Help! UD pullies and air conditioning
07-31-2006, 09:27 PM
#11
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RE: Help! UD pullies and air conditioning
ORIGINAL: hawgman
Yea, because that 15% decrease at 2500 rpm is going to make a difference in an electrical system that is designed to achieve maxium output at 2000 rpm. Same goes for the AC.
Yea, because that 15% decrease at 2500 rpm is going to make a difference in an electrical system that is designed to achieve maxium output at 2000 rpm. Same goes for the AC.
I for one would never say another word on the topic if someone could answer the question of why Ford chose not to change the pulley ratio after all these years of gearheads doing it?
Are the smaller pulleys heavy? Do they make noise? Are they more expensive? Do they change the emissions characteristics of the car? - let's see - no, no, no, no, hmmm...I honestly don't know what variables they considered, but all the logical one like making it work over the range their cars would see (Alaska to Dubais, Boston grid-lock to open roads in the mid-west...) would lead me to hypothisize that you are simply removing margin from a system that had some built in for places _most_ people don't live and driving conditions _most_ people don't see...
So, most of the time it works, and most of the time smoking does not kill you for a long time...
07-31-2006, 10:13 PM
#12
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RE: Help! UD pullies and air conditioning
I think Cekim's analysis is dead on.
Ford has to design their cars to work in a huge variety of conditions. They then have to design in a factor of safety in order to make sure things really work as they should.
If we fiddle with the pulley ratios, then we are reducing this capacity (or factor of safety as the case may be). That is a FACT--after all, the HP gain of a set of UDPs has to come from somewhere. Will this be enough to cause problems? Maybe, maybe not. It depends on your demands and what kind of risk you are willing to take. I think it is safe to say that for MOST people there won't be any problems. But that isn't a certainty.
Ford has to design their cars to work in a huge variety of conditions. They then have to design in a factor of safety in order to make sure things really work as they should.
If we fiddle with the pulley ratios, then we are reducing this capacity (or factor of safety as the case may be). That is a FACT--after all, the HP gain of a set of UDPs has to come from somewhere. Will this be enough to cause problems? Maybe, maybe not. It depends on your demands and what kind of risk you are willing to take. I think it is safe to say that for MOST people there won't be any problems. But that isn't a certainty.
08-01-2006, 11:10 AM
#13
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RE: Help! UD pullies and air conditioning
ORIGINAL: CrazyAl
I think Cekim's analysis is dead on.
Ford has to design their cars to work in a huge variety of conditions. They then have to design in a factor of safety in order to make sure things really work as they should.
If we fiddle with the pulley ratios, then we are reducing this capacity (or factor of safety as the case may be). That is a FACT--after all, the HP gain of a set of UDPs has to come from somewhere. Will this be enough to cause problems? Maybe, maybe not. It depends on your demands and what kind of risk you are willing to take. I think it is safe to say that for MOST people there won't be any problems. But that isn't a certainty.
I think Cekim's analysis is dead on.
Ford has to design their cars to work in a huge variety of conditions. They then have to design in a factor of safety in order to make sure things really work as they should.
If we fiddle with the pulley ratios, then we are reducing this capacity (or factor of safety as the case may be). That is a FACT--after all, the HP gain of a set of UDPs has to come from somewhere. Will this be enough to cause problems? Maybe, maybe not. It depends on your demands and what kind of risk you are willing to take. I think it is safe to say that for MOST people there won't be any problems. But that isn't a certainty.
Most people don't idle thier cars for long periods. Also, once the accesories are spun at a certain speed, increasing the speed doesn't make them do any more work.
UDP's leave less safety margin at idle, and also mean that instead of 2K giving peak output, peak output won't happen until 2.5K (example not actual numbers).
Also if the accesories spin 10% slower, they should last 10% longer.
Is the "MAX A/C" setting being used?
Is there a lot of stop-n-go driving?
If there is a lot of stop and go driving, I would consider upping the idle slightly, and making the radiator fans come on at lower temps.
08-01-2006, 12:05 PM
#14
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RE: Help! UD pullies and air conditioning
ORIGINAL: olym4gery
Most people don't idle thier cars for long periods. Also, once the accesories are spun at a certain speed, increasing the speed doesn't make them do any more work.
