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Unread 05-04-2010, 12:10 PM   #16
Area.3.Fiftyone
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I was reading this thread last night before all of the additional replies.

I took my 2.5 liter powered Jeep (31" tires) on it's maiden voyage today to get some parts from the junk yard. I went about 30 miles on Interstate 81 and was not at all pleased with the performance of the little 4 banger trying to make it up some hills.

5th gear was totally out of the question except on long, flat straights and even in 4th it seemed to struggle going up the hills.

You guys are saying that the 4.0 throttle body will help in this area? I could get one cheap and would be willing to give it a shot.

Is there a particular year range to look for in the throttle body? My motor is a 93 if that matters.

Thanks in advance.

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Unread 05-04-2010, 12:30 PM   #17
djsmith1174
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I would look in the 4.0L pre 95' range. YJ, Cherokee, or Grand I believe are all the same. I believe some of the later models had a MAP port that you have to plug up adding some additional work.
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Unread 05-04-2010, 12:33 PM   #18
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Is there any TB mods for us TBI guys running 90 and older?
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Unread 05-04-2010, 06:38 PM   #19
xdgt03
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Part of the problem with the 4.0l tb swap is that the intake manifold inlet is smaller than the 4.0l tb. It actually could hurt because the lip of the inlet would cause the air coming in to churn. This cuts down on the velocity of the air flow through the tb and into the intake runners. Velocity is an important factor in airflow. Ideally, you would have a long intake runner that starts large and gradually tapers to the size of the tb or even slightly smaller. Stillen makes intakes like this. Also, most stock IM's intake ports are smaller than the intake port on the head. This is on purpose.

Based upon the spray pattern of the oe injectors, I think the Ford injectors are the best place to start. It only really makes sense to clean them first. The ones I got were not terrible but they definitely improved in their spray pattern with the cleaning. Plus I found that one of the injectors was not working well. You could not know this unless you cleaned them first.

I think I will try to get a spare IM and port and it and check to see if there is any port matching that could be done at the head.

This is all very minor stuff on these long stroke 4 bangers. You can squirt perfume on a turd but it's still a turd.
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Unread 05-04-2010, 08:26 PM   #20
moonshinefuel
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This is why it is important to stress not to drop too much money into this persuit, because the outcome is very minimal for a lot. For me, I know results can be achieved, but they are minimal, and I don't mind, it is fun to experiment. Its not a ricer engine, it is different. The 2.5 is an excellent engine for durability when treated and maintained correctly. An outstanding engine. If just do little things here and there that people are presenting in this thread over a span of time, it all can add up to that extra response that makes it a little more fun. The key is don't overspend, have fun doing this. Little things do add up, no, it is not replacing displacement, but it does help for me. I already run a non-chambered magnaflow muffler, (as my stock one was toast, so I replaced it with that), a mandrel bent tailpipe, very high quality spiral wound spark plug wires, a performance coil, which the stock one needed replacing anyways, and put an airiad intake system in. (Which I did not need, but hey, I like it, so what) . I also run a approx 50% alcohol fuel blend a majority of the time, which gives it that special spirit. I have no regrets doing the things I have done already, nor unreasonable expectations. Look, the factory airbox is stuffy, it does not help to have a flex tube, the whole thing is kind of restricting. But the factory air filter is a good filter though. So, save money, get a nice form fitting smooth flow air tube only, from the airbox, to the TB, that would be a nice, very inexpensive way to get that air flowing better. I say this because I believe factory air filters do filter better than the aftermarket cone filters. It is amazing to me how my computer handles such a high blend of alcohol over the years, so, I am very intersted to see how it would do with a mild cam with the things I have done so far. I think just a little more mild than stock and my computer would have little to no problem with it, but I have not tried it yet, so that I am just tossing in the air. When I replaced my oil pump, I can tell my cam has seen better days, so, what the heck, I need a new cam anyways, why not step it up a little, gonna have to shell out anyways.
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Unread 05-04-2010, 08:53 PM   #21
pot_father
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This is all helpfull. I have to mash the peddle to the floor to get to 65 in 5th gear and I have stock wrangler wheels on it. I hate getting passed by a crx, and around here everyother mexican has one. I am going to have to find me a taurus fan also that was a good idea.
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Unread 05-05-2010, 06:27 AM   #22
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Yeah, you should be able to do better than that with stock wheels. Also, if you haven't looked, check your exhaust pipe from the exhaust manifold to the tailpipe. Mine was mashed under the trans and that caused too much back pressure. I took out my cat and am running a 3 chamber dynomax muffler with 2.25" pipe. It is to loud for cruising. At some point I will add a resonator.
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Unread 05-05-2010, 06:39 AM   #23
Area.3.Fiftyone
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All of the stuff moonshinefuel mentions (except for the cam) can be done for little to no money. I have access to tons of Jeeps and can get another intake, Ford injectors and throttle body for about $20 to experiment with.

