is buying and installing electric fans into a 240sx worth the money and time? do you feel the power that was free'd up? all comes to all, is it worth the bang for the buck... how much difference did you feel afterwards?
sorry for the newbieish questions, im just broke and looking for something to free up and add some power
Electric Fans, are they worth the money?
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NIGHTfall_240sx
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I replaced mine and went with a flexalite. To tell you the truth I did not notice that much difference. I do not think it's a worthwile investment. In fact this topic comes up a lot in the rx-7 forums (engine known for running really hot) and most members agree and swear by the mechanical fan up to 350+ horses. It is mostly done to give space in the engine bay or mount thick radiators.
I am seriously considering going back to the mechanical, but I do not know if the stock 240sx fan suffers more problems than the rx-7 fan.
You see, the main argument is that the 240's fan creates drag as you speed up (making the fan spin faster). However this is a statement that makes no sense, since the clutch fan is viscously filled and the fan goes into free play (virtually no drag) as the viscous matter cools via fast air through the radiator. You can try it by spinning your fan with your hand when it's cold (should be easy) and then again when you have reached operating temp. (should be locked in). Of course you do this with the engine off. There are other arguments that I think apply to the 240's fan as well, and I'll post them uP:
You see, we are not gaining power if our fan is on all the time either (mine is, but i'm just too lazy to fix it right now) because the advantage of the electric fan is that it takes away the alternator drag when the thermostat shuts it off, so having it on all the time robs you more than the mechanical unit would....
Taken from: http://www.aaroncake.net/RX-7/efanmyth.htmThe Myth Of The Electric Fan
--------------------------------------------------------------------------------
Electric fans are an often discussed modification on the various RX-7 forums. Unfortunately, it seems that there is also a lot of inaccurate information surrounding the "e-fan" and how it should be installed. This document will hopefully answer some of the most common questions with regards to e-fans, and debunk some of the myths.
Before we begin, let's just take a general overview of the cooling system on the RX-7. Forget for a moment that there is also an oil cooler. We will just concentrate on the water cooling system.
The cooling system consists of 5 basic parts: the engine, the water pump, the radiator, fan and the thermostat. Water passages inside the engine are filled with a coolant/water mixture (commonly just called "coolant"). These passages allow the heat that is generated within the engine to transfer into the coolant. Coolant is circulated through the engine via a water pump, which is driven from a belt off of the main eccentric shaft pulley. The stock fan and fan clutch assembly also mounts of the shaft of the water pump, and is therefore driven by the engine as well. The pump's job is to circulate water though the engine and the radiator. Air flowing over the radiator cools the coolant, and thus the engine. A thermostat is used to open or close flow of coolant through the rad to maintain the engine temperature at a constant (180 F).
Now that we know how the cooling system works, let's be clear about the function of the fan, and how the clutch assembly works. As mentioned, the stock clutch fan is attached to the water pump shaft. This shaft receives it's rotation from the engine itself. The fan is not directly attached to the shaft, it is actually bolted to a viscous clutch. The clutch then sits between the fan and the shaft. The purpose of the clutch is to keep the fan at a (fairly) constant speed, and to only engage the fan when it is needed. Think of the clutch as a very simple mini torque converter. Inside is a fluid. When this fluid is cool, the clutch is freewheeling, and thus the fan turns relatively slowly as the clutch slips. As the engine heats up, so does the clutch as hot air from the rad flows over it. The fluid thickens up, engaging the clutch and turning the fan at engine speed up to about 2000 RPM. At this point, it begins to slip again to keep the fan at the most efficient speed. Thus, more air flows through the rad, cooling the engine. The clutch cools down as the engine does, and then disengages. Thus, the cycle repeats. The (very crude) image below illustrates the assembly.
What's important to note is that the fan is only used when the engine is idling, or the car is creeping along at low speed (less then 20 MPH). If the car is stationary or creeping, there is not enough natural airflow through the rad to provide adequate cooling. Thus, the necessity of a fan.
Now that we know the basic operation of the cooling system and fan, let's look at the electric fan.
