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-   -   My goal is to get 25+ mpg from my 99 XJ with 30 x 9.5 R15 ATs (https://www.jeepforum.com/forum/f11/my-goal-get-25-mpg-my-99-xj-30-x-9-5-r15-ats-1551782/)

Charley3 07-22-2013 10:44 PM

Quote:

Originally Posted by mschi772 (Post 15706932)
Not that it's throwing your MPG estimates wildly out of whack, but if you can fill-up at the same pump at the same time of day, your calculations will be more accurate. Pumps vary, orientation of the vehicle at a given pump can alter when "full" happens, and temperatures can affect the volume of fuel that actually gets delivered per gallon (cooler mornings means denser fuel which means more bang for your buck).

I will make sure that I follow those suggestions.

Charley3 07-22-2013 10:46 PM

Quote:

Originally Posted by MountainMan864 (Post 15707229)
Take backseat out and all bumpers off too.

I'm not willing to reduce functionality.

Charley3 07-22-2013 10:52 PM

25+ mpg highway seems a realistic goal, considering that I'm already at 22 mpg and still have several mods yet to do. Best of all, my mods so far have slightly increased torque and HP. It pulls up hills easier now.

My goal is to increase fuel economy without reducing performance or functionality, and do this with 30 x 9.5 R15 AT tires. So far so good. Still working on it.

Charley3 07-22-2013 11:16 PM

I think I'll replace fuel injectors next because doesn't cost much to do. Haven't decided yet whether to try Ford or Dodge injectors.

Next after that will be Flex-a-Lite twin elecric cooling fans to replace stock fans.

Next after that will be high flow exhaust.

Maybe a new coil.

I think it'll get better than 25 mpg after those mods (and more torque and HP too!)

mudpen 07-23-2013 01:47 AM

Whats your gearing ratio 3.55 ? if you change that to 3.07, that should drop
your rpms some. Kinda sucks going uphill though

Charley3 07-23-2013 11:18 AM

Quote:

Originally Posted by mudpen (Post 15707915)
Whats your gearing ratio 3.55 ? if you change that to 3.07, that should drop
your rpms some. Kinda sucks going uphill though

To many hills and mountains here. I don't think 3.07 would be good for me. To bad my XJ auto tranny doesn't have 5 gears.

Charley3 07-23-2013 11:35 AM

I've been lurking at a hypermiler forum and learned some general engine info and some info specific to 4L Jeeps.

The hypermilers say this is true with all gas engines, and specifically they mentioned 4L Jeep engines (cause one of the hypermilers owns a 4L Jeep): The single most important mod, and one of the cheapest, is get the hottest thermostat you can find.

A 205F Gates 33010 thermostat from RockAuto.com was the hottest I could find for 4L Jeep engine. I would have preferred 210F if I could have found one. Anyone know if I can get a 210F stat for a 4L engine?

Edited in Later: I have learned that the 205F ACDelco 12T1F and 205F Motorad 200-205 are the SAME thermostat and open at 208F to 210F. i.e. - are really a 208F to 210F stat, which is perfect for my moderate to cold climate.

Some hypermilers say a 4L Jeep is most fuel efficient when running at 215F to 220F (measured at thermostat housing). I disagee.

I think 205F to 213F (measured at thermostat housing) is most efficient for Jeep 4L engines.

Mine is running at 208F to 210F most of tbe time this Summer (if dash guage can beleived). Almost ideal in Summer, but won't be warm enough in Fall, Winter, or Spring.

My stock auxilliary electric fan comes on at 215F and quickly cools engine down to 210F. Then fan goes off.

BTW - I'm using Mobil One 0/40 synthetic. I have no fears about running warm. It won't hurt the engine. It's good for engine because plugs, valves, and oil stay cleaner when engine runs warm.

ninjakid 07-23-2013 12:32 PM

I'd stick with a 195 even if the engine runs better at 220.


