JEEP question - 4.0 vs 4.0HO

hey everyone! got a question for all you jeep gurus out there... i'm
sure that someone can answer my question for me. ok, i have an 88
cherokee with the 4.0 in it. now i remember a while back when i was
just searching around reading articles on the internet someone said
that the only difference between the regular 4.0 and the high output
was the computer? the old was made by bendix if i remember right?
anyways, in the same post i read that when they switched over to the
high output jeep offered a mopar upgrade kit to turn the old 4.0 into
the HO. i went to my local jeep dealership's parts dept to talk to
them, and they said that they haven't heard of it and if it does exist
then it was probably made by an aftermarket manufacturer. however, he
didn't seem like the smartest guy in the world and he didn't even
bother to look for it so there might be a mopar upgrade. my question
is have any of you ever heard of this kit? if it is a mopar part do
you know the product number? if it's aftermarket who makes it? i
really want to do this. have any of you ever done this before or heard
of it being done? money isn't too much of a worry so im not too
concerned with the cost. a friend suggested that i go to a junkyard
and pull the computer and all the associated wiring of a newer
cherokee, but i don't know if it's just that simple. any input would
be greatly appreciated. thanks in advance!

james morrow

IIRC, the change to HO was 1991 for the XJ Cherokee. However, it wasn't
just a computer change: Jeep also redesigned the head, intake manifold and
exhaust manifold.

It's not impossible to upgrade to HO, but it's a bit of work. check out
rec.autos.makers.jeep+willys for a lot of people that know a lot more about
it than I do

Chuck


"James Morrow" <[email protected]> wrote in message
news:[email protected]...
> hey everyone! got a question for all you jeep gurus out there... i'm
> sure that someone can answer my question for me. ok, i have an 88
> cherokee with the 4.0 in it. now i remember a while back when i was
> just searching around reading articles on the internet someone said
> that the only difference between the regular 4.0 and the high output
> was the computer? the old was made by bendix if i remember right?
> anyways, in the same post i read that when they switched over to the
> high output jeep offered a mopar upgrade kit to turn the old 4.0 into
> the HO. i went to my local jeep dealership's parts dept to talk to
> them, and they said that they haven't heard of it and if it does exist
> then it was probably made by an aftermarket manufacturer. however, he
> didn't seem like the smartest guy in the world and he didn't even
> bother to look for it so there might be a mopar upgrade. my question
> is have any of you ever heard of this kit? if it is a mopar part do
> you know the product number? if it's aftermarket who makes it? i
> really want to do this. have any of you ever done this before or heard
> of it being done? money isn't too much of a worry so im not too
> concerned with the cost. a friend suggested that i go to a junkyard
> and pull the computer and all the associated wiring of a newer
> cherokee, but i don't know if it's just that simple. any input would
> be greatly appreciated. thanks in advance!
>
> james morrow

On Tue, 1 Jun 2004 07:37:28 UTC [email protected] (James Morrow)
wrote:

> hey everyone! got a question for all you jeep gurus out there... i'm
> sure that someone can answer my question for me. ok, i have an 88
> cherokee with the 4.0 in it. now i remember a while back when i was
> just searching around reading articles on the internet someone said
> that the only difference between the regular 4.0 and the high output
> was the computer? the old was made by bendix if i remember right?
> anyways, in the same post i read that when they switched over to the
> high output jeep offered a mopar upgrade kit to turn the old 4.0 into
> the HO. i went to my local jeep dealership's parts dept to talk to
> them, and they said that they haven't heard of it and if it does exist
> then it was probably made by an aftermarket manufacturer. however, he
> didn't seem like the smartest guy in the world and he didn't even
> bother to look for it so there might be a mopar upgrade. my question
> is have any of you ever heard of this kit? if it is a mopar part do
> you know the product number? if it's aftermarket who makes it? i
> really want to do this. have any of you ever done this before or heard
> of it being done? money isn't too much of a worry so im not too
> concerned with the cost. a friend suggested that i go to a junkyard
> and pull the computer and all the associated wiring of a newer
> cherokee, but i don't know if it's just that simple. any input would
> be greatly appreciated. thanks in advance!

There's more to it than just the computer. They get what? 25? 40? hp
more out of the HO with a different head, new manifolds, some changes
to the throttle body, etc. etc. The computer is just part of the
change.

I've never heard of a MOPAR drop-in replacement. I imagine that you
could fit the MOPAR MPI upgrade they make for the 258 to it, but
that's $2k or so - more than I want to consider for a tired 4.0 that's
run fine for 160,000 miles. I did look at swapping in one of the HO
engines from a wreck a while back but that's still a lot of work for
what would not be that much of an improvement over the one I'm running
now with the Rennix (Rennault-Bendix) computer. The only way I'd look
at swapping the computers would be if this one died and I couldn't
find another one in the boneyard.

--
Will Honea

one other possibility i didn't think of earlier is maybe the Mopar
Performance computer for the Renix system? Those aren't made by D-C
anymore, but if you are persistent, you might find one on ebay... i did
it cost me about $150. Of course, I'm also building a long-rod stroker, so
the computer may do more for me than it will for a stock engine.



