Alan

Dave - was there a reason you didn't just put the fan on the end of the stock alternator hose/shroud in the fender?

Alan

j.kenzie@sbcglobal.net

Hi Alan,
I would have liked to use the stock items. Unfortunately the stock duct is a little less than 3" and I have no shroud on my aftermarket alternator.
Dave

LT Texan

All these years and I keep coming back to this.

The stock set up. But can you up rate the stock alternator to put out a bit more current to handle an electric radiator fan with everything else on?

j.kenzie@sbcglobal.net

I wanted to give a follow up on this project. I bought a 3" marine bilge blower and some flexible ducting. I routed it from the front brake cooling grille through the factory alternator duct route to the rear of the aftermarket alternator. I have about $30 invested. I wired it to come on with ignition. No thermostat as yet. It is a little noisy, like a hair drier, but it works great. My voltage remains good when the engine is hot. By good, I mean always greater than 13.0V at 800RPM, hot, at the cigar lighter with a digital meter.
Most of the time, at 1500 RPM it gives 14.0-14.5V.
I think it is a pretty good improvement.
Dave

mark kibort

who needs 180amps??? i think ours are rated at near 80amps, and mine has been fine until i sucked iin a rock to the armature. (broke an armature winding by having the rock spin around at break neck speeds).
otherwise, it takes 10amps to drive the alternator. it responds to voltage drops to the battery and the real only wear factor , is the brushes which will wear out in 70-100k miles. it looses efficiency as they wear do to spring tension on the commutator.

Now, if you have your 5000watt stereo blasting, you need a higher capacity alternator and need to worry about cooling it. OR if you race, you want a lighter one, because the stock one is a beast. ive never noticed any unusual heat in the alternator, street or race.

The Fixer

Hi Dave,

The muscle car guys seem to like to use alternators that are powder coated black in color to radiate the heat.

I did this but with VHT engine enamel and modified my aluminum protective plate (w forward facing louvres) to shoot cool air up to the alternator which is directly above it. An NACA duct could be made also and look very Porsche. I didn't want to take the time making a true NACA duct and the hammered louvres seem to be doing the job. The aluminum is easy to louver with a wide sharp chisel on a wood block with hammer.

I don't need the ventilation cowl anymore.

j.kenzie@sbcglobal.net

Hi Mark,
I need more amps than the standard 80. My supercharged car has only electric fans to cool it. The supercharger takes the space normally used by the engine driven fan. That leaves me in need of about 30=35 amps of electric cooling. If you add in other sources of load such as lights, a/c system w/blower, etc., you will find that you have inadequate alternator output at idle on a hot day. I am not doing this for fun. My volt meter (digital) read 10.8 volts worst case before this mod, now, so far the lowest is 12.4 volts.
Dave

j.kenzie@sbcglobal.net

Hi Matt,
Thanks for the suggestions.
Dave

mark kibort

I have only electric fans too. i also used to have the eRAM on the 5 liter version of this system that was 60amps. voltage never dropped below 13.5volts. with the battery alone, that voltage of 12.6 nominal dropped to about 12.0v with the 60amp load. (this will be battery dependent)
my fans, which one is on during a race and two, almost never, are about 10amps each, and then another 10 for having the car be running.. Ive never and you shouldn't either, get the voltage much below 13v with near capacity of the stock alternator. if you were near 10.6volts with a stock alternator, that alternator was bad...... plus, just because you have a 60 or 80amp load, it doesn't mean you have that coming from the alternator. the voltage drop determines this and the alternator provides more and more current depending on the voltage drop. keep in mind, i have a stock GT alternator, with a larger pulley, so its going slower than stock and never goes below 13volts. both fans running, car running and idling. (and a mini 13lb battery)

j.kenzie@sbcglobal.net

Mark,
At mid throttle rpm's I have always had plenty of voltage too. In bumper to bumper traffic at 800 rpm, with high load and high ambient temps, I get 10.6 volts. I bet you are not racing in bumper to bumper traffic at 800 rpm. If I was driving at any kind of speed, my alternator would give plenty of juice too. Unfortunately, that is not always the case. Have you ever seen an alternator output curve of amps vs. rpm? Your 80 amp alternator is not giving you much more than 30 amps at idle. Sorry, but I think that is true for me, and most other people too.
Thanks for trying to help.
Dave

j.kenzie@sbcglobal.net

Also, Mark,
I looked really hard to find efficient electric fans. There is no electric fan that will cool a stock, much less an upgraded engine, at idle, in 90 degree weather and draw 10 amps. Just not out there. Can't do it with 20 amps either. I can just barely do it with 35 amps. with really efficienct fans.
Sorry,
Dave

dr bob

Dave-- smaller wiring will reduce the current draw, but would need better high-temp insulation.

If that's the real goal....

j.kenzie@sbcglobal.net

Sorry Bob,
What wiring are you referring to? In the fans, alternator, or elsewhere?
Thanks,
Dave

Alan

Mark - I'm not sure what you mean by this? but the alternator certainly doesn't provide more current as the voltage drops... in fact the voltage drops because the alternator can't supply the power that is being asked of it at its rated voltage setpoint - Voltage must droop to compensate - its the only way the power goes down (so voltage & current both drop). Now the stock regulator is indeed a little over aggressive in regard to temperature deration.

This is the critical element here - ambient temperature and local "ambient conditions" at the alternator in particular that drive the regulator temp. deration.

In Phoenix at 120F you will not find a 928 Bosch alternator that will make good power (and sustain set point voltage) at low (idle) RPMs with a heat soaked engine. Remember under these conditions the AC & blower will be on max and the cooling fans will likely be on at full power almost constantly. Make it night time with lights on and even if its a little cooler say 100F-105F+ it will be no better. Bring your car here in July and find out for yourself.

The issue is very real but primarily only for very hot environments, if you see similar somewhere cool - you have some other issue (regulator/diodes... etc)

Alan

dr bob

Fans, but was a tongue-in-cheek suggestion. Smaller wires mean more resistance and more heat, but less current flows. Fans will last a lot longer since they will be spinning slower too. Not a perfect solution to any particular problem really, except high current draw.