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Discussion Starter · #1 ·
Hey guys,

I was wondering what kind of HP/TQ gains I should expect after installing my godpseed uppipe and downpipe. I am currently running my MBC at 16psi.

Thanks!
(yes i did a search)
 

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Discussion Starter · #2 ·
surely someone's got an opinion!? :D
 

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This is not a direct answer to your question, however this is a personal anedote of increased performance through exhaust modification on my WRX.

I installed the TurboXS stealth turboback system recently. This system consists of a catless downpipe, and a single high-flow cat mid-section and connecting pipe.

I did NOT change the stock uppipe (that's next on my list of mods!)

Without ANY other changes I gained 1.25mph in the 1/4 mile, and managed to drop 3/10ths of a second in ET.

Not bad for a mod that is basically stealth (no increased exhaust note as I'm running the stock muffler) and was <$600!

Aloha,
Richard...

P.S. Somebody smarter than I can do the calculations to see what kind of HP increase it would take to move my '02 WRX Sedan with me driving (~160lbs.) down the 1/4 mile 1.25mph faster... That would be interesting!
 

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someone posted this question at i-club a while ago, I used assumed fomula and some seemed to agree.
JDM WRX=250hp w/ one cat.
USDM WRX=227hp w / 3 cats.
250-227=24 in different of 2 cats therefor can say 12hp/cat.
so catless should run you around 262hp
this might not be accurate, but quite a few people agreed.
 

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Discussion Starter · #5 ·
thanks for the info guys, anyone else wanna add?
 

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You need to specify if you are going with the USDM version or JDM version of the down-pipe. The USDM version connects to the stock main cat and the JDM version is completely catless and can only connect to a JDM exhaust.
I'm running the Turbo XS stealth back (same as is2scooby) but I do not have the high flow cat, instead I have a straight pipe. Most people will tell you that running catless will lead to big gains and I will agree to that claim. How much hp, I really could not tell you.
 

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is2scooby said:
what kind of HP increase it would take to move my '02 WRX Sedan with me driving (~160lbs.) down the 1/4 mile 1.25mph faster... That would be interesting!
What's your original ET/Trap?
 

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I hate to give out my E.T. and MPH figures because they seem so slow - because of the poor track and heat/humidity issues we deal with here in Honolulu, HI - but here goes!

Original MPH = 90.01
After TurboXS MPH = 91.25

I haven't seen a stock WRX trap over 90.xx here yet. Darned tracks in Paradise! :D

Anybody want to venture a guess at how much horsepower it took to raise my MPH 1.24?

My WRX Sedan is stock, but with lightweight 17" Rota Attacks and I weight ~160lbs...
 

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All8up said:
You need to specify if you are going with the USDM version or JDM version of the down-pipe. The USDM version connects to the stock main cat and the JDM version is completely catless and can only connect to a JDM exhaust...
Wrong, both the USDM and JDM Godspeed downpipes will eliminate both the cats after the turbo. The only difference is the JDM will mate up to JDM spec catbacks, and USDM will mate up to USDM catbacks.
 

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gryphon said:
0.0021294863172505055611552852074378 * weight is the gained hp
I was serious BTW.

If your weight is the same both times, say 1/4 tank of gas ( ~ 22 lbs.) + you (160 lbs) + car (3085 lbs) then the hp difference is 3267 * the above number =~ 6.96 or about 7 awhp

That's also assuming everything remained the same. Which is a bunch of crap. Were your 60' times equal? Temperature? humidity? same track? same 1/8 mile? Nah. Doubt it. Doubt it a lot.
 

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I was serious BTW.

If your weight is the same both times, say 1/4 tank of gas ( ~ 22 lbs.) + you (160 lbs) + car (3085 lbs) then the hp difference is 3267 * the above number =~ 6.96 or about 7 awhp

That's also assuming everything remained the same. Which is a bunch of crap. Were your 60' times equal? Temperature? humidity? same track? same 1/8 mile? Nah. Doubt it. Doubt it a lot.
Gryphon,

Mahalo! Thanks for the formula. People with brains bigger than mine (like you) come up with this stuff, huh? :D I was thinking that I'd see more than a 7awhp gain - but who is going to complain for an exhaust that retains a catalytic converter and doesn't even replace the stock muffler? WAY stealth!

Aloha,
Richard...
 

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atf78 said:


Wrong, both the USDM and JDM Godspeed downpipes will eliminate both the cats after the turbo. The only difference is the JDM will mate up to JDM spec catbacks, and USDM will mate up to USDM catbacks.

I stand corrected. I remember when the USDM version was in development, that many people wanted it to retain the factory primary cat.
I guess a lot of people other than myself are catless...
 

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Just to give you an idea- a recent thread documented a dyno run w/ the following mods- decatted upipe, turboback w/ hi-flow cat in downpipe and Samco hoses. No boost controllers- no engine mgt.

His figure were 205 hp, 215 lbs torque- that's a ~ 40 hp gain over stock- mighty impressive says I.

Big Sky
 

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3085 is stock weight with full tank of gas



If your weight is the same both times, say 1/4 tank of gas ( ~ 22 lbs.) + you (160 lbs) + car (3085 lbs) then the hp difference is 3267 * the above number =~ 6.96 or about 7 awhp
 
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