[Slowlearner]

Sorry if this has been discussed already...just delete me if it has. My question is...why have a CAI if the air is going to be heated by the turbo? (thus the need for FMIC) I understand the turbo is not always on...so I guess during those periods a CAI would make sense, but as soon as the turbo kicks in, all that cold air just got heated up. So, what's the point?

 

[swordfish]

A) Turbo is always 'on'. The compression is what increases the air temperature however.

B) The cooler the air that enters the intake the less heated the air gets and the less cooling that needs to occur in the intercooler.

 

[Reaper7]

im sorry buy I don't get the comment, u saying if a cai makes a difference because of the turbo?

 

[lagonwagon]

The OP believes that the heat from the turbo is voiding the benefit of a CAI. Like "The Fish" said though, the colder the air in, the colder the air out.

 

[swordfish]

The OP believes that the heat from the turbo is voiding the benefit of a CAI. Like "The Fish" said though, the colder the air in, the colder the air out.

Yeah. That.

 

[Sixspeed]

I've been researching this very issue for a while now and there seems to be two kinds of thoughts behind the discussion.

Thought #1 states that an SRI is actually better for turbocharged vehicles because the ultimate goal is to get the air flowing through the turbo in the quickest and most proficient manner (which is why some racecars w/turbos run Velocity Stacks). Since the SRI has less piping than a CAI the turbo doesn't have to work as hard to bring in the air. This school of thought also points out that the air goes into a white hot turbo anyways so the air being a few degrees cooler really doesn't make too much difference because that's what the intercooler is there for.

Thought #2 states that CAI is better because as the name implies the intake is able to to pull in colder air which in turn allows for cooler air into and out of the turbo. This cooler air (albeit it being only marginally cooler) allows the intercooler to not work as hard and therefore reduces the amount of time/chance for heatsoak.

Some people on the interwebs have said that a possible solution would be to have a CAI before getting an upgraded intercooler and once the intercooler is upgraded switching to a SRI would be beneficial.

My thought on this whole issue is (and granted I'm not an engineer, but I did stay at a Holiday Inn Express once) is that the whole point of a turbo is to compress more air into the engine to make more power. Cooler air on it's own is more dense. This denser air enters the turbo and gets compressed even more which in theory should increase boost which should make more power. However with that being said, the more compressed the air becomes the more heat it puts off. This means that the turbo could actually potentially get hotter using a CAI vs SRI.

Like I said I'm not an engineer and would love for someone smarter or more knowledgeable than I to chime in.

 

[Dcannon203]

trivial until you get more boost and tuned HP increases..then your primary goal would be larger more efficient FMIC no matter what intake method you use. after that ....methanol injection. on WOT system. or a co2 or meth sprayer for the FMIC. I assume would be the right way to do things..

 

[bgenlvtex]

Air density increases as temperature decreases. The purpose of the turbo is to compound density. Cooler (read higher density) in means higher density to the i/c which means higher density to the intake port.

The ECU sees higher density air so it adds more fuel which in turn increases the smile on your face.

 

[Slowlearner]

Found this info at a thread at DX Engineering. It shows a linear response relating to turbo input and output temps.

Do the case where inlet is 300 Kelvins:

(1-1.8^0.283) * 300 / 0.70 = 77.6 Trise

so you have a discharge temp of 377.6 Kelvins.

Compare that with 260 Kelvins at the inlet:

(1-1.8^0.283) * 260 / 0.70 = 67.2 Trise

giving a discharge temp of 327.2 K.

The temperature ratios are the same, i.e.,

300/260 == 377.6/327.2

So this answers my question. I assumed the reduction in temp from the CAI would be lost in the turbo increase, but apparently the reduction of input temp transfers out as a reduction in output temp. Learned something new today.

 

[nvyseal]

Basically like this,
What freezes faster, hot water or cold water?
What boils faster, hot water or cold water?

 

[Cinderblock7881]

also, ever notice that rather large power difference when you drive your car on a hot day, and then drive it later on that night when it is rather cold? (well that doesn't happen for some of you, but anywho lol) colder air makes more power because of the density.

 

[3Sxturbo]

Cinder- I miss the 20-30 degree difference from day to night.
Man sometimes I miss Cali so bad...

 

[Cinderblock7881]

haha yeah i was typing that and went, ohhh yeah, some places don't have that luxury of temp difference. hahaha.

 

[3Sxturbo]

Haha yup.
Interested. Based of the info the info provided, it seems a ram air system where stock ic was would be the best of both worlds, both quickest route to turbo and providing the most cold air possible without worrying about engine bay temps affecting iat

 

[jared]

Basically like this,
What freezes faster, hot water or cold water?
What boils faster, hot water or cold water?

1:hot water
2:hot water

 

[swordfish]

1:hot water
2:hot water

Hot water will not freeze faster. That's an old wives tale.

 

[jared]

Hot water will not freeze faster. That's an old wives tale.

Mpemba effect - Wikipedia, the free encyclopedia

but usually hot and cold freeze at the same time.

Back to topic.

There are a few factors to take into consideration when comparing an SRI and CAI. The first question raised is the intake temps. Now sitting in traffic the CAI should have lower intake temps since it is getting air from outside the engine bay, but while moving the air under the hood also moves and starts brining in cooler air to closer match the air temps being taken in by a CAI. I think the bigger factor here is the design of a CAI compared to an SRI. The longer tube of a CAI creates a smoother airflow between the filter and the turbo, this is where I think the gains in horsepower are made.

 

[MTD]

Someone should measure the AIT right at the intake manifold after the IC. I would think heat soak would be a bigger issue then an SRI vs CAI.

 

[AZG23]

Someone should measure the AIT right at the intake manifold after the IC. I would think heat soak would be a bigger issue then an SRI vs CAI.

This...and most air moving THRU the engine bay is pulled thru via the fan, thru the A/C condensor, radiator and IC...its not cooler than outside air.

 

[VeloT]

Mpemba effect - Wikipedia, the free encyclopedia

That Wiki seems to say "We really want this to be true, but cant prove it."