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Discussion Starter · #1 · (Edited)
After mounting a remote reading thermometer in the stock intake tube of my home made CAI, I discovered there was a significant temperature difference between ambient air and actual intake air temperatures. I went through about 3 different versions of this insulation mod., until I arrived at the current setup. My true intake air temp. now runs at ambient on the highway and 0-8 degrees above ambient around town. Sometimes there will be a little higher difference (depending on how much stop and go), but it usually recovers within about a mile or so. This difference also may increase during summer months, but I'll have to wait to see.
I started Phase 2 by insulating the bottom part of the airbox with foam backed aluminum duct insulation, and building my own air intake tube. Parts for the intake tube were acquired from www.airflow.com. The ABS and duct insulation from Home Depot. The first intake tube was a 4 inch aluminum tube with 1/2 inch of foam backed aluminum insulation around it. A 5 inch aluminum tube was slid over top of it making it a double wall tube. The current setup replaced the 4 in. inner aluminum tube with a 4 inch ID cellular insulated (1/4 inch wall thickness that looks like encased concrete mortar) ABS black pipe that goes from the box to the bend going into the throttle body. (This is where I have my temp. gauge sensor located.) The ABS is wrapped with a layer of two rows of plastic bubble wrap encased on both sides with aluminum foil. This was cut from a front windshield slip-in sun protection visor bought from a local auto parts store. Why bubble wrap?? I researched it on the internet and found it is only surpassed by argon gas as an insulator of heat. The study I used lists insulators in this order of effectiveness: argon, air (bubble wrap), styrofoam, polystyrene (solid), wood, teflon, water, glass, and concrete. I looked at a few other studies which also listed bubble wrap as among the most effective. Any way, then I have the 5 inch aluminum outer tube. As an experiment I have also insulated the elbow where it goes into the throttle body. I have to find a way to sanitize the elbow mod. though. My intake air temp. when cold, in town now runs from minus one degree (might be due to the calibrations of the two units) to plus two degrees of ambient. Around town stop and go after warm up runs 0-8 degrees from ambient with long stops in traffic at the higher end. Within a mile it will cool down to 4-8 degrees of ambient. On the interstate from about 50 mph up it runs at ambient after about 3 miles at speed. After a 15 plus minute stop, start driving at 35-40 mph and cool down from around 100 degrees to coolest takes about 3 miles with the biggest drop (30-40 degrees) taking place within the first mile or so. These tests were done with ambient running between 50-65 degrees. I imagine in warmer temps. the variance from ambient may increase, but I am fairly confident that at highway speeds true intake air temp. will run at or within a couple degrees of ambient. The biggest problem in my opinion is controlling heat soak, as indicated by sub-ambient to near ambient when the engine is cold. I feel the majority of this problem comes from the intake tube. I did not notice much difference after insulating the air box. Is all this worth it? Aside from my love of tinkering, I'd say, yes! I am at about $120 for all mods. and my gas mileage for the last three tanks (205 hrs/5200) miles currently) has been 18.2, 17.9 and 18.4 mpg respectively with about 95% of driving in town and an occasionaly WOT blast. My highway mileage runs 27.5-28.3 mpg at 60-70 mph. Others have documented dyno tests for the air box mod. vs. stock, so I am sure there is also a small increase in power. I have since added more insulation to the top of the airbox and around the main part of the tube. I don't think this is doing much though, but I figure it can't hurt. The only other things I have done are raised tire pressure to 40 PSI, run nothing but regular 87 octane fuel, Mobil 1 synthetic oil and my MDS "on" indicator light.
http://www.300cforums.com/forums/showthread.php?t=4984
As far as the intake mods. go I am satisfied that I am getting more than enough (Two 3 inch ducts into the air box) cool (insulated air box and intake tube) air into the engine. The original mod. cost $10. The latest mods. cost about $110. Still way cheaper than the aftermarket ones and I know the engine is now ingesting the coolest air possible.
 

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Magnuman

Genuine thanks for your full description and supplying us the reasoning behind what you have done

I hope you don’t mind, because your description is fairly technical and packed with information: to make sure I and others have fully understood, I will give a brief synopsis. The point of this is to refine our understanding. If you wish to: please add to this synopsis.


