Oyaji

Look guys, I appreciate that the desire to make modifications that improve on the original design is part of the allure of owning a Jeep, but if there is no significant benefit to be had, is there any reason to do a given modification? You might as well save your money and spend it somewhere else where it will do more good. You can also look at it this way: the benefits of scavenging exhaust headers have been well recognized and documented with the mathematics to design them for many decades now. With all the pressure on vehicle manufacturers to increase fuel economy and power, don't you think if there was practical benefit to be gained that they would have included them in their products by now? ... That said, if there was sufficient interest for an off-road application that would generate at least 500 orders, I would consider looking at designing a skinny-tube true long-tube header for use with short dual exhaust with target retail price of $500, ordered direct. I don't expect sufficient interest, and fewer orders than 500 @ $500 would make such a project unprofitable and a waste of time and resources. :(

Mostly on-target, but you miss the mark here: "If your engine was not designed for high octane or if you are having a pinging problem, then you are throwing your money away using high octane gasoline." Absolutely correct about the engine not benefiting from high octane gasoline unless designed for it. That generally means high compression or forced induction, which is what it takes to get the benefit from high-octane. But pinging can happen from carbon build-up in the combustion chamber (on both head and piston) or from unusual running under heavy load, and an engine in this condition would indeed benefit. If pinging cannot be controlled (by ignition timing changes via manual setting or knock sensor, or by fuel/air ratio compensation, typically by oxygen sensor feedback), short of pulling off the head and decarbonizing or gearing down, use of high-octane gasoline may be the only practical cure. edit: maybe I misread you, and I merely restated in detail the very point you were making? :???:

