Hi all,

I went to the track this weekend and my 8 was overheating in the afternoon. The coolant boiled over at one point, and I had to keep rpm's under 7k to keep driving. This would happen after only a few runs. Ambient temp was 100F. I got the RB street flash a few months ago and I suspect this is what caused it, because I've taken the car to the track before in similar weather and it ran with no problems.

Another thing is that the RB street flash killed my cat after a few weeks of use. I had an RP supercat with 10k miles that failed right after I got the flash (redlined about 20 times). Is the flash just running the engine way too hot in the upper rpms? Or do you guys think it could be another reason for the overheating?

I also have a Koyo radiator, greddy oil pan, running 5w30, and 50/50 coolant/water.

 

I dont know, but i was getting the same problems, killed my supercat, and when temps went above 90 at the track I was getting boilover and water temps around 235 degrees

 

the flash may be killing an aftermarket cat. the street flash will not kill an oem cat.
I just got through with a track w/e during ambients of 105. coolant never over 215, oil never over 230
my thoughts:
1- use a 70/30 coolant blend with one bottle of red line water wetter. You already have the fans coming on early
2- underdrive pulley--to slow the water pump cavitation issues
3- no oil or a/c sceens on the track
4- synthetic oil(you didnt mention if you were running this) it does run the engine cooler
I even took the front bucktooth out of my air dam to increase air flow.
hell put a mid pipe on for the track--its only 5 bolts and takes less than an hr to do
the cars power band is such you can shift at 8.5 with no real lost. do it if it is right. Dont overdrive the car.
olddragger

 

1. I was running 50/50 with water wetter. Are you suggesting 70/30 coolant/water?

2. Is water pump cavitation a big problem on this car? Which pulley do you recommend?

3. I did have oil and AC screens on the car. I also have the RB ram air partially blocking the opening as well. I wonder if that also contributed to the problem.

4. I use Royal Purple in the car.

Does a midpipe help keep the engine running cooler?


Staticlag, is your setup similar to mine?

 

The scary thing, is there may be a number of RX-8 people running 50/50 in hot weather. You also have to watch out for mindless Mazda Techs or mechanics that might be putting straight 50/50 or mixing TAP WATER with your anti-freeze. Tap water is bad because it contains all kinds of unwanted minerals and metals that lead to corrision and bad performance of your cooling system. Distilled Water is the best.

I think 70/30 (Distilled Water/Anti-freeze (with redline water wetter)) would be a better combination in hot weather. You can also stay with this combo all year round if you are not in an area that is subject to below 32F temps. Keep in mind your manual states 65/35 (water/anti-freeze) above 3 degrees F temps. 70/30 or 75/25 would work for hot weather performance. Higher, if your racing...

 

1) yep, 70/30 with WW
2) yep AP pulley
3) I kept them on
4) yup, 10w30

Running a straght pipe, 100 octane highpower unleaded gas.

battery relocated, excess underhood plastic removed.

However I never went easy on it, WOT all the time except switching to partial throttle going into corners. That and 45 minute runs. If we were supposed to shift at 8.5K, then why is the revlimiter at 9.3K?

 

I don't understand the 70/30 water/coolant. Won't less coolant cause it to boil over sooner? Or does the extra water cool the engine down that much better?

 

Pure H2O can carry more/get rid of heat better than Coolant.

Boiling point has little to do when its in a pressurized system.

 

Damn, RB street flash+RP supercat=BAD combo? That sucks. So, RB Race flash & street flash are both killing supercats? But, the OEM cat can take a Street flash?

I'm glad I didn't rush out and get the flash like I wanted to.

 

water is a much better heat scrubber that coolant--pressurized system so it doesnt boil at 212F However dont run 100h20 distilled--unless you change it out after the track and use at least 2 bottles of water wetter--pump needs a little lube.
rb's flash is well worth the cost just to get the fans turned on sooner.(via stock box not an add on).
the extra 0.8K redline can be useful--may make a shift unnecessary when your gearing is not exactly right--this will help lap time a little and make the course easier to drive---however using the high rpm band all the time really adds to coolant stress. try short shifting at 8.5 --see if it affects you any--you maybe surprised. Your engine will like you as the temps will be noticeably lower. avoid high rpm partial throttle scenarios--that really hurts(cat also). If you are at partial throttle--high rpm--then shift to higher gear and use partial throttle--cuts the rpms down--it all adds up.
two areas at road atlanta i do this.
Also you would be surprised how much screens block airflow. Now if you have the need for projectile protection then by all means use them! they are great for that.
The "grill" area is not really affective in providing airflow to the a/c radiator area. RB got it right. The flow comes from the airdam area--thats why i removed the bucktooth(rotar symblom)
see the pic.
olddragger

 

CRH, where's my clutch bracket? She's clicking...