UDP's leave less safety margin at idle, and also mean that instead of 2K giving peak output, peak output won't happen until 2.5K (example not actual numbers).
Also if the accesories spin 10% slower, they should last 10% longer.
Most people don't idle thier cars for long periods. Also, once the accesories are spun at a certain speed, increasing the speed doesn't make them do any more work.
UDP's leave less safety margin at idle, and also mean that instead of 2K giving peak output, peak output won't happen until 2.5K (example not actual numbers).
Also if the accesories spin 10% slower, they should last 10% longer.
This is not entirely true.
Water pump: The flow rate of a water pump is directly proportional to the RPM at which it turns...which just so happens to correspond with the RPM (heat output) of the motor. And actually, since the water pump is centrifugal, it becomes exponentially LESS efficient the slower it turns. (Same principle as a centrifugal supercharger). Mechanical water pumps are great becasue as the RPM of the motor goes up (and thus the cooling needs go up), the pump output comes up as well. When you underdrive the water pump you are decreasing your cooling capability, especially at low RPM (idle) when the pump becomes less efficient.
Alternator:
Alternators under NO LOAD conditions will generate their peak voltage output at a fairly low RPM. HOWEVER, that fact is fairly meaningless in practicality. Voltage by itself means nothing if there isn't enough capacity (current -- Amps) to actually do work, and THAT is proportional to RPM. Furthermore, as the current demands go up, so does the electrical load on the alternator. UDPs are probably fine for many situations. But, if you're at cruising RPM (or stuck in traffic) with a lot of electrical draw: stereo cranked up, A/C or Heater fan blowing, headlights, and maybe some auxilliary stuff plugged into the car (extra lights or a GPS or laptop or whatever else) then that's a different story. Peak output will be reached at a much higher alternator RPM due to the added demands on the system.
AC Compressor:
The performance of the AC compressor is directly proportional to RPM. The faster it spins, the better it works. This becomes more critical when the condensor becomes hot--such as a hot day when you're moving slowly.
As has been discussed before, there is a reason why Ford designed things the way they did. UDPs are no more expensive or difficult to manufacture than the OEM pulleys. Ford could have installed "UDPs" from the factory and it wouldn't have cost them one single dime--AND they would have the bragging rights of even more HP to the ground. they didn't do this becasue it is a trade-off. They deliberatley CHOSE the OEM pulley ratios to deliver a certian accessory performance standard.
Now, I'm not saying that UDPs are necissarily a bad idea, or that your car will crash and burn if you have them. Far from it. Most people use them without problems at all. HOWEVER, if you use UDPs you need to understand that you are upsetting what the Ford engineers intended, and are decreasing the performance of the belt-driven accessories--which may or may not be a concern of yours. Personally I wouldn't hesitate to use them if I lived in a cooler climate. But here in south Texas, I want every bit of AC and water pump performance that I can get.
08-01-2006, 12:29 PM
#15
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Join Date: May 2006
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RE: Help! UD pullies and air conditioning
ORIGINAL: CrazyAl
This is not entirely true.
Water pump: The flow rate of a water pump is directly proportional to the RPM at which it turns...which just so happens to correspond with the RPM (heat output) of the motor. And actually, since the water pump is centrifugal, it becomes exponentially LESS efficient the slower it turns. (Same principle as a centrifugal supercharger). Mechanical water pumps are great becasue as the RPM of the motor goes up (and thus the cooling needs go up), the pump output comes up as well. When you underdrive the water pump you are decreasing your cooling capability, especially at low RPM (idle) when the pump becomes less efficient.
ORIGINAL: olym4gery
Most people don't idle thier cars for long periods. Also, once the accesories are spun at a certain speed, increasing the speed doesn't make them do any more work.
UDP's leave less safety margin at idle, and also mean that instead of 2K giving peak output, peak output won't happen until 2.5K (example not actual numbers).
Also if the accesories spin 10% slower, they should last 10% longer.
Most people don't idle thier cars for long periods. Also, once the accesories are spun at a certain speed, increasing the speed doesn't make them do any more work.
UDP's leave less safety margin at idle, and also mean that instead of 2K giving peak output, peak output won't happen until 2.5K (example not actual numbers).
