minocqa

hi
if i remove the air pump do i need remove the fan thats stock and then install a electric fan?
thanks
Don

Alex-7

You can either get a shorter belt or an electric fan. The choice is yours

BMS2004

<looks at location> you don't ever race at blackhawk by chance do ya? and yea alex is right, I would opt for the electric fan though if ya can.

1stgen_tn

Electric fan is a good upgrade (IMO) but you will need a shorter belt either way you go.

Without the air pump belt, the alternator belt will slip at high rpms. I imagine it might slip on the water pump as well. Definitely get a short belt to run from crankshaft to water pump. (or) buy a dual belt alternator pulley and just run (2) alternator belts.

search for "rat's nest removal" if you haven't yet. This will explain more on removing the air pump, etc.

MosesX605

I wouldn't bother with the e-fan. Aaron Cake made a good point in the Canuck forum a while back. The alternator has to generate power for the e-fan, which will make it commensurately harder to turn. Any way you cut it, fans are a parasitic loss. The way I see it, if you're converting the rotational energy from the engine to electrical and then BACK to rotational to power an e-fan, any benefit has long since evaporated. A stock fan that has a properly operating clutch should be a minimal drag on the engine.

If your fan clutch is shot and you don't want to shell out for a new one, then by all means, get an electric fan. Otherwise I'd stick with the stocker. Another thing to consider is that the stock alternator on the 1st gen is underpowered from the factory, let alone with the added draw of an e-fan and aftermarket stereo, etc.

1stgen_tn

true. It would be wise to upgrade to a 2nd gen alternator if you are going with an electric fan. That is on my "to do list"

However, the e-fan will not be running all the time if powered by a thermostat. The way I have mine set, I think it's only on when I stop at redlights or during alot of city traffic. (this is with the water temp at "normal operating temp" which is like 1/4 on the temp gauge.

Since I drive mostly open roads, I don't think it's a real issue for me. You CAN tell by the voltage meter when the fan kicks on though-no doubt about it.

REVHED

You're forgetting one important detail... if you use a thermo switch (as you should) the fan will not be running most of the time! So yes there is a definate benifit to using an electric fan.

Supper

And then there are those of us without any stereo at all in any of their 7's.

MosesX605

That's true I suppose. That being said, the stock clutch fan should partially disengage at speed as well. Mine only runs noticably at idle or at very low speeds. The whole efan thing seems to be of marginal benefit at best.

Of course, I'm not really one to talk about making modifications with marginal gains. I've got a DLIDFIS system and I modified my air cleaner based upon Carls tutorial for insulated cold air intake.

To each their own.

Yeah, I'm basically in the same camp as you, but even without a stereo, our alternators are pretty wimpy.

DAVID GRIMES

The alternator doesn't increase its "parisitic"ness with the addition of a fan. It can either handle it or not. The efan by itself will not cause you problems unless you've loaded up your alternator with accessories.

Yes, go with the alternator upgrade if you are introducing stereo amps and such. And get rid of your stock fan if you want a few horses on the cheap.

Hell, I thought our cars were pretty much air cooled in Canuckland at least nine months out of the year.

djmtsu

iTrader: (3)

I'm with Grimes. I can't see how more juice being drawn from the alternator is going to make it "drag" more than normal. That's not how it works. The regulator dispenses the juice as needed (hence REGULATOR). Its not like the commutator in the alt magically produces a greater magnetic field and thus "drags" more when the output rises. Or maybe I just need another beer.

MosesX605

I was under the impression that the alternator would be harder to turn the more power it was putting out.

gsl-se addict

iTrader: (3)

Actually, Moses is correct. The more load placed on the car's electrical system, the more work that needs to be done by the alternator to keep up with the demand (until the maximum output of the alt is reached). This means that the alternator gets harder to turn when the load is increased. Think of it this way: If the alternator always put out the same work (current), but not all of it was needed, where does the energy go? Energy has to go somewhere; it cannot be created nor destroyed.

Basically, the regulator varies the amount of current that is allowed to flow back through the field coils (by sensing the output voltage), which in turn alters the magnetic field. Alternators do not use permanent magnets like generators and electric motors. The magnetic field is created by passing a current though a coil. The strength of the field is proportional to the amount of current flowing though the coil.

Here is an article that explains how the alternator works:
http://www.vtr.org/maintain/alternator-overview.html

Based upon this, a clutch fan would seem more efficient. Some state that the electric fans don't run most of the time, so this makes them better. However, the later (after '84 I think) clutch fans had a thermostat in them to where they basically freewheel under cooler conditions, like during cruising. I am not sure which is really better. You are not going to gain or loose much power between either setup (unless your clutch fan is bad). I think it is just a matter of preference. The electric fan clears up some space in the engine bay, but also adds failure points to the cooling system. The electric fan also adds to the electric load of the system (some draw over 30A continuous), so if you install one, definitely consider an alternator upgrade.

