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Thread: Aftermarket headers worth it?

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    Default Aftermarket headers worth it?

    I have a 2002 6cyl 5 spd manual TJ which is stock. I'm interested in dropping some dollars on it to improve performance somewhat and maybe increase mpg somewhat.
    It has been recommended to me that I go the Borla header and cat back route. I'm wondering, however, if these mods will really accomplish much of anything on a 2002 TJ. I suspect that the stock exhaust is fine and the aftermarket stuff is really unnecessary.
    I'm therefore interested in opinons as to whether money spent for headers and cat back will be money well spent on a 2002 TJ -- or just wasted. By the way, I don't care at all about increased "cool noises" out of the Borla deal as I think the TJ is loud enough overall as is! It's performance and mpg that I'm interested in. Thanks!
    2006 Liberty Limited, mopar skid plates (all), tow hooks, factory P235/65R/17 tires, no mods (yet)

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    Forum Leader LeadFoot's Avatar
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    Doing exhaust upgrades is useless without drawing more air through the intake.
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    i got a bit of power I'd say off my borla but no where near what the cost is. Only upgrade your exhast if you need too I'd say.

    You could try a cone air filter, header, better exhast and it might give you more power but really the best way is to regear
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  4. #4

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    Originally posted by LeadFoot
    Doing exhaust upgrades is useless without drawing more air through the intake.
    I noticed a increase in power from doing a cat back exaust on my 2.5L TJ. I also added a k&n air filter at the same time, whick alot of people say is useless as well.

    I wouldnt go for the borla get a Race Magnum, I think made by walker now, or a dyno max with a 2.5" pipe. I ran the same set-up on my YJ, but I never noticed any increase in MPG, but maybe cause I really liked the new found power as well though

  5. #5

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    I did the Mopar performance header and a full cat back. MAYBE 5 hp, barely noticeable. I also added the K&N, the AirRaid, the Helix, sounds pretty cool, but no where near worth the $$ spent. It's all in gears and LOW range IMO. I am planning to stroke it to a 4.7, let ya know on that one if it's "worth" it.

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    There is really nothing that you can do, bolt on, to the engine to really increase power. Maybe for a few days, but the OBDII will adjust itself and basically undo whatever you've done.
    You may hear all sorts of people say, "well, it feels like more power", etc., but dyno it and see.
    Several magazines have done that in the last year, and basically zippo improvement for things like high air flow air filters, cat back exhaust, headers, etc.
    Remember that the computers are there to provide that most power possible *AND* keep 'em emission complaint. The computers will simply adjust most bolt on "improvements" out over a weeks time.



    Fred
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    i have the six w/5speed also, did a borla header and catback. i like the extra power, and tossed the tip, needed the clearance. i had a cracked header so i needed something there and the warrenty was done. the best choice (IMHO) is to upgrade the exhaust when it is needed. go for some of the other nice upgrade, such as a replacement for those pieces of tin that the fellows from DC call bumpers. good luck on your choice.

    R.C.
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    '97 TJ 4.0 sahara
    terflex 4", 33" boggers,
    borla headers and cat back w/hi-flow cat
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    Default Re: Aftermarket headers worth it?

    Originally posted by nrifenbark
    I have a 2002 6cyl 5 spd manual TJ which is stock. I'm interested in dropping some dollars on it to improve performance somewhat and maybe increase mpg somewhat.
    It has been recommended to me that I go the Borla header and cat back route. I'm wondering, however, if these mods will really accomplish much of anything on a 2002 TJ. I suspect that the stock exhaust is fine and the aftermarket stuff is really unnecessary.
    I'm therefore interested in opinons as to whether money spent for headers and cat back will be money well spent on a 2002 TJ -- or just wasted. By the way, I don't care at all about increased "cool noises" out of the Borla deal as I think the TJ is loud enough overall as is! It's performance and mpg that I'm interested in. Thanks!
    well to be honest, I'm not positive, but I dont think they're going to improve your hp figures a whole lot. I'm not even aware of any out to replace the 01 and newer exhaust manifolds. They were revised in 01 which increased the flow over the older versions.

    may I suggest the "Speed Freaks" forum (i hate that name. sounds ricey *shrugs) here at JU for further assistance? http://www.jeepsunlimited.com/forums...?s=&forumid=17

    theres a sticky thread at the top named "Horsepower gains Revisisted" that might give you a start.

    I plan on modifying my 4.0 at some point in the future, but it wont be until next summer at the earliest.

    Other things I'm not too big on are so called "cold air" intakes as they are tested in a garage (shade) with the hood open for their HP increases. Well the tune changes in the sun with the hood closed and it starts sucking in "warm air" Instead, I am planing a custom "cold air" intake routed to the firewall. you can find Threads here and there covering that subject.

    here's a list of mods I plan on further investigating:

    "true" custom insulated and routed cold air intake
    bored out TB
    IAT relocation
    Hesco water pump w/high flow thermostat (no temp change though)
    electric fan to replace the conventional one
    crower cam #256hdp
    custom cat back exhaust with large high flow muffler (not to big on noise)

    after I get it assembled I'll play with spark plugs and see if I need a remapped computer chip or such to make it run properly or if I feel there's room for further gain.

