GT Pump vs. Stock Fuel Pump & Alternator Tips

[Zack]

This may be trivial info, but I thought it was relevant to High Horsepower cars.

Before switching to the GT Pump, I watched my Duty Cycle on the ScanGauge. It was between 28-32 just cruising around.
After I switched to the GT Pump, the Duty Cycle dropped to 17-19

I may be speaking Greek, but thats HUGE... in a good way!

When you reach 100% Duty Cycle at WOT, your pump is maxed out.

Another thing I did in preparation of my Dyno Tune tomorrow is swap the clutched alternator pulley for a standard model. This will send 14+ Volts to the fuel pump at WOT vs. Battery Voltage only.
Part # for the pulley is: F5OY-10344-F from Ford. You will need a different alternator pulley nut which can be hard to find. I suggest a local electrical shop that rebuilds alternators. If you dont have the tool to get the clutched pulley off, use an air chisel to unthread it.....it works quite well..

Also.. you can bypass swapping the pulley altogether by tach welding the 2 piece clutched pulley together. Simply take the car to a welder, pop the cap on the pulley, tach it up and go! No more Voltage loss at WOT.

Hope this was helpful

[Joe Walsh]

The clutched alternator pulley is just a one-way clutch to prevent belt chirp due to overspinning of the pulley.

It works like a 10 speeds bicycle's rear hub...you can power it one way, but it free wheels the other way.

I've got the one-way clutched alternator and would NOT change it, nor weld it together.
If you run the alternator mounted backwards (like a Trilogy install) then you must replace the clutched pulley.

The charging at WOT function is handled by the computer.

BTW: Good update on the GT fuel pump. I've got to order one from Ray The Dealer soon.

[Zack]

The clutched alternator pulley is just a one-way clutch to prevent belt chirp due to overspinning of the pulley.

It works like a 10 speeds bicycle's rear hub...you can power it one way, but it free wheels the other way.

I've got the one-way clutched alternator and would NOT change it, nor weld it together.
If you run the alternator mounted backwards (like a Trilogy install) then you must replace the clutched pulley.

The charging at WOT function is handled by the computer.

BTW: Good update on the GT fuel pump. I've got to order one from Ray The Dealer soon.

Yes it is. As far as I know, the SCT software cant override it. I tried doing it in the software with no luck. Jerry W. Had to hook up his 'Black Box' back in 03 to override it.
I do know swapping pulleys remedies the problem.

Hey Trilogy guys, does your voltage drop at WOT?

[RoyLPita]

The Trilogy guys also have the tool that removes the clutch puuley from the alternator.

[DOOM]

Whats the price for the gt fuel pump?

[Zack]

Whats the price for the gt fuel pump?

About $90


Please discuss the alternator pulley in more detail.
If Im wrong about it, thats fine! Id rather get the straight scoop sooner than later.

[O's Fan Rich]

I have no voltage drop at WOT that I have noticed.
But then again I drive her like I'm an old lady.

[Zack]

http://www.mercurymarauder.net/forum...ad.php?t=16262

I found this old post composed by you Joe

I can agree with the clutch and how it works, but if the clutch is freewheeling at WOT, that means the alternator is not spinning, regardless of the PCM controlling it or not.

Does that make sense?

[Breadfan]

http://www.mercurymarauder.net/forum...ad.php?t=16262

I found this old post composed by you Joe

I can agree with the clutch and how it works, but if the clutch is freewheeling at WOT, that means the alternator is not spinning, regardless of the PCM controlling it or not.

Does that make sense?

Is the clutch just one way or is it electromagnetically controlled as well? If that were the case, the computer could "energize" the clutch on and off at will.

I'm only running 2 gauges at teh moment oil pressure and boost and no scanguage I cannot comment much, I suppose I could datalog the Xcal2 maybe that'd give some insight.

EDIT: NM I read the post that it's not electromagnetic but fully mechanical.

[Zack]

The clutch is mechanically driven only.

Here's my argument:

On a blower car, at the dragstrip or on the freeway...
If you go WOT for extended periods of time, that alternator clutch will be freewheeling the entire time.
That means that over the course of the WOT run, the actual 'guts' of the alternator will be slowing down or eventually stop altogether! Which ultimately leaves you with battery voltage and nothing more.

Im happy I switched to a regular pulley, I will adjust the tune so the PCM commands the alternator to make at least 13-13.5 volts at WOT.

[Breadfan]

If the only reason is for increased belt life and/or no chirping I'd say for a performance minded MM you'd be better off. I see your logic too on a S/C car getting a pump voltage drop at WOT could result in a less fuel flow when you need it.

I suppose this would be built into the tune since it would be tuned on WOT runs as well, but after several times or with a weak battery you could end up with low voltage/low flow.

If the clutched pulley is gone though, what advantage is there in stopping the alternator? If I read the link right, the computer just sort of shuts it off, so in theory even with a non-clutched pulley the PCM could turn off the alternator.

What sort of benefit would that be, without freewheeling it, you'd still need to turn the mass of the alternator just you wouldn't be getting any juice from it. Or is there less parasitic loss if it's not switched "on"?

[Paul T. Casey]

The clutched pulley adds to the "sinisterness" and "coolness" of the car. I like it when my lights go dim when I mash it. The premiss behind the design was to free up some extra RWHP at WOT. I'm not sure how much RWHP an alternator eats up, but hey, we're talking Ford Engineering here.

[FordNut]

Wow, it's amazing that this is coming up again.

The clutched pulley is a one-way clutch. It will let the alternator spin FASTER than the pulley but never spin SLOWER than the pulley.

The light dimming or output voltage dropping at WOT is controlled by the PCM and it works in a totally different way. It simply turns off the field voltage so the alternator doesn't put out any voltage even though it is still spinning. That takes the electromagnetic load and therefore the mechanical load off the alternator to free up a wee bit more horsepower.

The reason for changing the pulley for Trilogy cars is that the alternator spins the opposite direction and the one-way clutch would constantly slip, never producing output voltage from the alternator.

[Breadfan]

OK, so an energized alternator takes more effort to spin than an unenergized one, I was wondering where the hp gains would be if you're still physically turning the unit!

[Zack]

Im confused