3.7L V6 Decent or not?

InCommando · **Posted:** Wed Oct 19, 2005 11:52 am

During a recent discussion on anohter Jeep BBS, some mention was made that the 3.7L sucks and we routinely trash it on the KJ forums. I have not seen this and I am very happy with the engine coupled to the 6-spd. Opinions?

pixeldzn · **Posted:** Wed Oct 19, 2005 11:58 am

InCommando wrote:

During a recent discussion on anohter Jeep BBS, some mention was made that the 3.7L sucks and we routinely trash it on the KJ forums. I have not seen this and I am very happy with the engine coupled to the 6-spd. Opinions?

I think its probably got more power than the old inline-6. Only downside is the gas mileage - but that's more due to the KJs weight than anything else. I'm happy with it so far.

Skyjump136 · **Joined:** Tue Jul 05, 2005 6:50 pm **Posts:** 1633

I spend a fair amount of time reading KJ forums and I've never heard of widespread problems with it. Its a great engine.

BlueFreedom · **Posted:** Wed Oct 19, 2005 2:33 pm

It's just OK as far as I'm concerned. I think they could have made it more advanced (more than 2 valves per cylinder) and made it more efficient (yes the Liberty does weigh a lot) and definitely more power (210hp from 3.7 liters is probably one of the smallest hp to displacement ratios in cardom today.)

That being said, it is reliable, runs smooth and should last a long time.

JediJeeper · **Posted:** Wed Oct 19, 2005 3:26 pm

It may not have the highest HP rating for displacement/configuration, but it does have a very very usable torque curve for wheeling. The 3.7L torque curve peaks at a lower RPM than a lot of it's competitors which translates to better low RPM grunt for off roading.

All in all I think it is a very decent first-gen engine. Being the cut-down version of its big brother V8 lets it benefit from most of the longevity R&D DC did for the V8.

No complaints here, I like it's simplicity.

-Adam

Eddo · **Joined:** Thu Jul 07, 2005 7:01 pm **Posts:** 1214

Personally, I think the 3.7L is a great little motor. Could it have been better? Of course it could have been, but the same with any engine. It is reasonably reliable, gets good gas mileage for push a 4k+ brick... how many other 4k+ SUV's that are shaped like a brick get better mileage than the KJ? Torque while is not the exceptional low-end torque of a 4.0 it is a hell of allot better than car engines. It will pull a 3k trailer plus my 4200lb KJ across the country without a problem cruising at highway speeds. That is the engine essentially moving the Jeep and another small car.

High HP to displacement engines are just marketing tactics especially in a truck or SUV. Low-end torque is more important for a truck or SUV. Typically if you want a high hp to displacement engine you sacrifice low-end torque. Also, usually the high hp/displacement engine get better mileage because you need to make the engine scream to produce the high power. Most people don't make their engine scream on a regular basis. Therefore, you are producing less power which means you are using less fuel.

BlueFreedom · **Posted:** Wed Oct 19, 2005 7:18 pm

Whether high horsepower engines are a manufacturers marketing tactic or not, I've never heard anyone (high horsepower engine owners) complain about it (I know when I'm accelerating from an entrance ramp I certainly wouldn't be!)

I don't make my engine scream on a regular basis (in fact I'm quite the opposite) and I still only get about 13 miles around town (that's about the same as my neighbor who has a Mountainer with a 4.6 liter V8.)

Come to think of it what do owners of Grand Cherokees with the 4.7 liter engine get around town?

Ed · **Posted:** Wed Oct 19, 2005 7:54 pm

High Horsepower figures are indeed just a marketing tactic. Power is work (done in a straight line) divided by time. Since there's all sorts of whirly bits in a car engine the actual horsepower isn't measured. Instead the torque's measured and then the power can be calculated as torque times rpm divided by 5252.

This is why when you see high horsepower figures given they're always at really high rpms. Little racy engines (especially turbos) will produce really high horsepower values, but only once you wind them up to like 8500 rpm. You can see this in F1 cars, they're always quoted as having like 900+ horsepower, and yet the mechanics still like to give them a bit of a push to get them going out of the pits. That's because they've got virtually no low down torque (and also very light flywheels, or none at all, but that's a different matter) but will rev to something stupid like 20,000rpm.

Of course the ability of an engine to maintain its torque at such high revs is what gives you a high top speed, but for 4WDing you're not likely to have the rev counter hovering around the red-line are you? So you want lots of low down torque and an engine that probably won't rev very high, and so won't give a very high horsepower figure.

When you're accelerating from an entrance ramp that's the low down torque you're using. You use the high horsepower when you're blasting along the highway at 100mph!

High torque = quick acceleration, hill-climbing ability and towing
High power = high top speed.

PitViper · **Posted:** Wed Oct 19, 2005 8:00 pm

I've had 2 and both have Impressed me since day one.

USAFCOP · **Posted:** Wed Oct 19, 2005 8:06 pm

well, mine is gutless...

I have been on many uphill climbs that the engine will bog and the only way she will even try to climb is in 4 low... now in 4 low, it does awesome in the torque and power dept!

