Thin High CFM Electric Fans

[SSL]

I'm trying to find a higher CFM solution with limited mounting depth (< 4"). The Arizona summers are too hot without the A/C but the engine temp creep (during stop and go driving) is keeping me off the road.

Current setup:
502 ('68 Camaro) with a long water pump and A/C
Be Cool big block aluminum rad
2780CFM Dual Spal 11" fans
Spal pwm controller

Does anyone have experience with the following Derale fans or have any other recommendations?
http://store.summitracing.com/partde...0&autoview=sku

Thanks,
Steve

[Yelcamino]

Give Tim at Ron Davis Racing a call (Glendale, AZ). I spoke with him the other day and he said they have a new thin, high cfm fan being added to their inventory. He should be able to help you.

http://www.rondavisradiators.com/Welcome.htm

[SSL]

Thanks Herb. I'll give them Ron Davis a try.

Anyone else have any ideas?

[nickv]

SSL - I've got a similar setup - just a few cubes short - 468 -
What were the temps with the BeCool and dual spal setup with and without AC? I'm out here in Texas and have an AFCO aluminum dual 1" core radiator and a 18" flexalite fan and clutch. Was going to go the BeCool route but...

[gmachinz]

To use a truly HO fan such as Mark VIII or similar, you can use a SB radiator and go with the short style water pump on BB 1st gens and it will give you the clearance needed. When swapping to an electric fan especially a good one, the cfm rating is often times much higher than any mechanical fan-so the rate of heat exchange is higher and along with the replacement radiator usually being aluminum instead of copper/brass, you swing the balance even further in your favor in terms of using a SB radiator when it comes to space. Sheer coolant volume is important when deciding on a radiator but just as important is how you plan to pull heat out of it. You don't always need a BB radiator just because you have a BB. High quality fans that can pull some serious air will offset it every time. Trimmed to fit a 1st gen radiator support, we get the mounting depths down to 5" on the Mark VIII fans and we can fit them into 67-69 Camaros just fine. Oddly, the clearance variances can be as much as 1" though which is why we highly stress measuring accurately before ordering one. If you are designing a cooling system, pick a fan first and build around it. -Jabin

[andrewb70]

Before throwing money at the problem, tell us whats wrong. Your current setup should be more than up to the task of cooling your combo. I have the identical setup in my GTO and I have never had any issues. I drove the car the other day when it was over 100 here in Kentucky. Not exactly Arizona heat, but fairly hot.

Andrew

[SSL]

I just completed the car and it only has about 30 miles on it since. So, the data is a bit limited...

#1) I've corrected a lean condition with the accelerator pump and primary jets (Holley 850) which corrected a low speed temp increase to ~215 before I shut it down. According to the A/F meter, it's not running lean at any point in the RPM range.

#2) Timing is at 10 degrees initial and 36 total.

#3) If the car idles in the garage without driving and with the A/C ON the temp will very slowly increase. It will need to be shut down (215+) after about 10-15mins on 110 degree day.

#4) The temp sending unit is in the passenger head and I notice an increase in temp under hard acceleration and when i come to a stop the cooling system cannot recover and temp slowly increases.

Thanks again for the help. I hate throwing money at the problem and not being successful...

[andrewb70]

The first thing I would do is make sure that your system is well burped and you have no air pockets trapped in the heads. One thing that I have found to help is raising the front of the car as high as possible. This puts the radiator up high compared to the engine. Take your time and run the engine through a couple of heating and cooling cycles. Just in the garage. Make sure that the thermostat is opening. After going through this procedure you will know that the system is as full as possible and void of air pockets. If the problem persists then we can take it from there.

Andrew

[KUL FIR CHICK N]

I'd rather see the sending unit in the manifold under the thermostat rather than in the head. I've had a problem with sending units picking up too much radiant heat from the headers and making them read high. At the least, fabricate a heat shield to test the theory on your car. Also, be sure the fan shroud is properly sealed to the radiator face using a suitable foam that can handle the temps.

As far as fan ratings go, the CFM ratings you usually see in print are not worth the paper they're printed on. Those ratings are in free air, not against a load. Some fans that blow massive numbers in free air don't work well against the restriction of a radiator and condenser.

I use amperage draw as a better guide to see how much work the fan is doing. The Mark VIII fan draws approximately 30A when installed in the vehicle. It spikes to 100A on start up. If the ad says 3500cfm @ 20A you can bet its bogus.

As Andrew said, your components should be more than up to the task of cooling your engine. The dual Spal setup is plenty. We've got a vehicle here with a 705 cu. in. motor making over 1K HP using a single 18" electric fan drawing 30A and a copper/brass radiator that never gets over 180deg. in traffic, on the highway, or just idling in the shop. Trust me, this car gets driven hard, and the cooling system has never even been on the radar screen.

[SSL]

Your comments about amps vs. CFM match exactly to a conversation I had with a tech rep from Ron Davis. Being an electrical engineer myself, I am a believer on the topic. Fans need to pull big current to pull big CFM values expecially under load when being restricted by the rad and A/C condenser.

