Air filter/ intake question

[Nick Triesch]

That vacuum hose that plugs into the back of the 3.2 airbox, what does it really do? Is it really a vacuum tube? I ask this because the airbox is not really a sealed unit with the open snorkel. I just wonder if that tube is for vapor rather than vacuum?

[Synchro Joe]

http://forums.pelicanparts.com/uploads20/911_motronic_vacuum12405899401333400906.jpg

Looks to be emissions related, goes back to the carbon canister in the right rear fender well. I found mine loose one time and had not noticed any impact on performance or idle.

[Koizumi]

Originally Posted by Snitzler

I did this, very easy to get at the rear clips. Huge weight savings and tons of extra horsepower. Actually maybe a little bit more intake noise and nothing more. I too have an M&K exhaust. Getting rid of the horn cleans up the engine on the right side a bit.

I have a similar modded box, I quite like the fact that it’s easier to clip and unclip the back like u mentioned.

Bonus is the nice swooshing sound but it’s hard to hear with my Supercup exhaust

[famoroso]

Originally Posted by jlex

Would using a filter like that alter the air intake pressure requiring you to adjust idle speed or (God forbid) MAF sensor adjustment?

No MAF sensor on a stock 3.2.

Also, used air box, replete with trumpet, for sale...

3.2 Airbox

[911pcars]

In our rear mounted engines, there is only cold air intake in the engine compartment when the ambient (outside) air temperature is "cold". IOW, at speed, the intake air temperature is pretty much ambient - whatever it is. If colder intake air is the objective, the vehicle must operate in a colder environment or the air must be treated to remove any latent heat (intercooler, water spray, etc.).

Cool intake air is more of an issue when the air source is typically exit air from a coolant radiator in front of the engine.

Sherwood

[Satanas]

Originally Posted by Koizumi

I have a similar modded box, I quite like the fact that it’s easier to clip and unclip the back like u mentioned.

Bonus is the nice swooshing sound but it’s hard to hear with my Supercup exhaust

I've done the same. Opening the air box is a mistake from a power point of view. (If you don't change anything else) you loose about 10 horse power and the top of the curve is shorter, I mean power drops at a lower rpm. Torque curve is also lower than original air box.

[pmax]

Originally Posted by Satanas

I've done the same. Opening the air box is a mistake from a power point of view. (If you don't change anything else) you loose about 10 horse power and the top of the curve is shorter, I mean power drops at a lower rpm. Torque curve is also lower than original air box.

This supports the notion that the funnel shaped intake improves the airflow and is more than just a "noise suppressor".

[Rawknees'Turbo]

Originally Posted by pmax

This supports the notion that the funnel shaped intake improves the airflow and is more than just a "noise suppressor".

False - it supports the well documented fact that allowing more air to enter the system than it was designed for/around, without then adding additional fuel (via a new chip, WUR adjustment, EFI tune, or carburetor jetting change, where applicable), results in lower engine performance. Get some, pNutz!

PS - it is impossible for that airhorn to have any positive effect on airflow (velocity, etc.) since it is placed prior to the air filter - if anything, it is a restriction. I will learn you a thing or two about a thing or three, yet, bro!!!

[pmax]

Originally Posted by Rawknees'Turbo

False - it supports the well documented fact that allowing more air to enter the system than it was designed for/around, without then adding additional fuel (via a new chip, WUR adjustment, EFI tune, or carburetor jetting change, where applicable), results in lower engine performance. Get some, pNutz!

PS - it is impossible for that airhorn to have any positive effect on airflow (velocity, etc.) since it is placed prior to the air filter - if anything, it is a restriction. I will learn you a thing or two about a thing or three, yet, bro!!!

If there wasn't an airflow concern, what function does the flare at the end of the intake serve ?

That design detail isn't for noise suppression, is it ?

[Rawknees'Turbo]

Originally Posted by pmax

If there wasn't an airflow concern, what function does the flare at the end of the intake serve ?

That design detail isn't for noise suppression, is it ?

It was probably done that way for appearances - looks more race than if it was just a blunted tube, like a vacuum cleaner extension. Or perhaps the intake noise is actually reduced by the flared tip (just the!) - would be interesting to test that.

[911pcars]

I suspect it's based on intake airflow design that's been around for a long time. The inlet curvature produces less turbulent air flow than a straight cut end. Not the same as a velocity stack with an uninterrupted air path to a plenum or cylinder. Any expected power increase by sexy-looking tubes and perceived pressure waves is negated by the presence of an air filter element between engine and outside air.

https://en.wikipedia.org/wiki/Velocity_stack

IOW, looks and a bit of functionality.

Sherwood

[Rawknees'Turbo]

Originally Posted by 911pcars

I suspect it's based on intake airflow design that's been around for a long time. The inlet curvature produces less turbulent air flow than a straight cut end. Not the same as a velocity stack with an uninterrupted air path to a plenum or cylinder. Any expected power increase by sexy-looking tubes and perceived pressure waves is negated by the presence of an air filter element between engine and outside air.

https://en.wikipedia.org/wiki/Velocity_stack

IOW, looks and a bit of functionality.

Sherwood

Exactly, and not to mention the 90 degree bend in that airhorn.