Just my $0.02. Hope this clears some things up.

Kent

DAVID GRIMES

I'll bet you a shift **** or fuzzy dice ( your choice ) that the "drag" from an alternator ( the variable electromagnetic field that develops across the fixed GAP between the rotor and stator ) is MUCH LESS than the "drag" from a mechanical clutch fan pulling hundreds of CFM's of air with plastic paddles.

You are right that energy can neither be created nor destroyed. But it can be wasted from inefficient conversion.

gsl-se addict

iTrader: (3)

Yeah, it is hard to say which is better of hand. For instance the alternator (assuming 80 A, 14v output with an efficiency of say 80%) would take a maximum of 80x14/0.80 = 1400 W (less than 2 HP). The first gen alts are about 55 amps, so there maximum parasitic draw is even less. However, as I said before, these electrical systems are not designed to take the additional load of an e-fan, so I would recommend a 2nd gen alt as an upgrade. They are real easy to install and will get you to 70-80 amp capacity.

You have to also understand that the load on the mechanical fan decreases when the car is moving. The incoming air does much of the work needed to spin the fan.

I am not arguing that the mechanical fan is better. I plan on switching to electric myself. I am just saying that there is no free lunch. The power has to come from somewhere. There may be some gains with the e-fan, it just isn't going to be much (unless your clutch fan is bad). Some people just like the reliability of the mechanical fan.

CarlRx7

im with gsl-se addict. the alternator does create a harder load on the engine when i NEEDS more current. let your car sit for a month and your idle will be lower because you alt is harder to turn because your battery has been sitting and needs to charge.

the reason im installing an electric fan, is when i goto the track, im going to have an interupter switch on the thermostate to kill the fan when i pull up to the staging lights.

carl.

1stgen_tn

If you have a GSL, use your cruise control for the power source (not the fan itself, just the relay for the fan) and you can switch it on/off with the cruise control switch.

Pele

iTrader: (28)

I've actually SEEN alternators take more physical power to create more electrical power...

In my old Honda wagon, I tuned the idle and mixture on the carb precisely so that I'd get 35+ MPG... City... Dead on 500 RPM idle. Any lower and it'd run crappy and die if I stomped it...

Problem was, I tuned it during the day, following all the instructions under the hood... (All accessories, cooling fans, lightes, etc off.)

At night, raining, front and rear wipers on, lights on, cooling fans on, defroster on high, A/C on to get rid of the condensation, stereo on... Tap the brakes... Stalled the engine... ****...

So I retuned it with everythign ON... You could notice the difference turning on the Lights and Blower...

1stgen_tn

Just curious...what did your volt meter read during all this Pele?

I've always wandered about what low voltage can do to how a motor will run. I mean, you need so many amps/volts for correct spark, etc. I've had batteries and alternators going bad on me (on different cars) and when you turn on too many accesories, the volt meter drops to 12V or even 10V in some cases (should be at least 14V-right?). Obvouisly, this had an effect on engine performance (usually involving a bad miss). So, was it lack of proper voltage to run (OR) was it the alternator putting a huge draw on the motor trying to make up the needed electricity?

I've just always thought it was lack of proper voltage...

DAVID GRIMES

How much horsepower does an alternator pull ? You can mathematically determine the horsepower cost at any given load. (Remember, alternators respond to load. If there is no load present the alternator is basically freewheeling.)

So if you have an 85 amp alternator your maximum hp loss ( like when your battery is really low and/or you're cranking your stereo amps, etc.) is AT WORST:

Amps x Volts = Watts
Watts / 745.7 (one HP) = Electrical HP Produced by the Alternator
HP x 15% Efficiency Loss = HP Loss ( 85% efficiency is typical )
HP + HP Loss = Total HP Used


Example:
85A x 14.0V = 1190 Watts
1190 Watts / 745.7 = 1.6 HP
1.6 HP x 15% = 0.24 HP
1.6 + 0.24 = 1.84 HP Total AT FULL OUTPUT

If your average load is 42.5 amps ( very possible ), then your parasitic hp loss would average only .94 horsepower, etc.

Now we have an idea the HP cost to run the electrical system.

The question is what is the payback of using an electrical fan ( which adds to the alternator load ), and removing the clutch fan ? I will find these out and add to this post.

Another question: How much horsepower are you currently losing because of low electrical system voltage if you are using too small an alternator ?

You have to ask: How many amps do I need ?

