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Topic: Engine Fan vs two electric fans (Read 990 times) previous topic - next topic

Engine Fan vs two electric fans

I'm sitting here reading posts about radiator fans (hydraulic) and had these thoughts.
Coaches with side radiators do NOT have fans on the engine--not practical or even possible.
The hydraulic fans (2) suck horsepower and reduce mileage.
Our coach is only 200 HP. It has a fan on the engine and two 13" diameter electric fans on the rear radiator.
The engine fan presumably sucks 30 HP (that figures out to 15%) which is a lot for a coach that isn't overpowered to start with.
The engine fan is still the old fiberglass fan and the radiator has apparently seen damage (repaired now) dead center to the fan.
Wolfe says leave the engine fan, but I kind of wonder. Is it possible that I could just remove the engine fan as an experiment? And monitor temps?
I have a quote for a nylon replacement and can do the work myself now that my shoulder is healed. $115 + shipping.
Would a nylon fan reduce horsepower drain?
Should I try without engine fan? We live up here in Wisconsin where we don't get the real high temps like down south or the taxing mountain driving that creates problems.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Engine Fan vs two electric fans

Reply #1 –
Not familier with your coach cooling system, so just general comments from this peanut gallery.

Engine cooling fan technology in automobiles is highly developed.  Why wasn't some of it applied to motorhomes?  A simple thermostatically controlled viscous fan clutch would eliminate much of the drag at low engine temps.  Hayden, for instance, markets fans and clutches designed for "trucker" duty.  Perhaps it would be possible to adapt one of them to your engine?

http://www.haydenauto.com/featured%20products-fan%20clutches%20and%20fan%20blades/content.aspx
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Engine Fan vs two electric fans

Reply #2 –
Without an engine fan you would need some really powerful electric fans. And I am doubtful they could keep it cool.
95 U300SE

Re: Engine Fan vs two electric fans

Reply #3 –
I tried the addition of an Heavy Duty Electric Truck Fan on my 1993, U225 just for additional cooling. I did not remove my mechanical engine fan. I could not see that the addition of the electric fan made any change in cooling the engine. I took it off. The only way I can see electric fans or fan would work is if a custom shroud was built to push or pull the air over the entire surface of the radiator. Without an effective shroud you would be bringing cool air only to an isolated area of the radiator.

I do think the thermostatically controlled fan clutch has some merit. I had a fiberglass fan on my U225 and it was very rigid so I doubt that a new fan will help much getting more horsepower. I couldn't find a Flex Fan big enough (CFM) to work on the coach.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Engine Fan vs two electric fans

Reply #4 –
Quote from: Kent Speers –
I couldn't find a Flex Fan big enough (CFM) to work on the coach.
I thought about suggesting flex fans.  I ran many Flex-A-Lite fans on my early hotrods with good results.  However, on a diesel engine I don't think the fan would ever turn fast enough to flatten out the blades, so any benefit would be minimal.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Engine Fan vs two electric fans

Reply #5 –
Quote from: Chuck & Jeannie –
I thought about suggesting flex fans.  I ran many Flex-A-Lite fans on my early hotrods with good results.  However, on a diesel engine I don't think the fan would ever turn fast enough to flatten out the blades, so any benefit would be minimal.


You are right. Your hyd fan can use up to 40 engine hp, now imagine the size of the motor on the electric fan, and of course the size of the alternator required  to run it.
Jim
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: Engine Fan vs two electric fans

Reply #6 –
Nitehawk,
I don't think your fan is consuming anywhere close to 30 hp.  I think that number is for engines with twice the horsepower and thus twice the cooling needs.  Secondly hydraulics are notorious for their very low efficiency.  I have a rear radiator too.  As an experiment I installed a toggle switch on the dash to manually turn ON my fan's pneumatic clutch.  I could not detect any power loss between ON and OFF.  The direct drive rear fan is the most efficient as far as turning a fan.  I think second would be an electric fan, but they lose efficiency at the alternator and then at the electric motor.  The hydraulic fans are the worst with all the heat that gets dumped into the fluid (although newer systems are getting better).  In fact, I wonder is some of the power steering gear failures are due to this hot fluid prematurely aging the seals? 

Rear radiators:  Poor airflow, poor engine access, excellent fan drive.
Side radiators: great air flow (fresh air, little obstruction), great engine access, poor fan drive.
I have seen an example of the best of both worlds:  2008 Prevost XL.  It had a large side radiator with a single huge fan.  The fan was a direct drive off the engine.  Belts off the vibration dampener drove a shaft that went into a right angle gear box that drove the fan.  There was a clutch in there too but I don't remember where in the fan drive.

I would not suggest running your coach without some kind of cooling fan - I don't thing you will get very far and when it is too hot to run it will take a long time to cool off on the side of the road.  The clutch system does an excellent job of providing the fan when you need it and turn it off when you don't.

