Re: What year 3.9 -> 3.7?

From: Gary Hedlin (superdak@gmail.com)
Date: Thu Apr 08 2010 - 22:06:39 EDT


When I was looking at the Gen4's, the 3.7 engines were actually rated
worse than the 4.7's when it came to fuel economy. If I recall
correctly, the 3.7's were rated at 14mpg highway, and the 4.7's were
rated at 18mpg. I'm pretty sure it was due to the HP to weight ratio,
but I never did get why Ma Mopar put that engine in a Gen4 when the
mileage would be worse.

But the 3.9 in my 98 usually gets about 20/22mpg, that's with all the
chrome. I haven't seen what the 3.7's in a Gen3 gets, but I'm sure it
has to be better than in the heavier Gen4. Of course, I never saw
that many Gen3's with the 3.7 since I think 04 was the only year that
it was available..... probably a good thing.

I would probably stick with the 3.9 in a Gen3, Gen4.... just go for a 4.7.

Hopefully in the next few weeks, I'll be able to report on what a 1972
340 block crammed in the 98 gets for fuel economy! :)
http://picasaweb.google.com/superdak/340#

Gary

On Thu, Apr 8, 2010 at 6:34 PM, <jon@dakota-truck.net> wrote:
>
> "Mr. Plow" <adam_is_mr_plow@hotmail.com> wrote:
>
>
>> I'm curious what year they switched to the newer 3.7 engine?
>> Is it actually any better in terms of fuel economy?
>>
>> I'm planning on selling my '02 Durango and getting back into a Dak.  :D
>
>
>    Unfortunately I'm not going to be able to give you any data that
> you can actually use, but just wanted to chime in to say you are
> definitely wise to ask!  I know that with the Magnum series of
> engines, the 3.9 didn't do all that much better than the 5.2 in the
> fuel economy department, especially when you actually use the truck as
> a truck.  If you had a really light Dak and drove it like Grandpa,
> then maybe...  However, I know that does not apply to you - I know
> what the "two words" are, and they are not "slow down"!  ;-)
>
>    Again, I have no hard data, but based on the previous experiences
> of DMLers with the 3.9 vs 5.2, I would not be surprised if the 3.7 got
> even worse mileage than the 3.9, given that the Daks the 3.7 got
> installed in are heavier than ever, and the 3.7 probably gives up some
> low end torque to the 3.9 due to the pushrod to OHV change.  (I could
> be wrong about that, I have not tried to pull up any dyno data, but I
> have talked to folks who have owned both the 5.2 and 4.7 who were not
> happy with the lack of torque in the latter as compared to the former,
> so I am assuming - dangerous I know - that the 3.7 and 3.9 are similar
> in that regard.)
>
>
> --
>                                          -Jon-
>
>  .- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
>  | '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
>  `-------------------------------- http://www.jonsteiger.com --'
>
>

-- 
Gary Hedlin
Hedlin Web Designs
(815) 993-0792
www.hedlindesigns.com

--Many talk about those who died, but too few talk about those who survived... THANK A VET!



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