ok i just im in the process of rebuilding my car


KOYO radi
2 12'' Flex a lite fans
Topline 0.040 over pistons
OEM used rod's
New Head and can's From CCH
yada ...yada

ok now here's my question

now my engine is gonna be mostly new 100% new Topend, 75%bottom end
should i run a 2.5 exhaust or a 3 in exhaust????
my car has no exhaust or down pipe just the OEM header.....soon to be replaced

i have herd that 2.5 is better cuz of back pressure but also i hear that 3 give's better fuel econ and power

i just dont wanna redo my engine i want her to last so i can pass her down to my kid's

 

dont waste your time with 2.5 in, the whole backpressure thing, ehh, but you are going turbo soon anyway so you dont want to get a new exhaust, 3in is a good size

 

I currently have a 3" exhaust because i used to have an SR. Now that i have a N/A KA its killing me. So if you are planning on going turbo you might as well go 3" but if not 2.5" is your best bet.

 

go 3"
it really depends on what your setup is
if you're looking for around 200-250, go with 2.5"
of course, anything above 250, go with 3" or more.
thats just my recommendation

 

if youre already planning on turboing do 3"

if its gonna stay n/a, a 3" exhaust is gonna kill your top end and torque

 

someone explain to me this whole concept of needing back pressure.
Where the hell did that fucked up idea even come from?
Do any of you "needs back pressure" people remotely understand things like cam overlap? or scavenging? or exactly how you make power with a good exhaust set up?

 

enlighten us oh mighty one

 

On Nico there are a couple of n/a KA's using 3inch and they did not lose any hp or tq they have dyno sheets posted to back it up.

 

yup just another dyno from the other day
NA KA24DE motors love to breathe!... My stock motor dyno... PICS!... - FreshAlloy.com Forums

KA's love 3 inches. even for n/a.
now gt spec that starts at 3 and opens to 3.75"...maybe pushing it but still wont lose much.

 

Hmmm... interesting

Those are the numbers im shooting for with my S14 KA. Where did you get your car dyno at? Im wondering if we are close. The only thing i have different is a custom ram air intake, electric fans, and a koyo radiator. If i can get those same numbers i believe i can squeeze a bit more with some tricks i have under my sleeve.