I like this ad better than the XJ one from last week... even though it has more grammatical errors, I think it is even funnier! It deserves to be posted here in its entirety so that if the link goes down we still have a copy for posterity: I should start by saying that if you are looking for a “Pajama party Barbie Jeep” you my friend, should keep looking. If you are looking for a short description of to the beast before you, I can offer you two words “MEAT & POTATOES”. This is the All American chariot of the free world. You are not dealing with any ordinary, cookie cutter Jeep son. This thing was forged from a single block of all American Tungsten Steel. Real sturdy! From that day forward my life has never been the same. Winch yourself off that couch and see if you can handle this Jeep Wrangler Sahara. So if you are looking for a rice burning hatch back, a solar powered liberal mobile, or even a Hyundai crossover keep on looking my friend this thing is a piece of red white and blue Americana Machinery. This baby’s pulse is pumping 4.0 liters of uncensored raw fuel through her straight six nuclear power plant. And rest assured this is no metro feminine automatic. . .you command her to obey, with your calloused hand planted firmly on the shifter. And she will obey, the first time, every time. If you can’t handle your stick shifter, or reach the clutch pedal, you better not ferry skip over here wanting to test drive her. If you stall her out, you can count on getting hit in the face with a piece of re-bar and sent back where you came from. It has A/C but are you kidding me….Really! If you want to blow the sweat off your brow, you do it the old fashioned way: doors off, top down. “What if it rains?”. . .You whiney b*@$£! I told you to stop reading. . . Any man who drives this beast doesn’t give a damn about rain. Not even skin melting acid rain, Cause he’s already dripping wet in blood, sweat, dip spit, and fish guts. If you are looking for the kind of jeep that has to be pansy parked in the garage, so the “carpet doesn’t get wet and soggy” Then you should plant your Obama sticker on some Japanese piece of $#!&. Cause this thing has drain holes in the floor and rhino lined to let the blood drain out from the buffalo you just killed, with your bare hands. Because you are William Wallace from Braveheart and when you get home you can leave your “sissy sponge glove car wash kit” in the pink bucket it came in. Go ahead and spark up your 6000 psi heated pressure washer on the dually trailer in your man cave, cause you are Tim Gillespie and you can pressure wash your truck on the inside. She’s got rhino lined floors with a full roll cage in case that buffalo comes back to life while you’re doing 80 over some mountain pass or flooded river. If you’re thinking about Mexican chrome bumpers for her, think again. The bumper bashers come hand forged in a blacksmith shop in Franklin County over a wood burnin fire, out of 4 inch well casing, and railroad tracks and then I welded em to the damn chassis. That way if you get deployed you can piggy back this war wagon on a deuce and a half and chain her down tight from the four corners, so you don’t lose her when your convoy gets hit by a taliband roadside suicide bomber. And forget about putting one of those “It’s a Jeep Thing. . .You wouldn’t understand” stickers on this machine cause when you’re spotted in this American Classic there will be no questions, no further explanation required, people will understand and get out of your way… real quick. If you think you’re ready to park this panty hauler on your tract of land. If you buy this jeep you better go get your old lady ready for some damn changes around your lair, cause this $#!& will be happening. What will be Happening? Glad you asked…. 1. More chest hair. 2. You’re growing a beard. 3. Meat Only Diet. 4. T-Rex for a pet. 5. You’re taking a job at the lumber mill. 6. Your car carries five kegs. 7. Penis enlargement. 8. Catch more fish. 9. Wire bristled toothbrush. 10. Sex in the yard. 11. Sex in the garage. 12. All male offspring. 13. Chiseled jaw line. 14. Not giving a damn. 15. Flesh turning to steel. 16. Higher salary 17. Promotions. 18. Better looking wives. 19. Better looking mistresses. 20. More golfing 21. More killing stuff. 22. More dead animals in the KITCHEN freezer. 23. More tools in your garage. 24. Bigger TV 25. Wife takes out the trash 26. Four Wheel Drive 27. Wife brings trash can in from road. 28. Wife stops bitching about clothes on floor. 29. Wife stocks fridge with beer. 30. Chuck Norris. 31. John McCain 32. Steaks for dinner. 33. Winning the Lottery. 34. Women on the side. 35. Wrestling with bea 36. Building $#!& out of stone. 37. Riding Lawn Mower. 38. Bon Fires in cul-de-sac. 39. Bar Fights. 40. Wife picks you up from Thee Gentlemen’s Club. 41. Craftsman Tools. 42. Jay Bisset. 43. Welding stuff. 44. Digging holes. 45. Huge Piece of meat. Put your GPS back in your purse. Sounds good doesn’t it? This jeep has carried me through 155,000 miles of battlefield twice as gruesome as the second half of the movie “300″. . ..And just like a trusty steed this juggernaut has never left me stranded. If you think you’ve worn her out you drag this beast back to me in any condition. And Ill handle the rest. But if you think you’re going to get to whip this mule you better pony up Sixty Five Hundred Dollars. . .American Cash. I’m not selling you this car unless you are clearly a pure blooded American Species, so don’t even think about it. Read more: http://www.uproxx.com/webculture/2013/10/check-balls-texas-mans-craigslist-ad-jeep-wrangler/#ixzz2k10EBEUf Follow us: UPROXX on Facebook

I guess it depends on what you expect out of them, and what the value of money is to you. Without seeing good hard numbers from objective testing (manufacturer's numbers are automatically suspect as being merely ammunition for advertising - independent test results are far more trustworthy - no results are 'gospel' without methodology and test conditions plainly reported), I wouldn't buy any from any maker. As Hornbrod mentioned, the limited space available in the engine bay severely limits the potential of any headers I have seen for this application. The link he posted is a critique and comparison write-up on the subject (sadly, lacking hard data) by a (in my opinion) fairly well-informed Australian, and is worth reading: http://jeep-xj.info/HowtoExhuast.htm

With any luck, I hope to have my own booth out there at SEMA in a year or three. Damn, but ain't it expensive though! If I can swing that, maybe I'll be able to swing importing a trio of Japanese "companion girl" bimbettes, too. :D

