Horsepower = Heat?

[DocDirk]

Well over the winter I found that I got decent cooling even at idle on my 533 BB Ford powered Cobra. It has a 4 core 19 x 28" radiator with a 16" puller fan behind a shroud. Now that the temps are in the high 70's I'm running fine with the ram air effect at over 40mph but in stop and go I have to pull over because it's shortly at 225. I realize this type of question has been asked in one form or another on the forum already and I've read all the "overheating" and "coolant/cooling" threads here on the forum and have everything pretty well to spec.

My question is, can I consider a Flexalite twin 13" fan behind its own shroud with a 2760 to 4600 cfm rating a likely solution to this problem if all other parameters are in sync? (It fits my radiator to a T size wise). I bet mine pulls about 1600-1900 cfm at best. I have a heavy duty high output alternator so I'm thinking the amperage draw isn't likely to be a problem. I'll need to rewire a bit heavier gauge I suppose, but I wonder if anyone else has tried one of these behind a thick radiator on a hot engine. The Flexalite website has a disclaimer that states "Flexalite does not recommend the use of electric fans with four core radiators." I called and spoke to them and they say that a radiator that thick is tough for any fan to pull well through... I've read of some folks switching to a thinner 2 or 3 core radiator with good results.... hate to spend $450 and the labor to yank and install if I'm on the wrong track here. AND it gets over 90 most days in the summer here in my part of Krazyfornica

Thanks for any input!

Dirk

[Silverback51]

It could be more than just the radiator.

What about the waterpump? Are you running undersize pulleys?

[vector1]

i remember waaaay back when i had a radiator made for a mustang the guy spec'd a 2 core with either 1" or 1.25" cores, remember him saying much over this and it was hard to get air to flow throw. this was on a rr mustang and didn't use a fan. fwiw

[Rick Parker]

This is the Fluidyne radiator used by Shelby for ALL of his cars regardless of the engine size. I believe it has 3 rows of 1" tubes.
[IMG][/IMG]

[DocDirk]

Yep the pulley for the water pump and crank are properly sized for good pump action thanks.

Rick, I was just gazing at that photo in your gallery yesterday, wondering why it would work as it's not shrouded, but perhaps the wider fan makes it happen.

What I would like to know also is: Has anyone used a Flexalite dual fan to cool their monster?

Thanks, I'm hoping to play in the sun with this toy this coming Hot Hot Summer

Dirk

[Rick Parker]

The fan pulls an enormous amount of air, but I do have a Small Block. The fins are somewhat course compared to others I have seem and may permit more flow??

[tmareina]

I've got a 3 core with a 16" puller that puts out 3948cfm. On the road at 35 or faster I don't even need to turn the fan on and it runs at about 180+/- ....only during cruises at Hot August Nights when the temp is 90+ does it get to about 210 after I've been in bumper to bumper traffic (5-10mph) for about 45 minutes or so. At that point I think the problem is evacuating the heat out of the engine compartment.

Tom

[Rick Parker]

If you are currently using Antifreeze Coolant you might try using distilled water and Redline Water Weter in lieu of the coolant. It will drop the temps about 10-15 degrees. Flush the system first. Your radiator setup looks well sized from what I could see.

[RICK LAKE]

DocDirk Doc Has this problem been going one since day 1? Is the motor new or does it have 2-3 thousand miles on it? What is the thermostat opening #. Do you see a 20-30 degree drop in the temp gauge when the thermostat opens? 50/50 coolant in the cars coolant system? That is a big motor in a small space. 225 is not that crazy of a number on hot days. Try this, do a heavy taping of your hood latches to hold open the back of the hood and give the hot air a place to go, Go for your normal road run and see how hot the motor gets with this opening. If the temps are alot lower than there is no problem with the motor. You need to fine a way to help remove the hot air under the hood. Heat wrap on the headers is a good start. Get yourself a infrared gun for temp readings and check the radiator from top to bottom on both sides and see what the readings are. I have added 2 4" bildge fans to help remove hot air when racing. This has helped to lower temps. Is your radiator straight up and down or at a 30 degree angle? If it is at an angle you may want to add a splitter in the opening to help the air get directed through the whole radiator. ERA sells the with their cars. Rick L. Ps Doc I looked to your pulleys and the water pump is smaller than the crank. This is a undersize setup. The coolant flow for your motor may not be enough. I ran a set of March pulleys on my FE an the water pump was spinning too slow. This was with a high flow pump. Crank pulley and water pump need to be 1-1. Are they March? I was told the same thing from March about the problem of overheating was EVERYTHING but their pulleys. I changed radiators, thermostats to a Dodge larger one, only the connection to the waterpump and radiator are rubber, to stop and collaspe on the lines, removed the intake and cleaned out the ports on the manifold of flashing where the coolant flows. I ended up going with stock size upper and lower pulleys from ASP to stop the heating issues. Both pulleys are about 6" ASP builds custom pulleys and ships them in 24 hours. I have had no issue with over heating for the last 5 years. A also went from a 452, 9.2 compression motor to a 482 with 10.5 and over 100+ added HP and torque. Rick

