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Old 12-19-2011, 11:24 AM   #1
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Engine air intake - why did Porsche do this?

It is very possible that I am missing some really smart engineering by Porsche here, so I am sorry if this is obvious and I am missing the point

Whilst working on the air intake on my racing car I was aligning up the factory grill minus some bars to get a feel for how the air flow is moving into the filter - and I am really confused by what I see.

This can not be good for air flow? Include to this the fact that the bottom two grill bars are solid. the air can only enter from the top half of the grill and then it is directed into the side corner before winding it's way down to the entry to the air box.

What am I missing with this design???

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Old 12-19-2011, 11:39 AM   #2
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You are right about that. The only explanation is that this is Porsche's way of making it much less powerful than the Porsche 911 so that it does not compete with it.
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Old 12-19-2011, 12:32 PM   #3
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read this

http://www.renntech.org/forums/tutorials/article/141-desnorkle-your-986/

as far is i understand, the snorkle was added to US cars in order to stand with noise regulation.
the engine will be more noisy with out it and it sound great. just removed it yesterday from my car.
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Old 12-19-2011, 01:12 PM   #4
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There are several issues to consider regarding the Boxster intake design:

1. Foreign particle ingestion - design should allow large particles/items (dirt, pebbles, leaves, cig butts, etc) drawn into the air intake to "fall out" of the air flow prior to the air filter
2. Water ingestion -- design should allow any water drawn into the air intake to "fall out" of the air flow prior to the air filter (including driving in heavy rainfall, carwash jets, solid splash of water from car in next lane, etc)
3. Intake noise - if needed, help meet overall noise standards
4. Performance - meet engine performance standards
5. Cost - meet (or be less than) the cost goal
6. Packaging (space limitations) - fit into the allocated space
7. Ease of assembly - easy to assemble in the factory
8. Maintainability - does not require periodic maintenance
9. Durability - long lasting
10. Repairability - easy to remove and replace

Based on all of these (and many more) criteria, the Porshe engineers came up with the design as implemented and as such, it is sure to be a compromise between performance and the other criteria.
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Old 12-19-2011, 07:32 PM   #5
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OK, so bottom line, this is a compromise made by Porsche to ensure reliability etc and the cost of performance.

As this is a racing car, I would therefore do better to alter the design to allow for a straight line for the air to get to the filter - is this correct or am I still missing something?
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Old 12-19-2011, 07:56 PM   #6
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You are correct in the straighter and smoother the airflow, the better!

All I was trying to say is that the Porsche engineers had to take a lot more into consideration than just performance. I'm not saying that they came up with a perfect compromise or even a clever one, just saying that there is alot of of often conflicting goals to try to meet in a single design.
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Last edited by thstone; 12-19-2011 at 07:59 PM.
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Old 12-19-2011, 08:05 PM   #7
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Quote:
Originally Posted by Kroggers View Post
It is very possible that I am missing some really smart engineering by Porsche here, so I am sorry if this is obvious and I am missing the point

Whilst working on the air intake on my racing car I was aligning up the factory grill minus some bars to get a feel for how the air flow is moving into the filter - and I am really confused by what I see.

This can not be good for air flow? Include to this the fact that the bottom two grill bars are solid. the air can only enter from the top half of the grill and then it is directed into the side corner before winding it's way down to the entry to the air box.

What am I missing with this design???

Something doesn't look right in that picture. Are you trying to use a 987 intake?
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Old 12-19-2011, 09:11 PM   #8
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Water and foreign object ingestion was a problem on first generation Boxsters. If you are building a race car and never plan to run it in the rain, why not mount a roof intake scoop and a nice large flexible intake duct directly to your air filter box, GT-1 style:
Carbon Creations Carbon Creations Universal Hood Roof Scoop 1 - 102894
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Old 12-19-2011, 09:40 PM   #9
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Water and foreign object ingestion was a problem on first generation Boxsters. If you are building a race car and never plan to run it in the rain, why not mount a roof intake scoop and a nice large flexible intake duct directly to your air filter box, GT-1 style:
Carbon Creations Carbon Creations Universal Hood Roof Scoop 1 - 102894
Yes, it is a dedicated racing car, but we do have some wet racing as well - can not plan every race to be in the sun

The filter location in my 911 and the motorbike is more open than on the Boxster and I have never had problems with rain whilst driving. I will assume water getting to the filter is more of a problem when the engine is not running...

The scoop idea has been considered and an interesting option, but our class regulations does not permit any "new" holes to be put into the firewall or covers that separate the engine from the driver.

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Something doesn't look right in that picture. Are you trying to use a 987 intake?
Sorry to say, but that is the factory design. You are looking at the grill section from the 986 air intake scoop mounted against the side of my 986 racing car.

The only thing that is not as factory is the fact that I have removed the air box, so the normal snorkel thing is not in the picture.
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Old 12-20-2011, 06:43 AM   #10
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Interestingly enough I once had paper numbers taped to my doors for a track weekend.
It rained for most of it. Eventually the paper desinigrated with bits and pieces streaming all along along the sides of the car. There was bits stuck to the intake scoop. I pulled the air filter and it was clean nothing made it through.

On another occasion I have found seeds in there

I am desnorkled
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Old 12-21-2011, 11:18 AM   #11
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Originally Posted by Kroggers View Post
It is very possible that I am missing some really smart engineering by Porsche here, so I am sorry if this is obvious and I am missing the point

Whilst working on the air intake on my racing car I was aligning up the factory grill minus some bars to get a feel for how the air flow is moving into the filter - and I am really confused by what I see.

This can not be good for air flow? Include to this the fact that the bottom two grill bars are solid. the air can only enter from the top half of the grill and then it is directed into the side corner before winding it's way down to the entry to the air box.

What am I missing with this design???

Quote:
Originally Posted by blue2000s View Post
Something doesn't look right in that picture. Are you trying to use a 987 intake?

Is that fire flames on the side of the car? Cool.
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Old 12-21-2011, 07:34 PM   #12
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Is that fire flames on the side of the car? Cool.
Nope, it is the racing team logo



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Old 12-21-2011, 08:56 PM   #13
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Now that what I call a lowered Boxster - hell, you can hardly see the top of the wheels let alone the tyres.......
I bet the turning circle is - er - somewhat restricted !!
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Old 12-21-2011, 09:03 PM   #14
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Now that what I call a lowered Boxster - hell, you can hardly see the top of the wheels let alone the tyres.......
I bet the turning circle is - er - somewhat restricted !!
No, there is no problem with the turning circle. Did have some rubbing on the rear at the start of the 2011 season, but fixed that after the first race with a grinder

Remember this is a dedicated racing car, so the suspension is rather stiff and the geometry set-up for track use - I would not want this configuration on a street car!
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Old 12-22-2011, 03:13 PM   #15
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No, there is no problem with the turning circle. Did have some rubbing on the rear at the start of the 2011 season, but fixed that after the first race with a grinder

Remember this is a dedicated racing car, so the suspension is rather stiff and the geometry set-up for track use - I would not want this configuration on a street car!
Wow, with that low rear end, I would guess the lower control arm is past horizontal such that the rear roll center is "below ground", thus increasing the rear roll couple, or have you relocated the lower control arm pivot points?

Anyway, regarding de-snorkling, it looks like a good idea to me for a race car, and I think I'm going to do that on my part-time race car that is almost never driven in rain anyway.

Good luck...
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