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high water temps at second startup

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Old 07-12-18, 03:42 PM
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high water temps at second startup

Hey guys,
I have a quick question, I just got my car back together about 1 month and a half ago. I installed a PFC along with a datalogit and I have noticed that when I do a cold start then everything works fine but if I'm out just riding around and I stop at a store or wherever turn off the car and back on after like 5 mins my PFC will see water temps at about 105C and the car will start revving on its own just back and forward from 1k to 3k then the PFC will start dropping the water temp back down to 85C. Has anyone dealt with this problem and how to solve it? I also have an aftermarket radiator from rotary works with the stock fans. any help would be great!!
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Old 07-12-18, 05:16 PM
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Check to see what the setting are in the PFC and change to have the fans come on sooner. There are some great write ups on the two fans with the three fan relays and how that works so check that out as well. Basically when sitting at idle you loose the air flow from car moving, also the water pump being driven by the pulley and dependent on RPM does not help to compensate when at idle. The other issue is the air temps will get high as well, do not get on throttle until that drops as well, you can monitor air intake temps on the PFC as well.
This has always been a concern when sitting in traffic and watching the temps rise and not being able to do anything about it. I have gone to an electric water pump that is independent of pulleys and that has helped tremendously. Getting the fans to turn on to high will certainly help. Once that is done you can then see is your fuel map and temperature compensations may not be correct and modify those once the fans are working correctly as it may not need once that is done. Good luck.
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Old 07-12-18, 07:02 PM
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Originally Posted by stever View Post
Check to see what the setting are in the PFC and change to have the fans come on sooner. There are some great write ups on the two fans with the three fan relays and how that works so check that out as well. Basically when sitting at idle you loose the air flow from car moving, also the water pump being driven by the pulley and dependent on RPM does not help to compensate when at idle. The other issue is the air temps will get high as well, do not get on throttle until that drops as well, you can monitor air intake temps on the PFC as well.
This has always been a concern when sitting in traffic and watching the temps rise and not being able to do anything about it. I have gone to an electric water pump that is independent of pulleys and that has helped tremendously. Getting the fans to turn on to high will certainly help. Once that is done you can then see is your fuel map and temperature compensations may not be correct and modify those once the fans are working correctly as it may not need once that is done. Good luck.
Thanks for the info I will look into it, but I don't think I'm explaining myself correctly, the car has no problems while at idle or running. My problem is, for example, the car is cold I turn it on and wait for it to get up to temp before I start driving, normally my water temps stay between 83 and 88C once I get to my destination (grocery store ext..) the car is off for maybe 10 mins then when I get back to the car and turn it back on my PFC will display a 103 to 105C water temp even though the car never got that hot while driving. As a result, the car will start to rev bounds between 1k and 3k and PFC will start to drop what temp real rapidly back to 85C
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Old 07-12-18, 08:08 PM
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Ok perhaps you are really taking about heat soak, when stopped at a rest or for gas most RXers pop their hood to allow engine to not heat soak. Some add a tubo timer to run engine for a bit after stopping, a vented hood has helped me also the added benefit of a electric water pump is that it runs for a bit after shutting off the car to prevent the heat soak. lt's been awhile since I was stock but remember the fans coming on when turning engine off to help on cool down. If you are mostly stock the twins plus all the restricted space around the engine did make them prone to heat soak, common issue. Having spent the past years going single, vee mount, etc opening the area around the engine have not had that issue since and I do live in Arizona. For the buck I would go with an electric water pump, there are two vendors here on the site that supply kits. With that said don't ever remember hearing a failure due to this but all rotary guys are sensitive to heat and I have suffered the bouncing revs blues and glad now to "fingers crossed" not be experiencing that for some time. hope this was more on point for you.
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Old 07-13-18, 08:13 AM
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The temperature change is quite normal and shouldn't be a problem. The surging rpm could be caused by a lean condition at idle, try giving it some more fuel when the problem occurs.
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Old 07-14-18, 09:21 PM
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I've been monitoring temps lately and this seems to be the norm. Just heat soak. As said above, maybe your a little lean from the temp?? Mine doesn't do the rev thing, but she will get to 103-105 5min after shutdown.
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