96XJ performance mods advice??

[RudiXJ]

I'm new to the forums, is amazing how much info. are in this forums.

I have a few questions about my very clean and reliable 143,000 96xj 2dr. 4x4. She is my weekend warrior. Tow my flats boat, rescue vehicle, beaches, and to keep the miles off the Infinity. Well, It finally left me on the side of the road with a blown head gasket and clogged radiator. I decided is time to do some mods and put a little more muscle in her. I also had a RMS to R&R..I had a little $ laying around and purchased a CSF 3 core Rad., flowkooler W. pump, oil pump and some power upgrades. Clifford 264 EFI cam kit 206 @ .50 .474 lift, JP Double roller T. chain, and a Performance head from Clearwater Heads, big valves 2.02 in-1.60 ex. 0331 new casting. Clearwater built the head specifically for this cam. The head wasn't cheap. I found out that my old 0630 head was not cracked or warped, but at least I got to keep it.
Currently the XJ has a Magnaflow CAT back, K&N CAI and D.U.I Performance ignition kit.

My questions are:
1. Headers? hi-flow CAT? or keep the factory Ex. man. since is not cracked.
2. I picked up a 99 xj In. manifold from the salvage. ($10) Use it, or keep the old one??
3. 703 injectors? $100 from Precision Injectors, they are local. Purchase or keep the old injectors?
4. HP/TQ predictions?? Hopefully I will have a nice power gain.

BTW, the Cam Kit, RMS, JP Chain are installed at this time. Everything looked great ( cam. bearings, no sludge, rear main bearing) etc. after so many miles I was impressed. The only thing was the carbon buildup in the intake runners and top of pistons. Everything bolted up great so far.
Thanks

 

[SolarBell]

If what I've read is right you'll see 4-5HP from the 99+ intake. If you have it put it on.

If Talyn sees this he can chime in on the header, but it's probably worth it (high-flow cat too) just to match with the flow from the upgraded head.

Search and find the injector thread on here. There is lots of info on the injector swaps. It would be worth if for all the new engine parts to at least put in a cleaned and matched set of stock injectors if nothing else. I'd tell you the good answer but my knowledge on injectors is minimal, Talyn can recite them from memory.

I don't see it, but I would find a bored throttle body at least 60mm in size. I've seen them on eBay starting at $50.

 

[O-Gauge Steamer]

In my experience with fitting the late intake to the earlier engines, what I have found is that the engine runs better on the highway. The curved runners in the late manifold come into their own once the engine speed is up into and above the mid-range.

For the bottom of the engine speed range, little to no improvement is gained. But... This is what the Chrysler Engineers needed to do in order to improve the mileage of the XJ in particular and the 4 Litre in general.

As it has been a number of years since I drove a non-Supercharged XJ, I do not recall the mileage improvement. That it was there, I do remember. Just not by how much... Sorry about that.

Headers. Better than the stock manifold for sure but they are, to me at any rate, hard to justify owing to the cost of a quality unit. If it were me, I would run what is on there until it cracks and then replace it with an aftermarket part. When I first obtained this '98, the manifold was cracked so it was replaced with a header. Unfortunately for me, the header had to be replaced with a stock replacement type of manifold (the type with the bellows on the numbers 1 and 6 ports) as the header would not clear the Sprintex Supercharger intake manifold... Not a sacrifice at all as it turned out...

A short note on headers. There has been discussion, in the past, on wrapping the header. IMO, this is a fatal mistake as it creates hot spots in the metal at each end of the wrap. These hot spots promote metal fatigue and subsequent cracking at those locations. Most, if not all, header manufacturers will void their warranty if the header is wrapped. The better solution is to wither use a header blanket (I do...) or, install a ceramic coated header.

Before someone points out that Dragsters usually have their headers wrapped, it must be taken into consideration that those headers are not expected to run for tens of thousands of miles... The parts we use are so expected.

 

[Dr. Dyno]

My questions are:
1. Headers? hi-flow CAT? or keep the factory Ex. man. since is not cracked.
2. I picked up a 99 xj In. manifold from the salvage. ($10) Use it, or keep the old one??
3. 703 injectors? $100 from Precision Injectors, they are local. Purchase or keep the old injectors?
4. HP/TQ predictions?? Hopefully I will have a nice power gain.

