imported_fattz

hi all

I have some question, i have a 93 civic and planning to get a b16a sir2 engine with turbo...is that a waste? should I get sir1 or sir2? the other question is about the exhaust, if I got a turbo can I use the NA catback? for example apexi WS, N1 coz the pipes are 2.25" and someone told me turbo should have 3" pipes...

thankyou so much for answering my question...THANKYOU!!!

chris_si98

anything above 220ishwhp I would recommend getting 3" pipes.. it can make a pretty big difference.

2 1/4" will definately hold you back a lot on a boosted motor.. even if you are pushing around 180-200whp.

imported_weiRtech

i can't speak for which engine you should get as i don't know them that well. from my understanding though obd1 is easier to tune.

chris is right, generally you want a larger exhaust on a turbo car as the exhaust will only flow as fast or slow as the turbo can expel it, so bigger is better. with n/a engines you want to have an efficient exhaust system to help keep velocity at maximum to evacuate exhaust gases.

imported_mikepasini

i am going to be running 7psi on a gsr in an ek eventually... i only have a 2.5" straight pipe... how much will this hold me back...

chris_si98

7psi on what setup?

it'll hold you back quite a bit if its about 220-250whp

imported_2join performance

2.25" is enough for mild boost. 2.5" will be good too, but 3" is overkill on anything below 250hp.

dingus888

save some $$ and get a b18b swap if your gonna boost it anyway

Bryce

mike your 2.5 should be fine man forsure... unless you pull like 300whp

89SIHATCH?

2.5 " is a perfect size. i was running a 2.5" straight pipe before on my old hatchback with a A6 in it, had headers and CAI to tag along with it.
it was a very fun car and pretty quick.

now 2.5" with boost added at around 7psi-12psi should be great too.

imported_weiRtech

i disagree. turbo engines are very sensitive to back pressure. a free flowing exhaust allows the turbo to spool faster. if you have too much back pressure it will decrease the efficiency of the turbo's ability to flow exhaust.

with an n/a engine you want good scaveging from your exhaust valves to help increase velocity in your exhaust system so having just the right size exhaust is important. a good exhaust for an n/a engine should have low back pressure and high velocity. NOT so for turbo engines or nitrous applications.

it is almost impossible to put too big a diameter exhaust on a turbo car as the turbo relies on pressure differential across the exhaust turbine to get power recovery efficiently... meaning, your whole exhaust system can only flow as effeciently as the turbo will push it out of the system... and if the pipe behind the turbo is too small it won't be able to push it out freely enough decreasing the potential of the turbo (too much back pressure as stated earlier).

here is a good rule of thumb for both n/a and turbo exhausts:

2" is good for up to about 130hp
2.25" is good for about 150hp
2.5" is good for about 170hp
3" is good for up to about 500hp
4" should be fine for anything approaching 1000hp

89SIHATCH?

go 4"

zeeman

iTrader: (1)

i'd go with a SIR II b/c it will go into your 93 civic a lot easier than the older obd0 SIR I engine/tranny will. If you use a SIR I you will need a hydro tranny, the SIR I uses a cable tranny. OBD1 is definately better for tuning, which is really important with a turbo car.
If you are going to spend the money on bigger exhaust i would go 3". You will always want to go faster, especially once you get a taste of boost. Trust me, a bigger turbo will be in your future and prolly a built engine to handle more boost. I've seen it plenty of times.....boost is hella addictive.

trinituner-EL

as Zeeman said, boost is very addictive. Go with the 3" especially if its a GSR. They make 275- 300 whp easy with a nice turbo

imported_mikepasini

i am running a b18c1 with a 2.5" striaight pipe wirh rsr gt2 muffler... i am putting on a 7psi turbo... and getting it tuned of course... i have it at home actually, just waiting for the funds to get it installed.

will this piping be enough?

1nf4m0u5

why take a chance

Mr. Death

It will do for now but you definatly will want to upgrade in the future. I was using a 2.25" exhaust on my turbo car @8 lbs for one year. ONe thing I did notice was quicker spool up time once I upgraded.

imported_mikepasini

its not big enough?

RDub99

iTrader: (1)

no, go with 3"

imported_mikepasini

wtf... 3" for 7psi? dammit... why did i buy the 2.5" then...

chris_si98

7psi on what turbo?