I suppose before going into answering this question, you'd all like to know what's done to the car and what the current temp situation is.

The car is a 94 Touring with a 10k mile engine in it (ports were smoothed out but not enlarged).

Upgrades:
99 spec front lip
Fluidyne radiator
R1 oil coolers (2) with OE ducts
OEM undertray IS in place
Pre-cat replaced with a clean 3" DP
Stock main cat
HKS Ti
Metal AST

Stock engine bay otherwise (OE battery size, OE battery tray, OE intercooler / duct etc)



Here's my issue.
At any ambient temp over 85deg F if I'm driving around town in stop / go (below 40mph) my temps increase and eventually get near 220F. For me, this is high but isn't really all of my problem. If I see my temps get to 220, I'll check and find that my fans (both) are on. At this point I head over to the highway and cruise for a few minutes at 60-70mph, and it takes a good 10-15 minutes for the temps to come down to the 180-190 range. I've found that with the A/C on (on the highway the temps come down even faster) which suggests that the air flowing through the rad isn't enough.

So the question... are there any of you that managed to retain the stock US bumper and maintain a temperature of 185-200 daily driving in 85F weather with a configuration similar to mine? When you reach your high temp, how long does it take to come back down with no fans, just airflow @60mph?

Let me add one more component. I've been monitoring oil temps as well. If start with water temp at 220, my oil temps are usually there as well. I've found that my water temps only drop if the oil temps come down too... I've yet to see my oil temps higher than water temp.

As a comparison, I've got an FC with front mount and the entire radiator path is ducted so there is no escape of air from any direction other than aft of the radiator the fan comes on at 200F but I can beat up that car on track and it won't hit 200F, maybe 190F and as soon as I let off, the temp drops to 175F over the course of a single straight.

Lastly, I recently had to leave the car running while parked on the side of the road helping my buddy. I left the A/C on so the fans would run and the water temps just sitting rose to 220F over an hour, but dropped to 185-190 after I opened the hood. Ambient was maybe 70deg F.

 

My car is similar to your car. R1, Fluidyne, OEM bumper but with AST deleted and ~ 60:40 water:coolant. I rarely see much over 190 F./ 88 C....even on the hottest days.

Not sure who planted the thought that you need a 99 spec bumper for adequate cooling, but your issues lie elsewhere IMO.

 

An aftermarket bumper won't help if you're sitting in traffic because you have no airflow. You've actually proven yours is fine by traveling at highway speed. You may want to look into a fan switch mod that kicks on the fans at lower temps, which should help at lower speeds. Pettit sells one or you can mod a FC switch.

 

The stock ecu doesnt turn the fans on until the coolant gets pretty hot (108c). To keep your coolant temps down, you need to be able to turn the fans on sooner. The two easiest ways to do this are to install an FC thermoswitch (which will turn the fans on earlier: 95c) or install a fan mod switch (which will allow you to turn on the fans when you want them on), or both. I have both.

https://www.rx7club.com/3rd-generati...u-read-397156/

Cooling Fan Modification

 

for what you're trying to do, you need to kick on the fans to high speed at lower coolant temperature. it's a 3 speed system. one bump comes from A/C, one by a physical thermoswitch, and one bump by the ECU.

 

Great point. And I forgot to mention earlier that I have the FC Thermoswitch.

 

Are you on the stock ecu? Like said above, fans don't don't on until about 220. Get a power fc and change the fan turn on point. If you get any more power mods you will need a pfc anyway and the car will be safer with a proper tune. For the time being and fc thermoswitch and 180 degree thermostat should keep you under 200F.

 

This may or may not be relevant and helpful to the OP ,

like stated above you seem to have issues with temps while staying still . Now I'm in miami with 90 omething temps . and dont really have that issue . Check your Fan relays . i've had one relay go bad on me and fan just wasnt working as they should . like stated above its a 3 speed system , but one of the speeds uses 2 relays . and if one of those relays goes out temps will slowly rise . rather then maintain / or go down . I'd give that a check


NOW for my selfish impedement of this thread . I have a Power FC , and I have my fans turn on at 85C . Does this hurt temps while driving at higher speeds? having the fans turned on ? I hear alot of yes and no's on this . Back when I had my fans turn on at 88C My car would run at 85/86 at highway speeds ,

 

Another item worth mentioning is ducting! It's cheap and can improve things dramatically.

Shine a drop light underneath the belly pan and beside the radiator and use long foam strips that they sell for home window air conditioning units to plug every opening where you see light coming through. This helped mine significantly back when I was running close to stock configuration. Other than that, switching to my Vmount IC/radiator configuration was another HUGE step improvement in cooling performance!

Just my 0.2!

 

i would say FC thermoswitch will solve this. you have way better cooling mods than I, and I do not get up to 220 in normal stop and go. I have stock rad, single oil, stock ducting---just FC switch, downpipe,catback.

stock switch activates and sends its signal at 226 F. with an FC switch, that temp will become 95c/203 F when it sends its signal. My temps stay around 190 in light street traffic. in heavier traffic it may get up to 200, i hear the fans come on higher, and temps drop back down -- drop even lower when i have AC on, as that kicks the fans up a speed as others have mentioned.

 

A PFC is another way to kick the fans on earlier. You'll get a few other benefits too.

I have just about the same mods as you and my car doesn't run hot at all, even after flogging it all day long at Buttonwillow Raceway which is in the middle of Death Valley.

PFC, ducting, a little water wetter and a new intercooler would be at the top of my list. Even a nice stock mount one like a Blitz or M2 would make a difference.

 

Hey guys,

I thank you for your responses, but it seems the school of thought that "turning on fans earlier" is how to keep these things cool just won't cut it.