[undy]

I fought this for a couple years and here's what I found..

If your 4 row is brass it won't do as good a job as a 2/3 row fluidine/Be Cool or Griffin with the 1" or 1 1/4" tubes.

Ensure your water pump pulley isn't under-driven. March under-drives their crap and hurts our coolant challenged Cobras.

Make sure you run a "performance" T-STAT, such as Mr. Gasket (robertshaw made). They will flow more, under all conditions.

You can bypass the external water pump bypass for additional cooling as long as you modify the thermostat.

Ensure your puller fan is fully shrouded.

Ensure the inlet of your radiator is fully shrouded, all the way to the "mouth" at the front of the car. You WILL recirc hot air from the cooling fan's outlet if you don't at idle in traffic.

Flexalite drastically OVER-RATES their fans' CFM capabilities. "Professional grade" fans, such as Spal, tend to have true ratings.

Ensure your timing and fuel mixtures are correct. Lean conditions and incorrect timing can aggravate coolant temps.

***most important!! Make sure your electrical system is up to the task of hi-amp draw fans. Alternators/wiring and rugulators (read: Painless wiring harnesses) are NOT usually up to the task with under-sized conductors. With the usual accessories running at idle, check your voltage to and at the fan. Mine was 10.2 volts before I straightened things out!

Dave

[Tom Kirkham]

Originally Posted by undy

Ensure your puller fan is fully shrouded.

Ensure the inlet of your radiator is fully shrouded, all the way to the "mouth" at the front of the car. You WILL recirc hot air from the cooling fan's outlet if you don't at idle in traffic.

Ensure your timing and fuel mixtures are correct. Lean conditions and incorrect timing can aggravate coolant temps.

Dave

What Dave said is spot on. It is important to make sure ALL of the air flow goes through the rad.

Most engine builders set the timing on the engine very lazy. They do this to prevent the engine from detonating. You need to set your timing to come in quick and aggressive, yet still not detonate. With the timing retarded your engine will run hot and sluggish. This is a balancing act and you will need to drive the car and tune it.

[DocDirk]

Originally Posted by RICK LAKE

DocDirk Doc Has this problem been going one since day 1? Is the motor new or does it have 2-3 thousand miles on it? What is the thermostat opening #. Do you see a 20-30 degree drop in the temp gauge when the thermostat opens? 50/50 coolant in the cars coolant system? That is a big motor in a small space. 225 is not that crazy of a number on hot days. Try this, do a heavy taping of your hood latches to hold open the back of the hood and give the hot air a place to go, Go for your normal road run and see how hot the motor gets with this opening. If the temps are alot lower than there is no problem with the motor. You need to fine a way to help remove the hot air under the hood. Heat wrap on the headers is a good start. Get yourself a infrared gun for temp readings and check the radiator from top to bottom on both sides and see what the readings are. I have added 2 4" bildge fans to help remove hot air when racing. This has helped to lower temps. Is your radiator straight up and down or at a 30 degree angle? If it is at an angle you may want to add a splitter in the opening to help the air get directed through the whole radiator. ERA sells the with their cars. Rick L. Ps Doc I looked to your pulleys and the water pump is smaller than the crank. This is a undersize setup. The coolant flow for your motor may not be enough. I ran a set of March pulleys on my FE an the water pump was spinning too slow. This was with a high flow pump. Crank pulley and water pump need to be 1-1. Are they March? I was told the same thing from March about the problem of overheating was EVERYTHING but their pulleys. I changed radiators, thermostats to a Dodge larger one, only the connection to the waterpump and radiator are rubber, to stop and collaspe on the lines, removed the intake and cleaned out the ports on the manifold of flashing where the coolant flows. I ended up going with stock size upper and lower pulleys from ASP to stop the heating issues. Both pulleys are about 6" ASP builds custom pulleys and ships them in 24 hours. I have had no issue with over heating for the last 5 years. A also went from a 452, 9.2 compression motor to a 482 with 10.5 and over 100+ added HP and torque. Rick