I already did the air box mods (pulled out the restrictions) and have replaced my whole exhaust as well. The PO did a real hack job on the exhaust system so I replaced it with stuff I had laying around including: Thrush welded muffler (Flowmaster clone IMO) and a 2 1/2" stainless steel mandrel bent exhaust pipe that is supposed to be for an S10 pickup truck but fits the Jeep perfectly.

I knew going into this particular project that it would never be a speed demon and I bought it as a DD for mostly around town stuff, back and forth from my house to the shop, for parts pickups, etc. It does really well in town but the highway performance was a little less than what I expected.

I'd like to squeeze whatever I can out of it without spending a ton of cash. I could easily swap in a 4.0 motor, but that is not the point for this particular rig. I'm trying to get the best fuel mileage I can out of the 2.5 dropped into basically a rolling brick.

What does everyone recommend for a coil upgrade and do they make a header for the 4 banger?
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Unread 05-05-2010, 09:07 AM   #24
xdgt03
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This is one should work ACCEL 140021 - ACCEL Mopar Remote Super Coils - Overview - SummitRacing.com
It has more voltage and less resistance. I would not change unless yours is bad.

I only run NGK V-Power copper plugs in everything but my Caravan (because they are a biotch to change). This will probably get people all flamed up but copper plugs are better than any other plug be it iridium, platinum, etc... Copper conducts electricity best and with less resistance. The others are good for longevity and not bad, just not as good.

Magnacore wires are the best wires made IMO. I run them on my autox car. I don't run them on the Jeep because it is huge overkill but if you got a spare $125 laying around, you can try them.

The best way to maximize power output from the engine (without building/boring/proting etc...)is increasing airflow so the PCM will increase fuel flow. More gas means more power. You can also get a air/fuel controller where you can increase the fuel in the a/f ratio. This is best done on a dyno which is overkill. But, through trial and error you can probably get close. The problem is that we operate on a wideband o2 system and that adjusts a/f ratios between 1 and 4volts. This is not very accurate. A narrowband system is better since it is far more adjustable. I'm not sure how this would be done (or if it can but I assume so) but again, this would probably be overkill.

Much of the things you do to free up or add hp with bolt on sort of mods lower torque. Torque is really the important number. Hp is directly connected but whatever is done should not sacrifice torque for hp. Opening the exhaust too much with too big of pipe, too open a muffler, removal of the cat, can lower back pressure too much. This has a direct negative affect on torque. Obstructing air volume and velocity both lowers hp and torque. This seems obvious because of what happens with dirty air filters. But lowering velocity because of the 4.0L tb or too big an CAI (cold air intake) can lower torque even if hp is raised.

For every action there is an equal and opposite reaction. There is a counter point to everything. It is a matter of finding the right balance. And in the end I'm guessing that we can do no better than gain 15hp (freeing) and 15ftlb torque with exhaust, intake, and fan mods. Not too shabby for the relative cost. An a/f controller costs around $200 and might get you another 5 to 8 in both hp and tq.

A guy here had a good thread about porting and polishing the head on a 2.5L He did it himself and took most of the valve guides off. This is not good in the long run but if you only put a few thousand miles on your rig a year, it will last a very long time. I think he got 25 dyno'd whp (I don't remember the tq number but it was higher). That is a lot. That would make a big difference. I haven't read that thread in a long time but I remember it seeming legit.

rambling over
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Unread 05-05-2010, 09:41 AM   #25
moonshinefuel
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Xdgt03, pardon my ignorance on some of what you have mentioned above but are talking about a type of an over-ride to the 02 sensor such as a polarity switch, and and affecting air/fuel in that manner by manipulating the voltage? That kind of has an unfavorable reaction with the computer and or sensors in the jeep doesn't it? It sees that as a problem and tries to make corrections I would think, or no? Or are you talking about making adjustments through the pcm? I would have reservations with it only because of my own unknowns with it, but for the savvy knowledgable person, it is very interesting, all of what you have stated. That is a lot, facinating.
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Unread 05-05-2010, 11:13 AM   #26
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Quote:
Originally Posted by pot_father View Post
This is all helpfull. I have to mash the peddle to the floor to get to 65 in 5th gear and I have stock wrangler wheels on it. I hate getting passed by a crx, and around here everyother mexican has one. I am going to have to find me a taurus fan also that was a good idea.
Get used to being passed by people in all kinds of vehicles of all ethnicities. There is a thread that shows a 2.5L YJ pulling 66hp on an accelerometer. If you are a type A driver then you might have the wrong vehicle.

