RX7Club helped us fix It! We raced It! Now we need more help! :) Fan Questions:
 

Good tuesday RX7CLub.com We rallx'ed the RX7 to shake it down and see how it feels. The day went well, it was my first time rallyx'ing in Fun wheel drive, and it was mikes first rallyx. Testing went well, we learned alot! namely that we have a catastrophic issue with our cooling system, we need MUCH softer springs to play in the dirt and we need proper gloves!

So here is where you come in.

We did our morning runs without much alarm the front end was super rickety (400lb spings DO NOT BELONG IN RALLY) but held together and was predictable ie. nothing wonky going on. in the morning we did the driver swaps with the car off. No park brake and race is in a banked field. After lunch we learned our lesson and brought a chock with us from the truck. This allowed us to keep the car running as she does not like to start cold. (1.Low compression?=rebuild?) we noticed about 3 runs in the car would get really hot on the grid and in line. we got another 3 runs in before it was kissing 270 and coolant was sprouting out of the over flow tank. (2. what temp is too hot, what do i look for damage from over heating?) We run a Ron Davis radiator, possibly from AWR (car was covered with awr stickers when we got it). We obviously need a fan shroud and fan since we are not track racing. (3. 1 fan or 2? what are your experiences/opinions?) and also (4. if anyone has one for sale and can get it to me in NH by 12/5 PM me) Lastly i am considering bringing a blower to stick in the front of the car during grid, not as sole solution but a redundant safety measure.

Please review and advise highlighted inquiries.

Dash cam vids coming soon!

270? O.o

definitely need to work on the cooling ducting, fans and probably a high flow racing thermostat.

Thanks for your input but that shed no light on any of my questions.

sure it did, im surprised you haven't melted a coolant seal which imo is your first priority. find the highest cfm fan that fits your radiator and make sure you duct through the radiator, making sure the undertray is intact. a high flow thermostat will also help.


cold start issues are usually not compression related, hot start issues are. but a compression test still may be insightful.

240 is probably about thermal meltdown temps, even track drivers should try to avoid this number, and its ideal to keep it way below that...

at 270 your oil temps are probably mid 300's and the oil is literally boiling and burning which will lead to premature engine failure as well, also make sure your oil cooler is clean and not blocked.

How would I check for the coolant seal failure. And yes the car starts great cold but not hot. We will clean and throw our spare oil cooler in over the winter. We will also take a look at the oil. On the Dyno the car did not push over 160 So I'm thinking the fan will fix the problem.
It did start surging when it started to get hot.
Thank you for the more robust response Rotary Evolution.

N/A or turbo??

check to see if you have the right PSI on the rad cap or might be time to get a new one .

to check for failure pull the plugs and check for coolant or crank with plugs out.

by the sounds of it your not running a fan at the moment?? that's probably the reason its overheating, you need a fan, track racing or not.
use a stock clutch fan and the shroud if you can.
or run 10" twin thermos or a 16" single but depends on the size of your radiator.

and yea get a comp test to see if its allgood.

yeah, if you're not running a fan you're not listening to the right people. a fan is still very necessary whenever your speed drops below around 80mph.

yea that's for sure, especially if your going to drive it flat stick through dirt in a rally
wich I don't know how he could do that to a rx7 lol :scratch::scratch:.

I love new RX7 racers who just don't understand and trust me I was there once right with you. If you haven't killed your motor yet, cross your fingers that it keeps going. These motors are a lot more sensitive to overheating than a traditional piston engine car. Testing for a coolant seal failure is traditionally compression loss, pressurized coolant system and coolant use out the tail pipe.

I personally would not run any car without a fan that has times operating at speeds lower than 50 mph. Before I would even go out again in the car I would change the oil, add coolant, add a remote controlled electric fan, add the extra oil cooler and make sure that all the ducting is good and so is the rad. If it gets even a little clogged with dirt, temps can go sky high.

Also, if you are out there buzzing the snot out of the motor all the time (which you should be), you are operating outside of the water pumps happy place and you are cavitating the coolant in the water pump. This means that the pump impeller is overspeeding and inducing air bubbles and poor flow through the rest of the system. Most guys again change the speed of the water pump to prevent this and slow down the pump.

Its not worth destroying an engine by running it again without doing these things and everything else that people are telling you. As long as the support systems are good, these engines can go for years. Just make a few errors and you can destroy a brand new motor in moments.

Eric

thank you all for your responses (and thinly veiled ridicule ;-) )

firstly, i you have not rallied you have not lived.


