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Help me understand Re-medy thermostat and earlier fan activation for track cars...
I'm just trying to wrap my head around these cooling "upgrades" and how they relate to a track car that has an upgraded radiator and shrouding/sealing. I have a well-ducted CSF aluminum radiator that should be able to maintain 205F once the OEM T-stat is fully open.
1. Lower temperature Re-medy thermostat. A lower temperature thermostat can only start the flow of coolant sooner, it does not solve overheating issues once it is fully open. With enough radiator and ducting, this T-stat could reduce the steady state operating temperature on-track.
Q: Is it preferred and recommended to operate the renesis at a lower temperature for track driving, or is the OEM fully open temperature of 205F okay for engine power & longevity?
2. Earlier fan activation. For example, #1 fan now turns on at 190F (stock - 207F) and #2 fan turns on at 194F (stock - 214F).
Q: If you have the OEM t-stat, which opens at 180-203F, and you modify the fans to activate earlier, wouldn't #1 fan (190F) be frequently be running before the T-stat is even fully open (203F)? Or does the RX-8 look at the vehicle speed (VSS) and not run the fans when the car is moving above a certain speed?
For reference, according to the "Renesis Engine Tutorial" dated 2 Aug 2012 for the Star Mazda Racing series, posted somewhere on this forum:
Oil: 190-230F operating range, target of 200F and a terminal temp of 250F before the coolers.They quote a 30F rise in temperature through the engine, so keep in mind where you're measuring and adjust accordingly.
Water: 180-220F operating range with a terminal temp of 240F.
205F is a great temp. I don't think it'll do any harm. Pretty cool if you can stay there. Most of us can't.
Just a little clarification, both fans turn on at the same time. What you changed is the low and high speed temps. Both fans turn on low, and then both go on high
Even I wanna know if the car turns off the fans when moving. Been asking that for ages on here.
Even I wanna know if the car turns off the fans when moving. Been asking that for ages on here.
I have actually tested this by hooking up a lightbulb to the fan relay . So I can confirm that the fans do stay on at speed once their turn on temp has been reached.
Fan activation .... I was not aware that the Tstat wasn't fully open till 205 but have always reasoned that the fans should never be turned on at a temp below which the engine would normally run under cruise conditions . I set my first stage to activate at 195 FWIW.
As far as the thermostat goes ... I never was a fan of one that opens earlier than stock except perhaps on a dedicated race car ...even then I struggle to see any benefit.
the thermostat and early fan on are great for the street, and do help if you have enough radiator.. on track neither matter, it is size and efficiency of radiator and ambient temp.
i have all four. early fan on. 180 thermostat. remedy h2o pump.. and remedy big *** radiator. around town when i do that, no matter what the outside temp.. runs ~180 to 185. on track as soon as outside temp hits 95 my temps run 200 to 220 depending on track.. but on the cool down lap they are back to 180..
This makes me NOT want to get the racing beat flash if I use the OEM T-stat, because then the fans will be fighting to keep the engine cool before the thermostat is even fully open. seems like a waste of energy.
This makes me NOT want to get the racing beat flash if I use the OEM T-stat, because then the fans will be fighting to keep the engine cool before the thermostat is even fully open. seems like a waste of energy.
Doesn't work out that way ..... while the thermostat might not be fully open , it doesn't need to be to get enough flow through it to cool the engine below the fan set point.
i got off the phone with Jim at RB. He provided some feedback that cleared some thoughts up and confirmed some others:
1. While the OEM T-stat might open at 180F and be fully open at ~203F, it is flowing the majority of its capacity quite early on, even if it may not be fully open. So perhaps it is doing ~80% of the flow rate when the RB fans would first be kicking on.
2. The lower fan activation could be good for stop-and-go traffic, drag racing, and for autocross situations, where you are heat soaking and then trying to recover with fans.
3. He said that the fans will indeed be running at highway and above speeds such as a road course when the coolant temperatures exceed the settings. While he said the fans might not actually help much in this situation, you don't loose much power from doing so.
i'm not interested in a tunable solution such as the cobb AP, but i'm looking to optimize the midpipe and single exit exhaust for track use. the RB V2 flash seems like a good option and provides good gains (Team had posted dynos back in the day).
going forward i think i will go with the OEM T-stat (won't be my limiting cooling factor) and the RB flash (despite my disagreements with the fan set points).
I have actually tested this by hooking up a lightbulb to the fan relay . So I can confirm that the fans do stay on at speed once their turn on temp has been reached.
