Coolant flow

[Bitsyncmaster]

My biggest problem making smarter "relays" is I'm limited to 5 pins. I think I can hold more stable temps with an electronic otterstat. PWM of the fans is going to make a lot of electrical noise and not gain much improvement. I made my fan relay hold 20 seconds just to stop the switching of fans on and off to reduce engine load changes at idle and improve the AC capability.

You defiantly don't want the fans to cool if the thermostat has not opened which is why (my guess) the otterstat was put in the outlet.

Fans have to run anyway when the AC is on which is most of the time in summer.

[DMC-Ron]

Dave,
Well you're right. The AC mode makes this discussion somewhat of a mute point. Don't think you need any more pins on the relay but the delay-off feature would need to be shifted to the electronic otterstat.
All-in-all, too much trouble for, as you say, very little gain. And I just had a discussion with my son (electrical engineer) and he said many of the newer DC motors wouldn't tolerate PWM.

Appreciate the discussion and all your effort on behalf of the DeLorean community.
Thanks,
Ron

[PJ Grady Inc.]

How about because that's where the circulating coolant is hottest?

I agree with this. I don't think it was coincidental that the otterstat is located almost directly above the catalytic converter.

[funkstuf]

The one point that seemed salient was that different radiators cool at different rates, and therefore, without monitoring the actual temperature of the fluid leaving the engine, there is some risk that the engine temp might get too hot if one is monitoring the fluid after it's been cooled. Having the otterstat at the point where it leaves the engine appears to be a safer solution if nothing else, because it's reflective of the engine temp. I still contend, that regardless of where the otterstat sits, it will take the same amount of fan time to cool the engine 20 degrees. That being said, it seems it would be difficult to improve the current design, unless one designs a control system designed to keep the engine in a tighter temperature range by continuously varying fan speed. My understanding, is that when the vehicle is moving over about 25 mph, the fans shouldn't be needed. Such is the case with my Delorean. The fans don't come on, unless the vehicle sits and idles, or is in stop and go, and speeds under 25 mph. That being said, it's interesting to consider potentially, new and more efficient ways to cool. If you read the specs, the fan shutoff temp is above the thermostat open temperature, but not a lot. For that reason, I don't see big advantages in using the variable temp otterstat that's available either. If one turns it down much it doesn't work properly because the thermostat reduces circulation before the engine reaches the target temp. I think the stock design is somewhat difficult to improve, other than to upgrade the old high current fans to the newer more efficient ones. One problem I have seen on hot days in parades is that the old fans run so much they melt all the wires and housing on the 3 prong fused fan fail fix in the relay box, but don't blow the fuses because the current isn't high enough to blow them. (I've seen this happen twice in the last couple years on cars without the fan replacement). Sorry for diverging.

[Bitsyncmaster]

One problem I have seen on hot days in parades is that the old fans run so much they melt all the wires and housing on the 3 prong fused fan fail fix in the relay box, but don't blow the fuses because the current isn't high enough to blow them. (I've seen this happen twice in the last couple years on cars without the fan replacement). Sorry for diverging.

Check out my old thread about those fuses melting.

http://dmctalk.org/showthread.php?12...t=fuse+testing

[Ron]

The one point that seemed salient was that different radiators cool at different rates, and therefore, without monitoring the actual temperature of the fluid leaving the engine, there is some risk that the engine temp might get too hot if one is monitoring the fluid after it's been cooled. Having the otterstat at the point where it leaves the engine appears to be a safer solution if nothing else, because it's reflective of the engine temp. I still contend, that regardless of where the otterstat sits, it will take the same amount of fan time to cool the engine 20 degrees....