Jeep 4.0L info
The difference between the 4.0L and the 4.0L H.O. is a combination of cylinder head design, fuel injection type(from throttle body - renix- to Multi Point Injection), and computer tuning.
The 4.0L (standard) ended production in 1991, when the 4.0L H.O. came out. Though the "high output" was later dropped, it is still the high output version.
As time went on, it's power increased from 180 to 190hp, in all but the wranglers. Due to its more restrictive exhaust the YJ and TJ, took more fine tuning over the years to develop 190 hp. I don't remember the years that everything took place, but you can probably find it online.
As far as I know, no 4.0s came from the factory with more than 195hp. I spoke with a jeep engineer who mentioned in some of their test, they had the 4.0L getting 300 hp by playing with computer tuning, but the MPG suffered greatly.
Sometime around the 99 year model the 4.0 came with a "dual plane" intake, instead of the traditional straight runner. This occured when coil packs replaced the distributor. I believe this combination yielded more torque in the grand cherokee.
Originally Posted by countryjeep
Wait a second...the 4.0L H.O. shows as being 190hp on the Car & Driver review of the Jeep Cherokee. These specs compy with Comanche specs also. The 99' and up 4.0L's stayed the same, with the exception that the regular 4.0L's above 99' were upgraded to 190hp and the 4.0L H.O.'s were upgraded to 215hp.
Or did they miscalculated horribly?
Did they still make the "H.O." after 99? I thought that was discontinued prior I could use an extra 25 ponies in my TJ
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