Interesting Test on Engine Fans

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Jims65cyclone
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Re: Interesting Test on Engine Fans

Post by Jims65cyclone »

Groover wrote:Can we assume that the HP gained/or lost is proportional to the engine displacement/HP?

That is to say that while this costs or saves 30 hp on a 350 chevy, it would cost or save proportionally less on a 260 SBF.

?
I would think it wouldn't matter what size engine you had a given set-up bolted up to. It would take the same amount of hp to drive that fan/shroud/rad combo at a given rpm. The engine is just the device that turns the fan. The amount of power it takes to turn it is a function of how many cfm the fan is trying to move through a given resistance to the airflow. That's why the amount of hp required dropped without a shroud. The fan is able to move air from all around it, which reduces the resistance the fan has to overcome if all/most of the air it draws has to be pulled through all the fins on a rad. I would expect a shrouded fan pulling through a 4-row rad to rob more hp than the same fan with a 3-row rad. More resistance to the cfm it's trying to move. I would also expect a fan fully within a shroud to draw more hp than one half in/half out. It can't cheat by pulling part of its cfm from unrestricted air from outside the shroud. Now cooling efficiency is just the opposite. The more air a fan can (has to) pull through the rad, the better the cooling. But that cooling efficiency comes at the cost of hp. The trick is to find the sweet spot where you pull just enough air through the rad in an efficient manner to cool the engine to the target temp. A 4-row rad with a loose fitting, or no shroud and a 16" fan might get the engine temp where you want it. But, maybe the best combo is a fully shrouded 3-row fan with a fully inserted 10" fan. The tight shroud ensures that nearly all of the fan's cfm moves through the rad so none is wasted by pulling air from behind the rad, and the smaller fan required to accomplish that takes less hp to drive. Win-win. Of course the amount of testing required to find that sweet spot, and factor in the effect of additional forced airflow through the rad as the car speed increases, would be mind-boggling. :roll:
Jim
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Comechero65
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Re: Interesting Test on Engine Fans

Post by Comechero65 »

I've read several people say a 4 row, which is what I run, has more restriction to airflow and they may be right, it does make some sense. It would take some tedious testing to find the best combo that cools properly at a minimum of hp loss. I have always run a 4 core rad with a 5 blade fixed fan and never had an overheating problem. But i don't know what the cost is in terms of hp loss.

When they measured a lesser hp with no shroud I think the fan is like a pump when it cavitates, it's mostly just spinning in the air and not taking as much hp to keep spinning.

Might be interesting to try several different fans and some different locations of depths into the shroud. If there were enough room it might be interesting to try a clutch fan just to see how well it would work. I would think it would cool just fine just don't know how much hp it took when hot. wish they had got it hot when they tested that one. We may never know.
Too old and tired to expend that much effort to find out. Even though I wonder may just leave things alone.
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redhotcomet
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Re: Interesting Test on Engine Fans

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The thicker the rad, the more work the fan has to do to pull air through it. Electric fans work well because they only require power when the coolant is hot enough to turn them on. They don't turn at highway speed - when there is adequate air flow through the rad from forward motion. Similar to a clutch fan. Except a clutch fan doesn't always pull air through the rad...but it is always attached to the engine. Everything is a tradeoff.
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comethead
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Re: Interesting Test on Engine Fans

Post by comethead »

On my track Falcon 302 I'm using this nylon fan https://m.summitracing.com/parts/flx-41 ... hYQAvD_BwE
But that little engine will spend most its time above 6k rpm.

Joe
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lavron
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Re: Interesting Test on Engine Fans

Post by lavron »

Ok so the question is (or one of them) would there be an advantage to modify the core support a little to hold a wider thinner radiator?

Just a thought on using a later model that has electric fans(s) already fit to it and making the opening wider, maybe welding in the center part of a core support from say a later model Mustang or something that would fit correctly?

