Jeep Intake Manifold Swap and Evaluation
In 1999, Jeep had to redesign many parts of the venerable four liter to meet increasingly stringent emission controls. Some of these redesigned parts of the engine were, but not limited to, smaller exhaust ports to heat the inline catalytic converters quicker (The original exhaust outlets were nothing to write home about and now are smaller), two inline catalytic converters in the exhaust manifolds (This in addition to the original, but more efficient catalytic converter in the exhaust system), revised camshaft timing to reduce overlap and duration, and revised computer timing maps. None of this is conducive to increased performance.
Jeep’s answer was to redesign the intake manifold, EXTENSIVELY, to make up for the power losses due to tightening emission regulations. This swap is increasingly becoming popular, but no one has actually tested the merits or demerits beyond, what I will refer to as the “Butt Dyno”. This is the purpose of this review and evaluation. To install the later manifold and actually find out what it will do on a dyno and what messes you get into with this conversion. Reports on the internet state that if you fit one of these manifolds to a earlier Jeep, without the different emission reduction devices, you get a 15 hp boost! Those running strokers even more as Jeep Speed mention a 25 hp gain on there race engines just with this change! Let’s see!!!
Basic baseline data of the subject test vehicle
1993 Jeep Grand Cherokee
My engine specs before:
Turbocity air intake
Removed 5mm taper on throttle body 60mm all the way through
Throttle body spacer 62mm
Port and polished head
LS1 valves 2.02 intake 1.60 exhaust – Detailed at the end of this write-up
FULL 2.5” exhaust all the way back
Carsound OBDII high flow cat
Custom homemade dual mode muffler
Stock style plug wires, cap, rotor and ignition coil
Stock fuel pressure of 43.5 psi (measured)
31x10.5 tires, which does affect a chassis dyno.
Only things that changed between the two dyno runs were:
The 2000 intake manifold
The 2000 injectors that came with the manifold
Hesco adjustable fuel pressure regulator for the 91-95 4.0L adjusted to the newer pressure, required of the new style injectors of 49PSI
I ground down the large bumps around the injector ports, to maximize air flow across all inlets to the engine. This will be discussed during this write-up.
Note, the local state safety and emission tests were performed after the installation of this manifold and injector change. The vehicle passed with flying colors. No detrimental effect to the ecology here!!
The new 1999 and newer style intake manifold is on the right. Note the MUCH larger volume and individual runners. The Renix on the left is shown for design reference.
Here you can see my 93 in the middle and the completely new intake manifold on the right. The runners are far more curved leading to the ports without the harsh right angled bends that the earlier ones have. You can also see that the plenum chamber which sits right under where the throttle body bolts is much larger.
“The old intake manifold took 2.6 liters to fill and the new one an 4.3 liters. A throttle body spacer only adds .076 liters you can see how much bigger in volume this new manifold is without the sharp bends in the runners.” (Picture above and text were borrowed from http://www.go.jeep-xj.info/HowtoIntakeManifold1.htm)
These are the number four to six from left to right, or center to outer ports, of the new manifold.
You will find a small lip from the machining process inside each port. This is not good for air flow and should be removed by grinding regardless of the further port grinding or not
Note the bosses or raised areas around the injectors. That is not an optical illusion, but the bosses around the injectors are different from Center as you go out.
The bosses on the center two ports (3 and 4) of the six-port manifold are very large and are somewhat restrictive of the port. The number 2 and 5 ports are less restrictive, and the number 1 and 6 ports are basically open.
I would assume this is some type of tuning for a flatter torque curve, and improve drivability, at the expense of upper rpm horsepower.
Now, how to test this theory?
Not owning a sophisticated manometer and the machine shop that did the valve work could not flow test intake manifolds, I decided to make my own monometer to check the relative flow relations between the intake ports.
I used my trusty two horsepower shop vacuum to pull large amounts of air through the individual ports and insert a plastic hose into the injector ports. Note, this method is NOT intended to provide an SAE factual flow data, but only to indicate differential differences between the intake runners to see if my concerns were valid. The hose was run to a bowl of colored water on the ground and the test was performed on top of my work bench. Note, placement of the plastic tube must be EXACTLY the same for each test or the resulting figures will vary greatly.
Vacuum from ports one and six pulled the colored water up only 6.875”.
