Increase in mpg w/ 4.7L TB

Scar0 · **Posted:** Thu Sep 04, 2014 10:49 pm

Another update. I still don't have a larger intake tube. I'm having a real hard time finding one I am willing to pay for. Looking for one that is 3-1/8" (TB) then an adapter to go from 3-1/2 (air box) down. Open to any suggestions...

But, I went on a highway trip yesterday. About 10 miles city rest highway, cruise set to 72 Mph.
95 miles, 5.427 Gal. = 17.514 MPG
It will take a bit to make up the $ for the TB, but so far things are looking up.
I'm sure my mileage would be better @ 65, but I can't drive that slow.

RPM hang at cold start up a little. After the engine is warm, no hanging.
No CEL at all and shuts off just fine.

lfhoward · **Posted:** Thu Sep 04, 2014 10:52 pm

Thanks for the update, Scar0. I always look forward to updates to this thread, especially with data. :rockon:

I noticed on my Jeep that the stock intake tube (that says "3.7L" on it) narrows as it enters the throttle body. However, the air box end of the tube is at least 3 inches in diameter. I'm wondering if it would work to just replace this tube with a tube that is consistently 3-inches wide, and thereby keeping the stock air box. That way no CAI would be needed. Would it be possible to use the intake tube from the 4.7? What do you think?

Bmxer524 · **Posted:** Thu Sep 04, 2014 10:56 pm

Someone do it on a 2011 lol. When you guys say the rims hang at the start what do you mean by that? How high are they?

Gageraid · **Posted:** Fri Sep 05, 2014 1:00 am

Bmxer524 wrote:

Someone do it on a 2011 lol. When you guys say the rims hang at the start what do you mean by that? How high are they?

We mean where the rpms are during a cold start.
They are a few hundred rpms higher than usual for the first week or so.
Mine are normal now and have been for quite some time.

Scar0 · **Posted:** Fri Sep 05, 2014 3:42 am

I still have the stock air box in place, so basically that is what I am trying to do.
Right now I have a 3" tube running inside the air box hole and am using an inner-tube as a gasket.
This is an old Pic, since then I have trimmed the tube flush with the lid.

With the K&N filter and RAM air hole in the air box, I have very little air flow restriction.

The problem is that the 3" tube is not large enough to stretch over the new TB. It is also not really strong enough to use a coupler on only the outside of it without reinforcement on the inside. The hose clamp would cause the hose to collapse. So right now I have a coupler on the inside of the 3" tube so I can clamp the outside. The coupler reduces about 1/2 of the new TB opening gained. Kinda defeats the purpose.
The new TB OD is just under 3-1/8" the air box hole is just under 3-1/2" OD.
So if I can find a stiffer 3-1/8" hose I can clamp it directly on the TB and use a 3-1/2" coupler on the air box side to join the two.

I have looked into a OEM 4.7 intake tube, but the shapes just aren't right for what I need.

12KK SFD · **Posted:** Fri Sep 05, 2014 7:54 am

Bmxer524 wrote:

Someone do it on a 2011 lol. When you guys say the rims hang at the start what do you mean by that? How high are they?

I plan on doing it as soon as I find one. But I also need to be on the lookout for an adapter from the stock intake size to the new throttle body. Any idea what size I need?

Marlon_JBT · **Posted:** Thu Sep 11, 2014 2:11 pm

tommudd wrote:

Gageraid wrote:

Come on, Tom. You're regeared. I don't doubt you'd test drive my Jeep with these mods if I handed you the keys. I paid $60 for extra mpg. That's a great deal in my eyes. Feel free to hop on our band wagon when other members do these mods and report back with the same results.

Regeared yes but also larger tires, lots of dead weight ( me :shock:

) and then heavier bumpers/skids etc.
I've never actually driven a KK very far Ted or Marlon never trusted me with theirs :ROTFL:

The only difference between a KJ and a KK as far as I can tell is about 200 additional pounds, and the terrible throttle response.

You can have my keys next time, Tom.

... and I see that I have a new project on my hands here. If this fixes at least the throttle response and nothing else, I'm a happier guy.

Scar0 · **Posted:** Fri Sep 12, 2014 2:22 am

12KK SFD wrote:

I plan on doing it as soon as I find one. But I also need to be on the lookout for an adapter from the stock intake size to the new throttle body. Any idea what size I need?

