987 Airbox-Worth it?
 

Those that have done the 987 airbox, with 74mm TB and either IPD or 997 plenum, what were the measured gains from the airbox on it's own? I have the TB and plenum that I will be installing, and trying to decide if the airbox is worth it. Seems a LOT of work to manage the MAF issues as well as tuning (I don't have PIWIS to download a tune on my own) especially if the gains are nominal. Would love to hear some feedback either way.

The dyno graphs I have seen including my own the average increase just for the air box is 5 hp .

I assume that was for your stock engine ??

Have seen the 5 hp change on stock and modified engines.

What MAF setup are these running? My concern is this turns into a never ending rabbit hole for tuning and what not.

If I swap the TB and plenum, but maintain the 986 AB, my understanding is I CAN use the existing mapping and maintain drivability with increased response. I don’t want to get into wide band O2 systems and what not to tune around a new problem with increased MAF diameter that I create.

I would say it may be the best mod to do other than exhaust. Install is not easy it's best to remove driver side intake runners.

I have a video on my YouTube channel where I do this mod. It may be of help.

I contacted VRTuning (VividRacing) and they sent me a MAP file and the hardware to flash it, based on the mods I told them about. They did a pretty good job. It might be just a LITTLE bit rich, but I can attribute some of that to my 3500' elevation. haha

plan on $800-ish for the hardware and flash-file.

As long as you don’t exceed 120% of the original air volume flowing over the MAF, the DME can adapt, no remapping necessary.

A rudimentary volume calculation can be achieved by using the diameter of the original MAF tube vs new and inputting the numbers into the formula for area of a circle. It’s not perfect, but will give you a rough idea. You can then check your fuel ratio to confirm whether or not it has adapted.

Hey Particlewave,
Do you mind if I ask where you get the 120% figure from?
I am always trying to learn more about the capabilities of modern day engine management systems.
Thanks

Don’t recall...I’ll try to find it, but it was reputable. ;)

Check this thread (pg2): http://986forum.com/forums/performance-technical-chat/32074-987-v-986-air-box-2.html

It seems it may be adaptable up to a 25% increase (125% of original). Good info there, but I’ve seen it repeated by other reputable sources or I wouldn’t have committed it to memory. ;)

You’ve built some pretty significant motors for these. Did you use a 986 MAF or the larger diameter 987 one? If it’s worth the additional work for tuning, It seems like a worthwhile mod. Just not sure how to go about it.

Did you follow the link particlewave provided below?

There are many, MANY write ups with excellent instructions on this forum. Hit the search bar, you'll be amazed .

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I've researched this ad nauseum, and have come to the conclusion that there are a number of butt dynos who have registered gains after tuning, but limited info with regard to the larger MAF from a 987 being used. I've read here and seen videos that suggest that additional tuning with either a 996 tune or VRTuning type software is necessary to make the larger MAF work. As I mentioned before, I don't have access to either of those at the moment, and am not convinced the improvements are worth the cost and difficulty to install. Would love to see some hard data that supports it, or get more feedback from someone who has installed the 987 MAF on what the best course is. I can definitely recognize that the 987 AB is an worthwhile improvement as even Porsche used it on the anniversary edition. I need to make a decision as to how I want to invest in the supporting HW/SW to make it work. My thoughts at the moment, suggest using the 987 AB with tubing to allow for the 986 MAF. Unfortunately, a lot of the threads on this subject are older, and folks like The Radium King who've done a lot of research aren't as active. I was hoping to locate some info that would support either method with good dyno info.

As listed in my signature, I have a 987 airfilter housing & MAF that has the the same diameter as a 996. This requires reprograming the DME for the larger diameter MAF. This really woke up my 3.6 liter rebuild. On the test drive the 1st time I floored it The induction noise scared me.

If you have access to dyno graphs could you tell us where in the RPM range the 5 hp gain is?
More importantly what are the torque gains? and where?
Are these gains in the low to mid RPM range? So they would be useable on the street?
Or more on the high end of RPM so more applicable to the track?
Thanks in advance

Thanks
I have read that thread in the past. Ended up re-read the entire thread again.
Don't know if I should thank you for that or not:D Some good experimenting going on there.

Sorry those graphs were over a year ago . I don't remember the specifics but I know the guy's at Jake Raby's shop and they have told me many times they see an honest 5 hp increase from the air box swap .

You can get 5+ bhp without the airbox and just doing a 996 plenum and 74mm throttle body. You'll see the gains from approx 3.5k onwards.

hey man, i can get you dyno results. my rate is $125 per hour and the car is $500 per day. not sure what the actual dyno cost is, but i'll bill you the actual cost plus 10% markup. the clock starts when i leave the house and stops when i am back home. and i live a LONG way from the nearest dyno.

listen, none of us are selling anything. if you want testing then ask a vendor and don't complain about the cost of their product afterwards. instead of asking a bunch of home diyers to spend time and money to prove info that they are sharing out of the goodness of their heart, how about you take the time and spend the money to try out the mod and see if you like it? seems a lot more fair to me. hey, we already did 90% of the work for you at our own expense.

