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Old 09-24-2011, 09:27 PM   #61
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Yeah, I can't comment on the manuals, but


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Originally Posted by kjeeper10 View Post
Hence a Tuner or uh um.... SprintBooster

The stock throttle response in the pre 12 jk is toned down for a couple reasons. no secret... Glad they worked it out.
With the sprint booster I don't have to wind it out to 3000+ before I shift. I would hit 2300 ish-depress the clutch and give it gas, the rpms would sink to under 2000 before it cought up.. We all no the 3.8 performs poorly under 2000 rpms. A tuner has been noted to help also with TR.

Don't know if regearing would help. Plus most people regear for bigger tires and/or the AT.
Have not seen a performance regear yet.
With my 5.38s and in 2hi, all shifts, including downshift on demand (foot) are very quick and abrupt--

Now in 4lo--GADZOOKS-HANGON TO YOUR TEETH--when I drive in 4lo "D", the shifts are LIGHTNING/JARRING

Need someone with some 5.13/5.38 --(manual) advice and there ain't many !

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Old 09-24-2011, 09:42 PM   #62
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Quote:
Originally Posted by JIMBOX
Yeah, I can't comment on the manuals, but

With my 5.38s and in 2hi, all shifts, including downshift on demand (foot) are very quick and abrupt--

Now in 4lo--GADZOOKS-HANGON TO YOUR TEETH--when I drive in 4lo "D", the shifts are LIGHTNING/JARRING

Need someone with some 5.13/5.38 --(manual) advice and there ain't many !

JIMBO
Ya I know but

You have 33's correct?

So your 5.38's puts you in the the performance range. Heck, the 4 speed auto needs at least what? 4.88's to be comparable to a rubi with 4.10's

With the manual 4.56's would be similar with stock 32's. (too you)
I could not justify spending that much money going from 4.10 - 4.56

I would really like to find someone who has 4.88's and a manual.. And see how that goes

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Old 09-24-2011, 10:01 PM   #63
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Heh Heh, just let me say one more thing tonight--


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Originally Posted by kjeeper10 View Post
Ya I know but

You have 33's correct?

So your 5.38's puts you in the the performance range. Heck, the 4 speed auto needs at least what? 4.88's to be comparable to a rubi with 4.10's

I could not justify spending that much money going from 4.10 - 4.56

I would really like to find someone who has 4.88's and a manual.. And see how that goes
For the 42rle auto/wrangler 4.56 is a total abomination and should never be used in a jeep--There's no difference in it's use for 32" tires and a complete failure in 33" tires-

4.88 ring/pinion is the MININUM RATIO, that anyone should pay good money for a regearing --manual/auto

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Old 09-24-2011, 11:35 PM   #64
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I've had 4wd Taco's and an FJ. The 4.0 is easily stronger and sounds right but the slush box in the FJ was the reason I bought a 12 Wrangler w/6spd. Not sure about the 3.8 but this motor is way better than the old straight 6s of old.
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Old 03-10-2015, 01:40 PM   #65
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I am sorry to bring this tread back from the dead, but does anyone know why there is such an abrupt jump in torque at 1800ish RPM on the 3.6. While driving my manual lightly, it's almost like turbo lag when you hit this RPM. You get a noticeable push. I usually stay above this point anyway, but it's noticeable to me starting off and driving very lightly when the shift Pont brings the RPM below this point and climbs past it again.
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Old 03-10-2015, 03:29 PM   #66
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Look at the power and torque curve chart.
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Old 03-10-2015, 04:45 PM   #67
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Mixed reviews? Where have you seen a negative review of the 2012?
must have been on consumer reports
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Old 03-10-2015, 05:45 PM   #68
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Look at the power and torque curve chart.
This. The cam and heads don't flow efficiently at lower RPMs. As a result, the engine feels sluggish until it gets into the RPM range where it's designed to run.

If anyone were to come out with a set of cams that moved the torque curve down to where the engine makes good off-idle torque, I would install them in a heartbeat. I wouldn't care if the torque dropped off above 5000 RPM or even a little lower. A Jeep doesn't need a high RPM screamer of an engine as much as it needs a stump puller.
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Old 03-10-2015, 06:26 PM   #69
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This. The cam and heads don't flow efficiently at lower RPMs. As a result, the engine feels sluggish until it gets into the RPM range where it's designed to run.