Rick, the motor has only about 7.5 hours on it, including initial engine dyno. The temperature smoothly climbs to 185-190 while I'm driving at any steady forward velocity over 35 mph, and stays there. I run a 180 degree pro thermostat. Within a few blocks of city driving it begins rising and steadily does so until I pull it over to cool off. Earlier in the year it rose to 235 but I've not allowed that lately, pulling it over if I reach 225. Yes, I'm using March pulleys and the water pump pulley is smaller than the crank pulley. It seems to me that would INCREASE the water pump RPM's vs the crank, and increase output?? Wouldn't a smaller pump pulley turn the water pump more often per crank revolution? I'm confused why equal sized pulleys would increase rather than decrease water pump output per engine RPM? (Unless the higher pulley ratio of a smaller water pump pulley would be pushing TOO much water through the radiator without giving it time to cool off...I have heard of that but only due to running without a thermostat.....) I have a larger than usual scoop on the hood and have yet to isolate the passenger compartment from the engine compartment, so a LOT of heat escapes through the footwells, perhaps the engine compartment venting is going to be worse if there is one, once I get the airflow blocked..... The radiator is straight vertical and the shroud on the fan side is completely sealed except for each side which has about 1/4" full vertical height opening. I've wondered how much sealing that opening would improve flow through the radiator. Shrouding the front makes a lot of sense. That way only external air would be drawn through the radiator. My engine has a 10.5 CR btw. I noticed you weren't so impressed with 225 temp on hot days. At what temp do I worry about hurting the engine actually? ... AND the days will be MUCH hotter in about 3 months.

Thanks for the input everyone!

Dirk

[barabar]

Doc, Arnie here. I'll give you some info that will cool. There is a rule of thumb to use when cooling engines. It is derived based on HP--500HP and below, 2 rows 1" aluminum cores, dual fans, flow 3300 cfm each, 10 gauge copper wire to each fan, complete shroud, high flow 180 degree thermostat. high flow mechanical water pump. 600HP and below----1 1/4" cores and the same criteria as above. 700HP and below---1 1/2" cores and same criteria as above. As a couple guys stated, make sure all the air pulled goes through the radiator. You might have to fabricate a shroud from the nose to the radiator. This should work all the way up to 750HP. Yes there are things you can do---Timing, water fast or slow cfm. When you get much over 750HP your not to streetable and would probably reconfigure the cooling system anyway. Good Luck.

[DocDirk]

Not sure what the size is on the radiator tubes, hoping to find if anyone has used a Flexalite or equivalent dual fan to cool their Cobra engine ??

[Rick Parker]

Yes there have been dual electric fans used by some. In some OEM applications they individually come on at different tempratures and then run simultaniously. Keep in mind they collectively may not move as much air as a single straight blade large diameter fan.

[undy]

The frontal area of our Cobras is comparatively small. It's hard to fit a dual fan setup with our typical "narrow" radiator. If you do, the fans are so small that the single fan will still pull much more than the duals. On the CFM issue, Spal is the only fan mfr that I really trust when it comes to ratings. Working in the HVAC industry you grow to realize all CFM ratings are not the same. CFM ratings on puller fans are specified at inches of mercury. Bluntly spoken, their ability to suck. Most auto fan MFRs rate their fans at 0" of static pressure. That basically is a free air blow. That fan, say rated at 3000 CFM, when bolted up to a radiator shroud with a tight, thick cored radiator will now only draw 2000 CFM. It falls on it's face when you increase the negative static pressure. This can be a result of blade design, motor size and a host of contributing factors. If you're serious about obtaining a certain CFM try asking the MFR for a copy of the "fan curve" diagram for the particular fan you're interested in.

I do run the Flexalite 16" "pre-shrouded" Black Max setup. I think it was primarily intended for the 5.0 crowd. I did a little "shroud sculpting" and viola, it fit like a charm. You'll be surprised how much better your puller fan will cool, being bolted to a well designed shroud over being affixed directly to the face of the radiator's core.

Dave

[barabar]

Doc, Try RON DAVIS Racing Products. He is probably one of the best when it comes to cooling systems, customize or stock. He builds and sells,,radiators, shrouds, fans, etc. Will also answer any questions you might have. Based in AZ. so he is probably heat orientated.