• The written analysis of the air intake by David Vizard that Chrysler’s engineers, having already put significant effort into computer modelling of all elements of the air intake system from filter to plenum; for a wide power band, consistent with street performance needs, influenced you to retain the inherent high value of this part of the air intake system
• You examined the intake silencer and found it to have no air restriction - just kept the system quiet - so decided to retain it.
• Having seen improved dyno figures- (at least at WOT max power) by feeding extra cold air to the intake you wished to use this to increase volumetric efficiency primarily for improved gas mileage and performance
• You reasoned that an additional and straight cold air feed taken from behind the grille area was one way to achieve this by adding cold air and potential ram-effect efficiency at higher vehicle speeds
• An effective and inexpensive air feed pipe was installed and fabricated to feed ambient (cold) air from the grille area
• Your measurements of intake air temperature showed improvements in the “cold air” aspect could be made by insulating most of the system.. As most efficient insulation, you chose foil-faced reflective insulation availabe from most large home improvement stores. - brand names: Astrofoil, rFoil, Reflectix, Tempshield (Class 1/Class A fire rated)
• You examined the system to see which items would best benefit from insulation keeping the air as cold as possible and proceeded from there.
• You obtained a measurable benefit in gas mileage and a small (non-measured in your case but measured in others with same/similar mods) power increase

Thanks for taking the time, for the benefit of the forum members

Zilla
 

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So should i stop my CAI mod or keep going all this "techy geek" is making my head hurt. I got the thing torn out got a plastic coragated tube and ready to go but should i stop.
 

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Discussion Starter · #6 · (Edited)
Zilla,
By Jobe, I think you've got it!! I'll elaborate a little on some items of your synopsis.
1. I figured if DCX did a lot of computer engineering to design the intake system, they must have at least come close. That's why I didn't mess with the plenum length. I examined the airbox, noting the directional fins inside the top. The only thing I did to the top is chamfer the edges of the outlet to the plenum to make for slightly smoother airflow out of the box. I used K & N's formula to determine the filter area is more than adequate for the engine size and RPM we will be operating at. A large area cone type filter would just be overkill, based on K & N's formula.
2. In my opinion, it is a waste of time to remove the stock silencer (so-called ear drum). I had thought of removing it and running another 3 in. duct over to the grill or fog light area. I think any increase over stock would be minimal, and probably not worth the effort.
3.Improving the intake (and exhaust) systems generally improves the overall volumetric efficiency of an engine, although DCX has really done a pretty good job in the stock form. Normal, stock street cars have a volumetric efficency in the neighborhood of 70-75%. An improved (more air volume in and less restriction out) intake and exhaust will add maybe 5-10% with our LX's probably on the lower end of that scale.
4. My philosophy was to make more air available and let the engine use it if it needs it. The shorter tube to the airbox probably provides more air than the stock air intake, because it is the path of least resistance for drawing intake air. Most importantly, COLDER IS BETTER.
5. Air feed tube and end adapters/couplings were obtained from Home Depot.
6. Forum member "done" was kind enough to do air temp. tests of the stock intake system. As I said earlier, DCX really did a pretty good job. You can see his tests at:
http://www.watsoncard.com/magnum/ They are after the pictures of his car. Generally speaking my mod. provides more air (potential) and saves 8-10 degrees on the highway, and substantially more around town...also with much quicker recoveries. My old "Holley Carburetor Bible" says there is about a 1% increase in power for every 11 degree reduction in air temperature. That's a pretty good boost for cheap $$.
7.I used the foil faced foam rubber self stick insulation (2 layers) on the airbox and front of the radiator tank only. The insulation around the 4 and 5 inch tubes, and over the top of the airbox is 2 row bubble pack faced on both sides with aluminum. It is cut from a windshield sun visor obtained from the local auto parts store. I feel this is a must. I tried the self stick stuff first and it is not near as good.
8. The airbox is insulated on all sides and the bottom. The front of the radiator tank to the water level is insulated. The inner ABS tube 1/4 inch cellular wall serves as an insulator. It is surrounded by a layer of the bubble pack sun visor material. Tube length goes right to the bend into the throttle body, but does not obstruct airflow in the bend. I feel the smooth inner wall of this tube reduces airflow resistance and turbulence as compared to the stock thin accordian wall tube, and hopefully moves the air faster as a result. My remote temp. sensor is mounted right at the curve at the end of the ABS tube. The 5 inch tube slides over the top of the insulation and butts up to the reducing adapter at the airbox and slips into the 5 inch to 3 1/2 inch
reducing elbow that mates to the throttle body. There is another layer of bubble pack insulation wrapped around and velcroed to the 5 inch tube. A bubble pack cover fits snuggly over the top of the airbox. These last two were after thoughts and may not do much, but I have not tested it without them...too lazy. Maybe some day.
9. Can't be positive about power increase, but I am certain about mileage increase. My personal belief is that there is some power gain though. I think the additional power and increased mileage go hand in hand.