By far, the most common misconception is that the electric fan cools better then the stock. People see the high CFM numbers in the catalogues (for example, the Black Magic is advertised as pulling 2,800 CFM, and the Perma Cool "finger chopper" is advertised at 2,950 CFM) and are impressed. The truth is that no one actually knows the CFM rating of the stock fan. It has simply never been measured by anyone but Mazda. All we do know is that it is rated at "a lot". And to be honest, who cares how much air the stock fan moves? It is more then adaquate as long as it's clutch and the rest of the cooling system is in good shape. The steeply raked blades of the stock fan move quite a lot of air, even if it turns slower then an aftermarket electric unit. Experience has shown that when in good shape, the stock fan is even easily capable of handling a 400HP engine (aftermarket rad installed). How much power do you make?
Many people also seem to believe that an electric fan will cure their "at speed" overheating problems. Recall that the fan is not even used when at speed, as the natural flow of the of air through the radiator is more then enough (much more then a fan, in fact) to keep the car cool.
Of course, you're not necessarily after better cooling. You've seen those TV commercials or catalogue ads that promise "Up to 17 free HP!" by converting to an electric fan. Well, that's simply not true. There will be a horsepower gain for sure, on the order of 0.5 - 1HP. But remember that the electric power to run the fan must come from somewhere, and that somewhere is the alternator. Electric fans draw quite a lot of current. Most pull surges of 35A or more to start up, then run at 8A-10A. This puts extra load on the alternator. Ever pedaled a bicycle with a generator powered light? If so, then you will know that as the electrical load on a generator/alternator increases, the generator/alternator becomes harder to turn. Suddenly, all that "free" HP you just freed up is once again being used. This time, though, it is being used to turn the alternator. There is also an inefficiency in the whole system. We are converting mechanical energy, to electrical energy, to mechanical again to run the fan. This very inefficient, much less then just driving the fan directly via the mechanical energy of the rotating shaft.
We can see that the electric fan is a large current draw. The '86-'88 alternator is rated at 70A, and the 89+ unit is rated at 90A. Real world tests have shown that actual output is somewhat less then the specifications would indicate. Add the load of the electric fan, and you are that much closer to overloading an already factory-stressed electrical system.
While on the subject of the electrical system, let's look at how the fan is actually connected. The proper way to control an electric fan is via a thermostat and relay combination (fused, of course). Unfortunately, very few people actually do this. Many installations simply connect the fan to run all the time, or to a switch inside the car. In the latter case, your brain actually becomes the thermostat. Needless to say, this is a very poor arrangement as it is easy forget to switch on the fan as the temperature climbs. Worse still, the 1989+ temperature gauge is horribly inaccurate. By the time you see it move, the car is already too hot. Leaving the fan on all the time presents a different set of problems. It becomes an unnecessary drain on the system, and may actually over cool the car. This is not necessarily a flaw of the fan itself, but of the installer.
Lastly, there is the question of reliability. The stock clutch fan can have two failure modes: the clutch will fail, or the fan will physically break. The electric fan introduces many more failure points: fuse, all wiring connections, physical failure of the fan, failure of the motor, failure of the thermostat.
By now, you're probably wondering "Gee, why is this guy so against electric fans?". Well, I'm not really. But I recognize their disadvantages. There are also some useful advantages to the electric fan.
Since you are no longer tied to the shaft of the water pump, the electric fan can be oriented in any way, and moved around to make space. Without the stock fan shroud in the way, there is much more room in the engine bay, as well as room to route things like intercooler piping, cold air intakes, etc. An electric fan may also be required when going to certain aftermarket radiators that do not have provision for mounting the stock fan shroud.
The electric fan can also be left on after the engine is shut off. This allows continuous cooling to minimize heat soak. A small turbo timer like device can be used to run the fan for a preset amount of time. The 3rd gen RX-7 actually does this from the factory, but that is about the only good point in the 3rd gen cooling system.
Perhaps the greatest advantage of the electric fan is cost. It provides an affordable alternative to replacing a failed stock clutch fan. The stock unit is very expensive when purchased new, so it is possible to save several hundred dollars by purchasing an electric fan instead. However, this advantage is not as great if you have a decent wrecking yard in your area. Used clutch fans are very cheap.
