miata with the engine installed.
#879
This winter I was going to do the QMax and switch to DH20 and wetter water