I wanted to start the discussion on this mod. Looks like it had not been mentioned on these boards at all until I brought it up in another thread.
This is commonly referred to as the "Viper" TB swap, as they utilize two of these. The 4.7L mopar vehicles (Jeep included) also use these. Stock 3.7L TB is 2.5" and 4.7L is 3", additionally the intake manifold opening is 3" on all of these vehicles.
I just ordered one, but I wont likely have a chance to install until after my honeymoon so it might be a few weeks...
So 3.8L, 3.7L and 4.7L TB's are interchangable, and quite inexpensive $135 new, $65 used ebay, JY even cheaper I'd imagine.
The Fastman custom ported TB's have become a popular improvement to these vehicles, so the TB is a reasonably accepted restriction according to this train of thought. If similar improvements can be had with an off the shelf item as I suspect then this should be a good low buck option for some people.
Those 3.8l guys seem to like em
The dyno sheet looks too good to be true, I suspect that some tuning also happened.
This response sounds about right.
I'll start with: I'm deployed and no I didn't pack my dyno sheets with me before I left. That said, I purchased and installed one of the viper throttle bodies on my jeep when the discussions first began on this site over a year ago. I have had no problems with it of any kind (7,000 miles) and did not notice the TB having much change in performance with any of the SC tunes loaded vs stock (read: the change in performance came moreso from the change in tunes and the TB had little impact one way or the other). This was prior to the availability of the "Trottle body" program some tuners are now offering so I cant speak to that. With my SC tuner and several runs on the dyno, regardless of tune set we observed a nominal 4hp and 7lbft difference in back to back runs. This was done with 3 runs with stock throttle body, add the new throttle body then do 3 more runs. We then swapped vehicles and did the same thing again with a completely stock JK. This difference was beyond the error/deviation in each of the 3 runs, thus a measurable gain beyond the accuracy of the equipment. On the topic of fuel economy I have noticed no real change one way or the other. The bigger impact is wind speed and right foot weight...
One thing to note is that on the VTB dyno sheets the torque peak did seem to move down about 50 revs in the RPM range.
On the butt dyno it does feel a little more responsive, that probably is based on larger volume of airflow with lower throttle position, similar after effect as changing the pedal responsiveness via a programmer or the like. The sound is difference and slightly lower on the intake side enhanced by a CAI more than the stock airbox as well.
Hopefully this helps those on the fence determine if 4/7 is worth $140, or at least give another users observances to add to the pile.
4.7L vs 3.7L (not my pic)