Fan activation .... I was not aware that the Tstat wasn't fully open till 205 but have always reasoned that the fans should never be turned on at a temp below which the engine would normally run under cruise conditions . I set my first stage to activate at 195 FWIW.
As far as the thermostat goes ... I never was a fan of one that opens earlier than stock except perhaps on a dedicated race car ...even then I struggle to see any benefit.
GREAT! So that's one myth down. The fans don't only turn on when moving slowly. They can turn on even at speed if it's over the trigger temp.
I don't know if this happens to you guys, but when I'm stuck in traffic for over an hour, my car goes into some kind of "fail safe" mode. The fans stay on, all the time! Even when the temp drops to 190F, it stays on high speed. Restarting the car won't fix it. If I let it sit for 20 mins and start it back up, that'll bring the fans back to it's normal behavior.
I don't know if this happens to you guys, but when I'm stuck in traffic for over an hour, my car goes into some kind of "fail safe" mode. The fans stay on, all the time! Even when the temp drops to 190F, it stays on high speed. Restarting the car won't fix it. If I let it sit for 20 mins and start it back up, that'll bring the fans back to it's normal behavior.
Weird.
I've never tested it, but it could be that the fan relays have a deadband built in so they don't cycle on and off constantly. For example, the temps may need to drop 5-10 deg. or so below the 'on' point before turning off the fans.
Try letting the temps drop lower and see if the fans shut off at some point.
ETA: I have a fan relay kit that lowers the on point for both fans to about 185. It has a huge deadband- 20 deg! My temps actually get too low; the fans don't turn off until 165.
T-stat and Fans are good for the street, but yeah, not so much help on the track. At speed, fans shut off. And you get more air in from the ram effect. Tstat is the same, once open, it is open. What can help is the remedy water pump, or a rather severe underdrive pulley for the water pump. The stock pump will cavitate above about 7,500 RPM. There are some very cool religious wars in this forum someplace, including CFD analysis and witch doctor chants. You can slow it down or get a better impeller. I chose the water pump, problems immediately went away. Lower speed may give you issues with heat in the winter. I am sorting that one. Likely will mess with a valve to replace the heater hose orifice.
I've never tested it, but it could be that the fan relays have a deadband built in so they don't cycle on and off constantly. For example, the temps may need to drop 5-10 deg. or so below the 'on' point before turning off the fans.
Try letting the temps drop lower and see if the fans shut off at some point.
ETA: I have a fan relay kit that lowers the on point for both fans to about 185. It has a huge deadband- 20 deg! My temps actually get too low; the fans don't turn off until 165.
Yeah my fans go on high at 213F and go back to low speed at 206F. But when this happens, they stay on high speed no matter how low the temp gets. I've seen the temps go down to around 183F. They were still on high speed. Very weird, but it keeps the temps really low! So it's harmless. If I stop the car and start it, fans turn on immediately. If I stop the car, let it cool down for say 15 mins and start, fans will only turn on at the correct turn on temps, or when the AC compressor is on.
And this only seems to happen when the fans have cycled on and off for over an hour (traffic in Colombo is insane). Maybe the ECU just thinks "screw it! I can't keep turning these on and off" and just runs the fans constantly?
Originally Posted by 04Green
T-stat and Fans are good for the street, but yeah, not so much help on the track. At speed, fans shut off.
We've just confirmed that the fans stay on even while moving if they're over the trigger temps.
From the Mazda's document "2009 Mazda RX-8 Service Highlights":
After an hour of traffic, I would guess your engine bay is heat soaked and it goes into after-cooling mode. However, I don't believe this applies when the engine is running. Maybe this has to do with the AC operation?
I don't have data to prove this, and it is on my list of data collection tasks for spring track days, but when I was at the track a few weeks ago in 92F ambient temps, I accidentally left my fans-on-low-mod switch on and noticed my peak temp was 4 to 5 degrees lower than it was with the switch off in an earlier session at the same ambient temp. The only "proof" I have is simply me glancing at my phone occasionally, so I could have it wrong due to timing. But, I hypothesize it may make a difference to run the fans constantly--even on low--when running relatively short (20 to 30 minute) sessions. I will log data in September to find out if it is true.
From the Mazda's document "2009 Mazda RX-8 Service Highlights":
After an hour of traffic, I would guess your engine bay is heat soaked and it goes into after-cooling mode. However, I don't believe this applies when the engine is running. Maybe this has to do with the AC operation?