Vacuum from ports 2 and 5 pulled the colored water up 7.375” or 7.3% more restriction than ports 1and 6.
Vacuum from ports 3 and 4 pulled the colored water up 7.625”, or 10.9% more than ports 1 and 6………NOW WHAT?
Grind the protrusions in the ports, around the injector outlets to equalize flow using the fore mentioned test procedure. BE VERY CAREFUL to not cut through the manifold. The bosses or protrusions have indentations in the runner of different sizes for these bosses. IT WOULD BE VERY EASY TO CUT A HOLE IN YOUR MANIFOLD. YOU ARE WARNED. I got them within 3% of the same flow and chickened out to cut more!!!
Power steering pump modifications
In 1996 Jeep changed the mounting bracket, power steering pump, and idler pulley for the power steering pump arrangement. For a 1993 this meant new parts and a new power steering pump.
This is a copy of the parts needed at the jeep dealer or junk yard to convert a 1993 power steering system to use the new intake manifold. Note, # 8, 9, and 2 are not necessary. You can reuse the old parts.
Part Numbers for the steering portion of the intake swap for pre 96 4.0L’s
Part number Dealer name for part Price at my dealer
4. 34202029 bolt-hex f 136c 2.95
5. 33002201 bushing-id 114b 3.35
6. 4792112 pulley 116e 20.50 (Normal ZJ idler pulley)
7. 6503230 spacer-bel 2.70
8. 53010148 bracket 15.50
9. 53010149 sleeve-ten 5.60
10. 6503198 bolt 8.75
11. Reuse yours or hardware store
Total for the power steering parts if purchased at dealer: $59.35
This new bracket becomes the way to adjust the belt tension and makes adjusting the serpentine belt tension MUCH easier than the original system!!! I also had to get a new serpentine belt part number 4060922 / 6PK2345 Goodyear Gatorback. It sort of sounded like I had a supercharger whine before the belt had time to break in, then the sound went away.
On the 93-95 ZJ’s the idler pulley on the new power steering bracket replaces the pulley that was below the air conditioner compressor, and the belt routing changes slightly but it was no big deal. When you remove the pulley below the AC make sure you put the bolt back in, it holds the AC bracket.
Assembled and installed power steering system
Final installed power steering pump assembly
After removal of the old intake manifold, loosen the remaining bolts to the exhaust manifold or, in this case the Banks header, which was previously installed. Replace the intake and exhaust gasket. Make sure that the new gasket holes line up with the intake ports on the new manifold. I have seen some new gaskets that are considerably smaller than the passages they are supposed to seal and this reduces air flow.
The bracket to secure the fuel lines as they pass under the manifold used a different bolt pattern on the earlier verses later manifold. I re-drilled the bracket to bolt to the 99+ manifold. Do not leave this out or fuel line leaks could occur from excess vibration over time.
Installed manifold with original throttle body. Some rearranging of vacuum lines was necessary, but that will be obvious. The intake air temperature sensor wires might need to be lengthened, but was not necessary on mine, but it was close. You must also use the throttle and transmission cable bracket from your original vehicle or the throttle and transmission might not work as before. The distance from the transmission control cable to the throttle arm MUST be the same as before for proper transmission function. This length is adjustable to some degree with a locking tab at the cable mount.
My jeep is equipped with an air / fuel ratio meter to watch the mixture for signs of lean running while we had the 2000 injectors installed, while using the 1993 fuel pressure regulator. Note that the 1993 fuel pressure was tested at 43.5 psi without the vacuum source connected. The new style injectors are to run at 49 psi in the newer Jeeps, for better atomization, I assume. I ran the Grand for three weeks at the lower pressure with no ill effects and no change in fuel economy. I wanted to see if the new injectors would actually aid fuel economy at the higher pressures due to better atomization. Above is the adjustable fuel pressure regulator from Hesco installed and reset to 49 PSI with the vacuum disconnected. This is how the dyno run was performed. I, to date have not seen much benefit in fuel economy with this new set up, but there was NO negative change in miles per gallon. What I would call the “Butt Dyno” did seem to feel a difference in response with the higher pressure.
FYI The original injectors will work and fit right in. If you use the new style injectors, you will have to modify the electrical connection and zip tie wrap the connectors to the new injectors. Note, you can buy separate new style plugs and change the electrical plugs if you desire.
