99+ Intake manifold

[Bryan C.]

Originally posted by XJ Saga

Here is another individual report where someone swapped out the intake manifold to the newer style: "I just wanted to tell you guys about the updated '99+ 4.0L Jeep intake manifold I installed with a self-bored-out throttlebody. I felt a slight power loss off the line but once the engine hits around 1,500 rpm, it comes alive and hits the redline much, much faster. Now, since I don't have access to a horsepower dyno I just relied on my "ass-o-meter" and felt a noticeable gain in horsepower. I installed the intake on a '96 XJ 4.0L with a K&N filter and a Flowmaster muffler. I would definitely recommend the upgrade, but I have been asked many times what the actual horsepower gain is and I can only say that another magazine rated the gains at 25 hp."
--Bryan Cloward

It is interesting to find yourself being quoted in a post. I'm coming in late to this thread, but I thought I would like to say I saw the HP increase quote in 4wd&su in the 4word column. I do not agree with the claim, but that was the only "number" that I heard of.

I work at a Jeep dealer as a tech and have the oppertunity to dive alot of XJ's. I would have to say the fastest XJ is the 99 4.0l. 99 is the first year of the intake, but with the old tube style header, and distributor ignition. I also drove a bone stock 96 and felt it had more power than mine with all the modifications, I just blamed it on the gearing change to make myself feel better.

Once the coil on plug came out on the 00, DC also changed the exhaust manifolds, and in California, stuffed two small cat converters in place of the old header. I think the 00, and 01 models are underpowered, compared to previous years. I haven't driven the 49 state model 00 or 01 XJ yet, so I cannot comment on its performance.

As far as rated HP numbers being low, I agree with that. I recently heard at the local DC training center that the new Dodge Neon SRT4 HP ratings were about 30 HP higher than what DC had published, also mentioned was the new hemi 5.7l.

The power steering/tensioner mounting to the intake manifold changed in 96, so the intake is a direct swap in for 96 to 98 XJs. 95 and later will need to upgrade to the new style tensioner system, and more than likely need a new power steering pump and belt too.

Bryan Cloward

[XJ Saga]

Good deal. I like to see positive response from individuals quoted in magazines.

I agree with just about everything you have stated with one exception: the 00-01 4.0's are very likely not underpowered, I'm running 0-60 in the mid 6's with all of my bolt ons. In stock form it was already an 8 second XJ. The precats are too small to provide any restriction and the new exhaust manifold resembles a good aftermarket header.

[Dr. Dyno]

Originally posted by Bryan C.
[B]As far as rated HP numbers being low, I agree with that. I recently heard at the local DC training center that the new Dodge Neon SRT4 HP ratings were about 30 HP higher than what DC had published, also mentioned was the new hemi 5.7l.

Almost correct.
Stock High Output 4.0 Jeep Cherokees with an automatic transmission produce 150-155hp/190-195lbft at the rear wheels in 2nd gear. Assuming a 20% drivetrain loss, that equates to 188-194hp/238-244lbft at the flywheel. It appears that the factory correctly rated the horsepower output but slightly underrated the torque.
You're right about the SRT4's. They were rated at 215hp (flywheel) by the factory but most of them are producing more than that at the front wheels. The true flywheel output is more like 240-250hp.
The Hemi, on the other hand, appears to be overrated. A 5.7 Hemi Ram produces about 240rwhp so even allowing for a 22% drivetrain loss, that amounts to 308hp (flywheel), well short of the 345hp quoted by the factory

[Dr. Dyno]

I think that might have been an underpowered version of the Hemi that wasn't yet broken in. I found a dyno sheet of another stock Hemi in a Ram, and the nos. were 269rwhp @ 5500rpm / 288rwtq @ 4250rpm.
Assuming a 20% drivetrain loss for a RWD automatic, that's 336hp/360lbft at the flywheel. If we use the 22% figure, the flywheel nos. are 345hp/369lbft. That's much closer to the factory quoted 345hp/375lbft.

[Bryan C.]

My observation regarding the 00 and 01 was just just that, an observation. Maybe I'll take better notice the next time I drive 00 and 01 XJs. I still think a stock 99 will beat a stock 00, or 01. I have no doubt that 99 to 01 XJs are all faster than my 96.

Dr. Dyno, you seem to be much more knowledgeable than I about the HP ratings. Thanks for the correction.

I often wonder how my mods have helped or hurt the performance of my Jeep. I guess you just keep going till you get it all dialed in and working together correctly. Oh the joys of Jeeps.

Bryan

[lunghd]

Originally posted by jack SF
to answer czb83. the 99 intake bolts up directly to the 91-98 head. but you need the steering pump and belt tensioner out of a 95 or newer jeep. wrangler inake and pump set up works in xj too. i got a whole set up from a 2000 tj.

(edited)
Quick clarification, if possible:
Does this apply to non HO / 'Renix' motor accessories (incl. power steering pump) as well?

My stroker has a '90 block, '93 head and a y2k intake.

I'm trying to retain my old non HO / Renix accessories if possible with this new intake.
I don't have a problem w/ swapping to the later power steering pump, belt & tensioner but dunno if the tensioner will work w/ my existing a.c. compressor & alternator?

Any input would be appreciated.

[jack SF]

the 91 and newer dont have an egr port like the pre 91, so you wont pass visual smog.

the throttle body and all sensors are different, but i have seen an adapter for sale that would take care of that.

i am not sure about this one, but i think that the 91 and newer heads are a little different. the intake might not line up axactly with your old head, maybe you could just put on a head from a 91 or newer. double check on this.

it does not seem that its worth doing after all those problems. jack

[lunghd]

Originally posted by jack SF
the 91 and newer dont have an egr port like the pre 91, so you wont pass visual smog.

the throttle body and all sensors are different, but i have seen an adapter for sale that would take care of that.

i am not sure about this one, but i think that the 91 and newer heads are a little different. the intake might not line up axactly with your old head, maybe you could just put on a head from a 91 or newer. double check on this.

it does not seem that its worth doing after all those problems. jack

Not sure if ya was posting in response to me or not, but here's some additional info I left out:

By "renix motor" I was referring to my donor block.
I'm building a stroker from the ground up - non-HO block, HO head, HO intake, HO throttle body w/ Renix TPS, HO header with the non-HO EGR tossed just as far as gravity & my arm will allow.

Got all that covered either in the garage, at the machinist or on the way... what I'm trying to figure is what kind of power steering pump I'll have to run - My old one if I can keep the old bracket w/ the y2k intake; or a new pump set up if the belt & tensioner will work w/ my old 'renix' accessories.

[jack SF]

yes lunghd i was replying to you. you should just get the whole set up from the donor jeep. the pump, bracket, tensioner pulley, hoses and all the bolts. if i remember right than the pump bracket and tensioner bracket are 1 piece. i think it might be possible to reuse your existing pump with a little work but i did not want to waste my time with a pump thats over 10 years old. just get the whole thing from the donor jeep. jack

[lunghd]

Originally posted by jack SF
yes lunghd i was replying to you. you should just get the whole set up from the donor jeep. the pump, bracket, tensioner pulley, hoses and all the bolts. if i remember right than the pump bracket and tensioner bracket are 1 piece. i think it might be possible to reuse your existing pump with a little work but i did not want to waste my time with a pump thats over 10 years old. just get the whole thing from the donor jeep. jack

Gettin' parts from all points of the compass so there's not a 'donor Heep' to eyeball the setup on or to rob all the parts together from. (New pump goes in regardless - just trying to get the right one the first time.)

Thanks!