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Discussion Starter · #1 ·
I finally got around to installing my A pillar gauge pod that will accommodate two gauges. I decided to put in two vacuum gauges and check air flow in and around the manifold to the bottom and top of the stock R/T air box.

I have a K&N filter and a 2011 Charger intake tube that moves the air right from the air box to the throttle body without that ridiculous silencer otherwise this system is stock and obviously naturally aspirated. It does have a 91 Predator tune with throttle modification, but that doesn't really affect this test.

One vacuum gauge was hooked to the vacuum port right after the throttle body and generally can be considered manifold vacuum. This is handy because you can see if you are starved for air and get a general idea of how far the throttle body is open.

The other gauge I fed first under the K&N then on top of the K&N. If there is a significant difference between any of these numbers air is not flowing well.

Not to patronize anyone, but all air is pushed through the system by atmospheric pressure which at sea level is 14.7 lb/sq inch.

I got some fascinating results.

At WOT the manifold vacuum reads a steady 5 inches of mercury which is great because it indicates plenty of air is available.

Either placement of the other gauge gave an interesting result. Essentially
to the resolution of the Autometer gauge. there was no movement. This indicated that the air supply at the front of the throttle body was essentially at atmospheric pressure. I even changed the gauges to see if I had a vacuum leak and I didn't.

I ran the test with my six speed shifting at 5500 rpm through 5 gears and had to shut down. Everything was consistent.

What does this mean? It means that your stock air box with a newer clean air tube + K&N filter can supply all the air a basically stock 5.7 can use.

The air is cooler too because none of it flows from the engine compartment. Consider too, there is a very short wide path for the air without many bends. This verifies the anecdotal results from the track forum too.

The typical CAI may look and sound neat, but it is certainly not helping performance. If you get in cool air then it may help depending on how many bends and the diameter of the tube.

So, I see only one modification that should help a bit and that is spend your cash on an 85mm throttle body set the Predator for a CAI tune and forget that $300 CAI.

Do get the 2011 clean flow Charger tube from your dealer. It is a direct path for the air without kluges to create turbulence.

I was quite frankly amazed at how efficient this system is. Again, this was done on my 5.7 and I don't make claims for the 6.1 or 6.4.
 

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Great write up! Having taken my air box apart a few times I am not surprised by your results. The opening at the bottom of the air box appears to have more sq.in. of opening than the larger end of the Charger intake tube. With that said, and NO air filter the engine should not require more air than the box can supply. Now your only variable is the filter itself. So, assuming a good filter is installed there should be no need for an aftermarked CAI - from a performance standpoint.
 

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Discussion Starter · #3 ·
Great write up! Having taken my air box apart a few times I am not surprised by your results. The opening at the bottom of the air box appears to have more sq.in. of opening than the larger end of the Charger intake tube. With that said, and NO air filter the engine should not require more air than the box can supply. Now your only variable is the filter itself. So, assuming a good filter is installed there should be no need for an aftermarked CAI - from a performance standpoint.
I agree completely and this test said as much. If I was still running at the track, I would likely just replace the filter with SS window screen based on what I just found out.
 

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Great write up of test. Recently swapped to '11 Charger air tube. Just need to get K&N filter now.

Thanks for sharing! :bigthumb:
 

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Great write up of test. Recently swapped to '11 Charger air tube. Just need to get K&N filter now.

Thanks for sharing! :bigthumb:
LOL, me to. About 3.5 hours ago to be precise :browsmiley:
 

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Gm LS throttle bottles come equipped with a screen covering the TB.even my SC 3.8l Buick had the screen. I'm sure a few tried running no air filter and depended on the screen for filtering, I'm not so sure this is a good idea. Most removed the screens and left whatever filter they had in place.It was said the screen reduced turbulance entering the TB, believed by most but obviously an old wives tale as our hemi's run just fine without them. Unless the difference between MAS systems and MAF systems created such anomalies.All this thinking is making my brain hurt. Discuss among yourselves...
 

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As for having 5" vacuum in the manifold, this might be due to the TB never goes beyond 76 percent open. I do alot of data logging. It shows pedal at 100 percent, it also shows TB-Blade at 76 percent. I dont know why the TB is limited. I want to hook up a switch that would close if the TB was past 90 percent.

I will ask the tunners if they ever looked at the TB when dyno-tunning.:indifferent:
 

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I wonder though if the throttle blade is really only 76% open, or if it is really open all the way and the computer reports that it is only 76% open. Stranger things have happened.

One would have to remove the intake tube and look to find out.


As for having 5" vacuum in the manifold, this might be due to the TB never goes beyond 76 percent open. I do alot of data logging. It shows pedal at 100 percent, it also shows TB-Blade at 76 percent. I dont know why the TB is limited. I want to hook up a switch that would close if the TB was past 90 percent.

I will ask the tunners if they ever looked at the TB when dyno-tunning.:indifferent:
 

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I like the idea of a 11 charger intake and if you people don't mind would you have a part number of it and did it go in without any trouble.(same as stock fit).
Good write up
Thanks
Dan
 

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Great write up Matrix. I've been going back and forth on whether to do a CAI or just a K&N filter. You have convinced me that the filter is all that is necessary and the CAI is just for looks.
 

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Discussion Starter · #11 ·
I wonder though if the throttle blade is really only 76% open, or if it is really open all the way and the computer reports that it is only 76% open. Stranger things have happened.

One would have to remove the intake tube and look to find out.
That has been done a while ago and there is a thread that had a lot of data logging and comparing timing retard in 6 speed and autos during shifting.
One member (I don't remember who) did video the throttle body, and the blade without question goes to full open and now with the new predator tune you have some control on how fast this happens and also tied into how much foot movement it takes. The videos links were posted for all to see. There is no mystery on this point. I think the thread was originally in the General Forum then moved to Performance tuning.

I was able to find the video link:


From the long data logging thread:

http://www.challengertalk.com/forums/f181/if-youre-datalogging-6-speed-46638/


It is interesting reading and you can learn quite a bit, but you need to be interested. There is no debate, the throttle bodies open full.
 

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Discussion Starter · #12 ·
I like the idea of a 11 charger intake and if you people don't mind would you have a part number of it and did it go in without any trouble.(same as stock fit).
Good write up
Thanks
Dan
Dan here is the part # Mopar part #4861940AC
 

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Thanks for the great write-up. This helps a lot. I had a ATF stage 2 CAI. Took it off and modified my old intake by cutting off the silencer and sealed the opening. Installed a K&N filter and am very pleased with it. The only difference is less noise.
 
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