curious about 99+ intake

whats up guys. ok so i have heard alot about using 99+ intakes. i have an 89 xj with the renix 4.0 will the 99 up fit on my renix? also how do i go about the swap? what is all involved? i know it cant just be a straight bolt in. i know u have to mod something. also what are the benefits to using the 99+? why are they the hot ticket? and i have heard about running neon or mustang injectors. just want to get up to speed on this. thanks

Some say they feel the difference; some say they don't.

JP Magazine said it lost HP on their 4.0 in the Mileage Master XJ series: http://www.jpmagazine.com/techartic...iter_engine_myth_busting_true_lies/index.html

You will have to modify the Renix TPS to work with the HO throttle body (or pay Hesco $150 for their adapter--a bit much). Check out stealth919's post in this thread, it is pretty slick: http://www.naxja.org/forum/showthread.php?t=1003642

Personally, I wouldn't do it on a stock engine. Maybe a stroker build with a cam.

I would REALLY like to see some before and after dyno numbers for this mod.

Your 2686 renix head has big intake ports that the 7120, 0630, and 0331 intake manifolds will have a hard time covering. Those manifolds have a 4-bolt mounting system for the tb and the renix has a 3-bolt mounting system(some make an adapter plate to use the renix tb). You can use the newer tbs, but will have to modify the renix tps to mount to the newer tbs(hesco sells a $135 adapter if you don't want to make one). In all seriousness, if you want more air in, get your TB bored to 60mm by Jeff@ www.strokedjeeps.com, cause that is the current bottleneck, not the manifold.

joe_peters said:

I would REALLY like to see some before and after dyno numbers for this mod.

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working on it. ive got my '99 intake off of my old stroker motor. just got to find a dyno in the middle of s$&% hole michigan.

VAhasnoWAVES said:

working on it. ive got my '99 intake off of my old stroker motor. just got to find a dyno in the middle of s$&% hole michigan.

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Looking forward to seeing those comparisons!!

The general consensus is that it is not worth the effort for the small benefit.

I did the swap on my '97 and it was really straight forward and only took about 2 hours. The new intake bolted right up, and the only modification I had to do was switching around a few sensors and extending a couple vacuum lines.

I did the swap in conjunction with an air tube and cone filter, and notice that the engine seems to rev more freely. I don't have any figures, as everything is via the butt dyno, but for the cheap cost and the ease of installation, I'd say it was worth it. Also saw a slight improvement in MPG on the highway, so I'm close to my numbers before I lifted my XJ.

i was wondering where one would find a 99+ intake, would a junkyard or the dealership be the only 2 places that would be able to get one? i've searched all the major aftermarket manufacturers and none of them make a manifold for the 4.0 HO.

is the gasket different from a 96 than a 99?

98XJ40231 said:

i was wondering where one would find a 99+ intake, would a junkyard or the dealership be the only 2 places that would be able to get one? i've searched all the major aftermarket manufacturers and none of them make a manifold for the 4.0 HO.

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? :dunno:




is the XJ '99 intake the same as the one on the '99 TJs (or a certain era)? that may expand options, but (as with anything in the TJ world) id imagine itd be pricey.

I'm fairly certain it's the same intake. I know that the 2.5L intake manifold changed style at around the same time (might have been off by a few years, not sure) and I've seen the updated style on TJs.

Since it is the same part, anyone sane will sell it for the same amount. Anyone who doesn't think it's the same part will probably put a gold plated TJ price on it.

I know multiple people who have reported little to no butt dyno improvement after installing a 99+ intake however.

Wouldn't that be the same intake as the WJs as well?

I think taking the taper out of the TB had more of a pronounced effect than anything else, especially in the bang-for-the-buck category. It would love to see dyno numbers for a lot of the more common "budget" mods; intake swaps, downpipes, cats, cowl snorkels, open element filters, etc.

I agree this mod will do little for a NA 4.0, but it helped the stroker. it's here w. dyno results:

http://www.jeepstrokers.com/forum/viewtopic.php?f=5&t=387

hubs97xj said:

Wouldn't that be the same intake as the WJs as well?

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Yes, it is the exact same intake manifold as the WJ one. I pull all the 99+ manifolds I find in the junkyards and sell them to an engine builder friend of mine.

I've pulled intakes from a 99+ XJ and a WJ in the same day. And they are identical, right down to the casting number.

All these clowns who report no "butt dyno" results from a performance mod I take with a grain of salt - read ignore. The butt dyno is a notoriously inaccurate and uncalibrated instrument. If you can't afford a $50 dyno run w. before and after Torque/HP printout curves, don't waste everyones time posting your BS opinions. This is not directed to anyone in particular, but I think accurate proven results are necessary on any performance mod and will most benefit the community considering a performance mod.

There are before and after dyno graphs on the forum somewheres for a '99 intake on a stroker.
The is another report somewheres that you receive a 3 HP increase on a stock 4.0L. For the expense of a '99 intake and replacement gaskets I don't think this small increase is worth the expense.
The consensus is that on a stroker engine the performance increase is worth the expense especially if you install it with a new engine.

I think JP Magazine's article stating that it actually decreases HP on a stock motor has swayed a lot of people who haven't put their junk on a dyno.

hubs, you have no idea how much your signature has been confusing me since last evening.

Just figured it out :dunce:

hubs97xj said:

I think JP Magazine's article stating that it actually decreases HP on a stock motor has swayed a lot of people who haven't put their junk on a dyno.

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x2. I don't get how you can decrease the HP though. Sounds like they are smoking something. When they went to the 0331 head and two pre-cats on the manifold, they had to make up for the decrease in power from the added exhaust restriction from the new emissions standards. The newer intake put the numbers back up where they should be. If you look at the specs on HP and Torque for a 2000+ motor vs. earlier you will see they make the power at different RPMs. If I recall the peak torque is at 3,000 RPM on a 2000+ motor while earlier ones are at a lower point (around 2100).

The 99+ intake won't necessarily increase HP that much, maybe 3 HP like stated above, but its main improvement will be changing the torque curve a bit. Many who do this mod claim more midrange torque. For JP to state that it caused a loss in HP is just stupid. Even highschool mechanics students know that an engine is like an air pump. The better an engine can "breathe" the more efficient it will be. They wouldn't spend the money to redesign the manifold if it wouldn't change the power output and make up for the more restrictive exhaust.

The question about it being worth it is up to the owner of the Jeep. Would I change my manifold for more power? Probably not considering the gains are not really worth the work in my opinion. You could get about the same from a bored throttle body. If I had an older motor I was rebuilding out of the jeep and had the option to throw on the 99+ intake I would though.

ok sounds like i will not f with the 99+ swap maybe just bore the tb in my renix. now my other ? that really hasnt gotten answered is injectors. what do most of you run in the renix. i dont know anything about them. some guys say to use mustang some say neon. i would like to use the neon. and do u have to change the fuel pressure regulator? ive heard yes and no. i just want to do my swap correctly so the engine will run smoothly. i just had it rebuilt and it hasnt even had its break in oil change yet. and can i run the neon or stang injectors after i bore the tb? does this help with mileage? i dont know anything about engine performance and how it all plays into each other and some schooling would be very appreciated.