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Old 10-12-2014, 10:40 PM   #1
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987 airbox on a 2.5 worth it or not

Looking to replace my aftermarket intake with the standard airbox, is it worth looking for a 987 airbox or is the standard 986 one fine for the 2.5 motor.
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Old 10-13-2014, 10:24 AM   #2
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Looking to replace my aftermarket intake with the standard airbox, is it worth looking for a 987 airbox or is the standard 986 one fine for the 2.5 motor.
i would think the only way to know for sure is if you run some tests / dyno runs with vacum transducers strategically placed in the air box. I think the car would have to be moving (to get the effect of air pressure into the air box). If you are seeing vacum everywhere a bigger air box may help, but you must consider your goals. Throttle response maybe way more useful to you than peak hp.

My gut feeling is that the the air box is just fine for the 2.5, on the edge for the 2.7 and perhaps too small for the 3.2. I have not come across anyone that has worked with a 987 on a 2.5....perhaps others can chime in with their thoughts

You will also loose the helmholtz chamber if you go 987
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Old 10-13-2014, 10:33 PM   #3
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yes that was my thinking with it being fine for the 2.5, i'm trying to solve a flat spot ive got at 5400 rpm.
When i disconnected the MAF the flat spot had gone, the MAF's ok as after the flat spot it pulls hard again to the redline
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Old 10-15-2014, 05:41 AM   #4
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ipd plenum will fix your flatspot
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Old 10-15-2014, 06:00 AM   #5
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there's a cheap softronic plenum fs on planet 9 right now ...

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Old 10-15-2014, 08:54 AM   #6
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Quote:
Originally Posted by whitecliffs View Post
yes that was my thinking with it being fine for the 2.5, i'm trying to solve a flat spot ive got at 5400 rpm.
When i disconnected the MAF the flat spot had gone, the MAF's ok as after the flat spot it pulls hard again to the redline
Still sounds like a fouled MAF. I had a similar problem with a flat spot and no error codes yet. I cleaned the MAF and it improved for a while but came back over time with codes. Replacing the MAF was the cure.

I suspect the 987 airbox on a 2.5L may improve performance slightly above 6krpm but may sacrifice some torque in the 4-6k range. A tradeoff worth taking??? Depends on your goals I guess.
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Old 10-15-2014, 09:38 AM   #7
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You realize the 987 air box probably can't be installed without removing the motor. At the very least you will have to take out half the intake manifold. Next the MAF tube is significantly larger than the 986 I believe it is 90MM. Without some programing your air fuel mix will probably be off.
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Old 10-15-2014, 10:32 AM   #8
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ipd plenum will fix your flatspot
I already have a pedro techno torque fitted

[QUOTE=Topless;421741]Still sounds like a fouled MAF. I had a similar problem with a flat spot and no error codes yet. I cleaned the MAF and it improved for a while but came back over time with codes. Replacing the MAF was the cure.

The MAF is only a month old and a genuine Bosch one, if the MAF was faulty wouldn't it show up in other areas and not just at 5400rpm because once passed 5600 it pull clean and hard again everytime
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Old 10-15-2014, 11:47 AM   #9
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[QUOTE=whitecliffs;421750]I already have a pedro techno torque fitted

Quote:
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Still sounds like a fouled MAF. I had a similar problem with a flat spot and no error codes yet. I cleaned the MAF and it improved for a while but came back over time with codes. Replacing the MAF was the cure.

The MAF is only a month old and a genuine Bosch one, if the MAF was faulty wouldn't it show up in other areas and not just at 5400rpm because once passed 5600 it pull clean and hard again everytime
If it is brand new Bosch and clean it is probably ok. A flat spot in the rpm range while running fine everywhere else is a common symptom of a failing MAF. It rarely affects the entire upper range unless it is completely fouled.
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Old 10-19-2014, 12:05 PM   #10
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Installed the standard airbox this weekend and the flat spot as gone, so looks like it was my after market air filter it didn't like
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Old 10-19-2014, 12:34 PM   #11
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aftermarket air filters are typically oiled - the oil fouls the maf. happened to me more than once, hence now an advocate for the 987 airbox conversion over any aftermarket filters or intakes.
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