4.0L High output

[elcapitanmas]

Hey all, new to the site, just offed my toyota for frame rot issues and am looking at a cherokee sport. Can anyone tell me the difference between the 4 liter and the High output version, hp differences torque differences? Just wondering if its really worth searching for an HO. Thanks

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[SteelHeadz]

Slight difference on the camshaft lobes and mostly computer software in the PCM was changed. Some differencen on the engine wiring too for the sensors. EGR valve and knock sensors were taken out but some sensors were added to increase response and performance for the H.O. 4.0.

[elcapitanmas]

so for both off and on road performance, if an HO can be found, thats the way to go. Anyone have any suggestions as to what years may be "better" than others? I have a buddy that runs a dealership and can pretty much bring in anything I want. So far it looks like its going to be 99 or 00.

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[SteelHeadz]

Dont forget that the engine wiring is going to be essential for the swap. If possible, also the H.O. PCM or since your friend is in a dealership, the existing PCM can be reprogrammed with the updated software from a non H.O. to and a H.O. engine.

[blown XJ]

91 through 95 are supposed to have the best stock head and exhaust manifold

[Bounty__Hunter]

I don't know the HP and torque numbers, but there were significant changes to the head that accounted for most of the performance. The intake runners had a more straight shot into the cylinders in the HO as compared to the 90º turn the intake shot had to take in the Renix setup.

[carnuck]

Originally Posted by SteelHeadz

Slight difference on the camshaft lobes and mostly computer software in the PCM was changed. Some differencen on the engine wiring too for the sensors. EGR valve and knock sensors were taken out but some sensors were added to increase response and performance for the H.O. 4.0.

The HO started in '91. Before that they were Renix EFI (which I prefer, because it's more adjustable) The HO has no EGR (1 point for HO) and the head breathes slightly better (about 15 ponies worth)
The difference between HO and Renix cam shafts is the timing was retarded at the cam, which lowered VE (volumetric efficiency) and curbed engine ping so they could do away with the EGR valve. Sadly, they did away with the knock sensor, which would maximize engine power by advancing timing till pinging was heard. (the bad part of the knock sensor was it would also cut engine timing if there was internal engine noises)
As noted, a few sensors were different. Most notably the crank position sensor and the notches on the flywheel/flexplate. They do not interchange.

The biggest gains in power of the HO over the Renix were due to the much bigger injectors, and moving the cam timing, which also moved the power band into the higher RPM range.

	Crank position sensor A crank sensor is a component used in an internal combustion engine to monitor the position or rotational speed of the crankshaft. This information is used by engine management systems to control ignition system timing and other engine parameters. Before electronic crank sensors were available, the distributor would have to be manually adjusted to a timing mark on the engine.