987 v 986 Air box

[onaFLYer]

Major difference in size between them, bigger is 987.

There is some modification to the muffler area of the 987 box for clearance, otherwise it bolts right up.

[Brad Roberts]

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

[onaFLYer]

Originally Posted by Brad Roberts

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.

[Brad Roberts]

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

[DenverSteve]

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.

[Brad Roberts]

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 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

[Kroggers]

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

[Brad Roberts]

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)

[tommy986]

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?

[Brad Roberts]

"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

[Brad Roberts]

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..

[Brad Roberts]

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?

[blue2000s]

Originally Posted by Brad Roberts

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?

[Brad Roberts]

Thinking about this

[Brad Roberts]

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.

[blue2000s]

Originally Posted by Brad Roberts

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.

[The Radium King]

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).

[blue2000s]

Originally Posted by The Radium King

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).

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.

[jaykay]

I am struggling with what the contribution of a software remap is to engine power after one has increased air flow rates (without hurting velocity) through hardware changes. If the 25% value is correct, the stock map will adapt.

I can understand remap benefits for where ignition timing is refined for a given fuel quality (anti knock rating). What other benefits can a remap hope for?

Also wondering what power increases everyone has realized with the 987 box. I would expect its real value would be seen on a 3.4 and 3.6L where you may start to get significant vacum readings (MAP) in the intake system. I would only expect a minimal gain on a 3.2. Perhaps I am wrong...just trying to learn. Will my stock air box be good enough up 290 hp or so? Is MAP data via OBDii good enough to see what is working?

Originally Posted by The Radium King

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).

[Brad Roberts]

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