If anyone were to come out with a set of cams that moved the torque curve down to where the engine makes good off-idle torque, I would install them in a heartbeat. I wouldn't care if the torque dropped off above 5000 RPM or even a little lower. A Jeep doesn't need a high RPM screamer of an engine as much as it needs a stump puller.
Torque can be arbitrarily manipulated by gearing. The Pentastar provides more than enough torque under just about any conceivable offroading situation, particularly with the Rubicon transfer case. Let it rev. That simple. Geared properly, the 3.6 absolutely blows away both the 3.8 and 4.0 under all circumstances.
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Old 03-10-2015, 06:54 PM   #70
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Torque can be arbitrarily manipulated by gearing. The Pentastar provides more than enough torque under just about any conceivable offroading situation, particularly with the Rubicon transfer case. Let it rev. That simple. Geared properly, the 3.6 absolutely blows away both the 3.8 and 4.0 under all circumstances.
Most certainly. Plans for the 4 speed Atlas are in the works. Still, more low end torque would never be a bad thing.
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Old 03-10-2015, 07:04 PM   #71
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Most certainly. Plans for the 4 speed Atlas are in the works. Still, more low end torque would never be a bad thing.
No, not a bad thing at all. And I am intentionally exaggerating - truthfully, gearing IS constrained to some extent (by OEM availability, etc.) and it also makes an offroad vehicle easier to drive if you don't need a lot of throttle to move under high load situations.

I am a big fan of the Pentastar. But, I am not the type to worry about over-revving their engine. When I merge, chances are pretty good I am going to the floor with my foot and letting the trans shift at the redline. I do not think it will hurt anything.
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Old 03-10-2015, 11:17 PM   #72
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This. The cam and heads don't flow efficiently at lower RPMs. As a result, the engine feels sluggish until it gets into the RPM range where it's designed to run.

If anyone were to come out with a set of cams that moved the torque curve down to where the engine makes good off-idle torque, I would install them in a heartbeat. I wouldn't care if the torque dropped off above 5000 RPM or even a little lower. A Jeep doesn't need a high RPM screamer of an engine as much as it needs a stump puller.
I see the torque curve and it's definitely felt. My question is why. It's an unnatural, almost exponential jump, where normal torque curves are just that, not such an exaggerated line. My question is why. It looks like it's intentional or computer controlled IMO.

As far as off idle torque, it would be nice. Especially for the 6sp as I have, but the only way that is happening is with a V8 or Diesel and a heavy flywheel. This engine has got enough torque to get it rolling without throttle as long as you are not in a hurry. Then if you are, you are immediately shifting as my exprience is with the 3.73. 2nd is a little high to start in unless you are on a slight hill or have plenty of time to let the clutch out gradually and very easy with a tad bit of throttle. I don't like to fell that chatter of a slipping clutch when not necessary.

Quote:
Originally Posted by i82much View Post
No, not a bad thing at all. And I am intentionally exaggerating - truthfully, gearing IS constrained to some extent (by OEM availability, etc.) and it also makes an offroad vehicle easier to drive if you don't need a lot of throttle to move under high load situations.

I am a big fan of the Pentastar. But, I am not the type to worry about over-revving their engine. When I merge, chances are pretty good I am going to the floor with my foot and letting the trans shift at the redline. I do not think it will hurt anything.
IMO this engine does not mind to be revved and mine has seen redline a few times , merging onto the highway and...well once racing my buddies 5.7l Tundra lol. I have found, although it does not mind revving, the power is linear but there is not as much to be gained from taking it to redline as with some engines. The pull is roughly the same from 3500 to 5000 to me. However the couple times I have ripped through 1st and 2nd has been slightly impressive for a Wrangler. It could be considered quick'ish at low speeds (up to 45). Granted I am a 2dr sport 6sp with 3.73's. I will say if you boot it in 1st, you better damn well be ready to shift very quickly, and get it right.

Overall it's not a bad engine, especially street oriented and the torque is way more than useable. But, I would also be happier with a lower revving engine with more torque since it's not a speed machine.
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Old 03-10-2015, 11:59 PM   #73
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I get why the engine is the way it is. It has to live in several platforms for cost effectiveness. The only way I see them adding meaningful torque down low is to increase displacement or force air in to it. 3.6l isn't a large motor to start with in a vehicle that weighs this much.
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Old 03-11-2015, 12:00 AM   #74
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Quote:
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I see the torque curve and it's definitely felt. My question is why. It's an unnatural, almost exponential jump, where normal torque curves are just that, not such an exaggerated line. My question is why. It looks like it's intentional or computer controlled IMO.
Volumetric efficiency is a complicated topic to explain on a message board.

