MPG lower than expected...

tjkj2002 · **Posted:** Fri May 18, 2007 4:56 pm

DarbyWalters wrote:

jcphoto20 wrote:

of course, but all things arent equal, and im getting better mileage in a gasser than you are in a diesel. and with what i know how to modify these things, then i would easily get over 30 if i had one.

WRONG again, you are not getting better mileage than ME in a CRD with your gasser.

He may but he's pushing his KJ half of the way for the better mpg ratings :lol:

.

DarbyWalters · **Posted:** Fri May 18, 2007 6:10 pm

He just doesn't get it...I have had both and the CRD gets better mileage than the 3.7L. OF COURSE driving habits, weight reductions, ect. have something to do with any improvements but he is more interested in being right instead of reasonable.

spencevans · **Posted:** Fri May 18, 2007 6:21 pm

jcphoto20 wrote:

has anyone tried a hotter thermostat? big rigs run those covers over the grill to make them run hotter to get better mileage. wouldnt that same principle work on a CRD?

or how about taking off the engine drivin fan, and only using an electric one once it gets to the point you would want a fan on. that would let it warm faster

im sure something along these lines would help your mileage. and drive like an old guy, it works.

Jcphoto20, This is a friendly family site. I think you need to stop ruffling peoples feathers, esspecially those who put their lives on the line and serve our country, and being condecending toward other won't get you to far in life. Just a reccomendation

jcphoto20 · **Joined:** Sun Nov 19, 2006 1:36 am **Posts:** 507

[quote="DarbyWalters"][quote="jcphoto20"]of course, but all things arent equal, and im getting better mileage in a gasser than you are in a diesel. and with what i know how to modify these things, then i would easily get over 30 if i had one.[/quote]

WRONG again, you are not getting better mileage than ME in a CRD with your gasser.[/quote]

you are wrong, since i wasnt talking to you.

jcphoto20 · **Joined:** Sun Nov 19, 2006 1:36 am **Posts:** 507

[quote="DarbyWalters"]He just doesn't get it...I have had both and the CRD gets better mileage than the 3.7L. OF COURSE driving habits, weight reductions, ect. have something to do with any improvements but he is more interested in being right instead of reasonable.[/quote]

there was no matter of "getting it" and duh, of course your crd gets better than your gasser. but like i was saying i get better in my gasser than you get in your CRD. that was my only point and a big WHATEVER, to the jarhead.

jcphoto20 · **Joined:** Sun Nov 19, 2006 1:36 am **Posts:** 507

[quote="spencevans"][quote="jcphoto20"]has anyone tried a hotter thermostat? big rigs run those covers over the grill to make them run hotter to get better mileage. wouldnt that same principle work on a CRD?

or how about taking off the engine drivin fan, and only using an electric one once it gets to the point you would want a fan on. that would let it warm faster

im sure something along these lines would help your mileage. and drive like an old guy, it works.[/quote]

Jcphoto20, This is a friendly family site. I think you need to stop ruffling peoples feathers, esspecially those who put their lives on the line and serve our country, and being condecending toward other won't get you to far in life. Just a reccomendation[/quote]

thank you so much for your off topic social recommendations. i put my life on the line exactly like all of them did for over 15 years, so i dont really care what your opinion is. i earned the right to have and voice mine like everyone else in this country that i defended with MY life so very long.

anyways, how about the ON TOPIC things i suggested, anyone?

tjkj2002 · **Posted:** Fri May 18, 2007 8:56 pm

jcphoto20 wrote:

has anyone tried a hotter thermostat? big rigs run those covers over the grill to make them run hotter to get better mileage. wouldnt that same principle work on a CRD?

or how about taking off the engine drivin fan, and only using an electric one once it gets to the point you would want a fan on. that would let it warm faster

im sure something along these lines would help your mileage. and drive like an old guy, it works.

The big rigs only run those covers in the winter time to allow the engine to warm up to operating temp faster.A higher degree thermostat will not help,it will actually decrease power and MPG's on a diesel and shoten the engines life.Diesels are harder to maintain a stable temp in so the mechanical fan is a must,the electric fan is for a back up and for low speed driving.I work on big deisels and they run alot better when they are keeped between 170 degrees and 190 degrees.The up armored Hummers run at 240 degrees and they have alsorts of problems,no start when warmed up,engines only last for maybe 1000-2000 miles,overheates the trannies and PS systems(which powers the brakes,engine fan to).Get warm and keep under 200 degrees for best results.

jcphoto20 · **Joined:** Sun Nov 19, 2006 1:36 am **Posts:** 507

[quote="tjkj2002"][quote="jcphoto20"]has anyone tried a hotter thermostat? big rigs run those covers over the grill to make them run hotter to get better mileage. wouldnt that same principle work on a CRD?

