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Old 10-07-2011, 01:52 PM   #1
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Another boring lecture by Mr. Sinister: This time about bolt on performance parts.

WARNING!! Long and boring technical mumbo-jumbo to follow.
I was going to post this in the "Horsepower Boost" thread, but I didn't want to spam it up and get off topic in his thread, and open it up for discussion, as there's a bunch of pretty knowledgeable folks in here.

Keeping in mind that the 3.6 makes 20 more horsepower in the Challenger with nothing different between the two other than the air intake, according to Chrysler. A CAI on this engine might be worth investigating.
What concerns me about the 3.6, is the loop in the exhaust. As a guy who has spent many years tuning fuel injected engines, and with Chrylser claiming the loop is there to "make the engine run right", this tells me that these engines are very sensitive to changes. I'm curious to know, but fairly certain that the tune on the Wrangler's computer is also different than that of the Challenger, because of the change in air intakes. If I knew this for sure, it would confirm my theory.
These differences alone don't mean much, but when you put the pieces together, it tells me you aren't going to be able to do much in the way of performance mods on the 3.6 without a computer reflash to optimize the tune for the parts you added. It's not a big deal, and I'm sure Superchips/Diablo/Whomever are working on tuners for the 2012 as we speak. You might not cause any issues changing parts and not changing the tune, but you also might not see any power gains, and maybe even some torque losses. Many modern engines are like this, as engines become more complicated and computer controlled. Every single sensor in your Jeep is measuring some parameter millions of times per minute, and if they measure something that isn't in acceptable parameters, you get a check engine light.
A custom tune will tell the computer the new acceptable parameters, and the computer can then compensate added airflow with added fuel, timing, etc. This is where almost everyone goes wrong with bolt on parts on modern injected engines. Simply increasing airflow isn't the whole picture. The computer can usually compensate to avoid a check engine light, but only inside it's predetermined acceptable parameters. So you get more air in and out with things like CAI kits, throttle bodies, headers (not on the 3.6, obviously), and exhausts. But, the computer can't typically add enough fuel and timing to totally compensate, due to it's limitations to operate inside of it's predetermined parameters.
In the old days, you could simply re-jet your carburetor and go. Even with some of the more rudimentary fuel injection systems (like the old 5.0 Mustangs), you could really get away with murder on the stock tune, since the computer wasn't as much of an interference. You were still limited by the mechanical capabilities of the engine, but it was much easier to get great power gains from bolt on parts. In the case of the 3.6, and having looked at it's architecture and numbers, I'm thinking this engine is limited more by electronic nannying than by mechanical limitations. It looks like it has great potential to make horsepower, but I believe proper tuning will become necessary to achieve optimum results, much like the import guys have to do. Handheld tuners work well, but they can never provide the same results a custom tune can, because every engine is just different enough. I can attest to this having modded a couple turbocharged imports. The custom tunes made a noticeable difference, even over the canned handheld tunes. Canned handheld tunes take the things that are the same with every particular engine, and make a general tune for added airflow. This works fine, but you just can't get the same level of power as you can by going in and measuring each engine's particular numbers, and compensating for them.

Discuss.

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Old 10-07-2011, 02:08 PM   #2
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I agree with you, absolutely.

So can I get 20 hp with a CAI on my TJ?

LOL just kidding

I think that there is a ton of capability for the 3.6 as well, but only if every part of the system is addressed like you said. many people dont understand you can slap a part on and it will help, but there are ways to optimize your gains.

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Old 10-07-2011, 02:12 PM   #3
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Great writeup! That exhaust loop really scares me when it comes to performance mods to the 2012 Wrangler. I can't help but think any mods are going to be difficut because as you mentioned: "Chrylser claiming the loop is there to "make the engine run right", this tells me that these engines are very sensitive to changes." I'm thinking they worked long and hard on that Loop and it was the only choice they had, otherwise it wouldn't be there. I can't wait to see what comes out in the aftermarket to tweak the 3.6 in the Wrangler. I think its a fantastic platform, but time will tell.
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Old 10-07-2011, 02:19 PM   #4
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Originally Posted by GoldenSahara00 View Post
I agree with you, absolutely.