The Wrangler hits a wall aerodynamically at about 60mph so you can stand on the gas all day and you won't go much faster.

I like riding in the slow lane at 60mph listening to Los Lobos and not caring if I get anywhere fast.
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Unread 05-05-2010, 11:19 AM   #27
xdgt03
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No Problem. A controller works by intercepting the signal between the car's air flow meter (MAP or MAF. FI YJ's have MAP) and the ECU (PCM for Jeep). The controller is the device that tells the ECU how much air is entering the engine so that the ECU can add the correct amount of fuel.

The ECU calculates the proper ratio of fuel to air for a stock, unmodified engine. Certain engine modifications can cause the engine to require more fuel. Since the stock ECU thinks that it knows how much fuel it is putting into the engine based on the stock injector size and the stock fuel pressure, making certain modifications may allow for more fuel. There is a standard a/f mixture of 14.7 to 1. That is 14.7 parts of air to 1 part of fuel. You cannot push this ratio because the ECU, no matter what you do to the engine, will always adjust to 14.7 to 1. With a controller, you can make the ratio more fuel rich. This can give you more "bang". There is a point of diminishing return. The controller gives you the means to adjust the amount of fuel that the ECU injects into the engine by modifying the signal from the air flow meter. This can be done at specific RPM levels. This way you can tell the engine that a certain amount more air is flowing into the engine at a specific RPM than is really entering the engine, and the ECU will add that much more fuel.

On a YJ, there is only one o2 sensor. This sensor can be bypassed to run in open loop. Open loop is what it is in when the engine is cold or at start up. This means the engine runs with a greater than 14.7 to 1 a/f ratio. Once an engine warms, it goes into closed loop, or default 14.7 to 1 ratio. The PCM should not compensate because you are intercepting the signal at the 1st and only o2 sensor and making the PCM think it is in open loop. In OBDII systems there is a second o2 sensor that monitors after the cat and justifies what it reads with what the front o2 sensor is doing and the ECU compensates as needed.

Does that make sense? I think I confused myself lol
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Unread 05-05-2010, 08:59 PM   #28
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That is very very interesting. So 14.7:1 air fuel ratio except on start up, or when cold, it is greater. So it acts as a choke then right? when the ratio is higher, it serves the warm up process. And from what I can see a controller could be used instead of replacing the injectors, just use a controller to manipulate, in a round about way, the stock injectors. It seems like that might work. It is also interesting that the 02 sensor comes into play like it does, so to speak. For me, in discussing oxygen, I know alcohol fuel has a much higher oxygen content than regular 100% gasoline. I have been using 50% alcohol blend with my gasoline for years. My 02 sensor must be recognizing that in some way or form, its much higher in oxygen. I guess my thought is I am very surprised how my computer seems to be ok with it. I don't get trouble codes, and my 02 sensor seems to last longer. I have no E85 conversion kit in it. I am thinking it must be a testement to a computer that can make some adjustments. I have actually run 85% alcohol and 15% gas for weeks without coding at one time. Now, it is really really fiesty at that ratio, and not advisable, however, I have done it, and it did work. What I am thinking is a controller might be a good thing for a person like me especially if I get a mild cam, and running a high blend of alcohol in the fuel. But is it worth it since we run a wide band 02 sensor, and it may not be a good candidate for a controller?
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Unread 05-05-2010, 11:30 PM   #29
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Originally Posted by xdgt03 View Post
No Problem. A controller works by intercepting the signal between the car's air flow meter (MAP or MAF. FI YJ's have MAP) and the ECU (PCM for Jeep). The controller is the device that tells the ECU how much air is entering the engine so that the ECU can add the correct amount of fuel.

