Factory Limits Torque in 1st and 2nd
JK Junkie
Joined: Jul 2009
Posts: 2,343
Likes: 1
From: The San Andreas Fault
More than likely it will not go WOT in first or second in order to allow effective use of EGR in the 3.8s. The old 4.0s were nice engines because they didn't need to pass any stringent emissions standards. And as everyone knows the reason they switched the new Jeeps to run the 3.8 is to pass emissions standards.
BTW, they could have probably (if they even tried) passed stringent 50 state emissions with the 5.7L HEMI driveline and possibly improved their CAFE ratings.
JK Super Freak
Joined: Jan 2009
Posts: 1,462
Likes: 3
From: Aurora, CO
The now late 4.7l would have been a better choice in both regards.
Thread Starter
JK Newbie
Joined: Oct 2009
Posts: 4
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From: Hermosa Beach, CA
Thanks!
JPop, So Cal Tay 12, ronjenx, Foo, GoodysGotaCuda, pearl-drum-man, CJ7nvrstk, dmhines, Atl JK, tpm152, spin lock, and anyone I just missed -
I appreciate that you took the time to respond.
JPop, I take your SC contact as the final word - The torque limiting I feel is not imagined.
Thanks for defining a fix! Sold.
JPop, So Cal Tay 12, ronjenx, Foo, GoodysGotaCuda, pearl-drum-man, CJ7nvrstk, dmhines, Atl JK, tpm152, spin lock, and anyone I just missed -
I appreciate that you took the time to respond.
JPop, I take your SC contact as the final word - The torque limiting I feel is not imagined.
Thanks for defining a fix! Sold.
JK Junkie
Joined: Jul 2009
Posts: 2,343
Likes: 1
From: The San Andreas Fault
The 5.7l "Hemi" is far from a clean running engine. They barely got it to pass emissions by running two spark plugs per cylinder and using speed density programming. Among other things that I can't recall off the top of my head... The '09+ version might be better, I don't know much about it. It also isn't known for its fuel efficiency and would not have made a CAFE improvement.
The now late 4.7l would have been a better choice in both regards.
The now late 4.7l would have been a better choice in both regards.
My line of thinking more along the lines of the 5.7L which has similar MPG ratings as the 3.5L in the Charger. Sometimes larger engines with more low end torque can provide more or equal fuel efficiency as smaller engines, because they can operate in the lower RPM band.
JK Super Freak
Joined: Jan 2009
Posts: 1,462
Likes: 3
From: Aurora, CO
I defeinitely agree there. I wish a LSx engine bolted in like the Hemis do. I think a fuel efficient V8 would be great.
Hell, my 4.7l WJ got 22 mpg at 80 mph because it had a fuel efficient V8 with good power/weight ratio and a low cruising RPM.
Hell, my 4.7l WJ got 22 mpg at 80 mph because it had a fuel efficient V8 with good power/weight ratio and a low cruising RPM.
JK Junkie
Joined: Jul 2008
Posts: 3,017
Likes: 0
From: Lakewood, OH
More than likely it will not go WOT in first or second in order to allow effective use of EGR in the 3.8s. The old 4.0s were nice engines because they didn't need to pass any stringent emissions standards. And as everyone knows the reason they switched the new Jeeps to run the 3.8 is to pass emissions standards.
Part of these pesky emissions standards are NOx (which comes from high stoichiometric combustion temps, especially before the catalytic converters have a chance to get up to operating temps). One of the easiest ways to keep NOx down is to recirculate exhaust (EGR = exhaust gas recirculation) so that the "fresh" charge going into the cylinders have not only less oxygen available because the exhaust has displaced it (hence you inject less fuel for stoich combustion) but the mixture with all the CO2 and water has a higher specific heat, so you reach even lower peak combustion temps.
The reason why the throttle wouldn't open all the way for effective ERG use is to draw a vacuum in the intake to pull the exhaust gases through the EGR loop and back in the intake.
Part of these pesky emissions standards are NOx (which comes from high stoichiometric combustion temps, especially before the catalytic converters have a chance to get up to operating temps). One of the easiest ways to keep NOx down is to recirculate exhaust (EGR = exhaust gas recirculation) so that the "fresh" charge going into the cylinders have not only less oxygen available because the exhaust has displaced it (hence you inject less fuel for stoich combustion) but the mixture with all the CO2 and water has a higher specific heat, so you reach even lower peak combustion temps.
The reason why the throttle wouldn't open all the way for effective ERG use is to draw a vacuum in the intake to pull the exhaust gases through the EGR loop and back in the intake.
Last edited by JPop; Oct 8, 2009 at 03:00 PM.