I know the rotary doesn't Love city driving. But I keep noticing how relatively cool the engine runs on the highway (under 180f) but a stop and go drive will get it above 200f in no time flat.

Is there anything that would cause the higher temps at stop and go that could be a problem which wouldn't show up at cruising speeds on the highway. Might be paranoid because both rebuilds were from overheating issues.

Thanks for any insights.

 

Air hitting the radiator and ic at speed cools it down, now imagine standing on hot pavement barefoot. the radiator is relatively close to the ground and angled. Of course your fluid ratio and type also have to do with this as well as temp your fans come on, working cooling system etc. check to make sure it is opening up when it shoukd be, if not replace it, also what radiator are you running? There are so many factors a mod list would be helpful.

 

Perfectly normal. Of course you get really low temps when your driving, stop and go traffic will make them rise until your fans turn on to cool them down. If you have a FC thermoswitch temps should never go above 203F. You can turn on your AC or defrost to force the fans on at low speed and it will bring temps down.

 

If you have a fully stock fan control system, this is normal but not optimal. The stock fans don't kick on until the car is VERY hot. With proper fan control, you can keep water temps in the 80-90 deg. C range all the time which is the sweet spot.

FC thermoswitch is one thing that can help, but to really get it where it needs to be the ECU's control of the fan speed needs to be changed, only way to do that is a PowerFC. Or an HKS fan controller.

Dale

 

Thanks, since it's Florida -- ac is almost always on and at 2 or above, so fans are operating.
Just surprised at the difference in temps.

Stock Cooling System, but flushed regularly.
Fans work correctly.
No coolant loss.

 

If you want to keep it completely stock you can get with pettit and get their 185f fan control so the fans come on sooner.

From the pettit website

#8 Most RX7’s benefit from cooler operating temperatures our 185f fan switch is a direct replacement for the original 210f part and as they get older its common to see 225f before the fans kick. As we all know cooler running improves longevity for the engine as well as all under hood components.

http://shop.pettitracing.com/product...ucts_id=120050

 

Get this as well.

Pettit Racing

 

Nothing wrong with your car. It is operating within the thermostat control range (182-207F).

swap in FC thermoswitch if you want the fans to kick on (or increase speed when A/C is on) at a lower temp

 

I had a thought while reading this. I removed all my AC mechanical components like many people do (compressor pump, front radiator, lines, condensor, radiator block under the dash in the heater box, etc) but left the wiring there, just unplugged where the pump used to be.

If I were to push the AC button on the dash with no AC installed, would this still trick the ECU into turning the fans on?

(I've never pushed the AC button after AC removal, because I wasnt sure what would happen)

 

I don't think so, because of the pressure switch.

 

If it makes you feel any better, my sport bike averages 172f while cruising on the highway, but as soon as I hit side street traffic the temps will climb to 220f.

That's obviously not a rotary, but still a comparison of a high performance engine (1000cc supersport) that will see some pretty crazy temp swings based on air flow. 200f is only like 93c, which isn't that terrible for traffic, especially if the ambient temp is pleasant. If you're holding that temp than I wouldn't worry too much, if it keeps climbing past that... then get concerned.

 

Thanks Arghx.

My 70's era Chrysler with Australian Hemi engine used to give the same temp fluctuations.

On the highway, it would hold a good temp. Once I got into slow moving traffic, I could actually watch the temp gauge climb, and the needle moving before my eyes.

It ran a 4 barrel Holley, all the go fast muscle bits from Summit, along with a big shiny $2000.00 PWR specially designed and fabricated one-off aluminum radiator. It was a high performance carburetor engine, but did the same thing as the sports bike mentioned above, and your car.

My (now sold) BMW E39 M5 was another story. In traffic or highway, it never moved off 99 degrees C, no matter what you did to it. But that car gave me more grief and engine trouble than any other car I've ever owned..

 

I think the lesson we all learned from the FD3S is that OEM temperature gauges are not necessarily linear. The fact that more modern cars seem to run at constant temperatures is probably at least partially attributable to the fact that their gauges "prefer" to display the correct temperature. Of course, any car with excess cooling capacity can be configured to run at a nearly constant temp, but a lot of high performance cars are going to be marginal on cooling.

 

Since this is sort of on topic, for those with FC Datalogit, what would be a reasonable target temperature to have the fans switch on?

 

an under tray would help with temps , not sure on stop and go traffic but does affect it pretty good

 

The old rule was something like 'the more horsepower you make, the hotter its going to run'.
Thats been pretty accurate for most of the fast cars I've owned.

The new stuff (2001- present models, espcially european cars) tend to run very hot. Some BMWs I've owned, have normal operating temps of 110 degrees C, and ECU controlled electronically variable thermostats (Example: ECU opens and shuts the thermostat based on load parameters, etc, completely independant of coolant temperature)
They do this for emissions. Hotter running engines meet emissions more easily.

One of my BMWs would vary the thermostat opening during part throttle highway cruise, in order to raise/lower the coolant & running temp, and adjust its AFR mixtures to get the best lean cruise and best fuel consumption/emissions possible for the situation, taking into account air ambient temp, intake air temp, TPS value, etc. Thus it had NO EGR valve, and this was the alternative method of making it meet emissions.
Scary thing? That was a 1996 BMW.

Imagine how complex they are now...

It worked well until things started going wrong. ECU began miscalculating, sensors began wearing out. Then it ran pig rich everywhere. And cost mega $$$ for a specialist to try and diagnose. I underwent BMW training and got so far with the Motronic system, but ultimately sold the car, as it was too frustrating.
Give me my nice simple FD any day!!!

 

I think your BMW gauge (dash gauge right?) may have been lying to you... A lot of the new BMW engines have electric water pumps that vary the temperature. They run 220F at certain load points, because the higher temperature reduces friction.

 

You can install a switch to turn on your fans when driving in the city. This has been around forever. I still use it to cool down the engine at shutdown sometimes.

Cooling Fan Modification

 

"both" rebuilds and you don't know why heat builds up when your standing still in traffic?

Upgrade to a Koyo radiator
Run 70/30 and Redline Wetter Water
Remove precat
Change to 185f Thermoswitch
Get PFC and set fans to come on at 84c

I think if you're worried about another rebuild you should definitely be doing these things. Else, move up north.

 

This , except I feel like the car likes running a little hotter then 84C , I have my fants set at 87 Thermostat doesnt even fully open until 86C .

I had mine at 84 for a while But hte car and fans seems to like this setup better .

 

Some people have recommended the pettit FC thermoswitch and I recenty removed mine because I put my PFC in. So if your interested drop me a pm and I will sell it to you. I put maybe at most 3000 miles on the sensor.

 

Mine hover around 180F during cruise and the fans keeps it at 195F in traffic, those numbers are pretty normal in the summer, not sure about this time for the year tho, but again I don't know how hot it is now in FL

 

I see you are running stock ECU, you should get a PFC. You can setup your fans to turn on earlier through it as well as see far more accurate numbers then your stock gauges. If you see the water temp gauge go up that's when you know it is too late...

 

you realize that the radiator and intercooler is basically an air cooled heat exchanger. you drive the car, it moves through the air, the air goes through the heat exchanger / radiator / ic fins and cools the medium running through the heat exchanger.

if the car isn't moving, then there isn't much air going through the heat exchangers resulting in hotter temps.