Seriously though.. if you are concerned about how much the screens inhibit airflow, try taking off your radiator and swinging it through the air to see how much drag it will generate I admit I have no hard numbers to back this up but I don't think the screens should inhibit airflow any more than the radiator / coolers already do. That is why the rad fan is there - to pull air through the radiator and create a low pressure area there to allow more air to flow in from the front of the car. Rebuttals welcome....

On a similar note, has anyone tried fitting oil cooler fans? Any gains? Any kits in the making?

Oh, and for point 3 above - removing the cat for track duty will save it because it will not be on the car to suffer the abuse of prolonged WOT

 

Getting back to the original question - RB flash causing overheating . I can't see any possible reason for that to occur - except perhaps if you were taking it out to the new 9300 rev limit all the time . But leaning out the mixture & turning on the fans early - seems unlikely to be the cause .

 

Wow, 45 minutes in 100 degree weather?

I can only handle about 30 minutes or so in hot weather. Don't want to work myself (or the car) too hard.

Were you above 8k for sustained periods? I mean we're all running hard at the track from 100% braking to WOT, but I usually go from 6k to 9k RPMs and then shift instead of riding it at 8.5k for any sustained periods of time.

i.e. if the fastest I can enter through a corner is in 2nd gear at 8.5k RPMs, I'll just go ahead and do it in 3rd instead of 2nd. I've seen folks drive their cars really hard by going down into 2nd and put them very close or above redline.

Mostly track dependent I guess, but curious what everyone's doing.

 

I was at a car show and this drift car had a couple of what looked like PC case fans (120mm) to cool his oil coolers. It would probably only benefit him because he wouldn't usually have enough speed to generate good air flow through there.

 

Yes, not sure and yes.

 

Wow that's pretty funny... They do make some pretty powerful PC fans. They are not exactly rugged, but quite cheap, so should be fairly cost-effective...

Now about rigging up a bottle of compressed air upside down to blast the cold liquid stuff out ever so often? As long as don't damage the fins by over-cooling, this might be an option for track days if you really have problems with overheating.

As to the OP's question - RB flash makes it run leaner, and if I'm not mistaken leaner = hotter?

 

i used this screen "test"
1 take your screen
2- cut a 1 " wide 3" long of regular notebook paper
3- turn on a regular floor"box" fan
4- place your screen up agaisnt the fan
5- hold the paper up agaisnt the screen with you finger
6- visually remember how high the paper blew
7- remove the screen and hold the paper where it was.
you will be very surprised how much air is being blocked!
imho dont need fans on the coolers--what we need is less blocking on the back of the coolers and no screens. If you have to idle a long time or you are in a low speed congested enviroment--need a better flowing coolers --not fans.
course how hot is to hot for youre oil? Thats another can of worms.
with the engine we have what you want is the coolant temp and the oil temp very close to one another.
olddragger

 

your cat was likely heading south long before you got the RB flash, plenty of people fried Supercats with the OE factory flash

 

you can go so far as to gut the thermostat, plug up the bypass and use a 90/10 mixture. BUT street life would be interesting in the winter!
olddragger

 

its true i was being ungenerous. And the trackday, I redlined every shift did pretty good too. Though the 350z and EVOs spanked me.

I was thinking of getting a stock hood, cutting a scoop hole and putting the fluidyne cooler right under it. A little project for after I finish paying off some stuff. Making a custom bracket that will bolt up somewhere.

 

The problem with this test is that behind the screens there is an oil cooler and the oil cooler by itself is quite dense and will block a lot of airflow. Though a bare screen will block a lot of airflow, the oil cooler could already be blocking so much airflow that the effect of adding a porous screen would be negligible.

 

And surprisingly not a soul mentioned the obvious. If he's running at a sustained higher rpm than most track guys, he probably is experiencing cavitation and may just need THE HIGH-FLOW WATER PUMP from MAZMART (Guaranteed not to cavitate at 10k).

Wow, that was shameless .

Paul.

 

is it for sale yet? cost?

 

I was shifting around 9k rpm, same as before I got the flash. I am definitely interested in this product. Do you have a link to it? If I get the AP pulley, would it accomplish the same thing?

 

didnt know it was ready yet! Yes the water pump is the heart of the cooling system! I would not upgrade the radiator with it! I certainly would not FI without it!
You would be surprised if you removed your water pump and examined it closely.
screens? Dont block a lot? well every bit helps. its a personnel choice.
olddragger