Re: [AMC-list] Mileage with AMC/Jeep 4 Cyl 2.5 EFI or 4.0 in an 80's AMC

[adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)]

" From: Frank Swygert <farna@xxxxxxxxxxx>
" 
" I have a hopped up 4.0L and get about 22 mpg cruising at 70 mph. I've
" got 3.55 gears and an AW4 auto trans from a 2WD Cherokee. I feel it
" would do great with 3.31 gears, but don't want to pony up the dough to
" change the gears just for a couple more mpg. Mark Price is running a
" 4.0L in an American with a five speed. I don't recall his rear axle
" ratio, but he's reported getting around 24 mpg cruising. Both are about
" in line with a typical Cherokee that's been kept in top condition...
" maybe a couple mpg more in both cases. A dogged out Chero won't get
" that much, of course!

your car is a classic, a little heavier than mark's american.  that
must account for some of the difference.

i get 23@65 and 24@55 in my gf's 4.0/auto/2wd xj.  when i posted that
on an xj list, another poster replied he gets 25@65 in his 4.0/5sp/4wd
xj.  they also are heavier than an american or spirit though about
equal with a classic, as well as worse aero.

are you sure that 3.31s would be meaningful over 3.55s?  that's like
cruising at 65 instead of 70 for rpm.  my experience suggests you'd be
lucky to pick 1 mpg up for the swap.

" You should be about in line with a four cylinder Cherokee in a Spirit,
" maybe 2-3 mpg better, so you're talking mid to upper 20s as far as
" mpg, with 20-24 as an all around average. I'd use a five speed and
" something like a 3.55 axle. That should be about right for the four,
" a little taller than the 4.10 used in Cherokees with the four.

there was a brief economiser pkg with the 4 in the late '80s, with a
3.31 axle...

i agree though, if you don't recam the engine for more low end.  both
the 4 and 6 are cammed rather higher than the older sixes, in line
with the modern era's creeping performance expectations and auto
tranny prevalence.  the 4.0/5sp xj's geared with 3.07s, but
[anecdotally] loses very little with 4.10s, as they actually put the
engine more in line with it's most economical rpm at highway speeds.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh@xxxxxxxxxxxxxxxxx                       and think what none thought
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