CAI for turbo

[float_6969]

OK, so I had a CAI made for the turbo on my car. But the problem was that my girlfriend wanted to take the car down there and have them do it while I was at work and they didn't understand what I wanted.

The pipe is only 2" diameter, and it goes underneath the P/S pump, up twords the radiator, and then down into the fenderwell through the stock opening. The routing is OK, but it's going to make fitting a KOYO radiator and fans very hard later on down the road. I'm less concerned about that than I am the piping diameter.

I've done some rough figuring and I THINK it's going to be OK, but I thought I'd get some outside opinions. I based most of it off of the following statement. He backed this statement up with information, I'm just not posting it here because it's long. Here's what he said..."For ten feet of 1.5"-diameter smooth pipe, calculations using the web pages noted above suggest that pressure loss should be about 1.2 psi at 15 psi boost (near sea level), 360 cfm (before compression) flow (in each half of our IC system), with an air temperature of 200ºF. "Now these numbers are off a little, as I'll never be pulling in 200degree air, and this pipe will be under a vaccuum. He also goes on to say that at the same conditions, a 2" diameter pipe will flow about 720cfm.

So here is what I did. 1.8L=0.0635664ft3So, every 2 rotations of the motor will move about .063ft3So then I took 8000 (redline) and divided it by 2 which equals 4000.8000/2=4000Then I multiplied it by the ft3 #4000*.0635664=254CFMSo I'm thinking that w/o boost, I'm moving about 254CFM of air at redline in a minute. But when you start boosting, you are effectively increasing displacement. Soooo I started over. I figured a [email protected] is approx = 4.5L. So when you redo all the math you get 4.5L=0.158916ft34000*0.158916ft3=635CFM

This just seems really low to me. Maybe 635CFM is a lot more air than I think it is? Somebody show me how I'm retarded please...

[NeedCAforS13]

2 inch intake pipe? That seems excessively small Ryan... Stock is 2.75 I believe. Or maybe it was 2.25. Either way, smaller than stock intake piping seems like a bad idea. Turbos like to BREATHE! And why use a CAI on a turbo, the air is just going to get hot regardless of where you draw it in from. The gains will be minimal in my opinion.

Sean

[DAEDALUS]

I figured a [email protected] is approx = 4.5L.

How did you get that figure? Doesn't 1.5bar just mean each cylinder holds 50% more air than NA? I.e., Isn't 635 cfm too high?

[float_6969]

Well I need SOMETHING on there. I don't even have an air filter right now. I've got a 2.5" adapter that bolts to the front of the turbo and that's it.

Also, I don't see why a CAI for a turbo wouldn't be just as benificial as it would be for a NA car. The turbo is going to add x amount of heat to the air, regardless of what temperature it comes in at. The intercooler is never going to be 100% effecient so the cooler the air I draw into the turbo, the cooler the air entering the motor will be.

Right now, my intake temperatures are running anywhere from 110-130*F. That is mostly just cruising speeds, off boost. The turbo is essentially pulling in air right from underneath the turbo manifold. Very hot air.

[float_6969]

How did you get that figure? Doesn't 1.5bar just mean each cylinder holds 50% more air than NA? I.e., Isn't 635 cfm too high?

I THOUGHT (could have mis-understood) that 1 Bar of pressure (14.7psi) was equal to the pressure of the atmosphere. So running 1 Bar of pressure (boost) onto a motor is effectively doubling the displacement. So at 100% VE, a 1.8L, should move 1.8L of air at atmospheric pressure. So at 100% VE, a 1.8L, should move 4.5L of air at 1.5 Bar (1.5 times the pressure of the atmosphere).

[DAEDALUS]

My bad! I was thinking .5bar boost (1.5atm). Damn that's a lot.

[Dattebayo]

CFM has a quirk of being limited by the plenum design in most air conditioning systems, I dont see why a motor should be any different.

Also the "bar" designation is comparing to sea level pressure. I dont know what the elevation is where you live, but anywhere about 1-2K above sea level (average for most of america) is going to be a significant amount less dense than sea level.

And the CA is not running at 100% VE, an impossible figure to achieve unless you have magical powers that are above the laws of physics.

Now, I dont pretend to be the master motor maker or an engineer, but all these variables have to knock that number down at least some noticable amount...