Hope this helps.
 

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Discussion Starter · #7 ·
Scarbrs,
By all means keep on going. After both mods. it should look something like these pictures.
 

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Scarbrs said:
So should i stop my CAI mod or keep going all this "techy geek" is making my head hurt. I got the thing torn out got a plastic coragated tube and ready to go but should i stop.
Eric

I'm slightly confused by above ......... hope this is to the point

If you are fitting a tube that's corrugated and ribbed on the inside, turbulence is created and air flow velocity is reduced, compromising throttle response and upper end HP. Smooth interior of tubes/curves is neededIf your discarding internally ribbed piece Bravo!


Zilla
 

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Ok

So i should keep doing it just change my intake tube to the aluminum? The tube i have is a coil spring type with a plastic covering.I was going to hook it up to the bottom of the air box and they point it behind the foglight grills which i have already have replaced with mesh.
 

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Discussion Starter · #10 · (Edited)
Scarbrs,
Yes! As Zilla said, that wire type ducting is real coarse down the inside and will cause lots of restriction and turbulence. Go down to your local home improvement place and find the 3 inch stuff that looks like the picture below. Then look down it, and you'll see it is a lot cleaner...but maybe not quite as easy to route. The fittings I used (see pictures) will also work great if you're going to replace the stock "ear drum" with this tube. You'll need to put some self stick weather strip around it where it slips up into the airbox, and you'll also have to figure out some sort of mount bracket to hold it in place. The current "ear drum" is held in place by one small bolt, and a rubber locator nubb. You'll probably also have to go to the auto parts store (Napa has these) and buy some replacement plastic fasteners to replace the non-reuseable ones that hold the inner fenderwell in place. Just take an old one down and they should be able to match it with a reuseable type. I suppose you could also just leave the "ear drum" in place and stuff the new duct (surrounded with rubber weatherstrip to hold it in place) into the "ear drum" intake, and let it go at that. Good luck,and keep us posted.
 

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To late

I did the plastic lined tube. It goes in to the air box then the filter won't it lose any tubulance there? I realy don't want to take it apart again it was a pain to get my arms under there. I wire tired it to a couple of hole in the bumper and then around the tubing. I then wired it to the mesh.It works good but was hard to do. I then stuffed it up in to the hole in the air box and then used that tape to hold it in, was a tight fit so the tub shouldnt come out.
But it it does have trubulance isnt that good like those stupid tronado things?
 

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After reading this and exchanging a lot of messages I made a half assed attempt at doing the same thing, but kind of lazier, lol. I don't have a temp sensor to report temp results but it seems I may have picked up between 2 and 3 mpg overall. I used a layer of foam pipe insulation and a layer of fiberglass exhaust heat wrap over the foam insulation around the stock intake tube. I cut the ear drum off leaving just a stub which I pipe clamped a 4 inch home dryer flexible duct line too. I pulled out the black plastic trim block off thing behind the vent in the bumper beside the fog light and zip tied in an 90 degree outdoor dryer vent for a house and pipe clamped the other end of the flex line too it. It is jammed in so tight that the stub from the ear drum can't fall out of place. It's turned so the bend faces forward and the flex line arcs off of that down to my 90 degree vent which acts like an air scoop behind the bumper. Since there is no other inlet, and it's a sealed system, my hope is that I'm getting some ram air effect all the way through and maybe that will help overcome any restriction in the stock system.

It's hard to tell from the angle of the photo but the top of the dryer vent/scoop is nearly vertical and the flex line has a pretty good arc too it.

Tire Motor vehicle Automotive tire Hood Tread

Hood Automotive design Automotive exterior Bag Bumper

Automotive tire Grille Motor vehicle Automotive exterior Automotive lighting
 
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