When to turn on and off cooling fans?

[CarlC]

Hummm, I like to tinker with similar stuff ;-)



Agree with Don to check Vin at the fan(s) vs. input voltage to your controller.

First $0.02 thought is why have the fans on before or at the thermostat fully open point? If the thermostat is 195*, a 200* start - 210* fully on seems appropriate. Trying to dump heat at the thermostatic opening point does not fix an overheat problem.

One other consideration is the fan shrouding. It appears (but hard to judge depth) from the photos that the fan mounting surface is close to the heat exchanger fins/tubes and blocks a large portion of it. During cruise airflow can be blocked, hence reducing airflow and heat rejection. The integrated Spal fan/shroud has rubber flappers on the aft shroud surface to allow air to pass at higher cruise speeds but shut at slow speeds so all air is pulled from the front. The Mark VIII fan in my Camaro has a 1-1/2" deep offset that moves the non-fan portion of the shroud aft away from the heat exchanger and allowing more air to flow through the non-fan area sections. It might be a bit gutterball, but you may want to try removing the fans and shroud and drive the car at cruise speeds. If the temps significantly reduce...... However, Don did not have a problem with a similar setup. I've also never had a problem purging air from the engine.

pwm'ing the pusher fans will help with the alternator draw and subsequent engine speed drawdown at turn-on. Mine did the same with a Mark VIII fan (and melted the electrical plug) but the PWM cured it.

As a point of reference, the Camaro engine is basically a hot-rod LSA (6.3L LS6, bigger cam, heads, TVS1900) and with the C&R radiator, an intercooler that covers the whole radiator support opening, and Mark VIII fan it never gets near 190* even on the hottest days when driving around town.

[nicks67camaro]

The guy Don referenced makes probably the nicest hood vents i've seen. I follow him on instagram but availability is hit or miss. Another option is Track spec. I have the "universal" ones since they didn't offer first gen stuff when i bought mine.

http://trackspecmotorsports.com/shop...n-camaro-67-69

I'm still a little ways off on having mine run

[H2Ogbodies]

If I may add to this thread a bit. That fan shroud no matter who built it is NOT ideal whatsoever. It’s basically blocking off airflow and creating a wall where the only time heat isnshed is once the coolant travels across the fan openings. In other words you need as much surface area exposed for cooling on the radiator fin area-so given how much surface area is blocked off, I’d surmise that shroud is only about 30% effective. The shroud should act as a funnel-not a wall. And then yes those fans are an aftermarket aka Pacific Rim version of the GM LT1 fans and you can do better with them-ideally they should be ran in parallel low/high but they will never keep up with how restrictive that shroud design is. They are cheap to make and fit their radiators-thats the only positives going for it.

How much depth do you have between the accessory drive and your radiator? What is the overall radiator dimensions?

[blitzer454]

I agree that the shroud is somewhat restrictive. The shroud mount does hold the shroud away from the radiator so there is a gap between the shroud and the radiator fins, but I do wonder if this gap is big enough. I called Entropy to see if they would do an exchange for a shroud with bigger fans, but they were unwilling to do an exchange since the shroud and fans are now used. I wasn't too happy about that since they haven't been used that much, plus how can you determine if they're going to work until after you use them? So much for that 100% guarantee they advertise. Anyway they did set me up with a new shroud with two 14 fans which they told me would bolt right up to the radiator, but it didn't. There were three different things wrong with it; it was the wrong size, there was interference with the temp sensor and two of the mounting holes were in the wrong position. So I made my own drawing with the dimensions that it should have been and they have agreed to send me a new shroud to my specs and that's where I'm at right now. I should be getting the 3rd shroud this coming week.

I also went with the Trackspec hood vents. They're not as nice as the ones Don was suggesting but the cost was a lot less and they are far easier to install.

I also ordered a Fluidyne oil cooler and Canton's thermostat which should also arrive this week. When I first built the car I didn't give much thought to needing an oil cooler, but after it was suggested in this thread I started to give it more thought and came to realize that I probably do need an oil cooler as one of the things I did during the build was to swap out the oil pan for one that would clear the frame and steering linkage. I think the new pan has less oil capacity than the original so having the oil cooler will give back some of that lost capacity and provide extra cooling at the same time. All I can say is that I better be able to drive this car through hell and back without it ever overheating.

[andrewb70]

The holes in the hood will do wonders.

Andrew

[joeko23]

I’d like to start off with the fact that I have a 13 ZL1 stock Camaro and just out of curiosity I let the car idle with ac off on a 95 degree humid day. The fans only turned on at around 205 at relatively low speed they then got faster but temp stayed right around 213-215 degrees. So I think the temps you are seeing are normal. I would recommend you join camaro5.com and ask more zl1 owners but again I think these are normal temps.

This may be kind of late but hexvents.com also makes reasonably priced excellent quality vents.

Additionally, I don’t think you have a problem with the entropy fans or shroud. Your problem may be in the heat exchanger fans blocking off air flow. Fans on a heat exchanger are basically for drag racing to cool the supercharger coolant quicker when the car is between racing. Again you can confirm this with camaro5. No one drives with the heat exchanger fans on because you already have air flow. Try to take the heat exchanger fans off if you can. BUT I think 213 is normal temp for just sitting still in 100 degree weather.

[Tweak]

I hope this helps.
I have done a fare bit of airflow testing, all be it at an amateur level. The first thing to be aware of is that air takes the path of least resistance. Low pressure will always be dominated by high pressure and will try to take the shortest path possible.
I think someone mentioned it earlier, but yes you defiantly have a poor fan shroud design. If you create a difference in pressure across your radiator, then you will indeed have hot spots that effectively work against your cooling potential.
For instance, if your radiator sits behind the core support where there is no opening, then the air flow through your radiator will be inconsistent and compromised.

Forgive me, but i am not aware of pushing fans behind the radiator. Seems to go against logic with the natural effect of the car moving forward and air passing through radiator. I'm sure in a modern car where the grill area is very closed off for aero, they need to push to remove hot air. (i could be wrong) My 68 camaro has a full open grill that catches a lot of air flow.

When I built my OTR I realized I had created a bit of a "happy accident". Buy leaning the radiator over, it allowed the whole radiator to draw air through with the fans as the core support opening had less of an effect on total air flow and creating hot spots.