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fast80cc
Dodge Dakota
7/04/2001
03:00:33
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 Subject: New 3.7L vs good old 3.9!
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Wow, there's some GREAT discussion on this Forum! I've seen a few flames but everybody seems to know what they're talking about! It's funny, my karting buddies think trucks are supposed to be trucks (i.e. not fast). Think I'll send them the www.dragtruks.com website just to piss them off! I've got a Neon ACR (real light, nice stock engine with some simple mods, pretty fast). It'll do high 15's in the 1/4. That's def. faster than my new Dak. But, guess what, the Dak FEELS faster! Down low GRUNT (torque) is what's a blast! You can't beat CCs for that. I looked at the www.jeep.com site for specs. on the new 3.7L. It's interesting, they've done the typical marketing deal - up'd the HP at the expense of torque. Don't get me wrong, that'll be a GREAT motor (in the Daks in 2003/4 - long wait...). Clearly the marketing guys told the engineers they needed to get the HP numbers up. Consumers look at those (as do the mags.). Funny though, the 3.7L has a whopping 210HP (35 MORE than the current V6), BUT... Again, CCs tell the torque story here. They're only getting 10ft-lbs more (235)?!? I'm an engineer (the "wrong" kind - electrical, don't know that much about engines). I do know that you can always make trade-offs in a design. You can get a higher HP number, but it might be REAL high in the rev. range. Look at the 3.7. It's PEAK torque number (235 ft-lbs) is a 5000!!! RPM. Even my little 2.0 DOHC Neon rice-burner (it's a Mitsubishi motor - sorry) has a torque peak lower than that. Do those marketing guys really think the average Jeep Liberty buyer is going to rev. their baby that high? Guess what, they won't even get the chance if they keep it in "D". The 3.7L is apparently only going to come in the "Limited" version, which ONLY comes with an auto! Sorry guys - guess I'm just a believer in good old fashion "grunt" when it comes to a truck (used to an old F150 straight 6,
4L). I want my torque to kick in at 2000 RPM (gotta love those push-rods)! Anyway, I had a bit of a case of V8 envy (4.7 that is). Wish I could've gotten a super deal on a 4.7 with a stick, but they're sooo rare it'd have cost a bundle more. Hey the ol' 3.9 ain't that BAD. Sounds like you Forum guys have the pinging problem licked. Those new V6's in the Liberty's will be pulling another 500lbs around. Let's see: headers, Gibson catback, V8 t-body, cold-air intake and I should be able to surprise a few of them...
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sandman
Dodge Dakota
7/04/2001
14:38:25
|  RE: New 3.7L vs good old 3.9!
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I will agree that you can not beat torq. There is an old saying in the auto industry here in America. "American buy Horse Power but Drive Torq." The average joe has no idea what one or the either is. They have been marketed to for years to look for "V8" and "HP".
The market nich that Jeep is hopeing to fil with the Liberty is not the Hard Core truck driver. Can you say 24-40 year old sussie home makers and soccer moms. They might also cross over to Young single Proffessionals 24-34. This segment of the market will not mind the 3.7 or it's lack of low end troq. Cafe standards are going to be forceing alot of vechiles to use smaller displacements engines as time goes on. I doubt that you will see the old long stroke torq. monster of yesterday in most daily drivers anymore.
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jimgee
Dodge Dakota
JOIN HERE
5/14/2003
14:39:13
| RE: New 3.7L vs good old 3.9!
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i was going to get a jetchip stage two since i have
flowmaster exhaust does it help any or should i
reconsider
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Ryan
Dodge Dakota
JOIN HERE
5/14/2003
14:42:50
| RE: New 3.7L vs good old 3.9!
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Jim, doesnt really apply to the topic, but what engine do you have? If you have a 3.9L I would go with the Jet chip.
v8Performance.com - Dodge Performance Products
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jimgee
Dodge Dakota
JOIN HERE
5/14/2003
14:47:35
| RE: New 3.7L vs good old 3.9!
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thanks dude.
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brandon
Dodge Dakota
JOIN HERE
10/11/2005
16:10:15
| RE: New 3.7L vs good old 3.9!