"Will Honea" <hwj25(remove this)@qwest.net> wrote in message
news:[email protected]...
> On Tue, 1 Jun 2004 07:37:28 UTC [email protected] (James Morrow)
> wrote:
>
> > hey everyone! got a question for all you jeep gurus out there... i'm
> > sure that someone can answer my question for me. ok, i have an 88
> > cherokee with the 4.0 in it. now i remember a while back when i was
> > just searching around reading articles on the internet someone said
> > that the only difference between the regular 4.0 and the high output
> > was the computer? the old was made by bendix if i remember right?
> > anyways, in the same post i read that when they switched over to the
> > high output jeep offered a mopar upgrade kit to turn the old 4.0 into
> > the HO. i went to my local jeep dealership's parts dept to talk to
> > them, and they said that they haven't heard of it and if it does exist
> > then it was probably made by an aftermarket manufacturer. however, he
> > didn't seem like the smartest guy in the world and he didn't even
> > bother to look for it so there might be a mopar upgrade. my question
> > is have any of you ever heard of this kit? if it is a mopar part do
> > you know the product number? if it's aftermarket who makes it? i
> > really want to do this. have any of you ever done this before or heard
> > of it being done? money isn't too much of a worry so im not too
> > concerned with the cost. a friend suggested that i go to a junkyard
> > and pull the computer and all the associated wiring of a newer
> > cherokee, but i don't know if it's just that simple. any input would
> > be greatly appreciated. thanks in advance!
>
> There's more to it than just the computer. They get what? 25? 40? hp
> more out of the HO with a different head, new manifolds, some changes
> to the throttle body, etc. etc. The computer is just part of the
> change.
>
> I've never heard of a MOPAR drop-in replacement. I imagine that you
> could fit the MOPAR MPI upgrade they make for the 258 to it, but
> that's $2k or so - more than I want to consider for a tired 4.0 that's
> run fine for 160,000 miles. I did look at swapping in one of the HO
> engines from a wreck a while back but that's still a lot of work for
> what would not be that much of an improvement over the one I'm running
> now with the Rennix (Rennault-Bendix) computer. The only way I'd look
> at swapping the computers would be if this one died and I couldn't
> find another one in the boneyard.
>
> --
> Will Honea

one other possibility i didn't think of earlier is maybe the Mopar
Performance computer for the Renix system? Those aren't made by D-C
anymore, but if you are persistent, you might find one on ebay... i did
it cost me about $150. Of course, I'm also building a long-rod stroker, so
the computer may do more for me than it will for a stock engine.

(wow, my first bottom-post )

Now THAT one I have never heard of. I do know that the doesn't seem
to be any source besides the boneyard for replacement Renix boxes. I
might be interested in one of those if only for the built-in
diagnostic capability.

On Tue, 1 Jun 2004 23:21:24 UTC "Chuck Bremer" <cbremer@*hotmail.com>
wrote:

> one other possibility i didn't think of earlier is maybe the Mopar
> Performance computer for the Renix system? Those aren't made by D-C
> anymore, but if you are persistent, you might find one on ebay... i did
> it cost me about $150. Of course, I'm also building a long-rod stroker, so
> the computer may do more for me than it will for a stock engine.
>
>
>
> "Will Honea" <hwj25(remove this)@qwest.net> wrote in message
> news:[email protected]...
> > On Tue, 1 Jun 2004 07:37:28 UTC [email protected] (James Morrow)
> > wrote:
> >
> > > hey everyone! got a question for all you jeep gurus out there... i'm
> > > sure that someone can answer my question for me. ok, i have an 88
> > > cherokee with the 4.0 in it. now i remember a while back when i was
> > > just searching around reading articles on the internet someone said
> > > that the only difference between the regular 4.0 and the high output
> > > was the computer? the old was made by bendix if i remember right?
> > > anyways, in the same post i read that when they switched over to the
> > > high output jeep offered a mopar upgrade kit to turn the old 4.0 into
> > > the HO. i went to my local jeep dealership's parts dept to talk to
> > > them, and they said that they haven't heard of it and if it does exist
> > > then it was probably made by an aftermarket manufacturer. however, he
> > > didn't seem like the smartest guy in the world and he didn't even
> > > bother to look for it so there might be a mopar upgrade. my question
> > > is have any of you ever heard of this kit? if it is a mopar part do
> > > you know the product number? if it's aftermarket who makes it? i
> > > really want to do this. have any of you ever done this before or heard
> > > of it being done? money isn't too much of a worry so im not too
> > > concerned with the cost. a friend suggested that i go to a junkyard
> > > and pull the computer and all the associated wiring of a newer
> > > cherokee, but i don't know if it's just that simple. any input would
> > > be greatly appreciated. thanks in advance!
> >
> > There's more to it than just the computer. They get what? 25? 40? hp
> > more out of the HO with a different head, new manifolds, some changes
> > to the throttle body, etc. etc. The computer is just part of the
> > change.
> >
> > I've never heard of a MOPAR drop-in replacement. I imagine that you
> > could fit the MOPAR MPI upgrade they make for the 258 to it, but
> > that's $2k or so - more than I want to consider for a tired 4.0 that's
> > run fine for 160,000 miles. I did look at swapping in one of the HO
> > engines from a wreck a while back but that's still a lot of work for
> > what would not be that much of an improvement over the one I'm running
> > now with the Rennix (Rennault-Bendix) computer. The only way I'd look
> > at swapping the computers would be if this one died and I couldn't
> > find another one in the boneyard.
> >
> > --
> > Will Honea
>
> one other possibility i didn't think of earlier is maybe the Mopar
> Performance computer for the Renix system? Those aren't made by D-C
> anymore, but if you are persistent, you might find one on ebay... i did
> it cost me about $150. Of course, I'm also building a long-rod stroker, so
> the computer may do more for me than it will for a stock engine.
>
> (wow, my first bottom-post )
>
>