Proof is in the Pudding, or in this Case, the actual before and after Chassis Dyno Runs
Note, the original runs were performed with a modified fan clutch to insure cooling in the hot summer. Both runs were performed with this modification to insure good data. Then a second test with the fan clutch reset to standard conditions.
The Grand Cherokee was run normally in city driving for one month, to make sure that there were no bad effects from this modification. I really did not see much increase in gas mileage that has been reported on the Internet, but there was no decrease either. The engine feels much stronger above 3000 rpm, but I had to know the real effect.
Setting the Grand up for the acid test at Carboy in Houston, Texas,
Rear view showing the rear wheels on the dyno, straps to hold it secure and I paid extra to have the exhaust gas analyzer running during the tests to show the air / fuel ratio.
Result on Rear Wheel Horsepower on actual chassis dyno.
HP GAIN: 26.9 Rear wheel HP
TQ GAIN: 19.7 Rear wheel TQ
Original dyno test averaged 119 HP. New test is 146.4 HP. Torque has increased from 154.6 to 170.2 lbs.
It was interesting that the engine ran leaner, but still safe.
You will note the higher power readings on the final test. We released the spring on the fan clutch to unload the fan for the last run and gained almost 12 HP more.
Note, this modification is necessary to completely stop the heating problem in South Texas on a Jeep four liter. I will detail below.
As previously stated, we had the vehicle state inspected, which includes an exhaust analyzer with no detrimental effects at all.
This is the original and base line dyno run showing rear wheel horsepower. Again note, this test also uses a modified fan clutch and the conditions of the vehicle as shown at the start of the review. It is not indicative of all Grand Cherokees, but is the baseline for this evaluation.
here is a better dyno sheet to show the difference with only the before and after on it!
This is the exact same vehicle as described, except the new style intake manifold, stock 2000 injectors and correct stock fuel pressure for those injectors. The max power of 146.4 is with the modified fan clutch to keep the dyno run tests consistent. The 158.9 number is with the fan clutch basically reset to stock conditions, which will not cool in high summer temperatures with the A/C and traffic, but I wanted to see the actual effect of this fan modification also.
Is it worth it?………YOU BET!!!
How to Keep a Four Liter Cool with the A/C on in traffic
During this test we were running a modified fan clutch to stop, once and for all the overheating issue in traffic and the A/C on. I will detail below both for a Grand Cherokee and a Regular Cherokee.
There have been several posts about overheating and ideas how to stop. Most of which I have tried, including electric fans, cleaning the radiator with every known chemical, professional radiator cleaning, different fan clutches, larger radiators, louvers in the hood, ect. Still in stop and go traffic the engine would get hot. I am determined to be able to run the A/C full blast in heavy traffic in high humidity and hot weather above 100F!!!!!!!! Just call me fussy but it’s hot in Texas.
I had previously changed the original fan clutch to a new heavy-duty design clutch. While this helped, it still was not the solution.
This is the original setting of the thermostatic spring as purchased from the Auto Store. As the spring heats up, the center shaft, which is actually a valve to restrict oil flow, rotates counter clockwise. The more it rotates, the tighter the fan locks up.
You note that the spring can be removed from its locked position. In this position, the clutch is almost locked solid, as we have rotated the center valve shaft the full 90 degrees counter clock wise.
What I did is I cut the spring down so that the preset is now 45 degrees greater, or more toward the locked position to increase air flow. A small drop of glue secures this position.
Result, more noise, 12 extra horsepower to drive, per the dyno test, but NO OVERHEATING AT ALL!!! When we unlocked the clutch for the final test, all I did was pop the spring out and rotate clockwise to the maximum setting, thereby basically unlocking the clutch. This position actually works well below 85 degrees ambient and will be left there until next summer.
Standard XJ Jeep Cherokee Heating Solution
Tried bigger four core radiator, cleaning, electric fan, ect. NOTHING works in high humidity, high temperature and stop and go traffic with the A/C on!
My solution is to ELIMINATE the fan clutch all together!
The XJ fan is only 12-13 inches tall due to the tips for better efficiency.
I removed the fan clutch and installed an old fan clutch eliminator that I had laying around for direct drive.
Note, DO NOT DO THIS ON A GRAND CHEROKEE, the fan is much larger, could fail, and/or pull a rediculus amount of horsepower.