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i bought a 04 dodge runing the 3.7L i have never owned a 3.9 but i have driven a few. i got a full size ram but i realy woulf like to get a dakota here soon. i put on a stage 2 jetchip, super 40 flows with singal side exit for a deeper tone, high flow cats, dule cold air intake kit from boms, ngk iridum plugs,and a bbk thottle body spacer. i dident see a huge gain but im satisfide with the results, i resently was able to get out to the track and i out ran my best bro in his 4.7 dodge ram. i cant take down a hemi and probly will never beable to but if neone can give me a line on a good set of headers i would realy be in debt to yall thanks, brandon
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Craig
Dodge Dakota
JOIN HERE
10/12/2005
16:23:35
| RE: New 3.7L vs good old 3.9!
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The 3.7 with the 3.92s and a stick can absolutely outrun the 3.9 in almost every respect. I'm sorry, I looked at a 3.9, but held out until the 3.7 was offered in '04 for that reason.
As for your peak torque figure, the Dodge website claims 235 lb/ft of torque at 4,000 RPM, and 210 hp at 5,200 RPM.
Well, either way it's immaterial. The 3.7 feels noticiably more powerful. It does like to rev- when was the last time you had your truck up at 6000 RPM? ;-)
And the 3.7 seems to hold up very well in the Liberty.
Both are very good motors, but I would never consider trading my 3.7 for a 3.9.
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Mikes99Dakota
GenIII
10/13/2005
10:12:44
| RE: New 3.7L vs good old 3.9!
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My friend Jeremy bought his 04' CC 3.7L 5spd. with 3.92s/Suregrip and that thing is a blast to drive.
Craig ur right about the rpms it loves it. As a matter of fact when he ran that thing with just a flowmaster he ran a 16.0 @ 85mph Not bad for a V6. He is thinking of turbocharging the truck and that means my lil ol' 5.2L might have a hard time!!!
These trucks are great he put down 171 rwhp and 202 rwtq. The h.p. was almost as much as mine 181 rwhp stock!
1999 RC Auto 5.2L
Mopar PPH, Magnaflow 3" w/cut-out, 3.90s/Suregrip, 50mm Fastman TB
Track Times:
9.47 @ 72.21mph
14.89 @ 91.33 mph
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Mopars 318
Dodge Dakota
JOIN HERE
10/13/2005
15:03:08
| RE: New 3.7L vs good old 3.9!
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I agree the 3.7 is quicker then the 3.9 coupled with a good gearing but I will garantee you the 3.9 is much more reliable. Cant beat the good ol' tried & trusted 3.9/5.2
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99DAK
Dodge Dakota
JOIN HERE
10/13/2005
17:24:44
| RE: New 3.7L vs good old 3.9!
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3.9L - forged steel rods and pistons, cast iron heads, aluminum intake
3.7L - powder-forged rods, cast aluminum pistons, aluminum heads, plastic intake
I'm sure the 3.7s are fine, but I wouldn't use forced induction on one.
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Craig
Dodge Dakota
JOIN HERE
10/13/2005
22:52:23
| RE: New 3.7L vs good old 3.9!
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^^perhaps you are right. But the pistons in the 3.7 are forged. The rods are powder forged to save weight on the rotating assembly, in an effort to make the engine rev faster (and higher). I think a fair ammount of development actually went into the process. I would say it will hold up fine with supercharging, or NOS. Might want to shot-peen the rods, but other than that it's ready to rock. My biggest concern would be stroking: it uses a two piece block that would probalby not react well to the increased crankcase pressures involved with stroking an engine.
It runs in my mind that the 3.7 and 4.7 are similar in design...
And remember, the 4.6 Ford uses a plastic intake, and holds up VERY well to supercharged applications. In fact, it's one of the only cost effective ways to get power out of the Ford 4.6.
But I won't argue that the 3.7 is going to be better for longevity than the 3.9- you really can't mess with the 3.9/5.2, as it has proven itself very well in the working world. But I like the superior power and fuel econemy of the 3.7.
