SharkSkin

Interesting.... I found it to be very anemic. The Spal fan I replaced it with REALLY moves some air... The difference is noticeable even standing at the side of the car where the hot air exits. BTW I measured the current on my old fan at 17 amps... was there more than one fan offered in 78?

Old & New

The earliest fan was about 3" thick, has just five blades, and moves an enormous amount of air; it is unlike the 1.5" thick unit in the newer cars.

SharkSkin

Yeah, like in the pic below.... maybe there was something wrong with mine, because I sure wasn't impressed with it.

heinrich

OK Doug, I view the 928 engine is just another engine. I find that the more I remove from my own mind the mystique of this car's being a Porsche, and the more I focus on the fact that it is a car like any other, the better I do. I'm in the process of deleting many of the voodoo items from my car, and I find that with each new change comes a bit more reliability, some performance and much more enjopyment for me.

Only a short couple of years ago we were told the 928 engine was such a complicated piece of voodoo that you could not possibly hope to supercharge it without disaster. I personally spent weeks if not months of my life working on induction improvements, and spent much time talking with real 928 experts like Louie Ott.

Today the intake is gone from my engine and a verry basic airbox is in its place. Aftermarket thermostat. Aftermarket wires. Aftermarket exhaust that btw looks nothing like stock. The huge factory fans are gone. So is a ton of other highly-sophisticated cool ****. How much voodoo have I lost? Not enough. How much horsepower have I gained? More than 100. How reliable is my car? Never fails.

I used to be steeped in Porsche voodoo and I too feared the Jabberwock. Today I am reborn.

heinrich

Not to mention the ridiculous oil breather system.

Old & New

Dave,

17 amps sounds like the fan was worn out or something. I measure 30 and need to run a high current relay; the typical Bosch 30 amp relays don't last long.

Also, unless you position a gasket between the radiators, you will not get a laminar flow through the coolant radiator. Remember, the pusher was originally intended to cool the A/C radiator.

SharkSkin

Well, thanks... that explains it... sort of...

Doug Hillary

Hi,
Dave - my compliments on your wonderful site - especially the fan transplant - great stuff and a credit to you! And helpful to all of us!!!

heinrich - your "tons of tech-talk" comment made me laugh. You have 4.10 posts per day and I have 0.55, I'll have to decide to post more or less often! I'm very decisive - I think!!

However just refer to the first post in this thread again - heinrich, if you had posted earlier the initiator could have spoken to the real experts instead of the rest of us hobos and picked up an extra 100hp by now as well! Keep smiling!!!

Regards
Doug

T_MaX

OK, let me see if I have this right.

Q. If dave has a fan that pulls 17 amps and O&N has a fan that pulls 30 amps, whos fan shows to be worn out?

A. O&N?

I base this on O&N statement, "I measure 30 and need to run a high current relay; the typical Bosch 30 amp relays don't last long."

I have always been under the impression that if you have two fans that are the same, the one that pulls higher amps is the one that is showing its age.

heinrich

Ok man.

jorj7

When I first got my 90 S4 it ran hot. I changed the coolant (75% water,
the rest antifreeze with a bottle of water wetter), cleaned the radiator, replaced
one of the electric fans that wasn't working, disabled the front flaps, and installed
a 75 degree thermostat. One or more of these fixed the overheating problem.

T_MaX

George, your right coolant ratio does make a difference, I think some 89-91's have a problem with the fan controllers. I also believe that Porsche knew of this problem, as in 91 or 92 they upped the wire sizes and changed the controllers programming.("JMO", but I am willing to put my money up for the R&D to find out )

SharkSkin

-O&N, it sounds like your fan has a more powerful motor. Or, as Curtis said, it's going south. Since you also seem to get much greater output than I did, I'm thinking maybe mine had a broken winding or some such issue. Still, I find it very interesting that the new fan moves much, MUCH more air yet only draws 18 amps... one more amp, and it weighs 2 pounds less. Seems to be a net improvement no matter how I slice it.

IMHO gaskets are unnecessary since the sheer volume and velocity of the air that I can feel coming through to the back side of the radiator, and the great draft of hot air I can feel at the side of the car coming from underneath sort of indicates that there is plenty of airflow. Yes, there is noticeable spillage of air, but compared to the amount of air that is getting forced through the radiator it's insignificant.

-Doug, thanks for the compliments... One of my primary goals with the site is to give something back to the community that I've found so helpful. There was so little info floating around on the OBs when I started that I felt that even my ramblings and stumblings would constitute a net positive. It's always good to hear opinions that support that.

-Curtis, that is a decent rule of thumb if you have a valid baseline with which to pick out the oddball. All we have are two data points with no assurance that both fans were equal in the first place. Assuming they were, then mine could be exhibiting a failure mode along the lines of an open winding... relatively rare. If O&N's fan was drawing more current and moving LESS air, I would suspect that unit to be verging on failure. But maybe his simply has a more powerful motor.

BTW I'm running a gallon of DexCool, Redline Wetter, and the balance is distilled water FWIW.

Old & New

Curtis, Dave,

Agreed that we don't have much data for conclusions. Would someone else please attach a clamp-on ammeter to their early style 3" fan and report back? Truth be told, I questioned whether 30A was proper when I tested & installed it. But it was what I had on hand at the time and I liked the idea of installing an OEM part.

I ran a heavy cable from the ABS post to the fan. There is no line loss here. The circuit breaker is rated at 40A and the relay is a 70A unit. I have only to install a quenching diode to complete the project.

The fan spins up instantly with a roar and menacingly dares you to loose a finger to its blades. It is very old, but my gut feeling is that this fan is 100%.

I found what I deemed to be a significant amount of air recirculating, blowing out from between the radiators at the sides. It is an efficiency game, so I figured why give anything away? After gasketing a circle mirroring the fan housing, I have an impressive blast of air exiting the rear of the radiator, reminiscent of a mechanical fan.

SharkSkin

Too bad we can't directly compare airflow as well. Hmmm.... mine's not in the car... I could find the maximum distance at which my fan will blow over a beer can...