12VSuburban

I would like to know what the cfm's are on a stock coolant fan on the Ram Cummins. I'm getting ready to put electric fans on my Sub. Cummins and want to be sure I'm getting a big enough fan. Any one know what the cfm's are on the regular fan @ say 1,000 rpm, 2,000 rpm, and 3,000 rpm. Obviously, if I go with electric it will always be the same. I do not care for the setup I have now and really want to go electric. I looked at the flex-a-lite fan for the Duramax but my radiator is a little too small. I may try to make it work though. That has 6,000 cfm's. There are others that have 5,900 cfm's and they are the correct measurement. Any help would be appreciated.

Thanks,

12VSuburban.

infidel

Don't know the cfms but the stock fan pulls 23 hp when locked up.
It would be very difficult to find an electric that big.
Some of the big engines are now using hydraulic motors to turn the fan since they can be configured to turn at just the right rpms to match the load and conditions.

BigBlue

IIRC, the stock fan pulls something like 10,000 cfm.

CTD NUT

Actually, the stocker pulls almost 25,000 CFM at 100% full lock. That is why it can suck back 23 hp!

12VSuburban

Wow!!! 25,000 cfm. That is incredible. Is this common knowledge or was this found in a book or how do you know that number? Now, I'm concerned even about putting the Duramax electric fan on. I thought 6,000 cfm was a huge amount but if the stock fan does over 4 times that, it will not even be close to sufficient.

I hope my question doesn't appear that I'm doubting you. I reread before I posted and it could sound that way. I really am not. I guess maybe I am but it is simply because I can't believe they would sell one for the Duramax that only did 6k cfm's if that is the case. I can't believe the Cummins runs hotter than the Duramax.

Hmm, not sure those comments made it any better but I'm really not trying to create a problem. You have simply blown me out of the water by saying the stock is 25,000 cfm.

HappyGA

Cummins is a huge block of iron.. Harder to cool iron than aluminum.

blord

Here is one that supposedly can replace the stock fan in a 94-2001 CTD and is rated at 5500 cfm which is similar to what you are saying is used in the Chevy. Don't know if 3rd gen needs 4 times as much fan. With 90 more HP I guess it is possible.

http://www.drivetrain.com/flexfan/dodgemonster.html

CTD NUT

No offence taken here.....25,000 CFM is easy to discount if you are used to thinking 5500 - 6000 CFM is a lot. If you were to look at purely the hp requirement for the electric fans and the engine driven fan, it isn't difficult to see how the mechanical fan could be flowing 4 times as much air since the hp requirement is well over 4 times as much. Maybe somebody can help me out if I'm wrong here : 1 hp = 720 watts, right? Some of the more powerful off-the-shelf electric fans draw around 15 amps @ 12 volts. Run 2 fans and you are pulling 30 amps which is 360 watts which is a 1/2 hp. It isn't hard to see the huge potential variance in air flow when comparing electric fans to the engine driven fan. if you compare the hp requirements for each.

I have used electric fans extensively in other applications with some success and have learned the hard way about real world air flow requirements for different cooling systems. It is also somewhat alrming to note the difference between the advertised CFM rating of some fans as compared to others. Some manufacturers advertise having 3000 CFM fans that get out flowed by another manufacturers 2200 CFM fan.....so take advertised CFM #'s with a grain of salt. FWIW, Spal seems to be one of the few companies that does not appear to inflate their advertised CFM #'s. You may want to re-read the fine print in the catalogue from the fan manufacturer about the Dmax fans....I have seen a few footnotes indicating that their fans are only intended for light duty use or words to that effect - not very encouraging.

The bottom line is, if you plan on using your CTD in hot climates in a manner in which it was intended (high engine loading, towing etc.), 6000 CFM will not come close to matching the peak air flow requirement to adequately cool a CTD. If you don't have AC and use your rig as a grocery getter, it is possible to use electric fans, otherwise, don't bother.

joefarmer

12VSuburban,

I think you're in the same boat as I am. I can no longer use the stock fan since it interferes with the ATI Superdamper (they overlap each other by ~1/2"). This week I'm testing two 3.8l Taurus electric fans. On 26amp high mode, they can each pull 5000 CFM through a 3" radiator core. They come with the shrouds from the junkyard and they fit side by side over the Ram radiator.

As a side note, I can run this truck without any fan and an 8000lbs trailer as long as it's moving 20mph or more. The water temp will run 180 unless I get stuck in traffic. Then I need to pull over until the traffic clears.

bnraond.

12VSuburban

Your response to my post was encouraging. I have seen people get all torqued when there was any questions and since I'm new, I don't know yet how everyone responds. Thanks for taking the time to reply. I pull a 38' camper weighing in about 8,000 lbs. That is the heaviest thing I pull. I have it turned up quite a bit. Right now, I have a fan that is about 3 or 4 inches away from the radiator with no shroud whatsoever. Basically, if I sit and idle, my a/c goes away. I have gotten the engine warm climbing hills but have never overheated to the point that I was even remotely considering slowing down. (I did slow down because of egt's but not engine coolant temp.). I know my current setup is not putting out very many cfm's at all. Therefore, it seems feasible to me that 5,500 could do what I need done.

Do you know how often, if ever, a Cummins fan is at full lock?

25,000 cfm is basically taking the air completely out of a 3,100 ft^2 home with 8' ceilings in 1 minute through a hole the size of the coolant fan. My Sub has never had cold air when idling so I'm probably going to try one of the electric fans. I will be sure to keep an eye on the temp gage and post any results. I hope to have the new fan on within a month. I will be pulling the camper to a few places over the summer so I will keep you posted on how well it does.

RustyJC

The electric fan(s) will probably take care of the A/C problem when stationary. In fact, my wife's Dodge Durango uses this solution - an electric pusher fan that runs whenever the A/C compressor is running to provide airflow across the condenser with an engine driven fan (with shroud) to cool the radiator.

My experience with a Flex-a-Lite Model 350 system [dual pullers that drew 50A (0.8 HP) in lieu of the engine driven fan] is that they would not cool my 1996 V-10 dually when pulling a 13,500 lb 5th wheel in the Texas Hill Country or in Houston summertime stop-and-go traffic. I replaced them with the engine-driven fan with a new thermal fan clutch, and with no other changes, my cooling problems were solved.

Rusty

12VSuburban

joefarmer,

Let me know how that test works out. My brother has a couple of fans from an Intrepid that he said he thought might be worth trying.

Thanks,

yarddog

I've had my 02 for almost a year now and have only had the fan lock a few times. It was right around 190-200 and there was no mistaking it for anything else, it's loud. Both times it happened I was pulling up a mountain at highway speeds with a trailer, window up and stereo on. It doesn't happen often but it cools the motor almost instantly. I wouldn't want to trade it for an electric.