Cruising on the highway for 15-20 minutes may bring my temp down, but shouldn't there be enough air flow / heat shed to prevent my temps from going up after running through 3rd-4th gear?

Please note that I included a scenario where was idling for an hour and I turned on my fans via A/C switch when my temps were at 180deg F and they still climbed to 220 degrees with the fans on. My headlights were on too which should have been one more relay trigger. The combination of the two should have yielded the "middle speed" of my fans which for some reason wasn't enough to control the temp climb.

Again, both fans are functional.

 

it sounds like you might need a thermostat.

i was driving around a 99 spec FD the other week, and it basically acted like your car, temps were 180-190 on the freeway, and then as you slow down they would go up until the fans turn on @216 (its 99 spec, might be different) and then they would rapidly cool off.

in stop and go traffic, the fans would generally be off, and temps would be in the 200-210 range.

and if you just start the car and let it run until the fans turn on, its about a half hour wait

 

Fact #1: At idle, with no air flowing thru the radiator, the fans are the only thing keeping the car from overheating. Having them come on earlier is a big plus. Mine are set to come on at 185.

Fact #2: Without significant modification, your FD coolant temps will increase after one or two 3rd & 4th gear pulls. If you expect your car to stay cool for "road racing" types of runs, you will need ducting, a bigger radiator, a second oil cooler, and a vented hood.

 

This is an interesting troubleshooting sceanario. At highway speeds, temps are ok. In town, fans work, but temps get hot.

In both situations, air is moving across the radiator (if the fans are actually working). Is it the T-stat then?

 

Again, thanks for the replies.

I forgot to mention, I've changed the thermostat 3 times. All 180 degree. One time i drilled two 3/16 holes into it. All that did was make the warm take longer... Secondary turbo doesn't "come online" till temps reach 170. So that went in the trash.

@adam c:
I do have 2 oil coolers, both ducted.
Regarding your "road racing" comment. Does this mean you don't consider a fluidyne radiator large enough to keep the car cool after a couple pulls?


I don't really consider my highway speeds ok because it takes soo long for the temps to come down, granted they eventually do.

 

I also have a fluidyne radiator. I believe it to be a good choice. Good ducting for your radiator will help. My coolant temps will go up if I climb a long hill at highway speeds. I believe this to be normal for our cars. My temps will go up if I do a couple of hard pulls thru 3rd and 4th gears, also normal.

Our cars run hot. Yes I believe it to be normal for the temps to take a while to come down after hard pulls, especially on a hot summer day. Ambient temperature makes a huge difference.

For around town, the best we can do is run the fans to keep it cooler. Make sure your fans all work when they are supposed to, and do something that will get them going sooner (see my post above). My 2 cents.

Adam

 

If you feel your at speed temps are inadequate, now you're talking radiator/bumper/etc. i blew my completly stock FD driving it to hard and will be upgrading to a Ron Davis rad and 99 bumper with large twin OCs. Will report back if that is the way too go as an option to a V-mount which seems to be widely regarrded as the solution for overheating (both H2O and IAT)

 

What coolant/water ratio are you running? Run as much water as you can get away with safely. Check the face of your radiator, make sure it's clean between it and the condenser. Install the FC Thermoswitch. If none of those things help, pressure test your cooling system. But the front bumper isn't your issue.

 

My car always ran hot(actually had a thread about it) and heres what i changed, PFC and DEI titanium wrap on my downpipe and midpipe. Thats it!

Turning the fans on earlier and the downpipe being wrapped has completely solved my coolant temp issues. Heck the car has a hard time getting up to temperature now on anything cooler than an 80* day.

The only time my coolant went over 200 was on a track. On the street it lives around 180-185 and maybe 190 sitting in traffic with the a/c on on a 90* day.

I'd get a PFC with a good tune and heat wrap that downpipe and lose the main cat for something that will let the exhaust heat out the back of the car. The Bonez highflow is a nice piece and will keep boost in check and allow the engine to breathe better/run cooler(at least on my car it did!)

Jason

 

Describe exactly how you blew your stock FD. Was it actually completely stock? What mileage on it and what driving?

 

One thing to consider is that the AC condenser can block a lot of air flow to the radiator. Make sure there is air space between the condenser and your radiator and that the condenser isn't plugged up with dirt.

 

100% stock w ~65k. It was babied up until 4 years ago when i started tracking it. Ignorance was truly bliss, but then I went and installed water/oil temp gauges before my last track session. Believe i was reading 270F water, but that didn't stop me and i paid the price.

Another mod btw is the Mazmart pump, but is probably marginal benefit compared to other recs on the thread

 

^ Was it a coolant seal failure? I think we can all agree that running 270F is too high for this engine, and track activities, especially for a non R1 (single oil cooler), are hard on a stock car. On modern cars you can't even run them too hot without a mechanical failure because the ECU will cut power.

As for OP worrying about 220F on a street driven FD in the summer: I don't know, I can't get too worked up about it. They ran like that stock.

As I mentioned before though, there are three fan speeds, controlled by 4 relays. In the stock configuration you will never run at max fan speed unless the A/C is on. The problem is that the A/C increases heat rejection in the system. What you can try is rewiring the fans so that the thermoswitch kicks on 3 relays instead of 2 (putting you at medium fan speed by default) and then the ECU gets you to max speed. That way you won't need the A/C to have max fan speed.

Please see my thread https://www.rx7club.com/3rd-generati...ntrols-876767/

 

Have not torn down the engine, but am 99.9% sure it was an O-ring failure. Up until that moment, it was reliable as a rock. I'm convinced there's no reliability issues with stock configurations if you routenely change the coolant and engine oil. The problems surface when you start messing with them (or tracking them )