Also if the accesories spin 10% slower, they should last 10% longer.
This is not entirely true.
Water pump: The flow rate of a water pump is directly proportional to the RPM at which it turns...which just so happens to correspond with the RPM (heat output) of the motor. And actually, since the water pump is centrifugal, it becomes exponentially LESS efficient the slower it turns. (Same principle as a centrifugal supercharger). Mechanical water pumps are great becasue as the RPM of the motor goes up (and thus the cooling needs go up), the pump output comes up as well. When you underdrive the water pump you are decreasing your cooling capability, especially at low RPM (idle) when the pump becomes less efficient.
So increasing the amount of coolant flowing through the cooling system will not make it work better. There is a maximum flow level, that if surpassed will make the cooling system less capable of cooling the engine.
Alternator:
Alternators under NO LOAD conditions will generate their peak voltage output at a fairly low RPM. HOWEVER, that fact is fairly meaningless in practicality. Voltage by itself means nothing if there isn't enough capacity (current -- Amps) to actually do work, and THAT is proportional to RPM. Furthermore, as the current demands go up, so does the electrical load on the alternator. UDPs are probably fine for many situations. But, if you're at cruising RPM (or stuck in traffic) with a lot of electrical draw: stereo cranked up, A/C or Heater fan blowing, headlights, and maybe some auxilliary stuff plugged into the car (extra lights or a GPS or laptop or whatever else) then that's a different story. Peak output will be reached at a much higher alternator RPM due to the added demands on the system.
Alternators under NO LOAD conditions will generate their peak voltage output at a fairly low RPM. HOWEVER, that fact is fairly meaningless in practicality. Voltage by itself means nothing if there isn't enough capacity (current -- Amps) to actually do work, and THAT is proportional to RPM. Furthermore, as the current demands go up, so does the electrical load on the alternator. UDPs are probably fine for many situations. But, if you're at cruising RPM (or stuck in traffic) with a lot of electrical draw: stereo cranked up, A/C or Heater fan blowing, headlights, and maybe some auxilliary stuff plugged into the car (extra lights or a GPS or laptop or whatever else) then that's a different story. Peak output will be reached at a much higher alternator RPM due to the added demands on the system.
I could get into the fact that the altenator is regulated, and only generating enough power to run the car, so increasing the RPM's doesn't increase the output.
AC Compressor:
The performance of the AC compressor is directly proportional to RPM. The faster it spins, the better it works. This becomes more critical when the condensor becomes hot--such as a hot day when you're moving slowly.
The performance of the AC compressor is directly proportional to RPM. The faster it spins, the better it works. This becomes more critical when the condensor becomes hot--such as a hot day when you're moving slowly.
As has been discussed before, there is a reason why Ford designed things the way they did.
Most people won't do that continuous idle. Even at a slow speed, 1,200 RPMS in 1st gear, the air going through the radiator will siginfigantly increase the coolant and A/C's ability to work properly.
UDPs are no more expensive or difficult to manufacture than the OEM pulleys. Ford could have installed "UDPs" from the factory and it wouldn't have cost them one single dime--AND they would have the bragging rights of even more HP to the ground. they didn't do this becasue it is a trade-off. They deliberatley CHOSE the OEM pulley ratios to deliver a certian accessory performance standard.
Or the LCA's
Or the rear axle ratio
The A/C, water pump, and altenator are factory designed to do what they have to do at idle, indefinitely. Since most people don't idle their cars for hours on end, they drive them, losing the ability to idle indefinitley, and gaining some horsepower is a good trade for most people.
Now, I'm not saying that UDPs are necissarily a bad idea, or that your car will crash and burn if you have them. Far from it. Most people use them without problems at all. HOWEVER, if you use UDPs you need to understand that you are upsetting what the Ford engineers intended, and are decreasing the performance of the belt-driven accessories--which may or may not be a concern of yours. Personally I wouldn't hesitate to use them if I lived in a cooler climate. But here in south Texas, I want every bit of AC and water pump performance that I can get.
08-01-2006, 02:41 PM
#16
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RE: Help! UD pullies and air conditioning
ORIGINAL: olym4gery
Just like they chose the airbox that was designed into the car, right? Aftermarket parts like CAI's can often improve on performance.