    There are other things such as big port/valve heads and roller rockers available, but I can't say I'm going there for a while. Can't say much about ignition upgrades either as I think our newer 4.0's with distributorless ignition might be pretty strong as is.

    I'm also hoping I can get the whole thing to work properly with a different cam. (irt computer) i'll do some before and after sniffer tests to give me an idea how its working. swapping cams to some might sound radical, but I've done it in various other vehicles before and isn't that much of a hassle to me. (bolt on the Hesco water pump and electric fan while I'm at it anyway.)

    As you can see by my list, there arent a whole lot of things I consider worthy of attempting with my 4.0 and am going with some basics. I'd like to see 225hp, but *shrugs I'll take what I can get. If I can get 225hp, I'd be very happy and a content Jeeper.
    "Character, in the long run, is the decisive factor in the life of an individual and of nations alike."
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    Originally posted by DEN
    check out this post, and the ones I referenced in it:

    http://www.jeepsunlimited.com/forums...hreadid=304578


    wow... :loopyeye:
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    StealthTJ and Koolbreeze, you have contradictory advice. Which one of you should the originator of this post (and others reading it ) believe? Should we believe that all of Koolbreeze's modifications really do add up to make a difference, or that StealthTJ is right, and the computer undoes them all?


    ????

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    Originally posted by DEN
    StealthTJ and Koolbreeze, you have contradictory advice. Which one of you should the originator of this post (and others reading it ) believe? Should we believe that all of Koolbreeze's modifications really do add up to make a difference, or that StealthTJ is right, and the computer undoes them all?


    ????
    well, a cam is mechanical. it's "going to" flow more. The computer supposedly matches the ignition and fuel injector pulses accordingly. (using a variety of sensors from mass air flow on the intake side to o2 sensors on the exhaust side) how will it work? i'll find out. Will it be a waist? I'll find that out too.

    yes I will do more research first, but I have successfully changed cams on other vehicles with good results. (OBDII also) no Jeep 4.0s though so this will be new territory. I'm not the first person to do this though and it seems others have succesfully done this.

    how about stroker engines being run by OBDII computers? Those have more radical profiles than what I'm looking at.

    heres some various cam specs courtesy of Dino: http://www.angelfire.com/my/fan/Jeep4.0Camshafts.htm

    strokers usually run Crane 753901s

    here's some basic "un Jeep" info on cams and other modifications to OBDII equiped engines: http://www.se-r.net/about/200sx/scc/july97/july.html (my other car is a first gen se-r)

    Quote from that article:

    Camshafts
    Perhaps the most difficult part of Project 200SX SE-R‘s build-up was the design of the camshafts. Aftermarket cams and OBD-II don't get along for a variety of reasons. High overlap cams can cause pulsation in the intake manifold at low rpm. The pulsation in turn cause wildly erratic airflow meter and MAP sensor readings that make it impossible for the ECU to properly deliver fuel. Not surprisingly, such erratic behavior will be noticed by the OBD-II system, which will assume a system malfunction and start logging error codes. A lumpy idle caused by a big cam can also make the computer think a misfire condition is occurring. OBD-II systems are required to look for misfires and log their frequency. The only way they can currently do that is by closely monitoring crankshaft speed. Erratic changes in rpm (i.e., rough idle) will be interpreted as frequent misfires, and again, error codes will be triggered. Cams tuned to work well at high rpm often sacrifice low-rpm pumping efficiency. This, in turn, causes low manifold vacuum that can interfere with EGR operation. Very high overlap cams will exhibit an "eight stroking" phenomena at idle where each cylinder will completely misfire on every other compression stroke. Thus there is only one power stroke for every eight strokes instead of over four when everything is operating properly. This phenonmenon is responsible for the loping idle of the older hot-rod V-8s. Unfortunately, with every other exhaust stroke pumping out a cylinder full of unburned gas, hydrocarbon emissions soar. The over-rich exhaust will not contain enough oxygen for the catalytic converter to complete its breakdown of unburned hydrocarbons, so even with the cat in place it will become ineffective. Clearly, our cam's profile had to be slightly compromised in order to get a smoother, more stable idle with steady airflow meter voltage and consistent manifold vacuum.

    I will run sniffer tests before and after to compare. I don't feel like running a gross polluter or overly rich/lean situation. I would swap them back if that ends up the case and I have no other means of resolution. Such as swapping out injectors with different flow rates....
    "Character, in the long run, is the decisive factor in the life of an individual and of nations alike."
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    Virtually every question asked here produces contradictions in the answers. Read, read, and read where dyno test have been done.
    Cams can help a little, particularly maybe with HP, but most of us want torque not particularly HP. Stroking can help, but at a pretty huge cost, both up front dollar wise, then engine wise, having to run premimum fuel, hot engine, etc.
    I'm happy with my Jeep (power wise) as it is. If I wanted a sports car, that's what I would have bought.
    Mine will cruise all day long, on the freeway, at 65 ~ 70 mph, no problem, up hills, on flats, down hills. Around town, it's fine, but I'm not an aggressive , I'm past 16 years of age a long time ago
    Want more power, drop a V-6 or V-8 in it.
    You won't really pick up anything by headers, fancy air systems, cat backs, etc. The computer will ajust 'em out.
    Go back looking through some of the 4by mags for the last couple years. Several of them have done just those mods and dyno tested before, during, after, and have found, basically no difference after.
    It's your money, do as you wish. Myself, I have other mods to spend my on (making it more trail worthy), than chasing a few extra ponies, that really don't mean much



