What is the tube between the air box and plenum called? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

violametallic-S- · 03-01-2010, 03:57 PM

Hello,

Im looking for the intake tube which is in between the air box and plenum (plastic T") Ive seen a blue silicon type aftermarket replacement a while back and never could find it again. What is it called? and where can i find this?

Thanks

ChrisZang · 03-01-2010, 06:43 PM

I am assuming you mean this (see attached photo)

Dunno what's it called, but there used to be a few companies, which made hi-flow replacements; the only one that I am still aware of is around is AFE.
Google "AFE intake Boxster" and you shall find.

I am thinking about doing the mod but am not willing to pay $200 ~ $250 for a glorified piece of plastic. I also tried Pedro's mod http://www.pedrosgarage.com/Site_3/Make_a_Hi-Flo_Intake.html but wasn't happy with the result (actually more with my lack of skills in fitting plumping parts into my car).

So here's what I am planning to do this week:
I will re-use most of the original pipe and will get rid of the Helmholtz resonator. For that I will cut the pipe in two right in the middle between the rippled part and the resonator and will replace the shorter end with a 45 degree 3" silicon elbow pipe. This then turns this into a $20 mod

If you're interested I can let you know how it worked out

jcb986 · 03-02-2010, 10:47 AM

To be highly technical...it's called a thangmajig....burp.

Gary H · 03-02-2010, 12:41 PM

I replaced mine - the sound is awesome!!

Steve Tinker · 03-02-2010, 02:02 PM

Quote:

Originally Posted by ChrisZang

I am assuming you mean this (see attached photo)

Dunno what's it called, but there used to be a few companies, which made hi-flow replacements; the only one that I am still aware of is around is AFE.
Google "AFE intake Boxster" and you shall find.

I am thinking about doing the mod but am not willing to pay $200 ~ $250 for a glorified piece of plastic. I also tried Pedro's mod http://www.pedrosgarage.com/Site_3/Make_a_Hi-Flo_Intake.html but wasn't happy with the result (actually more with my lack of skills in fitting plumping parts into my car).

So here's what I am planning to do this week:
I will re-use most of the original pipe and will get rid of the Helmholtz resonator. For that I will cut the pipe in two right in the middle between the rippled part and the resonator and will replace the shorter end with a 45 degree 3" silicon elbow pipe. This then turns this into a $20 mod

If you're interested I can let you know how it worked out

Chris - I would be carefull about removing the Helmholtz resonator - I removed mine on my Mazda Miata and immediately lost about 25% of available torque below 4000 rpm.
It sounded better but after about a week I was convinced that I was missing something driving around town - I was, about 25 lb ft of torque which I immediately regained when I reconnected the resonator (they are removable on the Mazda). I thought that they were fitted for only noise supression but an ex Mazda man on the MiataForum confirmed that after lots of testing at the factory, the engineers found the sound wave harmonics actually improved cylinder filling at low to medium revs.

Gary H · 03-02-2010, 02:07 PM

25% of available Torque?!!!

ChrisZang · 03-02-2010, 02:16 PM

Gary,

you did the mod, what's your impression?

Gary H · 03-02-2010, 02:36 PM

Quote:

Originally Posted by ChrisZang

Gary,

you did the mod, what's your impression?

No discernible performance increase I could notice - although if I was being super critical (and trying to justify the $$ spent) I'd say a slight improvement in torque and power from 5.5K up) but for me the noise (in conjunction with a de-snorkel) was worth it

ChrisZang · 03-02-2010, 02:42 PM

cool, thanks

btw: your garage floor and my garage floor almost look the same

Where did you get you bypass pipe?

Cheers

violametallic-S- · 03-02-2010, 07:52 PM

Yes where did you get that pipe setup and how much?

violametallic-S- · 03-02-2010, 07:56 PM

Also can someone confirm if they lost power with this setup? I thought for sure this would help since its a smooth setup without dummy boxes....

Topless · 03-02-2010, 08:44 PM

QUOTE=Steve Tinker]Chris - I would be carefull about removing the Helmholtz resonator - I removed mine on my Mazda Miata and immediately lost about 25% of available torque below 4000 rpm.
It sounded better but after about a week I was convinced that I was missing something driving around town - I was, about 25 lb ft of torque which I immediately regained when I reconnected the resonator (they are removable on the Mazda). I thought that they were fitted for only noise supression but an ex Mazda man on the MiataForum confirmed that after lots of testing at the factory, the engineers found the sound wave harmonics actually improved cylinder filling at low to medium revs.[/QUOTE]

Confirmed. That silly little box thingy (Helmholtz resonator) in the intake serves two purposes: Noise suppression and improved midrange torque. It is part of a "tuned intake" and removing it may leave a trough in your torque curve. Caveat, I have not done the math on this but I am betting a bright engineer in Stuttgart has.

