Is cold air intake necessary on a turboed car?
 

After refitting my charge pipes, I no longer have room to run a cold air intake.

Now, my intake hangs off the turbo sandwiched in-between the exhaust manifold and the radiator. It just looks wrong...

I could maybe get some flex hose routed from the headlight area, but there's really not much room. Certainly not enough room to run a hard line to relocate the filter to the wheel well area.

What have others done?

Is cold intake that helpful? Or, does the turbo just heat soak the intake air stream anyway? ... and the intercooler has the biggest effect?

colder air inlet sure as hell doesn't hurt. Look up flyinmiata kit. They use a 90 silicone elbow and locate the filter behind the headlight area with some heat shielding to isolate the heat from the engine bay as much as possible.

I moved this to the DIY area because it is not race prep.

I wouldn't bother with a CAI if you're already turbo. (Though placement is still important)

Turbo will heatsoak either way, and also consider drag if you have lengthy pipe sourcing the cold air.

Why not do some IAT tests of your current setup? :dunno:

Would you be able to post a photo?

it definitely matters, but it's not a dealbreaker

It will look better in my opinion

My box is also cover with insulation on the inside the keep the heat outside of the box as much as possible

https://scontent-ams.xx.fbcdn.net/hp...03&oe=55763499

Next week im beginning my mild wiretuck:facepalm:

I've done both with my old GT3271 setup. Hot air intake, pulling in exhaust heat/radiator fan air, and then a custom CAI. I posted all teh data here when I made it, though it would probably take a while to find. It was worth probably 40HP on my car. It made A LOT more power with the CAI, I had to retune the car cause it went lean! I don't remember how much, but it was very noticable and power went up a good bit, very much worth it. Also AIT's dropped as I wan't dumping as much heat into the intercooler.

IMO it's a must, but a lot of people don't build them. It can be a pain to build, but it does add HP. I gotta build one for my new setup, and I know it's gonna suck, but I gotta do it for the power!

I'd say CAI is power found.

Yes. Pre turbo air temp and pre-turbo pressure drop are the biggest hidden power suckers you can find in a turbo setup. Like pat said, especially on a big power setup, they can kill you. With the subaru EFR stuff people are finding huge power gains going from a 2.5" intake tube to a 3" because of the pressure drop, even a couple tenths of a psi pressure drop in the intake tube puts a lot more heat into the intake charge and drops the max possible boost. Thats more drastic because of how convoluted their intake is, but do not discount the importance of the turbo intake.

I'd worry about a large intake and a quality intercooler as steps 1 and 2, then if you still have issues consider a cold air intake of sorts.

But sacrificing pipe size for cooler air will do more harm than good. Volume is the most important factor with a turbo IMO.

Not always true. The law of diminishing returns applies here. The tubes become a very small percentage of intake system pressure drop when compare to the intercooler once you reach a certain size. For our 250 WHP turbo cars, the difference betwwen a 2.25, 2.5, and 3 in is very small. However, go bellow 2 in and you intake tubes pressure drop will increase greatly as you start to choke the system at your top end CFM.

I guess it's case-by-case, but in the mazdaspeed3 world going from a 2.5" intake to 3" with the exact same routing will net ~10hp with matching tune adjustments. The g/s increase is significant. That's with a k04

yes, case by case. It's a function of max CFM through the pipe which is a function of MAX whp. A 400 WHP speed3 will benefit more from a larger intake pipe than a 250 WHP turbo miata.

Let boost be at 6 psi. The temp gain with turbo is about 14/15F per psi, or about 90°F.

On a 90°F ambient day, ambient absolute would be 90 + 460 = 550F.

The charge temp absolute would be about 550F + 90F from the turbo, which comes out to 640°F

Density would degrade by 550/640 = .86

The pressure ratio at 6 psi is 1.41.

With the heat from the turbo, then the 141% more density from compression will be degraded by .86 x 1.41 to about 1.21. or a 21% performance increase.

With a 90% efficient IC, .90 of the 90°F temp rise will be taken out, or about 81°F removed, thus leaving a net gain of 9°F.

So 550F + 9F = 559F

550/559 = .984

This would leave a density loss of only 2% from the heat, or a net gain of 1.41 x .98 = 1.38. or a 38% performance increase.

----

Now let's say we aren't using a cold-air intake and now we have 180°F temps under the hood (double the ambient!).

460A + 9F (from turbo minus IC removal) + 90F (intake delta increase) + 90F (ambient) = 649F

550/649 = .85

This would leave a density loss of 15% from the heat, or a net gain of 1.41 x .98 = 1.2. or only a 20% performance increase.


Or we can say, if you expect 10rwhp from every 1psi. that maybe the difference between your 100rwhp car going from 148rwhp from a warm air intake to 158.8rwhp with a cold air intake.


something like that. i probably messed up the math, but i dont tend to let facts stand in my way.

not talking about intercooler pipes, we're talking about pre-turbo intake pipes. Even tiny fractions of psi have a noticeable effect here. For example, assuming you're at sea level and your ambient pressure is 14.7psi and your target boost is 20 psi. That results in a 2.36 pressure ratio with no intake restriction, now put an air filter right on the turbo inlet (lets call it a .2psi pressure drop) and you're already up to a 2.39 pressure ratio. Add some fairly restrictive bends in and you're at a 2.45 pressure ratio. To put numbers to this, lets assume that you're getting 100°F air into the compressor with all of them and lets use 70% efficency for the compressor. In the open turbo inlet example you get 320°F air exiting the turbo, with the air filter its 322°F, with the somewhat restrictive intake its 331°F. And at higher mass flows that nearly 10°F temperature difference is a whole lot more heat the intercooler needs to reject to get you down to 20°F above ambient. Now for kicks if that restrictive intake got you to some ambient air of 70°F your outlet temperature is now 288°. Yeah thats a lot, and thats why this post took so long to write I had to re do that math out like 4 times to make sure I didnt fuck up.

What this doesnt account for is if your turbo efficiency goes to shit due to the higher pressure ratio, or if the higher PR forces the turbo to run out of steam. IE, you're running ALLOFIT but, like most compressors, the highest flow area is at a lower pressure ratio.

bigger intake pipes is power found from compressor efficiency losses.

https://www.miataturbo.net/attachmen...ine=1426263792

When I started putting this together, it seemed like I had enough room. But, I found that things were tighter than I thought.

As you can see, I'm using a MAF which takes up some space. Also, my crankcase catch can is also in the way.

Vincentmiata: That cold air intake box looks great! I wonder if I could fab up a container for the filter like yours and then duct cold air into it?

Solution: K&N RC-5052AB, K&N Apollo Unique Universal Air Filter | K&N

I really wonder how much that setup adds in restriction. The walls of the cone being so close to the filter itself add a lot of restriction. It would be interesting to compare pressure drops with a manometer of that filter vs a normal cone filter in a diy sealed box thats also fed cold air from the same type of hose.

From the CFD I've run the spacing between filter and housing wall looks adequate. Typically about 1.5-2 in is ideal. It should taper out some to create a constant press delta past the filter surface. This would load the filter media equally throughout the filter length rather at just close to the filter outlet like most radial filter airboxes. I have some pretty CFD pictures I wish I could share but I probably shouldn't unless we release marketing data on the study for work.

The best part of this system to me is the bell mouth outlet of the filter. This feature can not be created anywhere near a generous of a radius as your typical filter.

I'm considering on picking one up and can run it on the flowbench and post the results.