Hey @redturbo welcome to the the forum! It does seem like a possibility since the internals are the same. I've never tried to flash tune a Mazda before so I'm not sure how easy/hard it is to do. Would you consider doing it with your CX-90?
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So after doing some digging on parts diagrams, I found a hardware variation within 3.3L designators.
A optionality with a secondary radiator that cools the water that feeds the air-to-water intercooler that the new I6 platform uses. I suspect this equipment is on the Turbo S models, to provide a cooler intake charge to deal with the higher heat output from the higher output tuning. Without the sub-radiator, the intercooler is simply fed from the main radiator. The sub-radiator also contains a secondary water pump to cycle its closed water loop through the intercooler.
My theory is this is at least one hardware difference between the two engine variations. There doesn't appear to be any variations in the short block/long block or transmission though.
So while theoretically the base engine could be tuned up the S output, it likely will need that additional cooling to keep things safe.
A optionality with a secondary radiator that cools the water that feeds the air-to-water intercooler that the new I6 platform uses. I suspect this equipment is on the Turbo S models, to provide a cooler intake charge to deal with the higher heat output from the higher output tuning. Without the sub-radiator, the intercooler is simply fed from the main radiator. The sub-radiator also contains a secondary water pump to cycle its closed water loop through the intercooler.
My theory is this is at least one hardware difference between the two engine variations. There doesn't appear to be any variations in the short block/long block or transmission though.
So while theoretically the base engine could be tuned up the S output, it likely will need that additional cooling to keep things safe.
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So this only exists on 3.3L, the 2.5L (PHEV) has a completely separate parts bin (the PHEV has the lower towing capacity). As I thought all 3.3L had the same towing capacity.
The 3.3L does have an air-to-water intercooler, it sits tucked underneath the intake manifold. ECT (what is displayed on your dash) is the temp of coolant as its leaving the engine to be cooled. So that water will be cooled by both the main radiator, then the sub-radiator, before making its way to the A2W intercooler, or simply just the main radiator in the non-S config. The diagrams are a bit hard to follow, but there is a connection between the main radiator and the sub-radiator, but appears to be on the cold side main radiator.
A ballpark figure of 35% heat exchange requirement for modern automotive radiators puts post cooling temps at ~130F from 200F. Put that through another cooler and you can probably get much closer to ambient air, but even being very conservative, assuming a lower heat exchange rate on the secondary cooler of say 20% puts you at 105F (lower ambient temps will make this second exchange significantly more efficient, but there are diminishing returns). Manifold air temps post air-to-air intercoolers can easily exceed 130F during persistent load, even aftermarket cores. The air-to-water core has less reliance on air flow, and is thus harder to heat soak.
While you are not wrong that putting 200F coolant through an air-to-water intercooler would cause detonation, its just not what is happening in practice. The turbo charge pipe goes straight across COP #4 back into the firewall area to the throttle body then the A2W intercooler.
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To recap - 3.3L uses an air-to-water intercooler, and per the diagrams above, the sub-radiator is connected to the main radiator.
But there are many things that aren't well labeled/connected per parts diagrams. It is likely that the main radiator is actually a two core radiator 1 core for engine coolant, 2nd core for transmission coolant. And the additional sub-radiator is for the transmission side loop, and it is this loop that feeds the A2W intercooler and the transmission. I am not convinced of this, because you typically cool transmission fluid directly in dual core radiators, but with how new this all is its hard to say.
Edit: I think I have somewhat figured it out, the transmission cooling is cooling a voltage converter and some other high voltage components on the transmission, but it still appears to share a common overflow with the main radiator. The only connection I cant actually verify is the other end of the sub-radiator (15-1J0 no. 3) in the diagrams, as 15-200 (no. 1 ) is the generic part id for the main radiator...
It doesn't look like this cooling loop is for the transmission fluid, I am guessing that is a separate cooler. This scenario may or may not explain the two lowest trim levels of the non-S having a lower towing capacity, making the radiator simply a function of towing capacity not power. If this were the case, then turbo preferred plus and up may be identical mechanically.
As far as ECTs go, display gauges and idiot lights are usually for coolant leaving the engine. You do not typically see your temp gauge jump from ambient to operating temp in a very short amount of time when the thermostat opens up, but I am speaking generically. You wouldn't want your primary coolant temp ECU input post radiator / pre-engine as a safety precaution, its a lagged indicator at that point. You want the best measurement of heat coming out of the engine, or the temp of coolant as it leaves the engine. So the operating temperature target of around 190F is the steady state temp of your coolant as it leaves the engine.
But there are many things that aren't well labeled/connected per parts diagrams. It is likely that the main radiator is actually a two core radiator 1 core for engine coolant, 2nd core for transmission coolant. And the additional sub-radiator is for the transmission side loop, and it is this loop that feeds the A2W intercooler and the transmission. I am not convinced of this, because you typically cool transmission fluid directly in dual core radiators, but with how new this all is its hard to say.
Edit: I think I have somewhat figured it out, the transmission cooling is cooling a voltage converter and some other high voltage components on the transmission, but it still appears to share a common overflow with the main radiator. The only connection I cant actually verify is the other end of the sub-radiator (15-1J0 no. 3) in the diagrams, as 15-200 (no. 1 ) is the generic part id for the main radiator...
It doesn't look like this cooling loop is for the transmission fluid, I am guessing that is a separate cooler. This scenario may or may not explain the two lowest trim levels of the non-S having a lower towing capacity, making the radiator simply a function of towing capacity not power. If this were the case, then turbo preferred plus and up may be identical mechanically.
As far as ECTs go, display gauges and idiot lights are usually for coolant leaving the engine. You do not typically see your temp gauge jump from ambient to operating temp in a very short amount of time when the thermostat opens up, but I am speaking generically. You wouldn't want your primary coolant temp ECU input post radiator / pre-engine as a safety precaution, its a lagged indicator at that point. You want the best measurement of heat coming out of the engine, or the temp of coolant as it leaves the engine. So the operating temperature target of around 190F is the steady state temp of your coolant as it leaves the engine.
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A2W loop has its own reservoir that feeds the cooler, great opportunity to build an aftermarket reservoir/chiller tank combo. Also would probably want to put additional cooling pre-reservoir, since the low temp core is still getting some heat transfer from the high temp core (putting additional cooling before the primary radiator wouldn't be as efficient potentially).
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