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Which is more important, air flow or intake air temperature?

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Discussion Starter · #1 ·
Hey guys,

Does anyone know which metric (air flow or intake air temperature) is more valuable in regards to creating power with an aftermarket intake? For this example, let's look at the OEM intake vs the Forge intake. The OEM intake is about 3" in diameter before tapering down to the turbo tube. The Forge is 4" in diameter and, when combined with the turbo tube, tapers down far less than the OEM intake. One must assume that the CFM is greater in the Forge unit. In regards to air temperature, the OEM intake is closed and the Forge is open. One must assume that the IAT of the Forge filter is either greater than or equal to the IAT of the OEM intake. Which metric makes a bigger difference on engine power and why?
 

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I dont know any compassion IATs but i have a forge and recently got a JB4. I also have an intercooler and downpipe and all that taken into consideration, my IATs are about 130°F usually.
I have this feeling that the takeda momentum is the best intake available rn so im currently trying to get my hands on one and will compare IATs to see if it makes a difference at all.
 

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Discussion Starter · #3 ·
At this point, the largest intake tube seems to be the Forge unit, especially when paired with the turbo tube. Do you have any idea what diameter piping is used on the Takeda? I could not find any specs on that unit or any others for that matter. Forge seemed to be the only company that revealed how large the intake tube was. If the Takeda intake tube is the same size as the OEM unit, then I do not see how it could be any better than the OEM unit because they are so similar in size and both utilize a closed box.
 

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The size of the tube doesnt really dictate how good or bad an intake is though. I believe the takeda is about 3.5 inches im not exactly sure. The forge is for sure the biggest right now but it doesnt really matter all that much because its bottle necked by the 2 inch turbo tube. The forge turbo tube is 3 inches so regardless of how big your intake tube is, it all ends up 3 inchs best case scenario before the turbo. The takeda (and pretty much every other intake) has better airflow because of a high flow filter element.
Regardless of what intake you pick it will give you gains, but none to write home about. They all claim more or less 12hp. It basically depends on which one you think looks cooler and sounds better
 

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The Tekada starts at a 4" diameter at the filter and then tapers down to 3". A closed box is better for temps. This is the best compromise for both temp. and flow, especially with the Forge turbo inlet. I have that exact set-up. In the city traffic my IAT's never get over 110 degrees (f). On the highway the IAT's are about 5 to 10 degrees above ambient temps. I do have a Wagner inter-cooler on it too though. I think you'll love the Tekada Momentum intake. Hope this helped you?

Best regards,

-Mike
 

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Discussion Starter · #6 ·
So, assuming that all intakes are bottle-necked by the diameter of the turbo inlet, would there be an advantage to having larger diameter tubing leading up to the inlet? For instance, wouldn’t an intake that tapers from 4” to 2” create more pressure at the turbo inlet than an intake that tapers from 3” to 2”?
 

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Its a bit of a trade off. The 4-2 might create more pressure but its a mess to drive. The car hated itself at low speeds and especially when it was cold. Might have lost a hair in my 0-60 with the 3" inlet but it made the driving experience alot better and smoother. It depends if youre looking for power at any expense or the best possible driving experience. Or something in-between. Theres many options for many different driving styles after all

Nothing we say has been proven either were just assuming alot because the odds of someone being able to compare all of these things under the proper circumstances is pretty much non existent.
That's why picking something as simple as an induction kit is annoying. No matter which one you get you'll be happy but none are going to blow you away or anything
 

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*****cough+++++ Tekada Momentum ++++cough++++++

Then get a Velossa Tech intake snorkel and the smile will NOT leave your face..... :)

Best regards,

-Mike
 

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Both intake temps and air flow are equally as important so it's hard for me to vote on it.

The Velossa Tech intake snorkel creates less waste gate duty cycles so this means that the turbo is running much more efficient. That coupled with the Tekada Momentum intake and in my opinion you have the best intake on the market thus far. And for even better performance get the Yames turbo inlet or the Forge one. I have the forge one attached to the Tekada Momentum and that is attached to a Velossa Tech intake snorkel. Best set-up I have tried so far and plan on keeping it. Hope this helps?

