Ive got about every cooling option possible on the car, and it runs cool on the freeway, streets about 85c. However in traffic or idle it stays around 96-100c. Im wondering if I should get a new oem thermostat, or maybe modify/get a lower temp one? I dont want to be always running my fans, so that is not an option.

Your thoughts?

 

well what temp are your fans coming on? Do you have the stock ECU?

 

When was the last time the coolant was changed, and what mix of water/coolant are you running?

 

Running a lower ratio of coolant to water would help, but if it's running cool at highway speeds, my first suspect would be the fans.

 

there is nothing wrong with that temperature especially if you are in traffic / idling for a while
and that is what the fans are for .. weather you approve with them running or not .. your personal choice ...

if however you are seeing repeated 105 110 while idling for a few mins .. then u have a problem ... 90-105 C .. is normal depending on weather . length of time idling , oil used , whether u have dual or single oil cooler , ratio of coolant.water used ... etc

don't be concerned

 

^ Yep, my first question. If you have a PFC you can make the fans come on earlier than the stock ECU and keep those idle temps under control. I think with a stock ECU those temps are normal, but doesn't mean I'm happy with them FWIW, I just replaced my thermostat with a new Mazda one. Also replaced my water pump. Fans set to come on at 85*C. Putting around town, idling, etc., temp never goes above 87*C, this is SoCal weather (I'm near the beach, about 70*F or so lately).

Lately for me, the instant it hits 85 or so, temp may rise for a minute or two up to about 87. Takes about 3-4 minutes to cool back to 85. When I used to have my fans on all the time, it would have a hard time going above 83*C unless I was really driving the car hard (and it would take at least 30 minutes of driving to warm the car up, PITA and waste of gas)... if you change your mind about the fans, it's pretty easy to keep them on all the time. There's a wire in fan relay #1 you can ground and you'll never have to worry about it again... until your fan motors die

 

There is nothing wrong with your car. If you want it to run cooler, air has to go thru the radiator. At idle or low speed, having the fans on is the only way it is going to happen.

 

The factory thermostat doesn't even open fully until 95 C. Switch the fans on earlier with a PFC if you have one (need a Datalogit for it though). That will put the fans on at low speed (or middle speed if you have the A/C on). Then the thermoswitch will turn them on to high speed. The factory FD thermoswitch is 108 C I believe, but the s5 FC thermoswitch is 95 C. So if you are really concerned about temperatures, switch the fans on with the ECU at 85-87 C.

Then in the summer if it starts running hotter, an FC thermoswitch will bump up the speeds again at 95 C, to either medium speed (no A/C) or full speed (A/C on). The fan control unit will switch the fans on when you shut the car off if the thermoswitch has been active for two minutes, and it will throttle the fans between medium and low speed for ten minutes after shutdown in an attempt to control the heatsoak. I've posted about this in other threads, all the control logic is explained in the 94 workshop manual (availabe in the FAQ I believe) in a subsection of the fuel and emissions control pages.



EDIT: Remember that these are three-speed cooling fans. They have three speeds to minimize wear on the fan motors and to limit the amount of current drawn. Don't be concerned about them running at low speed according to the ECU's control logic. If you utilize the factory control logic to your advantage, you don't ever have to run a manual switch. The factory system is a great design except for the high trigger temps.

 

you have every cooling mod done..... as well as dual oil coolers?

 

wow have I been busy with work. It took me this long to reply....

I have a Koyo N flo radiator stock mount
running 25/75 with a bottle of watter wetter
everything ducted 100% (as can be seen by freeway temps)
flushed the system about 5 times, (got a lot of crap out of the block)
fmic doesnt help, but I do not have an a/c condensor
stock single oil cooler
stock pfc settings
relocated battery

The problem I have is the freeway temps sometimes are at 80-83c which is nice and cold, but driving in the city and the temps are around 95-100, usually about 98c. I just wish I could have that down to a steady 85c. I will look into the fan switch mod, but it seems it would be easier if I had a thermostat that opened at 85c instead of 95c

thanks for the info guys

 

It opens at 82C. The thermostat is not the problem, and you don't need a manual fan switch. That is kind of an "oldschool" mod that is unnecessary with the knowledge we have today.

You have a Power FC. Buy or borrow a Datalogit and switch the fans on to their low speed at a lower temperature (85 C or whatever you want). Then install an FC thermoswitch to increase the fans speed again at 95 C. This will also make the fans more likely to stay on when you cut the car off, as the thermoswitch is also used for the aftercool fan control module. Just use all the factory wiring and change the trigger temps. That was the entire point of my last post in this thread, please read it again. It is important that you understand how the factory cooling fan control logic works.

So you need:

Datalogit ($200-$300, but you can use it for a bunch of other things like swapping maps)
FC Thermoswitch , $75 ?

What you're getting for that money is a completely painless installation requiring no additional wiring, and a fully automatic cooling solution requiring no driver input. You're just taking the factory **** and making it do what you want it to do.

 

Stock single oil cooler and fmic are your problems. Upgrade to dual and ditch the fmic, its acting as a huge heatsink for the radiator.

 

I would prefer having cooler air, than cooler coolant. I can live with 98c coolant, dont want to mess around with detonation with a smic. Its just not worth it imo.
I dont know why people sacrafice cool air temps for direct airflow to the radiator. makes no sense to me.

imo an air to air intercooler is more sensative to ambient airflow than a water cooled radiator.

I am thinking about swapping my oil cooler though. its very old and crusty. will search and see what people do

 

been meaning to get datalogit for awhile now. guess its time to buy, thanks for your help

 

Why don't you install an electric intercooler fan that blows air directly at the top of the engine where its the hotest? Unless your intercooler is mounted horizontal it should work, I had one installed and it made a hell of a difference in stop and go traffic although I also had a by-pass fan relay setup all controlled from a console panel I installed.

I like to have control and not depend on the PFC or termostat, especially for something as important as cooling that beast down!

You have a good point in the radiator air flow, which blows hot air in the process of removing heat from the coolant.