[snova]

Hi All,

 

So I performed the Airbox modification and I got to thinking.  Seems that ditching the snorkel all together to get air into the additional air holes might be losing out on the benefits of the snorkel.   As I understand it, the snorkel is designed for two things.

 

1. Get colder air from better location.

2. Direct and route that air into the air box.

 

Without the snorkel seems that we are losing both benefits

 

I'm considering modifying the snorkel and reattaching it in conjunction with the airbox modification.  So the goals are

reconnect the snorkel which is held by two screens on the airbox.  Add an opening into the snorkel once the air has passed into the chamber just on the outside of the airbox.    I was thinking of cutting out the bottom side of the snorkel in this chamber.  Leaving the top side to do a few  things.

1. allow the snorkel to be held in place

2. as an air deflector to both keep the air from escaping straight up into the engine bay past the airbox

3. spill air to the added sides ports as part of the airbox modification.

 

Thoughts?

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[Chris Vais]

Removal of the snorkel and installation of the intake ports works best with the plastic engine shroud that was standard equipment on the earlier production cars. If your car doesn't have it, and you can't find one to buy, I would recommend the RS Barn Airbox shroud. With either of these items installed, only cool air gets routed into the airbag.

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[snova]

Removal of the snorkel and installation of the intake ports works best with the plastic engine shroud that was standard equipment on the earlier production cars. If your car doesn't have it, and you can't find one to buy, I would recommend the RS Barn Airbox shroud. With either of these items installed, only cool air gets routed into the airbag.

Thanks Chris. I have the plastics engine shroud.  This is in addition to the shroud.  If the snorkel is already stopping the air from going above  the main inlet port, then why remove it?  Why wait for it to get deflective off the top of the shroud?   If the goal is to get air to the side ports then why not open up the snorkel from the sides and blow to get air flowing into those side ports instead of ditching the snorkel completely?

 

my point is Porsche could have left off the snorkel if they felt that air would blow in there just fine.  This is what the airbox mod is assuming however, when it says ditch the snorkel. Instead Porsche did not assume that and went to the trouble to get the air up in there from someplace else and engineered in the snorkel instead of just expecting that COLD air will just blow in there.  Thats what I am asking about getting feedback on.  Can we do better than just ditching the snorkel all together by allowing it to feed the main inlet as originally designed AND spill over into the side inlets.

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[MCL968]

The sound limits imposed on German cars necessitated the use of the snorkel. The intake sounds on these cars are impressive, by opening up the airbox and changing the exhaust, the cars sound like they should have sounded from the factory (IMHO).

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[snova]

The sound limits imposed on German cars necessitated the use of the snorkel. The intake sounds on these cars are impressive, by opening up the airbox and changing the exhaust, the cars sound like they should have sounded from the factory (IMHO).

  If I understand you correctly, you are saying that an UNMODIFEID airbox but without a snorkel attached will be louder?  Why is that?

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[Roboman]

The sound limits imposed on German cars necessitated the use of the snorkel. The intake sounds on these cars are impressive, by opening up the airbox and changing the exhaust, the cars sound like they should have sounded from the factory (IMHO).

Interesting and thank you MC, I'm at the point of doing the same mod, but a few weeks back had the bumper off for another job. I was amazed that the snorkel pointed into an area of very poor airflow. So what was the fundamental point of the engine? What as the point of reducing the airflow?

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[MCL968]

I would guess it's because what you are hearing is the turbulence, and the snorkel places the exit for the sound further from the source, allowing destructive interference to occur and the waves to cancel each other out. Logic would dictate that a 3 liter engine, running at high RPMs, would have a bit of a challenge getting adequate air through that snorkel. Our Volvo is a 2.5 liter 5 cyl and it has a much larger intake than the stock one on my 968.

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[Roboman]

Again MC I'm with you. Given my now very amateur operations, I'm going to have to make mods and get out there with a stopwatch... Very amateur, but I am in rural France!, edit, I should say I'm in rural anywhere... Not just Fr, I just don't have access to accurate measurement.

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[MCL968]

The velocity stacks are off of a motorcycle airbox, and the groove was exactly the right size for the plexiglass I used. There is a baffle inside the airbox that needed to be trimmed, otherwise it was pretty easy with a Dremel, a holesaw, some double sided foam tape and some nuts and bolts.

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[Roboman]

Thanks again MC. I'm probably going to follow the mods to the bottom half. I feel there are gains to be had in the top section

; I'll let you know.

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[snova]

Interesting and thank you MC, I'm at the point of doing the same mod, but a few weeks back had the bumper off for another job. I was amazed that the snorkel pointed into an area of very poor airflow. So what was the fundamental point of the engine? What as the point of reducing the airflow?