1. Keep the stock header, have a 2.5" downpipe custom made at an exhaust shop, and add a 2.5" high-flow cat.

2. Use the '99+ intake manifold. I saw a small HP/TQ gain but the real bonus was gaining ~1mpg.

3. Your existing '96 injectors will do fine. Add a 62mm throttle body to improve response.

4. You'll definitely see a nice power gain.

 

[RudiXJ]

Thanks for all the advice...

 

[O-Gauge Steamer]

Could always drop a Supercharger into it...

That works.

 

[Talyn]

I'll just echo what Dyno said. With the exception of headers. Keep stock for now and replace when the stock manifold cracks or when you have extra money. Get a 62 or 63 mm throttle body now instead.

 

[Skwirl]

Intake, throttle body and exhaust covered = air

What can we do for fuel ? I searched some mixed review stuff about adjustable regulators and piggyback this n that. None of the info on fuel seems clear.

I also have an xj with around 150k (99) and would like to make some performance improvements. All the airflow stuff is covered. Injectors don't seem to help unless you control the timing......

 

[O-Gauge Steamer]

Leave your fuel alone.... There is absolutely no reason, good or bad, to make changes to this engine. Unless and until the displacement is changed by either building a Stroker or installing a Supercharger, the fueling of the engine is fine. Believe it or not, the Engineers at Jeep knew what they were doing...

That being said, there a numerous unsubstantiated claims about replacing the single hole stock injector with a four hole injector such as those used by Ford.

I say this is unsubstantiated as I have yet to see any sort of before and after Dynamometer
runs.

I am partial to installing Superchargers over building Strokers But, the engine must be in good nick prior to fitment of the compressor.

Changing the timing is one thing that can be slightly altered if the CPS (Crankshaft Position Sensor) is altered. It is impossible to add in an external controller (such as an AEM F/IC or a Split Second unit) and gain timing.

The way the PCM works assumes that the timing is fully advanced mechanically by the physical position of the CPS. From there, the PCM retards the ignition only. All PCMs work in this fashion as to expect any device to send a signal out before it comes in is a bit daft.

Which is why all of the aftermarket fuel/ignition controllers state that the ignition can only be retarded from stock. Physics you know.

I am running an AEM F/IC 8 in my '98. I also am running 40 pound fuel injectors. The only reason I installed the 40 pound injectors was to be able to run an E85 tune. This proved not to be easily done. If I were to do this again, I would use either 30 pound or 34 pound injectors with the Supercharger.

My advice is to acquire books on the subject of fuel injection and invest in quality ODBII software for your laptop computer. Good software will allow you to monitor exactly what is going on with respect to the ignition and the fuel. You can also monitor the O2 sensor which has value in certain specific conditions.

It would be extremely difficult to attempt to fully instruct here in this forum.

I can personally recommend this for the ODBII software as it is an updated version of what I run...
http://www.scantool.net/obdlink-sx.html


This is what I have...
http://www.scantool.net/scan-tools/pc-based/obdlink.html

 

[Talyn]

What can we do for fuel ? I searched some mixed review stuff about adjustable regulators and piggyback this n that. None of the info on fuel seems clear.

Why? Do you have a stroker? some form of forced induction? Do you have a wideband and see it running rich or lean at some point in open loop? If the answer is no leave it alone.

 

[O-Gauge Steamer]

Thanks Talyn for backing me up here. Until and unless a major change is made to the displacement, the stock fueling works just fine. Leave it alone.

And yes, I lump Superchargers and Strokers into the same bucket. In both cases the displacement of the engine is being enlarged. The Stroker is obvious, the engine was a 4 litre, and now it is a 4.5+ litre depending. A Supercharger forcibly stuffs more air and fuel into the engine which accomplishes the same goal. To move more air and fuel through the engine than what the designers had in mind.

As I stated, get some books. I have found that digging into how things work to be a ton of fun which is why I am now altering the programming of my PCM with the goal of eliminating the aftermarket F/IC. But you can take it to the bank that I am stepping very slowly with the PCM mods... This can go bad very quickly if I get too bold.