So can I get 20 hp with a CAI on my TJ?

LOL just kidding

I think that there is a ton of capability for the 3.6 as well, but only if every part of the system is addressed like you said. many people dont understand you can slap a part on and it will help, but there are ways to optimize your gains.
Actually, you make a good point. The 4.0 is an engine that is pretty well optimized in stock form, considering it went largely unchanged for a long time. It's limitations in stock form are mechanical, since there isn't much in the way of complicated electronics on it. The differences over the years with the 4.0 were largely mechanical.
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Old 10-07-2011, 02:21 PM   #5
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Originally Posted by demarpaint View Post
Great writeup! That exhaust loop really scares me when it comes to performance mods to the 2012 Wrangler. I can't help but think any mods are going to be difficut because as you mentioned: "Chrylser claiming the loop is there to "make the engine run right", this tells me that these engines are very sensitive to changes." I'm thinking they worked long and hard on that Loop and it was the only choice they had, otherwise it wouldn't be there. I can't wait to see what comes out in the aftermarket to tweak the 3.6 in the Wrangler. I think its a fantastic platform, but time will tell.
Thanks!! I like talking performance.
I believe the reports are that the loop doesn't exist on the 4-door, due to the longer wheelbase. If the loop isn't there, it all but confirms it. Even if it is, it's still there to "make the engine run right".
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Old 10-07-2011, 02:22 PM   #6
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I fully agree, that did not cross my mind in the other thread. The problem is, where & how could your average Joe get a custom tune done if he does not near a major city with a shop that can do this? I do not state this in arguemenative form & hope to retrieve some insight of what someone could do (if even possible) to make the computer accept mild to moderate mods until they could get to a shop that can perform a custom tune.

Also, how much would each computer in the YJ engines, TJ enjines, JK engines, XJ engines, etc. react/accept these mods without having issues that would require a skilled proffessional to perform a tune?

Thanks,
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Old 10-07-2011, 02:27 PM   #7
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Originally Posted by Mr. Sinister View Post
Actually, you make a good point. The 4.0 is an engine that is pretty well optimized in stock form, considering it went largely unchanged for a long time. It's limitations in stock form are mechanical, since there isn't much in the way of complicated electronics on it. The differences over the years with the 4.0 were largely mechanical.

Which is why I love it. simple and easy to understand. also easy to upgrade. You just don't do anything

but really, you can improve performance but its all mechanical. stroker kits, turbos, and all that. not so much as the computer inhibiting it.
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Old 10-07-2011, 02:32 PM   #8
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Thanks!! I like talking performance.
I believe the reports are that the loop doesn't exist on the 4-door, due to the longer wheelbase. If the loop isn't there, it all but confirms it. Even if it is, it's still there to "make the engine run right".
If the Loop isn't in the 4 door, do you think it would be easier to modify as a result?
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Old 10-07-2011, 02:44 PM   #9
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I fully agree, that did not cross my mind in the other thread. The problem is, where & how could your average Joe get a custom tune done if he does not near a major city with a shop that can do this? I do not state this in arguemenative form & hope to retrieve some insight of what someone could do (if even possible) to make the computer accept mild to moderate mods until they could get to a shop that can perform custom a custom tune.

Also, how much would each computer in the YJ engines, TJ enjines, JK engines, XJ engines, etc. react/accept these mods without having issues that would require a skilled proffessional to perform a tune?

Thanks,

Well, he can't unfortunately. Some companies offer services that let you ship them your computer, they do the custom tune based on your mods, then ship it back to you. This works marginally better than a canned tune, but they still can't tune in real time, using real time data. But, I wouldn't worry too much. Since the 3.6 is now Chrylser's fleet V6 engine, you will see aftermarket support, I reckon. This means that if I'm right, custom tuning shops worth their salt are going to have the software to tune the 3.6, even the little guys. Basically, any shop with a dyno and a computer with the software can do custom tunes. A guy with some tuning knowledge is also helpful, lol. That's why handheld tuners are so popular, for the guys who don't want to squeeze every possible HP from their combo, and are ok with sacrificing a few hp or a dead on tune for convenience of doing it themselves.