Here you see the fan clutch eliminator before the original fan clutch is removed and discarded. The above modification to the fan clutch, as I did on the grand Cherokee might work, but due to the small diameter of this fan, I doubt it.
I do not remember who made this eliminator, as I have had it for a while. It might be possible lock up your clutch and get similar results.
Result…OVER HEATING IS GONE PERIOD!
As this evaluation of the intake manifold is not being done on exactly a stock engine, due to the oversize valves and ports, I thought I should detail what we did to make sure there is no misunderstanding of the test results. It might be possible that a stock engine might not see quite so much improvement, as my engine has the below modifications to the cylinder head. I have not documented the manifold change on a stock four-liter head engine. Note, this modification to the head yielded a 10% improvement in gas mileage. The larger ports and valves alone, really did not seem to improve performance much, but I will take the gas mileage improvement all day!!
Valve sizes of the 4-Liter head are much larger than the older 258, but one can never be happy with that. The current intake valves are 1.90” and exhaust at 1.5 “and use an 8mm stem.
1. Even the new 4-Liter heads are somewhat restrictive due to relatively small port sizes and the worst is the exhaust valve ports. I took an intake and exhaust valve gasket and basically made the port sizes match the gasket holes. This is about a 7-hour project by hand. It is important to not over do this, as the ports can break through into the water passages. I only opened the ports to match the gaskets and manifold ports and had no trouble.
2. The head will accept 1.60” exhaust and 2.02” intake valves. This is best left to a machine shop. In addition to the need for new seats, and possibly guides, if the originals are excessively worn, the bowels directly beneath the new valves must be opened up for optimal airflow. Due to the 8mm stems, only the Magnum 360 valves, which are pricey will fit, but Long’s Machine shop discovered that the Chevrolet LS-1 valves, with a .002” larger SAE stem will work fine. You have worn guides anyway and this takes up the clearance with minimal modifications.
3. Actual measured CFM increase on a flow bench for 1991 or later head verses modified head. Stock at .500” lift intake 215 c.f.m. Exhaust at .600” lift 143.03 CFM. These measurements were done at Long’s Machine Shop.
4. Modified head. Intake at .500” lift yielded, 252.63 c.f.m. Exhaust at .400” lift yielded, 152.14. (Note, no additional flow was gained at .600” lift) This is an increase of 17.4% increase on the intake and 6% on the exhaust. If you look at the flow curves on the exhaust, at .400” lift before and after, you see a 10% increase at the same lift.
5. Long’s Machine and Custom Engines in San Antonio, Texas carried out the
actual valve conversion and testing. Phone 210 922 0637. Talk to Jerry.
Standard HO head flow data
Ported and LS1 oversize valve head flow data
The original valves at 1.5” and 1.90”, work well for millions of Jeep 4-liters. Not good enough. Let’s put in 1.60” and 2.02”. New verses old heads shown above.
Let’s clean up the intake and exhaust ports……..ended up almost Ľ” larger on the exhaust top to bottom and 3/16” larger on the intake. The main point is to port match the intake and exhaust ports to the intake and exhaust manifolds and gaskets. Note, how the original exhaust ports on the right in the picture above, are much smaller than the gasket. The gasket is the same size as the exhaust manifold. Actually my brother and I did the porting work based upon a few articles in the net on head porting. We got the porting stones and kit from Summit Racing. This takes almost one hour per cylinder or almost 7 hours total to do the port and polish by hand, before the machine shop work was done on the valves. Note, Long’s Machine can also do this porting for you, but you will save a ton of money if you do the porting work yourself and let them do the valve conversion and flow test the result on their bench.
Conclusions: The HP&TQ gain I stated was a result of changing all three parts (intake manifold, 99+ 22.5lbs injectors, and the Hesco adjustable fuel pressure regulator to get the fuel rail up to the right pressure for the newer injectors) and that my modified motor helped with higher HP gain possible, more than probably (since there wasn't a test on a stock motor) a stock motor might see, sorry stock guys you have lots of catching up to do!
Last edited by DJJordache; 04-28-2006 at 04:05 PM.
yeah that was long huh?
oh and I will soon be doing this same mod on my brothers XJ 4.7 stroker! will be hoping for an even larger boost in HP and TQ!