My my, aren't we getting childish. More disparaging comments, now highlighted in BOLD! How sad. It's obvious you have never seen any dyno runouts comparing peak power and torque numbers of the various available headers on the same 4.6L stroker engine. And I'll be sure to suggest to Mopar Performance that they should rename their long-tube Mike Leach header based on an eyeball calculation from some unknown wannabe. They'll get a good laugh. Keep up the amusing prattle; it's very enjoyable. What is sad is that sales literature can get away with calling a product something it is in truth not: it is patently obvious from the photo that the primary tubes are nowhere near 31" or longer. They don't even look to be half that, nor are they equal-length tubes, for that matter, so it is a stretcher to even call them "headers". (It's also pretty sad that you feel the need to launch personal attacks, and that you feel free to do so with impunity under the mantle of the "moderator" title.) Unless those results to which you refer came from a steady-state load-controlled chassis dyno, they are of limited value. Since such start at around half a million dollars these days, I doubt very much that more than a few people have even seen one, nor that your vaunted tests utilized one. Still, you are correct that I have not seen the data from tests you mention. It is certainly true that objective data from a statistically relevant sample that does comparison tests is of greatest value. If you have that data, you should post it here, along with the test methodology and conditions. That does not change the fact that calling the headers in the illustration "long tube" is inaccurate (actually an outright lie). In combination with a properly-designed intake manifold, with the use of true long-tube headers it is possible to achieve volumetric efficiency of ~ 1.05 (105%) on some engines. This feat is only possible otherwise with some form of forced induction, which is why the phenomenon to which I referred is called "pressure wave supercharging". For reference, your stroker Jeep engine probably has only about 70% volumetric efficiency (maybe even less). With pressure-wave supercharging on a carburetted or mechanically-injected engine (pre-dating digital engine management, mind you), figures of 100 horsepower or more per liter were common... and this in the day when figures half of that were considered noteworthy. Accomplishing that on a 4.0 would net 400 horsepower! (Not ever gonna happen with the 4.0 head, but just consider that figure for a minute.)

Good to know - thanks... although since aluminum cuts like butter, it didn't take me but a few minutes to make one. Here is another trick: to block off the EGR source port, heat an old copper penny (1970s or earlier are copper, after that they are plated zinc and will easily melt) red-hot, then drop it into cold water to anneal (soften) it. Drop it into the port on the manifold, then screw in a flange nut salvaged from an EGR pipe and snug it down good. Works great. :)

Please enlighten us. Better yet, please don't. :yes: Stings a bit, doesn't it? ;)

Way more technical than you need for sure. MY point is that without an EGR there with a pintle on it to stop the flow of exhaust into the intake manifold is only half the equation. What's happening with the exhaust that's travelling into the intake manifold with the EGR absent? He said he "put the plate in to block the flow exhaust gas", so I guess that was an EGR port blocking plate. If I got him right, there should be no admission of exhaust gas into the intake manifold now, so your point (albeit a good one) should be a non-issue now. I just removed a bad EGR valve and replaced it with an EGR block-off plate I made from some quarter-inch aluminum scrap yesterday. Are these generally available, and if so, where? If so I could have saved myself the trouble by simply buying one!

Watch your economy over the next 2 tanks and look for confirmation of a trend, then... and find out what kind of oil you have in that thing and top it off! :D

Yeah, Carnuck is right to mention it. In 4-season climates, gasoline is reformulated for the different temperatures encountered through the year. In winter, a greater amount of higher distillates are added to reduce vapor pressure, which makes for easier cold starts. In summer, this is changed to reduce fuel boiling in hot fuel lines near the engine to reduce vapor lock starting problems. I don't know to what degree (if any) gasoline is changed around here for the changing seasons. We are still pretty warm here - still haven't had our first freeze, and our winters are very mild (no snow and very infrequent hard freezes - none for the past 3 years). I know in recent years gasoline formulation has gone to crap in general, so it would not surprise me to find that seasonal changes in gasoline composition result in significant changes to fuel economy.