The YJ and TJ fuel injected engines are more or less the same. The computers in both models are not very intrusive, and will be more forgiving. Custom tuning will still maximize your bolt on mods, but isn't typically necessary. You can't just bolt a blower or do a head and cam swap on a 4.0 without reprogramming and expect it to run right, so that's a pretty good indicator of how far you can go on the stock tune.
Like the 3.6, the 3.8 is also going to benefit from tuning for your mods. The 3.8's computer is fairly intrusive from what I have seen. Ripp's blowers come with a tuner for a reason. They'll do the job, but you almost always will pick up noticeable power with a custom tune when adding a blower.
I put a blower kit from a reputable company on my buddy's 03 Mustang GT, and it ran pretty damn good. There were a couple flat spots in the canned tune that came with the kit, so we got it custom tuned at a local shop. The custom tune not only increased driveability, but it also found another 30rwhp while still being safe enough as to allow you to beat the snot out of the car, and not have it shred it's internals. The difference was really worth the cost, and I personally put the wood to that car on many occasions, and it soaked it all up.

Ideally, you do you bolt on parts in bunches. Do a few at a time, then get a custom tune. Doing a tune every time you do a mod will definitely get the most out of each part you add, but it's pretty expensive to do it that way.
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Old 10-07-2011, 02:46 PM   #10
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If the Loop isn't in the 4 door, do you think it would be easier to modify as a result?
Not necessarily, because you're still deviating from the factory setup. The tune is probably the same between the 2 and 4 door models, because the computer will think the exhausts are the same, due to the loop in the 2 door to effectively make it longer.
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Old 10-07-2011, 03:05 PM   #11
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Originally Posted by Mr. Sinister View Post
Well, he can't unfortunately. Some companies offer services that let you ship them your computer, they do the custom tune based on your mods, then ship it back to you. This works marginally better than a canned tune, but they still can't tune in real time, using real time data. But, I wouldn't worry too much. Since the 3.6 is now Chrylser's fleet V6 engine, you will see aftermarket support, I reckon. This means that if I'm right, custom tuning shops worth their salt are going to have the software to tune the 3.6, even the little guys. Basically, any shop with a dyno and a computer with the software can do custom tunes. A guy with some tuning knowledge is also helpful, lol. That's why handheld tuners are so popular, for the guys who don't want to squeeze every possible HP from their combo, and are ok with sacrificing a few hp or a dead on tune for convenience of doing it themselves.

The YJ and TJ fuel injected engines are more or less the same. The computers in both models are not very intrusive, and will be more forgiving. Custom tuning will still maximize your bolt on mods, but isn't typically necessary. You can't just bolt a blower or do a head and cam swap on a 4.0 without reprogramming and expect it to run right, so that's a pretty good indicator of how far you can go on the stock tune.
Like the 3.6, the 3.8 is also going to benefit from tuning for your mods. The 3.8's computer is fairly intrusive from what I have seen. Ripp's blowers come with a tuner for a reason. They'll do the job, but you almost always will pick up noticeable power with a custom tune when adding a blower.
I put a blower kit from a reputable company on my buddy's 03 Mustang GT, and it ran pretty damn good. There were a couple flat spots in the canned tune that came with the kit, so we got it custom tuned at a local shop. The custom tune not only increased driveability, but it also found another 30rwhp while still being safe enough as to allow you to beat the snot out of the car, and not have it shred it's internals. The difference was really worth the cost, and I personally put the wood to that car on many occasions, and it soaked it all up.

Ideally, you do you bolt on parts in bunches. Do a few at a time, then get a custom tune. Doing a tune every time you do a mod will definitely get the most out of each part you add, but it's pretty expensive to do it that way.
That makes sense & I fully agree.