Stock air box outlet OD is 3-3/8" New TB OD is 3-1/8"

I have given up on finding an intake tube that is 3-1/8" ID.
Spent more hours then I like trying to find something. I even looked at the 4.7L cold air intakes, but they all use 3"- pipes. Go figure!
So once again it is DIY time.
I just ordered some things to make my own intake tube.
First was some pipe insulation with an OD of 3-1/8", it should be here on Wed.
I will then use the pipe insulation as a mold to make my own fiberglass intake tube. The tube will be connected on each end with rubber gaskets and pipe clamps.
Wish me luck, and check back here for updates.

12KK SFD · **Posted:** Fri Sep 12, 2014 7:42 am

Scar0 wrote:

12KK SFD wrote:

I plan on doing it as soon as I find one. But I also need to be on the lookout for an adapter from the stock intake size to the new throttle body. Any idea what size I need?

Stock air box outlet OD is 3-3/8" New TB OD is 3-1/8"

Thank you.

Scar0 · **Posted:** Mon Sep 15, 2014 1:57 am

12KK SFD wrote:

Thank you.

Your welcome. Any luck on finding a TB yet?

12KK SFD · **Posted:** Mon Sep 15, 2014 8:00 am

Not yet. I checked with a "local" salvage place but they don't have anything in stock. I'm not in a huge rush so I'll check their inventory every so often.

Dewphy · **Posted:** Mon Sep 15, 2014 1:13 pm

Thought I would share where Im at with this. I too am currently on the "local" salvage yard hunt (a lot cheaper if you can pick it yourself off the junk vehicle), but I did get my intake installed so I am ready for the TB. Here is what Im working with...

Gageraid · **Posted:** Mon Sep 15, 2014 10:55 pm

^^^^^^^ I like how you used some of the original air box. I might need to try that.

lfhoward · **Posted:** Mon Sep 15, 2014 11:10 pm

Scar0: can anything be done with PVC pipe, or would that be asking for melted plastic and a nasty fire? It looks like you can get it with an inside diameter of 3.166" (close to 3-1/8").
http://flexpvc.com/PVCPipeSize.shtml
They even sell flexible 3" PVC pipes in white, black, or gray.

Edit: just answered my own question.
http://www.dynalabcorp.com/technical_info_pvc.asp
The max temp is 158°F 70°C. I think that would be problematic under the hood. I wonder what kind of plastic Jeep uses for OEM intake hoses?

CPVC is thermoplastic that has a melting temp of 395 °C. This could work, and it is available in 3.042 inch inside diameter.
http://www.harvel.com/piping-systems/ha ... dimensions

Scar0 · **Posted:** Tue Sep 16, 2014 3:02 am

Another drawback. The insulation I planned on using as a mold arrived today, 2 days early. But, I guess the Mfg process is not as strict as some things. It is not 3.125" OD.
Listing was 1-5/8" ID with 3/4" walls (x2), should = 3.125" total diameter. Nope, the walls are almost an inch thick. Total diameter is just under 3-1/2".
So now I'm back to square one and $13.01 shorter in the wallet.

I have scoured the internet looking for something that is 3.125" ID to no avail. :banghead:

@ Dewphy What is the ID of the pipe you are using, brand, and cost(if you don't mind me asking)?

@ lfhoward the melting temp is not an issue as the tube does not contact anything that hot. I've been using a flexible RV sewer hose for 6 years with no issues at all.

Dewphy · **Posted:** Tue Sep 16, 2014 2:29 pm

Scar0 wrote:

I have scoured the internet looking for something that is 3.125" ID to no avail. :banghead:

@ Dewphy What is the ID of the pipe you are using, brand, and cost(if you don't mind me asking)?

No worries, it was just an intake kit off ebay from the seller Trackracing for $55. I believe the tubes have a 3" ID. I chose it since it wasnt that stupid dual filter design and from the pictures it looked like the filter would sit right where the stock air box was and it did. I have to note that originally it didnt fit since the coupling that went from the tube to TB was 3" to ~3.5" for some reason (gonna give the seller a call). So i just ran to autozone and grabbed a 3" to 3" coupling and thats what you see in the pics.

I have thought about modifying the tubes (cut them shorter ect.) so they route to the stock air box and just couple the outlet of the box to the inlet of the tube assembly. Unless i see problems from the elements making it to the air filter and until I get a TB, I wont worry too much about this.

