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I track my car (RX8 6spd 2006) every weekend and I'm asking for advice about cooling.
Car is completely stock right now and when I'm driving hard on the track the temperatures under load are about 98 C, when braking or coming to a stop they rise as high as 101 C.
I'm thinking about the mishimoto lower temp thermostat because it would be fully open when under load not like the stock thermostat that's fully open at 95 C (temp I don't really want to hit).
What's your advice to stay at +-91 C when driving hard?
I can't promise you'll stay at 91C, that's just not reality, but there are things you can do to stay under 104 (which is where danger begins) while driving hard:
- Re-medy water pump
- Better rad (CSF and Koyo V-core have good reputations.. you can get fancier if you want to spend more
- check/increase the foam sealing around the radiator. There should be no loose foam or gaps for air to pass
By the way, 98-101 is about normal track temperature peak for an RX8. You don't need the thermostat. Depending on track speed and ambient conditions, the peak temperature will fluctuate. Some slower tracks can make the car run hotter than long, sweeping, faster ones.
My car peaks at 104C on the track under heavy load. I would back off at 105, but I have not reached it yet. 104 does not really worry me.
91C is not realistic for this car. You can get close to 95, but it requires a very expensive radiator and removal of your AC.
BTW, the stock thermostat is 82C, so it is fully open on the track.
Stock thermostat starts opening at 82C and is fully open at 95C. Bought the Mishimoto racing thermostat, fully open at 89C. Amazing difference. Yesterday on the track I was peaking at 94C in the corners, that doesn't rly bother me, what bothered me was when I braked into the corner the radiator couldn't keep up as the temperature rose. Now since it's fully open from 89C, when I brake into the corner the temperature peaks at 94C and that's constant high rpm driving.
The next problem of course is when I drive from the track into the pits and stop, then the temperatures start to rise until the fans start, so next thing I'm gonna do is a fan switch, just to manually start the fan when stopping. Cheers
Yeah. So, the stock thermostat is fully open on the track.
Anyway, unless your stock thermostat was faulty, or the Mishimoto flows more, the rest of your post does not compute. The thermostat sets the minimum operating temp of the coolant. It has no effect on peak temps.
Post some before and after data under similar ambient conditions.
you can set the high speed fans to stay on up to whatever speed you want . Probably somewhere around 60mph . Would be pointless above that I'm guessing .
Anyone experimented with this or any other means of keeping the fans on ?
Yeah. So, the stock thermostat is fully open on the track.
Anyway, unless your stock thermostat was faulty, or the Mishimoto flows more, the rest of your post does not compute. The thermostat sets the minimum operating temp of the coolant. It has no effect on peak temps.
Post some before and after data under similar ambient conditions.
It has effects on peak temps. You have more "cooling in reserve" for turns and braking when you slow down, therefore decrease airflow and it heats up. That was my problem, now its fixed.
The thermostat, outside of the two conditions l mentioned above, only affects peak temps, if you have excess cooling capacity. We know the stock cooling system in this car does not have any thermal efficiency to spare.
Thermostats do not react quickly enough to create "cooling in reserve" for short slow periods. Dip your old thermostat in a pot of boiling water and watch it in action. Thermostats open and close slowly.
This is all simple physics, and Mishimoto has not figured out how to defy the laws of thermodynamics.
In what ambient temp are you driving? If you are tracking the car under 20C ambient, I suppose I can see it, but otherwise nope.
Edit:
Let's look at this visually. Here is a chart of my coolant temps during a 20 minute session on a 100F day. Crazy, I know. Let's say I had a 169F thermostat, instead of a 180F thermostat. What you are trying to tell me is, the entire graph would shift down 11F. And, what I am saying is, it absolutely will not, because my 180F thermostat is fully open the whole time I am out there. You can actually see where it closes near the end of the line.
An extreme example, you say? Here is a similar chart from an 88F session. Same result. Thermostat is always fully open.
Wait. How did it dip down below 180F both times? Because, thermostats are slow to close.
I can dig up data from cooler days and graph it, but it will show peak temps at or over 200F and a fully open thermostat.
.
Last edited by Steve Dallas; 07-13-2017 at 09:16 AM.
Yah, a lower temp tstat will only be beneficial if your coolant temps actually get back down to your baseline tstat temperature. If your temps never get back down there, then it's moot. If they do, then it's probably worthwhile.
Also also, not all tstats are the same. The FSM says the initial opening temp should be 176-183°F. After I installed a new OEM tstat and CSF 3164 radiator last year and base winter temps (<30°F ambient) at highway speeds went from 180°F to 175°F (it wiggles between 174-176). At 90°F ambient I hover around 180°F coolant temps at highway speeds. I don't know how many mm of lift my tstat exhibits at 4°F above "closed" but it's enough flow to keep the engine cool under those conditions.