I was under the impression this swap would only pull about 5-10 hp.. but 30 at the wheels? Incredible. I'm going to have to show Dino this one.
so a 4.slo HO pre 99 ony puts down 145 hp to the wheels?
what a power house
Wow, I wasn't expecting those numbers. Awesome!
All numbers you get from factory is at the crank. You think the 5.9 is putting down 245 HP at the wheels? Think again. That's why all of the new SRT-8's have the same HP ratings (425 I think it is).. if they did a chassis dyno every vehicle would have different drivetrain losses so every vehicle would have a different number.Originally Posted by LouisianaZJ
a 30% drivetrain loss is pretty highOriginally Posted by TrojanMan
Yeah, but we're talking about a jeep grand cherokee here.Originally Posted by LouisianaZJ
*edit* also, it's automatic so it has more parasitic drag.
Thanks for the props guys! This was an EXPENSIVE TEST! the 2 dyno runs were about $90 EACH!!!! for about 3-4 pulls with air/fuel curves.Originally Posted by TrojanMan
the drivetrain loss is pretty HUGE on the ZJ, but I also did the math on my brothers XJ and got about the same % loss........ So after we do this to his 4.7L I can estimate we will be OVER 300 flywheel HP!
That's what i'm hoping for
that'd be like 1 dollar per hp. I assume the FMS 24# injectors will fit in as well?
yes the early and later injectors are COMPLETLY interchangeable with the intake and fuel rail. You won't have to change anything to use the FMS injectors.Originally Posted by TrojanMan
But if you were to use the WJ injectors you would have to modify the electrical plugins and zip tie the connectors on, no big deal though.
am i too drunk, or did i miss wtf you did to fix the overheating on the zj? is that the factory clutch that was modified? if another fan/clutch, which?
yeah I modified a stock style HD fan clutch to trick it to think it was hotter that it actually was to get it to lock up more and move more air through the radiator, and I can "unmodify" the clutch really quick for the winterOriginally Posted by Michael
Before the swap dyno run video:
I don't have a real place to host it and the site that I webmaster would kill me if I used their bandwidth.
Click here to watch ZJ-before-intake-swap-dyno
you need to richen that up to around 13.5:1 dont you?
ptownTSI - stoichiometric combustion is 14.7:1.
Interesting read. I'd like to see what kind of gains one would get with motor closer to stock that had a CAI and cat-back (stock heads, stock fuel pressure regulator, stock size injectors). It may be a project that I take on this winter.
Stoiciometric ratio for gas combustion is 14.7 but peak power is made in a slightly rich condition (mid to high 13s).
Not always true - I think it will vary depending on engine. The stroker in my Formula made more power slightly lean (right around 15:1), but my tuner backed it off a little bit to be on the safe side (14.5:1). Seems that the higher the VE, the leaner it can be run.
I'm going to try and add some more validity to the test by doing 3 separate 3 run groups with the Gtech:
1) the way it is currently 99+ intake 22.5lb injectors @ 49psi
2) 99+ intake, 93 injectors 21lb at 39 psi (stock)
3) 99+ intake, 93 injectors 21lb at 43.5 psi (what my stock pressure regulator actually tested at)
but before all of this I have to find a local weigh station to get the correct weight to put into the Gtech, and on top of that, study for my finals on Tues and Thurs which are gonna suck!
Great bit of work DJJordache !!
Did you keep track of torque and hp reading from 1000 to 3000 rpm too? I'm really interested in what manifold does at this street and highway rpm range. Expecially the approximately 1700 to 2500 rpm range of cruising from approximately 55 to 80 mph and the super-lowend torque for right off of idle for crawling.
If you don't have these, no problem.
Thanks for sharing all this documentation with us!
sure no prob but the 1000-3000 range is not covered in the dyno runs b/c they dont want the vehicle shift around even though it is strapped down. They want it in top gear for the run. if you watched the vid I posted they ran it up through the gears and then got on it for the run.
sorry guys I wish I also knew the gains in these rpm runs but I only have the butt dyno for those rpms but it does feel like there might be more off the line...
but again, FYI not everyone will have the same gains I did, just depends on the engine setup to maximize the gains when all the parts are working together in Jeep engine harmony
DJJordache, Does your butt dyno feel any difference when going up long grades? Hopefully it holds speed on grade with less throttle needing to be added. That's what I hope for with the conversion on my rig.
Thanks agien for the great writeup!
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