A.
Freaking.
Men.

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No 987 airbox on my first Boxster but here's some mods with Dyno runs
http://986forum.com/forums/performance-technical-chat/47555-tuned-modified-2000-boxster-s.html#post430413

Thanks for sharing that was very interesting. Is the 266 hp at the rear wheels?

I´m "blueprinting" my upcoming breathing mods right now. Plan on 987 airbox, 987 MAF-housing with 986-sensor, 74mm throttle, 997 Plenum and maybe, if I feel lucky I go all the way and swap in the 996 intake. This + the whole exhaust part.

I have read so much on the subject the last week that I´m actually dreaming about it at night ;-)

I still have two issues I haven´t managed to figure out, so if someone would be able to chime in It would be great.
1) I take it the 74mm throttle seems ok, or even the 76, but what about the 82mm? Would it be beneficial or is it just too big for the 3.2? I understand a 82 throttle from a Cayenne V8 would work and be cheaper than a GT3.
2) I take it that the 987 MAF-housing is too big for the ECU to adapt and a flash is needed, I do plan on a custom mapping by a good tuner however how bad is it with the 987 MAF-housing? Will the Engine run? Will I be able to drive to the tuner with the original tune? Or will I need to take the car on a trailer?

I know a number of people have done this mod, but two things that I never see mentioned is the affect on ignition timing and exhaust temps.
To much ignition advance and or to high exhaust temps are not good.
Might be interesting to take some base line readings before the mod. So you can monitor after;)

1) you'll have to decide if the larger tb is giving you a performance increase OR a pseudo-performance increase via what is for all intents and purposes remapped throttle performance. so, think of water; you put a 1/2" faucet on a 1" line and it will be a restriction and limit full flow (it will also increase the water pressure - good for cylinder fill in low-rpm situations). however if you put a 2" faucet on a 1" line then full flow will be achieved when the valve is only partially open - no extra power, but full throttle comes on sooner - pseudo-performance increase. i think the 74mm tb brings some top-end power by removing a restriction (to the detriment of low RPM torque) but the 82mm might be too big for any gains just losses.

2) talk w newart; iirc he ran with the larger maf housing prior to pushing the flash on his car and trims slowly increased until he got a cel. realize that more air is moving than the computer can allow for so you will get into a lean condition which is not good in the long term. fine for the drive to the tuner however.

Thanks TRK, great answers.


Thinking of how to manipulate the sensor value to simulate the smaller MAF-housing.. On the other hand, if I can "limp" to the tuner, that will be good enough.

you might be able to put a variable resistor in line with the maf. there was a great video on youtube where some folks did it w a 996. that's pretty much all that a piggyback computer does; use feedback from a wideband o2 to modify the maf readings that the main ecu sees. you can do the same manually.

https://apexi-usa.com/electronics/afc-neo-fuel-management

TRK-Thanks for jumping in and offering insight. I’m thinking at this point since I don’t have readily available access to a tuner and mapping capability, I’m going to find the BMW housing that will match the 986 diameter (I believe was mentioned as an E39 535i). Once I have the ability to either upload the 996 tune or get my car mapped to match, I can change to the larger housing and tubes from siliconeintake.

TRK-would you be willing to share the correct models for the appropriate housings?

i think that info is in the other long intake plenum thread. i got it from *i think* insite who is not around much anymore (who also had some interesting experiences w an apexi unit). i have one in my garage and can pull the part # in the next few days. iirc it wasn't an exact match ID but closer than the 987 unit. also can't recall if it mated to the airbox; still required cutting - i can confirm that as well. kram has a good thread on adapting the 986 housing to the 987 airbox, or i still have mine sitting around someplace that i don't really need anymore.

ok, finally got into my garage.

oem unit (sawn off the airbox) is 75 mm ID.

BMW unit is part # 0280217502 and is 72 mm ID. and, while it has a similar style of mating flange as the 987 airbox, it is smaller so an adaptor would be reqd regardless.

Sorry for my lack of respons, I really appreciate the answers on my question though.
Still haven´t decided on how to proceed with the MAF..

If I´m not totally wrong: People seem to be happy with the 74mm throttle (also IPD is designed to fit with 74), the OEM MAF for the 986s has an inside diameter of 76mm so are there really any reason to go bigger on the MAF? Using a bigger MAF that will need some sort of recalibration will add complexity and I´m afraid it will increase the cost for my tuner. (it´s expensive enough anyway)

Then I look at the Anniversary model, as we all know it runs on a 987 airbox, I just realised that is also uses the 98760612500 MAF. Could that be an option? If I just use the 98760612500, will I then not need to recalibrate the ECU for the oversized MAF?

Sorry for all the questions, I´m such an amateur :D

The MAF is closer to the throttle body on the Anniversary.