[nnkfws333]

2 inch intake pipe? That seems excessively small Ryan... Stock is 2.75 I believe. Or maybe it was 2.25. Either way, smaller than stock intake piping seems like a bad idea. Turbos like to BREATHE! And why use a CAI on a turbo, the air is just going to get hot regardless of where you draw it in from. The gains will be minimal in my opinion.

Sean

Yeah true Sean that the air going inside the turbo is hot but imagine air coming in at 60 degrees versus 80 degrees. You would still have a margin of 30 degrees of a difference in a perfect factor and the air will of course get hot but will always have a difference. I mean they do use fans and stuff to cool down the intercooler and draw in cooler air right to get higher dyno numbers...

[float_6969]

CFM has a quirk of being limited by the plenum design in most air conditioning systems, I dont see why a motor should be any different.

Also the "bar" designation is comparing to sea level pressure. I dont know what the elevation is where you live, but anywhere about 1-2K above sea level (average for most of america) is going to be a significant amount less dense than sea level.

And the CA is not running at 100% VE, an impossible figure to achieve unless you have magical powers that are above the laws of physics.

Now, I dont pretend to be the master motor maker or an engineer, but all these variables have to knock that number down at least some noticable amount...

-I'm in Kansas and our average elevatation is is 2000 ft above sea level.-I know 100% VE is impossible, but I was shooting for the upper end. I figured that those numbers would be off, but it was a rough guide. I didn't look into HOW MUCH effect elevation had on the pressures and volume flow. I was trying to keep the calculations simple.

Long story short, what do you guys think? The numbers say that the 2" pipe should work, but that just seems really small. I kinda looked at it this way. As Sean said, the stock rubber pipe is like 2.5/2.75" diameter. There's got to be a reason for that....

[NeedCAforS13]

Also, I don't see why a CAI for a turbo wouldn't be just as benificial as it would be for a NA car. The turbo is going to add x amount of heat to the air, regardless of what temperature it comes in at. The intercooler is never going to be 100% effecient so the cooler the air I draw into the turbo, the cooler the air entering the motor will be.

I can't explain the physics behind it, but I can't recall seeing any turbo cars running CAI's... its not that hard to plumb, so if there were benefits to be had, wouldn't more people run them?

[nnkfws333]

I can't explain the physics behind it, but I can't recall seeing any turbo cars running CAI's... its not that hard to plumb, so if there were benefits to be had, wouldn't more people run them?

People do run them in other cars: WRX, EVO, GTI's, etc.Stock of course you don't see them because of hydrolocking. The only reason why we don't run them in my opinion is because there is just no room for us to get in the fender. All the intercooler piping is blocking us from going anywhere. I mean look at float having to do some serious bends here for it just to avoid everything. Im sure a CAI would do great because they can draw a greater volume of air and better temps because they can get a better flow then under the hood where we have lots of areas that are turburlent and aren't even.

In FI drag cars you do see them put turbos in the hood and in lower spots to get the greater amount of air right?

I think you would have more spooling problems because your not getting enough volume of air by using a 2" pipe.

Im just stating my opinion even though Im still a newb.

[float_6969]

The plumbing problems don't effect me because of my intercooler placement. I actually don't have ANY pipes going down through the fender right now.

[Coldspawn]

I can't explain the physics behind it, but I can't recall seeing any turbo cars running CAI's... its not that hard to plumb, so if there were benefits to be had, wouldn't more people run them?

Because they jump off a bridge, would you do it too?

Simple fact is, colder air = denser air. Now the math.

We will say the car is at sea level and standard temperature (60F).

So, 2.7(14.7psi) / (460+60) = ~.076 Pounds (dense) PER cubic foot of air.

Now lets do 80F (about the difference you will see in a CAI)

2.7(14.7) / (460+80) = .0735 pounds Per cubic foot of air.

More dense the air is, more oxygen it will contain. Plus, the colder the air, more of knock threshold it will have.

Long story short, what do you guys think?

What size is your turbo inlet (ID)?

[float_6969]

What size is your turbo inlet (ID)?

It's an S14 T28, and that adapter that I had made is 2.5" ID.

More dense the air is, more oxygen it will contain. Plus, the colder the air, more of knock threshold it will have.

