added UD pulley's, need to change anything?

[Jackpine]

Full on, Sburn! VERY well presented post! It's what I like about this forum, people actually have brains over here and they use them!

I'm glad you did the research on the power loss, since I was too lazy/incompetent to do so. And it gives me a platform to comment.

IF, the 1.6 HP penalty is correct, and it sounds pretty good to me given the power demand figure you quote for the e-fans, then stopped at idle, it's kind of a "wash" isn't it? The e-fans are using a constant 1.6 HP, and the new PCM controlled fan's needs vary between quite low (at engine idle, since it is not turning very fast) to higher at cruising speeds - where it should be freewheeling anyway.

Now, the only thing that power demand does at idle is use a bit more fuel (in both cases) and, for the amount of time we're usually stopped, I doubt we'll feel much difference in the AC. So, the PCM controlled fan may win out in economy at idle and not make us too uncomfortable.

But, I don't know when the e-fan controller cuts it off as speed increases. I think it is purely temperature controlled, so it's possible the PCM controlled fan might cut off sooner, as a speed increase is seen?

And, since both should usually be off at highway speeds, we're left with your final statement. Is there any clutch drag with the new fan? The ram airflow through the radiator is going to encounter both kinds of fans and will try to spin them and all of this causes aerodynamic drag. But, the drag would be there anyway, since the engine and engine bay is not exactly a "slippery" aerodynamic shape. So, we spin the e-fans by airflow and get nothing in return since they are "decoupled". We spin the "water pump" fan and, if there is any clutch drag at all, we decrease its drag on engine power. But, if there's no clutch drag (does there have to be?) there's actually no power loss to the engine.

I know there was always some power loss through the fluid clutch since it is always ON. But, could the new clutch be purely (or effectively) mechanical? I doubt the new design would have been adopted if there were no real benefits. The fluid coupled fan was "simple", and it worked, but there was always drag. Maybe the drag was eliminated in the new, more complicated design?

- Jack

[Sburn]

Originally Posted by JackandJanet

Now, the only thing that power demand does at idle is use a bit more fuel (in both cases) and, for the amount of time we're usually stopped, I doubt we'll feel much difference in the AC. So, the PCM controlled fan may win out in economy at idle and not make us too uncomfortable.

But, I don't know when the e-fan controller cuts it off as speed increases. I think it is purely temperature controlled, so it's possible the PCM controlled fan might cut off sooner, as a speed increase is seen?

There's two flavors of e-fan controllers that I know of. Simple Off/On at a preset temprature (~thermostat temp) and PWM e-fan controllers that vary the e-fan speed based on the temp. sensed at either the radiator or by piggybacking on the factory ECT/CHT. So, the e-fan with a smart controller wouldn't always have to be running at 100% when it's on.

I know there was always some power loss through the fluid clutch since it is always ON. But, could the new clutch be purely (or effectively) mechanical? I doubt the new design would have been adopted if there were no real benefits. The fluid coupled fan was "simple", and it worked, but there was always drag. Maybe the drag was eliminated in the new, more complicated design?

- Jack

I'm not yet sure how the clutch works on the new PCM fans. Could be a PWM to some kind of solenoid that squishes some hydraulic bits, or a variable DC voltage to a magnetic particle clutch. I'll have to RTFM this weekend. Or, drag out the old oscilloscope.

Ford's PID show the fan RPM sensor and PCM output to the clutch as a percentage, but I don't yet know if the percentage mean duty cycle or a voltage:

[Jackpine]

Or, if you had access to a 2008+ truck, you could try spinning the fan by hand with the engine stopped. If you feel drag, it's going to be there anytime the engine is turning.

- Jack

[Sburn]

Originally Posted by JackandJanet

Or, if you had access to a 2008+ truck, you could try spinning the fan by hand with the engine stopped. If you feel drag, it's going to be there anytime the engine is turning.

- Jack

So, you're suggesting I might hook a fish scale up to the fan with the engine stopped and measure the drag as torque, right? That could be good to know. Not sure about 2008+, but my 2007 does have some drag when stopped, so whatever scheme the clutch is, it's not perfect.

[Jackpine]

Originally Posted by Sburn

So, you're suggesting I might hook a fish scale up to the fan with the engine stopped and measure the drag as torque, right? That could be good to know. Not sure about 2008+, but my 2007 does have some drag when stopped, so whatever scheme the clutch is, it's not perfect.

I thought you said the change was in the 2008 MY. My 2005 certainly has viscous drag when I attempt to spin it by hand with the engine stopped. I haven't actually tried this, but as I understand it, the drag should be greater if the engine is hot. (I'll have to give it a try). In my engine, the fan ALWAYS turns, but, it is supposed to turn faster (closer to engine speed) with the engine hot. (I know you know this, I'm just adding it for anybody who may not understand how a viscous clutch works).

I doubt you could measure it with a fish scale though on a stopped engine. You'd need to catch the fan to a scale mounted on a rafter or something and measure the force on the stalled fan with the engine running. Then, you could calculate the torque/hp loss from this force and the distance you had the "hook" from the hub. It's not something I'd like to try, since it sounds a bit dangerous.

But, if there is NO resistance in the 2008+ line, then that is a whole different clutch! And, you should be able to compare the relative resistances in different MY trucks by feel.

- Jack

[Sburn]

Originally Posted by JackandJanet

I thought you said the change was in the 2008 MY.

2006 or 2007, AFAIK. PCM-controlled fans have a harness with connector a 5 wires that sit between the water pump pulley and the fan hub.

My 2005 certainly has viscous drag when I attempt to spin it by hand with the engine stopped. I haven't actually tried this, but as I understand it, the drag should be greater if the engine is hot.

If harder to turn when hot and no wiring, then that sound like your 2005 has thermo controlled clutch.

I doubt you could measure it with a fish scale though on a stopped engine. You'd need to catch the fan to a scale mounted on a rafter or something and measure the force on the stalled fan with the engine running. Then, you could calculate the torque/hp loss from this force and the distance you had the "hook" from the hub. It's not something I'd like to try, since it sounds a bit dangerous.

Right, not a good idea to do it that way.

[88Racing]

Here is some more reading on fans:http://dygytalworld.ehost-services13...read.php?t=467

Lars