Overall gearing is very important to highway fuel economy (probably more important than whether the engine is 4 or 6 cylinder). When reporting fuel economy you guys should mention any changes from stock tire sizes and final drive ratios.

Do any extra driving in town? Take a roadtrip with a significant headwind? Carry a load of anvils to auction? Most likely: you filled up at a different location than usual. If your car was not sitting level when you filled it, you could have gotten a big air bubble at one end of the tank that prevented a complete fill on your previous tank, then this fill-up had to make up for it with extra gas. Kudos to you for keeping track of your fuel usage and economy! It's a great indicator of how well your engine is running. I always keep track, and log any unusual running conditions that might affect economy so that when I am in your current position I am not left scratching my head. I suggest doing what I do: watching the average economy over the last 3 tanks, and if a trend is evident, seeking out and remedying the cause. PS - would you help me keep an eye out for a cheap Comanche or 2 in the area, especially 91s/92s? I'm just east of you 1 county...

. I think the kind of interest in me that you show is plain enough to everyone reading this forum.

No worries man - some people get a kick out of gaining a deeper understanding of how this stuff works, while some just want to make it work and forget about it. Take what you need, and come back later for reference if you want to - I think that is what the general readership does. :)

Trick? It's not a trick, and pinging is controllable depending on engine compression and fuel octane rating. It's called a piggy-back chip installed between the ECU and the engine harness and has been around for many years. The Unichip is an example. Once installed, it allows you to plug in a programing tool, like a simple Windows laptop, and download various programs called MAPs to match your engine configuration. These MAPs are used to control inputs to the ECU, be it OBD1 or OBD2. These inputs include the IAT, CPS, TPS, and MAP signals and allow you to tune the A/F ratio for max power, max economy, and points in between. Piggy-back chips like the Unichip can be used on both stock and stroker engines, although stock engines w/o sufficient suck and blow mods are limited. Carnuck - retarding the camshaft timing is primarily done to boost power at higher engine speeds. The converse is true as well: advancing camshaft timing boosts power at low RPM. You are correct in mentioning that doing this affects volumetric efficiency (cylinder charging, expressed in percentage of cylinder + combustion chamber volume), but any effect on ping is incidental. Hornbrod - anything done to change the state of tune by an engine tuner comes from his "bag of tricks", so don't get hung up on Carnuck's nomenclature. You forgot to mention fuel/air ratio, which is variable, controllable, and when too lean is the most common cause of ping/detonation. When you go on to mention "it's called a piggy-back chip", just what is the "it" you are referring to? Carnuck did not mention anything but a "trick". Are you saying that a "piggy-back chip" is a "trick" that changes volumetric efficiency? Because, if so, it makes no sense in your follow-up comments about various programs called "MAPs"... and unless you are referring to a computer-controlled variable valve timing engine, it makes no sense at all in any context. Regarding MAPs, I guess you are not talking about "Manifold Air Pressure sensors", which is the usual acronym as you spelled it out in capital letters (you even referred to "MAP signals" in your very next sentence of the same post, which if taken in the context it was presented would properly refer to Manifold Air Pressure signals - when you use the same acronym for 2 different things in the same post it is extremely confusing!). Here is an illustration of a typical fuel injection map: . Looking at it, you can see why it is called a map - it is in three dimensions and is similar to a topographical map of terrain. A map is not a program - it is a plot of tabulated data points. Superior to the rudimentary engine management of years past (before digital engine control), it takes into account additional information from the running condition of the engine and allows programming for varying load states, offering superior engine management compared to simple 2-dimensional curve plots of the past. This function is accomplished regardless of whether or not a "piggy-back chip" has been added. Such a chip is added only for modifications beyond stock, and even then only when the OE chip is not itself programmable. Better alternatives do exist that completely replace the stock ECU with a stand-alone system - but they are only for advanced users who understand and can make their own maps. As far as a blanket statement "In general use now is changing the fuel/air ratio via closed-loop control by utilizing O2 sensor feedback" ?? Would like an explanation how that is accomplished. Open/closed loop O2 sensor voltage output to the ECU is fixed in transition and is not variable except at 80% to WOT when the O2 sensor input defaults to open loop voltage, controlled by the ECU. There is no feedback. A Unichip or similar can control at what point this O2 sensor shift occurs based on the downloaded programmed MAP and the signals it delivers to the ECU. Yes - it is a blanket statement, and one that should not need explanation to anyone who takes even a minute to think about why a manufacturer would include an oxygen sensor. The amount of oxygen in the exhaust is an analog of how much fuel and air go into the engine (which defines the fuel/air ratio). The measured values of oxygen content in the exhaust are fed back into the engine management algorithm to adjust the amount of fuel being injected - which is the definition of "closed loop". Open loop systems did not utilize an oxygen sensor to monitor exhaust - having no such feedback is what defines "open loop".