The opportunity to screw things up if you do not know what you are doing is very high when you start mucking about with the engine electronics. Just be sure you know what is going on before the changes are made.

Now a Supercharged Stroker would be fun indeed and I will be doing one in the near future. The compressor (brand new Eaton M90) has been purchased and the engine will be available shortly. Once it is all in and done, there will be a thread here on complete with pre and post Dynamometer runs and photographs.

 

[dirtlover69]

Could always drop a Supercharger into it...

That works.

This I would really agree on, but surely it will not be a cheap upgrade.

 

[RudiXJ]

Got everything done no leaks, good break-in of the new cam, new cooling system, everything smootth. Took my time. BUT???? but no low end, step on gas and rpms go down for a split second then it launches. Good midrange and Top-end but there is a hesitation or bog? The 264 cam is supposed to be stronger with low end torque. It idles Fine, motor sounds good, what can it be? The big throttle body? Cat? I did not install headers, manifold 99+, or injectors. But I don't think that will cause my issue.

 

[Boostwerks.com]

nearly every aftermarket cam is going to move the torque curve higher into the RPM band. If low end torque is what your looking for, the factory cam is your best bet.

Having said that, it also comes down to tuning. You can have all the bolt ons in the world and still end up with poor performance if the fuel and timing haven't been addressed.

 

[streetxj]

Getting a larger diameter pipe installed onto the stock 91-99' 4.0 header is IMO a waste of $$$. Just replace the pinched section of the down pipe with a matching smooth pipe. That's what I did to my 96' XJ 4.0. The stock down pipe is nicely mandrel bent from the factory and goes from 2 inches to 2.5 inches. Sounds puny, but the stock header outlet is 2 inches so it really isn't choking anything. It actually better for the stockish bolt-on 4.0 since it speeds up the exhaust gasses and actually causes more of a vacuum (scavenging). When I floor it, it produces lots of power, even in the 4000-5000 rpms territory especially after upgrading to 703 injectors, so I don't think the 2 inch section of pipe is doing anything wrong. For the 91-95 HO's, installing the 96-99' HO down pipe is considered an upgrade. Now, if your header cracks and you go with a header like APN that has a 2.25 inch outlet, then go with a larger diameter pipe to replace the 2 inch section.

I'm excluding the 4.0 wrangler-type downpipes in this conversation.

My mods are:

2.25 inch Dynomax tailpipe with 2.5 inch Aero turbine muffler
2.5 inch Thunderbolt High-Flow Cat
Exhaust downpipe pinch/dent removed
180* thermostat
Modified stock intake system (K&N panel filter, air silencer/venturi tube deleted, more holes cut out of the filter box below the filter facing the fender).
Leigh Performance 62mm throttle body
Bosch 703 injectors
2003 jeep 4.0 intake manifold with thermotec heat wrap.

 

[gradon]

streetxj's above advice is great for the 4.0. Additionally, you could add a cam w/ less overlap, roller-rockers, and a port-n-polish to the head to get a little more out of her.

 

[RudiXJ]

It appears that I have a timing problem. I pulled the timing cover off and it look like the tc was off by a tooth. At TDC (comp. Stroke) the dots were not align.

Pulled the tc and align the sprockets to the correct position. I also painted the marks white.

After installing everything and back in the 4.0, I couldn't get it to fire up. Got some intake back fire. It turns over but will not start. I verified the firing order with the sparkplug wires, and made sure everything kis plugged in. Still no fire. The distributor was also installed correctly. I am stuck!..
Could it be a sensor? I have no ENG light. Dizzy off by a tooth?

 

[Talyn]

JP timing set. Use a degree wheel. It might look like its correct but could be off a tooth.

 

[RudiXJ]

This is the first time I had problems installing a timing chain without a D wheel. It is a JP set, is this a COMMON ISSUE with this set??. Should I just get the original tc set from the dealer? This would be the third time the tc cover comes off.

 

[Talyn]

I had a problem with the JP set. but I really wouldn't call it a problem. Looked dot to dot, but I checked with a degree wheel and it was 13* off. Rotated the cam gear 1 tooth and it was good, but still looked dot to dot. I think it may be the smaller links doing that.