Just like they chose the airbox that was designed into the car, right? Aftermarket parts like CAI's can often improve on performance.
Or the LCA's
Or the rear axle ratio
The A/C, water pump, and altenator are factory designed to do what they have to do at idle, indefinitely. Since most people don't idle their cars for hours on end, they drive them, losing the ability to idle indefinitley, and gaining some horsepower is a good trade for most people.
It is also a trade-off of "duty cycle"... Alternators/AC more so than water pump are only "on" periodically... The slower you spin them, the more they are "on" - which is what wears them out - not spinning itself, but OPERATING.
As far cavitation - well... I'll let John Force worry about that - I don't spend enough time at redline to give a hoot...
Human beings are positively LOUSY at associating long-term outcome with causation... We look at the most immediate action and result and jump to conclusions - this is how we work and most of the time it works just fine...
This is one of those cases where it fails... "works for me" is meaningless for this analysis - the only answer you are going to get is unsatisfyingly statistical...
08-01-2006, 03:06 PM
#17
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RE: Help! UD pullies and air conditioning
cekim has some great points on once agian.
You can't compare the UDPs to those other common mods. The airbox, LCA, gears, and so on are all tradeoffs, just like the UDPs. When we install those mods we are swapping something for something else. Sometimes it's purely cost-for-performance like the LCAs. Other times it is fuel economy (gears), etc. Many common mods sacrifice emissions quality for performance. In the case of UDPs we are sacrificing a little engine cooling, electrical power output, and A/C system performance in exchange for a few more HP.
As for the water pump, sure, if the pump spins too fast it could cavitate--and if you pump the water too fast you're not helping things any. But we're not talking about "overdriving" the pump--those points are all moot. We're talking about leaving it at the OEM spec (where it works fine) or slowing it down. I'm pretty damn sure that it doesn't cavitate from the factory. Would you rather have the cooling system running at OEM capacity, or at REDUCED capacity? Increasing coolant flow might not be any better (I can't say "WILL" because you and I don't know what the critical flow rates for the S197 are). However, slowing the pump down DOES make it work worse. Worse enough to get you into trouble? Probably not. But maybe.
Alternator: Keep in mind that one of the main jobs of the alternator is to keep up with the demands of the fuel pump, ignition, and EFI system. These demands are linked to RPM. So at Idle there is some constant running demand on the electrical system. But, as the RPMs climb, those demands increase as the aforementioned components need more power to keep functioning, adding to the base requirement at idle. The "fan belt" links together the alternator and the engine at a given ratio. As the engine rpms climb so does the alternator. This is by design: as the power requirements go up, so does the alternator output. When you screw with the pulleys you are throwing that ratio off. Can the alternator still keep up with the engine demands with UDPs? Again, probably. But not certianly.
...by the way, I'm interested to hear that you know that "2000 rpm" is the magic number for the alternator's peak output. Do you have a copy of the output curves for the alternator? Becasue if so, we could put this argument to rest for all time.
AC: Sure the compressor cycles. But, if it is spinning slower, it's duty cycle will be shifted much more to the "on" side rather than the "off" side. In other words, you are running the compressor that much "harder". And, on the "Max" setting (Which I frequently use in the Texas heat) the output is outright diminished. In either case, the pressure at the compressor discharge is probably reduced, which is going to reduce the efficiency of the expansion cycle that the AC system works at.
IF you prefer, you can look at it in this regard. Installing UDPs gives you a HP boost at the wheels. That HP has to come from somewhere--you don't get power out of thin air. The answer is that is being re-diverted from other sources such as on the alternator and the AC compressor. If your "theory" about cycling the compressor and the "magic regulator" in the alternator was all there was to it, then there simply wouldn't be any HP to take away and UDPs wouldn't do anything past Idle RPM. Aside from a very small inertial component, for every 1 HP that you "steal" from the alternator, that is about 700 watts less output you're getting. For every 1 HP you take from the compressor, that corresponds to some number of BTUs worth of cooling that you're not getting...etc..
