xjmafia

i had well still own a 88 cherokee with the renix 4.0 but this week i picked up a 92 with the 4.0 h.o motor. which motor is supposed to be the better set up? i hope i dont regret the purchase lol

5-90

Mechanically, they're the same engine. Some revisions were made for the 1991MY to the cylinder head and intake, but they were relatively minimal.

Fuel and ignition curves were changed with the transition to OBD, but those were also fairly nominal.

However, OBD-I was a farkin' joke. I've owned a couple of OBD-I vehicles, and they were such a pain to work on. The problem is that there was no industry standard for OBD-I - it was a set of standards defined by CARB, but there was a good deal of open ground between definitions by CARB and implementation by the manufacturers (which is why plugs are different, DTCs are different, methods are different, ...)

OBD-II is when SAE took over - and that's why they're standardised. The plugs are all the same, and are supposed to be in the same area. The data transfer specification was standardised, any OBD-II code reader should work with any OBD-II vehicle. The "0-series" codes were defined as standards - a P0300 is a P0300 on any OBD-II vehicle (the "1-series" and less common "2-series" codes are "vendor defined," and generally for minor functions that have little to nothing to do with emissions or core driveability.)

However, I cut my teeth on cars made in the 50's, 60's, and early 1970's (electronic control didn't become common on domestic vehicles until 1974, import vehicles around 1980.) I'm used to doing my own thinking, and still can't quite trust OBD. However, I find OBD-II is a bit more reliable than OBD-I.

Given a choice, RENIX is my favourite - since most troubleshooting can be done with a DMM and your noodle, the system is more adaptable to changing conditions, and the programming is open-ended. OBD-II would be my second choice, because it makes more sense than OBD-I. OBD-I is something I try to avoid.

xjmafia

anyone else wanna chime in

cruiser54

I agree whole-heartedly with 5-90. The HO was not magic by any stretch of the imagination and was really a marketing ploy by Chrysler that still hangs around like an old wive's tale.

Only 8 more HP than the last version of Renix, no more torque, and the HP was only at higher RPMs.

xjmafia

not worried about any gains, just hoping there isnt any flaws compared to my 88

xjsnake

No flaws. No worries.

Chickenfloss

From what I understand, the heads were just reworked a little along with the inclusion of fuel injection. You might get a little better take off as a result vs carburetor. I don't know how bad it is on jeeps, but on my 1980 C10 with a 4 barrel quadrajet when you take it more than 45º in most angles it dumps gas and dies, with injection you wouldn't have to worry about it unless you are low on fuel and the gas washes away from the pickup so FI is a plus to me. However, on the same ticket when something goes wrong it's much easier to diagnose on an old motor.

As far as OBD-I vs OBD-II I haven't run into any problems with either myself. Yes the latter is standardized much better, but if you have a the internet or a repair manual for the vehicle you own you will know what that code means. Many vehicles have some way to get the codes yourself as well without getting the scanner. My ford probe with OBD-II needed a jumper in the diagnostics box, and I recently learned thanks to this forum that my jeep with with OBD-I can me codes by just turning the key on a few times. Having 1 scanner to fit all is nice though...

89 xj stroker

Transition from renix to ho did not include fuel injection, renix jeeps have fuel injection.

1991 white

never had anyproblems

Chickenfloss

Interesting, I always assumed pre H.O. was all carbed. Should have done my homework on the renault bendix injection. So really..not much of a benefit then :P

Firestorm500

I have an '87 Renix and a '92 HO.

There is a lot of power difference between the two.

IIRC, the '87 has about 169 hp and the '92 has about 192.

You can really feel the difference. The '92 pulls harder, passes easier, and climbs hills better.

But the '87 gets about 3-4 MPG better.

The electronics are not an issue with either one.

cruiser54

in 1987, Renix was 173, 88 it was 177, 89 and 90 it was 182 horsepower. HO was 190.

Your HO has an 8mm bigger throttle body, better header and a bit more sophisticated fuel injection system.

Want your Renix to run stronger? Get a 60mm throttle body on there, use a decent header, and/or get rid of the "crush" in the exhaust pipe right after the manifold.

austinjoe13

RENIX!!!

generalcrawl

either way they are both i-6 and you cant go wrong with that, i love my h.o. though

Firestorm500

Why is the "crush" there?