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98+ Intake Manifold

XJ91

NAXJA Forum User
Location
G'Nagiwanka
Has anyone replaced the OEM manifold on an early 91+ with an improved 98+?
EDIT: My Bad 99+


I was wondering are the clamed HP increases noticable?
 
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Go Jeep or Dr. Dyno (i can't remember which) has done it and did a write up on their site.
 
Dirk Pitt said:
Go Jeep or Dr. Dyno (i can't remember which) has done it and did a write up on their site.


Go Jeep. Good info, but remember, he's in Australia. His XJ is slightly different spec.
 
I did it on my 96. The 99+ manifold is a direct replacement on the 96-98 4.0l. The problem with the swap on 91 to 95 is that you need to change the power steering pump, mounting bracket, and belt to the 96+ style. The only other thing needed is to extend a vacuum line and the IAT sensor wire.

Bryan
 
Yes it was me that has a write up.
Mine is a 95 which is the same as your 96's so you do have a bit more to change than me and will need a bit of custom bracket work I believe. A few others have done it though to a 91 so it can be done!

http://go.jeep-xj.info
 
Gojeep said:
Yes it was me that has a write up.
Mine is a 95 which is the same as your 96's so you do have a bit more to change than me and will need a bit of custom bracket work I believe. A few others have done it though to a 91 so it can be done!

http://go.jeep-xj.info

Go-Jeep. I have looked at you write up a few times and I noticed the PS pump bracket is much different than the US versions. Do the Aussie Xjs use 2 2 mechanical fans. The US version uses an electric on the driver side and a mechanical fan on the pass side. The US version splits into 2 PS pump mounts, the 91 to 95 use a different PS pump mount ans belt tensioner than the 96 to 01. Your Aussie uses a PS pump mount with the mechanical fan hub attached to it, the US version has the hub on the alt/AC mounting bracket. Just noticed a difference and was wondering how it was set up over there. Thanks. BTW, you have a great website.


As far as the 87 to 90 4.0ls, the ports are different, and the newer manifold has no provision for EGR hook up. Not saying it can't be done, but it would take some work to perform the swap.


Bryan
 
im in the middle of the swap right now. im putting one on a 93 xj. all u need is the manifold and power steering bracket. you old pump will work fine, i am planning on drilling out the holes in the intake to bolt the pump to it. also, you will need a 2001 belt. it is longer due to one more pulley. the 2001 power steering bracket has a seperate pulley on it for tightening.

-chris
 
I just scored a 2000 manifold for $68 shipped and plan on doing this soon, think I'm gonna try and find some new injectors first though.

For those of you that have done it, did it require removal of the exhaust manifold or not? My FSM says the gasket is a integrated unit and requires removal of both manifolds to replace. Yet on GoJeep's writeup, it does not appear that he had to remove the exhaust manifold. Or can you just keep the old gasket on and rub some silcon around the edges? Someone set me straight. Thanks

Scott
 
I would suggest getting a new intake gasket when doing the swap. Removing the exhaust manifold once the intake is off is very easy. The gasket is cheap, so I would suggest just taking the few extra minutes and swapping it out. If you still don't want to pull the exhaust off, I am sure some silicone would do the trick.


Well, to answer my own question about the difference with Go-Jeeps RHD and the US LHD. Check out this picture.....
psbracket.gif


I seems there is a difference on the RHD and LHD PS mount brackets.

Just for kicks, here are the part numbers for the updated tensioner bracket.

Part Number Part Description
6502 425 SCREW AND WASHER, Hex Head, M8x1.25x95
3300 2201 BUSHING, Idler Pulley
181 112 SCREW AND WASHER, .375-16x1.00
3420 2029 BOLT, Hex Flange Head, M10x1.50x50
4637 491 BOLT
53010 228AB PULLEY, Idler
6503 230 SPACER, Belt Tensioner
5301 0148 BRACKET, Tensioner
5301 0149 COLLAR, Tensioner Adjustment


Hope at least this can help someone.

