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99+ manifold in a 98?

I know that the 99+ manifolds are different from the 97-98's (something to do with increasing HP since it was decreased by some EPA mandate).

would there be any benefit to swap a 99+ manifold (or anything for that matter) in on a 98?

I'm broke, looking for work, and bored all day, so I'm trying to work on my Jeep and make it as good as possible, since when I go to grad school I won't have time, and the school is 7 hours away...

Thanks
 
I know that the 99+ manifolds are different from the 97-98's (something to do with increasing HP since it was decreased by some EPA mandate).

would there be any benefit to swap a 99+ manifold (or anything for that matter) in on a 98?

I'm broke, looking for work, and bored all day, so I'm trying to work on my Jeep and make it as good as possible, since when I go to grad school I won't have time, and the school is 7 hours away...

Thanks

I didnt notice any difference in power or mileage, but it does rev more smooth. If the manifold is cheap or free, it would be a nice project.
 
BEFORE wasting your money and sweat on a 99+ manifold, I suggest you read JPMagazine's article on 4.0 myths: http://www.jpmagazine.com/techartic...iter_engine_myth_busting_true_lies/index.html

The 99+ intake part is near the bottom of the page, but the other sections are very informative too.

well then that makes perfect sense. a waste of time I guess.

quick side note, the article refereed to many false myths as internet data, that is "reliable" (sarcasm)... yet, it's a internet article, so by their standards, should we trust their data?
 
well then that makes perfect sense. a waste of time I guess.

quick side note, the article refereed to many false myths as internet data, that is "reliable" (sarcasm)... yet, it's a internet article, so by their standards, should we trust their data?

Its actually an internet copy of their published magazine's article.

To trust, or not to trust, that is the question.
 
The 99+ manifold is superior. You might not see peak #s increase, but the shape of the power curve does increase. I can get them for $27 at my JY and anything at/below $100 shipped seems to be the current fair market price.
 
I would like to see the claim that it reduces power proven. I disagree with Joe, but I'm biased- I run the later style manifold on my DD.
 
I would like to see the claim that it reduces power proven. I disagree with Joe, but I'm biased- I run the later style manifold on my DD.

Follow the link to JP Magazine I posted earlier--their results, not mine!:cheers:
 
I mean something concrete like a dyno run- they had several problems with that XJ- bad O2 sensors, dead PS pumps- and they don't mention the manifold in any of the articles, other than to say it's a myth that it adds power. How do we know the XJ was in good working order when they tested? How did they test? Etc, etc.
 
I mean something concrete like a dyno run- they had several problems with that XJ- bad O2 sensors, dead PS pumps- and they don't mention the manifold in any of the articles, other than to say it's a myth that it adds power. How do we know the XJ was in good working order when they tested? How did they test? Etc, etc.

All good questions. I would certainly like to see some background data on the tests.

I read three of the Project Mileage Master articles and I don't remember them putting a 99+ manifold on in the articles.

Maybe I'll "letter the editor" for some more info.
 
Coming from a turbocharged world, I'd have to say it doesn't sound accurate. Of course I haven't researched it much myself and I haven't found any bench flow tests. I've read that they reduced the power output on 99+ due to emissions and the intake manifold was redesigned to bring that power back up. Of course the turn of the century also brought in new innovations in emissions that pretty much reduces little to no power.

Also IMO, I believe the curved runners give it better reponse and maybe a bit more torque. This is assuming the runners are the same volume. I don't know about the plenum size though. They debunked that with the throttle body spacer.
 
Coming from a turbocharged world, I'd have to say it doesn't sound accurate. Of course I haven't researched it much myself and I haven't found any bench flow tests. I've read that they reduced the power output on 99+ due to emissions and the intake manifold was redesigned to bring that power back up. Of course the turn of the century also brought in new innovations in emissions that pretty much reduces little to no power.

Also IMO, I believe the curved runners give it better reponse and maybe a bit more torque. This is assuming the runners are the same volume. I don't know about the plenum size though. They debunked that with the throttle body spacer.

Yeah, I put a spacer in when I put the 31s on with 3.07 gears as a stop gap until I could locate some 3.73s. Didn't see much of an improvement, and I've been too lazy to take it out.
 
I've read that they reduced the power output on 99+ due to emissions and the intake manifold was redesigned to bring that power back up.

this is what I've read...

Also IMO, I believe the curved runners give it better reponse and maybe a bit more torque. This is assuming the runners are the same volume. I don't know about the plenum size though. They debunked that with the throttle body spacer.

this is what I figured, it seems to allow better flow, and therefore more power (at least it would be capable). of course if the down pipe, exhaust, etc. isn't larger, would it make a difference.

I've been reading more and more, esp. about throttle bodies and mods to increase flow of things, but when it comes down to it, it's like a garden hose... you can attached the largest garden hose EVER to a normal facet, and at the other end a normal nozzle; but the large hose is limited in it's capability because the facet and nozzle can still only handle so much.

Does this make sense? Sorry I like analogies...
 
this is what I've read...



this is what I figured, it seems to allow better flow, and therefore more power (at least it would be capable). of course if the down pipe, exhaust, etc. isn't larger, would it make a difference.

I've been reading more and more, esp. about throttle bodies and mods to increase flow of things, but when it comes down to it, it's like a garden hose... you can attached the largest garden hose EVER to a normal facet, and at the other end a normal nozzle; but the large hose is limited in it's capability because the facet and nozzle can still only handle so much.

Does this make sense? Sorry I like analogies...
I understand what you're saying. And it's true to a certain extent. N/A exhaust needs backpressure for torque, so they limit the size of the exhaust pipe to maybe like 2.5". I'm not too N/A savvy but my neighbor who owns a LS2 powered GTO increased the length of his exhaust for more torque. Although it would make more sense to have the least backpressure and get more air/fuel charge stuffed into the combustion chamber.
 
IMHO any gains from intake improvements--larger throttle body, better intake manifold--are going to be limited unless you do something about the cam, valves, and exhaust.

The flip side of the coin, again IMHO, dollar for dollar improvements to the exhaust will gain more for you even without intake/cam/valve changes.
 
i remember reading an issue of jp magazine and it said expect 30 horses from the newer style intake manifold, and now they claim it actually loses hp? ill dig it up and double check.

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