For the 4.0 I6 guys, would a CAI, larger throttle body, 24# injectors, new fuel pump, ported/polished intake, & aftermarket exhaust work well without the custom tune? Personally, I would have them give it a once over anyway, but would it still be worth their time & money?
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Old 10-07-2011, 03:39 PM   #12
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I've said this before and I don't expect it to be any more popular this time than last time, but we aren't going to see any big improvements to the 3.6 for a reasonable amount of money. I suspect the extreme bottom end might be improved with some tuning, but the amount of torque it makes for its size is in the same ball park that a world class engine builder can get out of an engine.

Where the improvements will be is beyond 5000 rpm where few of us drive very often, and significant gains are going to cost big bucks and involve heads and cams. In the simplest of terms, the torque you make is determined by how much air you can put in the engine at one time and power is determined by how much you can put in the engine in a period of time. You can make more power by spinning it faster. The only solution for substantially more torque in the midrange is to make the engine bigger or force feed it. There may a little more torque on the table from tuning, but the talk we had before about 300 ft-lbs isn't going to happen without getting more air into the cylinders by either making them bigger or going to artificial aspiration.
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Old 10-07-2011, 04:12 PM   #13
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Originally Posted by Mr. Sinister View Post

Keeping in mind that the 3.6 makes 20 more horsepower in the Challenger with nothing different between the two other than the air intake, according to Chrysler.

Its the calibration....

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Originally Posted by Mr. Sinister View Post
A CAI on this engine might be worth investigating.
What concerns me about the 3.6, is the loop in the exhaust.
Its only for equal length..

Quote:
Originally Posted by Mr. Sinister View Post
As a guy who has spent many years tuning fuel injected engines, and with Chrylser claiming the loop is there to "make the engine run right", this tells me that these engines are very sensitive to changes. I'm curious to know, but fairly certain that the tune on the Wrangler's computer is also different than that of the Challenger, because of the change in air intakes. If I knew this for sure, it would confirm my theory.
Im positive you are right and I can find out for sure..

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These differences alone don't mean much, but when you put the pieces together, it tells me you aren't going to be able to do much in the way of performance mods on the 3.6 without a computer reflash to optimize the tune for the parts you added. It's not a big deal, and I'm sure Superchips/Diablo/Whomever are working on tuners for the 2012 as we speak. You might not cause any issues changing parts and not changing the tune, but you also might not see any power gains, and maybe even some torque losses. Many modern engines are like this, as engines become more complicated and computer controlled. Every single sensor in your Jeep is measuring some parameter millions of times per minute, and if they measure something that isn't in acceptable parameters, you get a check engine light.
A custom tune will tell the computer the new acceptable parameters, and the computer can then compensate added airflow with added fuel, timing, etc. This is where almost everyone goes wrong with bolt on parts on modern injected engines. Simply increasing airflow isn't the whole picture. The computer can usually compensate to avoid a check engine light, but only inside it's predetermined acceptable parameters. So you get more air in and out with things like CAI kits, throttle bodies, headers (not on the 3.6, obviously), and exhausts. But, the computer can't typically add enough fuel and timing to totally compensate, due to it's limitations to operate inside of it's predetermined parameters.
In the old days, you could simply re-jet your carburetor and go. Even with some of the more rudimentary fuel injection systems (like the old 5.0 Mustangs), you could really get away with murder on the stock tune, since the computer wasn't as much of an interference. You were still limited by the mechanical capabilities of the engine, but it was much easier to get great power gains from bolt on parts. In the case of the 3.6, and having looked at it's architecture and numbers, I'm thinking this engine is limited more by electronic nannying than by mechanical limitations. It looks like it has great potential to make horsepower, but I believe proper tuning will become necessary to achieve optimum results, much like the import guys have to do. Handheld tuners work well, but they can never provide the same results a custom tune can, because every engine is just different enough. I can attest to this having modded a couple turbocharged imports. The custom tunes made a noticeable difference, even over the canned handheld tunes. Canned handheld tunes take the things that are the same with every particular engine, and make a general tune for added airflow. This works fine, but you just can't get the same level of power as you can by going in and measuring each engine's particular numbers, and compensating for them.

