SwappedNA

iTrader: (1)

So I recently replaced my radiator (thanks to whatever decided to punch a hole through my stock one) with a Koyo regular model. In a pure water setting (I know, straight water, I know, this is just a rough experiment) my thermostat mounted AEM temp gauge (so I'd trust its accuracy in terms of the sensor, anyway) typically reads in the 170's (F) while cruising. On cooler nights of sustained cruising, I actually can see it drop into the high 160's. Granted this experiment was performed with the car running straight water, but even with straight water, don't these temps seem unusually cool? Factory temp gauge reads its normal range, but according to the coolant thread, that's about an 80 degree span, but if its reaching operating temp on the oem gauge, I believe its warmed up.

I also noticed in comparison to the stock rad, when the car sits in traffic, the temp climbs slightly faster. Obviously a car is going to have its temp raise when sitting, no airflow, and the fans not kicking on yet, but it seems like the Koyo reaches the kick on point of the fans faster than the OEM rad did (I have an FC thermoswitch, and it kicks on right when it should.)

I'm about to conclude the experiment and do a full change with Zerex Red (Asian) and more distilled water, none of the harmful 2eha nonsense.

Also on a side note, I've noticed my heater blows cool air around those temps, 160's-170's, but occasionally I will get a burst of warm air. I don't hear any bubbles coming from the heater core. If the car gets up in the 180's or 194 when the fan kicks on and cools it back down the heat is I believe, much more noticeable. Could it just be that the low temps it's running at are causing the heater to not be blowing warm air? Thanks for the input, I appreciate it everyone.

AE_Racer

iTrader: (1)

I recently posted a thread with the same “issue”. I have a koyo n flo in the hks v mount configuration and with FL cooling down, I regularly see my car in the low 170s while cruising. With my route to work and driving it a few times a week, my car can go weeks without ever cycling the fans on (90 C with power fc). I use a mix of distilled water and pentosin coolant that met the RX7’s requirements.

The responses I got were that a negative would be reduced fuel mileage. And then the heater, which I havent needed to use yet. The heating system is optimized for normal operating temps so dropping 10-20 degrees will definitely have an affect on its output.

ItalynStylion

iTrader: (1)

170F is 76.6C. It's cooler than most but not really that cool. Thermostat opens at ~175F anyway so that seems about right.

This may be a dumb question but what part of the thermostat is the sensor located in? Is it reading water temp coming from the radiator or is it reading water temp coming from the engine? Those are obviously going to be quite different. I'm pretty sure the stock sensor location is on the back of the block but I can't remember if that's for temperature sensing purposes or not.

Have you researched what other people are reading as normal temps that have their sensor in the same spot as you? Did you have the sensor in this position with the stock rad? If so, what were temps then?

alexdimen

iTrader: (13)

Ambient temps are getting cold. Doesn't seem too far off the mark. My car sits at 75-85 C dependent on driving style and outside temp.

I'd be more concerned with what temp my ECU was reporting vs aftermarket gauge.

And... If you're expecting warm air to come out of anywhere except the defrost and foot vents - I wouldn't hold my breath.

ItalynStylion

iTrader: (1)

I meant to post this as well but forgot. I learned this lesson the hard way the very first few hours I owned my first FD. I'd bought it in New Mexico in February and it was starting to snow so we were trying to beat the storm back to Texas. My wife and I were in the new (to me) FD and my friend and his wife were driving my Tacoma. My wife and I froze our asses off for the first two hours of the trip because nothing but cool air left the dash vents. I thought it was broken, turns out, that's just how all FDs operate. Put it on defrost/feet and OMG we could finally drive without our winter coats. We were both way less irritated at that point.

gracer7-rx7

iTrader: (16)

Some thoughts:
- If you installed the temp sensor after the thermostat (which it sounds like you did), it won't register changes in the fluid temps until the thermostat opens.
- Stock thermostat opens around 190something degrees iirc
- Stock temp sensor reads from rear iron iirc
In summary, because the temp sensors that you are attempting to compare are in different locations, they aren't readily comparable.

You might have air in the system. That could contribute to the observed behavior. At this point in time, you are probably the only person on the forum that has any experience with a stock radiator. Everyone else has probably upgraded 5-10 years ago.



Yep. IMO That is to be expected given that you aren't getting up to operating temps

Mine blows hot air out of every vent position...

alexdimen

iTrader: (13)

Weird. I thought it was a fact that heat was foot and defrost only?

Maybe your system is letting some heat by. I am pretty sure mine let's some heat out of center vents. But it's nothing like the foot vents after a WOT pull.

I just accepted it and considered it an upgrade because my E28 only had heat out of the defrost by design. Not only that, but it also had 2 separate blowers and vent systems...one for the heat and one for the AC!

gracer7-rx7

iTrader: (16)

Yeah, that is odd. Then again, I'm in CA so I rarely use heat.

SwappedNA

iTrader: (1)

Okay, got a lot of replies, haha. Going to try to remember to address each of them. The temp sensor for the AEM gauge is on the thermostat housing, right in front of the thermostat itself almost, so the coolant going to the rad is what it is seeing. It does register temps pretty quickly, there isn't a no read or exceptionally low reading and a sudden jump when the thermostat opens, it's pretty linear from the time I start the car until it reaches the 'normal' temps, the car does have the oem sized hole I drilled into the thermostat at the 12' position, so maybe that is why/a contributor, or its just reading the radiant heat from the water behind the thermostat.

I'm not necessarily trying to compare the stock gauge and the AEM one, given that the oem one has I think an 80~ window before it starts to move above its normal resting place when the car is warm, I'm moreso just saying, when the factory gauge reads where it normally should, these are the temps the AEM gauge is showing.

I've heard many people say the FD isn't plumbed to put heat out the dash vents, and what my interpretation of warm is might be different to others, but I will say when the temp would get up to 190+ due to the car sitting at a traffic light, etc, I would notice the air coming out of the dash had a noticeable temperature change, now I'm not saying the FD is plumbed to put heat out through the dash vents, or that it isn't, I'm just saying under those conditions I noticed a temp change from the dash vents.

When I got the car it had the stock rad, which was probably gunked up, no undertray, and the stock thermoswitch. Normal driving temps were about 205. They lowered when I replaced the undertray with a new one, when I installed the FC thermoswitch, and the biggest jump was the Koyo rad (it's a regular, not an N flow.) I want to say the koyo has about a 14~ difference in cruising temps as opposed to the stock rad. With all the mods done but the koyo I was seeing 186~ ish I believe during in town trips