SergeantChuck

People use SC for both all the time. When I typed it I did not even think about that. You got me laughing

I wish I had one. One day.

yo_marc

The A/F ratio in the dyno chart caught my eye... 12.21:1 stock sounds fat. I believe 12.6 would be ideal under load... but I suppose that could be debatable.

Someone posted further up that the rich A/F ratio is likely why people are seeing gains with the Viber TB. I agree...

FlyinRyan

Hey guys, new to the forum, but not new to Jeeps.

The Viper TB is really a 4.7 TB- the Viper uses TWO of the 4.7 TBs to supply air.

I have not really done any work on the 3.8, but I have worked extensively with the 3.7s used in the KJs/WKs. On the 3.7 anyways the intake manifold inlet is 67mm and quickly tapers to 65mm. The "Viper" TB is 74mm. I dont know what the inlet diameter is on the 3.8 but I would imagine it is the same if not slightly larger. this creates a mismatch between the TB and the intake manifold, inducing unwanted turbulence.

What I have done with great results and zero drivability issues is simply take the stock casting , and taper port it to the stock blade, then reverse taper it to the intake manifold inlet.

I too doubt the 20whp difference.

I have access to Diablo CMR software and although I havent played with a 3.8 file, I would imagine there is more being left on the table.

CerOf

Hypertech's new upgrades to their chip is to include a tune for the viper TB. That will be interesting to see the results there.

Ryan0260

I agree....

FlyinRyan

It's a figure of expression. Would you sleep better at night if I said molding?

ALEXANDERJASON

i read this before i went to bed last night. i slept much better...

barrett_fodder

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.

BF

tslewisz

Excellent post. Thanks for that, and for your service to our country.

Bgut

On the 2 different runs the later has many mods added and the first has no mods.
What are the final drive gears and are they auto or are they manuals. Also are the tires the same size or are they the stock tires?
If there is a difference this may be why on dyno has higher gain then the other.
I believe both runs but "all has to be equal to compare results".