2wd, it is gutless after adding the wheels tires rack, and all the armor... Truck is just too heavy for the little V6 in my opinion, at least when mated to the 45 rfe and 3.73 gears anyway

auggy · **Posted:** Wed Oct 19, 2005 8:14 pm

No complaints here! For a little truck it has decent acceleration and decent gas milage (for its fat little butt)

. Also, It has a pretty good top speed for its type of car (over 100 miles per hour for sure); not that it's needed, but it's there.

raceinfan · **Posted:** Wed Oct 19, 2005 8:19 pm

I own 2 both 04's no complaints here & 4lo is great on the trail I would buy another one

L.O.S.T. 4 LIFE
04 COLUMBIA ED. & 04 SPORT

FreedomKJ · **Posted:** Wed Oct 19, 2005 8:57 pm

I'm happy with my little 3.7L. I can even spin the tires from a stop, so I'm happy.

Oh, and the reason there's only 2 valves per cylinder is to help with the low end torque. It also makes the engine cheaper to produce as there are fewer parts.

They can get away with big "heavy" valves because the engine doesn't rev up very high, whereas cars with high redlines need smaller, lighter valves to reduce inertia in the drivetrain components. It takes that valve spring a little bit longer to push the heavy valve closed than it takes to push the light valve closed. That doesn't mean much at low RPMs, but when you get up to higher RPMs you don't want your valves lagging behind everything else. Make sense?

roadrunner · **Posted:** Thu Oct 20, 2005 1:38 am

I'm very pleased with it so far. It has some outstanding design features, like roller cam followers (most engines have stamped steel), and timing chain (rarely seen today on production engines). These add up to a more reliable and durable engine. They also make the engine more expensive to produce.

IMO it has an excellent combined power and torque range, and operates quite efficiently -- moves the Liberty's heavy, non-aerodynamic body pretty darned well!

Tightwadsjeeper · **Posted:** Thu Oct 20, 2005 9:10 am

I've been happy with mine so far.

I guess the only thing that really puzzles me is the extreme difference in mileage reported by different users... even among vehicles that are relatively similar in model/year/mods. I personally get decent mileage out of mine (average ~19 mpg most tanks, and have gotten as much as 24 on a highway trip), but some other owners are having trouble getting 15 mpg. :?:

Luis

Eddo · **Joined:** Thu Jul 07, 2005 7:01 pm **Posts:** 1214

Tightwadsjeeper wrote:

I've been happy with mine so far.

I guess the only thing that really puzzles me is the extreme difference in mileage reported by different users... even among vehicles that are relatively similar in model/year/mods. I personally get decent mileage out of mine (average ~19 mpg most tanks, and have gotten as much as 24 on a highway trip), but some other owners are having trouble getting 15 mpg. :?:

Luis

I really think it has to do mostly with driving style even if people say they are a not a hard driver. I know people that barely get more than 20mpg out of a corolla and they say they don't drive hard either. I guess driving hard is all relative. I still get good mileage out of mine even being lifted.

Joe Jeep Owner · **Posted:** Thu Oct 20, 2005 9:59 am

I agree with the huge reported differences in mileage and cant figure it out myself. Other than my tires, I have a stock 2002 and I dont get near 24MPG that some of the heavily modified owners are reporting. Although I dont think I am as low as 13 MPG either. I'm constantly searching for new ways to improve on it but there are so many variables it gets confusing.

I dont know, I like the Jeep a lot and would definatley buy another. The mileage is just something you have to deal with.

tniverth · **Posted:** Thu Oct 20, 2005 10:00 am

I have had no problems with mine in the 110,000 miles I've got, I have also put some bolt on mods.

My mileage is about 18.5 eveyday driving and long hiway trips about 21.5.
Thats lifted with bigger tires.
I don't hear of any complaints except from people who want a more performace oriented vehical :roll:

and they should not look at a Jeep for that type of driving anyway.

BlueFreedom · **Posted:** Thu Oct 20, 2005 11:08 am

Yes, I'd like to know why I get such terrible gas mileage, like I said I don't drive the vehicle "hard" at all (with a 2 and 3 year old in the back seat that wouldn't be too smart). I am not lifted and have only upgraded my tires to Pirelli Scorpion All Terrains.

Per tniverth's post: I knew going in that the Jeep was not a performance vehicle (Jeep does not = Corvette) and didn't expect nor want the best 0-60-1/4 mile-braking distance numbers to be what a sports car would achieve. I'm not even that dissapointed in the acceleration, it's more the bad gas mileage (at least for my particular Liberty). BTW I am glad to hear that you've gotten 110,000 miles out of your Liberty I do intend to keep mine for a long time as well.

I love my Jeep, its performance is great off road, but I'm not going to blindly overlook it's weaknesses. I don't mean to offend anyone, it's just my opinion (which we are all entitled to) and observance of my Liberty.

Jeepjeepster · **Posted:** Thu Oct 20, 2005 11:17 am

the 3.7 does just fine in the libby.

3.7L V6 Decent or not?

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