There you have it. For the most part, electric fans are not recommended as an upgrade unless you have a very specific reason to do so. They provide inferior cooling to the stock fan, and may create other problems if improperly installed. If you want to install an electric fan, I have done a basic writeup of the generic process. Read How To Properly Install An Electric Fan.[
I am seriously considering going back to the mechanical, but I do not know if the stock 240sx fan suffers more problems than the rx-7 fan.
You see, the main argument is that the 240's fan creates drag as you speed up (making the fan spin faster). However this is a statement that makes no sense, since the clutch fan is viscously filled and the fan goes into free play (virtually no drag) as the viscous matter cools via fast air through the radiator. You can try it by spinning your fan with your hand when it's cold (should be easy) and then again when you have reached operating temp. (should be locked in). Of course you do this with the engine off. There are other arguments that I think apply to the 240's fan as well, and I'll post them uP:
You see, we are not gaining power if our fan is on all the time either (mine is, but i'm just too lazy to fix it right now) because the advantage of the electric fan is that it takes away the alternator drag when the thermostat shuts it off, so having it on all the time robs you more than the mechanical unit would....
Taken from: http://www.aaroncake.net/RX-7/efanmyth.htmThe Myth Of The Electric Fan
--------------------------------------------------------------------------------
Electric fans are an often discussed modification on the various RX-7 forums. Unfortunately, it seems that there is also a lot of inaccurate information surrounding the "e-fan" and how it should be installed. This document will hopefully answer some of the most common questions with regards to e-fans, and debunk some of the myths.
Before we begin, let's just take a general overview of the cooling system on the RX-7. Forget for a moment that there is also an oil cooler. We will just concentrate on the water cooling system.
The cooling system consists of 5 basic parts: the engine, the water pump, the radiator, fan and the thermostat. Water passages inside the engine are filled with a coolant/water mixture (commonly just called "coolant"). These passages allow the heat that is generated within the engine to transfer into the coolant. Coolant is circulated through the engine via a water pump, which is driven from a belt off of the main eccentric shaft pulley. The stock fan and fan clutch assembly also mounts of the shaft of the water pump, and is therefore driven by the engine as well. The pump's job is to circulate water though the engine and the radiator. Air flowing over the radiator cools the coolant, and thus the engine. A thermostat is used to open or close flow of coolant through the rad to maintain the engine temperature at a constant (180 F).
Now that we know how the cooling system works, let's be clear about the function of the fan, and how the clutch assembly works. As mentioned, the stock clutch fan is attached to the water pump shaft. This shaft receives it's rotation from the engine itself. The fan is not directly attached to the shaft, it is actually bolted to a viscous clutch. The clutch then sits between the fan and the shaft. The purpose of the clutch is to keep the fan at a (fairly) constant speed, and to only engage the fan when it is needed. Think of the clutch as a very simple mini torque converter. Inside is a fluid. When this fluid is cool, the clutch is freewheeling, and thus the fan turns relatively slowly as the clutch slips. As the engine heats up, so does the clutch as hot air from the rad flows over it. The fluid thickens up, engaging the clutch and turning the fan at engine speed up to about 2000 RPM. At this point, it begins to slip again to keep the fan at the most efficient speed. Thus, more air flows through the rad, cooling the engine. The clutch cools down as the engine does, and then disengages. Thus, the cycle repeats. The (very crude) image below illustrates the assembly.
What's important to note is that the fan is only used when the engine is idling, or the car is creeping along at low speed (less then 20 MPH). If the car is stationary or creeping, there is not enough natural airflow through the rad to provide adequate cooling. Thus, the necessity of a fan.
Now that we know the basic operation of the cooling system and fan, let's look at the electric fan.
By far, the most common misconception is that the electric fan cools better then the stock. People see the high CFM numbers in the catalogues (for example, the Black Magic is advertised as pulling 2,800 CFM, and the Perma Cool "finger chopper" is advertised at 2,950 CFM) and are impressed. The truth is that no one actually knows the CFM rating of the stock fan. It has simply never been measured by anyone but Mazda. All we do know is that it is rated at "a lot". And to be honest, who cares how much air the stock fan moves? It is more then adaquate as long as it's clutch and the rest of the cooling system is in good shape. The steeply raked blades of the stock fan move quite a lot of air, even if it turns slower then an aftermarket electric unit. Experience has shown that when in good shape, the stock fan is even easily capable of handling a 400HP engine (aftermarket rad installed). How much power do you make?