Essentially, the valves open too far and too long for the engine to efficiently draw in the right amount of air given the design of the intake manifold. The piston isn't moving fast enough. But once the engine reaches a higher RPM range, the pistons are moving faster, drawing in more air faster which takes advantage of the design of the camshaft and the intake manifold.
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Old 03-11-2015, 12:02 AM   #75
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I get why the engine is the way it is. It has to live in several platforms for cost effectiveness. The only way I see them adding meaningful torque down low is to increase displacement or force air in to it. 3.6l isn't a large motor to start with in a vehicle that weighs this much.
A different set of camshafts and a different intake manifold would move the operating range of the engine. But there would have to be a big enough market for a company to spend the R&D money. And because you can compensate with gears, there isn't as much of a market as there could be so we probably won't see anyone make anything like that.
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Old 03-11-2015, 12:13 AM   #76
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A different set of camshafts and a different intake manifold would move the operating range of the engine. But there would have to be a big enough market for a company to spend the R&D money. And because you can compensate with gears, there isn't as much of a market as there could be so we probably won't see anyone make anything like that.
I understand that. Also most of the time the change in cams and intake don't add much torque it pushes the torque higher to a higher rpm. Bring this torque down would help a little but at the end of the day it's still not as much as people would like. They do a good job of making that as broad as possible with variable cam timing. At the end of the day I still hold on to my answer for this application to add substantially large torque increases.
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Old 03-11-2015, 12:36 AM   #77
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this thread was dead for four years and someone brought it back. I get flamed for bringing up a three week old thread..... go figure!
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Old 03-11-2015, 12:44 AM   #78
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Look at the power and torque curve chart.
Someone call for charts? I have one right here in my handy chart folder.

What problem are we trying to solve today?

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Old 03-11-2015, 01:51 AM   #79
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So I don't know if this is what you are looking for, but I went on a long trip with mine. I use a gas card that keeps track of my mileage. Last month I averaged 18.6 miles per gallon. I have about 6500 miles on my Willys. I go off roadiing every weekend. Not always rock crawling but some sort of off road. I really like the set up. There is quite abit of weight added due to the winch and bumper but so far I am Pretty happy.
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Old 03-11-2015, 10:47 AM   #80
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I have found, although it does not mind revving, the power is linear but there is not as much to be gained from taking it to redline as with some engines. The pull is roughly the same from 3500 to 5000 to me.
Umm... this actually means there definitely IS much to be gained from taking it to redline. It's a nearly flat torque curve, with power increasing fairly linearly all the way up to redline. It only "pulls roughly the same" throughout most of the rpm range within the same gear. As soon as you shift up a gear, you'll have less torque multiplication through the transmission, and less "pull" than if you would have stayed in the lower gear to redline.
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Old 03-11-2015, 11:26 AM   #81
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Yep. Unless you have a theoretically perfect CVT, you always want to shift AFTER the horsepower peak to maximize acceleration.
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Old 03-11-2015, 07:22 PM   #82
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Looks negligible below 1500. I'm impressed with the overall performance. I have a auto.
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Old 03-11-2015, 09:01 PM   #83
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Auto with 4.10 gears helps a lot out of the hole or from a rolling start.. I raced a F250 diesel with a turbo spooling and smoke bellowing from his loud pipes and I spanked him.

The hillbilly didn't have a clue what went down...

It was like deliverance - but reversed roles.

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Old 03-11-2015, 09:11 PM   #84
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This will solve all your problems ;-)


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Old 03-12-2015, 11:20 AM   #85
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When I first got my 2015 JKU I was not familiar with it yet and stepped on the pedal too hard on dry pavement. It spun the tires and peeled out a bit.

I let off the gas immediately but it shocked the hell out of me that it could do this.
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Old 03-12-2015, 04:08 PM   #86
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This will solve all your problems ;-)



Maybe. Cubic inches have to be a plus for low end torque, no way around it. Having said that, my Corvette needs to be wound up to get any power or throttle response from it, just like my JK. Both high winding sports car motors, IMO. Gearing makes the 3.6 usable, especially off-road, even though it's not a "truck motor", IMO.

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