First track event with the RX7, getting a bit warm?
 

Hey everyone, for the past year or so I've been putting together an 86 FC. Finally got it on track last weekend. The car made it to the track, through 7x 20 minute sessions and back home.

As far as cooling is concerned, I've got a very large 3-row aluminum radiator (not sure the brand, came with the chassis), black magic fan, Pineapple-style "yoohoo belt" and a fabricated header-panel to cover the gap between the bumper and radiator. The stock under-tray is mounted as well.

Now, as the day got warmer and I got faster, I noticed the temp gauge would start moving up. The morning sessions it would go from 1/4 to 1/2, which I would consider normal for the car. Later in the day it start going above 1/2, so I backed off for a few turns put it in 4th or 5th and let it cool back down to below 1/2 and then went back at it.

Does that seem a bit much for probably 12-13 minutes into a 20 minute session? There are some gaps between the header panel and the supports, as well as where the oil cooler lines go, should I be looking at bridging those gaps?

I haven't got to the point of installing an aftermarket gauge yet, but that will happen in the next few weeks.

EDIT: Oh yeah, also I'm running 50/50 water/antifreeze. When I was putting that part together and getting the car running, it was still within freezing temps at night.

I would first try changing the coolant, drop it to 15-20% coolant and some sort of "water wetter". Plugging all of the gaps won't hurt either.

These are hard to keep cool. Start with a real gauge so you know your temps. Shoot for 200, 220 is high, 230 is dangerous. Duct the front, you'll have to play around with things to get it right. Use 90-100% distilled water, 10% antifreeze if you insist and one quart of 40 below. Consider an underdrive pulley to slow down the water pump.

all this info is great. but i would add 1 bottle redline water wetter additive to the mix. seemed to help me by 10-15 degrees

I used to use water wetter, then switched to 40 Below (similar but better additive). Not sure how well the two would mix, never tried it.

Interesting, I'll probably go ahead and change out the coolant before the next weekend then.

Thanks for the advice! I'll post up after the next one (which will probably be in a few months) if I continue to have issues. Next up is Road Atlanta in August....if I have heat issues, it *WILL* show that weekend.

What was the ambient temps? My S4 will run warm if its pretty hot outside. Are you still using a thermostat? Are you running stock pulleys? Your water pump may be cavitating at high rpms.


-Jack

Ambient was around 86 degrees, there was a bit of wind also, which seemed to help keep the track temps down.

I am using a thermostat, but I'm not sure which one (Stant or OEM), the previous owner had put it in. Stock pulleys with Pineapples "yoohoo belt" to keep from slipping.

High RPM's may be the issue, if I shifted a 7500's on the straights it would heat up MUCH quicker. If I kept my shifts at 7000, I could go through most of the session. The stock water temp gauge would get up to about 2/3 before I backed off, then it'd drop back to 1/2 after 4-5 corners in 4th or 5th gear.

I'm not opposed to changing over to Evans coolant either, but I really need to get the water temp gauge in and then get it back on track before I go crazy with this stuff.

Hey man, off topic, but I didn't realize you were from Nashville. You need to come out when we have a meet sometime. See you at Road Atlanta in August.

Brent

I would change the thermostat to a OEM one just to be completely safe, and I agree with the post that said to change to an underdrive water pump pulley.
Also get all the gaps covered up between the bumper and radiator, it'll help a lot.

Are the sides of the radiator blocked up as well? A common thing with the FD's is to use adhesive foam to block up all ways for the air to escape around the radiator.

Also, how's your oil cooling. Are you turbo or N/A? IIRC up to 40% of your engine (rotor) cooling is done by the oil alone so managing those temps is just as critical as the water.

I would just gut/core the thermostat, and slow down the water pump. The stock S4 temp gauge is supposed to be pretty accurate, not a dummy one like the S5. You can get either a smaller alternator pulley, smaller main pulley, larger water pump pulley or combination of the three.

Drill the thermostat if you have to, but don't gut it - remember that when it opens it also blocks the coolant bypass channel. Personally I would just make sure that you have a good stock unit in place.

For pulleys you need to either change the main or pump pulley. Just changing the alternator won't by itself reduce the RPMs to the water pump (which is the goal here).

Have you flushed out the cooling system? If the engine is older then you may want to look at trying to get things cleaned out internally.

+1 on the oil cooling. You probably want to plan on adding an oil temp gauge to go with the H2O temp.

Good luck,

-bill

That's right. If you gut the t-stat you will need to block the bypass. I believe 3/8 pipe plug is what i used.

It's a 1/2" NPT plug (you will need to tap the housing first, do it off the car). Ditch the thermostat, if the bypass is plugged there is no reason for the thermostat.

When I got the engine last year, I did a complete flush, and it was without coolant until I started the car about 4 months ago. The system is clean and fresh, but I really should have just replaced the thermostat when I had the car all apart. With everything else that was going on, I just didn't think about it.

I'll start in on the ducting next week, there are a few gaps (like behind the battery where the oil cooler lines pass through). The oil cooler is OEM, but I've got the stock ducting in place under the car. Water temp and oil temp gauges are on my list of things to buy.

Ha, nice! You guys have meets? I remember searching around and didn't see much for middle TN...lots of people in East TN. I just moved up here the beginning of this year.

I'll be there in August, I'm going this weekend but I'll be back to working T&S this weekend since I have a lot to go over on the car.

Yeah, every now and again we get together. Not as much during race season, but we are having a rotary bbq here pretty soon I believe.

I'll be at VIR this weekend for the Mazda Driver's event. Have fun at RA! See you in August.

Brent