The answer to that question depends on the electrical load. The real question is, "How many amps does my car use ?". This, of course, varies from car to car and can be figured two different ways. One way is to add the total amp requirements of all components together. Another way is to use an inductive ammeter with a "peak hold" function clamped around the battery cable while the car is running. The latter method would be more accurate since it would be testing the electrical system as a whole in real world conditions.

One thing to remember is that an alternator rated at 80A means that it is capable of producing 80A maximum. It does not produce power all the time but rather only when it is needed and only in the amount needed. Therefore if a car used 52A continuously a 60A alternator could be used. However, an 80A alternator would work better. Why ? Because the 80A alternator is working at 65% of its capacity whereas the 60A is working at 87% of its capacity. This percentage, or duty cycle, affects the voltage that the alternator is able to maintain. The 60A unit will typically produce the 52A at a lower voltage than the 80A unit in the same situation. Therefore it is good to get the alternator with the highest amp rating available for that particular mounting situation.

Another thing to consider is when do you need power the most ? On the track as with circle track racing ? Or on the return slip and in the pits as with drag racing ? The reason this is important is because it determines how the alternator is driven. Alternators put out less at idle than at high speed.

...to be continued

Pele

iTrader: (28)

That car didn't have a volt meter, so I don't know... But I do know the electrical system in that car will run on next to nothing... It was carbureted, and the ECU was vacuum powered (31+ individual vacuum lines running around the engine... It made our rat's nest look like child's play...) The fuel pump was mechanical as well, running off an extra lobe on the cam shaft... Alls I needed was spark...

There's several occasions where the alternator died and I was:

A.) Too lazy to get under and change it...
or
B.) Looking for the receipt so I could claim the lifetime warranty on it...

What I'd do is battery from the RX-7 I had lying around and throw it in the passenger seat along with the battery charger... I'd put jumper cables on the stock battery under the hood (There was enough clearance so I could close it if I put the clamps on right... They were secure too, they wouldn't fall off.) and put the cables out through the clearance near the cowl at the bottom of the windshield... Snake em around the passenger side view mirror and into the car via the window... I'd keep a hand held digital volt meter on the stock electrical system and watch it... When the voltage would dip too low, I'd hook up the 2nd battery... When I parked the car, I'd charge the batteries.

Roll start to save juice.

That car would run flawlessly all the way down to 8 volts. The headlights would have been too dim to be useful long before that. I could get a couple of hours of drive time out of it during the day. 30 mins at night in the rain...

I do know that I wasn't putting anywhere near the max 50 amp load on the stock alternator... It was the physical load on the engine... Like I said, I detuned it so well at idle it had no power... (But the city fuel economy was amazing and the tailpipe emissions at idle were cleaner than the air going down the intake... According to the emissions inspector...)


I was gonna bring this kinda stuff up, but I didn't have any hard calculations or anything and I'm too lazy to look em up... (Perhaps when I take physics at college, it'll go into a project...) Actually the alternator takes much less than I expected... But yeah...

Back in the day, I was raised by an electrical engineer... I had a soldering iron, volt meter, and basic tool set before I was out of the 3rd grade and was playing with mains voltage (120V AC here in the US) at that time... Probably explains a myriad of "issues" I have... But that's besides the point...

One Christmas, my father bought me a hand crankable generator kit, which I built... This generator would put out a bout 5 volts if you turned it at a couple hundred RPM. (It was gear driven.) But it was pretty easy to crank... My dad said, okay... That's without a load. Short it out and see what happens... Man the effort to crank it was 10 times worse, and it got worse the faster you cranked.

It goes to prove the property that energy [and matter] can not be created or destroyed, it can only be converted to other forms.

Crank RPM is converted to electrical energy in the alternator and some goes up in heat due to the bearings... Also some goes up in heat due to the electrical resistance of the windings...

Still trying to figure out whether converting it around from mechanical to electrical and back to mechancial is better than keeping it straight mechancial energy.

But also factor in the weight of the fan blades and clutch, the efficiency of how they're shaped (aerodynamics), how often the fan runs...

Many have said it's not much of an improvement, but you're removeing rotational mass... Kinda like a light flywheel. You're not gaining horsepower, you're freeing more for the rear wheels... Throttle response will go up... etc...

Plus you unload that belt that goes around the water pump... Might be able to get away with one belt if you've ditched the air pump.

I had something else I wanted to say, but I forgot what it was.

DAVID GRIMES

There are essentially three means available for engine temperature stabilization: a direct driven mechanical fan, a thermostatically modulated mechanical fan, and an electric motor driven fan.