--
Will Honea

im so glad you posted about that ecu chuck as it sounds like it
wouldn't be worthwhile to do the HO conversion. i did a little
snooping around and found out some info about it. Prod #4529334 right?
i even found a place where i can buy one thats never been used for
$450. which is nice bc i was expecting more than that for the HO
conversion. only problem i'm having is that i can't find any power
gain info on it. the only mods ive done are ram air intake, throttle
body spacer, borla headers, magnaflow high flow cat, and i chopped the
muffler. what do u think that i could expect to gain from the ecu with
this setup? i am also thinking about buying a bored out throttle body.
do you think that would help any? i know it's gonna hurt my wallet
though bc it says it needs premium fuel which is about $2.25/gallon
here now. obviously you have experience with the ecu since you own
one, so my other question is how hard is it to swap out? it says it's
for offroad racing applications so i doubt i am going to be able to
pass emissions with it. i still have quite a few more years until my
jeep is emissions exempt so i figure every year i will have to put the
old one back in before i go to get the tests done. any other mods you
know of for my jeep that will give significant power gains short of
major stuff (stroker,blower,etc)? anyway, please let me know if u have
any info about how much power i could expect to gain from it. thanks
alot chuck!

i've been running it on my stock engine ('87 4WD) for a couple of months
now, with the following conditions: it's my daily driver, and I use 87
octane, so I probably don't get as much benefit out of it as I could be. in
my case I wouldn't say that it gives more power, but it's more available
power... seems to be a little quicker from a dead stop, and will pull long
hills much better. I average about 14 MPG with the computer, 33" tires, and
4.56 gears with an automatic tranny. It gets a little better on the
highway- 16-17 MPG or so.

The research I've done on it states that it alters the timing curve and fuel
maps (injector pulse width, etc.). I've also noticed that it says 'racing
use only', 'not for towing', etc. Like I mentioned, I run 87 octane, and it
passed the CA smog check with no problems. I should mention that I failed
previously, and replaced the cat at the same time. either way, the
emissions were *very* low (well below average).

Installing it is not particularly hard, but it's uncomfortable you have
to kind of twist yourself under the dashboard (the computer is located
sort-of behind the radio, just to the right of your right foot/gas pedal).
when I get home tonight, i'll peek under the dash and get the part number
off of it and post here.

short of major mods (and what you've done so far), I've heard that the
long-tube Mike Leach/Mopar performance headers will get you good bang for
the buck. you could also port your head & intake, particularly the exhaust
ports.

Dino Savva has a great low-to-mid-buck performance site here (as well as
info on stroking & supercharging): http://www.jeep4.0performance.4mg.com/

have fun!
Chuck


"James Morrow" <[email protected]> wrote in message
news:[email protected]...
> im so glad you posted about that ecu chuck as it sounds like it
> wouldn't be worthwhile to do the HO conversion. i did a little
> snooping around and found out some info about it. Prod #4529334 right?
> i even found a place where i can buy one thats never been used for
> $450. which is nice bc i was expecting more than that for the HO
> conversion. only problem i'm having is that i can't find any power
> gain info on it. the only mods ive done are ram air intake, throttle
> body spacer, borla headers, magnaflow high flow cat, and i chopped the
> muffler. what do u think that i could expect to gain from the ecu with
> this setup? i am also thinking about buying a bored out throttle body.
> do you think that would help any? i know it's gonna hurt my wallet
> though bc it says it needs premium fuel which is about $2.25/gallon
> here now. obviously you have experience with the ecu since you own
> one, so my other question is how hard is it to swap out? it says it's
> for offroad racing applications so i doubt i am going to be able to
> pass emissions with it. i still have quite a few more years until my
> jeep is emissions exempt so i figure every year i will have to put the
> old one back in before i go to get the tests done. any other mods you
> know of for my jeep that will give significant power gains short of
> major stuff (stroker,blower,etc)? anyway, please let me know if u have
> any info about how much power i could expect to gain from it. thanks
> alot chuck!