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Unread 10-04-2006, 08:44 PM   #1
David Hinton
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would a diesle get a significant gain in mpg?

Would we see a large gain in mpg for the diesle even though it is much heavier and the overpriced diesle gas prices?

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Unread 10-04-2006, 08:52 PM   #2
Laxstar46
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on the highway yes. but other than that only a few mpg. the big reason for the diesel is the power. Diesel engines make great torque at low rpm. the diesel 3.0 crd that would most likely go into the jk makes 367 ft lb's of torque at 1800 rpm
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Unread 10-04-2006, 10:30 PM   #3
David Hinton
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is it likley that we will see a diesle in 2008?? How do we really know?
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Unread 10-04-2006, 10:37 PM   #4
David Hinton
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also, would the higher gas price for diesle equal out to the mpg of the v6 but the lower pas prices, so the overall price of fueling for the same amount of fuel used be the same?
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Unread 10-04-2006, 10:40 PM   #5
Laxstar46
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No one really knows for sure. but jeep has had quite a fair share of hardcore jeepers complain about the 3.8 v6 and rumors say they are planing for a better engine to please more ppl. In all honesty the 3.8 V6 is a fine engine. at least till all the bugs are worked out. The v6 makes good torque and Hp. the only problem that hardcore jeepers like me that will offroad our rigs is where the engine makes the torque. I believe motor trend said that the 3.8 makes 235 ft lb's torque at 5000 rpm or somewhere near that. which is a very high rpm for off roading meaning that when ur just crawlin up a hill ur not getting that good of torque in the low range. This is what was so great about the 4.0L it had almost 240 ft lbs torque and almost all was available at idle. making the engine very good for off road purposes. i really don't have any problems with the v6 yet. Even tho it makes its peak torque at a high rpm it may still have good torque in the low range yet. that's why i really want to see a dyno with the torque curve of the v6 b4 i pass judgement. If i go to test drive a 3.8 rubi and it displays a good low end torque while still having a great high end then i would have no problem purchasing it. but still there are lotsa rumores about oil, water leaks and electrical glitches. all common in a first year vehicle. So if i would get a new rubi i would wait till a year or so till the bugs are worked out. byt then hopefullya diesel or small block v8 is available. With the torque curves it is not the peak value it is the area under the curve that is most important. Kinda like if you can find the equation for the torque curve on the v6 and I6 then find the definate integral from what say 1000 rpm to 5000 rpm that will give you the area under the curve.
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Unread 10-04-2006, 10:51 PM   #6
Bgeddes
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We have an '05 KJ Diesel, a few coworkers have '05 gas KJs.

We get 23-24 in town (in the mountains) and right at 30 highway.
Gassers get 15 in town and 20 on the highway.

The CRD option was ~$1800. With the high gas prices, regular gas was $0.20 less than Diesel, we have just about paid for the option. Now the price difference is more like $0.40. Because we get 150% of the miles for 120% of the price, we still gain.

The VM Motori engine used in the Jeep Diesels is TINY. I would easily fit into an early CJ5. It's shorter than the Dauntless. Some day our CRD will power a Wrangler of some sort.

A few quick specs, 2.8L, turbo charged, intercooled, 4cyl. About 165hp, about 300 ft/lbs. Compare that to a 258 or 4.0, and see how the little mill fares.

I can make fuel for my Diesel in my backyard, can you make gasoline at home?
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Unread 10-04-2006, 10:57 PM   #7
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^^^^^ gotta love diesels. so much power at such low rpm. the offroaders dream
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Unread 10-04-2006, 11:02 PM   #8
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I forgot to add we are 380 lbs heavier with our CRD than the gassers. Same scale, same time.
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Unread 10-05-2006, 01:35 AM   #9
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YES!

Diesels are NOT sold for power or low end torque that just happens to be a conveinent extra, it is purly about economy.

Typcally diesel models see 25--35% better fuel over their petrol counter parts. This does depend on the model in question, often you'll find manufacturers only offer smaller displacment deisels with less power, so they then tend to be driven harder.

Land Rover Discovery S1 & S2.

3.9 EFI V8 Petrol - 12-18mpg
2.5 TD Diesel - 24-32mpg

From a 3 litre Mercedes Diesel in the JK I would expect a manual to be capable of mid 20's as an overall average and probably best part of 30mpg on the freeway as long as you are not running at silly speeds.
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Unread 10-05-2006, 03:14 AM   #10
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Quote:
Originally Posted by 300bhp/ton

Diesels are NOT sold for power or low end torque that just happens to be a conveinent extra, it is purly about economy.
I dunno about that. I say it depends, well at least in america. Diesels sold in cars are for gas mileage, but any diesel sold in a truck, is all about power. Its just conveinent that it gets better mileage.
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Unread 10-05-2006, 07:51 AM   #11
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Quote:
Originally Posted by Bgeddes
We have an '05 KJ Diesel, a few coworkers have '05 gas KJs.

We get 23-24 in town (in the mountains) and right at 30 highway.
Gassers get 15 in town and 20 on the highway.

The CRD option was ~$1800. With the high gas prices, regular gas was $0.20 less than Diesel, we have just about paid for the option. Now the price difference is more like $0.40. Because we get 150% of the miles for 120% of the price, we still gain.

