I was not saying what coolant temp the the jump is made at, because I think that varies by truck. I was saying that mine seems to make the jump at "X". I'll make a test run in a few hours and post back. I also believe on the GEMS and 14CUX verison of the ECM that it will drop out of closed loop if floored, or pushed hard, and return to stored map estimate.

I ran this past summer for a while with no stat, with 160 stat and with a 180 stat (not all at the same time, but sometimes all on the same weekend). In all cases I went to closed loop.

I think on a D2 the ECU holds cold idle at 1200 for like 20 seconds minimum on cold start to help warm up the cats.

 

Hmmm..just thinking out loud, could the ODB II software be adjusted for fan on/off temps? I know there are programmers out there. I could muse the already existing system, but with dual fans?? Another possibility is to use the OEM temp sensor located by the A/C pump for both the factory engine management needs and my fan set-up. I am not sure if I could run both off of one sensor.

If not I am betting the outlet hose area next to the block might be a good place to start. I can add it there using an inline sensor adapter.

--Mike

 

You would not want to use the engine coolant thermistor for dual duty. Where did the thermostat for your electric fans normally mount on the donor vehicle?

 

Don't think the closed loop switch over will be of interest for cooling fan.

Here's my test, cold start and just idle. 84F IAT 78Fcoolant temp

6:22 start
6:23 closed loop (took that long to get scanner to boot)
6:24 106F
6:25 111F
6:26 142F
6:27 169F
6:28 194F
6:29 201F
6:30 207F
6:31 180F

When I would rev engine it would go open loop. Turned off truck, let sit 5 minutes. Got scanner ready this time, switch on open loop), crank (open loop), 10 seconds later - closed loop. No codes.

So I would suggest that there is not a water jacket temp that "triggers" closed loop in the GEMS system. And you can expect initial temps with a mechanical stat to go 15 - 20 F over opening point, then it opens, cools rapidly, starts again. The following high points settle down to more normal levels over a few number of cycles.

While the Bosch system is different, suspect that it also does not use water jacket temp as the driving force, and instead depends on the heated O2 sensor.

The Bosch guide says that in the event of ECT failure, it will use a built in value that simulates a temperature rise to 150F, which is then used until engine is swiched off. This is yet another value thet Rover publishes. The D2 will turn off the AC compressor if coolant hits 255F (about darn time).

 

Savanna,
Thanks for getting that data and the advice on the thermistor. Shut of at 255F LOL, a bit too late at that point. The data you have showing the alternating temps based on the opening and closing of the T-Sat will help, although I have a Bosch motor and I am hoping it is some what comparable. Looking at the RAVE water flow chart what you stated makes a lot of sense. I just need to figure how I want to add the sensor and at what temp to set it.

May be letting the temp rise at first to say 204 and then turning the adjustment to on at that exact moment as a baseline. This will let me see how much more the temp will rise and to what point it drops back too. From that point I can start tuning it (at least for heat-up and idle) and see how well it deals with the fan on/off temp that is set. Also, while looking at the flow chart I was thinking a good place for the sensor would be the inlet at the top of the radiator. Yes, its after the T-Sat opens and behind the actual engine temp, but I would know that the engine is between 180 and 204, the opening and full open of the T-Sat. From there I can guess a good temp for the adjustable switch by watching the engine temp which I know is above 180 and climbing.

One other thought, I think you are right and its not water temp, but rather O2 sensors that trigger closed loop operation.

I like this discussion and I believe this will work if we can engineer it and keep running tests. Its killing me waiting for FedEx to bring the remaining parts, lol!

--Mike

 

If you find a way to reduce temps slightly, keep them stable, and increase mpg; there will be plenty of interest. Write about an idea the right way and it can fly like the Wright brothers.

 

Buzz, thank you for running that testing. I appreciate it. Ok, so closed loop is out of the question. Back to coolant temperature. Running it of the existing coolant sensor by programming the ecu, u might as well run standalone engine management. Best bet is to install a inline temp probe as soon as a hose leaves the block. The closer to the block, the better.

 

Another concern is the AC compressor. It is cooled by constant air flow thru the condenser, by a rad fan that is always there. Under certain conditions, the electric front fan turns on, but it does not run in step with compressor like a D1. So you could have a situation where front fan is off, truck is slow or parked, and no cooling for AC comprressor, high head pressure.....

from RAVE general datat:


temperature decreases to 25 °C (77 °F) [so if ambient is 77F or less, no front fan, again because it is not needed due to viscous fan drive taking the load]

IMHO, the potential exists with an electric fan conversion to properly cool the engine block, but cause havoc with the AC system. While it is true that increased condenser temps will increase the radiator temp and trigger fan eventually, that too depends on air flow. And our buddy the transmission cooler is there for a reason as well.

Just saying that while this can be done electrically, the relay logic employed may need to be modified so that cooling that is presently provided by a constant running main fan is not removed in such a way that the other systems that depend upon that same stream of air are compromised. Not a fair trade of head gaskets vs transmission and A/C. As an example, in a D1 the condenser fans run whenever AC is on, they don't cycle on/off.

Another issue would be amps. Might want to take a clamp on DC amp meter, measure alternator output with everything running (lights, wipers, AC, blower max, radio, brake lights, etc.). Let's say it comes to 120 amps. On a 130 amp alternator, does that leave extra to run new fan and charge battery? No fun if you have to sit in afternoon traffic in the rain and your battery is drained....

 

Set the fans to run at about 15% all the time. Or maybe it can be wired in with ac operation. When it sees power from the ac compressor, it turns the fans on to 20%. But that would leave trans temps to fate. Ideal situation would be to run the system at 15% all the time. Only saying 15% because they would be way more efficient that our current setup. And MJ, you are gonna have to test output of your alternator as well. I was actually thinking about that earlier. Uprated battery and alternator are gonna be needed. In addition, you might have to change the wiring off the alternator to battery to a slightly heavier guaged wire.

 

An by the way, I'm not saying don't do it. Just trying to think of the "gotcha's". Could measure things, like AC high side pressure, before and after on same temp days. And it should work, there are millions of cars out there with transverse mounted engines and electric fans.