I am contemplating replacing the mechanical clutch fan with an electric fan on my 1982 E350 based motorhome (Class C) with the 460 big block and C6 automatic transmission. After some significant research, I have decided to replace the fan and the radiator the same time. I've decided on an Aluminum radiator coupled with 4,000 cfm of electric fan assist. My primary problem is the choice between a crossflow and a downflow radiator. The original equipment for the 1982 motorhome was a downflow unit, but the crossflow units are more efficient and are used exclusively in more modern vehicles. I appear to have the space for a Summit Racing SUM-380475 unit with a 27.5" x 18" two tube core which would mate nicely to a DeRale Dual Fan Shroud P/N 16837. My concern is whether or not the stock water pump is adequate for the additional pressure and flow demands of the crossflow configuration. I'm aware that the F150-F350 of the era were already using crossflow radiators and I'm surprised that they weren't original equipment on the vans. If anyone knows the different flow requirements between the two radiator types, I'd really appreciate their insight!

 

Then there's the double-pass crossflow, Frank.
Downflow vs Crossflow aluminum radiators

The crossflow became popular as hood height got lower. The most important issue is surface area, larger cools better. Triple rows cool better than double rows. The rate of flow through the radiator is important to allow enough time to lose heat to the air, too fast through the radiator makes the water hotter.

Basically, fit the largest size radiator possible and let the thermostat maintain the engine temperature.

 

the water pump will push the water through a crossflow rad no problem, assuming it is in okay condition and the impeller blades are not corroded too badly.

I was considering fitting an electric rad fan to replace the viscous fan on my 92 E350 van, but have decided not to now.
I removed the fan and drove it around without it for a short while. It certainly reduced the cabin noise, and probably picked up a couple of hp and may have helped mpg's a tiny bit.

Although the rad only needs the assistance of a a fan when the temperatures rise, I think the very cramped (and relatively hot) conditions in the engine bay of the E350 need the additonal airflow provided by a mechanical fan, which basically pump air all the time the engine is running, as opposed to an electric fan which will only circulate when the engine temperature rises, which in my case is not very often. This is just my opinion, and I have not performed any long term testing to back any of it up!

Your C class motorshome will have a different engine bay to the van, and airflow around the engine may not be such an issue. In which case an electric fan may be a good alternative.

 

Electric fans cool better than W?P fans in most cases.

 

I always thought/felt just the opposite - a big shrouded clutched fan would be best for cooling.

I guess if properly sized and fed power it should not matter. 4000 CFM is a lot.

 

Electric fans need shrouds too.
If you don't use a properly sized shroud, you lose a huge amount of cooling no matter which type of fan you use.

 

Just the reassurance I need! My original plan was to do a custom shroud and mount an array of 5 - 10 inch fans rated at 1080 cfm. Unfortunately, comparing the rated wattage of the fans with equivalent fan specs from Derale and Spal, the power consumed is not adequate for the rated airflow so I'm reluctant to take on the custom project. In that original plan, I was going to trigger three of the five fans with a PWM variable speed controller, while running the other two continuously to aid airflow in the van engine compartment to control the doghouse heating. Now I'm looking for dual pass crossflow radiators that will fit!

 

I looked at some specs for Spal fans too, was considering 2x 16" fans. You can buy 16" fans in the cheapy Chinese brands, but the motors are really lighweight and the cfm is rubbish too, not worth risking an engine over I like your idea of running multiple smaller fans and running 2 constantly, that sounds like a good idea.

 

Is the project mainly about cooling when the vehicle is sitting and running? At highway speeds, the radiator fan isn't working hard, the airflow from 60 MPH is enough. And don't forget about cooling for trans and engine oil. Derale makes add-on coolers for those. Auxiliary coolant radiators could be added to dump heat outside the doghouse. The rear heater on dual AC/Heater installations could be connected to a radiator underneath (protected) to dump coolant heat.
jim

 

Actually, the project was initially about switching to an electric fan. As I researched electric fan conversions, I found several posts about serious overheating of the doghouse during those periods when the fan (most of these were variants of the Continental Mark V111 fan) was not operating. The authors pointed to the contested van engine compartment. When I first purchased the van (Motorhome) I was really surprised at the heat generated and projected to the doghouse. At one point while doing some carburetor tuning, I was driving with the doghouse removed and the heat was just unbearable! However, as part of this unending project, I added a set of Hedman Elite headers with ceramic thermal coating and the open doghouse experiment was stunning - the heat level was just modestly uncomfortable!

The overall project has been to increase the fuel economy of this beast. I thought a modest efficiency enhancement was available with the electric fan conversion, but I primarily want reliability, so I was concerned about effective cooling reserve. The motorhome was already equipped with the camper cooling system package with a huge radiator, so I wanted to go to the most efficient cooling package available. I have never had a cooling problem, but was concerned about the 34 year old radiator. I have a 140 amp single wire alternator, so I should be able to support the 75 amp loads of a high power fan, and I'm considering going to the double pass crossflow radiator system.

 

Ah, got it.

The efficiency part depends on how much fuel it will take to turn the alternator while powering the fans vs using the OEM clutch fan. The electric fan design could be more efficient but there is some loss generating current and converting current to mechanical energy. I have no idea about any of that.

Interesting project!

 

parasitic loss is greater with a W/P driven fan

 

Please let us know how you get on with this aspect of the project? I have similar aims for my campervan. Have already fitted a set of Thorley ceramic coated headers, which should reduce pumping losses. Will crank in a little more ignition advance too. It appears that the MAF conversion gives good MPG gains in these engines too. Pity they are only 8:1 C/R, as I am sure a set of 9.5:1 pistons would help a lot, but that's a mission to remove the engine and fit these!

edit: just realised yours is an 82, so probably a carbed engine! C6 won't be helping either

 

Actually, in addition to the Hedman Elite headers, I have an Edelbrock 2166 dual plane manifold, a C6 with minimal slip towing torque converter, a Gear Venders overdrive, a custom cold air intake, recurved distributor, Melling MFC-3 RV camshaft rechecked to 2 degrees advanced, Crane Hi-6S ignition with variable retard, and a bypass fuel system with electric pumps and a Holley pressure regulator. The current major step is the conversion from the current Edelbrock 1411 (750 cfm) carb to an Edelbrock 1406 (600 cfm) that is being built by Competition Carburetion to the optimal specs of the 460. I'm installing a continuously monitoring Innovate MTX-L wideband AFR gauge for real time analysis. So far on my last nearly 8,000 cross-country tour with this beast, I averaged 10.2 mpg with a minimum of 8.4 and a max of 12.2. Over the road interstate speeds ranged from 60 to 65 mph. This is a 24ft. Born Free, weighing in at 11,000 pounds.

Today I measured the space between the radiator and the fan pulley to be 4.5 inches. This is very tight for the Derale 4,000 cfm fan package I was considering. So still considering the options.

 

What are the options for electrically driven water pump to replace the belt driven original?

If hot air in the doghouse is an issue, ducting clean air into the doghouse might help. Added drag from ducting could affect fuel mileage, however. I'm thinking of the fans that NASCAR uses to cool tires/brakes as an example.

At some point, fuel economy and a 24 foot motorhome are unsolvable.