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My 6.4 True CAI Custom Build

23K views 40 replies 12 participants last post by  Grand_hustle17 
#1 · (Edited)
I purchased my 2017 Scat Pack Charger in March and after much research and reading I quickly learned that most intakes result in little to no gain on the Scat Pack, SRT, or HC cars. Well...after a few months I went ahead anyway and splurged on an Airaid Cold Air "Dam" kit (part #350-210). I drove with this for a couple weeks to test it out and first impressions were exactly in-line with what I read on the forums; loud engine roar, better looking engine bay, slightly better MPG, but a negative impact to intake temps. The best I saw was about 6-7 degrees above ambient during normal driving but HOLY CRAP did the intake get heatsoaked easily while momentarily stopped, especially since temps around here lately are 90s and into the 100s on some days. The only way to cool down the IATs after they rocketed upwards was getting on the throttle heavy or doing a WOT pull, otherwise the temps stayed up 10-15 degrees over ambient - again, this is not surprising because many others have already posted about this. I removed the intake and sold it to a fellow 5.7 owner because it just wasn't worth having IMO.

Then I got bored and started thinking about what else. Of course I'd heard about the LMI Carbon Fiber kit and definitely loved the idea of it, but I just didn't want to drop upwards of $400 for negligible gains on my application. My car is street driven and mildly modded so although the LMI is the best option it wouldn't have done a whole lot for me. In wanting to do something different, I thought "why not just make my own kit". I had done this before many, many years ago and it worked out so I thought I'd give it another go. I ordered up a bunch of parts and yesterday finally got a buddy, @Griffin R/T to give me a hand on the build - Much Thanks again BTW. Essentially the setup I built is quite the same as the LMI True setup except the tubing components/material is obviously different. The Airaid universal tube kit comes with near perfect sections (a 30* and 45* bend) so a little measuring, cutting, and trimming was all it took. For about just about $200 all-in I am pretty satisfied. First impressions on this setup are great! The engine bay looks SO much better, the intake roar is apparent but not overbearing, and the IATs are within 1-2 degrees of ambient.

Parts List:
  • Airaid Universal 4" Tube kit
  • S&B 7" Intake Filter
  • IAT Extension Harness
  • 4" to 3.5" Silicone Coupler
  • 4" 90 degree Silicone Coupler
  • 18mm Breather Filter



THE BUILD:











I still have a little adjusting to do with the brake duct as I want to reinstall a modified section of it as some LMI owners have done. I am considering what it would take to sand the tube and possible paint it white to give the engine some more flare so I will repost if I decide to do that.
 
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#2 ·
Nice, I'm honestly surprised nobody has done this yet. I used that air raid kit to make an intake for my ram and it worked quite well imo. If I didn't get the lmi for a steal I think I would've went the same route. Good job!! Did you still have to trim that triangle for the 4" pipe??

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#3 ·
Nice, I'm honestly surprised nobody has done this yet. I used that air raid kit to make an intake for my ram and it worked quite well imo. If I didn't get the lmi for a steal I think I would've went the same route. Good job!! Did you still have to trim that triangle for the 4" pipe??

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Yeah I had to trim it out the same. I used some heavy duty moulding trim to surround the hole and it turned out really good.
 
#6 ·
Just did mine today. Very simple and quick to complete aside from cutting the hole (my dremel bit broke and I had to hand hack the hole...). Thanks a lot to @MY357 for providing detailed answers to my questions. During my testing I saw an average of 3-5 above ambient temperatures. This is absolutely a better option than the LMI option.
 
#8 ·
Cheaper , not better. Carbon fiber wins in heat dissapation every time. I'm 1-2 ° over ambient. Also doesn't heat soak as quickly as the air raid plastic. Not knocking it , for a budget intake it's perfect.

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#9 ·
Cost is pretty cheap for this kit Beach, I think I paid about 100$ for my old one.

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#12 ·
Was it this kit for 100? I don't see this 4" master build kit for less then 300, for that price for a short stretch you can get a leg maker

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If you buy all of the required pieces for this kit it's about $180-$190 plus your elbow grease. I couldn't justify more than double the price for LMI just to have the CF tubes. I have not done a scientific test but I'd argue all day long that you get nearly identical performance from both. They are exactly the same diameter, bends, and filter with the only difference being tube material. My IATs are the same as those with LMI. If people have the money to spend, then by all means go ahead and get the LMI if you wish. I just wanted to give people an option that wasn't $400 for marginal performance.
 