Just thoughts to ponder :roll:

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Mike
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poboyjo65
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Re: Interesting Test on Engine Fans

Post by poboyjo65 »

Mike some guys notch the frames so the rad can come on out to the aprons. Yes a thinner rad would help. & before you think outside the box, there is barely enough room for a 1'' thick condenser before the brace for the hood latch gets in the way,which also bolts to the rock guard on its way down to the frame.so some extreme re-engineering would be needed to remove that brace. Is that 250 6 any longer than a 200? maybe a mock up is in order while your block is empty & light?
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Re: Interesting Test on Engine Fans

Post by lavron »

poboyjo65 wrote:before you think outside the box
There's a box? :lol: :lol:
poboyjo65 wrote: Is that 250 6 any longer than a 200?
The engine itself is no longer but the water pump is, so there is a loss of about 1". I am going to try and push the motor back maybe a 1/2" and gain some, but you are right it all needs mocked up.

One thing is I am going to change the core support in my car which I already have (in parts car) somethings I won't know until I get the Mll installed as far as how low I can set the motor down, I might be able to use the parts car to mock stuff up because my car is still all together.

I said a late model Mustang earlier and so I checked to see the size and it is no shorter than stock one and it is wider than the frame rails so you would have to pocket the rails to get it to even fit, that was off the top of my head but I am sure there are better choices if someone really wanted to do something like that.

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Mike
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Groover
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Re: Interesting Test on Engine Fans

Post by Groover »

So if I put an electric fan in my Comet, I'd pick up approximately 30 hp which is a gain of almost 20% on my stock 260 with 164 HP.

??
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Re: Interesting Test on Engine Fans

Post by lavron »

Groover wrote:So if I put an electric fan in my Comet, I'd pick up approximately 30 hp which is a gain of almost 20% on my stock 260 with 164 HP.

??
There probably is a reason that about all new cars have electric fans. Now I need to figure out which one will donate a good fit to my car, if it could be around '98 that would be best because half my drivetrain is from '98 :roll: :P

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Comechero65
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Re: Interesting Test on Engine Fans

Post by Comechero65 »

A possible electric fan source, my daughter-in-law had a Jetta that had dual fans driven by one motor that was narrower than some others so may be a candidate. May need a slightly wider rad but I thought it was a nice fairly compact design design and since the motor is on one side no interference with the water pump. The motor had one fan mounted to it and had a belt driving the other fan.Can't find the dimentions I thought I had.
Looked for one on epay but could not find even one.
Ron
Last edited by Comechero65 on Sat Aug 19, 2017 5:26 am, edited 1 time in total.
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Re: Interesting Test on Engine Fans

Post by Lou's Comet »

poboyjo65 wrote:I wish they would have did a run with the clutch fan hot. who cares what it does cold :roll: I'd guess its' numbers would be more closer to the others if it was hot. I wrote down the HP numbers;

no fan 349
cold clutch- 335
lo profile alum- 328
plastic- 325
steel- 318

steel/no shroud was 326. it made 8 more HP without the shroud. which make sense, it forces the fan to pull air thru the more constricted radiator. Makes me glad I made my shroud quick & easy to remove, if I ever go to the strip I'll take it off! :D ........

..........................
I would just leave the shroud on. It's a cool shroud!

Cool test, neat to see the differences in the types of fans. Always planned on a clutch fan for mine, and test confirms what I already felt.

The numbers are deceiving, obviously they are accurate for what they did, but are not accurate for a car your driving.

When your driving you ever stick your hand out the window go 35-40 mph? Good bit of wind. Stick hand out at 60-65 mph, a lot of wind.

Now that wind is being pushed (becoming airflow) through your rad so the fan isn't working nearly as hard to pull it thru, compared to the car/engine sitting still as in the test. If fan isn't working as hard then it is not using as much hp.