or how about taking off the engine drivin fan, and only using an electric one once it gets to the point you would want a fan on. that would let it warm faster

im sure something along these lines would help your mileage. and drive like an old guy, it works.[/quote]The big rigs only run those covers in the winter time to allow the engine to warm up to operating temp faster.A higher degree thermostat will not help,it will actually decrease power and MPG's on a diesel and shoten the engines life.Diesels are harder to maintain a stable temp in so the mechanical fan is a must,the electric fan is for a back up and for low speed driving.I work on big deisels and they run alot better when they are keeped between 170 degrees and 190 degrees.The up armored Hummers run at 240 degrees and they have alsorts of problems,no start when warmed up,engines only last for maybe 1000-2000 miles,overheates the trannies and PS systems(which powers the brakes,engine fan to).Get warm and keep under 200 degrees for best results.[/quote]

awesome, thanks for the great info

onthehunt · **Posted:** Fri May 18, 2007 9:36 pm

jcphoto20- what's with the attiutde? Don't come on this site half-cocked. Way too many people here that know b.s. when they hear it. If you get 25mpg with your gasser good for you. I get that with my crd without pulling the fan,running a shutter or any other pita mod. I just drive mine- no grandpa needed. Go hook up a trailer and come back to brag about your mpg.

Jimbob · **Joined:** Thu Nov 02, 2006 11:05 pm **Posts:** 160

I get near 30 on the highway with 13K on the odometer. Around town I get 22 as advertised, doesnt sound great but this is real world. A great relief compared to my 1999 4.0L Wrangler! (difference practically accounts for the payment). Parents gaser 16 around town, 20 on the highway.

Diesel runs a little higher than gasoline in the winter but usually less than gas in the summer (vacation driving) so it usually works out in favor of the diesel economically.

jcphoto20 · **Joined:** Sun Nov 19, 2006 1:36 am **Posts:** 507

[quote="onthehunt"]jcphoto20- what's with the attiutde? Don't come on this site half-cocked. Way too many people here that know b.s. when they hear it. If you get 25mpg with your gasser good for you. I get that with my crd without pulling the fan,running a shutter or any other pita mod. I just drive mine- no grandpa needed. Go hook up a trailer and come back to brag about your mpg.[/quote]

i didnt have an attitude. and thanks for the "good for you" i feel the same way. and i dont tow, so it doesnt really matter. have fun driving.

spencevans · **Posted:** Sat May 19, 2007 3:46 am

Hey, how about those lower than expected MPG!!!

Let's keep this thread rollin'.

:-)r

RFCRD · **Posted:** Sat May 19, 2007 7:07 am

tjkj2002 wrote:

jcphoto20 wrote:

has anyone tried a hotter thermostat? big rigs run those covers over the grill to make them run hotter to get better mileage. wouldnt that same principle work on a CRD?

or how about taking off the engine drivin fan, and only using an electric one once it gets to the point you would want a fan on. that would let it warm faster

im sure something along these lines would help your mileage. and drive like an old guy, it works.

The big rigs only run those covers in the winter time to allow the engine to warm up to operating temp faster.A higher degree thermostat will not help,it will actually decrease power and MPG's on a diesel and shoten the engines life.Diesels are harder to maintain a stable temp in so the mechanical fan is a must,the electric fan is for a back up and for low speed driving.I work on big deisels and they run alot better when they are keeped between 170 degrees and 190 degrees.

Can both agree and disagree. I have read studies done by Detroit Diesel where they found optimum (for burn efficiency)water temp to be 193*F. That said, the CRD (atleast the one I had) is configured to run way too cold for optimum burn in air temps under about 45*F and drops off badly under 30*F.

Last winter, I installed blocking plates behind the grill and got a noticable bump in both fuel economy and heater output. I had those plates (which blocked @80% of the air through the grill) in while cruising highway speeds in air temps up to the mid-50's*F without even a hint of abnormal temps on the factory gauges or any overheating. This would strongly indicate DCX used a cold theromstat or has another engineering issue such as over-chilling the charged air or some combined factor of both. Would try this approach before changing to a hotter thermostat (if you can find one).

tjkj2002 · **Posted:** Sat May 19, 2007 7:18 am

RFCRD wrote:

tjkj2002 wrote:

jcphoto20 wrote:

has anyone tried a hotter thermostat? big rigs run those covers over the grill to make them run hotter to get better mileage. wouldnt that same principle work on a CRD?

or how about taking off the engine drivin fan, and only using an electric one once it gets to the point you would want a fan on. that would let it warm faster

im sure something along these lines would help your mileage. and drive like an old guy, it works.

The big rigs only run those covers in the winter time to allow the engine to warm up to operating temp faster.A higher degree thermostat will not help,it will actually decrease power and MPG's on a diesel and shoten the engines life.Diesels are harder to maintain a stable temp in so the mechanical fan is a must,the electric fan is for a back up and for low speed driving.I work on big deisels and they run alot better when they are keeped between 170 degrees and 190 degrees.