The VM Motori engine used in the Jeep Diesels is TINY. I would easily fit into an early CJ5. It's shorter than the Dauntless. Some day our CRD will power a Wrangler of some sort.

A few quick specs, 2.8L, turbo charged, intercooled, 4cyl. About 165hp, about 300 ft/lbs. Compare that to a 258 or 4.0, and see how the little mill fares.

I can make fuel for my Diesel in my backyard, can you make gasoline at home?
Have you changed the exhaust system on your CRD? From what I heard changing the OEM (which is the same system used for the 3.7 and old 4-banger gasser engines) to something less restrictive can give you a significant (1 - 3 mpg) improvement on the CRD. Supposedly, a $30 cherry bomb is enough to quiet the CRD.

Oh ya, now I remember what I was going to say... We're not going to see this VM engine here in the US. Unfortunately it won't pass emissions and from what I hear, none of the VM plants do. As far as I know the only diesel that DC has certified for the US so far is the 3.0 V6 from Mercedes. So if they will be offering a CRD JK in the near future (MY 2008) that would have to be it. THis is all my guessing of course...
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Unread 10-05-2006, 09:27 AM   #12
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Quote:
Originally Posted by 300bhp/ton
Diesels are NOT sold for power or low end torque that just happens to be a conveinent extra, it is purly about economy.
Not sure that is 100% correct.

For cars, that is correct.

However, for trucks (anything from the Liberty to 18 wheelers) that is not the case.

The torque of a diesel can not be matched by a gasser, which means if you are pulling any kind of load, or doing any driving which requires torque (rock crawling, etc . . .) the diesel engine is the best option for you.
For these people, the MPG advantage is purely icing on the cake.

Why you want a diesel depends on how you drive. If you use it to commute, and never pull a load, you care about the MPG.
If you use it off-road and/or pull a load, you want the diesel for the power/torque.
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Unread 10-05-2006, 09:50 AM   #13
LEDFoot
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Quote:
Originally Posted by strobengh
Not sure that is 100% correct.

For cars, that is correct.

However, for trucks (anything from the Liberty to 18 wheelers) that is not the case.

The torque of a diesel can not be matched by a gasser, which means if you are pulling any kind of load, or doing any driving which requires torque (rock crawling, etc . . .) the diesel engine is the best option for you.
For these people, the MPG advantage is purely icing on the cake.
I would not call it just icing on the cake... with higher MPG also comes extended operating range which can be very important on expeditions.
Also diesels are typically more reliable, especially on low grade fuels you find in some places where 4x4 are required (like Africa or South America).
Of course, on a modern diesel you would probably have to remove your catalytic converters ant particulate filters before using this kind of fuel.
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Unread 10-06-2006, 01:58 AM   #14
300bhp/ton
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Quote:
Originally Posted by strobengh
Not sure that is 100% correct.

For cars, that is correct.

However, for trucks (anything from the Liberty to 18 wheelers) that is not the case.

The torque of a diesel can not be matched by a gasser, which means if you are pulling any kind of load, or doing any driving which requires torque (rock crawling, etc . . .) the diesel engine is the best option for you.
For these people, the MPG advantage is purely icing on the cake.

Why you want a diesel depends on how you drive. If you use it to commute, and never pull a load, you care about the MPG.
If you use it off-road and/or pull a load, you want the diesel for the power/torque.
I think 18 wheelers are a totally different ball game. A Wrangler is much more akin to a car than a 40 tonner.

I hear what you say, but I guess living in the US maybe it offers a different view point. But go take a look at ALL the diesels offer world wide in 4x4's. From Nissan Patrol, Mitisbushi Shogun, Land Rover Discovery, BMW X3, Mercedes G Wagon or M class, Range Rovers, Defenders, Toyota's. Along with all the non-American market 4wd pick uptrucks, Ford Ranger and so.

In every case the diesel is smaller and less powerful than the petrol counter part. So most of the time they are less powerful, sure they may make torque lower in the rpms, but overall the are comparitivly underpowered.

The same trend follows in 99% of all disel cars. You probably don't get them in the US much. But basically EVERY normal car has a disel in it's line up. And usually it is no where near the most powerful.

A nice example, my DD is a Peugeot 106 XND. It has a 1.5 litre straight diesel (no turbo) and is the least powerful engine for that model with about 50bhp. However it does average over 60mpg. Petrol versions are more spritly but will tend to be 40-45mpg.
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Unread 10-06-2006, 08:17 AM   #15
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There has to be a freakin conspiracy here.

If you go to Europe, almost every vehicle is diesel. All these SUV's and cars are sold here in the US, just without the diesel option. They get motors with 30-60 mpg and a life of 250,000 miles; we get 20-35 mpg and engine life spans around 150,000, if you’re lucky. This is in a country with hardly any pedestrian or bicycle access and a miserable mass transit system. We are completely vehicle dependant.

People are talking about the future possibility of hydrogen vehicles, hell even ethanol like Brazil. We haven't even been given the option of more diesel engines. My 05' doesn’t even accept ethanol !! Do the new JK's? Ethanol which is made from corn or sugarcane, the stuff we pay farmers millions of dollars to allow their crops to rot in the fields so the market isn't flooded, is $0.30/gal cheaper here than basic gas. Even this would be an improvement!!

Sorry for the vent.
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