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Unread 07-25-2013, 08:37 AM   #61
Azzy
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Quote:
Originally Posted by Newtons3 View Post
I check fuel mileage religiously on every vehicle I drive. It's a bit of an OCD for me. That said I always hate to quote a single tank. I have never found that ambient temperature of the fuel when I fill up makes any noticeable, trackable difference. In our state, the pumps are tested and regulated and you can be assured of their accuracy. The tolerance between pumps is negligible. Unless I've made some change to one of my Jeeps, the biggest factors affecting my fuel economy are average speed, air temp, a/c duty cycle, and humidity. Methanol as an oxygenate factors in, but that's purely mathematical.

Its been way back in the thread, but I wanted to comment on this. Fuel temps generally stay the same, since they are stored underground, well below the frost line. Us motorcycle guys always know that a fresh filled tank helps cool off the ... legs.... on a hot day. (then again, that might be from pumping too.. dunno)

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Unread 07-25-2013, 09:58 AM   #62
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Quote:
Originally Posted by Azzy View Post
Its been way back in the thread, but I wanted to comment on this. Fuel temps generally stay the same, since they are stored underground, well below the frost line. Us motorcycle guys always know that a fresh filled tank helps cool off the ... legs.... on a hot day. (then again, that might be from pumping too.. dunno)
Frost....? Unfamiliar. No frost in South Louisiana.
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Unread 07-25-2013, 12:48 PM   #63
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Originally Posted by Kevin108 View Post
I just got a new ScanGauge II a couple weeks ago. When I get my XJ back together, I'll unload all the tools from the back and see just what kind of mileage I can shake out of it. The best I ever did was 21 mpg stock on a 3-hour interstate run. I'll set my goal at 18 mpg.
What is a Scanguage?

21 mpg is respectable for a stock XJ. Though it could get 23 or 24 mpg just from changing to a Gates 205F thermostat.
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Unread 07-25-2013, 12:54 PM   #64
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Newtons3, I don't have the nerve to use a 215F stat, but I might (in future) try a 210F stat with aftermarket electric fans than I can set to come on at 220F.

So if you could help me find a 210F that would be great.

However, Stant stats are known to open 5F sooner than stated temp. So a 215F Stant would be a 210F.

---

For now, as long as I have stock fans, I'll keep using the Gates 205F, which seems to really be a 208F.

Edited in Later: I have learned that a 205F Motorad 200-205 fits 4L Jeep engine and starts opening at 208F to 210F. So that's real close to being a 210F stat. I'm going to buy one at Oreillys.
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Unread 07-25-2013, 01:01 PM   #65
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Want gas mileage? Go buy a Prius and be happy.
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Unread 07-25-2013, 01:03 PM   #66
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Want gas mileage? Go buy a Prius and be happy.
Someone didn't read the thread :thumbs down:
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Unread 07-25-2013, 01:05 PM   #67
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How much more money are you going to through at it before you decide just to buy more gas?
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Unread 07-25-2013, 01:15 PM   #68
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I've read the thread, just sayin. Regear, belly pans, aerodynamic changes, body mods, how much does that cost?
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Unread 07-25-2013, 01:22 PM   #69
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Quote:
Originally Posted by Charley3

What is a Scanguage?
It's a little scanner that plugs into your obd2 port. It tracks lots of stuff like fuel economy, horse power, voltage, coolant temp, typical stuff monitored by your obd system. I have it in my ZJ and I love it! They make cheaper versions but I think the scangauge 2 is the best one on the market.

If you get it and have questions let me know.
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Unread 07-25-2013, 01:29 PM   #70
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Originally Posted by StreckXJ View Post
So, if the fuel consumption comes from the mechanical fans turning as commanded by the thermostat....wouldn't the better choice be to go to electric fans rather than have the engine run at higher temps? There has to be a long (or maybe even medium) term trade off for running at higher temps for longer periods of time.
Fuel consumption from mechanical fan comes from two things, it's turning all the time, even when not needed. In my climate it's only needed when driving slow on hot summer days. The rest of the time, not needed.

The fuel consumption issue with a mechanical fan is that it's always cooling the engine to some extent, making it more difficult to get to full op temp on cold days, especially in Winter.

===

An electric fan only comes on when needed. This solving both of the problems with a mechanical fan. The electric fans in my Buick only come on on the hottest days of the year when driving slow. Same deal when I had an aftermarket electric fan in a Wrangler.

Also, an electric fan's temp sensor can be configured to make fan come on at the temp I choose. Thus offering more control over engine temps.

===

There is absolutely no risk to engine from running a 205F stat instead of a stock 195F stat. I did this for 6 years and 30K miles on a Wrangler with no problems at all. I have been doing this for 40K miles on my Buick with no problems at all.

The 205F Gates stat I like are really 208F stats, IME. They work great. The engine is more efficient and plugs, valves, and oil stays cleaner. Op temps are 208 to 210F, unless driving slowly uphill on a hot day, in which case temp gets to 215F and then electric fan turns on and temp drops back to 210F. Same for my LJ, XJ, and Buick.

That gives 2.5 to 3 mpg more. No downside at all.

===

The potentially risky stuff is what the hardcore hypermilers-economodders do, which is put the hottest thermostats made, like 215F, 217F, or maybe hotter than that if they can find them. Then their electric fans are configured to turn on at 5F to 10F hotter than stat. So they are running 215F to 220F for the more conservative economodders, or 220F to 225F for the more aggressive economodders. Combined with electric fans that gives great fuel economy, but may or may not harm engine over time. I'm not sure if it would harm the engine, but I'm afraid to find out.