Last edited by NotAPreppie; 07-13-2017 at 09:22 AM.
Also the heating up heading to the pits doesn't super make sense. That would mean the cooling system isn't keeping up with a lower load than you just had the entire time on track. If that were true, you would be overheating in regular city driving all the time.
Is your undertray and sealing foam around the rad all nicely attached? You need those, otherwise air is going around the rad and not through it.
Yeh, when driving into the pits after hard driving it heats up. I don't daily or city drive my rx8, it's track only. Ambient temp is +-30C. Tested it again yesterday, highest temp I reached was 93, when driving into the pits and idling 98C. I didn't trust the low temp thermostat too, but it fixed most of my problems, oem might have been faulty if u guys say that it doesn't help alot. BTW, what's the cause of eaten up thermostat housing? The edges look eaten out from water.
BTW, what's the cause of eaten up thermostat housing? The edges look eaten out from water.
Cavitation or acidity... or somebody changing the thermostat with sledgehammer
How old is the coolant and what coolant is it? You want Mazda FL22, changed every few years (depending on mileage..)
I would be surprised to see cavitation from flow in that area, but perhaps the coolant was boiling and that ate away at the metal at the level where the boil happens.
Have a picture?
And if it was boiling, the cooling system was not pressurized correctly.
I don't have a picture. Coolant was FL22 nice and clean and flushed it after swapping the thermostat. Cheers.
I meant the previous owner might have done something. Another reason this could happen is if someone ran tap water rather than deionized. If the water has minerals, you get electric current between different metals the coolant is in touch with, and the weakest of the metals (Al in this case) begins to erode.
Car was imported from a mountain area, I was checking out the grill today. Top half is hard plastic and the bottom is open right? I have a tin rubber there so the grill is closed completely, is this stock or has been done to deal with cold temperatures? (I'm new to rx8s)
Also the heating up heading to the pits doesn't super make sense. That would mean the cooling system isn't keeping up with a lower load than you just had the entire time on track. If that were true, you would be overheating in regular city driving all the time.
Is your undertray and sealing foam around the rad all nicely attached? You need those, otherwise air is going around the rad and not through it.
Originally Posted by kerrboiii
Yeh, when driving into the pits after hard driving it heats up. I don't daily or city drive my rx8, it's track only. Ambient temp is +-30C. Tested it again yesterday, highest temp I reached was 93, when driving into the pits and idling 98C. I didn't trust the low temp thermostat too, but it fixed most of my problems, oem might have been faulty if u guys say that it doesn't help alot. BTW, what's the cause of eaten up thermostat housing? The edges look eaten out from water.
Temps rising as you putter around the pits isn't that weird. You've got next to zero airflow at 5-10 MPH so yah, temps are going to rise until you hit the fan trigger temps.
With my RE-medy water pump and CSF radiator, I'm down below 190°F by the end of the cool down lap and from track exit to paddock to parking it climbs back up over 200°F again.
Nothing handy. I have a full day event on Monday so I'll have some then.
Track temp data.
This was at the 1.95 mile Blackhawk Farms Raceway in South Beloit, IL. Ambient temperature at the start of this session was a cool (for middle of July) 80°F.
Cooling system (in ascending order of likely impact):
9 month old OEM thermostat (opening temp on this one is on the bottom end of the spec at 176°F)
Mazda FL-22 flushed about 4 months ago
Mazmart RE-Medy water pump
CSF 3164 radiator with FAL 420 fans with foam on bottom and driver sides
Other mods that likely don't matter:
Sohn OMP adapter
Premixed 1oz/gallon
S2 gearbox
resonated midpipe of unknown origin with 200 cpi cat (throwing a P0420 code)
Tanabe Super Medallion Hyper catback
Enkei RPF-1 17x8 wheels with 245/40-17 Hankook R-S4 tires
<100 psi compression on front rotor
<90 psi compression on rear rotor
Last edited by NotAPreppie; 07-18-2017 at 10:40 AM.
Those numbers look damn near identical to mine. My fans turn on high at 204 and return to low at 196. 80F ambient is a pretty typical summer day for me as well but I don't think I ever get down to 188 at a light cruise, mainly due to my FMIC I'd think though.
Thanks for the graphs!
Last edited by RotaryMachineRx; 07-18-2017 at 09:58 AM.
07-08-2017, 12:01 PM
Cooling upgrade advice - track car