Not really. That's what the knock sensor was for. It was to reduce emissions. Do you just pull $#!& out of your hat and post it up? Consider the folks that are relying on intelligent, well informed answers. You're doing them a real dis-service. The EGR's job is to take some oxygen away from the air/fuel mix so combustion temps are kept down and NOx formation is cut down. What happens to motors when you squirt nitrous oxide in? It burns faster and hotter. If you watch the tractor pull guys with gas motors, you can hear the pinging when they over NO2 the motors. Waaay too much and you see the backfires out the intake. http://autos.yahoo.com/maintain/repairqa/engine/ques080_1.html Knock sensor retards timing slightly to cut ping. What happens when timing is retarded too much? Power drops. Some internal engine noises mimic ping and cause the sensor to retard timing and really cut the power. I have 20 years as an ASE certified tech (since 1981). I left AMC when Chrysler took over and worked for Ford for awhile. I've been doing mostly parts since '02. . Carnuck is correct, but there are more ways to cut ping/knock/detonation than EGR and retarding ignition timing. Three more that come to mind are increasing the fuel/air ratio, using higher octane fuel, and reducing compression ratio. (You might think these sound impractical, but I assure you that all 3 have been used to eliminate ping in a running engine. In general use now is changing the fuel/air ratio via closed-loop control by utilizing O2 sensor feedback.) . Incidentally, I expect the reason for "the pinging engines burning nitrous at the tractor pull" is lean burn resulting from failure to add sufficient fuel to maintain correct fuel/air ratio when the N2O is added.

"Headers" are not only supposed to flow exhaust with less back pressure than stock manifolds, but also are supposed to generate pulses of negative pressure to increase volumetric efficiency. Those negative pressure waves reduce pumping losses of the engine and actually "suck" exhaust gas out of the combustion chamber. They only generate those pressure waves around the engine RPM for which the pipes are tuned. The principle is harmonic resonance (the same principle a pipe organ uses to amplify sound): the longer the pipes, the lower the resonant frequency and the lower the RPM at which flow is enhanced. Back pressure drastically inhibits the scavenging effect, so pretty much ever since the advent of catalytic converters the benefit of headers has been limited. Additionally, headers tubes need to be equal-length for maximum flow (~31" long for higher RPM power gains, ~36" for lower RPM band), and there is no power/efficiency benefit from using special heat-insulating coatings/paints. (I suppose headers look nice to some people when the hood is open though. I reckon that is the primary benefit for street-driven vehicles these days.) Note that in the above picture, the layout is 2 3-into-1 collectors that funnel into another 2-into-1 collector farther downstream. None of the primary tubes are of equal length. nor are they long enough to generate scavenging at any practical engine speed for a 4.0. (Just eyeballing them, tubes that short would be tuned for maybe 12,000 or more RPM. It is beyond ridiculous to call them "long tube headers", and only the ignorant, the imaginative, and/or the disingenuous would do so.) To produce significant power gains in 4.0 you would be looking for 2 separate 3-into-1 collectors with 33"-36" equal-length primary pipes that feed into a dual exhaust system with no catalytic converters, glass-pack mufflers with no baffles (or else no mufflers at all), and tailpipes exiting somewhere behind the doors. Such a system would be LOUD - but that is the hallmark of pipes that actually boost power.

