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914World.com _ 914World Garage _ What do ya know about this?
Posted by: JPB Mar 25 2006, 06:54 AM
Aircooledclassics has an electric horizontal fan set up for 914 engines. My question is has anyone ever seen one in use or used one? It looks like a good idea but wonder if it would be good for street applications since they imply for "racing". 1200 cfms is not much wind compared to stronger fans on the market that can even push 3500+CFMs. If it does save HP from the power plant, then its worth it and it will give the engine a stead air stream compared to the belt/fan deal which will only supply higher CFMs at higher REVs. ![popcorn[1].gif](http://www.914world.com/bbs2/html/emoticons/popcorn[1].gif)
Posted by: ! Mar 25 2006, 07:11 AM
I tried a dual electric fan set up once and it was less than adequate.
The DTM by Jake, the upright 911 fan or the current T4 that are belt driven tend to be the best bet.....too easy for a failure on the electric.
Posted by: rhodyguy Mar 25 2006, 09:23 AM
more continous current draw for our puny alternators to deal with. the idle falls off plenty on my car with the lights and everything else on, as it is.
k
Posted by: Jake Raby Mar 25 2006, 09:35 AM
Do searches...You will find a lot.
Email to ask them how much pressure the system creates in the upper plenums, I'd like to see if they have any data and if so if it matches what I measured when I tested the arrangement against the 914 DTM.
It's all about pressure and those axial fans make about 1/2 as much pressure as the stock cooling system does on it's most effective side of the engine (right side, 1-2 cylinders)
As for being efficient, taxing the alternator and etc that much more robbed 3 more HP from the engine than we saw with the same test without the arrangement in place, with the alternator only supporting the engine...
It's fine if ALL you do is Auto-X, load the engine up in a stock 914 and see what happens in 5th gear. I have data.
Posted by: JPB Mar 25 2006, 07:29 PM
I guess what you are saying is if you need air cooling from the belt or the alternator, its all costs HP's from the engine right and its better and safer from the original setup 
?
Posted by: rhodyguy Mar 26 2006, 08:53 AM
and money better spent on other items.
k
Posted by: brant Mar 26 2006, 10:26 AM
I've seen plenty of them..
used on -4s and on -6s..
strictly a racing item.
NOT a street fan
brant
Posted by: JPB Mar 26 2006, 08:07 PM
Cool and informative. It sounded so good at the time and yes an oil cooler would do the trick instead of modifying something like that. THNX. 
Posted by: jd74914 Mar 26 2006, 08:12 PM
Of course, if you are into the horizontal thing you could always go with a http://www.tangerineracing.com/engine.htm . 
Posted by: ! Mar 26 2006, 08:14 PM
Yeah that 90 degree bend worked wonders for the Corvair....
Posted by: alpha434 Mar 26 2006, 09:36 PM
| QUOTE (Jake Raby @ Mar 25 2006, 07:35 AM) |
| As for being efficient, taxing the alternator and etc that much more robbed 3 more HP from the engine than we saw with the same test without the arrangement in place, with the alternator only supporting the engine... |
Be specific. According to my data, the #1 HP robber is the fan. Not the alternator. So are you saying that you have a net loss of 3 HP with an electric system as opposed to the stock setup, or to no fan at all?
Posted by: lapuwali Mar 26 2006, 10:38 PM
The power loss from the alternator scales with the amount of demand on power from the alternator. The stock alternator can put out 55A at peak, but usually only puts out 10A or less. Given typical efficiency of 50%, that means the normal power loss from the alternator is 1/3hp, but the loss at a peak load is over 2hp. Two 1500cfm electric fans would draw about 40A, or 560W, doubled to 1.1kW loss at the crank, or about 1.5hp, just driving the fans. That assumes the alternator really is 50% efficient (a common rule of thumb, but only that). If it's only 25% efficient, that's 3hp (and that also means the normal alternator loss is closer to 2/3hp).
The belt drive to the alternator also causes some conversion losses, though that's usually only 2-3%.
Given that centrifugal fans are more efficient than axial flow fans, and that the fan is direct drive on the Type 4, it's very likely to be much more efficient than this.
Posted by: alpha434 Mar 26 2006, 10:45 PM
I already knew all the stuff in regards to calculating alternator hp loss. Or sometihing close to what you said. The fan has to push a lot of air into a high pressure system and maintain that pressure system. There is a huge loss with the fan. Much greater than with the alternator at full draw. You would be surprised.
The advantage of a belt drive system is being able to set a ratio for the pulleys specific to the amout of air you need, the amount of air you can provide before starving the fan, and your average RPM range.
And then you loosen the belt to give you that extra oomph.
Posted by: lapuwali Mar 27 2006, 01:19 AM
Energy in = energy out - unavoidable thermal losses. Plain, simple thermodynamics.
If pushing a fixed amount of air, then you have to expend a fixed amount of energy to push it.
If you use a system with a fan that's attached directly to the crank, or you use a system that has to drive an alternator through a v-belt (small power loss), then the alternator has to convert this to electricity (big power loss), then you have to convert the electricity back to mechanical energy with a motor (another big power loss), which one is going to end up drawing more power from the engine to deliver that fixed amount of energy?
Posted by: alpha434 Mar 27 2006, 01:26 AM
| QUOTE (lapuwali @ Mar 26 2006, 11:19 PM) |
| Energy in = energy out - unavoidable thermal losses. Plain, simple thermodynamics. If pushing a fixed amount of air, then you have to expend a fixed amount of energy to push it. If you use a system with a fan that's attached directly to the crank, or you use a system that has to drive an alternator through a v-belt (small power loss), then the alternator has to convert this to electricity (big power loss), then you have to convert the electricity back to mechanical energy with a motor (another big power loss), which one is going to end up drawing more power from the engine to deliver that fixed amount of energy? |
But with an electrical fan, you have constant output at all rpms. Unless you want to change that. The advantage would be at high revs, where the attached fan has the most power loss, and is borderline starving all the time. With a properly setup electrical fan, the hp cost would be constant, since the fan will always need the same amount of energy to turn the same speed.
