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  #1  
Old November 3rd, 2007, 00:04
megabyte5689 megabyte5689 is offline
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90 XJ Performance

What do I need to put on my 90 XJ to add more horse power ? Can I put a cold air intake on it?, throttle body spacer?
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  #2  
Old November 3rd, 2007, 00:12
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Re: 90 XJ Performance

Quote:
Originally Posted by megabyte5689
What do I need to put on my 90 XJ to add more horse power ? Can I put a cold air intake on it?, throttle body spacer?
You are going to be a bit hampered by the fact that you've got a RENIX rig (1987-1990 w/4.0L,) but that's made up for by your being in Kansas (where you are not, as I recall, subject to the whims and dicta of the Air Police.)

Still, it's also worth bearing in mind that the performance aftermarket for the XJ is a bit limited - which makes my usual question all the more relevant. "What, precisely, are you trying to do?"

It's an honest question - how do you know you've gotten where you're trying to go if you don't know where that is?

One of the best mods for your engine - bar none - would be to put in a crank and rods from a 258 (commonly called a 'stroker',) which may or may not be complemented by a performance camshaft as well.

An "Air Police-accepted" intake can be had from XJ-Armor (I think - I've got one, but I picked it up in swap a while ago...) and you can adapt most later cold air intakes to the RENIX as well. None of these kits includes a heat shield tho - so you're not really putting in a "cold air" intake until you box off the air filter from the rest of the engine bay (an open element will flow more than the ~3" x ~4" hole that the airbox breathes through, but you lose some due to breathing in warm - and therefore less dense - air.)

There are also some bolt-on engine mods, but these aren't really power adders on their own - although they do tend to complement each other well.

You'll see somewhat limited gains with low-buck bolt-ons, but if you start with a stroker, you'll be on to something... Search here for "strokers," or check out the strokers e-group - groups.yahoo.com/group/strokers - for more information.
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  #3  
Old November 3rd, 2007, 00:21
megabyte5689 megabyte5689 is offline
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Re: 90 XJ Performance

what do you mean by air police? Ya I've read about strokers.
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  #4  
Old November 3rd, 2007, 00:23
megabyte5689 megabyte5689 is offline
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Re: 90 XJ Performance

I probably won't go with a stroker, I just want better and faster acceleration like my 2001 XJ Sport.
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  #5  
Old November 3rd, 2007, 00:37
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Re: 90 XJ Performance

Quote:
Originally Posted by megabyte5689
what do you mean by air police? Ya I've read about strokers.
Air Police, Smog Nazis - whatever you want to call them. Local "Air Quality Management" people that like to stick a sniffer up your car's arse on a regular basis (here, it's every two years. Unless your vehicle is around 1975 or older, then don't bother. And, they're thinking about a 20-year "rolling limit" - between twenty years ago and "classics," they want to stick a sniffer up there every year. Bugger...)

Better and faster acceleration means low-end torque, which means moving more air at lower crankshaft speeds. Later heads "breathe" better than earlier heads (the #7120 - 1991-1995 - is typically regarded as best,) and a stroker increases airflow at all RPM ranges. Use a lightweight crankshaft (later 258) to increase throttle response.

Catch is - with a head swap, you'll have to swap intakes, throttle bodies, and the like as well. The later heads flow better because the intake ports were raised about 5/8" to lessen the angle that the air charge has to make. This means that the RENIX (1987-1990) intake won't "bolt right up" to the HO (1991-2007) heads - it can be adapted, but it's a fair bit of work to get it all to line up right and bloody stay put!

You can also think about a camshaft swap - but several of the AMC inline six performance cams are listed as "not compatible with computer-controlled vehicles." I've yet to determine if this means that the computer just flat won't work, or if it will be hard-pressed to adapt to the different valve timing events, or if it just means that it won't pass smog (and is therefore not a problem in most of the country.) I've been working on research for Swappology of late, and haven't gotten that bit of research done yet (it's a planned update for the Power Manual - probably get to work on it right after I finish getting information for Chapter Seventeen - Fuels together. Information on both books is on my site, and the link is in my sig.)

I've also heard that you can get rather "crisper" part-throttle response with a bored-out throttle body, but I've no personal experience to back this up. Yet.
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  #6  
Old November 3rd, 2007, 00:44
megabyte5689 megabyte5689 is offline
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Re: 90 XJ Performance

I'm looking at getting acceleration like my 01 XJ, without tearing down the motor completely
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  #7  
Old November 3rd, 2007, 00:53
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Re: 90 XJ Performance

Quote:
Originally Posted by megabyte5689
I'm looking at getting acceleration like my 01 XJ, without tearing down the motor completely
Good luck. You're somewhat crippled by the cylinder head. Here's a few little things you can do...

Install a cold-air intake (walled off from the engine bay) or a snorkel kit.
Remove the venturi insert from the spout on the airbox (take that hose off, you'll see what I mean.)
Look for an overbored throttle body (dubious utility, but it might help.)
Replace your catalytic converter and muffler with units rated for larger engines (I usually use a "universal" cat for BB Chevvy, and a muffler for SB or BB Chevvy. No point in putting more air into your engine if you can't get it back out.)
If you're lifted, consider replacing your downpipe. That crimp is there to give a little extra clearance for the front driveshaft at stock height - and you don't need it past about two inches of lift or so (I think...)
"Anything that isn't making you go faster is slowing you down." Put your rig on a weight-loss programme, and jettison anything that isn't engine that you don't need. Losing even fifty to one hundred pounds makes a difference...

But a stroker is still going to be your best bet.
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  #8  
Old November 3rd, 2007, 01:00
megabyte5689 megabyte5689 is offline
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Re: 90 XJ Performance

what makes my '01 so different from my 90
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  #9  
Old November 3rd, 2007, 01:53
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Re: 90 XJ Performance

High Output, and about 17 more horsepower at crank, that's the basic differenct between your 01, and 90. Just my .02. I happen to like my RENIX system. Possible different trans gearing, not sure on that though.
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  #10  
Old November 3rd, 2007, 06:01
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Re: 90 XJ Performance

Quote:
Originally Posted by megabyte5689
what makes my '01 so different from my 90
About 11 years of technology.
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  #11  
Old November 3rd, 2007, 06:11
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Re: 90 XJ Performance

If you want snappy accerleration, re-gear it. Go as low as you can stand it on the highway.

Also make sure everything is in perfect running condition, engine, tranny, t-case and diffs. Any thing can suck performance away from the engine.
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  #12  
Old November 3rd, 2007, 08:08
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87manche 87manche is offline
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Re: 90 XJ Performance

Quote:
Originally Posted by megabyte5689
what makes my '01 so different from my 90
completely different cylinder heads and engine management electronics.
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  #13  
Old November 4th, 2007, 12:32
CrawlingCritter CrawlingCritter is offline
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Re: 90 XJ Performance

I have a 90 XJ and I've noticed that the exhaust manifold is EXTREMELY restrictive. My wife's WJ (an 02) has a much better exhaust setup. Has anyone had any experience changing over to a header? Will the Grand Cherokee exhaust manifold fit an XJ?
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