dprantl

Right, but the problem is when you put in a lower temp thermostat, its effect is defeated in hot weather because the fans are calibrated for the stock temp thermostat. I guess most people will run a stock thermostat, but for a modified car it can be desirable to run a little cooler than the factory intended.

Dan
'91 928GT S/C 475hp/460lb.ft

dr bob

Old wives' cars maybe.

Five or ten degrees colder thermostat gives you a couple needle-widths of "gauge comfort", a few 'extra' seconds when you hit the system capacty limit. Perhaps a reason to stick with the original-temp thermostat? Avoids driving around in cold-start-enrichment mode if nothing else. I used a lower-temp thermostat for a while, but went back to normal temp thermostat so there wouldn't be more than that same two needle-widths of gauge reading difference between summer and winter. Except for humidity, your climate is amazingly similar to mine AFA temp ranges and all.

86'928S MeteorGrey

Any progress on this replacement fan speed amp being discussed? I've got people with open wallets ready right now...

John Speake

Bump.....

jleidel

Sorry for the significant delay. Our company recently went through some significant layoffs [25% of engineering was axed]. As such, our EE team has been playing catchup since the holidays. We currently have a valid spice model of the functional circuit. I hope to get back to playing with it this week.

928 at last

John,
Excuse my ignorance, but a "spice model"?

jleidel

SPICE = Simulated Program with Integrated Circuit Emphasis
http://en.wikipedia.org/wiki/SPICE

Its basically a software simulation of your target circuit. It allows us to simulate the circuit and ensure that it performs as designed before going to the fab. It also allows us to play with the selection of individual components if we find similar [but not exact] replacements.

928 at last

Thanks John.
That just made today not a waste. I learned something new.
Not only that, but I didn't even know that that was possible!

Lorenfb

"It allows us to simulate the circuit and ensure that it performs as designed before going to the fab."

For simple circuits like this, others use a basic 'breadboard' where an actual
'live' test can be evaluated with real components. Like the old adage for
computer operations, "Garbage in = Garbage out".

worf928

And mastodons were once killed and rendered by first slowing them with hand-chipped flit-tipped arrows and then overwhelming them with numbers of axes, spears and knives.

New times. New tools. There's still a place in the process for knives, but the heavier lifting can be done with vastly more efficient tools.

Alan

fraggle

If it works with pro's in spice moving the manufactuing is a **** ton simpler. Bravo! Is there going to be an easy way to kick the fans on full from an external input? I'd love to have this option when I know I'll be stuck in near parked traffic for 15 minutes - to help reduct the heat soak before it happens.

jleidel

Loren, we're very good at this process. Building a simulation using proven methods is both faster and more accurate than a breadboard method. "Breadboarding" is fine when playing with circuits for hobby projects. However, it doesn't allow one to easily play with multiple components and it can be quite prone to user errors [which adds to the development costs].

Our lab guys built a software model of a 27-layer PCB w/ both through-hole and surface mounted components. The board supports over 60 SERDES links pumping at 1Ghz [each] and 200+ components totaling ~$9k in capital costs [for each board]. They did it right the first time. No design errors when the first boards came back from the fab.

I'd say that "precision in = precision out".

jleidel

fraggle, we could probably incorporate such a thing. If we added an additional pinout that allowed one to bypass the overall temp circuit. I would also be prudent to add a countdown timer to it... hmm... me thinks this could work.

SeanR

:P