===

My local Napa certified mechanic says engines can run at 230F all the time and not be harmed if they have good oil and a perfect cooling system that won't ever allow above 230F, BUT he says that it's not wise to run at 230F because there is no margin for error. He suggest running at 215F or less to be safe.

===

With my Gates 205F stat (really a 208F IME) I am running 208F to 210F most of the time. It occasionally gets to 215F (on a hot day driving slowly uphill) and then the stock electric fan comes on and quickly cools it down to 210F. That is perfectly safe and pretty darn good for fuel economy and having a clean engine.

===

Bottom Line of Temps:

If you want to try a little economodding on a Jeep 4L, start by getting a 205F Gates 33010 thermostat from RockAuto.com. It's safe and effective and works well with the XJ (or TJ) stock mechanical and electric fans (though it'd work even better with no mechanical fan). This is what I'm doing. I think my engine will last LONGER this way because it's cleaner.

If you want to be a hardcore economodder and are willing to take some potential risks, get a 215F stat, IMO. I wouldn't recommend hotter than 215F to anyone. If you do have a 215F stat, you'll need aftermarket electric fan(s) that are set to come on at 220F, IMO. After careful consideration, I'm not going this hardcore route, but there are economodders with Jeeps who are doing this with great success so far. I say "so far" because it remains to be seen if their engines will last.
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Unread 07-25-2013, 01:34 PM   #71
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Quote:
Originally Posted by blackcar87 View Post
I've read the thread, just sayin. Regear, belly pans, aerodynamic changes, body mods, how much does that cost?
This one person spent less than 400 (think it was less but dunno) creating a front skid made of either plastic or corrugated metal, belly pan from plastic iirc, filling in gaps between panels and stuff plus other little tweaks to improve airflow and he gets 26 highway.
Unless you crawl underneath it looks the same as a stock Cherokee.
Worth it to me.
I'd love to be able to go more than 400 miles on a single tank.
Sure it takes some engineering and planning but it is very much worth the time and effort to me since I do a lot of highway driving.
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Unread 07-25-2013, 01:38 PM   #72
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I've read the thread, just sayin. Regear, belly pans, aerodynamic changes, body mods, how much does that cost?
Really? The same argument could be made for almost any mod. Read the post. Then reread it. We are discussing economy and efficiency mods not personal financial planning. My 15x10 Sidebiters are not wholly necessary, neither are strippers and beer. But.... Ive spent money on all 3 and feel better for it.
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Unread 07-25-2013, 02:06 PM   #73
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Originally Posted by blackcar87 View Post
How much more money are you going to through at it before you decide just to buy more gas?
How much more gas money are you going to flush down the tank before you do a few cheap mods that will improve your fuel economy?

===

So far I have spent very little that didn't need to be done anyway for a tune up and/or to increase power.

The only extras (beyond a tune up) so far are AFE high flow intake (around $300) that benefits power and fuel economy, and a $5 thermostat.

My highway fuel economy went from 16 to 22 mpg. That is cost effective and will pay for itself within a year. Much of that gain was from the $5 thermostat.

I have talked about doing some expensive economods, but so far haven't done anything expensive. I am prioritizing doing cheap mods first.

Next will probably be $150 for Dodge Neon or Ford fuel injectors. Still not expensive.

A few cheap mods can get you to 23 mpg highway (with 30 x 9.5 R15). Then comes the expensive mod of replacing stock mechanical fan, but then you're at around 25 mpg. That's all safe, conservative ecomodder stuff and operating at 208 to 210F (safe).

===

Replacing mechanical fan won't be cheap or easy, but will probably get me to 25 mpg (after doing all those ^ cheap mods), and it'd help power too.

I can then probably get 26 mpg by adding high flow exhaust.

Those ^ are all safe conservative ecomods, and most of them don't cost much. If we then went into the more hardcore, expensive or riskier mods, then I think it could exceed 26 mpg, but might not be worth expense (expensive mods) or risk (running hotter than 215F).

---

You can safely, easily, and cheaply get to 23 mpg (30x9.5R15 AT tires). Running 208 to 210F. This is safe for engine. This approx wbere I am now.

You can safely get to 26 mpg without doing anything risky, but will have to part with more money. Running 208F to 210F. This is safe for engine. This is where I intend to go.

You can get even higher mpg by spending more money and taking some potential risk (215 stat and all electric fans that come on at 220F). Running 215F to 220F. This might be safe for engine, but I'm not sure. Hardcore ecomodders do it. I'm reluctant to run that hot.

===

There is also the satisfaction of personal accomplishment and laughing at nay sayers after doing what they say can't be done.
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Unread 07-25-2013, 02:22 PM   #74
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I almost forgot, Newtons3, or someone, posted earlier about the suckiness of radiator temp probes for aftermarket electric fans.

I concur. Radiator temp probes suck.

When I upgraded my LJ to a Flexalite electric fan, I bought a special kit from them that had a screw in probe for the engine block or the thermostat housing.

A hole was drilled into the thermostat housing, and the hole tapped to put threads in it, and then the sensor probe was screwed into the thermostat housing. This worked good.

Not sure exactly how I'd have an XJ aftermarket electric fan (to replace mechanical fan) set up for a temp sensor probe, but it definitely wouldn't be a radiator probe.
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Unread 07-25-2013, 02:40 PM   #75
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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.
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