    Fred
    Fred Wilson
    Base - '98 Sahara, 4.0L 6 cyl, Auto (swap from 5 sp)
    Suspension - 4.0" Procomp Springs + 1 1/4" JKS body lift.
    Rear tri-link. Currie J arms in the rear.
    HPD30, front axle, With Currie J-Arms, WJ knuckles, WJ dual piston calibers, Warn Hub Kit, with Warn inners, and CTM u-joints. Cross over, hi-steer.
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    Axles & Lockers - Dana30/Dana44 (rear disk conversion); LockRite/Full Detroit; 4.56.
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    Recovery - Warn XD9000i


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    There really isn't any single item to do to make these engines perform better. The factories have done a very good job of engineering everything to match. If you upgrade one item, you probably won't gain much. You need to upgrade everything to take full advantage. And to upgrade everything is a little expensive. And you may or may not be totally happy with the results. If you put in a bigger cam, you will probably lose low end horsepower and torque. Bigger in this case is not always better. Unless you plan on doing 1/4 mile drag racing!

  16. #16

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    I don't understand the "be-all, end-all factory performance" mindset. These engines can make more power and OBDII does NOT adjust to negate the effects. If the computer senses more incoming air it will still flow more fuel - which makes more power.

    I think you guys feel that these mods should net you 25% or 30% increases in power - that's not the case. Yes, these engines are well-designed compared to the old, de-tuned engines that came on the scene in the early emissions days, but power can still be had. I think the destinction that needs to be made is whether 10 or 12 h.p. from an intake, header, and exhaust is worth the money - 10 or 12 h.p. is still a noticeable difference!

    Besides, the gentleman who made the comment that you may feel the difference for a few days before the computer adjusts to negate it has it completely backwards. These computers take time to learn what's been done and then they make MORE power. With the Avenger SC, we went from a noticeable increase and 10 - 11 mpg after it was installed to a LOT more power and 14 mpg now. If the computer negated the effects of power-adders then the SC would be a waste of money!

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    If I can go from 10 to 14 MPG on a single mod, I WANT ONE!!!! WHOOHOOO!!!bsess:

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    [QUOTE]Originally posted by DEN
    check out this post, and the ones I referenced in it:

    http://www.jeepsunlimited.com/forums...hreadid=304578
    [/Q
    01' TJ 4.0L, Stone White, 3 Spd. Auto, Tera 3T, 1" Daystar BL, MORE mm, DT Shocks, JKS Discos, Currie Front Track Bar, Rancho RS 5000 SS, 4:11 gearing, 33 x 12.50 Trxus, Spidertrax Wheel Spacers for the Canyons.

  19. #19
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    the thing is there are a lot of gimicks out claiming increases in power while they dont have much use on an otherwise reasonably well designed engine. I'm not a fan of these and would prefer to think out what I'm going to do in advance.

    There is room for improvement and I intend on pursuiing those avenues. One thing a computer couldn't hope to "counter" is an electric fan and smoother water pumpimpellor. How much hp is that going to get you? I wouldn't count on much over 5-6 ponies combined. Is it worth it? Depends on the individual. I was actually impressed to see there are gains when boring out throttle bodies. The throttle body for the 4.0 is rather large as it is a dry flow and when you use a cfm calculator, flows plenty for the size of the engine. But... people do this and are gaining a few ponies in there also. It's not like these mods when properly performed are going to wreak havoc with reliability. No the TJ isn't a sports car... lol. but if I wasn't interested in having power, I would've got the 4cyl. As far as the exhaust goes, I desire a queit powerful sound and amgoing to replace the muffler anyway. To have the guy at the shop bend me sometubing to match only makes sense. The cam? Well it depends on the profile. That cam isnt going to diminsih my low end torque. You would need to look at the specs and understand what they represent to understand that. It's a relatively low end cam and and the additional lift with that lobeseperation etc should increase my low end also. The thing is I don't want a major poluter on my hands, so I will have to play with a sniffer and figure it all out.

    Like anything else... what some do as a hobby and what have you doesnt always make sense for everyone. To be negative about these things is kinda silly if you're not into them yourself. If on the other hand you actually are an enthusiast who enjoys tweaking his engines and have usefull imput, I'm sure your recommendations and insight are appreciated.
    "Character, in the long run, is the decisive factor in the life of an individual and of nations alike."
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    So, like I said earlier, do we believe that all or any of these modifications make a difference, or does the computer just override them? As an unknowing, casual observer who is interested in this topic, and not knowing either one of you, I have no way of knowing which to believe.

    ???

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