My goal is to get 25+ mpg from my 99 XJ with 30 x 9.5 R15 ATs - Page 6 - JeepForum.com
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Unread 07-25-2013, 04:08 PM   #76
Charley3
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1999 XJ Cherokee 
 
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Quote:
Originally Posted by ninjakid View Post
Couldn't you splice into the coolant temperature sensor in the thermostat housing?
I thought all later cherokees have them at least.
I toyed with the idea of going all electric for cooling but most fans pull quite a few amps especially during spinup and the charging system on it isn't quite up to it currently and I figured I'd work on some other stuff on it before taking a look at the idea again in the future.
Good idea about using stock stat housing sensor. I was considering that. However, I might need a second sensor (that activates at a different temp) so each fan comes on at a different time.

---

Fans (or any electric motor) that lack a capacitor pull a lot of amps on startup, if they start at full power.

If it has a capacitor, it doesn't draw much amps at startup. This can work good, but I've heard capacitors have some risks.

Another way to reduce draw at startup is to have each fan start at a different temp. That is my preference, but might require a separate sensor?

Another way (Flexalite's way) is to start at 60% of fan capacity, and then increase if temp increases. I might like this method too (not sure).

I think the 2nd two methods are commonly used by OEM car manufacturers.

So there are a few ways to avoid a big amp draw at start up.

---

Whatever you do, don't use a radiator probe because they don't work well. The thermostat housing is the best place to monitor engine temps, IMO.

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Unread 07-25-2013, 05:30 PM   #77
mschi772
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I'm using a slightly earlier radiator that has a port in the drivers side tank. I'm not sure what year they stopped doing it, but the aux fan used to be controlled by a thermal switch in the rad tank. I'm using one of those rads and mounting my switch there. In every other way it is an appropriate rad. It is an open system, post-Renix radiator.

You could also use a couple brass fittings and a T to put a switch in the heater hose by the stat housing.

Despite being a fin probe, DC Controls controllers are awesome and not to be dismissed as just another fin probe controller.
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Unread 07-25-2013, 05:30 PM   #78
Newtons3
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I have one temp sensor for the fan on my Cherokee in a second hole I drilled and tapped to 1/8 NPT in my thermostat housing. I have another in a spun aluminum housing halfway up my upper radiator hose in my Wrangler.
http://www.jeepforum.com/forum/attac...1&d=1374791243
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Unread 07-25-2013, 05:34 PM   #79
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Quote:
Originally Posted by Charley3 View Post
What is a Scanguage?
Here is mine reading MAP, TPS, Intake Air Temp, and Coolant Temp.
http://www.jeepforum.com/forum/attac...1&d=1374791685
photo355.jpg  
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Unread 07-25-2013, 06:17 PM   #80
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Quote:
Originally Posted by mschi772 View Post
I'm using a slightly earlier radiator that has a port in the drivers side tank. I'm not sure what year they stopped doing it, but the aux fan used to be controlled by a thermal switch in the rad tank. I'm using one of those rads and mounting my switch there. In every other way it is an appropriate rad. It is post renix and for the open system.

Despite being a fin probe, DC Comtrols controllers are awesome and not to be dismissed as just another fin probe controller.
Is there any possibilty that a radiator switch will show slightly lower readings compared to something in the head or housing?

Our xj is a 96 and it only has the probe in the housing.
I'd guess that non obd2 vehicles had them in the radiator.
Late year thermostat housings are dirt cheap on ebay if you ever wanted to try a sensor in it even if its just to compare temperature and when it kicks in.
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Unread 07-25-2013, 06:22 PM   #81
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Forgot to multiquote.
Quote:
Originally Posted by Newtons3 View Post

Here is mine reading MAP, TPS, Intake Air Temp, and Coolant Temp.
http://www.jeepforum.com/forum/attac...1&d=1374791685
Does that show mpg correctly for your jeep?
Been considering getting one to use in both the xj and our work truck plus my yj once I finish it.

