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Newbie horsepower questions. What to expect

540ismiley

NAXJA Forum User
Location
denver
I was looking for headers, exhuast, performance chip, and a throttle body for now. May go with a supercharger later. What have you guys found to be worth the money? And what are the horsepower/torque and fuel effeciency gains.
thanks
josh
 
Okay, not the end all be alll expert, but these are easily answered questions.
Header: Not much, maybe 5 ponies because of the efficiency of the stock design.
Exhaust: Hi-flow cat, 0-2 hp, Cat back, 5-12, depending on system
Performance chip: Gonna get some reponses for this one, but probably jackshoot in terms of hp, but most help by playing with the shift points, so maybe a little help with an automatic rig.
TB: 2- hp, Help the most when used in conjunction with everything else, dont waste the big bucks on a huge one, just a bored out one like jeepers 'n' creepers will do the trick.
As for efficiency, probably very little, and what you do get will be overshadowed by how much heavier your foot will get when u have a quick truck. Hope that helped, everyone else feel free to chime in or criticize.:anon:
 
540ismiley said:
I was looking for headers, exhuast, performance chip, and a throttle body for now. May go with a supercharger later. What have you guys found to be worth the money? And what are the horsepower/torque and fuel effeciency gains.
thanks
josh

You'll find the answers on my website. :)
 
I have done several mods just to increase horses (albeit low-end torque was my goal) using the intake/ outake / combustion theory and of the mods (Borla, catback) ignition showed the single largest gain of any of the mods I did. MSD 6 Off-road, MSD Blaster coil and 8mm wires. Easily noticed by the seat of the pants. Be forewarned the MSD box puts out a LOT of spark so BE CAREFUL. Also if you have stereo equipment that is valuable put a noise filter on your battery. I rigged a 80gig Hard drive in my jeep to play MP3's so I have skip free tunes while wheeling and the MSD box fried that puppy in no time.
 
Dr. Dyno, have you actually run your XJ on a dynomometer to verify the numbers on your website, or are these guesstimates based on the manufacturer's claims?

540ismiley, remember that the performance chips require you to run premium gas. So, more power, but lots more money also.
 
dmillion said:
Dr. Dyno, have you actually run your XJ on a dynomometer to verify the numbers on your website, or are these guesstimates based on the manufacturer's claims?

Unfortunately I don't have access to a dyno so my HP numbers are either based on my own "before and after" performance numbers or on actual dyno numbers that I've sourced from various articles.
I think it's fair to say that the ~50hp/40lbft gain that I've seen from my own package of mods is a pretty accurate estimate. I never believe manufacturers HP claims anyway because almost without exception they are BS.
 
Here are a couple good links. For those of you who think JET chips dont work, read the article links below. 4.0 was dynoed with an 8.2hp gain with the stage II chip.

http://www.4x44u.com/newproducts4u/projectpowerzj/

Here is another excerpt from our own JU testing:
"Last week week I removed a Jet Stage 2 chip from my 1998 Grand Cherokee Limited 5.2 before returning it to the dealer for a new WJ. I took 0 to 60 times with a G-Tech pro before and after. Note, my ZJ had Positive Performance Headers, Car Sound Cat, Gibson Catback, and a custom K & N cone filter. I averaged three 0 to 60 runs. Here are the results.

Before (with Jet Stage 2) - Average 0 to 60: 6.95 seconds
After (10 minutes after removing the chip) - Average 0 to 60: 7.10 seconds

There is also a MOPAR Performance computer upgrade available now this application. Jet was the only game in town for a while, now there are choices. The MOPAR computer seems to change more parameters, give a better dose of HP, but seems a little more sensitive to fuel and is a more involved upgrade."
 
XJ Saga said:
.....
Before (with Jet Stage 2) - Average 0 to 60: 6.95 seconds
After (10 minutes after removing the chip) - Average 0 to 60: 7.10 seconds

That's a ~2% change so if you had ~250hp without the JET Stage 2, you had 255hp with it. I went from ~211hp to 215hp with my JET PCM so it's the same 2% change.
 
Remember that the changes will be different for different year models. If I put headers on my 00' I wouldn't get nearly the increase (if any!) that someone with a 90' (or even a 98') might get. Same story with most other things...
 
drewlee77 said:
Remember that the changes will be different for different year models. If I put headers on my 00' I wouldn't get nearly the increase (if any!) that someone with a 90' (or even a 98') might get. Same story with most other things...

I tend to agree with that.
Also regarding the JET chip with the Gtech Pro results: you have to consider that the Jeep did'nt have much time to relearn/recalibrate the PCM in order to get those time differences but nonetheless the Gtech showed higher times. I'm sure that if some time had elapsed (couple of days to a week) then those times without the JET chip would have been even higher. Just like any other mod.
 
1000hp for 1000ft if you put enough NOS to it.
 
Is that 1,000 feet under power, or does that include coast distance??? :doh:
 
Ok As far as headers go the later moddle Xjs aren't going to see much change until you start with other mods. I'm a tried and trued hot roder I willl moddifiy anything tthat i can get my hands on.my first XJ need a motor so it cam out and was punched 30 over and got a clifford cam and valvetrain minus the rocker(that was a mistake since a hardend pushrod will go thought a stock rocker). I alos put a Pacesetter hhesaedr on it witch at the time seemed like a great deal but wasn't the greatest qualityl but I have headr4 they may have in proved thier work(this was in 97 when I did this.) that witha 2.5 in exaust and good plugs a wires realy made it screem but I didn't know enought about the injection set up at the time to realy make the most of the gains. My current built XJ has a borla header witha a good 2.5in cat and turbo muffle going out thorougha cheap advancedauto tail pipe since they just seem to get smashed on the rocks and has a a custom 3in air intake I made.. with4.56 and 35 ssrs I can run with a bone stock HO XJ up till about 75 when thingfgs get interesting.My next mototr will be for a short bed 2wd MJ sateup for the street. Using a renix block and fuel system with an HO head (hopefully a big vavle head from AP with a WJ Intake and aPunched out Tbm to atleast 62mm. and a cam as yet to be decided and a mopar or mike leach headerand good igntion and other bascie thing that I've been palying with much like DYno has. I can see amost 300hp with out a stroker and forced induction plus when its time to realy play NOS is jusy a botton away. I have a roadd test of a long bed 2wd mj that wieghs in at 3040lb with open diff and 3.07 geras and I belive it was a 5speed running low 16s with with athe "auto stick" aw4 I'm working on and some 3.55 gears and 4link or IRS I should see some very impressive #s and thats not inculding the wiegth reduction the truck will see.
 
1000ft till total meltdown!!
 
i think 1000ft would be how for the piston would be slung after meltdown.

sorry that i hijacked the thread.

i have a Jet stage 1 chip, firepower kit, K&N FIPK, and Flowmaster on my 98, but i added bigger tires and other stuff at the same time, it still is alittle faster than before, so most helped some but what is best i can't say.
 
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