I think the point is to place the intake to the snorkel in a location with RELATIVELY low ambient temperature.   Since the intake in on top of the engine and airbox not that much lower, it seem that relative temperature wouldn't be that great compared to UNDER the car or shield away from the heat of the engine.

 

In short, I think its about air temperature (i.e. colder = more dense air than "ram" air flow.   Also, if the source is cold air the and entry into the manifold is relative warmer air, I would think this would create a air draft effect once the air inlet value opens up in the cylinder to suck in the air / fuel mix on the intake stroke.

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[snova]

as far sounding louder without the snorkel, I would love to find out if it actually is louder by simply removing the snorkel with an unmodified airbox. 

 

Roboman, do you have any interest is trying this out before you modify your airbox to see if you can hear any difference?

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[MCL968]

as far sounding louder without the snorkel, I would love to find out if it actually is louder by simply removing the snorkel with an unmodified airbox. 

 

Roboman, do you have any interest is trying this out before you modify your airbox to see if you can hear any difference?

You raise excellent questions, many of which have been raised and answered by our predecessors. Suffice it to say that most of us who have made the modifications to our air boxes believe we have improved the performance of our respective cars. Most were and are satisfied with the outcome. Whether it's self fulfilling prophesy, cognitive dissonance, the pygmalion effect, or the Hawthorne effect, we like it are glad we did it. I have modified the airbox, added an RS barn exhaust and chip, and I think the car has slightly more power. I have also added the D1R stiffeners and Koni inserts/shocks and I believe those modifications have further improved the car. I have no data to back these claims up, only the experience of driving the car when it was stock compared to how it is today.  Overall, I like it better now.

 

Ultimately it's your decision. With the alleged growing interest in these cars, and the equally alleged increases in their values, you may be wise to leave your car unmolested and drive as Dr. Porsche intended.

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[snova]

You raise excellent questions, many of which have been raised and answered by our predecessors. Suffice it to say that most of us who have made the modifications to our air boxes believe we have improved the performance of our respective cars. Most were and are satisfied with the outcome. Whether it's self fulfilling prophesy, cognitive dissonance, the pygmalion effect, or the Hawthorne effect, we like it are glad we did it. I have modified the airbox, added an RS barn exhaust and chip, and I think the car has slightly more power. I have also added the D1R stiffeners and Koni inserts/shocks and I believe those modifications have further improved the car. I have no data to back these claims up, only the experience of driving the car when it was stock compared to how it is today.  Overall, I like it better now.

 

Ultimately it's your decision. With the alleged growing interest in these cars, and the equally alleged increases in their values, you may be wise to leave your car unmolested and drive as Dr. Porsche intended.

Trying to strike a balance. That's why I bought a used air box and modified that instead of the one which came with the car. Relatively easy to swap back to the original in case I ever want to go back to stock.  No harm no foul.  Since I also have a spare snorkel, I may modify that as well and see if I can feel a difference in the middle of the summer.

 

I was hoping to hear someone say..  "no don't put the snorkel back in modified because ....." and thus it will make things worse.   

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[Roboman]

Hi Guys, once I'd seen what I thought was the "interesting" positioning of the snorkel I did think that I must try it with just cutting the bend off it.


So, with a caveat of my less than perfect testing system, I'll go through the various modifications and test along the way. My plan is to do repeat runs in opposite directions under as identical-as-possible conditions. Luckily my recently installed cruise control should help.


As you say, I'll just be tinkering around the edges, so I can still restore it to its original condition. I'm a little way off doing the work, but when I get to it I'll let you know the numbers.


Cheers

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[snova]

@Roboman,

 

keep in mind that air doesn't get pushed into the snorkel.  A vacuum is created by the intake manifold from the intake stroke and air is sucked in.  So its more of an air flow pull than it is a push. 

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[Roboman]

Thanks guys, more later ...

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[Roboman]

I mused that the positioning of the snorkel was to cool the air traveling inside it, but I think the rate of flow is probably too fast for any real cooling. Anyway, thanks for now guys, more later ...

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[J.Elenbaas]

I don't think sound is ever been an issue in Germany, as Porsche also make there watercooled 911's to produce the sound of the aircooled one's.

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[flash]

i barely pop in here anymore, but when i saw this, i thought i would kick in my two cents worth.  i will step in now, because this was a pet project of mine, and i don't want to see people led astray.

 

i recommend reading the materials here.  i did EXTENSIVE testing of pretty much every possible permutation of this mod when dave and i were designing it.  i spent a fortune at the dyno testing everything.  i then wrote a magazine article about it.  further testing was then done when i was developing the supercharger.

 

in summary though, the snorkel is there to both pick up cold air from the lower grill, to control noise, and to pass emissions tests and cold start tests.  in normal use, the snorkel is not needed, and in fact limits the air intake.  removing it improves performance, but in extremely cold environments, can make for harder starts, and the noise will increase.

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