You can't compare the UDPs to those other common mods. The airbox, LCA, gears, and so on are all tradeoffs, just like the UDPs. When we install those mods we are swapping something for something else. Sometimes it's purely cost-for-performance like the LCAs. Other times it is fuel economy (gears), etc. Many common mods sacrifice emissions quality for performance. In the case of UDPs we are sacrificing a little engine cooling, electrical power output, and A/C system performance in exchange for a few more HP.
As for the water pump, sure, if the pump spins too fast it could cavitate--and if you pump the water too fast you're not helping things any. But we're not talking about "overdriving" the pump--those points are all moot. We're talking about leaving it at the OEM spec (where it works fine) or slowing it down. I'm pretty damn sure that it doesn't cavitate from the factory. Would you rather have the cooling system running at OEM capacity, or at REDUCED capacity? Increasing coolant flow might not be any better (I can't say "WILL" because you and I don't know what the critical flow rates for the S197 are). However, slowing the pump down DOES make it work worse. Worse enough to get you into trouble? Probably not. But maybe.
Alternator: Keep in mind that one of the main jobs of the alternator is to keep up with the demands of the fuel pump, ignition, and EFI system. These demands are linked to RPM. So at Idle there is some constant running demand on the electrical system. But, as the RPMs climb, those demands increase as the aforementioned components need more power to keep functioning, adding to the base requirement at idle. The "fan belt" links together the alternator and the engine at a given ratio. As the engine rpms climb so does the alternator. This is by design: as the power requirements go up, so does the alternator output. When you screw with the pulleys you are throwing that ratio off. Can the alternator still keep up with the engine demands with UDPs? Again, probably. But not certianly.
...by the way, I'm interested to hear that you know that "2000 rpm" is the magic number for the alternator's peak output. Do you have a copy of the output curves for the alternator? Becasue if so, we could put this argument to rest for all time.
AC: Sure the compressor cycles. But, if it is spinning slower, it's duty cycle will be shifted much more to the "on" side rather than the "off" side. In other words, you are running the compressor that much "harder". And, on the "Max" setting (Which I frequently use in the Texas heat) the output is outright diminished. In either case, the pressure at the compressor discharge is probably reduced, which is going to reduce the efficiency of the expansion cycle that the AC system works at.
IF you prefer, you can look at it in this regard. Installing UDPs gives you a HP boost at the wheels. That HP has to come from somewhere--you don't get power out of thin air. The answer is that is being re-diverted from other sources such as on the alternator and the AC compressor. If your "theory" about cycling the compressor and the "magic regulator" in the alternator was all there was to it, then there simply wouldn't be any HP to take away and UDPs wouldn't do anything past Idle RPM. Aside from a very small inertial component, for every 1 HP that you "steal" from the alternator, that is about 700 watts less output you're getting. For every 1 HP you take from the compressor, that corresponds to some number of BTUs worth of cooling that you're not getting...etc..
08-03-2006, 12:43 AM
#18
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RE: Help! UD pullies and air conditioning
OK,As I am wont to do, I did a LOT of research. on this.
Contacted Steeda. I can post their reply, but basically their tests and history show never a problem in this regard. My dealer: ditto. Hawgman , Thanx, and you are right. It doesn't seem to be a problem. ALL accessoriies have a peak output/rpm ratio, beyond which, there is no benefit, but still continue to rob power at some mathematical function rate; and it's fairly low. I've been driving all summer in 100+ degrees, with the recent change. Why? Uhm. Seems the temp control, which is EXTREMELY easy to move, had gotten bumped on one of those #3 shifts, and got stuck just far enough not to see it, and it took a force, to put it back. Once I really punched it, it's back to quite cool. Also no overheat problems, even at stoplights.
Other info, water flo is NOT directly proportional to rpm. the flow maxes out rather quickly (I believe it is a 4th power function, except at ONLY the low end where it loses power (re: while energy/ rpm increases at about a 2.5 power, but have to check the Thermo books...
olym4gery. Great info, what can I add, except that w/ UD pullies, the idle rpm may start going down on the curve. That's what precipitated my question, figuring out where that point is.
Thanx, ALL. Great info!