NAMoulton1 · **Joined:** Tue Aug 12, 2014 7:01 pm **Posts:** 1054

Scar0 wrote:

Another drawback. The insulation I planned on using as a mold arrived today, 2 days early. But, I guess the Mfg process is not as strict as some things. It is not 3.125" OD.
Listing was 1-5/8" ID with 3/4" walls (x2), should = 3.125" total diameter. Nope, the walls are almost an inch thick. Total diameter is just under 3-1/2".
So now I'm back to square one and $13.01 shorter in the wallet.

I have scoured the internet looking for something that is 3.125" ID to no avail. :banghead:

@ Dewphy What is the ID of the pipe you are using, brand, and cost(if you don't mind me asking)?

@ lfhoward the melting temp is not an issue as the tube does not contact anything that hot. I've been using a flexible RV sewer hose for 6 years with no issues at all.

Just take a Dremel to it in the inside until it's 3 1/8" OD.

John3:17 · **Posted:** Tue Sep 16, 2014 10:15 pm

NAMoulton1 wrote:

Just take a Dremel to it in the inside until it's 3 1/8" OD.

O.D. = Outside diameter

Scar0 · **Posted:** Wed Sep 17, 2014 3:50 am

John3:17 wrote:

NAMoulton1 wrote:

Just take a Dremel to it in the inside until it's 3 1/8" OD.

O.D. = Outside diameter

Plus, I couldn't if I wanted to. It is soft foam rubber and would no longer be smooth for a mold.

huntb · **Posted:** Wed Sep 17, 2014 10:04 am

Scar0 wrote:

It came in the AM, Installed in the PM.
Here are a couple of side by side Pics. 3.7 on right.

Now you guys said you have to install it upside down for it to fit.
But the only thing keeping it from installing right-side up, is the 2 alignment pins on the intake manifold. (If you install it upside-down the alignment pins are outside the TB mounting surface.) So what I did was to simply ream the holes on the 4.7 TB to match up with the pins on the intake. I did not want to Mod my intake by removing the pins...
In the following Pic, at the tip of the red lines, you can see the original alignment pin holes on the 4.7 TB.
The yellow line tips are where I had to ream them out, to get it to work on my 3.7 intake. The bolt holes line up perfectly and the gasket still seals it.

Here is a Pic of it installed.

It fits right where the original TB was located, I was a little concerned because it is a little larger on the bottom, but there was enough room to fit just like it was made for it.
Couple more Pics of the install.
Right side.

Left side.

Now comes the issue of the air tube.
My DIY CIA uses a 3" smooth bore RV sewer pipe for the connection to the TB. But 3" ID needs to go to a 3.125" OD TB.
I was hoping to be able to heat up the sewer pipe and stretch it over the new TB... But it did not work. So tomorrow I will need to get a new intake tube to go from the air box to the TB. For now I used the same coupler I was using on my OEM TB which makes the inside diam 2.75"(approx). Kinda defeats the purpose of the new TB, but at least I can drive it.

The other thing I thought of, that was not previously mentioned, was the intake manifold opening. What good does a larger TB do if the intake hole is the same size as the original TB? To my surprise the intake manifold opening is actually larger then the original TB opening, and just a hair smaller then the new one.
Now I have the little bugger installed and hoping the rig will run.
WOW fired right up on the first try! YEA!
I was warned by Gageraid the RPMs seem to hang a little longer, which they did. Each time I reved the engine the RPMs would hang there, rev a little more and the RPMs go up again and stay there... I'm thinking DANG IT! It's not going to work!!!
Finally at 4000 RPM it broke, and dropped to a 1000 RPM idle. A few more revs and it dropped to a 700 RPM idle with very little hanging at the top RPM. I think the rig was just getting a feel for it. Anyway, it is acting almost like normal again. Tomorrow comes the road test.
After I get a new air tube, I will post back with more Pics.

The RPMs are hanging because your computer hasn't compensated for the greater amount of airflow. Hanging idle is a classic symptom of a lean running vehicle. Also, the same reason that people are seeing better MPGs from it. Less fuel per combustion cycle = better economy = worse performance. The reason everyone sees better throttle response is because of the larger butterfly. Larger butterflies will make it seem like you are pressing down on the gas petal further which gives you the feeling of better throttle response.

The only thing the larger TB helps is when you are at WOT. After my computer relearned for the larger TB, my mileage went back to suck city again

Increase in mpg w/ 4.7L TB

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