Now if sitting still in traffic if you rev your car to whatever rpm peak hp is your going to lose hp similar to the test. Really can't use the hp anyways, ya sitting still. But driving down the road at speed the loss numbers are going to be a good bit less with the airflow from the speed of the vehicle. I would think more on the lines of what pops said at 12 or so.

The clutch fan being tested hot would also give you loss numbers more typical with a car in stop and go traffic, running down the road with airflow the clutch shouldn't really be hot.

Drag car...electric fan is the way to go. Street car I will stick with a mechanical.

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Re: Interesting Test on Engine Fans

Post by Lou's Comet »

lavron wrote:
Groover wrote:So if I put an electric fan in my Comet, I'd pick up approximately 30 hp which is a gain of almost 20% on my stock 260 with 164 HP.

??
There probably is a reason that about all new cars have electric fans. Now I need to figure out which one will donate a good fit to my car, if it could be around '98 that would be best because half my drivetrain is from '98 :roll: :P

See Ya,
Mike
The reason many new cars have electric fans is because the engines are sideways.

If ya go with electric do as John said and make sure they produce enough cfm. Seen many people switch to electric and have problems.

Lou

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Re: Interesting Test on Engine Fans

Post by Comechero65 »

When I had the motorhome with the 454 while running on level road at speed the fan clutch would still engage and cut on and off occasionally but not often. If I hit a grade and the engine was working harder it would go on and off more often but would still shut off indicating it was doing its' job.

As has already been said the clutch fan is less likely to engage when running at highway speeds then sitting in slow traffic. But it's a tight fit on our cars to get a clutch fan in there so not an easy task.
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Re: Interesting Test on Engine Fans

Post by lavron »

I do have a do have an old radiator out of my '90 Cherokee (maybe, if I didn't haul it to the scrap yard) it is really short, wide and thin. Of course there is the whole thing that all I ever had was one cooling problem after another on that Jeep but the engines are a similar size. I will have to look on the Jeep but I think it has one electric fan and one little belt driven fan (plastic) but I could be thinking of something else.

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Re: Interesting Test on Engine Fans

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lavron wrote:Ok so the question is (or one of them) would there be an advantage to modify the core support a little to hold a wider thinner radiator?

See Ya,
Mike
Yes. If you don't have a problem with modifying your core support you could go with a wider thinner rad.
Enlarging the opening wouldn't be that hard.

Also where the Comet rad mounts to the support it is farther back (raised?) than the rest of the rad support. So just removing the raised mount sections on the support would move the rad forward some.

Going with something like the rad in this link may be the ticket.

**warning** link is for a rad in a non Ford conversion. http://jagsthatrun.com/Pages/Parts_S10-V8-Radiator.html

The rad in the link has a core only 1.25" thick! Think it would be hard to find a thinner one.

A stock Comet rad has a core of about 16"x17" which is around 272 sq inches of frontal area. The one in link is about 24"x15" which would give you around 360 sq inches of frontal area. This is over a 30% increase in frontal area. Which in my opinion is big improvement. Also it being a single row rad the airflow thru it will be increased.

On my Comet I have 30" from inside of apron to inside of apron right above the frame rails. You would not have to notch the rails. You would have to make the opening about 8" wider, 4" a side? Which would remove the raised/moved back sections of support and let the rad move forward even more. May have to make a block off on the bottom since rad core isn't as tall. This would not affect anything in front of the support.

Not sure if it would affect any of the holes to mount grille or gravel guard but can check today. Thinking horns would need to be moved which isn't a big deal.

IMHO this rad would fit with minor modifications, just need to enlarge the opening fab a few mounts. The only problem you may have is where the inlet and returns are on the rad. Don't recall what they are on the Comets.

The aftermarket rad is a V8 rad designed off a vehicle that has a very small airflow opening in front. With the bigger Comet grille I would think it would get even more airflow.

Also at $130 for a new rad really don't think it is a bad price. If you take the year,make,model of the car the aftermarket rad is designed off of and do a search you can find them for under a $100.



Lou

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