Bryan
 
Re: 99+ Intake Manifold

Since a lot of people are jumping on the bandwagon and replacing their intake manifolds with the '99 and later version, I wonder if anyone has actually dynoed their Jeep before and after the swap to see how much HP/TQ gain there is, if any?
This seems to have been prompted by one or two wild claims about 15-20hp increases with the swap and I think those are a load of BS. If that were true, the '99 and up 4.0's would have had a much higher HP/TQ rating (i.e. 205hp instead of 190hp) than their elder brethren. That is obviously not the case. The '99 and later 4.0's are handicapped by heads with smaller exhaust ports but DC already compensated for that by increasing the exhaust valve opening duration with the reprofiled camshaft. They also redesigned the exhaust manifold and fitted a better pipe from manifold to cat.
The newer intake manifold has the same runner C/S area and more or less the same runner length as the older manifold. The only major difference is that the newer manifold has a much larger plenum. The result of that is more torque at lower rpm at the expense of torque at higher rpm, but throttle response will be slower and the vacuum signal will be weaker.
Unless a dyno test shows a significant HP/TQ gain from swapping in a newer manifold, I'm not convinced that the hassle involved in doing the swap is worth it.
 
Re: 99+ Intake Manifold

Dr. Dyno said:
Since a lot of people are jumping on the bandwagon and replacing their intake manifolds with the '99 and later version, I wonder if anyone has actually dynoed their Jeep before and after the swap to see how much HP/TQ gain there is, if any?
This seems to have been prompted by one or two wild claims about 15-20hp increases with the swap and I think those are a load of BS. If that were true, the '99 and up 4.0's would have had a much higher HP/TQ rating (i.e. 205hp instead of 190hp) than their elder brethren. That is obviously not the case. The '99 and later 4.0's are handicapped by heads with smaller exhaust ports but DC already compensated for that by increasing the exhaust valve opening duration with the reprofiled camshaft. They also redesigned the exhaust manifold and fitted a better pipe from manifold to cat.
The newer intake manifold has the same runner C/S area and more or less the same runner length as the older manifold. The only major difference is that the newer manifold has a much larger plenum. The result of that is more torque at lower rpm at the expense of torque at higher rpm, but throttle response will be slower and the vacuum signal will be weaker.
Unless a dyno test shows a significant HP/TQ gain from swapping in a newer manifold, I'm not convinced that the hassle involved in doing the swap is worth it.

From what i was told 2000 and up have the low port head.
 
You also have to consider that the 99+ XJs have a lot more emmisions stuff on them. If I'm not mistaken, they are the LEV vehicles. I know a guy who did this upgrade on a 95 and it did make a big difference in power, but it was running too lean at first so he had to put the newer style fuel injectors on it and then it ran great but his fuel economy went down around 25%. It was his DD so he went back to the stock manifold. :pirate1:
 
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Ravi, while the 4.0 in the WJ is rated at 195hp/230lbft, the same engine in the XJ was still rated at 190hp/225lbft until 2000 when it was uprated to 193hp/231lbft. The TJ engine was also still rated at 181hp/222lbft until it was also uprated to 190hp/235lbft in 2001.
A new slitter vane water pump contributed 2hp towards the increase. The rest was mostly due to a better twin outlet exhaust manifold and downpipe to the main cat.
The newer intake manifold probably enhances low/medium rev torque by virtue of the larger plenum but I don't think the difference is that much. Even Marcus (GoJeep) only reported a slight change.
 
Dr. Dyno said:
Ravi, while the 4.0 in the WJ is rated at 195hp/230lbft, the same engine in the XJ was still rated at 190hp/225lbft until 2000 when it was uprated to 193hp/231lbft. The TJ engine was also still rated at 181hp/222lbft until it was also uprated to 190hp/235lbft in 2001.
A new slitter vane water pump contributed 2hp towards the increase. The rest was mostly due to a better twin outlet exhaust manifold and downpipe to the main cat.
The newer intake manifold probably enhances low/medium rev torque by virtue of the larger plenum but I don't think the difference is that much. Even Marcus (GoJeep) only reported a slight change.
Thanks for both of your replies, and in particular the dimensions of your head porting, thats exactly what i will do, i am a very good copycat. :yelclap:

Ravi
 
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