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339 Posts
Discussion Starter · #1 ·
On Saturday I installed the 08 Manifold along wth the adapters from Air Ram.The twist is that this is not going in a Dakota or a Ram...but a Jeep Grand Cherokee. To my knowledge I am the first to successfully install it in a 99-04 GC. Some have tried but failed. Unlike a Ram, Durango, or Dakota, it requires irreversible modifications to do.

We started at 2:15, got a plug we needed at Home Depot. we got back to the house, started pulling the coil packs and related hardware. We made amazing time considering we were bagging everything together at this point- all in all the teardown took only about 30 mins.

We had a minor issue with pulling the bolt holding the manifold down in front of Cyl #2 but were able to get it out with some force. We went to go pull the manifold, and it came about halfway out, but it wasn't even close to being free to pull out. it appeared that the alternator, AC compressor, and the fuel crossrail were all interfering. Mainly the crossrail, which had limited flexibility.

Given the shape of the Jeep's firewall we felt that if we cut part of the cowling that it would give us enough room to pull the manifold out. Didn't happen. However, that same cut was the only way we would have been able to get the 08 manifold in. So in the long run, it was necessary.

After 2 hours or so of struggling (3.5 hours in total at that point), we decided to finally remove the alternator, compressor, and possibly the fuel rails. the AC and the alt were easy....the fuel rails did NOT want to budge. after another hour of cursing and carefully prying, we were able to pull the rails. 5 hours, and we finally pulled the manifold out.

The manifold went in easily and seems better placed in the bay, but by that point we had a ton of hoses and sensor plugs scattered throughout the engine bay. Since we worked non-stop, fatigue was starting to set in, so we both took our time and split the tasks up whenever possible. There was alot to re-connect and to modify since the 08 manifold has different provisions than the 02 manifold that I have.

So we are buttoning everything back up- the manifold is secured, the coil packs are on, the grounds are attached, adapters are secured to the manifold, the TB is about to be bolted up...and then it hits me. there is no room for the throttle/cruise control bracket!!!! ****. Long story short I tore off a large chunk of firewall padding and just barely made it fit. It still does not sit flush with the adapter, either I need to cut the cowling further, shave or grind down the bracket.

The whole project, including short meal/drink/texting breaks, a trip to the parts store, etc etc took 10 hours. Hannes (my buddy helping with the swap) and I both agreed that if we ever did this swap to another Jeep, it could be done in about half that time now that we know what to look for. It's a very big project.

I dont know if you can embed video here, but heres some videos. Keep in mind this is just after a few miles after a PCM reset with the same tune I was using for the 02 manifold. I went from about a 12.5 AFR up top to 14.2 so there is room for improvement.

What it started out as...I coated it with flat alumnum VHT flame proof and the it looked likethis

Then it came time to tear shit up...this is what we started with

I think at this point the manifold was loose and ready to be pulled

This is after pulling the fuel rails, compressor, altrnator, etc etc etc and the old manifold is out

Same time , just closer up

Manifold is finally in

And this is with everything buttoned up together with a VERY VERY temporary PVC intake....I have a custom 4" ceramic coated intake I've designed myself ready to go but the sillicone couplers I purchased did not arrive in time.

Heres the videos.....I apologize for the low quality, I accidentally shot everything in low resolution...

http://www.youtube.com/watch?v=ihZhGmyciaM 1st crankup vid

It should also be mentioned that I am not tuned for this manifold. I am currently running a mostly dialed in (for an 02 manifold) 93 octane file from Sean Powell. AFR was previously 12.5-12.8 across the board, with a somewhat aggressive spark map.

After this manifold I need a major retune. This manifold will be on the edge of safe on a stock JTEC calibration, but for NGC I would highly recommend custom tuning. Superchips will not be enough for this modification regardless of PCM.

I have an 02 manifold, which is (along with 99-01) the worst flowing of all the 4.7 manifolds. 03-07 manifolds are not really much better. So I had the most to gain from this. I may have some WOT power loss off the line (I'm not sure- I need to verify this at the track), and the power seems to be a little soft from 2200-3000 (this may be in part due to becoming significantly richer- mid 11s ), but come 3000 rpm on it goes into a DRASTIC and unmistakable change in character. The intake literally starts screaming (It's loud all the time but now it is WAY louder) and there is a HUGE surge in tq. From 3000 rpms to 6000 it pulls like a freight train. I just came back earlier this evening from a little drive with a friend of mine who weighs 350+ lbs and when it switches over at 3000, even at a slow roll it sucked his ass into the seat.

With the 02 manifold, my tq curve stayed at peak from 3200 to 4200 rpms, and then nose dove. What this means in reference to the 1/4 mile is that with my 1-2 and 2-3 shift recovery being 3500 and 3900 respectively is that I was spending the majority of my 1/4 mile with a rapidly dwindling tq (and hp) curve. Now, I am spending far more time in the peak of my power band, with the power band being greater than what it was previously. Even without the tune there is no doubt in my mind that I am significantly faster than I was prior to the swap.

This is just my experience but before, with my TB and the 02 manifold and the SCT 93 tune, under a load I was seeing alot of weird AFR fluctuations (both lean and rich) and inconsistencies before it would go into open loop fueling. I thought that perhaps the HUGE inlet and 68mm blade (my own ported TB design) were skewing with the CL/OL algorithms. Now with the 08 manifold, under the same load, the same calibration now gradually makes a seamless transition from stoich to OL. OL triggering leads to AFR dipping down to about 10.7-11.3 AFR which is way too rich (it should be at about 12.5-13.5 at this throttle position), but that is an easy fix. For whatever reason the PCM is much happier with this manifold than the 02.

Thats all folks...Enjoy!
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Reactions: mthandt

4,140 Posts
great job. glad you guys were able to get it done...i just got your thread on this on one of the other forums last night

339 Posts
Discussion Starter · #6 ·
what type of gains are there supposed to be from this?
So far, I dropped about .3 in the 1/4 from swapping to the manifold and going from a plastic 3" intake to a insulated 4" intake (oh, and retuning via SCT). There is more in it- I'm gaining 18+ mph from the 1/8 to the 1/4, but I'm really no faster in the first 1/8 of the track.

The manifold alone is worth the swap, but I feel like I need a stall converter or a larger cam profile to make it work properly.
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