The ECU calculates the proper ratio of fuel to air for a stock, unmodified engine. Certain engine modifications can cause the engine to require more fuel. Since the stock ECU thinks that it knows how much fuel it is putting into the engine based on the stock injector size and the stock fuel pressure, making certain modifications may allow for more fuel. There is a standard a/f mixture of 14.7 to 1. That is 14.7 parts of air to 1 part of fuel. You cannot push this ratio because the ECU, no matter what you do to the engine, will always adjust to 14.7 to 1. With a controller, you can make the ratio more fuel rich. This can give you more "bang". There is a point of diminishing return. The controller gives you the means to adjust the amount of fuel that the ECU injects into the engine by modifying the signal from the air flow meter. This can be done at specific RPM levels. This way you can tell the engine that a certain amount more air is flowing into the engine at a specific RPM than is really entering the engine, and the ECU will add that much more fuel.

On a YJ, there is only one o2 sensor. This sensor can be bypassed to run in open loop. Open loop is what it is in when the engine is cold or at start up. This means the engine runs with a greater than 14.7 to 1 a/f ratio. Once an engine warms, it goes into closed loop, or default 14.7 to 1 ratio. The PCM should not compensate because you are intercepting the signal at the 1st and only o2 sensor and making the PCM think it is in open loop. In OBDII systems there is a second o2 sensor that monitors after the cat and justifies what it reads with what the front o2 sensor is doing and the ECU compensates as needed.

Does that make sense? I think I confused myself lol
You are mostly correct. A MAP sensor does not interpret air flow, it interprets pressure. Also the vehicle speed sensor comes into play. As you mentioned, at idle, cold starts or operating temps the system is in open loop and follows the map completely and adjust just according to the Manifold Air Pressure (MAP). In light acceleration and cruise profile(Vehicle speed sensor) the computer could care less about the MAP sensor. Its in closed loop and is looking a the o2 sensor. The narrow band o2 sensor have such a narrow band that it really doesn't ever hit 14.7 to 1, it just says I am leaner or richer than 14.7 to 1 and hunts up and down around that magical number. Now only when the computer is triggered by Wide Open Throttle(WOT) does the MAP sensor come back into play. The Throttle position sensor triggers this.

IF you add lots of air with mods, at WOT you can be running lean. Since the MAP sensor cant tell that it getting more air than stock it injects so much fuel for a certain RPM according to its fuel map. The MAP controllers adjust the voltage signal to fool the computer to think that more or less pressure is present so more/less fuel at WOT will be injected. So in cruise or other situations the MAP controllers really do very little, its more just during acceleration.

Moonshinefuel, are you running ethanol or methanol? The o2 sensor and the computer could really care less if its alcohol, propane, gasoline, methane(natural gas). The problem with using alcohol in concentrations over ~15 percent is that many parts of your fuel system are damaged by it. Fuel pumps, o rings, regulators, injectors, and fuel lines on your jeep unless they have been retrofitted are not rated to handle alcohol. You are damaging your engines fuel system by running high concentrations of alcohol, unless you vehicle is a flexfuel. If it ethanol its slower to damage than methanol but it still does, its just a matter of time before it rears its head. Flexfuel vehicles do typically modify the timing slightly to take advantage of ethanols higher resistance to spark knock to partially offset its lower btu content/lower fuel economy/lower power. A engine designed to run on pure alcohol has a very high compression ratio, of 15 to 1, running alcohol in a lower compression engine is a waste of money (ethanol is more expensive per mile) unless you have a special/free source of alcohol.

Also you talk as if you have a wide band o2 sensor but if your asking questions about them I highly doubt you do? Wide band sensors are not plug and play into stock systems, only a few specialized aftermarket ecus can effectively use them. They are typically add on sensors with a gauge or data logger that is completely divorced from the ECU/fuel system that is used as a tool for tuning and checking the state of tune.
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Unread 05-05-2010, 11:49 PM   #30
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Originally Posted by xdgt03 View Post
But lowering velocity because of the 4.0L tb or too big an CAI (cold air intake) can lower torque even if hp is raised.

For every action there is an equal and opposite reaction. There is a counter point to everything. It is a matter of finding the right balance.
Your making the assumption that the factor 2.5 air intake system is/was already optimized from the factory. Adding air does not mean necessarily that it WILL kill torque. To much of any thing is not good but I noticed no difference what so ever of low end toque, but a noticeable gain a 2300rpms plus. Have you even done this mod along with opening the intake manifold to match? Doesn't sound like it?
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