#17 · (Edited)
Good job; however an important, make that critical, piece is conditioning / smoothing air entry into the intake tube itself. I won't get into the fluid dynamics that occur right at point-of-entry and how the higher the air velocity the more the entry turbulence literally impinges (blocks) air from entering (I've posted on this a few times over the years), suffice to say it is extremely important.

All your efforts to gather cooler air is great but resistance to airflow increases at the entry point as rpm rises because of the squared off shape. Spectre produces a composite velocity stack that has flanges on both ends that allow attachment to a 4" tube (entry side) and transitions up to 7" on the air filter side. The pic shows one temporarily attached to a throttle body to measure actual CFM (along with machined TB testing to confirm their uselessness). To put this into perspective; without the air smoothing , at 39in mercury the CFM dropped to almost half;



There is a How-To thread I posted some years back showing this stack mounted, along with the rest of the custom intake tract and isolation panels in the front / left fender cavity to ensure only ambient air is being drawn into that 10 cubic litre cavity.
 
#19 · (Edited)
Are you saying the entry point at the filter needs a smooth transition or at the throttle body?

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In the OP's case, at the filter. FWIW, any perturbations along the entire intake tract create turbulence. Laminar is good - turbulence is bad. This includes every single step-up or step-down, bend (hence why the Apache SRV manifold has an angled entry) and increase or decrease in cross sectional area.

To put the above pic into perspective; for testing actual cfm on a flow bench - that intake bell you see is essential to achieve accurate results. When ports for example are bench flowed the tech will use modeling clay to form a smoothed entry (like the above velocity stack) on the surface next to the port to smooth and align the air prior to port entry. Otherwise any gathered data is useless cause normally there would be an intake manifold attached during use that is supplying aligned (and fairly smooth) air flow. Its why the nacelles on jet engines are rounded and shaped specifically so that air entry remains laminar over a wide range of velocities as well as angles of attack (AoA).
 
#21 · (Edited)

Four inches is adequate; without getting deep into drag types (viscous for starters) one needs to understand that within the intact tract, air at the inner surface of the tube is travelling at zero M / s (0 mph). This may be hard to understand; air right at the surface on any jet's outer surfaces is at zero velocity no matter how fast it is moving. As velocity measurements are observed further away from the tube's inner wall, velocity increases exponentially. It doesn't take a rocket scientist to realize that a tube that is the same diameter as the throttle body (TB), in this case 90mm (3.54in), viscous drag is reducing, along with turbulence from other irregularities, the overall rate-of-flow (RTF) to something less than that actual 90mm inside diameter (ID).

As tube ID increases, gains to compensate for viscous drag diminish as the overall limit will be the 90mm entry right at the TB's butterfly itself. So the idea is to reduce upstream losses by making the tract smooth and of a larger diameter than the smallest aperture. Not shiny smooth, but as free of as many anomalies as possible that create turbulence (for example, ensuring two tubes joined together by a sleeve / clamps have the ends of the tubes match and are butted up against each other). As previously mentioned some of those anomalies include bends (because air has mass, once in motion with a vector it wants to stay on that vector), narrowing and widening (this increases and decreases velocity proportionally, but with a slight delay due to that mass (that in of itself creates significant turbulence), sharp steps either up or down (same deal - an abrupt change in localized pressure / vector that creates turbulence proportional to the change in cross sectional area).

One can't do much about viscous drag except reducing the overall length as much as practical. Hence how a larger ID, to a point, allows for less aggregate drag forces to hinder air flow as it travels at and near the center of the tube.

EDIT; the same issues occur within the exhaust system with one added dimension to make it more dynamic, heat. This is why an exhaust system can have a 3" ID at the exhaust manifold and a 2" (or less) exit at the exhaust tips with absolutely zero change in aggregate drag forces (hint; amongst some other stuff, as the exhaust gases cool they contract significantly).
 
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#23 ·
Boundary layer

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Yes; I assumed most readers would not understand the term as it relates to air near / at the surface...
 
