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Old 04-03-2014, 08:28 AM   #1
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Closing the S gap for a 2.5...tall order

I'm fully aware I'm barking up the wrong tree with my 2.5 box but I'm so invested in it now it's too late to change horses. Now that I'm classed in my local autoX with the S boxes I'm interested in bumping up the power to close as much of the power gap as I can. Just how much power can you get out of the 2.5l with bolt on upgrades.

I'd love to find a dyno run with the following
-no cats (which I've done)
-headers(which I have)
-exhaust(which I have)
-underdrive pulley
-pedo's power pack claiming 25+hp
-intake
-chip
-regulator
-something I'm forgetting.


Right now I'm guessing I've added 11hp, and removed 140lbs. With the 3.2 S added curb weight I'll need 18 additional HP to completely close the hp/lb gap
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Old 04-03-2014, 11:07 AM   #2
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Good luck, and I don't mean that in a snarky smart-ass way. Porsche really did a good job of wringing a lot of power out of the little 2.5. Chevys & Fords used to be impressive when they got 1HP per cubic inch. The 2.5 is 200HP for about 150 cubes. That kind of ratio in a chevy 350 produces an unstreetable beast.
You might begin by dynoing your car. Performance Autosport is pretty close to you. For reference, on their dyno my car showed 244 RWHP.
The underdrive pulley is about the most bang-per-$$
After that, get some lighter wheels and Hoosier A6 tires. That will make you a lot more competitive, hands down.
Another thought is to lose weight, but you'd have to be careful in order to stay in BSP. Some things like pulling the carpet and going with a carbon or FG hood bump you to F Prepared. I do think you can ditch the AC and swap the seats for race shells.
Sorry for the ramble...waiting in an airport.
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Old 04-03-2014, 11:19 AM   #3
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244rwhp! Wow! I need a 911...or maybe anything besides a 2.5. Ultimately I'm not too concerned I have a long way too go on skill first. Do you ever make it out to the Vmsc or tidewater autocrosses?
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Old 04-03-2014, 11:49 AM   #4
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You need to stop focusing on chasing a boxster S and look at your competition... The boxster S isnt the fastest car there. How are your times against the FRZs/BRZs? They have similar horsepower to your Boxster, if you arent anywhere close work on chassis, tires, and seat time because it = DRIVING ABILITY. Go to all the events and schools you possibly can.

J.Fro has it right, although I'd add Ksport coilovers. Dont skimp on size either, you can easily squeeze a 9" wheel on 275s up front and a 10" wheel with 295s in the rear.
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Old 04-03-2014, 12:04 PM   #5
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Couldn't agree more, I was more curious than anything else. I beat out the 911s, boxsters and caymans last weekend including a brand spanking new cayman. Like you said its skill over power for sure. It was also wet so they're power didn't help them much. I've got my eyes on the ksports, seems to good to be true. Oddly enough we dont have any BRZs in our club.
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Old 04-03-2014, 12:32 PM   #6
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ditto weight - lw seats (rottec if you don't need fia approval) a/c delete, roof transmission and motor delete (roof works just fine in manual mode). perhaps stereo delete. if no emissions testing then secondary air and carbon canister (a row flash will get rid of any cels that may arise). oz wheels from tire rack are the best $/lb deal out there.

for more power, smallest udp is 4" - make sure you don't have the 5" that is also available. you've done exhaust. 987 air box (and trim the air filter hanger to improve airflow - good for a few more hp according to planet 9). pedro sells the intake plenum/larger throttle body/dme flash as listed (get a hard limiter if possible). after that, get a wideband afr gauge and trim your open loop afr a little closer to stoichiometric. see if you can bolt an intake manifold for a 3.2 onto your car - might give a bit more top end oomph.

all should look relatively stock and keep you in your class.
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Old 04-03-2014, 01:01 PM   #7
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removing carpet behind&under seat, engine carpet, and compartment behind the seat will reduce about 33 lb.
Carpets and wood panel @ trunk 13,6 lb
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Old 04-03-2014, 01:37 PM   #8
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Sure, removing weight greatly increases handling.

Is your car a dual purpose car? Or a track car only? Is it worth it sacrificing all the sound deadening, radio, carpets, AC, automatic convertible top function and door panels to lighten the car up 100lbs? Not if you drive on the street...

Keep that in mind when you go removing the carpets. I totally stripped my 944 turbo to build a track car out of it. Long story short, I ended up spending a lot of time and money putting the interior back together.

Dont destroy your car for autoX, just slap on some slicks, suspension, and a few more bolt ons and youll be very fast around the course.
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Old 04-03-2014, 01:46 PM   #9
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So far, my Boxster S is a lot faster than I am. I lust after more, but I can't fully use what I already have.

Until you hit a plateau, I'd say spend the money on more autocross entry fees (e,g, look into SCCA) and use the practice to get faster first.
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Old 04-03-2014, 08:07 PM   #10
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Talent, tires and weight are 95% of the game in AX. If you do nothing else, take all the weight out of the car you can. HP brings increases in acceleration only. Weight removal improves acceleration, braking, and cornering speeds.

A lot of drivers spend cubic $$ chasing a few hp when reducing 50lbs results in the same lap times and it is free. Sticky tires however are not free.
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Old 04-04-2014, 04:51 AM   #11
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It is a duel purpose car so I dot want to go to extreme. Right now I'm Ventus RS3s which are worlds better than the summer tires I've run in the past but I'm going to make the jump to slicks soon. I can't remember the name of the site but I know a few guys that buy Hoosiers and continental slicks used from them and have had great luck. They charge about 100/tire. I need to figure out what size I can get away with and what wheels to put them on first. As far as weight goes, I wonder how tough it is to remove the top for an autocross? Mine is already converted to a manual top. I've also already installed gt3 seats so I have that weight reduction checked. I've said it before on here but buying those fake gt3 seats was the best 1,000 I've ever spent.
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Old 04-04-2014, 06:02 AM   #12
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Quote:
Originally Posted by Topless View Post
Talent, tires and weight are 95% of the game in AX. If you do nothing else, take all the weight out of the car you can. HP brings increases in acceleration only. Weight removal improves acceleration, braking, and cornering speeds.

A lot of drivers spend cubic $$ chasing a few hp when reducing 50lbs results in the same lap times and it is free. Sticky tires however are not free.
True, I can afford to lose more than a few pounds myself. Ive been dieting hoping to get faster this year
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Old 04-10-2014, 08:04 PM   #13
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Competition at this level is all about driver skill and driver skill is all about seat time. Practice, practice, practice. That is why guys like Topless and I (and most other drivers near or at the top of their class) do 25+ days per year.

Spend all of your money going to events and while you're there, get an instructor to ride along with you. When you're good, then continue going to events and pay for a professional instructor. When you're really good, THEN upgrade the car.

Invest in yourself to close the gap. Really good driving skills are worth more than the 18hp that you're chasing.
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Old 04-11-2014, 06:12 AM   #14
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Very true, I remember my first year autoXing, an instructor asked to co-drive. While I was wondering what upgrades I should do next, he set the fastest time in the class ( 7 secs faster than me ) and wasnt that far off from the fastest time of the day. He was a monster driver...

So I have to agree with seat time being a lot more effective than bastardizing the interior of your car to save a few pounds...
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Old 04-11-2014, 06:25 AM   #15
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To close the gap you need torque and throttle response much more than horsepower.
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