Difference between yj 4L and xj 4L??

[athletic99]

Okay, I just bought a '92 yj. This is my 3rd Jeep. I had a CJ an XJ and now a YJ. What I want to know is.... My XJ had the RENIX engine circa 1989. It had 177bhp. Now, the '92 YJ has the newer 190bhp?? I know all of the power is down low in the rpm range with the yj but I kinda like the more broader power of the RENIX. What are the differences between the current XJ and YJ engines? I might want to try the broader power in the YJ to see if I like it better. Is it just timing and or cam differences? Any input will be appreciated.

[Bender]

In 91 the 4.0L was changed to the HO version where the intake manifold was re-done for better flow as well as the throttle body. The fuel injection system was also changed slightly with different injectors as well as a new computer system.... I think the heads might have been tuned a little as well. These mods raised the torque curve by about 500 rpms or so although the peak torque changed very little. Since HP is a function of torque and engine rpm this raised the HP figures from the mid 170's to the high 180's. The low end grunt of the old non HO 4.0L was better while the HO version really showed it's colours at higher rpms (high for jeeps at least) due to the increased air flow. Unless you're in need of a rebuild it wouldn't be worth it to swap from any version of the 4.0L to another version. Especially swapping in an older one. Use that money to upgrade you current engine as some very simple bolt on's can get your 4.0L up to 205hp and 240lb/ft of torque fairly easily.

I'll probably see you on the trails in southern ontario someday. Look for a custom doorless, locked and lifted XJ on 33" swampers.

Cheers!

Bender

[athletic99]

I totally appreciate the info Bender. But what I'm having trouble with is the YJ power range is so low that I don't feel it is taking advantage of the full range of the engine.
Let's say you drive an HO XJ, then you take an HO YJ for a spin. The "powerband" is so different. The XJ will kick the YJs ass everywhere. With the XJ there may be a bit less bottom end but it has a much fuller range of power throughout the rpms. The truck can easily fly at 100mph. Try to do that in my stock YJ and forget it! I'm doin Fred flinstone after I hit 80Kph just to get it to 120Kph. What I want to know is, what do I have to change on my YJ to get the "powerband" of an HO XJ.
BTW I sold my '89 Grey XJ to be a YJ guy :):)
Is your XJ Dark Green?

[IcemanK2]

This does not make sense to me. The same engine in two different vehicles will obviously preform better in the lighter vehicle. It does not make sense to say the XJ will kick the YJ's ass with the same engine under the hood.

It sounds like your 4.0 in you YJ is not up to par in other words not tuned. One other thing that they did do from the factory in the YJ was install an air horn in the air box to restrict the horsepower by 10bhp. The only other possible difference is in the gearing between the too but not the engine my friend.

My sister hads an XJ with the engine your talking about and my YJ with the 4.0 will smash the hell out of that thing with out even getting on it.

[Jaybird124]

Originally posted by athletic99
My XJ had the RENIX engine circa 1989. It had 177bhp. Now, the '92 YJ has the newer 190bhp??
190 HP? Are you joking? :winky: The newer XJ's had that and the wranglers had 181 till 2001 when DC changed the intake, ignition, cats, and exhaust. Where are these specs coming from?

[Jaybird124]

Originally posted by IcemanK2
This does not make sense to me. The same engine in two different vehicles will obviously preform better in the lighter vehicle. It does not make sense to say the XJ will kick the YJ's ass with the same engine under the hood.

It sounds like your 4.0 in you YJ is not up to par in other words not tuned. One other thing that they did do from the factory in the YJ was install an air horn in the air box to restrict the horsepower by 10bhp. The only other possible difference is in the gearing between the too but not the engine my friend.

My sister hads an XJ with the engine your talking about and my YJ with the 4.0 will smash the hell out of that thing with out even getting on it.
The 10 HP didn't come from the intake. The XJ's had a better exhaust system than both the ZJ's, TJ's, or YJ's because of the way the pipe was allowed to be routed. The exhaust couldn't be routed in the same way on the YJ, TJ, and ZJ. :D

[athletic99]

It could be as simple as a different cam profile that would put the power on at a lower rpm. The YJ was built for crawling and towing and this could be why all the engines output is lower. Maybe the YJ I have has had this done for it ....I don't know. But I wanted to know if the factory made them any differently.
As far as the Hp rating I got of 190Hp was what the manufacturer was quoting it as for media purposes. I am VERY unfamiliar with the YJ that's why I put a (?) after 190Hp.

[wcjp]

Until very recently I had a 93'XJ and a 93'YJ. The YJ is pretty modified while the XJ only had a Rusty's intake. My 5spd YJ with 30,000 more miles would stomp my auto XJ. The YJ in mixed driving averaged 19-20mpg. The XJ was a commuter only. I drove 70miles roundtrip per day on the freeway. It averaged 17-17.5mpg. With all my mods and the increased weight and wind resistance the YJ should be a dog. Not true.