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Old 07-05-2014, 06:13 PM   #1
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2.5 Intake upgrade

I've been told that if you swap out the intake on an early Boxster, 2.5, with a 3.4 intake you'll pick up as much as 25hp. I guess they had "choked down" the original 2.5s because the performance was better than the 911 of the day. Anyway, can anyone confirm an intake off of a 3.4 911 will bolt and work on a 98 2.5L ? Thanks

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Old 07-05-2014, 08:58 PM   #2
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Originally Posted by RayW View Post
I've been told that if you swap out the intake on an early Boxster, 2.5, with a 3.4 intake you'll pick up as much as 25hp. I guess they had "choked down" the original 2.5s because the performance was better than the 911 of the day. Anyway, can anyone confirm an intake off of a 3.4 911 will bolt and work on a 98 2.5L ? Thanks
Hehe absolutely not. I have yet to see a well documented performance improvement by just changing the intake alone on a 2.5l. If you tune it exactly right you might pick up 1-2hp above 6krpm while giving up valuable TQ at 4k rpm.
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Old 07-06-2014, 02:50 AM   #3
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Here is the absolute truth. The 987 intake will fit in and do a better job. You will have to have the car retuned due to the change in position of the mass air sensor. On a 2.5 motor I wouldn't bother changing it out. The stock is perfectly fine and THE best cold air intake out there. Keep a clean stock air filter and do not de-snork the car. Take my advice or not. Others will argue intake options, most of them with no dyno time or afr knowledge.
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Old 07-06-2014, 11:29 AM   #4
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Thanks for the advise guys. I'm new to the Porsche experience, so I'm learning as I go. This forum is a good place to talk through ideas. Trial and error is a little more costly for a Porsche........
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Old 07-06-2014, 02:05 PM   #5
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do not de-snork the car.
Just wondering what the down-side of de-snorking is? (or should it be de-snorkification?)
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Old 07-08-2014, 06:29 AM   #6
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i have a 1999 2.5 and i made some mods to the intake, and although i didnt dyno test it, i have no doubt that it made an improvement.
I got an evoms cold air intake, had a bigger aluminium intake pipe fitted, got an ipd plenum and finally i bored out the throttle body and had a bigger butterfly valve fitted to it.
all this together with a remap DEFINATELY made a difference in throttle response, not to say that the car sounds like a different beast now.
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Old 07-08-2014, 06:55 AM   #7
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To put it simply, without a before and after dyno, there is no way to know if the change added any power.

That is why I dyno tested my new exhaust and if you look at the data, you'll see that the hp increase is very small (7hp) and ONLY at certain RPM's (only above 5800 rpm). This info was different than what some people were reporting based on the good ol' butt dyno. I'm not saying that the butt dyno doesn't work, just saying that it is somewhat subjective.

http://986forum.com/forums/general-discussions/51783-top-speed-pro-1-catback-exhaust-hp-increase.html

Soon, I will also be posting a before and after dyno test of my old 136,000 mile engine and my completely rebuilt engine so we can see what, if any, difference there is in power between an old tired motor and a new rebuild.

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Last edited by thstone; 07-08-2014 at 06:59 AM.
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