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Old 12-20-2017, 03:28 PM   #1
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986 vs 987 MAF tube

Sorry to start a new thread, but the 986 vs 987 air box thread is getting a bit leggy at 15 pages!
987 v 986 Air box
My question here really concerns the MAF tube and the MAF itself. So far, I've picked up a 74mm TB and have a line on either a 987 air box with, or another 987 air box without the 987 MAF tube. The difference in price is not that great but the question is: is it preferable to install the 987 tube and MAF which, I presume, would require a tune or jerry-rig the 986 tube with it's inherent restrictions (no tune required) into the line?

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Old 12-20-2017, 04:45 PM   #2
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Originally Posted by NewArt View Post
Sorry to start a new thread, but the 986 vs 987 air box thread is getting a bit leggy at 15 pages!
987 v 986 Air box
My question here really concerns the MAF tube and the MAF itself. So far, I've picked up a 74mm TB and have a line on either a 987 air box with, or another 987 air box without the 987 MAF tube. The difference in price is not that great but the question is: is it preferable to install the 987 tube and MAF which, I presume, would require a tune or jerry-rig the 986 tube with it's inherent restrictions (no tune required) into the line?
If you install a larger diameter MAF housing/ tube the "tune" will have to take the resulting greater airflow into consideration to prevent running too lean. The 2004 special edition program should be good & least expensive.
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Last edited by BYprodriver; 12-20-2017 at 04:47 PM.
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Old 12-20-2017, 06:06 PM   #3
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Yes, I was thinking of that. Doesn’t the SE MAF tube have a step down to use the 986 TB? That is, do you know if the SE uses the 987 MAF?
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2004 986 S
987 air intake TB and plenum, Mantissport 2 litre sump, UDP, Bilstein B6 with H&R lowering spings, re71-rs for track, other stuff.
https://www.youtube.com/user/12shoes2
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Old 12-21-2017, 12:37 PM   #4
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I have performed this mod in the last weeks. I had planned on using the 987 MAF tube and getting a tune from either a local tuner or Evo motorsports. My car is a 2001 S with the 7.2 DME. Both tuners said they can't make the 987 MAF tube in the 7.2 DME work as the map table size in bytes is larger for the 987 7.8 dme and they can't compress the map to work properly in the byte size table allotment in the 7.2. Enlarging the byte size map would change other addresses and cascades into an mess.

I cut the 986 MAF tube off and grafted it onto the 987 tube like in the thread. The id of the 986 MAF tube is still larger than the 997 Throttle Body. You just need to install larger hoses as the 986 hose restricts it even more.

If you have 2003-2004 with the 7.8 dme then the 987 tube can work.


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Old 12-21-2017, 01:09 PM   #5
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Yes, I have the 2004 Boxster S with the 7.8 DME. It would be nice if I could use the larger MAF tube. Would the tune be for the 986 anniversary edition or the 987, or another?
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2004 986 S
987 air intake TB and plenum, Mantissport 2 litre sump, UDP, Bilstein B6 with H&R lowering spings, re71-rs for track, other stuff.
https://www.youtube.com/user/12shoes2
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Old 12-21-2017, 07:58 PM   #6
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Originally Posted by P_Carfahrer View Post
I have performed this mod in the last weeks. I had planned on using the 987 MAF tube and getting a tune from either a local tuner or Evo motorsports. My car is a 2001 S with the 7.2 DME. Both tuners said they can't make the 987 MAF tube in the 7.2 DME work as the map table size in bytes is larger for the 987 7.8 dme and they can't compress the map to work properly in the byte size table allotment in the 7.2. Enlarging the byte size map would change other addresses and cascades into an mess.

I cut the 986 MAF tube off and grafted it onto the 987 tube like in the thread. The id of the 986 MAF tube is still larger than the 997 Throttle Body. You just need to install larger hoses as the 986 hose restricts it even more.

If you have 2003-2004 with the 7.8 dme then the 987 tube can work.


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you can use a 996 tune on your car if you want to keep the larger maf tube.
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Old 12-22-2017, 05:52 AM   #7
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you can use a 996 tune on your car if you want to keep the larger maf tube.
Cool, thanks for the information!
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987 air intake TB and plenum, Mantissport 2 litre sump, UDP, Bilstein B6 with H&R lowering spings, re71-rs for track, other stuff.
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Old 12-22-2017, 06:11 AM   #8
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I thought that the 987 MAF tube was 3.25" diameter, against 3.5" for the 996?

Or do the 3.4 987's use a 3.5" MAF?
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Old 12-22-2017, 09:07 AM   #9
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Cool, thanks for the information!
here is more specific info ...

a number of variables - year, displacement, variocam. porsche moved the 996 from the 7.2 to 7.8 dme in 2002, but didn’t move the boxster until 2003. unfortunately, porsche also put the variocam+ system into the 996 at the same time, whereas it didn’t introduce it into the boxster until 2008 (the box kept the standard variocam timing). so, a 2003 or 2004 can’t run a 996 tune. fortunately (and pls verify, as i have no direct experience) the 2004 Special Edition anniversary edition boxster runs the 987 airbox and maf housing on the same engine as a standard 2003/04, so that is the tune i would use in that case. if you have a 99 or earlier i am not sure how well the 3.4 tune would work on a 2.5 (ditto and 2.7 or 2.9). a 996 tune to 01 works great on my 2000 S, and should work no problem on a 2001. if you have a 2002 you should be ok with an earlier 996 tune as well.
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Old 12-22-2017, 09:12 AM   #10
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Originally Posted by witko999 View Post
I thought that the 987 MAF tube was 3.25" diameter, against 3.5" for the 996?