. Could be they didn't do a dynamic balance, or that they screwed up a static balance. Easiest way to tell if they did a static balance is if there are only wheel weights on one side (usually inner side of the wheel, because some customers complain about visible weights on the outer side detracting from the beauty of fancy alloy wheels). Though static balance is fine in the vertical plane, tires are also out of balance in the lateral plane to some (greater or lesser) degree. This typically shows up at 50-55 mph, and can become quite violent when in combination with other factors such as big tires, lifts, and any front end problems otherwise so marginal as to go otherwise unnoticed until triggered and amplified by harmonic oscillation.

. At what sort of speed?

. Agreed. . Off-road capability that depends in large part on the superior articulation of solid-axle suspension is part of Jeep's heritage and brand recognition. Abandoning that will cost them sales to some degree in the long run, I am sure, because even though independent suspension (front AND rear) is superior for the street where most miles are driven, when people buy Jeep they are buying the image of capability and rugged individualism, even if they never once take it off the pavement. I guess fulfilling the irrational desires of the consumer that drive marketing is diametrically opposed to the cost of lawsuits that result from rollover accidents... and that the financial bottom line balancing projected lost sales against legal costs is ultimately what will drive the final design decision.

^ I think everything he said was on target. . Independent suspension is the right way to go for street driving, which is where 99.X% of the miles accumulated are driven. Safety not only of the occupants but also everyone in other vehicles operating in proximity would be enhanced, as would be handling and road manners in general. . I would like to see a solution that offers modification for better off-road performance (all the way to the extreme), but I don't see a profit there for the manufacturer. I therefore fear this may be the beginning of the end for unrestricted off-road modding of Jeeps, and probably for other makes as well.

^ Well-said, and good examples too! . We should move on to the OP's question of how to get crazy power levels out of an AMC 2.5 4-banger. He ain't gonna like the answer, because it is so technically difficult that it would be impractically expensive, but let's go there just for fun. Everybody should chime in, so I'll just throw out a starting point and let you guys find solutions, no matter how bizarre or expensive. . Let's say we want to make 1,000 hp at 10,000 rpm - what would it take for us to build that engine? Start with figuring out the thrust per stroke, then consider the block - look at the main bearing journal webbing - is it sufficient to handle the thrust? How about the crankshaft? Pistons and rods? What do we need to hold the head on with to keep it from separating from the block?

. That would be because you are American - the rest of the world's 6.8 billion people use newton-meters (not pound-feet). Even professionals in the US use newton-meters, but for convenience of old farts like us who are too stubborn to change they convert figures to pound-feet. . Gogmorgo is right - precision and clarity do matter (I am sure his professors have drummed that into his head in his studies). That said, in the context it was presented (after adding 7 psi of boost) only pound-feet made sense to "ASSume" as the correct unit.

Well an XJ would look like this (if I remember right) after 7 rolls at 45 mph. And yes she's fine, she walked away with a broken figure. Sorry for the tinny picture, it was texted to me a couple years ago when I first got my xj. It was my female friend at the time, best friend Image Not Found I am happy to hear of her good fortune on the injury front. That flattened roof is oh so common in XJ rollovers ( and probably our MJ's, too, I just lack evidence) and usually occurs during the first roll or two. Then as long was your body is below the beltline after the failure you have the stronger portion of the body protecting you. Imagine being tightly strapped to a high-back bucket as that roof caved... If the roof bent you back or didn't bend you at all and you took the full force of the collapse... . That right there is the best argument I have seen and heard for installing some kind of rollover protection.