I've been using torque to monitor our jeep since it is obd2 and it reports everything accurately except mpg.
As much as I wish I know I'm not getting 40 mpg cruising and 60 going downhill.
It displays an absurdly low fuel flow number at all times.
Something like 0.5 gph cruising at 40.
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Unread 07-25-2013, 06:34 PM   #82
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Quote:
Originally Posted by ninjakid View Post
Is there any possibilty that a radiator switch will show slightly lower readings compared to something in the head or housing?
Probably, but I'm using a sensor with lower than usual temp cutoffs to compensate for the cooler temp in that tank vs the stat housing.
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Unread 07-25-2013, 06:38 PM   #83
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Others have reported good success with it for MPG reporting. The math is simple so I don't use it for that. I find it much more useful to monitor my engine load and operating parameters. I assume it will do well if you follow the instructions for setting that up and are accurate about it.
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Unread 07-25-2013, 06:40 PM   #84
Newtons3
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Quote:
Originally Posted by ninjakid View Post
Is there any possibilty that a radiator switch will show slightly lower readings compared to something in the head or housing?

Our xj is a 96 and it only has the probe in the housing.
I'd guess that non obd2 vehicles had them in the radiator.
Late year thermostat housings are dirt cheap on ebay if you ever wanted to try a sensor in it even if its just to compare temperature and when it kicks in.
I have run a switch in the radiator (inlet side) several times on different vehicles. I just adjust my sensor for the temp I need. I try to order my radiators with three 1/4" ports in the inlet tank JIC I need them.
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Unread 07-25-2013, 06:53 PM   #85
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Quote:
Originally Posted by ninjakid

Does that show mpg correctly for your jeep?
Been considering getting one to use in both the xj and our work truck plus my yj once I finish it.
I have mine dialed in for mpgs and it's typically close. You have to set your correct speed on the scangauge, if you have re geared or used different tires I think your speedo will be off a few mph. You also have to fill your tank till capacity, meaning until it clicks once. And then run it till about 1/4 remaining, then fill it again. If you put 20 here and 10 there and fill up over here the scangauge won't be accurate. Last time I filled up, I averaged 14.1 mpgs in a 5.2 ZJ 3.5 inch lift and 31's.

Also the scan gauge is able to be used in different cars.
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Unread 07-25-2013, 07:02 PM   #86
wj4play
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Long time ago I read about smokey yuknics 50+ mpg fiero - might want to watch for some ideas

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Unread 07-25-2013, 07:44 PM   #87
Newtons3
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Smokey Yunick is a hero of mine. I studied that Fiero hot air engine and read everything published about it. Don Garlits has it in his Drag Racing Museum in Ocala Florida. When I was there two years ago, the lady in the museum opened it up for me so I could have a peek. You should stop and see it if you're ever in the area. Incidentally, they also have his Octane Motor in the front of the same building. Amazing stuff.
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Unread 07-25-2013, 07:57 PM   #88
Charley3
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Quote:
Originally Posted by ninjakid View Post
Is there any possibilty that a radiator switch will show slightly lower readings compared to something in the head or housing?
Yes. Guaranteed.

Quote:
Originally Posted by mschi772 View Post
Probably, but I'm using a sensor with lower than usual temp cutoffs to compensate for the cooler temp in that tank vs the stat housing.
Another problem with reading temp at radiator is the radiator is the last part of the cooling system to know what the temp is.

Reading at stat housing gives much faster response time for turning on fan when engine gets to hot, IME. That gets the fan on much sooner when things start heating up (like in traffic jam, or off road). It also gets fan shut off sooner after engine cooled back down. So much less temp swings.

---

I base that on have had my Wrangler setup both ways. It had an aftermarket electric fan. For a while I had a pro e in the radiator. It was unsatisfatory. So I had thermostat housing drilled and tapped and installed a screw in sensor for the thermostat housing. Then it worked good. Much faster response times for turning fan on and off. Much less temp swing. With screwin sensor in stat housing it worked as good as my Buick OEM electric fans in my car.

In hind sight, I could have put an XJ stat housing on the Wrangler, instead of drilling and tapping the Wrangler stat housing. However, the screw in sensor in stat housing worked great. I bought the screw in sensor kit from Flexalite.
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Unread 07-25-2013, 08:18 PM   #89
Charley3
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Quote:
Originally Posted by mschi772 View Post
Probably, but I'm using a sensor with lower than usual temp cutoffs to compensate for the cooler temp in that tank vs the stat housing.
That will compensate for temp diff, but not for the lag time. A sensor in stat housing gives much faster response times when fan is needed. IME
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Unread 07-25-2013, 08:21 PM   #90
Charley3
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Quote:
Originally Posted by Newtons3 View Post
Others have reported good success with it for MPG reporting. The math is simple so I don't use it for that. I find it much more useful to monitor my engine load and operating parameters. I assume it will do well if you follow the instructions for setting that up and are accurate about it.
This magic you speak of impresses me. I want one.
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