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Ok, as an experiment I switched from waterless to 50/50 coolant. I'd been running waterless since replacing the engine, and wanted to track down some indications so I ran logs for a few days on a stock tune and swapped coolant halfway through. The results for cruising at 70mph after readings were stable:
50/50 vs Waterless
Coolant temp: 197 vs 206
EGT: Negligible difference.
Short term Fuel trim: .6 vs 1.7
Running vac: Negligible
Idle Vac: 22 vs 23.5
Although I will say that I didn't leave it running long to see if idle vac changed with the 50/50. I do know it stays about the same with waterless.
These are the conclusions I've drawn:
The internal temps for idle are directly related to engine vac, so the engine internals stay cooler at idle.
The engine appears to run cooler in cruise. I say that because the fuel trims did drop 1% going to 50/50 (hotter internals), however the EGT did not change. So it's a toss up.
What I will say is that running waterless is slightly better than regular coolant for actually keeping the internals cool even with the increased temperature, and it doesn't boil over so overheating is less of a concern.
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__________________
Quote:
Originally Posted by 9krpmrx8
Buying a used turbocharged RX-8 is like marrying a stripper, it very rarely ends well.
Quote:
Originally Posted by X7rotor
im starting to think a lot of rx8 guys are seriously up there own *** when it comes to thinking out the box.
Surely if it never boils, the situation would just go from bad to worse?
Steam pockets in the cooling jackets act as insulators causing rapidly and uncontrolled increases in localized temperatures. In addition to this catastrophic climb, there are also the pressure and other mechanical stressors associated with this boiling.
By preventing this, and as demonstrated in GT class racing where Evan ran insanely high compression ratios and much higher than normal coolant temperatures because even those elevated temperatures were controlled.
__________________
Driving the RX-8 is never about the numbers, it's about the experience and the experience of driving it is the best selling point in favour of it. If you drive it and there is a heart beating in your chest, I believe you WILL buy it. The tragedy is that too many talk themselves out of even trying it because of the numbers.
Yup, departure from nucleate boiling is the concern. As soon as a steam blanket forms the engine can quickly overheat.
If you fill waterless coolant with water and have greater than a 60/40 mix you get the worst of both worlds. Specific heat capacity of antifreeze and the boiling point of water. If you go down to 60/40 or less then you are in the realm of a normal coolant system.
The only concern is that Evans is expensive and hard to get quickly in a pinch. So I don't run Evans. If you look at the Evans NPG MSDs it is just a Ethylene Glycol/Propylene Glycol blend. They can claim magical pixie dust and the like, but it is what it is. I've been running straight EG may go to a EG/PG blend.
__________________
Quote:
Originally Posted by 9krpmrx8
Buying a used turbocharged RX-8 is like marrying a stripper, it very rarely ends well.
Quote:
Originally Posted by X7rotor
im starting to think a lot of rx8 guys are seriously up there own *** when it comes to thinking out the box.
The cooling system in this car needs help. I have finally ( after some years) developed a "package' that satisfies all my parameters. More specifically, low speed/rpms and high speed, high load, high rpms enviroments. Cruise conditions have always been ok.
Waterless cooling is one way to compensate for an inadequete system, but even it does not provide all the corrections this car needs.
If anyone is interested in my findings and results of what I have done--drop me a PM.
I run 30%coolant 70% water with a bottle of redline water wetter. Temps stay at 180-183 crusing. Ever since I installed that fan kit the highest my coolant ever got was 195, and that's in summer stop-n-go traffic with the ac on. Coolant system on this car seems fine to me other than the factory preset fan turn on temps.
A big part depends on where you live and how you drive. Where are you measuring your temps from? The obdII port.?
Yeah, obdII, I drive slightly aggressive usually.
Prior to changing my coolant and adding the fan kit my temps were +210 in traffic, that's to hot in my opinion.
__________________
Driving the RX-8 is never about the numbers, it's about the experience and the experience of driving it is the best selling point in favour of it. If you drive it and there is a heart beating in your chest, I believe you WILL buy it. The tragedy is that too many talk themselves out of even trying it because of the numbers.
a lot of cool dudes will answer your questions accordingly 
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