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Discussion Starter #1 (Edited)
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

http://www.jk-forum.com/forums/modified-jk-tech-2/viper-throttle-body-dyno-sheet-192536/

The dyno sheet looks too good to be true, I suspect that some tuning also happened.


This response sounds about right.
http://www.jk-forum.com/forums/modified-jk-tech-2/viper-throttle-body-dyno-sheet-192536/page6/#post2786836

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
4.7L vs 3.7L (not my pic)
 

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Let us know if it does something? I could see it improving power with no drawback or improving top end power with low end driveability suffering some OR I can see it making no change at all.

You can't flow more through the TB than you can through the stock air intake and filter before it. And I don't really know how much restriction is the stock setup, but if you try a bigger TB and see no gains at all, I'd add a CAI or something to free up the flow before the TB. As well, you can't flow more into the motor than you can flow out of it, so its also possible that the 3.5" is more than big enough for the 3.7L and adding a bigger TB does nothing, you need bigger cams and freer flowing exhaust before it starts to suck more air needing a bigger TB.
 

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Discussion Starter #3
Let us know if it does something? I could see it improving power with no drawback or improving top end power with low end driveability suffering some OR I can see it making no change at all.

You can't flow more through the TB than you can through the stock air intake and filter before it. And I don't really know how much restriction is the stock setup, but if you try a bigger TB and see no gains at all, I'd add a CAI or something to free up the flow before the TB. As well, you can't flow more into the motor than you can flow out of it, so its also possible that the 3.5" is more than big enough for the 3.7L and adding a bigger TB does nothing, you need bigger cams and freer flowing exhaust before it starts to suck more air needing a bigger TB.
Agreed with you on all points here Mongo.

If I see some improvement in throttle response to compensate for the lazy DBW system then I will be happy. Its certainly cheaper than the resistor trick (Sprint Booster $$$).

More power and rumored MPG would be nice. We shall see :)
 

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Discussion Starter #4 (Edited)
I also want to point out that I am not completely in uncharted territory here.


A couple members on another forum have successfully completed this mod on 3.7L's
http://www.jeepforum.com/forum/f67/viper-throttle-body-3-7l-1492188/index2.html
ca07wk said:
With the Volant intake and 4.7l tb I've seen a gain of about 2mpg average driving 50/50 city highway. Before I was at 15.5 recently I've seen 17 maxing at 17.5

http://www.jeepforum.com/forum/f67/viper-throttle-body-3-7l-1492188/

Input from a Liberty owner as well
http://www.jeepforum.com/forum/f67/seeking-more-performance-out-my-3-7-a-2616274/index2.html
Gageraid said:
Just added that throttle body to my Liberty. I also have a Hypertech programmer, exhaust, and CAI. This mod dramatically improved EVERYTHING!
Not sure what gains you would see stock, but with these mods, it's money well spent.
 

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I also want to point out that I am not completely in uncharted territory here.


A couple members on another forum have successfully completed this mod on 3.7L's
http://www.jeepforum.com/forum/f67/viper-throttle-body-3-7l-1492188/index2.html



http://www.jeepforum.com/forum/f67/viper-throttle-body-3-7l-1492188/

Input from a Liberty owner as well
http://www.jeepforum.com/forum/f67/seeking-more-performance-out-my-3-7-a-2616274/index2.html
So the question folows, if these gains can be achieved by just swapping to a part that is already in the inventory for the manufacturer, and I can't imagine how identical TB's just with a different bores would make costs a factor in that decision, then why didn't the manufacturer just do it themselves already???

NOT to be overly skeptical, but that is the legitimate counter claim to those bogus products with people claiming a spark plug with an extra electrode or a $5 sheetmetal swirl will make your engine have so much more power and mileage, they don't, and if their claims were true the manufacturers would be using those products in their cars from the assembly line.

So, to still keep an open mind, there must be some drawback to this mod that prevented the manufacturer NOT selecting the bigger TB from the beginning, and I suspect it may be the beuracratic testing and design criteria for the vehicles that is at the root of it. I.e. the drawback is probably some low speed driveability losses, that for a better (or at least more mechanically conscience) driver are so easily adaptable too, that its unoticeable for them.

I suspect that is the reason behind the lazy DBW, there are probably design and test criteria that are more for liability of stupid drivers that drive the design that way. i.e. if it has the slightest lurching characterstics during parking maneuvers, no matter what gains in mileage or power, NOPE, that out, reduce TB size until the lurch is gone. Otherwise we'll end up with a class action lawsuite on our hands and half our customer base is soccer moms that would reject the vehicle on a test drive at the dealership, simple because it's harder to park.