We were there to test not to compete, so no we were not pegging it the whole time, the car never hit the shift buzzer. We did not build the car, and yes amateur omission as it is, i did not even consider the fan issue before the race, now I am working on sourcing a fan for this monster radiator, but I am unsure on this topic 3. 1 fan or 2? what are your experiences/opinions? I work at a sheet metal company so i was considering fabing my own shroud but need to know which is more efficient. our undertray and rad ducting is in perfect condition and we have all the room in the world to mount the fan. I am dont want to assume that two fans is better than one hence my question. Now with a fan, 1 or 2, should i still bring a blower to keep air temps down on the grid or can I rely on the fans to do that job?

I dont have alot of experience with these cars and am cutting my teeth on a race only vehicle, thusly, I know expensive mistakes will happen.

As i said we DO have hot start issues and are rebuilding a spare because of it.

thermostat, and rad cap are both for race use and function. I have not had a chance to pressure test the cooling system since the race as i went in for surgery the day after (monday). I am not going to be heart broken if we blew this motor, frankly, I never expected it to run in the first place, but as it sits she starts and runs as happily as she did before the race.
thank you for your advice.
if anyone could suggest a fan setup that would be excellent thank you.

Eric,
I noticed when we bought this car that the water pump pulley seemed a different size, is this what you are referring too?

generally i try to stick with 1 large fan. 2 fans usually draws more current and is difficult to fit the square framed radiators. try to stick with something OE like a taurus fan. i run a black magic on my car but they are problematic and could cost you more money than it is worth in additional repairs.

Why something OE? this is a race only application.

i haven't had luck with aftermarket fans. sure some will work but being heavy duty they tend to burn themselves out. OE fans need to survive tens of thousands of hours of use. reliability is a better offset than a few more CFM.

Trust me when I say I am not being sarcastic. My first experiences with these cars was with a race car and I had to learn everything from scratch like you are. Regarding the water pump pulley, it should be a fair bit larger than stock and the eccentric shaft pulley should be smaller (crankshaft). Different companies do this differently and there are different underdrive ratios available based on you target rpm range. I also agree in using factory electric fans. They never, well rarely, break and they move a lot of air. Aftermarket ones just don't seem as robust or work as well.

I have never rallied, but I did race motocross, direct drive FIA type karts and drag before moving into road racing.

Eric

The water pump pulley is definitely larger than stock, but i am unsure of the eshaft pulley. The car did not budge from 160 on the dyno so i am thinking that my only problems are lack of airflow on the grid. thanks for that bit though Eric, the functionality of the waterpump pulley size did not occur to me. I appreciate your insight.

so some large OE fan it is. im thinking a "taurus fan," may be a bit small for this radiator though.

https://cimg7.ibsrv.net/gimg/www.rx7...c91b373297.jpg

not by much, i have seen them on large aftermarket radiators almost as big as the ron davis.

Thanks for your advice RotaryEvolution. I am looking into it now.

In rotary race cars I always like to go bigger/more. Huge rad, more oil cooling than you possibly think you can use and a huge ass fan. The cars so some funky things at times and I would rather have to tape off most of my grill for the car to reach temps than look for ways to keep it cool. For example even after racing it for years, during the 3 hour enduro this fall we needed to drill 5 x 3" holes in the nose for more air flow. Why, I don't know, we just had to and then everything worked well again.

Could have been fuel difference, the last tune made more power I don't know, it just needed more air.

Eric

OE stuff works! remember that, it'll be handy later

X's eleventy.

Eric

Me and a few of the V8 guys are all running the same SPAL electric fan and it works really well, but it's expensive...

https://webstore.spalusa.com/en-us/p...-12v-dual.aspx

Can the Taurus E-fans be hooked up to run soley off of a switch? IE no thermo sensor? if so can they be setup to run on High only? all the write ups i see involve thermosensors. I want this to be as simple as possible.

yeah, all you need to do is wire directly off the battery to an on/off switch then to the fan high speed circuit, place a 30a fuse near the battery. run the ground wire somewhere near the fan that is a solid grounding point.

in fact im putting a ford thunderchicken fan on my car right now, that damn flex a lite black magic piece of garbage can rot in the trash.

$17 20 year old used OEM part replaces 3 year old $300 new part, go figure. it's even bigger than my already oversize radiator.. it'd probably fit the ron davis perfectly.

the flex a lite started locking up on a scorching hot day, but not before the temp hit 260 on my gauge did i notice as the car started to finally give me bucking symptoms, on a brand new engine that i only put about 800 miles on(the engine is fine but it did cause a few of my studs to begin seeping coolant so i need to yank it out and reseal them).