This aspect of the cooler air is also one that I'm aware of and failed to mention. Due to the nature of this motor, it will be prone to knock. (Increased compression). My goal was to increase throttle response. I don't know how much effect the CAI is going to have on that aspect of the motor, but I didn't think that it would be horribly noticable if the pipe was the proper diameter.

And just to let everyone know, I SERIOUSLY doubt that this motor will actually see 1.5Bar, but it's built to handle it if I decide I want to try.

[Coldspawn]

It's an S14 T28, and that adapter that I had made is 2.5" ID.

When you think in CFM (or as you are doing), you are not factoring in the physics side of it. What you think will happen with you go from 2" to 2.5"? Yes, the 2" may flow what you need (or will need).

Due to the nature of this motor, it will be prone to knock. (Increased compression).

Compression is one factor, but there is more. Chamber and piston design have a great affect on knock threshold. I think you are running like 9.5 I think?

[WeldingHank]

i put a 3" intake pipe on my S14/5 turbo that seemed to help alot with spool up.

[f s t caz]

i don't understand why your talking pressure drops and piping diameter for an inlet pipe. I can't imagine them having an effect on a vacuum filled pipe as the atmosphere is always working hard to equalize the pressure between the pipe and the outside air. I'd think the surface area of the filter, its flow qualities, location and routing of the piping would be of much greater importance. If you want cold air, why not a ARC intake box? Shield the filter from the engine bay temps while bringing air up from the fenderwell over a nice sized area.

[slownslurious]

I was just reading in a magazine that CAI does make the same difference on a turbo as it does on an NA... turbo acts as a heater but it doesn't uniformly heat all air to an even heat... the air passing through it gets hot but its proportional, so 60 degree intake air won't get as hot as 100 degree intake air, etc. So yes CAI would be worth it, but as stated, its rather difficult to do properly. also its cool to have a giant filter sitting there when you pop the hood.

I think 2" is too small, thats even small than what AEM uses on NA 1.7 honda civic motors, and their intake actualy dynos some decent numbers.

[sdtouge]

pv= nr/t peoples

[Dattebayo]

I just felt like I got btich slapped and then quoted for reference at the same time...

Oh well. I know it willmake some difference, but I dont think that your inlet size is going to affect your performance untill you surpass your plenum design. Thats what I was trying to say. Your stock plenum design will not flow well at rates that are as high as 1.5 bar, and all environmetal factors combined, you will not notice a real difference in your performance overall. The only possible problem I could see would be your mid boost throttle response. Once you get the air flowing, the velocity should make the flow just fine.

Point of example: Have you ever seen the intake runners on a Stealth/3000GT VR-4? They are tiny as fcuk! Yet they have the ability and flow to allow that manifold to produce over 1000HP as is.

[rexhunta]

I have an idea. Plumb a duct from your air con duct in your car, to the mouth of the turbo.. make sure it has no leaks !

Turn said air-con onto 18 degrees..

Voila. There you go..Super cooled air going into your turbocharger.

[themadscientist]

I have an idea. Plumb a duct from your air con duct in your car, to the mouth of the turbo.. make sure it has no leaks !

Turn said air-con onto 18 degrees..

Voila. There you go..Super cooled air going into your turbocharger.

That gets a TMS "**** yeah" stamp of approval. I like it!

[rexhunta]

That gets a TMS "**** yeah" stamp of approval. I like it!

Always happy to help

[float_6969]

The problem with comparing a CAI on a turbo to a plenum is the airflow characteristics. The runners of a plenum, don't have a continuous air flow through them due to the openeing and closing of the valves. Therefore, you can, to a certain extent, use smaller diameter runners to increase port velocities and increase the scavenging effect inside the cylnders.

With a CAI, especially on the turbo, the induction is fairly constants while the turbo is spooled/spooling. In this instance, I would actually want to DECREASE the air velocity inside the pipe so that when I closed the throttle and the turbo started spooling down, it would have less inertia and put less load on the turbo. Although, as I'm typing this, I'm having the thought that perhapse increased velocity inside the CAI for the turbo might help with spool up inbetween shifts. I'm not sure which would be more benifical to power though.

[nnkfws333]

Why don't you create 2 of them and test the differences =)

[float_6969]

I will do this actually. I talked to the shop that made the current one, and they said bring the car back down, with the air filter, and tell them exactly what I want.