So I guess I'm saying I'm a tad skeptical, but open minded, it might be true and the reason why such a simple mod actually working in defiance of the common sense (of why didn't chrysler do it before you) is because if you're NOT a soccer mom driver then the disadvantages are insignficant.
 

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Discussion Starter #6 (Edited)
A very popular, valid counter argument.

I definitely appreciate your candor Mongo! This point has been made on other forums as well, although typically in a more condescending way.
 

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Discussion Starter #7
So the question folows, if these gains can be achieved by just swapping to a part that is already in the inventory for the manufacturer, and I can't imagine how identical TB's just with a different bores would make costs a factor in that decision, then why didn't the manufacturer just do it themselves already???

NOT to be overly skeptical, but that is the legitimate counter claim to those bogus products with people claiming a spark plug with an extra electrode or a $5 sheetmetal swirl will make your engine have so much more power and mileage, they don't, and if their claims were true the manufacturers would be using those products in their cars from the assembly line.

So, to still keep an open mind, there must be some drawback to this mod that prevented the manufacturer NOT selecting the bigger TB from the beginning, and I suspect it may be the beuracratic testing and design criteria for the vehicles that is at the root of it. I.e. the drawback is probably some low speed driveability losses, that for a better (or at least more mechanically conscience) driver are so easily adaptable too, that its unoticeable for them.

I suspect that is the reason behind the lazy DBW, there are probably design and test criteria that are more for liability of stupid drivers that drive the design that way. i.e. if it has the slightest lurching characterstics during parking maneuvers, no matter what gains in mileage or power, NOPE, that out, reduce TB size until the lurch is gone. Otherwise we'll end up with a class action lawsuite on our hands and half our customer base is soccer moms that would reject the vehicle on a test drive at the dealership, simple because it's harder to park.

So I guess I'm saying I'm a tad skeptical, but open minded, it might be true and the reason why such a simple mod actually working in defiance of the common sense (of why didn't chrysler do it before you) is because if you're NOT a soccer mom driver then the disadvantages are insignficant.
Something to consider is that bean counters make silly choices/oversights that don't make sense to the end user all the time. :icon_confused:

Something that comes to mind to me right off the bat is that darned LCA bolt that welds itself in place. :sick:
 

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I havent looked at any of the threads posted here on the tb swap but would love to do this mod AFTER my muffler goes. I'd get an aftermarket exhaust, then go about the 4.7 tb install.
 

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A very popular, valid counter argument.

I definitely appreciate your candor Mongo! This point has been made on other forums as well, although typically in a more condescending way.
Something to consider is that bean counters make silly choices/oversights that don't make sense to the end user all the time. :icon_confused:

Something that comes to mind to me right off the bat is that darned LCA bolt that welds itself in place. :sick:
Actually, I'm thinking they are making a decision that makes the most sense, because what drives their decisions are what choices will "Sell the Most Cars" and what choices "Limits are Liabilities from Class Action Suite Lawyers".

If there were no Soccer Mom's or Idiot Drivers buying Jeep's, and there were no Class Action Suite Lawyers, then 3.7L would probably come from the factory with the bigger TB. And you I without a thought would modify our driving habits in a parking lot, knowing the vehicle can lurch a bit at very low speeds, accellerate slow and coast as much as possible while driving around the parking lot and parking.

On the flip side;
Look at the banner in my signature, if all the vehicles owners in this country understood how the car manufacturers are intentionally locking consumers and independent mechanics out of repair/diagnostic information as a barrier to competition and as a revenue stream scheme, do you think there would NOT be an uproar?

Unfortunately, if one manufacturer were to actaul buck the others and say, "We're going to stand by our customers and make the repair/diagnostic information readily available". 0.3% of the customers would cheer and rush to them and buy their cars, which means they'll lose money compared to all the other manufacturers raking in the doe for the rights to their proprietary tools and the big bucks for their dealerships, that the other 99.7% will still keep going to because they know no better, nor could be bothered to learn, and will buy a car based on no better criteria than "they like the way it looks" or "it presents the image I want to project". So the ignorance of the consumer allows them to get away with murder.
 

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Discussion Starter #10
Ok, finally got a chance to pop the hood on the commander.


New TB and the resonator box are the same diameter. Gonna have to get a silicone sleeve and clamps...