Best regards,

-Mike
 

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Both intake temps and air flow are equally as important so it's hard for me to vote on it.

The Velossa Tech intake snorkel creates less waste gate duty cycles so this means that the turbo is running much more efficient. That coupled with the Tekada Momentum intake and in my opinion you have the best intake on the market thus far. And for even better performance get the Yames turbo inlet or the Forge one. I have the forge one attached to the Tekada Momentum and that is attached to a Velossa Tech intake snorkel. Best set-up I have tried so far and plan on keeping it. Hope this helps?

Best regards,

-Mike
Thanks for the shout out Mike, appreciate it. Mike & Mike305 said it best, it is an upgrade that will keep you smiling and appreciate the car even more. I would group intakes in the category of rims, they all have similar characteristics, but in the end, pick the one that suits your taste. As for the turbo inlet section, I be more than happy to help you out if you end up with the Tekada (or AEM, Injen, Tork Motorsports, etc). Cheers.:cool:
 

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Velossa Tech intake snorkel creates less waste gate duty cycles
Do you have independent numbers to back this up?
 

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No, I do not have independent numbers. I was just going by what the owner told me. From using it for over a year it does work. It's up to the individual if they want to buy one or not. Most reviews are from personal experiences as mine is. If you believe me, great, if not, no skin off my back.

Best regards,

-Mike
 

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So I would have to agree with the general consensus that the Takeda is the one to get over Forge (haven't considered others). Objectively, Takeda presents their performance numbers in a more appropriate manner. They overlay the before and after dyno, and use a seemingly stock car otherwise. Forge shows no comparison dyno and portrays performance increase numbers on a car with additional modifications (performance exhaust). Forge also show dynos for their inlet pipe; these graphs are not overlaid nor do they have equivalent axis'. I don't like companies that make it a puzzle to understand their product. furthermore, there is a great difference between the designs of the two intakes at the filter end. Takeda's use of an air box should allow for better pressure build-up before it goes through the filter. Adding that big gulp snorkel can only improve this. Forge's approach is sheer size dominance, with a massive filter for increased surface area (more air flow). Great in theory, but in comparison to a well designed box, the air turbulence in the engine bay -- while actually driving -- will probably hinder its effectives. It also has access to hotter air than the Takeda does not (easily).
 

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Nice first post. And I agree with your theology regarding the air flow. Nice explanation! Welcome to the forum.

Best regards,

-Mike
 

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Thanks for the welcome. I've been on these forms for a while now (V.org, VT.org); since owning a 2014 VT. These topics have come up many a time and they get rekindled when a new product or supplier comes onto the market. The first gen crowd did not have air box products like those from aFe. Our choices are essentially all the same and are distinguished by brand loyalty; unless you want to make big power where small details matter. I'm enjoying seeing what new products are being developed and doing my due diligence for my future car. From what I've read so far, the VN is such a fun car it doesn't need much in the way of mods. Add a splash of turbo flutter with an intake and your good to go. This is not the case for the 1st gen VT. Anyway, this is a little off topic now for the thread. I hope my first post helped the OP at least.
 

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There is actually quite a bit for the VN. This is what I have done so far:

Uniq collar kit
Mishimoto Catch Can (PCV side)
SXTH Element oil cap
Afe Scorcher piggyback
WhiteLine 24MM rear sway-bar(On softest setting)
Pierce 4pt and trunk brace
Tekada Momentum CAI
Forge turbo inlet
Interior white light led kit
Aem obd2 gauge w/ AeroForce pod
Cerma oil, turbo, and transmission treatments (love this $hit!)
Amsoil 5w30 Signature Series oil (changed at 4500 miles)
Magnetic oil plug
Ttr upper & lower motor mount
Velossa Tech Intake Snorkel (Love it)
GFB recirculating BOV
HKS M45XL Plugs
Redline MT-LV Trans. Fluid
Rally Armor Mud Flaps (Black with red lettering)
RaceArt Solenoid Holder
Wagner Tuning FMIC
MAC BOV Solenoid
JBR Racing Short Shifter and Shifter plate bushings

I am waiting for a new down-pipe right now and my Jet-Hot coated mid pipe will be here sometime next week.

