Cold Air Intake?

[Jims5543]

I searched
"cold+air+intake"
"Cold Air Intake"

and did not come up with much. Unless I own a newer Porsche.

Has anyone designed or fabricated anything interesting?

When messing with my other cars I found wonderful gains from a good cold air setup. Expecially the non-turbo cars.

I keep looking at my airbox sucking in 200° enigne air and thinking something has to be done here.

Another question:

Does anyone have a profile of a 911 with a whale tail showing the aerodynamic drag points on the car. Where is the downforce where is there a vacume?

Thanks for any input or images you can provide.

[masraum]

The theory is that the engine compartment air in our cars is not hot like a regular car because the fans on our engines pull a ton of air.

This has come up before, you may want to try some more searches. Thom Fitzpatrick did some work on his '77 w/3.6L

[Zeke]

I saw some interesting cold air boxes at Ventura. Unfortunately, I did not take any pics. What he did was isolate the carbs from the rest ot the engine bay with some nice looking duct work that fit flush under the grille when the lid was closed. I had a design for the same on my 914.

The thing is, at the grille there is a low pressure area which will deprive the carbs (or whatever you have) of air at speed if you don't have a duck tail or similar device. In stock form, it would be my opinion that the factory setup is better.

[acapella8]

I'm curious to the exact function of the ducktail or whaletale spoiler, I always thought it was more to provide downforce during high accelleration runs.

-Tom
Newbee 78SC

[911nut]

Tbiz did some research that showed the air just inside of the engine compartment to be about 20 degrees hotter than ambient.
I used some heater hose and a tie wrap to make a cold air intake. The tie wrap is used to provide the 90 degree bend in the hose. One end of the hose is shoved into the snorkel and the other end sits right at the engine lid grille. Not elegant but functional.

[wilke3169]

If you ever feel the air box after a drive it is really pretty cool. I was actually surprised the first time I felt it on a cooler evening run. But, even on a warm day it is stilll cool enough I do believe.

[jevvy]

Just as a matter of interest...

how much air does a say 3.2 suck in at decent RPM(I mean induction air not cooling air) - it must be a fair amount and so any engine compartment hot air must get sucked up pretty quick and then replaced by ambient air from outside?

is this the case at all?

[wholberg]

3.2 liters x 5000 rpm divided by 2 crank revolutions per intake volume = 8000 liters per minute at 5000 rpm.

With this kind of air volume, combined with the enormous flow through the cooling fan, I don't believe that hot air in the engine compartment is an issue.

What may be more of an issue is the negative pressure created in the engine compartment, causing the fan and airbox to compete for air. A rear tail creates a high pressure area immediately in front of the wing, increasing airflow into the compartment.

In my opinion, the advantage of a cold air intake would be more due to the the airbox not having to suck air from a slightly low pressure engine compartment, although the gains would probably be minimal.

[jevvy]

thanks wholberg

so thats 133.3 litres a second - thats a lot of air!

[kach22i]

The Cool Duck thread:
Cooling fans and ideas.

There were a bunch of guys a couple of years ago posting their experiments in the forum. One guy duct taped a corrigated air hose to the intake and bent it up towards the grille. He was about to form a cardboard box at the upper lip and seal it off before he threw in the towel. He stopped himself only because their were no seat of the pants gains at that stage, plus feared morning dew and rain water would get into his daily driver (and explode the airbox) before the experiment had run it's course.

I don't have the links, recall printing out some bad black and white prints - stored in a box somewhere.

Below are some related pictures on the topic I have saved, enjoy.

[kach22i]

I found this image useful in drawing overlay studies.

Go for it.



Related aerodynamic threads, hours of reading, links and pictures.

Tail Options: Measuring Real-World Downforce

aerodynamics and airflow

Cartoon examples:
http://www.gmecca.com/byorc/dtipsaerodynamics.html

Aero testing (partial):
http://autospeed.drive.com.au/cms/A_1065/article.html

[sammyg2]

On a N/A 3.2 liter engine I would expect around 80% volumetric efficiency at 5000 rpm, maybe a little better. that would reduce the amount of air getting sucked in to around 6400 liters per minute.

My 3 liter engine should consume around 10,000 liters per minute at 5000 rpm

Boost is good, even fer math

[masraum]

Originally posted by tcar
The ducktail makes downforce by creating a high pressure area at the tail, which is at the intake grille.

Only effective at fairly high speed, though.

Actually years ago ('74 I believe) R&T did a test and determined that there was a difference with the duck tail as low as 60mph.

All of the spoilers that came on 911s reduce lift considerably. The duck tail, whale tail, carrera tail, turbo tail, even the 964 tail reduced the amount of lift over the rear axle. Not only that, but they also increased air to the engine compartment for the cooling and induction.

I don't remember if it is the duck tail or whale tail, but whichever one combined with the matching front spoiler reduced lift at 150mph from 400lb to 40 for the whole car.

[911pcars]

In our naturally aspirated engines, I think the need for a "cold air intake" is overrated.

Sherwood

[wholberg]

A cold air intake might be effective if it could be developed into a "ram air" system that pressurizes the airbox as velocity increases. The increase in HP would occur at higher speeds, but the engineering difficulties and aesthetic challenges in doing this on a rear engine Porsche have been discussed extensively in other threads.

[twin plugged targa]

I saw pics recently where someone had used what looked like 4" plastic drain pipe to poke through the engine grill area (grille absent) pointing forwards. wish I could remember the thread.

[911pcars]

Originally posted by twin plugged targa
I saw pics recently where someone had used what looked like 4" plastic drain pipe to poke through the engine grill area (grille absent) pointing forwards. wish I could remember the thread.

I saw it too, a couple of posts upward. I wouldn't bother with that line of thought.

Sherwood

[kach22i]

Cool air intake links from bookmarks:

http://autospeed.drive.com.au/cms/article.html?&A=0436

The Patent Files: Refrigerated Intercooling

Ford has recently patented an intercooling approach that uses an engine-driven refrigerant system.

The US Patent and Trademark Office and Julian Edgar

AEM Cold Air Intake and Short Ram Air Induction Systems
http://www.coximport.com/aem/induction.html


Banks System
http://www.bankspower.com/tech_coolair.cfm

Cool Air Equals Power

Cool air is good for making power, but could hot air be even better?

[Wavey]

Originally posted by wholberg
3.2 liters x 5000 rpm divided by 2 crank revolutions per intake volume = 8000 liters per minute at 5000 rpm.

With this kind of air volume, combined with the enormous flow through the cooling fan, I don't believe that hot air in the engine compartment is an issue.

What may be more of an issue is the negative pressure created in the engine compartment, causing the fan and airbox to compete for air. A rear tail creates a high pressure area immediately in front of the wing, increasing airflow into the compartment.

In my opinion, the advantage of a cold air intake would be more due to the the airbox not having to suck air from a slightly low pressure engine compartment, although the gains would probably be minimal.

I used to argue that point too, wholberg. A couple of years ago there was a thread about cone filters attached right to the throttle body. Some thought that the intake would pick up hotter air there, I argued that there was so much air moving throi]ugh the engine compartment that it didn't have time to heat up.

Then this thread was recently posted about some real-world temperature measurements, so I now believe it is worth looking at.

Experimental data for Cold air intake

[kach22i]

Originally posted by Wavey
Then this thread was recently posted about some real-world temperature measurements, so I now believe it is worth looking at.

Experimental data for Cold air intake

Great Thread!

How did I ever miss it before now?