986 and 987 maf are the same; 987 unit comes w the holder is only difference (holder detachable in 987, fixed to the airbox in 986). 987 holder is larger diameter than 986; 986ae used special tune. sorry if i missed it - what year is your car?

also, as you note, the original maf holder and new tb will be same ID so good there; thing is that the tubing you are using to join the two units fits to the OD which is 1/4" or so larger (the thick lip on the tb is 1/8" or so) so that the air compresses from airbox to maf holder, then expands, then compresses at tb again - wasted work. also, a decreasing radius intake system (ie, airbox larger than maf holder larger than throttle body) will tend to accelerate the intake airflow and facilitate cylinder fill for low rpm torque. small gains overall, and not worth the work of modifying the programming on your car when you can just use the original maf housing. i did it for (a) oem look, and (b) i have a pst2 and wanted to run a 996 tune on my car.

Thanks boys, maybe I´m starting to understand.. So, my car is the 2003s ROW as I understand it it should as standard be sporting a 986.606.125.01 MAF-sensor attached to the narrower housing. The 987.606.125.00 would then be the larger housing complete with a 986.606.125.01 sensor inside.. Did I get that correct?

So do I want the larger or the narrower MAF housing..
I believe that I should strive for a air-path with a smooth but slightly decreasing diameter all the way from the airbox to the plenum. Thus I take it that the larger MAF is the way to go, just ensure that the piping gives a good decrease in diameter downstream, and since I will be using a custom tune I guess the cost won´t be too overwhelming just for the MAF-tune part.

Please enlighten me if I still got it wrong!!!


Some more thoughts.. I am starting to believe that the theoretical dimensioning to strive for should be:
1) Go from wide to narrower in the airbox, MAF, Throttle body, to accelerate air and give good cylinder fill at lower rpm (as stated by TRK). By keeping the whole chain larger than oem, it will still give more flow at WOT, thus more power.
2) Here comes the strange part.. I believe I have read somewhere that the plenum, or (maybe the chamber between the plenum and the intake runners) should be basically as large as possible, to act as a "air-reservoar" with enough air to provide the runners with enough air. (Have I got this 100% wrong???)
3) Then the runners.. I guess the runners must me "wide enough" but not least quite long.. The length to achieve some momentum in the air (more air mass accumulated) to provide cylinder fill at lower rpm:s, thus the 996 intake / runners are preferred.

All in all I´m sure I got at least some part of the above bullets 1-3 wrong. Let´s discuss! :dance:

sure. you are lucky - your car is a 2003 so the anniversary edition tune will work on it. for a mechanic with a pst2 that knows what he is doing it is a 5 minute job to push the new tune onto your car. you would need the dme programming code for your car but any dealer should be able to provide that. otherwise a custom tune or run w the original maf holder. at a minimum, you can run with the original holder until you can get the new tune. for the cost of a custom tune i'll fly to sweden with my pst2 and tune your car for you (actually, i will be in france in april, perhaps i can do a side trip ...).

1) i think you have this correct.
2) i am not sure about this, but that's my thesis. given that the intake runners (the six legs that descend to each intake valve) should also be of decreasing diameter to accelerate air into the cylinder (look at any car design, even the venturi intake tubes on old itb cars). however, if the air acceleration is happening in the intake runners, what is the need to accelerate air into the intake plenum? i'm not sure, so my intake does both.
3) longer runners mean more acceleration, but also more air resistance (work). so, short fat runners are good for hp (less resistance) while longer ones are good for torque (better cylinder fill). 986 is short and fat, while 996 are longer. unsure why the difference; perhaps engine bay packaging, perhaps efforts to limit performance of the 986 vs 996. nova has 996 runners on his car and swears his 3.2 pulls as hard as his 3.4 with all the above modifications. remember, porsche limited the 986 vs the 996 to avoid one stepping on the other; given heads and internals are the same (only displacement differs, but differences in hp/litre ratios between the two engines indicate more than a difference in displacement is at work) so porsche could only limit the 986 w exhaust, intake, and tuning.

Good input, I agree about the runners, they also are of decreasing diameter, and what would the point be to accelerate air in two stages just to have it "consolidated" before the runners, this is over my competence level. However, this design cannot hurt, so it´s my plan. I plan ta take the car to a specific shop for a custom tune on the dyno, however let´s see how things turn out, the idea of you popping by Sweden is a good one, let´s follow up on that one later on! :cheers:

So I'm moments shy of buying a PST2 for this same purpose.
I understand from other threads that I'll need a 996 VIN and associated password, in order to load that 986 flash to my 986 DME. (Correct?)
In anticipation of this, I called my dealer today to see what it'd take to get them to help me with that VIN and password. No joy. They basically mocked me, that I'd think they'd just hand that out. They're kinda dicks over there.

So, question: some of y'all who've done this (TRK?) Do you have a VIN and associated pass code you can share? And if not, do you know a dealer who is supportive of this, who I could contact?

I'd sure like to know I've got a clear pathway before I pull the trigger on the PST2.

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