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Old 03-01-2013, 07:29 PM   #1
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Typical MPG for a Boxster 03 2.7L

I'm new to the Porsche Brand, but itching to try my next mod.

My first mod consisted of a "simple to install" bolt-on plenum that replaces the original stock plenum by Peak Aire Performance, which has yielded 36 to 37 MPG highway driving ( see pic ) & 20 to 23 MPG city.

Not sure if these MPG ratings are good or bad, however the original sticker price label when the car was sold read - 20 City 29 Highway - Comments Welcomed!

Question:

Has anyone successfully increased the size of the stock TB & Intake Plenum from 68mm to 74mm?

I would like to combine the increased performance from the first mod with a larger plenum & TB from a different Porsche model.

Does anyone have the recipe for this "DIY" cocktail?
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Old 03-01-2013, 07:52 PM   #2
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Here is some reading material that will keep you up all night.

http://986forum.com/forums/general-discussions/31693-maf-throttle-body-diameter.html
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Old 03-02-2013, 08:29 AM   #3
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who cares about MPG for these cars ???
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Old 03-02-2013, 10:54 AM   #4
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MPG for Boxster 2.7L????

Meir,

I curse you and the Boxster you drove in on!!!

I was up all night analyzing the entire thread... but over half of that content was somewhat dated... what was the outcome... did you actually do the upgrade.

Have we heard back from any of those participants of that thread?

The results would be very useful testing/modeling that the entire Boxster Community can benefit from.

Also... please comment on MPG for your 2001. Since my plenum upgrade, I'm getting fantastic MGP both CITY 23 & especially HWY 37. FYI - my findings are based on Porsche's on board computer via steering column.

Thanks for all your support & input!
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Old 03-04-2013, 07:06 AM   #5
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Hi @ Speedster986,

Welcome to the group! Careful about "Scratching that itch" on this mod. MPG on this car is a tough nut to crack.

I dare say your computer has a 'glitch' in it. It seems to be almost impossible to get mileage that good.

Best I have been able to achieve is around 26-28 MPG BUT, having said that, I DO NOT drive anywhere near conservative. If you have this car you are obligated to drive it accordingly. In order to get mileage that high you must be unde-revving it. My wife borrowed my car and got over 30 MPG (per manual calculations) but I found out she was DOGGING it!

Doctor's orders are: Upshift UNDER 3k until warm…then NO LESS than 3k on upshifts after that. You may cruise at less than 3k, but IT IS a sports car and I think that widening the TB or intake WILL ALLOW more air and gas mix in - using more, not less gas.

I have a 4" intake on my car and IT HAS GOBS more power but not much better gas mileage.

Most people here would agree the POWER is more important than MILEAGE but opinions vary so you are welcome to try. Keep us posted!
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Old 03-05-2013, 10:03 PM   #6
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Homeboy-

First of all, I must say that ALL members of this forum site are absolutely awesome!
The wealth of knowledge shared on this website is truly... priceless.

As for my driving behavior as of late, frankly I'm surprised I haven't been arrested.
My Boxster has become my daily driver due to obvious reasons, however since the plenum upgrade (4 mos. ago) it seems like I'm driving a different car. Now it's much faster, shifts smoother, pulls harder to red-line etc. Typically I try to keep my RPM indicator 'straight up' most of the time and shift around 4500 (cruising) & 5800+ (show-off mode).

Next week I'll begin opening up the AIR INTAKE side of the engine to allow it to breath easier. I realize the trade off HP vs. gas efficiency, but hey... I'm already ahead due to the increase mileage experienced from my plenum upgrade.

Currently I'm in the process of patenting the plenum's performance enhancing design. I can tell you that my plenum upgrade will require fewer parts than what is being offered today and will be sold at a fraction of the cost!

More HP + Fuel Efficiency = Win Win!!!
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Old 03-06-2013, 05:18 PM   #7
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If I can manage to keep my foot out of it I get about 27 hwy. that's boring though Go Play and have fun with your car. It's not a prius thank god....
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