Discuss.

The limitations you speak of are called torque managment, and yes the PCM will pull out anything that exceeds those limits via timing retard and throttle closure. It exists to protect the physical limits in the transmission... And yes some of us are working on it
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Old 10-07-2011, 04:16 PM   #14
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I would say that reflashing with a new intake could be said of a lot of new vehicles were the computer controls everything. I would bet the 3.8 could even benefit from CAI if someone could come up with a tuner to compensate for the new add ons.
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Old 10-07-2011, 04:31 PM   #15
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Speaking of performance mods, I wonder what it takes to do this to the I-6!

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Old 10-07-2011, 05:23 PM   #16
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To make any engine run at optimum, especially after adding bolt on power adders, to maximize this you need a real deal tune at a shop.

Just previously said, any good performance shop can do this for relatively cheap.. $450. By porting and polishing, adding great air flow, exhaust flow, ignition, and fuel you can increase the horsepower indefinitely. But the old addage is true, unless you have a performance engine that is able to use everything you put at it, you wont gain much.

My good friend added a custom milled intake and manifold to his lt1 super street camaro and gained 50hp, 65ft lb torque... But then again the intake cost 2500.
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Old 10-07-2011, 05:36 PM   #17
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Originally Posted by Mr. Sinister View Post
Thanks!! I like talking performance.
I believe the reports are that the loop doesn't exist on the 4-door, due to the longer wheelbase. If the loop isn't there, it all but confirms it. Even if it is, it's still there to "make the engine run right".
I believe the loop is on the four doors can somebody with a 2012 confirm?
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Old 10-07-2011, 05:52 PM   #18
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The loop is on the 4 door as well.
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Old 10-07-2011, 05:54 PM   #19
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You most certainly CAN boost the 4.0's numbers significantly without tuning, but it takes a LOT of stickers...
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Old 10-07-2011, 05:56 PM   #20
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That makes sense & I fully agree.

For the 4.0 I6 guys, would a CAI, larger throttle body, 24# injectors, new fuel pump, ported/polished intake, & aftermarket exhaust work well without the custom tune? Personally, I would have them give it a once over anyway, but would it still be worth their time & money?
Well, with all that work, you're not going to see a tremendous improvement unless you port/polish the head, maybe add larger valves, and do a cam swap. The heads have to be able to flow the added air in and out, and the cam will need to be changed to allow the vales to open further and stay open longer to get the mixture in and out. This is where the total picture come into play. You hit the mechanical limitations of the factory parts. It would certainly be worth the effort if your ultimate plan was to do the head and cam work.
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Old 10-07-2011, 06:01 PM   #21
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I've said this before and I don't expect it to be any more popular this time than last time, but we aren't going to see any big improvements to the 3.6 for a reasonable amount of money. I suspect the extreme bottom end might be improved with some tuning, but the amount of torque it makes for its size is in the same ball park that a world class engine builder can get out of an engine.

Where the improvements will be is beyond 5000 rpm where few of us drive very often, and significant gains are going to cost big bucks and involve heads and cams. In the simplest of terms, the torque you make is determined by how much air you can put in the engine at one time and power is determined by how much you can put in the engine in a period of time. You can make more power by spinning it faster. The only solution for substantially more torque in the midrange is to make the engine bigger or force feed it. There may a little more torque on the table from tuning, but the talk we had before about 300 ft-lbs isn't going to happen without getting more air into the cylinders by either making them bigger or going to artificial aspiration.
You may be right. There is a mathematical formula for figuring out torque potential by displacement, but I can't remember it right now. Mechanically, I doubt the 3.6 will support much more than 300-320 lb/ft naturally aspirated. It already makes decent torque given it's displacement, thanks to the dual overhead cam design.

