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Old 11-24-2002, 07:00 PM   #1
Tattoo Collector
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Member#: 19364
Join Date: May 2002
Location: Pennsylvania
Vehicle:
1998 Impreza RS
Black Mica Pearl

Default Overbored/polished throttle body

As most of you probably know, I am building my 11:1 N/A 2.5 RS. I was wondering what the benefits of the overbored or polished throttle body might be with these mods:

-J & E custom 11:1 forged pistons, wrist pins, rings
-MRT full exhaust
-port and polished heads
-valve job (2 angle on valve, 3 angles in the heads)
-Fidanza Flywheel
-Vitek Stage 4 Clutch (4 Puck, sprung disc, carbon)
-Underdrive pulleys
-Cobb CAI (whenever those guys finally finish developing it)

-Also, is there anything I am missing? I want to do this right. I can't afford cams right now. I think when I can I am going to pull off the heads and use those cad? cams [they make the cams for the Honda F1 racecar, supposedly giving 16 WHP(i think that's the company's name)] and install higher spring rate valve springs. When i do that, I will finally go to a stand alone engine management system.
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Old 11-25-2002, 10:38 AM   #2
dcoty
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Location: montreal quebec
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01 V7 GC/R32 sky

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Hey,

I'm pretty far along the way you want to go, I would like to get a set of J&E pistons rods etc, they are a good company from my brothers experience.

Ive done my heads, cams, springs (need them for the higher redline you'll need). I diddnt go with fidanza, i went with a lightend stock flywheel @14lbs. I also have the other n/a mods that you are getting. All thats left is pistons and lightend crank.

I really think you should save up until you can do all of the internals at the same time, lke the cams becuase you dont want to have to pay to have your engine opened again just for your cams (unless you are doing it yourself).

You have a nice list of mods, and the overbored throttle body would be a great addition, that is one thing I have to do to my car aswell. Good Luck with your project!

Dan

PS: My car is in the last day of Unichip tuning and it will finally be finished. They said it sounds very neat at 7,500 rpm...
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Old 11-25-2002, 10:57 AM   #3
Tattoo Collector
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1998 Impreza RS
Black Mica Pearl

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Thanks for the encouragement. I can't spend the money on the cams, plus the ones that I want will throw a CEL, so I can't get them until I can afford a stand alone ECU. I am doing all the work myself and I have a fairly big garage that I keep my antique car and subaru (for now) in. I have no problem pulling the heads off again, maybe in the summer when I am not driving the car. As far as the other stuff, what crank do you have, I am balancing the extra one I have if you are interested.

By the way. J & E is definitely an awesome company. I got the custom pistons, rings and wrist pins for $650 from Eric at Airborne Motorsports. He is an awesome guy to deal with. Great service!
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Old 11-25-2002, 11:50 AM   #4
dcoty
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I might get a set of pistons too, this would complete my car. I dont have a crank, but i am very interested in the one you have. I would want to lighten it too. The pistons are in your car right? If so could you tell me how they worked out? My brother had a small problem with his where they had to trim a thousandth of an inch off the top of it becuase it wasnt clearing. I would like to get J&E pistons, probably same specs as yours. It woudl also let me wind out higher after the new intake manifold.

Its good to find someone who is going the same way too, I felt very alone and no one to compare products and ideas with.
Good luck!

Dan
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Old 11-25-2002, 08:16 PM   #5
ColinL
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'01 Erion CBR 929

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why do pistons and rods if you're not doing cams and engine management?

no point in it.
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Old 11-25-2002, 11:30 PM   #6
Tattoo Collector
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Black Mica Pearl

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First and foremost, I have to rebuild the engine. My block is supposedly cracked and I had to swap blocks. I am not going to trust the stock components that are in the block that I got, so I might as well go with better stuff if I am going to do it at all. But, anyway, it will, most certainly make a difference. I am changing the compression from 9.7:1 to 11:1. That right there is going to produce a more powerful compression stroke, therefore giving me more power. I have built a few engines in my day and from everything that I have learned, I am thinking that this will, by all means create more horsepower. Unless subarus are different from every other motor that I've built. I am not saying that I am not going to do the cams in the future, but I can't afford to do it right now. I am going to port and polish the heads and do a valve job, but the only reason I am able to afford that is because I am doing the machining myself, in my performance engine balancing/blueprinting class. I am also putting on a full exhaust and intake. Plus, correct me if I am wrong, b/c I don't know as much as I should about ECU's (I used to build old hotrod motors), won't the subaru learn that there is a need for more fuel and realize more air is running through the engine? Won't this result in the MAF telling the ECU that it needs to run more fuel to the injectors? In all honesty, if the block didn't crack I would never be doing any of this stuff to this car. I would be buying another 911 and turning that into an all out N/A track beast!
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Old 11-26-2002, 03:00 AM   #7
Keiho
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Graphite Gray Pearl

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Well, I've got a bored throttle body, and I don't have dyno runs to show gains, but I can tell you that throttle response is improved greatly.
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Old 11-26-2002, 05:18 PM   #8
BOY
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99 RS-T RIP
02 Forster-S

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Our TBs will flow more than enough cfm for your engine build, porting/polishing/knive edging will improve throttle response but will only yield a hp or two. I can tell you from experience that it is a fun project, grinding metal always is but I need to go back and re-work mine a bit. I you're going to do it yourself go for it, if you're going to pay someone else spend the money elsewhere, its just not worth the shop bill.
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