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Mikes99Dakota
GenIII
10/14/2005
09:55:06
| RE: New 3.7L vs good old 3.9!
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99DAK the 3.9L doesnt have forged pistons like the 3.7L and btw the 4.7L doesnt either.
From what I undertand you can boost the 3.7L and should have any problems except with maybe the head gaskets. and why do yall talk about rods on a 3.7L = OHC and no puchrods here.
1999 RC Auto 5.2L
Mopar PPH, Magnaflow 3" w/cut-out, 3.90s/Suregrip, 50mm Fastman TB
Track Times:
9.47 @ 72.21mph
14.89 @ 91.33 mph
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99DAK
Dodge Dakota
JOIN HERE
10/14/2005
10:05:19
| RE: New 3.7L vs good old 3.9!
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Sorry, should have said forged, but they (pistons) are nonetheless aluminum, not steel. I agree that the plastic intake is probably not a big deal, but it'll be interesting to see how these things are holding up 10 years and 200K miles down the road.
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99DAK
Dodge Dakota
JOIN HERE
10/14/2005
10:27:46
| RE: New 3.7L vs good old 3.9!
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Ok tell me if I have this right-
3.7L - forged aluminum pistons
4.7L - cast aluminum pistons
3.9L - cast (?) steel pistons
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99DAK
Dodge Dakota
JOIN HERE
10/14/2005
10:30:17
| RE: New 3.7L vs good old 3.9!
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"and why do yall talk about rods on a 3.7L = OHC and no puchrods here."
I was referring to piston rods, not pushrods.
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cuzindoug
GenIII
10/14/2005
10:55:57
| RE: New 3.7L vs good old 3.9!
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The 3.9 are cast aluminum with a tin coating i do believe. The only magnum engine that I know of now that has other than aluminum piston heads are the hemi which are cast iron i think.
If it ain't broke, fix it til it is.
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99DAK
Dodge Dakota
JOIN HERE
10/14/2005
11:09:27
| RE: New 3.7L vs good old 3.9!
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Thanks for clearing that up for me, in the absense of anything I could find about 3.9L pistons on the web I just assumed they were steel. Is that a Magnum thing, or did LA engines have aluminum pistons?
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Mikes99Dakota
GenIII
10/17/2005
09:39:05
| RE: New 3.7L vs good old 3.9!
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Message:
99Dak,
OOOps, I should have known....i stand corrected.
1999 RC Auto 5.2L
Mopar PPH, Magnaflow 3" w/cut-out, 3.90s/Suregrip, 50mm Fastman TB
Track Times:
9.47 @ 72.21mph
14.89 @ 91.33 mph
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Yates-N-Dee
Dodge Dakota
JOIN HERE
10/18/2005
17:25:11
| RE: New 3.7L vs good old 3.9!
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The 3.9/5.2 is much more reliable Ill garantee you that. A motor well capable of 200-300k. May not be as quick with the less power it generates but Id take reliability any day.
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jayb
Dodge Dakota
JOIN HERE
10/18/2005
17:51:48
| RE: New 3.7L vs good old 3.9!
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i wouldn't jump all over the powerband of a 5.2L magnum. it has the same torque rating. and now, the never 4.7's are designed to have less low end grunt, to get that peak # higher.... dont know why... they only have 5 more hp. WOW! sounds like it was worth all the time to redesign a motor.
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Mikes99Dakota
GenIII
10/19/2005
09:36:14
| RE: New 3.7L vs good old 3.9!
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Message:
Well I wil tell you what JayB, The torque curve is broader on the 5.2L than the 5.9 or 4.7 I have buddies that dynoed both the trucks and the 4.7L showed sorta peaky torque number and the 5.9L peaked the torque lower than the 5.2L but wasnt as broad across the rpms. All these motors are great but the 5.2L isnt all that bad.
1999 RC Auto 5.2L
Mopar PPH, Magnaflow 3" w/cut-out, 3.90s/Suregrip, 50mm Fastman TB
Track Times:
9.47 @ 72.21mph
14.89 @ 91.33 mph
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