JDC
Contacted Steeda. I can post their reply, but basically their tests and history show never a problem in this regard. My dealer: ditto. Hawgman , Thanx, and you are right. It doesn't seem to be a problem. ALL accessoriies have a peak output/rpm ratio, beyond which, there is no benefit, but still continue to rob power at some mathematical function rate; and it's fairly low. I've been driving all summer in 100+ degrees, with the recent change. Why? Uhm. Seems the temp control, which is EXTREMELY easy to move, had gotten bumped on one of those #3 shifts, and got stuck just far enough not to see it, and it took a force, to put it back. Once I really punched it, it's back to quite cool. Also no overheat problems, even at stoplights.
Other info, water flo is NOT directly proportional to rpm. the flow maxes out rather quickly (I believe it is a 4th power function, except at ONLY the low end where it loses power (re: while energy/ rpm increases at about a 2.5 power, but have to check the Thermo books...
olym4gery. Great info, what can I add, except that w/ UD pullies, the idle rpm may start going down on the curve. That's what precipitated my question, figuring out where that point is.
Thanx, ALL. Great info!
JDC
08-03-2006, 10:53 AM
#19
Join Date: Jul 2006
Posts: 17
RE: Help! UD pullies and air conditioning
Aside from a very small inertial component, for every 1 HP that you "steal" from the alternator, that is about 700 watts less output you're getting.
If this 700 watt per HP number is documented somewhere, and you don't mind sharing where it can be found, I'd really like to read up on this topic so I can make a better decision on the use of UDPs. I'm not sure I'd want to give up that kind of charging capacity.
UDPs - It looks like people either love them or hate them.
08-03-2006, 11:18 AM
#20
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RE: Help! UD pullies and air conditioning
Well, I have some more fun to add to this debate...
So, for all of you who assume that Ford is just lazy or otherwise just does not care enough to give you your free horsepower...
I was pulling my car apart last night and went to change the pulley on the alternator (Saleen reverses the belt direction on the Alternator) and what do I find?[
]
They have put a "slip" pulley on the alternator...
If you spin it fast with your hand, the pulley actually slips past the alternator core! (intentionally it seems there is a bearing in the hub - if this is not intentional - WOW would it be defective
But I believe it is intentional...)
Clearly they have thought about this a lot as what they have done is now allow the engine to accelerate faster than the alternator... So, when revving up and/or at high RPMS the alternator will lag the engine's aceleration (reducing the intertial drag to accelerate the alternator)...
As I said before - if it works for you:
a. wait a while - then decide
b. crank up your 1KW radio and air conditioning in 100F heat
c. you might be lucky
d. you might live somewhere where the conditions give you enough margin to get away with it...
But, the issue is not that Ford just "left horsepower on the table" - the issue is you are removing the margin of saftey and need to be aware of that!!!
This is a lot like overclocking CPUs - yes it often works and even more often for a little while - but you cannot "see" electron migration (which always happens and happens faster when you run too hot or too fast for the part), so it won't work as long as it would have otherwise...
But people insist that Intel/AMD are just leaving MHz on the table to charge them more...[8D]
So, for all of you who assume that Ford is just lazy or otherwise just does not care enough to give you your free horsepower...
I was pulling my car apart last night and went to change the pulley on the alternator (Saleen reverses the belt direction on the Alternator) and what do I find?[
]They have put a "slip" pulley on the alternator...
If you spin it fast with your hand, the pulley actually slips past the alternator core! (intentionally it seems there is a bearing in the hub - if this is not intentional - WOW would it be defective
But I believe it is intentional...)Clearly they have thought about this a lot as what they have done is now allow the engine to accelerate faster than the alternator... So, when revving up and/or at high RPMS the alternator will lag the engine's aceleration (reducing the intertial drag to accelerate the alternator)...
As I said before - if it works for you:
a. wait a while - then decide
b. crank up your 1KW radio and air conditioning in 100F heat
c. you might be lucky
d. you might live somewhere where the conditions give you enough margin to get away with it...
But, the issue is not that Ford just "left horsepower on the table" - the issue is you are removing the margin of saftey and need to be aware of that!!!
This is a lot like overclocking CPUs - yes it often works and even more often for a little while - but you cannot "see" electron migration (which always happens and happens faster when you run too hot or too fast for the part), so it won't work as long as it would have otherwise...
But people insist that Intel/AMD are just leaving MHz on the table to charge them more...[8D]