Thanks Jastreb. I've seen that diagram before. If the temp is over 213.8F, the fans stay on only for 5 seconds when I turn off the car. It doesn't stay on for minutes. I think that only happens when the coolant temp is over 230F, or when the engine compartment temp is high.
It's not because of the AC. I've checked by turning off the AC while the fans are running constantly, and they're still on high speed. Could be high engine compartment temps like you said, but the diagram says it only happens when the engine is off
Are JDM cars programmed differently? I know another guy with an S1 who's fans also run constantly after sitting in traffic for a while.
Originally Posted by Steve Dallas
I don't have data to prove this, and it is on my list of data collection tasks for spring track days, but when I was at the track a few weeks ago in 92F ambient temps, I accidentally left my fans-on-low-mod switch on and noticed my peak temp was 4 to 5 degrees lower than it was with the switch off in an earlier session at the same ambient temp. The only "proof" I have is simply me glancing at my phone occasionally, so I could have it wrong due to timing. But, I hypothesize it may make a difference to run the fans constantly--even on low--when running relatively short (20 to 30 minute) sessions. I will log data in September to find out if it is true.
You logged it man! You posted up the log chart on one of my threads
Running the fans on high definitely lowers the coolant temp. You proved it, and I have personal experience when my car decides to run the fans on high all the time.
But still, even without jumping a relay or a fan kit, the fans will go into high speed at 213.8F and stay on until the temp drops back to 206F even while moving. For all this time we thought the fans turn off when the car is moving at speed. That's been proved wrong, thanks to Brettus.
Just a little theory I cooked up about the whole "after cooling" thingy.
This chart posted above is for S2s. After cooling happens only when the engine is off, when the coolant temp is over 230F, or when the engine compartment temp is high.
I think only S2 cars have an engine compartment temperature sensor. There is another chart for S1s, and it doesn't say anything about an engine compartment temp sensor. So, if it's happening to an S1, it's probably because the coolant temp was over 230F. I've read a lotta threads from 2004 about the fans staying on for ages after turning off the car. So that means these cars hit 230F even when they were new, with perfect cooling systems
Just a little theory I cooked up about the whole "after cooling" thingy.
This chart posted above is for S2s. After cooling happens only when the engine is off, when the coolant temp is over 230F, or when the engine compartment temp is high.
I think only S2 cars have an engine compartment temperature sensor. There is another chart for S1s, and it doesn't say anything about an engine compartment temp sensor. So, if it's happening to an S1, it's probably because the coolant temp was over 230F. I've read a lotta threads from 2004 about the fans staying on for ages after turning off the car. So that means these cars hit 230F even when they were new, with perfect cooling systems
There is a temp sensor in the engine bay on s1s .... it's next to the maf sensor
There is also the ambient temp sensor . Dunno if one of those triggers the cool down though.
But still, even without jumping a relay or a fan kit, the fans will go into high speed at 213.8F and stay on until the temp drops back to 206F even while moving. For all this time we thought the fans turn off when the car is moving at speed. That's been proved wrong, thanks to Brettus.
To be precise .... I tested the low fan speed relay .. Maybe I should test the high speed relay as well !
Tstat is the same, once open, it is open. What can help is the remedy water pump, or a rather severe underdrive pulley for the water pump. The stock pump will cavitate above about 7,500 RPM. Lower speed may give you issues with heat in the winter. I am sorting that one. Likely will mess with a valve to replace the heater hose orifice.
I chose to go with a rather strong water pump and alternator underdrive so that I could retain OEM water pump (spares are easy to come by if I'm 8 hours away at road Atlanta). There are pros and cons to each. I saw a dyno from the remedy pump, and because it actually pushes so much water, there was a power loss until high rpms where the factory pump cavitated, and then it made gains. The water pump underdrive should produce gains throughout the operating range and solve or greatly reduce the high rpm cavitation. The disadvantage may be low-rpm cooling... but then, my most severe thermal loads are generally while tracking. I guess stop-and-go might result in the fans having to run more with the underdrive.
http://www.rx8performance.com/produc...rmance-pullies
"Comparing temperatures at the end of each dyno run via the Cobb AP showed 184-187f with our RX8performance pulleys compared to 197-199f for the stock pulleys! Clearly a noticeable temperature difference even for the time required for dyno runs!" Could be marketing BS, but I'm willing to give them a try.
I'm also looking at installing the heater hose orifice to get rid of my high rpm bubbles sound from the glovebox. Did you notice an impact to heating with that orifice?
07-14-2016, 05:29 AM