BTW, not long after I purchased my coach (back in 2001) the Foretravel service manager suggest I replace my old fiberglass fan with a new plastic fan - I think it was very good advice as it probably saved me from lethal radiator damage. 
I don't think the plastic fans are anymore efficient - same basic shape.

John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Engine Fan vs two electric fans

Reply #7 –
A new Spartan k3 chassis has a mechanical drive fan side radiator setup.

Some kind of variable clutch in it as the salesman mentioned a hole to put a locking bolt into the slip feature locking it on
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Engine Fan vs two electric fans

Reply #8 –
Thanks, everybody, for all the great advice & information. I think I will keep an engine driven fan but change it from fiberglass to nylon. After all, the fiberglass fan is 27 years old but with only 80,000 miles on the coach. No clutch on the fan, tho, so it is direct drive and on whenever the engine is running.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Engine Fan vs two electric fans

Reply #9 –
Quote from: JohnFitz –
Nitehawk,
I don't think your fan is consuming anywhere close to 30 hp.  I think that number is for engines with twice the horsepower and thus twice the cooling needs.  Secondly hydraulics are notorious for their very low efficiency.  I have a rear radiator too.  As an experiment I installed a toggle switch on the dash to manually turn ON my fan's pneumatic clutch.  I could not detect any power loss between ON and OFF.  The direct drive rear fan is the most efficient as far as turning a fan.  I think second would be an electric fan, but they lose efficiency at the alternator and then at the electric motor.  The hydraulic fans are the worst with all the heat that gets dumped into the fluid (although newer systems are getting better).  In fact, I wonder is some of the power steering gear failures are due to this hot fluid prematurely aging the seals? 

Rear radiators:  Poor airflow, poor engine access, excellent fan drive.
Side radiators: great air flow (fresh air, little obstruction), great engine access, poor fan drive.
I have seen an example of the best of both worlds:  2008 Prevost XL.  It had a large side radiator with a single huge fan.  The fan was a direct drive off the engine.  Belts off the vibration dampener drove a shaft that went into a right angle gear box that drove the fan.  There was a clutch in there too but I don't remember where in the fan drive.

I would not suggest running your coach without some kind of cooling fan - I don't thing you will get very far and when it is too hot to run it will take a long time to cool off on the side of the road.  The clutch system does an excellent job of providing the fan when you need it and turn it off when you don't.

BTW, not long after I purchased my coach (back in 2001) the Foretravel service manager suggest I replace my old fiberglass fan with a new plastic fan - I think it was very good advice as it probably saved me from lethal radiator damage. 
I don't think the plastic fans are anymore efficient - same basic shape.




I think the 30-40 hp for the radiator fan is an old wives tale unless this is a test value at -40 deg. F. when air is really dense. I have run a dozen fans at different cfms and static pressures and with a 36" dia. Blades and they all max out around 5-7.5 hp at 70 deg F. But my fan simulator won't let me go any noiser than 120 dB. Might try to input -40 air during coffee break tomorrow. Earlier on i thought about putting a discharge damper controlled by engine temps at the rear of the radiator to limit mass flow, as mass flow along with the fan efficiency determine hp consumed. I thought wow if could spend $500 on a damper and actuator and gain big hp and fuel efficiency it would be worth it, but that doesn't look to be the case. I would bet the belts sizes would also back this theory up as the do not appear capable of transmitting that kind of hp, but I have not checked them yet.

Tried posting this last night but something happened.  Michelle pointed me in the right direction of where to find my draft.

Ran fan simulation this morning at -20 vs 70 inlet temp- used about 17% more power at the lower temperature.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Engine Fan vs two electric fans

Reply #10 –
What we can do to improve air flow through the radiator / intercooler is to seal EVERY air gap in the 'conveyer-belt' shroud.  The idea is to only allow fresh air outside the coach to be pulled through the radiators for maximum cooling.

When Foretravel built these coaches the shroud between the inside if the fiberglass fender and the edge of the radiator had many large gaps that allow the fans to recycle engine-side hot air back through the radiators.  We used common yellow hardening expanding spray foam to seal off the gaps that exist on all sides of the radiator.  We then painted the foam black.  We did have to add some drain holes in bottom for water that gets into radiator area.

No matter how the cooling fans are positioned, just be sure the shroud is intact and well sealed.

Re: Engine Fan vs two electric fans

Reply #11 –
I second Barry's comment and did the same but with new belting. I made templates so it all fitted together and when 2 pcs were needed due to awkward cutouts I used alum flashing to join them and screwed together.
It totally stops crap thrown up from Dually's which is the main problem with stuff getting between the CAC and rad, and gives a nice thru path for air drawn in.
JohnH
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Engine Fan vs two electric fans

Reply #12 –
Think Brett posted this a while ago, good info on what even a small engine [cat 300 hp] hyd fan can use.
This is why electric fans are not used very often in diesels.

http://prevostcommunity.com/PDF/Motor%20Home%20Fuel%20economy.pdf

Jim

 
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.