For more info on what it is and what it does: http://www.sae.org/technical/papers/2005-01-3803

Ultimately though it is your car and you can mod it as you see fit. I am just passing on what I know about the intake resonance concept. My dad designed "tuned jet engine intakes" for Northrop and Rohr. Intake resonant frequency and acoustic standing waves were regular dinner table conversations, much to my mothers disappointment.

Steve Tinker · 03-03-2010, 12:24 AM

Thanks for the link Topless - your SAE paper seems to confirm my findings.
Ricardo Engineering has an enviable reputation in Europe for their state of the art engineering going back to the 1920's, probably one of the best consultants in the world....
We all want to improve on the design or efficiency of our vehicles, but sometimes the factory engineers who have access to millions of dollars worth of equipment really know what they are doing - or at least should do....
Unfortunately, the bean counters have a bigger and bigger hand in the final product.

ChrisZang · 03-04-2010, 12:13 PM

OK,

you guys got me thinking. So I'll first source a used intake and then try the mod.
If anyone has one lying around let me know. I'll also post in the classifieds

Boxtaboy · 03-04-2010, 12:21 PM

Wait a second...from what I'm reading, people are saying you lose torque from doing this mod, and so you're gonna do it anyway?!

Gary H · 03-04-2010, 12:24 PM

I'm sorry, but can someone spell it out to me: I can find references to Helmholtz resonators relating to noise suppression...and that's it.
Having an expanded air reservoir POST MAF/Throttle body can make a huge difference to the available torque - I had this bulbous looking cross-over pipe on my old Miata and it made a huge difference...but this is um-metered air before it gets to the throttle body.

So the Helmholtz resonator on the snorkel is there for added torque?

And there was me thinking it was ll about noise reduction and passing certain EU noise levels...

ChrisZang · 03-04-2010, 02:10 PM

Quote:

Originally Posted by Boxtaboy

Wait a second...from what I'm reading, people are saying you lose torque from doing this mod, and so you're gonna do it anyway?!

Yeah, if I don't try I'll never know - won't I?
But by securing a spare pipe I can go back to OEM

makes sense?

And actually I don't think that torque will suffer

Topless · 03-04-2010, 04:08 PM

Chris, give it a try and let us know what you find. If you can measure your results you will know for sure if power improved. 30-70 mph times work pretty well for performance testing our cars.

For those interested in more information on induction tuning, intake acoustic resonance, helmholtz properties, and how standing waves affect engine torque, this may be useful:
http://dinamoto.it/DINAMOTO/8_on-line_papers/risuonatore/risuonatore.html

manolo · 03-04-2010, 04:57 PM

I would love to see some data on this. I've seen AFE's dyno chart but Im skeptical.

Steve Tinker · 03-04-2010, 08:12 PM

The engineering paper that Topless link shows us is only the input side of the internal combustion equation - even more complicated is the exhaust gas / muffler variations available. And one can definately affect the other.

Going back to the original question, it would have been so much easier for Porsche (or Mazda) to simply bolt on an inlet manifold sans Helmholtz resonator like Chris & Voilamettalic plan on doing BUT (as Topless says) a lot of clever engineers have done the calcs and come up with a resonator that fills the cylinder with a more efficient charge - and for very little money. How could the accountants complain. If the Helmholtz had cost $500 to produce, it may be a different matter.

Many years ago, we were trying to improve Manx Norton & AJS 7R motorcycle race engines to try & complete with the Japanese 2 strokes and it was quite common to replace the Amal GP carburettor inlet trumpet length to move the power band up or down the rev band. At the same time, we were changing the length and shape of the exhaust to prevent "megaphoneitis" a phenomenon where a hole appeared in the powerband and you went backwards so to speak. This was long before dyno's or ignition curves & power printouts.

I'm not saying don't try the mod - after all its not going to cost a lot and it can be reversed, but personally I must have spent hundreds of hours trying to "improve" basic physics concepts on motorcycles and cars, all designed by far cleverer engineers than me, and all I mostly got was blooded knuckles & negative results. Maybe I should have studies Mech Eng instead of Elec Eng.....