In a typical application of a direct driven mechanical fan, about 15 HP is a consumed at maximum engine RPM. Moreover, as RPM increases, windage loss will increase at a cubed law rate. In other words, an increase in rotational speed from 5000 RPM to 6000 RPM will increase windage loss by a factor of (6/5)3 or 1.7:1.

A thermostatically modulated fan performs well under steady state conditions such as highway driving. On the other hand, during transient load conditions, such as a 1/4 mile run, the performance is similar to that of a direct driven fan as the rate of modulation is limited byway of the heat capacity of the mechanical clutch.

An electric fan is most efficient, a typical application drawing less than one horsepower. Moreover, modern electric fans have the capacity to control temperatures in almost any application.

So... Worst case? Even if you have a pegged out 85 amp alternator consuming 1.6 horsepower all the time ( not at all likely to be that high all the time ) and you have an electric fan that consumes two hosepower ( twice what's available ), and you have removed a clutch fan that had been robbing 7.5 horsepower ( less than typical ? ), then your net result would still be a 4.9 horsepower gain PLUS you have more amps for your electrical system.

Nominal case: You average using only .94 horsepower for your 85 amp alternator and your thermostatically controlled electric fan averages .5 horsepower ( 1 horsepower 1/2 the time ) consumption and you shitcanned your clutch fan that was robbing an average 7.5 horsepower ( 15 horsepower 1/2 the time ), then you would have 6.06 horsepower gain plus you have more amps for your electric system.

No matter how you slice it, losing the clutch fan and going to BOTH a larger alternator and an electric fan is smart, relatively cheap horsepower.

MosesX605

Maybe I missed it in your post, but where do you get a FOURTEEN HP loss from the clutch fan?

Sounds like a really high estimate to me.

DAVID GRIMES

I'm not guessing. I'm just getting a range of actual numbers and averaging. I'll try to be much more specific.

I now have the goods on the 2800 CFM Black Magic 150 Electric fans that so many of us choose as our electric fan. They are built with self triggering thermostats and claim to add approximately 10-12 horsepower by eliminating the stock fan and clutch assembly which robs the engine of horsepower.

They have a 13.9 amp current draw or .261 horsepower. That's max, not average and is much less than the .5 horsepower average I used in the above example.

To complete this "analysis" I really would love to see a dyno back-to-back with / without clutch fan or some reliable data from a clutch fan vendor on the torque required, etc. but it eludes me at the moment. I will complete this if I can drag the info up.

After this I think I want to visit the water pump as well. I wonder...

gsl-se addict

iTrader: (3)

Basically, there are two camps in the mechanical/electrical fan debate. One camp states that the clutch fan uses 10-15 hp, while the e-fan uses 0.25 - 0.75 hp (both during full operation) so the e-fan is a worthwhile upgrade.

The other camp states that there come be only a minor gain for the e-fan is any. This is because to move a fixed amount of air takes fixed amounts of hp for a given design fan. It doesn't matter what provides the driving force. So if the stock fan and e-fan had the same designed blades, the stock fan may be as efficient as or more efficient than the e-fan.

So there is definitely some discrepancy on the power than a mechanical fan consumes. No one is debating the power consumption of the e-fan because it is easy to measure. The differences in possible power consumption between the two lie in the fact that the mechanical and e-fans uses different blade designs and the mechanical fan may move more air than really needed. We will assume that both fans are shrouded, so that aspect doesn't play a role. Another possibility is that all fan blades, especially plastic, tend to flatten out with increased rpm, which in turn decreases efficiency. However, the clutch in the mechanical fans limits speeds to about 2000 rpm. Above this, you are just wasting power because of the blade flattening and the increased turbulence on the tips of the fan. I can't see that the mechanical fan is really 30 - 60 times more inefficient than the electric fan design. It may be slightly worse, but I doubt it is anywhere near that amount.

Forum member rotarydankusagain did do some dyno runs with/without clutch fan. He didn't post actual dyno plots though. According to him, the loss of the mechanical fan freed up 14hp. But, his data also showed that his e-fan on low took like 6hp and took 8hp on high (he was using a Taurus fan if I remember correctly, but we know the fan shouldn't take more than 0.5 hp so I am betting that the 14hp number isn't right either). You should be able to find his post by his username. He hasn't posted in quite awhile, so I don't know if he is around to provide further explanation.

The only way to really sort this out is to do some dyno runs. It would be beneficial if we could get data for multiple cars. That way we know the difference wasn't due to a bad fan clutch or changes in conditions between dyno pulls. I still think that a least an e-fan will clear up some space in the engine bay, doesn't cost much money, and may free up some power. Overall, I think that it is worthwhile, but others may disagree.

Kent