Quote:
Originally Posted by Smoove
I swapped out the manifold and injectors on my ZJ from a 00 XJ, and I wouldn't recommend it. It wasn't a significant expenditure of time, becuase wrenching with friends allowed me to swap exhaust manifolds in under three hours, and the cash outlay wasn't bad ($150), but the gains were simply not there. It increased my 0-60 by .01s, my mpg by.2mpg (measured at 0, 500, 1000, 5000 miles) and no seat of the pants gain. The manifold was designed to use airflow more efficiently under 2000rpm's, and is suspected that it needs the matching head and internals to see the "15hp) gain.
YMMV
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One thing that will help incredibly is additional plenum volume. Not sure what kind of options there are for jeeps though.
I had the worlds biggest POS manifold on my 97 Civic. It was so small, had the plenum volume of a hacky sack and tiny runners. I swapped the manifold out for one from a SOHC Vtec engine (D16Y8 96-2000 EX engine) which had short, wide runners and a huge plenum. It was cleaned up with a little bit of porting (don't worry, never ported too much) and with no other mods or changes.
The off the line power was more robust (still a little 1.6L 4cyl though) but the extra capacity in the manifold allowed a much deserved increase in the top end. Best thing to do is have a well matched system. A high flow exhaust won't do much, if the engine is still straining to suck air in through a straw. Keeping things within the same desired and tuned range (exhaust, intake, heads, etc.) allows maximum velocity, maximum scavenging effectiveness which increases the VE and efficciency of the engine.
Now isn't that what this site is all about
