KJL

Just curious....

emsrescu

7 - 12 hp? thats what they say.

e3pres

:yesnod: ~10

bigvette1

You need to measure the cost of a electric fan conversion vs the 7-10 HP gain. You can gain that and more in many areas for a lot less. However, if you cooling is margional now then the conversion is worth it.

Weird Science

Another consideration is looks. I love the way electric fans clean up the looks of the engine compartment and would do it for that reason alone.

aharte

About how much does the mech fan weigh, and how big is it? When does the clutch lock and unlock? I could give an estimate based on these things. I bought my vette with an electric fan already installed, so I don't know what the originals are like.

Glutamine83

is it a big process to remove the clutch fan???
never done it before

75 Stingray!

Advantages of an electric fan:
-Free up HP
-Easier to replace belts without the fan in the way
-Flows same amount regardless of RPM
-Less weight
-Better for a higher RPM engine
-Looks better
Only 4 bolts

shotgun_000

Maybe I'm wrong about this, but do you really gain hp? You don't get something for nothing, the alternator still has to power the fans. Whatever the alternator puts out in terms of amperage is at the cost of inreased drag on the alternator. So, the hp gained by not driving the fan via belt is just transferred to the belt driving the alternator.

The only way I could see a gain is during the time the electric fans switch off, compared to the clutch fan that is always turning.

However, if there is a small hp gain, then it's likely due to the fact that the electrics are a bit more efficient. Tradeoff? They may not cool as well as a conventional fan, and the engine may run warmer.

Just my opinion.


[Modified by shotgun_000, 5:51 PM 7/28/2003]

aharte

You're right that the energy has to come from somewhere. All things equal, a mechanical fan would actually be much more efficient. Its easier to use mechanical power directly than to go mech->electrical->mech again. Electric fans are used more efficiently though.

The fan blades take energy to push the air though them, but they also take energy to spin up. An electric fan gets up to speed within a second or two, and then draws a constant current. A mechanical fan has to be accelerated every time the engine speed goes up. I think the fan clutch is a 1:1 coupling. If so, its the same type of drag on the engine as a larger flywheel. It takes a certain amount of power to run at whatever speed, but the rotational inertia adds an effective mass to the entire car on top of that. Its gear dependent, but I think its generally around 100 lb in 1st gear (+/- factors of 2 or 3 depending on a lot of stuff). So 100 lb/3500 lb car=3%. Assume a 300 hp engine, and you have the typical 10 hp people talk about. That last part isn't really correct, but I think that's how the numbers people quote were made up.

RJR99SS

a mechanical fan still cools better than an electric one. Thats why most new rwd cars still use mechanical fans. Although the new plastic mechanical fans seem to be the best of both worlds, as they're quite light and still cool the same as metal one.

Jvette73

I use both. I remove the mechanical fan when I go to the track but run both on the street. While the electrical fans dont always pull as much air, they do, when installed correctly, pull every bit of it thru the rad fins. The electrical fans are better at cooling during idling and slower vehicle speeds. When running at higher speeds the mechanical fans definatly pull alot of air but not all of it is being drawn directly thru the rad fins. The mechanical fans also do a better job of blowing the underhood heat out thru the gills and out underneath the car.


[Modified by Jvette73, 7:10 PM 7/28/2003]

aharte

My electric fan is really really strong. No mechanical fan I've seen in other cars comes close. I was playing with it once, and found it could cool the engine from 210 degrees down to the 180 thermostat setting in 5-10 seconds (its normally off with a thermally activated relay to turn it on occasionally). Unfortunately, I don't know where it was bought/what model it is. It also has a shroud, which I think is unusual for an electric fan.

Jvette73, at high speed, the fan is useless. More than enough air is forced through the radiator just from the speed of the car. Fans are only needed for traffic or very low speed driving.

427Hotrod

A lot depends on what mechanical fan you have. A good clutch fan is pretty efficient. Or a good stainless flex fan.

I can give you a worse case scenario. I run a 7 blade fixed stainless steel belt driven fan on my 540" '67. I've had that fan for 20+ years. It's a little noisy, but it cools great.

I removed it during some chassis dyno testing once to see what it consumed. It was less than 5 RWHP even turning over 7000 rpm. I was considering an electric if it really ate lots of power, but decided against it after the tests. I have also removed it at the track and it made no difference I could note on a timeslip in ET or MPH. Just not enough of a drag.


JIM

QuickVet

I never really noticed a difference in HP. But I feel much better knowing I have electric fans. They look great too. Next is an electric water pump.