Can both agree and disagree. I have read studies done by Detroit Diesel where they found optimum (for burn efficiency)water temp to be 193*F. That said, the CRD (atleast the one I had) is configured to run way too cold for optimum burn in air temps under about 45*F and drops off badly under 30*F.

Last winter, I installed blocking plates behind the grill and got a noticable bump in both fuel economy and heater output. I had those plates (which blocked @80% of the air through the grill) in while cruising highway speeds in air temps up to the mid-50's*F without even a hint of abnormal temps on the factory gauges or any overheating. This would strongly indicate DCX used a cold theromstat or has another engineering issue such as over-chilling the charged air or some combined factor of both. Would try this approach before changing to a hotter thermostat (if you can find one).

Yeah putting those winter fronts on will help in lower temps but you would not want to run them with the temps above 60 degrees.Also remember that the CRD's have a alloy head and heating up the engine past 190 while running hard or towing will also increase your EGT's and could play havok with the alloy head.Detroits/Cummins is mainly what I work on,I love those 8V92TA's,they are some powerhouses!

RFCRD · **Posted:** Sat May 19, 2007 8:15 am

tjkj2002 wrote:

Yeah putting those winter fronts on will help in lower temps but you would not want to run them with the temps above 60 degrees.Also remember that the CRD's have a alloy head and heating up the engine past 190 while running hard or towing will also increase your EGT's and could play havok with the alloy head.Detroits/Cummins is mainly what I work on,I love those 8V92TA's,they are some powerhouses!

Well, I use the term "Series 92 Roulette" when it comes to bus engines. They make a lot of power, just don't stand too close to that 8V92 when it decides to grenade. Had an empty bank account and garage full of scrap iron to prove it.

Interesting that a Series 92 maintains engine temps better than most 4-cycle. In a bus application, 6V92 or 8V92 DDEC uses 190* thermostats and the radiator shutters open at 195*. In cold weather, I prefer a Series 92 because it can throw enough extra heat to keep the coach warm without using auxillary heaters. Now, just finding a way to keep the rods in the block.....

Just a gut feeling DCX is having a difficult time balancing low combustion temps for NOx emissions and high enough EGT's to burn off the oils & soot. They are running it at less than optimum burn temps to control NOx and thus not getting use of all the power in the fuel. That is why fuel economy drops so badly at the hint of cold weather. Kill the EGR and get combutions temps up and you can easily see mpg's in the 30+ range from this engine in a Jeep.

Ripster · **Posted:** Sat May 19, 2007 8:27 am

I would have to agree somewhat as my unscientific tests show this. Ran covers up to 40 degrees and never
dropped below 24 mpg during the winter. Last 2000 mile trip this month with EGR off and I was consistantly 28 mpg at
70-75 and when driving with a tailwind at 60-65 finally worked up to 31mpg by the end of the trip and an
easy throttle. Confirmed by hand calculations also.

BiodieselJeep.com · **Posted:** Sat May 19, 2007 10:15 am

Jeep4Ever:

Just thought of something: what are your RPMS at 65? Should be just shy of 2000 rpm. Some guys reported that they can't get the overdrive gear until they pop up to mid-sixties... maybe if you are easing up to 65 and you have one of those tighter trannies, you are in a lower gear and in the 2500rpm range?

Wild shot, but thought of it. Hope that you see continued improvement.

Oh, also have you calibrated your odometer with "reality"? a lot of guys are reporting as much as 10% error on the odo. find some mile-markers or use a GPS and double-check.

Jeep4ever617 · **Posted:** Sat May 19, 2007 4:13 pm

I have about 43000 miles on my KJ...the air filter is spotless...and at 65mph the RPMs run at about 18 or 1900.

chadhargis · **Posted:** Sat May 19, 2007 5:59 pm

Well, I was pleasantly surprised today.

I've been getting about 20-21mpg with my daily commute. Today, I filled up and low and behold...I raked in 23.3mpg. That's around town driving only. I think that's awesome for an SUV.

I'm heading out for a 1000+ trip tomorrow, so I'll see what I get on the interstate. I believe, without a doubt, that I can get over 500 miles on a tank on the interstate.

This thing just keeps getting better and better.

To make things better...regular unleaded was $3.09...#2 Diesel was $2.85. Sweet!!

tjkj2002 · **Posted:** Sat May 19, 2007 10:58 pm

Quote:

Well, I use the term "Series 92 Roulette" when it comes to bus engines. They make a lot of power, just don't stand too close to that 8V92 when it decides to grenade.

Had many run away on me,that really sucks.Had one go so bad it ran for 45 min with a rubber/metal plate over the turbo intake,all fuel line cut,and the fuel rods pushed in.The whole time I was standing on top of the engine(mounted in a Marine Corps LVS) until it started on fire.The fire fighters pumped water in the turbo for a full min before it blew itself into about 50 pieces :shock:

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MPG lower than expected...

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