I don't know anything about your xj so I don't know if you have one or not but at the very least I'd recommend a external transmission cooler tied into the cooling system if you use a 205 thermostat.
AW4's do not like getting real hot and when they overheat they start belching fluid out the vent onto the exhaust.

mschi772 07-23-2013 12:37 PM

65 Attachment(s)
Quote:

Originally Posted by mudpen
Whats your gearing ratio 3.55 ? if you change that to 3.07, that should drop
your rpms some. Kinda sucks going uphill though

Lower RPM isn't always better. There is an efficiency sweet spot for every engine, and without spending a ton of time explaining the math and physics of it (which can be found online like everything else), our 4.0s run most efficiently somewhere in the 2300 +/- 200 range.

I'll trust your research about efficient temps, but I will agree that you should cool your tranny. They don't like getting hot at all.

Charley3 07-23-2013 12:39 PM

Quote:

Originally Posted by ninjakid (Post 15709557)
I'd stick with a 195 even if the engine runs better at 220.


I don't know anything about your xj so I don't know if you have one or not but at the very least I'd recommend a external transmission cooler tied into the cooling system if you use a 205 thermostat.
AW4's do not like getting real hot and when they overheat they start belching fluid out the vent onto the exhaust.

I have a stock tow package auxilliary tranny cooler. My engine with 205F stat is running at 208 to 210F (if dash guage can be believed) in Summer in my moderate climate. Working good.

Newtons3 07-23-2013 01:02 PM

I 215 and a 217 (rated). One of them fit a GM application and the 4.0. Ill try to find it and get part number for you. Just out of curiosity, why 5-40 and not 0 or 5w- 20 or 30?

Charley3 07-23-2013 02:44 PM

Quote:

Originally Posted by mschi772 (Post 15709580)
Lower RPM isn't always better. There is an efficiency sweet spot for every engine.

Yes. I'm already in the sweet spot for driving on the level. For steep hills I pull shifter to 3rd and then in sweet spot for hills.

My gearing is already ideal for economy, IMO.

The only thing I don't like about my gearing is its to high and struggles when in reverse backing up a steep hill. Otherwise 3.55 gearing is great. On the low rpm end of the sweet range.

I think 3.73 would be better. Probably similar gas mileage and better performance (with 30" tires).

Newtons3 07-23-2013 05:29 PM

The thermostat may take a while. We used to run one in an old pre-Vortec Chevrolet engine run on propane, but that's a dinosaur to us. I've got to find my old parts book and hunt it down. Check the late 90's 4G64 Mitsubishi engines; Talon; Eclipse; etc. They ran them in some automotive applications.

I'm not going to tell you not to run a fan controller. Just hear the frustration in my experience and judge for yourself. I believe I have run every probe-type controller on the market over the years and they are all disappointing at best and dangerous at worst (shorting out, fires, etc.). In the last three years I have run four PWM controllers including two series from SPAL, who I consider to be the leader in electric cooling. The SPAL performed the best.... initially. All four failed; and never at a good time. What I have learned is that the PWM controllers for fan speeds are overrated. If you need to cool your radiator, turn the fans on. If not leave them off.

I now run two Bosch relays, one to turn on the fans (75A), and one to interlock/isolate the A/C circuit. Flawless and simple. The best part is I run a fan switch and changing my cut-in temp. is as easy as changing that switch. I'm currently running either a 205 or a 210 AFCO. I don't remember which. It would be easy enough, especially on a Cherokee (read- this is how my Cherokee is getting wired) to run two power relays. One for two fans and one for the third. I will be staging mine with a two stage switch from a mid 80's Pontiac. The secondary cut-in would be at 235 with the primary at (don't quote this- it's been a while) 210-215.

As a diesel mechanic, I question your claim of hot running diesels and your methodology for picking oil viscosity as well as the statement about syn/dino as it relates to oil pressure. However, I do think you are doing better than many.

mschi772 07-23-2013 06:33 PM

65 Attachment(s)
Quote:

Originally Posted by Newtons3 (Post 15709702)
Just out of curiosity, why 5-40 and not 0 or 5w- 20 or 30?

