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).

is it that easy to wire up thermos??
when its wired up directly to the battery wont it cause the battery to go fat, or wont it use power when the switch is off.

iv also read around some people say the proper way is to wire to the battery with a relay and to a ignition wire but I don't like the idea of messing up loom and have wires catch fire.

his is a racecar, he will have a switch on a panel right next to the driver to manually turn the fan on and off, directly to the battery eliminates possible failure points. will the battery go flat? sure, if he leaves the fan on for an hour while he eats a sammich and forgets about it.


relays work fine, if you know how to utilize them and where to get the source power from, in the case of these fans, generic relays won't quite cut it.

so would it be fine to wire it the same way for a street car with the only the fuse instead of using a relay with it??

how often do the fans fail or the fuse blow?
iv seen a couple thermo wire ups where fans stop working after a while or wires catch fire inside the car not sure if they used a fuse or not that's probably why the wires caught fire instead of the fuse blowing.
i wouldn't want my car to catch fire that's the only reason why i wouldn't do it, but wouldn't mind installing a gilmer belt drive kit.

all circuits should have a fuse, not sure why that's a question.

how often does what fan fail? ive had 3 flex a lite fans fail, i have not seen anyone complain about the ford fans failing and they are already used for years and years.

fans require a lot of amps, it needs heavy gauge wire, good power source and grounding, heavy duty switches and relays otherwise stuff is going to melt down. usually people who melt fuses or wires are using cheap components or inadequate gauge wiring.

haven't really messed about with wiring other than speakers that's why I asked.

what gauge wire would you recommend?

so could you just wire it to the battery with fuses and a relay,
then from the relay to the thermo fan and to a on/off switch and ground what has to be ground.
or do you need to wire it to a ignition wire as well?
or is it just not that easy?

generally i just stick with the gauge wiring that the fan uses. in the case of the taurus fan it looks like 10 for ground and high speed, and 12 for low speed. using a thicker wire won't hurt, but using a smaller gauge wire can overload the wire and melt fuses/wiring.

sweet as never thought it was that easy I might give it a go one day so I can put on a gilmer belt drive kit.

thanks for the info RotaryEvolution.

yw, though i don't recommend just a basic switch for a street driven car. no matter what, you'll forget to turn it on randomly and not notice until bad things start to happen.

yea would be hard to remember every single time to switch it on.

I guess that's why people also wire it up to a ignition wire so the fans turn on/off when the key is turned?

yep, though mine is a little more complicated. it runs through a thermostatic control box that i ripped out of the flex a lite to control low speed and i used a dual control relay off my FC thermoswitch to turn it on high at 210F.

so you can wire them up to be on all the time.
or you can do similar to what you've done and wire it up with adjustable temperature switches to control when the fans work at high or low speed, if that makes sense.

iv also seen people using adjustable radiator probes to control what temps the fan turns on at.

I used a stock water pump housing from an automatic withthe stock thermostatic switch. It works great, turns my aftermarket fan on at 190 and off at 185. Just wired it with a relay.

I will second the advise already given in this thread. I blew a motor due to lack of cooling early in my development of the car: Here is what I learned.

1. 220 and higher is too hot for water. You should strive to never see much over 200.
2. I've not had any trouble with my 2500 CFM flexalite syclon e-fan. I'm not sure i would use one on a street car tho. It works with just a radiator and no A/C but the stock clutch fan is rated for something north of 3300 CFM to deal with rotary heat, idling, a/c etc. My fan on the racecar rarely needs to run, only when sitting still basically.
3. The Koyo N-flow radiator is FAR superior to any other radiator ive used. Multipass radiators make a huge difference in total heat shedding, and i will never buy anything else again. NOTE: Multi-pass is NOT the same as multi-row. Underdrive pulleys pair very well with multipass radiators...which leads me to...
4. ...You MUST underdrive the water pump with a racing underdrive water pump and main pulley. Your alternator pulley can be stock as long as you idle the car at at least 1000 rpm. The stock water pumps cavitate above 6500rpm or so.
5. Ducting is SUPER important. Make sure there is no obvious path where air can bypass the radiator from the front grille. Also i opened up my stock radiator air intake opening in the bumper and use stainless mesh in a completly vertical arrangement to ensure air does not get pushed under the car. If you add mesh to the stock FC bumper profile it will tend to slant forward and ANY slant to the mesh will push air under the car.
6. I use two stock oil coolers piped in parallel, reverse-return arrangement. My oil temps never top 200 with that setup even in 95deg California or Georgia heat right on the bumper of other cars. Some say oil temps should never top 210, others say 250. I've not experienced a failure due to oil temps but i do notice the cooler i can keep the oil, the cooler i can keep the water.
7. My rule of thumb for my car where i'm measuring oil and water temps at the rear iron is that the dash alarms either if they hit 220. I tell my drivers if they get an alarm to immediately go to a high gear and limp the car to the pits. But, that's never happened after i did 1-6 above.

cooling also relies greatly on ambient temperatures. the same cooling system i ran in the desert summer with no fan on would creep to 220F on the freeway at 80mph in 110F ambient heat in las vegas. in florida on a cool 75F day with little humidity it would run 180F at 50mph.

keep in mind that is virtually no load and no throttle, when you start generating heat you notice that even the air being forced into the radiator from speed might not be enough.

I apologize for the lack of updates. As I am sure you know, being one to frequent a race section, often the most progression happens in the wee few days prior to a race. here it goes.

acquire fan and remove radiator:

https://cimg5.ibsrv.net/gimg/www.rx7...3c6b73edc5.jpg


1 beer, 2 strips of 5052, 1 Taurus Efan (thanks rx7club), 1 Ron Davis (apparently custom) racing radiator.


https://cimg6.ibsrv.net/gimg/www.rx7...595ef31d27.jpg


first bracket is bent to the profile of the wide plate that retains the radiator.


https://cimg7.ibsrv.net/gimg/www.rx7...ce14dbbacf.jpg


test fit Note I put a sign under the fan to (successfully) prevent damage to fins


https://cimg8.ibsrv.net/gimg/www.rx7...86d22a3fb5.jpg


1st mockup of fab'd brackets -1


https://cimg9.ibsrv.net/gimg/www.rx7...9759f25e9c.jpg


1st mockup of fab'd brackets -2


https://cimg0.ibsrv.net/gimg/www.rx7...e8b88013cb.jpg


1st install

and then we went to the Wolf Chase RallyCross yesterday. The course was great! very fast and challenging. The morning runs went well, i destroyed a couple cones and got terribly lost once. the fan worked wonders! After lunch the car was hard starting, but she fired and i kept her running between runs on the grid. While pulling up to grid with only three runs remaining i stalled and from that moment on the car would not even engage the starter.


https://cimg1.ibsrv.net/gimg/www.rx7...64b1edacfe.jpg


Stranded, pushed out of the way at grid. <br/>

I was towed back to the pits by the the STI.

We will be looking into an oddyssey battery relocated to the rear and upgraded alternator. feel free to suggest one! Also thinking of rewiring fan to low circuit to see how well it cools.