Glad to hear you also agree the current setup should work. I'd rather fix this with my head (with help of course) rather than my wallet...

It already has foam closing all gaps between the shroud and the rad but none between the rad and the A/C condensor. I originally put the temp sending unit in the manifold next to the thermostat but found it to be visually ugly and moved it to the head. I could try a heat shield to avoid header crosstalk.

After looking at it further, there are a few other items that need to be highlighted:
1) The fans are seeing a voltage drop (~10.5V) when ON. Thought I had the 8 guage power lead running to the starter but need to trace it. Could be causing a reduced fan CFM...
2) The car sat for a few years at the body shop (long story) and rad has some type of crusty substance on the cap and a little viewable from the filler. Should I do a flush?
3) Antifreeze ratio is about 50:50.
4) Have a bottle of Water Wetter but haven't tried it yet. Does this stuff really work?

[KUL FIR CHICK N]

One clarification, the fans will draw less when working against the condenser/radiator than in free air because they're moving less air. Should be =/> 30A installed.

1. 10.5v BAD Also check the terminals in the connector and at the relay. you may need a 70A relay for reliability due to inrush.
2. Anything between the coolant and the tube surface will reduce efficiency.
3. Good ratio, but in the summer you could raise the water content for more efficiency. Keep the freeze protection above 25F to protect your heater core.
4. It works, but shouldn't be needed.

[gmachinz]

I would say that your gauge is correct with the temperature it's giving based on the sensor location-if you were to move it to the intake, I bet you'd see about 190-195-ish. As for where you have the power for the fan routed, I would have to say your voltage drop is due to heat. Heat increases resistance and it can be internally from a high amp drawing device, or from external sources like hot exhaust. The other is length, it induces heat if the wire size is too small to carry the load over the distance. I would run the fan off the alternator charge post instead of the battery if you are using the internally regulated type. There are better ways to make the most of your fan and charging system in general but that's another story. All in all, I don't see anything wrong with a 215 temp reading taken at the head. -Jabin

[Steve Chryssos]

I have yet to see a slim fan that pulls a lot of air. In fact, I've seen some that you can stop with your hand. Might as use a mouse on a treadmill to turn the fan. Feed it a lot of cheese. Run the biggest motor you can fit.

As for your problem, I would also try sealing off the core support to upper valence with some cardboard to prevent hot air from recirculating to the front of the radiator. This is a common problem at low speeds/idle. DON'T seal off top and bottom. Just break off the recircultion by sealing off top or bottom. Sealing off both top and bottom can cause airflow to stall at higher speeds.
Cooling system design can be something of a black art. Stick with it and try to preserve the scientific method by testing one change at a time.
Water Wetter works well at stabilizing a properly functioning cooling system, but cannot readily cure cooling system problems.

[SSL]

Hmmm... I seem to recall very original first gen Camaro's with A/C having a foam-like piece that bridged the gap between the rad and the core support. Has anyone else seen this too? It's probably to keep hot air from recirculating as you suggested. One more thing to try...

Has anyone tried to mount a Mark VIII fan without a shroud? What would the minimum mounting depth be?

[KUL FIR CHICK N]

Factory air Camaros had the foam strip or a rubber extrusion along the top of the core support for that reason. I have found in testing A/C systems that when I was parked at a stop light, where the car was pointing up a slope, the hot air would run up over the core support and back into the condenser. This condition was so severe that it would run the head pressures up high enough to kick out the safety switch before the light turned. It would only do this when the car was parked on an up-hill slope though. I had the car instrumented, so it was relatively easy to diagnose. Replacing the factory strip solved the problem.

Note, I don't think this is your overheating problem, but it may help.

[gmachinz]

Mark VIII fan mounting depth is 5.75" or you can trim off about 3/4" to give you 5.25". On a stock or drop-in replacement type radiator, they are almost a direct fit. You just need to slightly notch the fan shroud on the Mark VIII for clearance at the automatic cooling lines/radiator pass. side tank if so equipped and for the petcock in some situations. We do them all the time. Drop me a line if you need any help. -Jabin

[SSL]

Well it's not 110 degrees today (91 at the time) but it looks like burping the system has done the trick. The car now runs 185 on the road (thermostat value) and never got above 195 at idle. Thanks for all of the tips! Nice not having the throw more money at it!

Looks like the fan voltage issue is due to my 1-wire 140A Powermaster alternator. I will be posting a new thread in the Electrical Section to discuss this problem.

Thanks again!
Steve

[andrewb70]

Well it's not 110 degrees today (91 at the time) but it looks like burping the system has done the trick. The car now runs 185 on the road (thermostat value) and never got above 195 at idle. Thanks for all of the tips! Nice not having the throw more money at it!

Looks like the fan voltage issue is due to my 1-wire 140A Powermaster alternator. I will be posting a new thread in the Electrical Section to discuss this problem.

Thanks again!
Steve

Awesome!

Incidently I run a Mr. Amp alternator from Davis Unified Ignitions. It rocks. As soon as the car starts I see 14.7 volts and at no time does it drop, even when the sub woofer is thumping.

Andrew