Best regards,

-Mike
 

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So, assuming that all intakes are bottle-necked by the diameter of the turbo inlet, would there be an advantage to having larger diameter tubing leading up to the inlet? For instance, wouldn’t an intake that tapers from 4” to 2” create more pressure at the turbo inlet than an intake that tapers from 3” to 2”?
A transition from 4" to 2" tubing, at the flow rates and pressure we're seeing at peak torque, and using the exact measurements of the silicone coupler Forge supplies, creates about a 0.4psi pressure drop. The air speeds up but the pressure drops. The pressure gradient in the pipe between the compressor wheel and the air filter being low pressure at the turbo inlet and higher pressure outside the air filter means that the air is being pulled through the pipe by vacuum, so drops in pipe diameter and other restrictions cause pressure drop instead of pressure increases. It's basically the reverse of what happens in an exhaust system where restrictions do cause pressure increases. Any pressure drop before the turbo will be made up for by the turbo, but it will also mean is has to work harder to compress the air to the target air pressure (which means more exhaust restriction because the wastegate is closed slightly more to increase impeller speed, which will also increase exhaust manifold pressure and increase pumping losses, and also the turbo compressing the air more will mean it heats the air more).

but...

The length of an air path and number of bends matter as much as the diameter because of the restriction caused by the boundary layer. The boundary layer is the layer of air that sticks to the wall of the tube and the air that stagnates around sharp bends. The air in the middle flows past it, creating friction between the moving air and the boundary layer. Paths that aren't smooth can have turbulent boundary layers which create even more friction. Smaller diameter tubes have proportionally more boundary layer, and the higher air speeds in the tube at the same flow rate means more friction from the boundary layer which results in more pressure drop. So, yes, there is a definite advantage to larger diamter intake pipes, assuming they maintain gradual bends and don't require clearance kinks or have rough transitions.

but wait there's more..

At the same time, the longer the air path is (including the intake tube and airbox inlet feed path on closed intakes) the more boundary layer there is for the air to have to move past on it's travel from the open air to the turbo inlet. So for two equal 3" intakes the one with the longer tube will have more pressure drop. When you get into intakes with and without an enclosed airbox it comes down to how well they designed the flow into the airbox. If the flow path is not optimized it could contribute a lot more pressure drop compared to an open air filter.

At some point I think the pressure drop outweighs the temperature advantage of a cold air intake as far as performance goes. The temperature difference while continuously moving is not much between the Forge intake and the stock intake, so for the type of driving I do I place more importance on pressure drop (and the better airflow associated with minimizing it).

I would assume something like the 4" Forge intake combined with the SXTH turbo inlet (to get rid of that steep 4-2" transition) would have the lowest pressure drop of them all, and one of the long tube 3" CAI's or one of the 3" intakes with enclosed airbox would have the highest pressure drop (or maybe the stock box would be worst with it's contorted inlet elbow and bumpy and protrusion riddled hose, complete with tiny 2" tube before the turbo elbow).

So it would be interesting to see someone connect a differential pressure manometer to the turbo inlet close to the compressor wheel and then at the air filter/airbox inlet and compare between several intakes to see how much pressure drop we're really seeing between all the different designs.

I have considered making a heat shield for the forge filter though, to block radiant heat from the coolant hoses from heating the filter up and keep the radiator fan from blowing hot air right on the filter when the car stops. Beyond that I don't see a reason to sweat over not having a sealed intake box.

Also while we're discussing intakes I got rid of the velossa tech scoop because I noticed it would soak the forge filter in heavy rain, and water will carry dirt through a foam filter. This wasn't a problem with the stock airbox because the water would come into the bottom of the box and drain out and never touch the filter, but now the forge filter sits right behind the exit of the scoop and it would just blow all the dirty road water right onto it. I'm getting the same IAT benefit of the scoop just with the unpatched hole in the radiator shroud where the scoop used to pass through though, but without the water being funneled in.
 
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