Many people also seem to believe that an electric fan will cure their "at speed" overheating problems. Recall that the fan is not even used when at speed, as the natural flow of the of air through the radiator is more then enough (much more then a fan, in fact) to keep the car cool.
Of course, you're not necessarily after better cooling. You've seen those TV commercials or catalogue ads that promise "Up to 17 free HP!" by converting to an electric fan. Well, that's simply not true. There will be a horsepower gain for sure, on the order of 0.5 - 1HP. But remember that the electric power to run the fan must come from somewhere, and that somewhere is the alternator. Electric fans draw quite a lot of current. Most pull surges of 35A or more to start up, then run at 8A-10A. This puts extra load on the alternator. Ever pedaled a bicycle with a generator powered light? If so, then you will know that as the electrical load on a generator/alternator increases, the generator/alternator becomes harder to turn. Suddenly, all that "free" HP you just freed up is once again being used. This time, though, it is being used to turn the alternator. There is also an inefficiency in the whole system. We are converting mechanical energy, to electrical energy, to mechanical again to run the fan. This very inefficient, much less then just driving the fan directly via the mechanical energy of the rotating shaft.
We can see that the electric fan is a large current draw. The '86-'88 alternator is rated at 70A, and the 89+ unit is rated at 90A. Real world tests have shown that actual output is somewhat less then the specifications would indicate. Add the load of the electric fan, and you are that much closer to overloading an already factory-stressed electrical system.
While on the subject of the electrical system, let's look at how the fan is actually connected. The proper way to control an electric fan is via a thermostat and relay combination (fused, of course). Unfortunately, very few people actually do this. Many installations simply connect the fan to run all the time, or to a switch inside the car. In the latter case, your brain actually becomes the thermostat. Needless to say, this is a very poor arrangement as it is easy forget to switch on the fan as the temperature climbs. Worse still, the 1989+ temperature gauge is horribly inaccurate. By the time you see it move, the car is already too hot. Leaving the fan on all the time presents a different set of problems. It becomes an unnecessary drain on the system, and may actually over cool the car. This is not necessarily a flaw of the fan itself, but of the installer.
Lastly, there is the question of reliability. The stock clutch fan can have two failure modes: the clutch will fail, or the fan will physically break. The electric fan introduces many more failure points: fuse, all wiring connections, physical failure of the fan, failure of the motor, failure of the thermostat.
By now, you're probably wondering "Gee, why is this guy so against electric fans?". Well, I'm not really. But I recognize their disadvantages. There are also some useful advantages to the electric fan.
Since you are no longer tied to the shaft of the water pump, the electric fan can be oriented in any way, and moved around to make space. Without the stock fan shroud in the way, there is much more room in the engine bay, as well as room to route things like intercooler piping, cold air intakes, etc. An electric fan may also be required when going to certain aftermarket radiators that do not have provision for mounting the stock fan shroud.
The electric fan can also be left on after the engine is shut off. This allows continuous cooling to minimize heat soak. A small turbo timer like device can be used to run the fan for a preset amount of time. The 3rd gen RX-7 actually does this from the factory, but that is about the only good point in the 3rd gen cooling system.
Perhaps the greatest advantage of the electric fan is cost. It provides an affordable alternative to replacing a failed stock clutch fan. The stock unit is very expensive when purchased new, so it is possible to save several hundred dollars by purchasing an electric fan instead. However, this advantage is not as great if you have a decent wrecking yard in your area. Used clutch fans are very cheap.
There you have it. For the most part, electric fans are not recommended as an upgrade unless you have a very specific reason to do so. They provide inferior cooling to the stock fan, and may create other problems if improperly installed. If you want to install an electric fan, I have done a basic writeup of the generic process. Read How To Properly Install An Electric Fan.[
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NIGHTfall_240sx
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