#24 · (Edited)
Going to bump this up as I recently swapped out my manifolds. On my 6.4 I ran an lmi for the entire span. Now I swapped to a 6.1 manifold.... ok , so obviously needed a new cai or intake , what have you. The air raid system fits the bill , and quite well I might add!! Iat's are right on par with the lmi , I believe the delivery and flow may actually be better with this system!!! [emoji15] So , here it is. I made sure each and every connection butts up smoothly to the next. From the filter all the way to the throttle body. I did use a die grinder and smooth the transition from the velocity stack to the air raid tube as they are both 4" tube , but the air raid is a thicker material. The only other thing I have left to do is wrap all the tubes in a heat shield tape of sorts. Here it is :
velocity stack at the filter(4"-6")
filter is 6" opening and 8.5" cone
ditched the fog lights
just ordered the hellcat vents to cover the hole and voila !! Imo a very efficient "TRUE" CAI , all for about 200$. And here's the money shot :)


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#25 ·
Good one Ronan!

Using the fog light opening on the front is good idea to just feed outside air into the cavity.
 
#27 ·
Bump... any pics of where you guys put the IAT sensor???

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This is where mine is , but you can buy an ext cable for it and run it closer to the filter like the lmi if you like. I knew I'd be redoing all of this when I start building the turbo kit , so I didn't bother buying the extension. It may read a little warmer where I have it , but it's still reads ~3 above ambient when moving.


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#31 ·
Would love to see the details there

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Pic of the grommet. The sensor just slips/turns into it.


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#33 ·
Props for DIY.

I like the idea of running the tube thru the triangle. However no way im gonna grind my car to make the tube fit thru there. It’s just not an option no matter what.

There’s the option of doing a reduction to 3.5 inch right before the triangle opening. Then you gotta figure out what you want to do from there like running a velocity stack. Lots of details to sort out for sure.

I have one figured out for my Hellcat using a 5 inch inlet filter. Maybe I’ll fab it up next month if I have time.
 
#34 ·
Props for DIY.

I like the idea of running the tube thru the triangle. However no way im gonna grind my car to make the tube fit thru there. It's just not an option no matter what.

There's the option of doing a reduction to 3.5 inch right before the triangle opening. Then you gotta figure out what you want to do from there like running a velocity stack. Lots of details to sort out for sure.

I have one figured out for my Hellcat using a 5 inch inlet filter. Maybe I'll fab it up next month if I have time.
Airaid also makes a 3.5" kit you can use for the whole path. I used 4" simply because I already had the lmi before I swapped manifolds. Personally, I have no issue cutting that piece, but I get it , many won't want to cut up there car. I also smashed in my tub behind my fenders liners in the rear to fit the 315/50/17's :) that's just me.

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#37 · (Edited)
Ronan the thermistor bead on the IAT sensor is not affected by surrounding structure. This was proven by many in the early days where the notion (a carryover from MAF vehicles) moving temperature sensors outside the actual true temperature zone that is really required, especially on Speed Density Systems, to ensure an accurate calculation between the 5+ PIDs involved. Also note that A / F and timing do not respond instantly to a change in IAT. Given this, plus the fact that the thermistor bead's volume is so small it responds to deltas within millisecond, in our applications moving the sensor is moot.
 
#38 ·
Ronan the thermistor bead on the IAT sensor is not affected by surrounding structure. Tis was proven by many in the early days where the notion moving temperature sensors outside the actual true temperature zone that is really required, especially on Speed Density Systems, to ensure an accurate calculation between the 5+ PIDs involved. Also note that A / F and timing do not respond instantly to a change in IAT. Given this, plus the fact that the thermistor bead's volume is so small it responds to deltas within millisecond, in our applications moving the sensor is moot.
I guess that does make sense. Once I'm into the throttle the temps drop very quickly. It just seems to heat soak a bit more with this manifold. Although it could also be the difference between the carbon fiber lmi and the plastic air raid as well. Going from a plastic manifold with carbon fiber intake , to an aluminum manifold with plastic intake could mean a bit more heat soak. I was going to buy an extension and redo it when I run the nitrous , but if it is moot I will not waste any time or money. Valuable information Simon, thank you.

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#39 ·
That looks good. Glad u r happy with ur build.
 
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