987 v 986 Air box
 

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Major difference in size between them, bigger is 987.;)
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There is some modification to the muffler area of the 987 box for clearance, otherwise it bolts right up.http://986forum.com/forums/uploads01...1323828453.jpg

We trimmed it back a little farther. Can you show us how you made the cover for the opening? :)

I just covered the hole with a piece of plastic and glued it on. Had visions of making a smaller muffler with the cut off part, but decided against it. I want it to make noise. With as much as I have going into this car and engine, I plan on keeping it for a long time. Not concerned about resale at this point.

We glued and bolted an aluminum plate over the hole :) Used the typical 10/32 cap head screw and some nylocks.

I appreciate the information, and photos. But, I have to ask.... and what? Bigger doesn't mean better. Have you run flow tests on the two? Is there some expected result you were hoping for, and achieved? Thanks in advance.

I started with common sense :)

Hum.. I have a 3.4L CaymanS engine in a 986 Boxster, I wonder if I should run a CaymanS intake box? (question I asked myself)

We had a custom cone filter setup in the engine compartment, but they do not seal well to the engine lid or the chassis, and we would see intake air temps 40-50 degrees hotter after just 30minutes of running the car than we did in a stock CaymanS :barf: Cold air makes power (or at least closer to ambient)

I had been involved with CaymanS 3.8 conversions and knew the stock box seemed to work just fine with the larger GT3 throttle body on a 3.8

The stock box is too small for the 3.2..... about right for the 2.5 and 2.7 (same piston size in both engines)

When we see vaccuum at full throttle on the dyno, it means something in the intake system is too small and if the intake and the engine is stock..... it means the air box (to me)


B

Thanks Brad. It could be common sense, with some of the follow up information not previously seen. Did that vacuum go away?

It's tough online to see me smiling when I post "tongue in cheek" comments :) Thanks for not getting offended. It was meant in jest.

Yes, it went away and the engine air inlet temp went WAY down. Down to what we expected to see based on a stock CaymanS. GM has a division dedicated to inlet air temp on the Corvettes. After meeting a person who works in that group, and what I have seen on professionally raced Boxster's and Cayman's... I take air inlet very serious (to the point of covering the entire intake/air box/piping in the gold foil to keep the temps down. Heat kills!!!

Porsche cut the nuts off the Boxster's and Caymans. The trend for larger throttle bodies and larger headers is well founded, but you have to match it with a larger air box. So far the CaymanS airbox has proven to be *good* up to 420hp. I have not tested past that (GrandAm M97 engine in a CaymanS)

I keep looking at the air box on my racing car and wondering if there is not a better way to get cold air with higher volume into the engine. I was considering putting a plate on the location of the factory air box and running a tube out closer to the side of the car for the air filter - or how about relocating the air box/filer to the rear boot. That would give a straight line from the filter to the throttle body/plenum.

Then the air filter could be feed with air via a scoop on the rear trunk or even the roof?

Just an amateur thinking-out-loud, so sorry if this is all just stupid talking :D

Brad,

Do you have any experience with running an intake duct sealed to the outside intake "scoop" running to the throttle body....insulated of course. I have seen a fellow on here who did a marvelous job. I would think intake temps would be reasonable. The air would be spending less time running around the engine compartment...like a heat exchanger.

I would certainly like to put in a Cayman S box (MY year?) but I am still not seeing how one can possibly get it in. I am not understanding the muffler cut either.

The Cayman box plus the IPD might give me enough juice to get by some older 911s on the track

questions for Brad.

1. can the swap to a cayman airbox be done with the engine in the car?

2. where are you sourcing the cayman airbox? Model year and what price?


thanks

In addition to my questions above, I was wondering if the MAF housing was the same diameter as the 986? if not, do you use the 987 MAF sensor in the 986?

Reading the replies now.. didn't receive a notification that someone had posted :(

Tommy,

you want to use the CaymanS MAF housing. It holds the same MAF your 2000 car runs.

I happened to have one close to my desk. I'll show you the CaymanS MAF holder and boot, then show you the 986 (side by side)


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B

As far as pricing goes, I expect to pay about half of new when buying these parts from places like LAPD/OK Foreign/PartsHeaven

Part number: 987.110.021.00 NEW Price from Porsche is $560.00

You will find it in cars from 2005-2008 ALL 2.7/3.2/3.4 cars.. all of them..


B

Stock 2.5/2.7/3.2 utilize a 74mm diameter inlet at the MAF sensor.

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CaymanS utilizes a 82mm opening!!!!

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Just noticed the spider in the BoxsterS MAF tube.. LOL

Tidbit of info: The 987 tube has a MUCH finer screen to help protect the MAF compared to the early 986 style (The 987's rarely kill a MAF like a 986 does)

JayKay,

I have not seen exactly what you are explaining, but I do understand the concept and yes, anything you can do to seal the aftermarket "cone filter" setups to the outside of the car.. is GOOD!!

Muffler: Porsche has installed a resonator chamber/muffler to decrease (or control) the sound of the intake on the Boxster's/Caymans. They accomplished this by a "pimple" hanging off the intake tube, on the 2005-08 cars this "pimple" was part of the air box right where it makes its transition to the throttle body.

I'll show you with a picture..

thanks for the great pics and info.

So I can just re-use the MAF from my 986S but put it in the 987 housing. Its not calibrated to the tube diameter?

Can the housing swap be done with the engine in the car?