Jvette73

Jvette73, at high speed, the fan is useless. More than enough air is forced through the radiator just from the speed of the car. Fans are only needed for traffic or very low speed driving.[/QUOTE]

thanks for clarifying that. What i really meant to state was the mechanical fan moving faster at the higher vehicle speeds helps move more hot air from under the hood compartment.

LAvetteman

I disagree, for the simple fact that an electric fan runs at full speed as long as its on. They can be cycled off when not needed, thats better than a clutch. I can't think of any new vehicle that uses mechanical fan, except trucks. And to answer the question about an elec fan taking away HP as much as much as mechanical, if an elec fan ends up using the same amount of total HP it is spread out uniformly through the duration of the engine running. In other words for example, if a mech fan uses 7-15 HP epecially on acceleration than a elec fan will use around 5 HP throughout the entire duration while the engine is running.

Now I am a little confused on efficiency, the only bad thing I can see about elec fan is you have an energy loss through the heat generated by the fan motor and the extra heat the alternator may produce with the load of the fan. You dont have a heat loss with a mechanical fan unless the belt is slipping.

But dont trains use elec motors driven by deisel generators for propulsion??

Maybe a mechanical or electrical engineer can shed some light on this subject.

Cookwithvette

Yes. Many ships too. They use HUGE two stroke supercharged diesels to turn some hefty generators. Thing is, even supercharged, two stroke diesels run slowly. We're talking ~800 rpm. This would make for either an extremely long train ride or one extremely complex gearbox setup. Electric motors have one thing fuel driven motors will never have... a FLAT torque curve. They can produce full torque at 0 RPMs. (An extremely useful characteristic when trying to move a several thousand ton train.) Usually all wheels on a locomotive are driven. Instead of a complex drivetrain you use a relatively simple power regulation scheme. Combine that with traction control technologies and you can ensure you get the most tractive (sp?) force from each wheel without slipping.

Ships use this setup for the speed issue too. Also, should a ship's propeller suddenly snag on something, large rock, iceburg (in icebreakers), etc.. a directly driven system can be severely damaged but rarely hurts an electric motor.

In both situations you get the added benefit of plentiful electric power for the rest of the ship/train for lights and other... um.. stuff.

The biggest benefit of an electic fan is its constant speed. Even at idle you get airflow equivilant to ~35-45 mph cruising. The issue of efficiency is addressed with design. Look at the blades of an electric fan and look at the mechanical fans in our cars. Don't look anything alike do they? Mechanical fans need to be able to pull a lot of air at low speeds, otherwise our cars would overheat at idle. With that in mind devices (clutches) need to be implemented to reduce its impact on the engine at cruising speeds. If a mechanical fan could be set up to run fast at idle and completely disconnect when the engine reaches say 2000 RPMs you would have a perfect mechanical setup. While moving, any operating fan becomes an obstruction at a certain point. Electric fans need only be designed to be efficient at one speed.

One horsepower is 746 Watts. Lets take the dual Spals, they take a 25 amp fuse right?
Volts * Amps = Watts
So
13.5V * 25A= 337.5W

So essentially the electric fans take 1/2 horsepower. That's wether your at 800 RPMs or 7000. Of course you'd have to throw in the fact that most alternators are overdriven and there are generating and system resistance losses but I can't really see the whole setup taking more than 1 horsepower.

That in mind I can't really see a mechanical setup taking much more than 2-3 horsepower even at high RPMs without a clutch.

Bottom line... if you're looking for horsepower, there ARE better ways. If you're looking to squeeze every drop of performance out of a setup then go electric.

One added note, if you're drag racing you can put a switch in the cockpit to turn the fans off just before you stage. That way, as you race you have NO load on the engine from fans. But again that's only if you're looking for every ouce of performance.

One note about what I've just written; everything I know about electronics I've taught myself. I believe I have a good understanding of it but I'm not an engineer. If you see somthing you know to be wrong please tell me. :cheers:

[Edited for spelling.]


[Modified by Cookwithvette, 12:00 AM 7/29/2003]

KJL

I have already done the intake, cam and heads and now just want to glean what ever hp/torque I can. This includes electric fan, HEI distributor, under-drive pully set and 1" carb spacer. BeCool has a dual fan which moves about 2800 cfm. The cost is 280.00 But they are offering a 10.00 rebate and Summit is running a 10% off deal through the end of July. My ultimate plan is to swap all my new top end stuff on to a 403 or 383 stroked short block and then rebuild the original numbers maching engine. :crazy:

Stewart's74

A bunch of forum members run Permacool fans. http://www.perma-cool.com/Catalog/Cat_page16.html

16 inch....lots of cfm's