Posted by: dstar Mar 27 2006, 07:54 AM
I own an ACC electric fan and made the mistake of trying to breakin
an engine with it.
Head temps went to 400 in less than 5 minutes of run time....with 55 degree ambient air.......
Had to switch everything back over to stock cooling to run the engine in.
Strickly a race only fan, unless you have ducted/forced air.......then pray
you don't get caught in *traffic*!
Don
Posted by: rhodyguy Mar 27 2006, 09:04 AM
looks like the only way to find out is for you to buy and install one chris. strap the car to a dyno, give it a run or 2, switch back to stock, 2 more runs, and report with your readings.
k
Posted by: brant Mar 27 2006, 09:28 AM
I would like to add that when these electric fans are used in RACING applications...
The reason for doing so is entirely about the HP.
and they are used with a 2nd battery at a 100% loss
so there is no question in that application that the acceleration HP is benefited.
brant
Posted by: lapuwali Mar 27 2006, 10:09 AM
| QUOTE (alpha434 @ Mar 26 2006, 11:26 PM) | ||
But with an electrical fan, you have constant output at all rpms. Unless you want to change that. The advantage would be at high revs, where the attached fan has the most power loss, and is borderline starving all the time. With a properly setup electrical fan, the hp cost would be constant, since the fan will always need the same amount of energy to turn the same speed. |
High RPM also generates more friction, so requires more cooling, so more airflow is needed, so the fan has to be spun faster.
As Brant says, if you run the car and an electric fan off batteries in total-loss mode, as is commonly done when racing, then you'll see a significant benefit, as you get to recover both the fan and alternator losses. This beneift only lasts as long as the battery does, and that's likely to be little more than an hour per charge. Perfectly fine for many racing uses, pretty useless on the street.
One *could* devise a setup where the alternator is clutched out of the system at WOT, and just run off the battery (or batteries) during full throttle. This may even work on the street.
Posted by: dstar Mar 27 2006, 10:22 AM
@ 7000 RPM, the stock 914 cooling setup is using around 10-12 hp.
Cooling is NOT where you want to find HP!
But if you guys got enuff cabbage to piss away, have at it!
Stupidity usually ends up costing someone, something, in the end......
Again, this setup wasn't even usable for AXing, in a wide open 356......
with head temps in the 450 range.........
Don
Posted by: brant Mar 27 2006, 10:28 AM
Don,
I know 12 or so race cars running a modified version (something similar)
I only point this out to say it can be done with enough testing and tweeking...
luckily we have Jake here to sell finished products of cooling alternatives that are safe and tested...
It can be done.
should not be attempted for a street car
brant
Posted by: dstar Mar 27 2006, 10:32 AM
I agree, it can be done! I had the type 4 bottom tins on and I
think that had a lot to do with it.......
I have been thinking of using it in the Bradley GT, since I have
access to LOTS of forced air with that body......I just don't have
the time.
Anyone want this setup, with 75 amp alt for $450 + shipping?
30 minutes total run time only!
Don
Posted by: alpha434 Mar 27 2006, 11:28 AM
| QUOTE (dstar @ Mar 27 2006, 08:22 AM) |
| Again, this setup wasn't even usable for AXing, in a wide open 356...... with head temps in the 450 range......... Don |
We've ducted a 356 run no fan specifically for track use.
You have a Bradley GT?
Posted by: dstar Mar 27 2006, 11:34 AM
Yes.
Don
Posted by: lapuwali Mar 27 2006, 12:10 PM
| QUOTE (dstar @ Mar 27 2006, 08:22 AM) |
| @ 7000 RPM, the stock 914 cooling setup is using around 10-12 hp. |
10-12 hp seems extraordinarily high. Can you cite any references for this number? I suppose its possible, given how the stock Type 4 fan is supposed to reach peak efficiency around 4500rpm, and only gets less so above that. Aero loads also rise with the square of the speed, so...
Seems like this is one place where running a DTM setup would provide big gains, since you could underdrive the fan to operate more efficiently at these kinds of speeds, rather than being optimized for street cruising speeds. This should also cut the power losses at these speeds.
Posted by: r_towle Mar 27 2006, 04:42 PM
I have been thinking.
Uh oh.
Would there be any benefit of polishing the inside of the aluminum fan shrouding...
Would air flow be increased enough to justify doing this.
I am gonna sand blast it to get it clean anyways, I will use black beauty, so I wont be deforming the aluminum, just wondering if its worth the time (I am sure it would be alot of time) to polish the inside of this.
Rich
Posted by: Aaron Cox Mar 27 2006, 04:54 PM
what about cutting off and welding up and smoothing the 2 heater air outputs off the fan shroud?>
Posted by: r_towle Mar 27 2006, 05:11 PM
| QUOTE (Aaron Cox @ Mar 27 2006, 05:54 PM) |
| what about cutting off and welding up and smoothing the 2 heater air outputs off the fan shroud?> |
cause its to f-in cold for that...
read and apply your siggy.
I saw that last night...to funny.
Rich
Posted by: jhadler Mar 27 2006, 06:16 PM
I don't think poloshing the inside fo the shroud is gonne net you anything. Sealing up the heater ports? I suppose that might help, but I'd try to stay away from welding.... That's not aluminum you're talking about, it's magnesium. An it don' take too kindly to bein' welded on... If you know what I mean...
I haven't tried the electric fan myself. But I think it would be pretty good for a race only car. A street car would be a different story.
-Josh2
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