"can the housing swap be done in the car"

Yes, but you will be removing the drivers side intake plenum

"So I can just re-use the MAF from my 986S but put it in the 987 housing"

Yes. Correct.

"Its not calibrated to the tube diameter"

The MAF is not. The computer will adapt

If you use a larger MAF housing diameter without reprogramming or otherwise changing the signal, the DME won't be calculating air volume correctly. The car will run leaner than the DME thinks it is.

I do tune the cars that I have used this setup in, but I also believe that the stock ECU (no flash or tune) can easily adapt for this and headers.

This really is only slightly different from installing a cone filter setup.

Thoughts?

I have doubts. The DME uses the MAF to measure air speed. It needs to convert that speed to volume flow so it knows how much air the engine is injesting. The conversion calculation has to include the diameter of the MAF housing.

Increase the MAF housing without telling the DME and it thinks the airflow is lower than it really is. Same speed + larger area = more flow. And not a little difference, it's a 23% increase in area! Huge! I would be really surprised if there was some way the DME can compensate to that change.

It means Porsche would have had to allow for housing changes while programming and then figure out a way to double check the sensor. I don't see a system that can make the correction. You know how slow O2 sensors are, they aren't fast enough to make a meaningful correction. They are mostly used for steady state (cruising) corrections. And there is no MAP sensor to verify flow with a pressure measurement.

I bet when you do a tune, the car is running very lean to start, yes?

Thinking about this :)

They are not lean to start, but I know why they are not lean.

Funny part? I run the cable cars with the MAF disconnected pretty regularly. The base map in the ecu is pretty damn good..

Still thinking. Everything you posted makes perfect sense. I understand what we are doing (I'm not using this on anything smaller than a 3.2) but I will in the future.

The base map with the MAF disconnected probably runs fuel metering off the throttle position sensor. So it's probably fine as long as you don't mess with the cylinder filling efficiency of the engine (very free flowing exhaust and intake) and you don't change the size of the throttle body. If you do those, it'll probably go lean again. But the non-MAF map is probably conservative to begin with so it might bring the fuel level to about right.

Correct. TPS metering. The throttle response is not as crisp when I have them disconnected.

I have seen multiple cars adapt upwards of 20hp with no computer change, knowing that we changed the plenum (after MAF changes)

Typing out loud

With safe AFR's?

I'll install one of these on a stock 3.2 engine with headers with a before and after A/F readings. I have a gutted stripped 3.2 race car in the shop that will be easy to install one on. I'm pulling the engine this week anyway!


B

i've been looking into tuning recently and here is what i think i know:

dme looks at (a) maf signal (amount of air going into the engine) and (b) rpm, to determine how much fuel to deliver via the injectors. this is done using a 3D, 3-axis map (x=rpm, y=quantity of air, z=amount of fuel required). these are the maps that get modified by tuners to increase performance.

dme then looks at exhaust o2 sensors to see how things went during combustion. depending on the amount of oxygen in the exhaust, the dme either adds or removed fuel by lengthening or shortening the injector pulse.

this information is put into a short term fuel trim map (stft) as a % modifier of the primary map.

if the stft stays stable (ie, over about 50 kms of driving) the data is transferred to the long term fuel trim map (ltft). this is your dme 'learning'.

if you find that your ltft is staying at a constant value (ie, +5% due to intake modifications) tuners can go to the maf calibration map and calibrate it so that your ltft zeros out. you may wish to do this to make room for other modifications, as max ltft is 25%.

so, if you put a 3.5" diameter maf housing on a car that needs a 3" housing, you are looking at a maf that is reading 36% out (pie are square, right?). dme can't adapt to such a significant change. worse, your engine will be getting more air than it thinks it is and run lean - hard on engines (no cooling). you can do it, but a dme remap is required.

however, it also shows that those who state their intake products require an expensive remap (which they also sell) to realise full benefit are wrong, unless airflow is increased by more than 25% (not likely).

That should be interesting. Hopefully it's interesting, anyway.

Porsche runs these super lean anyway, but yes, more than safe.

King,

you pretty much nailed it. nearly verbatim to what Porsche has released in factory bulletins!

I'm all up for learning :) Now, sharing what we have learned? Not always :)

That's never a problem for me, I always know all the answers :D

Brad, do you think I'm safe to run the stock tune with the 987 box and stock throttle body? I plan to upgrade the TB and plenum at a later date, and probably headers, then tune it to match.

Let me get it installed in a stock Boxster-S with headers. I'll use a stock CaymanS throttle body on the 3.2 plenum and report back with numbers.

It all makes sense. But I wonder if the DME just makes small corrections to one load/speed point on the map at a time or if it tries to smooth the map around the point of correction. The O2 sensor isn't fast enough to relay good data while the engine is dynamically changing, like changing loads or RPM. It needs the engine to be steady for a while to know what the conditions are at the intake relative to the exhaust.

Although, I suppose if they charactorized the lag, maybe they've figured out how to use that data too. Maybe.

BTW, there's a really good book on the principles of engine tuning by Jeff Hartman. Also, the manuals for the programmable EMS computers are mostly available online. They give a good overview as well. But nothing beats doing an engine yourself. I learned more with my Haltech than I could ever have by reading about it.

I managed to get my hands on an actual Bosch .pdf explaining exactly how the 5.X and 7.X work. I should dig it up and throw it on a server for download. It is the most comprehensive break down I have ever seen published (I just can't regurgitate verbatim)


B