I think with the horsepower potential in this engine, you'll start seeing more guys revving them and adding a ton of gear. I'm excited to see some head, cam, and stroker packages become available for it.
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Old 10-07-2011, 06:06 PM   #22
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Its the calibration....


The limitations you speak of are called torque managment, and yes the PCM will pull out anything that exceeds those limits via timing retard and throttle closure. It exists to protect the physical limits in the transmission... And yes some of us are working on it
It very well could be, I'm just going with what Chrysler has said themselves.

Even beyond torque management, we need to look at fuel injector duty cycles, max timing possible before detonation, port velocity, max lift and duration possible, things like that. That's why I'd love to see some head and cam packages, as I stated just above.
It's good to know people see the potential in this engine, keep us updated!!
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Old 10-07-2011, 06:08 PM   #23
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I would say that reflashing with a new intake could be said of a lot of new vehicles were the computer controls everything. I would bet the 3.8 could even benefit from CAI if someone could come up with a tuner to compensate for the new add ons.
It's true, some cars won't even accept a CAI without needing a reflash. It's strongly recommended on the new Camaro, for one.
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Old 10-07-2011, 06:08 PM   #24
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Well, with all that work, you're not going to see a tremendous improvement unless you port/polish the head, maybe add larger valves, and do a cam swap. The heads have to be able to flow the added air in and out, and the cam will need to be changed to allow the vales to open further and stay open longer to get the mixture in and out. This is where the total picture come into play. You hit the mechanical limitations of the factory parts. It would certainly be worth the effort if your ultimate plan was to do the head and cam work.
That's actually what I am currently doing with mine, I bought another 4.0 so I didn't have my Jeep sitting for a while without a motor in it. I am having the block completely cleaned, bored, honed, decked, etc. Then I am having a multi-angle valve job done along with the porting & polishing, etc.

My current dilema is: I'm not sure what type cam to go with & most importantly, where to find aftermarket cams for the 4.0

I'm sure I just haven't looked under enough rocks yet.
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Old 10-07-2011, 06:10 PM   #25
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Originally Posted by InvertChaos View Post
Speaking of performance mods, I wonder what it takes to do this to the I-6!


Well, apparently a turbo and a 4.6 stroker kit at least.
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Old 10-07-2011, 06:11 PM   #26
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Thought I would add, I have built many performance & race Ford / Chevy V-8's, but this is my first time with the AMC 4.0 I6. (The motor is out of a 94 YJ)

Also, where is the best place to get a stroker kit for it?
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Old 10-07-2011, 06:11 PM   #27
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That's actually what I am currently doing with mine, I bought another 4.0 so I didn't have my Jeep sitting for a while without a motor in it. I am having the block completely cleaned, bored, honed, decked, etc. Then I am having a multi-angle valve job done along with the porting & polishing, etc.

My current dilema is: I'm not sure what type cam to go with & most importantly, where to find aftermarket cams for the 4.0

I'm sure I just haven't looked under enough rocks yet.
I'm sure you can find a shop in Texas that can at least set you up with a regrind, right?
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Old 10-07-2011, 06:13 PM   #28
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Thought I would add, I have built many performance & race Ford / Chevy V-8's, but this is my first time with the AMC 4.0 I6. (The motor is out of a 94 YJ)
My background as well. Carbureted and injected, n/a, nitrous, and boosted. My only limitations have been money!!
It's so easy to do it yourself these days. You can buy complete engine packages that are designed to work together, and assemble them yourself. I just can't do the machine work.
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Old 10-07-2011, 06:16 PM   #29
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I'm sure you can find a shop in Texas that can at least set you up with a regrind, right?
I'm sure around Dallas/Ft. Worth or Houston I could. I'm hoping to find one that someone already makes, I'll just keep looking, or find someone to design a new one.
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Old 10-07-2011, 06:38 PM   #30
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I know Comp and Crane make them. From my understanding, you need to shim the lifter bridges to compensate for the increased lift and keep your preload in check when you gow with an aftermarket cam in the 4.0.
Custom grinds, I can't say I know of anyone.

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