Indeed, you seem quite attached to that 5-40 Mobil 1, but all my oil research shows the 4.0 having rather bad UOAs (especially iron wear) from Mobil 1 EXCEPT the synthetic 0-40. M1's syn 0-40 is a great oil, up there with German (yeah, you have to check the back of the bottle for "Made in Germany" because the same oil in name made elsewhere is different) Castrol syn 0-30 and Shell Rotella T6 5-40. I know I'm splitting hairs, but if I have to spend money on oil, I figure I might as well spend it where my money is best spent. Mobil 1's high mileage and Delvac blends do get honorable mention, and because it's hard to stay perfectly up-to-date with my research, they may be solid contenders as well.

Lots of guys run these oils, but I'm trying to get away from running thicker oils. Lubrication comes from FLOW, and a thinner oil will require less energy to pump and will flow better thus providing an MPG boost and necessary protection. Don't even get me started on how most people are wrong about how they THINK they understand the Xw-YY numbers on oil. Yeah, Charley, you seem to be a little "off" with your understanding of what those numbers really mean, too. The short explanation is this:
Quote:

In a 10w-30, the 10w part (W stands for winter not weight!) and signifies a certain maximum viscosity/flow at low temperature; the lower the number, the better its winter and cold start performance. Again, the first number is just an index, not a strict viscosity rating like so many people think.

The 30 corresponds to certain viscosity limits at 100 deg C. These are fixed limits and all oils of a given rating must perform within that rating's limits. Because the limits form a range/window, there is some variation in viscosity even at 100 deg C from one oil to another, and there are NO standards set for how an oil will perform/change during all the temps above or below that temp. The lower the number the thinner the oil at 100 deg C.
The oils above are great for the 4.0, but not because of their viscosity, and the misconception that lots of Jeepers have that heavier oils are better in the 4.0 has been debunked quite well. All other things being equal, a 40 is not any better in a 4.0 than a 30. There is no significant benefit from the thicker viscosity. Even the Castrol is a pretty thick oil--nearly worthy of being called a 40, and it practically IS in some ways. A lower viscosity oil (I'm not sure how I feel about going below 30 in a 4.0, though) can help MPG, and as such, my search for a lighter quality oil continues. I'm currently using Rotella T6 but will try German Castrol 0-30 if I can ever find it. If I never find another really great 30 oil and have to keep using T6, GC 0-30, or M1 0-40 for the rest of my days, I'm OK with that.

Charley, given your affinity for your Mobil 1, I highly recommend you at least consider switching to Mobil 1 synthetic (may also be labeled as Euro blend) 0w-40. Superb oil, and if you do a little Google-fu, you'll see confirmation of my recommendation. Yeah hair-splitting, but if we're nit-picking, why not split all the hairs, right?

P.S. Anytime I bring-up oil, some numb-nuts chimes-in about our flat-tappet cam and zinc/ZDP/ZDDP. To that person, I say read this: http://www.steelsoldiers.com/showthr...nd-ZDP-content Some oils are good, and some are bad. Do your research and use a good oil, but don't go out and buy oils jacked-up with zinc or add a ZDP additive just because of some myth you heard about once upon a time.
It is an excerpt from SAE document #2004-01-2986 which can be found in full here: http://papers.sae.org/2004-01-2986/

P.P.S. If you want superb, customizable control over electric fans without having to control them manually all the time (good to have a manual on/off though), get a fan controller from DC Controls. The end.

Newtons3 07-24-2013 04:57 AM

Again, well said mschi772. Thats one of the best written summaries of oil viscosity ratings Ive seen. Like you, every time I post similar, out come the nuts who believe all the myths and conjecture. Ive read all the studies about ZDDP but the reality is that except for some EXTREME cases of aggressive lobes and very high spring rates or maybe (maybe) a case or two of prolonged idling, the cams that Ive seen fail over the years had nothing to do with Zinc and Phosphorous. Its always been poor metal, design, alignment, or oiling in general.


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