My car came with a lower degree tstat and a good bit of ducting for the factory radiator, IC, and ducts for the oil coolers. I believe the tstat opened around 75 C. With that setup the car would rarely go over 90 C at which time the fans come on. Only during highish ambient temps and extended idling would it get that warm.

fast forward to now, I went through the entire cooling system with OEM hoses, OEM tstat, IRP water pump, and a HKS V Mount with a Koyo N Flo radiator. Similar to before, the system rarely gets to 90 C. I have an aftermarket gauge in F (tied into throttle body coolant line), and it matches up with the same number.

My question, possibly issue, is that unless I drive somewhere with traffic that involves stopping regularly, or I let the car idle, or do a solid pull through a few gears, it will struggle to get past 82 C and open the tstat. For example, my drive to work is about 20 miles. I go through 2 stop lights to get there and speed limit is 60mph. My car will typically still be sitting at 81-82 C. If I get on the interstate the temps will climb to 84-85 usually, I assume due to the highish revs at 75-80mph with my jdm trans and 4.30 rear.

I assume the tstat is partially opening and allowing flow because I am not having any issues that im aware of but I just want to be sure im not hurting anything. Should I go back to a lower temp tsat to get more flow? Leave it alone?

 

If the engine has been rebuilt, it's likely had its oil cooling jet thermostat deleted. As I've ranted before, this is a needless mod that only promotes over cooling; replacing with a new OEM part gets the job done. How are your fans controlled?

As for actual downsides, maybe a small hit in gas mileage and some increased chance of carbon build up.

 

Thanks for the response. It was rebuilt by feed in Japan but I have not been able to find any detailed description of what they typically do other than the basics. The car has a power fc with fans set to 90.

 

I would definitely raise the fan engagement temps to something like 95* C. No need to trigger at 90* C.
I would ask if your heater works at those engine temps but you probably don't use it in Jax

 

I've used it once or twice hehe. It does well enough but yea rarely needed.

 

Speaking of Jax... My friend used to own MVP's Sports Grill. I guest bar tended one night another life time ago.

 

My last FD would typically sit right at 84C unless I was flogging it and then I'd see as high as 87C as long as the car was moving. Only time I ever broke 90 was when I was sitting still idling and then the fans would come on when needed. Long way to say, I think 82C is just fine. If you are in the 70's yeah, that's likely not warm enough to be proper.

 

I have a similar situation and a very similar setup. I just switched the fluidyne radiator with the N flow and i made a custom shroud to fix my a/c issue with my aftermarket fans.. My coolant used to go to 105 at the track easily.. now it wont even go past 80-85 at the track same weather conditions. I do have a very low thermostat (69degrees).

 

If you lived in a cooler climate, I think the decision to install a stock t-stat would be an easy 'yes'. In the spring and fall I see ambients that are pretty cool. Not sure about your situation.
And it's academic about thermopellet removal as you're not likely to reinstall it IF it was removed. But I don't think the mod is needless. And if the thermopellet was removed I doubt it’s a significant contributor to your problem...if it's a problem.

 

Thank you all for the responses. I suppose i'll let it be for now. We'll see what happens when it really cools down in another couple months.

 

I dont have an accurate coolant gauge, but I recently switched from new OEM radiator to Koyo N-Flow and it runs so cool that in normal driving the heater barely works anymore.

I was blown away.

 

Ya same here. Koyo n-flow. stock thermostat, r1 dual oil coolers. my temps year round are maybe 175 on the highway. idling they get up to 196 but once the fans kick in they drop like a rock.

 

Just want to comment on the fact a bunch of RX7 guys are in here talking about their cars running TOO cool.....

 

as long as its at least 74c / 165f its fine, the tune might be on rich end from fuel compensation, but 165 is ok for the engine, not too cool, fake news that it will hurt motor. In perfect world id like to see 170's on water, and 180's on oil temps

 

hahah for real thats the damndest thing, if you're issue is too cool thats a GREAT proble mahahahaha

 

The only thing you'd be hurting by running 'too cool' (within reason) is your wallet. As mentioned, ~180F/82C is a great target to go for, but if you're within 10-15% you're fine. What is usually NOT fine, is seeing wild fluctuations/variances in your temps, if that's a trend you notice its time to revisit your cooling systems.

 

I find this thread really interesting. Especially this quote.

For years I ran an electric water pump on the coolant side and large dual oil coolers without a oil thermostat on the oil side. During the winter, all temps were crazy cold during sustained freeway driving. Depending on ambient temps, coolant and oil temp could be as low as 150ºF during on the freeway. I wasn't really worried about the coolant temps but the oil temps really had me concerned. Whatever the temps were, they were alway completely linear.

Even though packing was a pain, I finally plumed a 185ºF High-Flow Engine Oil Cooler Thermostat. It did raise oil temps over all but temps were no longer linear. During the same colder ambient temps it was a constant fluctuation of up to 200ºF to an almost instant drop to 150ºF. I am no expert but this just did not seem like a better solution. Maybe it is. I am honestly not sure.

 

Before my radiator decided to have a hole punched in it, I would see cruising temps of 195-205 (straight sustained highway temps, no AC switch on, parklights not on.) depending on if i was going 60-80 mph. 205 would be doing about 80.

After the rad went, I installed a regular Koyo (not the N flo) and I seem to be doing about 185~ now at sustained highway cruising. The car will heat up much more rapidly when sitting still with the Koyo, I've noticed, temps will rise to 192-194 before the fan kicks on and brings them down to the low 180's. This seems to happen much faster than with the stock rad, but the fans always bring it under control. So far at least. If I cruise far enough at about 60mph, the temps tonight went down to about 169 I believe. I was astounded. Only cooling 'mods' the car has is an FC thermoswitch. Undertray is present.