 

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Discussion Starter #11
Ordered a 3"-3" silicone coupler and 2x Tbolt clamps from https://www.siliconeintakes.com for ~$15

Will get this thing put on next week I hope.

Side note:
I am considering replacing the flexpipe with their straight silicone tube, stainless couplers, and t-bolt clamps for ~$45
 

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I'm curious to hear your results.
 

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Discussion Starter #14
Got this bad boy in the mail today.

Will likely trim the silicone a bit as it seems longer than I need.

TBolt clamps are nice

 

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any progress on this project?
 

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Discussion Starter #16 (Edited)
any progress on this project?
Yep, to some minimal degree.

With my factory intake silencer box I had a hard time getting it connected to the MUCH larger TB. Had to remove the strut tower bar to get it lined up, which meant removing the fuse boxes on the drivers side.

As usual I do things the hard way and attemped install @ midnight bc I couldnt sleep.

After install the idle was @ 1500rpm and dropped to 1000rpm. It was cycling the TB a lot and making a loud clunking noise( i assume shutting the TB completely) and then RPMs would drop below 500 and it almost died several times. By this time it was 1:30am and my wife had to drive it to work in the morning so I bailed. Thought the TB may be not functioning properly.

Put the stocker back on. Will try it again when I have the chance to drive it for a few days in a row so she doesnt have to deal with the crazy idle.

Come to find out later that this is pretty normal, and it takes some significant time for the computer to figure out the TB. :sick:

Side note was that in my case the opening for the itnake manifold behind the TB was a bit smaller than the T opening. Some dremel action should fix that a bit.

Will keep you updated!
 

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Had to remove the sway bar to get it lined up, which meant removing the fuse boxes on the drivers side.
Sorry to be a Nit-Noid, but you mean the tie bar, right?

Don't want to confuse someone that tries this and he pulls the actual sway bar off the bottom of the vehicle, when its the tie bar over the engine that needs to be pulled.

I may even have the wrong name for it, but its the bar that goes over the top of the engine, that is a very tight fit with the intake box, that ties to the two strut towers together.

On another note; if the opening in the intake manifold was smaller than the larger TB, do you think the butterfly plate in the larger TB might be rubbing the edges of the opening in the intake manifold? Might explain the huge hunting at idle. BUT, I see it totally plausible that the PCM is going to take a while to learn and correct the idle for the bigger TB.
 

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Discussion Starter #18 (Edited)
Sorry to be a Nit-Noid, but you mean the tie bar, right?

Don't want to confuse someone that tries this and he pulls the actual sway bar off the bottom of the vehicle, when its the tie bar over the engine that needs to be pulled.

I may even have the wrong name for it, but its the bar that goes over the top of the engine, that is a very tight fit with the intake box, that ties to the two strut towers together.

On another note; if the opening in the intake manifold was smaller than the larger TB, do you think the butterfly plate in the larger TB might be rubbing the edges of the opening in the intake manifold? Might explain the huge hunting at idle. BUT, I see it totally plausible that the PCM is going to take a while to learn and correct the idle for the bigger TB.
Yes! Much appreciated, I mean the bar that connects the strut towers!


Regarding the butterfly hitting the intake manifold -> I had considered that. I am able to open it by hand and it does not come into contact.
 

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Thats good that the butterfly plate does NOT contact the intake manifold and drag.

I suspect the bigger TB changes the idle way outside the stock settings programmed into the PCM, and it has going to have to hunt way outside the baseline setting before it find the right position that holds the idle.

I don't know on the commander, but I have heard on other vehicles that people swap TB or Cams that require more air for idle, of them filing down edges on the butterfly to let more air by, then the PCM adjust for one of the lower settings at closed or almost closed to idle the motor. I'd only try that if you've given the PCM more than enought time to adjust and it just can't do it. Taking it for a drive will probably help it adjust as well.
 

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Discussion Starter #20
Thats good that the butterfly plate does NOT contact the intake manifold and drag.

I suspect the bigger TB changes the idle way outside the stock settings programmed into the PCM, and it has going to have to hunt way outside the baseline setting before it find the right position that holds the idle.

I don't know on the commander, but I have heard on other vehicles that people swap TB or Cams that require more air for idle, of them filing down edges on the butterfly to let more air by, then the PCM adjust for one of the lower settings at closed or almost closed to idle the motor. I'd only try that if you've given the PCM more than enought time to adjust and it just can't do it. Taking it for a drive will probably help it adjust as well.
Good idea :)
 
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