Or do the 3.4 987's use a 3.5" MAF?
987 and 996 are same ID. i’ve been running 987 airbox, 987 maf and tube, 997 plenum and cayman tb (or 996? can't remember) for several years now no problem. using a 996 tune and monitoring trims. low load trims have been perfect, and idle trims a bit higher but still well within spec.

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Old 12-22-2017, 10:00 AM   #11
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here are last years trim readings with all the mods including the 996 tune ...

date FRA (load 0.7 to 1.32) RKAT (idle +/- 4%)
21-May-17 1.00, 1.01 1.92%, 1.35%
22-May-17 1.05, 1.06 1.96%, 1.64%
17-Jun-17 1.04, 1.05 1.78%, 1.40%
21-Jul-17 1.05, 1.07 2.48%, 1.82%

these are all after hard workouts at the track, so real long-term trims.

so, as you would expect, load trims are fine. While the 996 tune is designed for a bigger engine, it is still just a matter of look up airflow at the maf, and check a table to confirm appropriate amount of fuel for airflow - displacement doesn't matter. idle is different, so the ecu will have to trim it a bit more to work with the 3.2 but, as you can see, still within tolerance. my concern with the 996 tune was that the load triggers for the switch to open loop would be off - rpm, engine temp, throttle position - however all seems good and engine working like a top. in fact, seems to be better than before (no dyno or anything) which seems to indicate to me that porsche neutered the 986 with the tune as well. finally, since low load trims are so good, i am confident that the open loop fueling is fine (open loop is un monitored - our cars only have narrow-band o2 sensors so can't monitor high load operation when the dme is adding additional fuel for cooling purposes).

putting a 996 tune on a 986 is no big deal - anyone with a pst2 or piwis can do it in about 5 mins - the tools come preprogrammed with all the 9x6 tunes and variations (ROW, NA, various changes for various years, etc.). great chance to get a row tune at the same time (delete cats/sensors and smog pump with no cel). what you will need is your dme programming code - available from porsche if you can find a willing dealer to give it to you (mine cost me $50). after you have the 996 tune on, realise that your car will read as a 996 or a 986 depending on what system you want to look at with your pst2/piwis/durametric.
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Old 12-22-2017, 10:09 AM   #12
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putting a 996 tune on a 986 is no big deal - anyone with a pst2 or piwis can do it in about 5 mins - the tools come preprogrammed with all the 9x6 tunes and variations (ROW, NA, various changes for various years, etc.). great chance to get a row tune at the same time (delete cats/sensors and smog pump with no cel). what you will need is your dme programming code - available from porsche if you can find a willing dealer to give it to you (mine cost me $50). after you have the 996 tune on, realise that your car will read as a 996 or a 986 depending on what system you want to look at with your pst2/piwis/durametric.
fwiw, i could find no one in my area who was able or willing to do this. so I ended up with a massively overpriced junky softronic tune.
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Old 12-22-2017, 10:19 AM   #13
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fwiw, i could find no one in my area who was able or willing to do this. so I ended up with a massively overpriced junky softronic tune.
well, i have the benfit of having my own pst2 - bosch pcmcia card and cable in a fragile old 1990's laptop that i have to keep operational using spare parts from similar laptops bought on ebay because i have no idea where to find the proper software to load onto a newer machine. and i have the benefit of getting the instructions on how to do it from todd holyoak, the king of 986 engine swaps. i can get the instructions to anyone who is interested, but ultimately it is just a matter of hooking the tool up to your car, logging in as a 996 (you'll get lots of complaints as the car is not a 996, but this is required otherwise the tool will only offer you 986 flash options) then go into dme programming, enter your dme programming code, chose the flash you want, follow instructions, done.
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Old 12-22-2017, 03:24 PM   #14
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Yes, I have the 2004 Boxster S with the 7.8 DME. It would be nice if I could use the larger MAF tube. Would the tune be for the 986 anniversary edition or the 987, or another?
I believe the 2004 986 anniversary program would be best for that application.
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Old 12-22-2017, 04:01 PM   #15
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I believe the 2004 986 anniversary program would be best for that application.
What he said!! The SE has the 987 MAF tube senor and air box. Same parts.
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Old 12-22-2017, 05:38 PM   #16
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Super! Exactly the info I was hoping for!
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987 air intake TB and plenum, Mantissport 2 litre sump, UDP, Bilstein B6 with H&R lowering spings, re71-rs for track, other stuff.
https://www.youtube.com/user/12shoes2
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Old 12-22-2017, 06:52 PM   #17
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Hey radium, any chance you're in Edmonton? The dealer we got doesn't do anything beyond what came out of the factory.
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Old 12-22-2017, 07:28 PM   #18
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Hey radium, any chance you're in Edmonton? The dealer we got doesn't do anything beyond what came out of the factory.
fort smith, nt. i'm in edmonton lots though, esp in the summer. pm me if you need any help.

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